This guide presents a catalog of security-relevant
configuration settings for Red Hat Enterprise Linux 7 formatted in the
eXtensible Configuration Checklist Description Format (XCCDF).
Applicable platforms
|
Version: 0.9 Revision history
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1. Introduction
The purpose of this guidance is to provide security configuration recommendations and baselines for the Red Hat Enterprise Linux (RHEL) 7 operating system. The guidance provided here should be applicable to all variants (Desktop, Server, Advanced Platform) of the product. Recommended settings for the basic operating system are provided, as well as for many network services that the system can provide to other systems. The guide is intended for system administrators. Readers are assumed to possess basic system administration skills for Unix-like systems, as well as some familiarity with Red Hat's documentation and administration conventions. Some instructions within this guide are complex. All directions should be followed completely and with understanding of their effects in order to avoid serious adverse effects on the system and its security.
Table of Contents
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1.1. General Principles
The following general principles motivate much of the advice in this guide and should also influence any configuration decisions that are not explicitly covered.
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1.1.1. Encrypt Transmitted Data Whenever Possible
Data transmitted over a network, whether wired or wireless, is susceptible to passive monitoring. Whenever practical solutions for encrypting such data exist, they should be applied. Even if data is expected to be transmitted only over a local network, it should still be encrypted. Encrypting authentication data, such as passwords, is particularly important. Networks of Red Hat Enterprise Linux 7 machines can and should be configured so that no unencrypted authentication data is ever transmitted between machines.
1.1.2. Minimize Software to Minimize Vulnerability
The simplest way to avoid vulnerabilities in software is to avoid installing that software. On RHEL, the RPM Package Manager (originally Red Hat Package Manager, abbreviated RPM) allows for careful management of the set of software packages installed on a system. Installed software contributes to system vulnerability in several ways. Packages that include setuid programs may provide local attackers a potential path to privilege escalation. Packages that include network services may give this opportunity to network-based attackers. Packages that include programs which are predictably executed by local users (e.g. after graphical login) may provide opportunities for trojan horses or other attack code to be run undetected. The number of software packages installed on a system can almost always be significantly pruned to include only the software for which there is an environmental or operational need.
1.1.3. Run Different Network Services on Separate Systems
Whenever possible, a server should be dedicated to serving exactly one network service. This limits the number of other services that can be compromised in the event that an attacker is able to successfully exploit a software flaw in one network service.
1.1.4. Configure Security Tools to Improve System Robustness
Several tools exist which can be effectively used to improve a system's resistance to and detection of unknown attacks. These tools can improve robustness against attack at the cost of relatively little configuration effort. In particular, this guide recommends and discusses the use of FirewallD for host-based firewalling, SELinux for protection against vulnerable services, and a logging and auditing infrastructure for detection of problems.
1.1.5. Least Privilege
Grant the least privilege necessary for user accounts and software to perform tasks.
For example, sudo
can be implemented to limit authorization to super user
accounts on the system only to designated personnel. Another example is to limit
logins on server systems to only those administrators who need to log into them in
order to perform administration tasks. Using SELinux also follows the principle of
least privilege: SELinux policy can confine software to perform only actions on the
system that are specifically allowed. This can be far more restrictive than the
actions permissible by the traditional Unix permissions model.
1.2. How to Use This Guide
Readers should heed the following points when using the guide.
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1.2.1. Read Sections Completely and in Order
Each section may build on information and recommendations discussed in prior sections. Each section should be read and understood completely; instructions should never be blindly applied. Relevant discussion may occur after instructions for an action.
1.2.2. Test in Non-Production Environment
This guidance should always be tested in a non-production environment before deployment. This test environment should simulate the setup in which the system will be deployed as closely as possible.
1.2.3. Root Shell Environment Assumed
Most of the actions listed in this document are written with the
assumption that they will be executed by the root user running the
/bin/bash
shell. Commands preceded with a hash mark (#)
assume that the administrator will execute the commands as root, i.e.
apply the command via sudo
whenever possible, or use
su
to gain root privileges if sudo
cannot be
used. Commands which can be executed as a non-root user are are preceded
by a dollar sign ($) prompt.
1.2.4. Formatting Conventions
Commands intended for shell execution, as well as configuration file text,
are featured in a monospace font
. Italics are used
to indicate instances where the system administrator must substitute
the appropriate information into a command or configuration file.
1.2.5. Reboot Required
A system reboot is implicitly required after some actions in order to complete the reconfiguration of the system. In many cases, the changes will not take effect until a reboot is performed. In order to ensure that changes are applied properly and to test functionality, always reboot the system after applying a set of recommendations from this guide.
2. System Settings
Table of Contents
- 2.1. Installing and Maintaining Software
-
2.2. File Permissions and Masks
-
2.2.1. Restrict Partition Mount Options
- 2.2.1.a. Add nodev Option to Non-Root Local Partitions
- 2.2.1.b. Add nodev Option to Removable Media Partitions
- 2.2.1.c. Add noexec Option to Removable Media Partitions
- 2.2.1.d. Add nosuid Option to Removable Media Partitions
- 2.2.1.e. Add nodev Option to /tmp
- 2.2.1.f. Add noexec Option to /tmp
- 2.2.1.g. Add nosuid Option to /tmp
- 2.2.1.h. Add nodev Option to /dev/shm
- 2.2.1.i. Add noexec Option to /dev/shm
- 2.2.1.j. Add nosuid Option to /dev/shm
- 2.2.1.k. Bind Mount /var/tmp To /tmp
-
2.2.2. Restrict Dynamic Mounting and Unmounting of Filesystems
- 2.2.2.a. Disable Modprobe Loading of USB Storage Driver
- 2.2.2.b. Disable Kernel Support for USB via Bootloader Configuration
- 2.2.2.c. Disable Booting from USB Devices in Boot Firmware
- 2.2.2.d. Assign Password to Prevent Changes to Boot Firmware Configuration
- 2.2.2.e. Disable the Automounter
- 2.2.2.f. Disable GNOME3 Automounting
- 2.2.2.g. Disable Mounting of cramfs
- 2.2.2.h. Disable Mounting of freevxfs
- 2.2.2.i. Disable Mounting of jffs2
- 2.2.2.j. Disable Mounting of hfs
- 2.2.2.k. Disable Mounting of hfsplus
- 2.2.2.l. Disable Mounting of squashfs
- 2.2.2.m. Disable Mounting of udf
- 2.2.2.n. Disable All GNOME3 Thumbnailers
-
2.2.3. Verify Permissions on Important Files and Directories
- 2.2.3.a. Verify that All World-Writable Directories Have Sticky Bits Set
- 2.2.3.b. Ensure No World-Writable Files Exist
- 2.2.3.e. Ensure All Files Are Owned by a User
- 2.2.3.f. Ensure All Files Are Owned by a Group
- 2.2.3.g. Ensure All World-Writable Directories Are Owned by a System Account
-
2.2.3.8. Verify Permissions on Files with Local Account Information and Credentials
- 2.2.3.8.a. Verify User Who Owns shadow File
- 2.2.3.8.b. Verify Group Who Owns shadow File
- 2.2.3.8.c. Verify Permissions on shadow File
- 2.2.3.8.d. Verify User Who Owns group File
- 2.2.3.8.e. Verify Group Who Owns group File
- 2.2.3.8.f. Verify Permissions on group File
- 2.2.3.8.g. Verify User Who Owns gshadow File
- 2.2.3.8.h. Verify Group Who Owns gshadow File
- 2.2.3.8.i. Verify Permissions on gshadow File
- 2.2.3.8.j. Verify User Who Owns passwd File
- 2.2.3.8.k. Verify Group Who Owns passwd File
- 2.2.3.8.l. Verify Permissions on passwd File
- 2.2.3.9. Verify File Permissions Within Some Important Directories
- 2.2.4. Restrict Programs from Dangerous Execution Patterns
-
2.2.1. Restrict Partition Mount Options
-
2.3. SELinux
- 2.3.a. Ensure SELinux Not Disabled in /etc/grub.conf
- 2.3.b. Ensure SELinux State is Enforcing
- 2.3.c. Configure SELinux Policy
- 2.3.d. Uninstall setroubleshoot Package
- 2.3.e. Uninstall mcstrans Package
- 2.3.f. Ensure No Daemons are Unconfined by SELinux
- 2.3.g. Ensure No Device Files are Unlabeled by SELinux
-
2.4. Account and Access Control
-
2.4.1. Protect Accounts by Restricting Password-Based Login
-
2.4.1.1. Restrict Root Logins
- 2.4.1.1.a. Direct root Logins Not Allowed
- 2.4.1.1.b. Restrict Virtual Console Root Logins
- 2.4.1.1.c. Restrict Serial Port Root Logins
- 2.4.1.1.d. Restrict Web Browser Use for Administrative Accounts
- 2.4.1.1.e. Ensure that System Accounts Do Not Run a Shell Upon Login
- 2.4.1.1.f. Verify Only Root Has UID 0
- 2.4.1.1.g. Root Path Must Be Vendor Default
- 2.4.1.2. Verify Proper Storage and Existence of Password Hashes
- 2.4.1.3. Set Password Expiration Parameters
- 2.4.1.4. Set Account Expiration Parameters
-
2.4.1.1. Restrict Root Logins
-
2.4.2. Protect Accounts by Configuring PAM
- 2.4.2.a. Set Last Logon/Access Notification
-
2.4.2.2. Set Password Quality Requirements
-
2.4.2.2.1. Set Password Quality Requirements with pam_pwquality
- 2.4.2.2.1.a. Set Password Retry Prompts Permitted Per-Session
- 2.4.2.2.1.b. Set Password to Maximum of Three Consecutive Repeating Characters
- 2.4.2.2.1.c. Set Password Strength Minimum Digit Characters
- 2.4.2.2.1.d. Set Password Minimum Length
- 2.4.2.2.1.e. Set Password Strength Minimum Uppercase Characters
- 2.4.2.2.1.f. Set Password Strength Minimum Special Characters
- 2.4.2.2.1.g. Set Password Strength Minimum Lowercase Characters
- 2.4.2.2.1.h. Set Password Strength Minimum Different Characters
- 2.4.2.2.1.i. Set Password Strength Minimum Different Categories
-
2.4.2.2.1. Set Password Quality Requirements with pam_pwquality
- 2.4.2.3. Set Lockouts for Failed Password Attempts
- 2.4.2.4. Set Password Hashing Algorithm
- 2.4.3. Secure Session Configuration Files for Login Accounts
-
2.4.4. Protect Physical Console Access
- 2.4.4.a. Require Authentication for Single User Mode
- 2.4.4.b. Disable Ctrl-Alt-Del Reboot Activation
- 2.4.4.c. Disable Interactive Boot
- 2.4.4.4. Set Boot Loader Password
- 2.4.4.5. Configure Screen Locking
-
2.4.1. Protect Accounts by Restricting Password-Based Login
-
2.5. Network Configuration and Firewalls
- 2.5.a. Disable Zeroconf Networking
- 2.5.b. Ensure System is Not Acting as a Network Sniffer
- 2.5.3. Disable Unused Interfaces
-
2.5.4. Kernel Parameters Which Affect Networking
- 2.5.4.1. Network Parameters for Hosts Only
-
2.5.4.2. Network Related Kernel Runtime Parameters for Hosts and Routers
- 2.5.4.2.a. Disable Kernel Parameter for Accepting Source-Routed Packets for All Interfaces
- 2.5.4.2.b. Disable Kernel Parameter for Accepting ICMP Redirects for All Interfaces
- 2.5.4.2.c. Disable Kernel Parameter for Accepting Secure Redirects for All Interfaces
- 2.5.4.2.d. Enable Kernel Parameter to Log Martian Packets
- 2.5.4.2.e. Disable Kernel Parameter for Accepting Source-Routed Packets By Default
- 2.5.4.2.f. Disable Kernel Parameter for Accepting ICMP Redirects By Default
- 2.5.4.2.g. Disable Kernel Parameter for Accepting Secure Redirects By Default
- 2.5.4.2.h. Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests
- 2.5.4.2.i. Enable Kernel Parameter to Ignore Bogus ICMP Error Responses
- 2.5.4.2.k. Enable Kernel Parameter to Use Reverse Path Filtering for All Interfaces
- 2.5.4.2.l. Enable Kernel Parameter to Use Reverse Path Filtering by Default
- 2.5.5. Wireless Networking
-
2.5.6. IPv6
- 2.5.6.1. Disable Support for IPv6 Unless Needed
- 2.5.6.2. Configure IPv6 Settings if Necessary
- 2.5.7. firewalld
- 2.5.8. Transport Layer Security Support
- 2.5.9. Uncommon Network Protocols
- 2.5.10. IPSec Support
-
2.6. Configure Syslog
- 2.6.a. Ensure rsyslog is Installed
- 2.6.b. Enable rsyslog Service
- 2.6.c. Disable Logwatch on Clients if a Logserver Exists
- 2.6.4. Ensure Proper Configuration of Log Files
- 2.6.5. Rsyslog Logs Sent To Remote Host
- 2.6.6. Configure rsyslogd to Accept Remote Messages If Acting as a Log Server
- 2.6.7. Ensure All Logs are Rotated by logrotate
- 2.6.8. Configure Logwatch on the Central Log Server
-
2.7. System Accounting with auditd
- 2.7.a. Enable auditd Service
- 2.7.b. Enable Auditing for Processes Which Start Prior to the Audit Daemon
-
2.7.3. Configure auditd Data Retention
- 2.7.3.a. Configure auditd Number of Logs Retained
- 2.7.3.b. Configure auditd Max Log File Size
- 2.7.3.c. Configure auditd max_log_file_action Upon Reaching Maximum Log Size
- 2.7.3.d. Configure auditd space_left Action on Low Disk Space
- 2.7.3.e. Configure auditd admin_space_left Action on Low Disk Space
- 2.7.3.f. Configure auditd mail_acct Action on Low Disk Space
- 2.7.3.g. Configure auditd flush priority
- 2.7.3.h. Configure auditd to use audispd's syslog plugin
-
2.7.4. Configure auditd Rules for Comprehensive Auditing
- 2.7.4.a. Record Events that Modify User/Group Information
- 2.7.4.b. Record Events that Modify the System's Network Environment
- 2.7.4.c. System Audit Logs Must Have Mode 0640 or Less Permissive
- 2.7.4.d. System Audit Logs Must Be Owned By Root
- 2.7.4.e. Record Events that Modify the System's Mandatory Access Controls
- 2.7.4.f. Record Attempts to Alter Logon and Logout Events
- 2.7.4.g. Record Attempts to Alter Process and Session Initiation Information
- 2.7.4.h. Ensure auditd Collects Unauthorized Access Attempts to Files (unsuccessful)
- 2.7.4.i. Ensure auditd Collects Information on the Use of Privileged Commands
- 2.7.4.j. Ensure auditd Collects Information on Exporting to Media (successful)
- 2.7.4.k. Ensure auditd Collects File Deletion Events by User
- 2.7.4.l. Ensure auditd Collects System Administrator Actions
- 2.7.4.m. Ensure auditd Collects Information on Kernel Module Loading and Unloading
- 2.7.4.n. Make the auditd Configuration Immutable
- 2.7.4.15. Records Events that Modify Date and Time Information
-
2.7.4.16. Record Events that Modify the System's Discretionary Access Controls
- 2.7.4.16.a. Record Events that Modify the System's Discretionary Access Controls - chmod
- 2.7.4.16.b. Record Events that Modify the System's Discretionary Access Controls - chown
- 2.7.4.16.c. Record Events that Modify the System's Discretionary Access Controls - fchmod
- 2.7.4.16.d. Record Events that Modify the System's Discretionary Access Controls - fchmodat
- 2.7.4.16.e. Record Events that Modify the System's Discretionary Access Controls - fchown
- 2.7.4.16.f. Record Events that Modify the System's Discretionary Access Controls - fchownat
- 2.7.4.16.g. Record Events that Modify the System's Discretionary Access Controls - fremovexattr
- 2.7.4.16.h. Record Events that Modify the System's Discretionary Access Controls - fsetxattr
- 2.7.4.16.i. Record Events that Modify the System's Discretionary Access Controls - lchown
- 2.7.4.16.j. Record Events that Modify the System's Discretionary Access Controls - lremovexattr
- 2.7.4.16.k. Record Events that Modify the System's Discretionary Access Controls - lsetxattr
- 2.7.4.16.l. Record Events that Modify the System's Discretionary Access Controls - removexattr
- 2.7.4.16.m. Record Events that Modify the System's Discretionary Access Controls - setxattr
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2.1. Installing and Maintaining Software
The following sections contain information on security-relevant choices during the initial operating system installation process and the setup of software updates.
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2.1.1. Disk Partitioning
To ensure separation and protection of data, there
are top-level system directories which should be placed on their
own physical partition or logical volume. The installer's default
partitioning scheme creates separate logical volumes for
/
, /boot
, and swap
.
-
If starting with any of the default layouts, check the box to "Review and modify partitioning." This allows for the easy creation of additional logical volumes inside the volume group already created, though it may require making
/
's logical volume smaller to create space. In general, using logical volumes is preferable to using partitions because they can be more easily adjusted later. -
If creating a custom layout, create the partitions mentioned in the previous paragraph (which the installer will require anyway), as well as separate ones described in the following sections.
If a system has already been installed, and the default partitioning scheme was used, it is possible but nontrivial to modify it to create separate logical volumes for the directories listed above. The Logical Volume Manager (LVM) makes this possible. See the LVM HOWTO at http://tldp.org/HOWTO/LVM-HOWTO/ for more detailed information on LVM.
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2.1.1.a. Ensure /tmp Located On Separate Partition
The /tmp
directory is a world-writable directory used
for temporary file storage. Ensure it has its own partition or
logical volume at installation time, or migrate it using LVM.
The /tmp
partition is used as temporary storage by many programs.
Placing /tmp
in its own partition enables the setting of more
restrictive mount options, which can help protect programs which use it.
Security identifiers
- CCE-27173-4
References
- SC-32. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20120928 by MM. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.1.b. Ensure /var Located On Separate Partition
The /var
directory is used by daemons and other system
services to store frequently-changing data. Ensure that /var
has its own partition
or logical volume at installation time, or migrate it using LVM.
Ensuring that /var
is mounted on its own partition enables the
setting of more restrictive mount options. This helps protect
system services such as daemons or other programs which use it.
It is not uncommon for the /var
directory to contain
world-writable directories installed by other software packages.
Security identifiers
- CCE-26404-4
References
- SC-32. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20120928 by MM. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.1.c. Ensure /var/log Located On Separate Partition
System logs are stored in the /var/log
directory.
Ensure that it has its own partition or logical
volume at installation time, or migrate it using LVM.
Placing /var/log
in its own partition
enables better separation between log files
and other files in /var/
.
Security identifiers
- CCE-26967-0
References
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-32. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20120928 by MM. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.1.d. Ensure /var/log/audit Located On Separate Partition
Audit logs are stored in the /var/log/audit
directory. Ensure that it
has its own partition or logical volume at installation time, or migrate it
later using LVM. Make absolutely certain that it is large enough to store all
audit logs that will be created by the auditing daemon.
Placing /var/log/audit
in its own partition
enables better separation between audit files
and other files, and helps ensure that
auditing cannot be halted due to the partition running out
of space.
Security identifiers
- CCE-26971-2
References
- AU-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-32. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20120928 by MM. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.1.e. Ensure /home Located On Separate Partition
If user home directories will be stored locally, create a separate partition
for /home
at installation time (or migrate it later using LVM). If
/home
will be mounted from another system such as an NFS server, then
creating a separate partition is not necessary at installation time, and the
mountpoint can instead be configured later.
Ensuring that /home
is mounted on its own partition enables the
setting of more restrictive mount options, and also helps ensure that
users cannot trivially fill partitions used for log or audit data storage.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SC-32. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1208. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20120928 by MM. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.1.f. Encrypt Partitions
Red Hat Enterprise Linux 7 natively supports partition encryption through the
Linux Unified Key Setup-on-disk-format (LUKS) technology. The easiest way to
encrypt a partition is during installation time.
For manual installations, select the Encrypt
checkbox during
partition creation to encrypt the partition. When this
option is selected the system will prompt for a passphrase to use in
decrypting the partition. The passphrase will subsequently need to be entered manually
every time the system boots.
For automated/unattended installations, it is possible to use Kickstart by adding
the --encrypted
and --passphrase=
options to the definition of each partition to be
encrypted. For example, the following line would encrypt the root partition:
part / --fstype=ext4 --size=100 --onpart=hda1 --encrypted --passphrase=PASSPHRASE
Any PASSPHRASE is stored in the Kickstart in plaintext, and the Kickstart must then be protected accordingly.
Omitting the --passphrase=
option from the partition definition will cause the
installer to pause and interactively ask for the passphrase during installation.
Detailed information on encrypting partitions using LUKS can be found on the Red Hat Documentation web site:
https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/7/html/Security_Guide/sec-Encryption.html
The risk of a system's physical compromise, particularly mobile systems such as laptops, places its data at risk of compromise. Encrypting this data mitigates the risk of its loss if the system is lost.
Security identifiers
- CCE-27128-8
References
- SC-13. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-28. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1019. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1199. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1200. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 185. .
2.1.2. Updating Software
The yum
command line tool is used to install and
update software packages. The system also provides a graphical
software update tool in the System menu, in the Administration submenu,
called Software Update.
Red Hat Enterprise Linux systems contain an installed software catalog called
the RPM database, which records metadata of installed packages. Consistently using
yum
or the graphical Software Update for all software installation
allows for insight into the current inventory of installed software on the system.
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2.1.2.a. Ensure Red Hat GPG Key Installed
To ensure the system can cryptographically verify base software packages come from Red Hat (and to connect to the Red Hat Network to receive them), the Red Hat GPG key must properly be installed. To install the Red Hat GPG key, run:
$ sudo rhn_register
If the system is not connected to the Internet or an RHN Satellite,
then install the Red Hat GPG key from trusted media such as
the Red Hat installation CD-ROM or DVD. Assuming the disc is mounted
in /media/cdrom
, use the following command as the root user to import
it into the keyring:
$ sudo rpm --import /media/cdrom/RPM-GPG-KEY
Changes to software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor. The Red Hat GPG key is necessary to cryptographically verify packages are from Red Hat.
Remediation script
# The two fingerprints below are retrieved from https://access.redhat.com/security/team/key
readonly REDHAT_RELEASE_2_FINGERPRINT="567E 347A D004 4ADE 55BA 8A5F 199E 2F91 FD43 1D51"
readonly REDHAT_AUXILIARY_FINGERPRINT="43A6 E49C 4A38 F4BE 9ABF 2A53 4568 9C88 2FA6 58E0"
# Location of the key we would like to import (once it's integrity verified)
readonly REDHAT_RELEASE_KEY="/etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release"
RPM_GPG_DIR_PERMS=$(stat -c %a "$(dirname "$REDHAT_RELEASE_KEY")")
# Verify /etc/pki/rpm-gpg directory permissions are safe
if [ "${RPM_GPG_DIR_PERMS}" -le "755" ]
then
# If they are safe, try to obtain fingerprints from the key file
# (to ensure there won't be e.g. CRC error)
IFS=$'\n' GPG_OUT=($(gpg --with-fingerprint "${REDHAT_RELEASE_KEY}"))
GPG_RESULT=$?
# No CRC error, safe to proceed
if [ "${GPG_RESULT}" -eq "0" ]
then
for ITEM in "${GPG_OUT[@]}"
do
# Filter just hexadecimal fingerprints from gpg's output from
# processing of a key file
RESULT=$(echo ${ITEM} | sed -n "s/[[:space:]]*Key fingerprint = \(.*\)/\1/p" | tr -s '[:space:]')
# If fingerprint matches Red Hat's release 2 or auxiliary key import the key
if [[ ${RESULT} ]] && ([[ ${RESULT} = "${REDHAT_RELEASE_2_FINGERPRINT}" ]] || \
[[ ${RESULT} = "${REDHAT_AUXILIARY_FINGERPRINT}" ]])
then
rpm --import "${REDHAT_RELEASE_KEY}"
fi
done
fi
fi
Security identifiers
- CCE-26957-1
References
- CM-5(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MA-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1749. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 366. .
- Test attestation on 20150407 by sdw. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.2.b. Ensure gpgcheck Enabled In Main Yum Configuration
The gpgcheck
option controls whether
RPM packages' signatures are always checked prior to installation.
To configure yum to check package signatures before installing
them, ensure the following line appears in /etc/yum.conf
in
the [main]
section:
gpgcheck=1
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA).
Security identifiers
- CCE-26989-4
References
- CM-5(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MA-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1749. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 366. .
- Test attestation on 20150407 by sdw. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.2.c. Ensure gpgcheck Enabled For All Yum Package Repositories
To ensure signature checking is not disabled for
any repos, remove any lines from files in /etc/yum.repos.d
of the form:
gpgcheck=0
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA).
Security identifiers
- CCE-26876-3
References
- CM-5(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MA-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1749. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 366. .
- Test attestation on 20150407 by sdw. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.2.d. Ensure Software Patches Installed
If the system is joined to the Red Hat Network, a Red Hat Satellite Server, or a yum server, run the following command to install updates:
$ sudo yum update
If the system is not configured to use one of these sources, updates (in the form of RPM packages)
can be manually downloaded from the Red Hat Network and installed using rpm
.
Installing software updates is a fundamental mitigation against the exploitation of publicly-known vulnerabilities.
Security identifiers
- CCE-26853-2
References
- SI-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MA-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20120928 by MM. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.3. Software Integrity Checking
Both the AIDE (Advanced Intrusion Detection Environment)
software and the RPM package management system provide
mechanisms for verifying the integrity of installed software.
AIDE uses snapshots of file metadata (such as hashes) and compares these
to current system files in order to detect changes.
The RPM package management system can conduct integrity
checks by comparing information in its metadata database with
files installed on the system.
Integrity checking cannot prevent intrusions,
but can detect that they have occurred. Requirements
for software integrity checking may be highly dependent on
the environment in which the system will be used. Snapshot-based
approaches such as AIDE may induce considerable overhead
in the presence of frequent software updates.
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2.1.3.1. Verify Integrity with AIDE
AIDE conducts integrity checks by comparing information about
files with previously-gathered information. Ideally, the AIDE database is
created immediately after initial system configuration, and then again after any
software update. AIDE is highly configurable, with further configuration
information located in /usr/share/doc/aide-VERSION
.
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2.1.3.1.a. Install AIDE
Install the AIDE package with the command:
$ sudo yum install aide
The AIDE package must be installed if it is to be available for integrity checking.
Remediation script
yum -y install aide
Security identifiers
- CCE-26741-9
References
- CM-3(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-3(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-28. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.1.3.1.b. Disable Prelinking
The prelinking feature changes binaries in an attempt to decrease their startup
time. In order to disable it, change or add the following line inside the file
/etc/sysconfig/prelink
:
PRELINKING=no
Next, run the following command to return binaries to a normal, non-prelinked state:
$ sudo /usr/sbin/prelink -ua
The prelinking feature can interfere with the operation of AIDE, because it changes binaries.
Remediation script
#
# Disable prelinking altogether
#
if grep -q ^PRELINKING /etc/sysconfig/prelink
then
sed -i 's/PRELINKING.*/PRELINKING=no/g' /etc/sysconfig/prelink
else
echo -e "\n# Set PRELINKING=no per security requirements" >> /etc/sysconfig/prelink
echo "PRELINKING=no" >> /etc/sysconfig/prelink
fi
#
# Undo previous prelink changes to binaries
#
/usr/sbin/prelink -ua
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-6(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-28. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.1.3.1.c. Build and Test AIDE Database
Run the following command to generate a new database:
$ sudo /usr/sbin/aide --init
By default, the database will be written to the file /var/lib/aide/aide.db.new.gz
.
Storing the database, the configuration file /etc/aide.conf
, and the binary
/usr/sbin/aide
(or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity.
The newly-generated database can be installed as follows:
$ sudo cp /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
To initiate a manual check, run the following command:
$ sudo /usr/sbin/aide --check
If this check produces any unexpected output, investigate.
For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-3(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-3(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-28. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.1.3.1.d. Configure Periodic Execution of AIDE
To implement a daily execution of AIDE at 4:05am using cron, add the following line to /etc/crontab
:
05 4 * * * root /usr/sbin/aide --check
AIDE can be executed periodically through other means; this is merely one example.
By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.
Remediation script
echo "05 4 * * * root /usr/sbin/aide --check" >> /etc/crontab
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-3(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-3(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-28. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 374. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 416. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1069. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1263. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1297. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1589. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.1.3.2. Verify Integrity with RPM
The RPM package management system includes the ability to verify the integrity of installed packages by comparing the installed files with information about the files taken from the package metadata stored in the RPM database. Although an attacker could corrupt the RPM database (analogous to attacking the AIDE database as described above), this check can still reveal modification of important files. To list which files on the system differ from what is expected by the RPM database:
$ rpm -qVa
See the man page for rpm
to see a complete explanation of each column.
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2.1.3.2.a. Verify and Correct File Permissions with RPM
The RPM package management system can check file access permissions of installed software packages, including many that are important to system security. After locating a file with incorrect permissions, run the following command to determine which package owns it:
$ rpm -qf FILENAME
Next, run the following command to reset its permissions to
the correct values:
$ sudo rpm --setperms PACKAGENAME
Permissions on system binaries and configuration files that are too generous could allow an unauthorized user to gain privileges that they should not have. The permissions set by the vendor should be maintained. Any deviations from this baseline should be investigated.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1493. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1494. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1495. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.1.3.2.b. Verify File Hashes with RPM
The RPM package management system can check the hashes of installed software packages, including many that are important to system security. Run the following command to list which files on the system have hashes that differ from what is expected by the RPM database:
$ rpm -Va | grep '^..5'
A "c" in the second column indicates that a file is a configuration file, which
may appropriately be expected to change. If the file was not expected to
change, investigate the cause of the change using audit logs or other means.
The package can then be reinstalled to restore the file.
Run the following command to determine which package owns the file:
$ rpm -qf FILENAME
The package can be reinstalled from a yum repository using the command:
$ sudo yum reinstall PACKAGENAME
Alternatively, the package can be reinstalled from trusted media using the command:
$ sudo rpm -Uvh PACKAGENAME
The hashes of important files like system executables should match the information given by the RPM database. Executables with erroneous hashes could be a sign of nefarious activity on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-6(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-6(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1496. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.1.3.3. Additional Security Software
Additional security software that is not provided or supported by Red Hat can be installed to provide complementary or duplicative security capabilities to those provided by the base platform. Add-on software may not be appropriate for some specialized systems.
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2.1.3.3.a. Install Intrusion Detection Software
The base Red Hat platform already includes a sophisticated auditing system that
can detect intruder activity, as well as SELinux, which provides host-based
intrusion prevention capabilities by confining privileged programs and user
sessions which may become compromised.
In DoD environments, supplemental intrusion detection tools, such as, the McAfee
Host-based Security System, are available to integrate with existing infrastructure.
When these supplemental tools interfere with the proper functioning of SELinux, SELinux
takes precedence.
Host-based intrusion detection tools provide a system-level defense when an intruder gains access to a system or network.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.1.3.3.b. Install Virus Scanning Software
Install virus scanning software, which uses signatures to search for the presence of viruses on the filesystem. The McAfee VirusScan Enterprise for Linux virus scanning tool is provided for DoD systems. Ensure virus definition files are no older than 7 days, or their last release. Configure the virus scanning software to perform scans dynamically on all accessed files. If this is not possible, configure the system to scan all altered files on the system on a daily basis. If the system processes inbound SMTP mail, configure the virus scanner to scan all received mail.
Virus scanning software can be used to detect if a system has been compromised by computer viruses, as well as to limit their spread to other systems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SC-28. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1239. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1668. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2. File Permissions and Masks
Traditional Unix security relies heavily on file and
directory permissions to prevent unauthorized users from reading or
modifying files to which they should not have access.
Several of the commands in this section search filesystems
for files or directories with certain characteristics, and are
intended to be run on every local partition on a given system.
When the variable PART appears in one of the commands below,
it means that the command is intended to be run repeatedly, with the
name of each local partition substituted for PART in turn.
The following command prints a list of all xfs partitions on the local
system, which is the default filesystem for Red Hat Enterprise Linux
7 installations:
$ mount -t xfs | awk '{print $3}'
For any systems that use a different
local filesystem type, modify this command as appropriate.
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2.2.1. Restrict Partition Mount Options
System partitions can be mounted with certain options
that limit what files on those partitions can do. These options
are set in the /etc/fstab
configuration file, and can be
used to make certain types of malicious behavior more difficult.
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2.2.1.a. Add nodev Option to Non-Root Local Partitions
The nodev
mount option prevents files from being
interpreted as character or block devices.
Legitimate character and block devices should exist only in
the /dev
directory on the root partition or within chroot
jails built for system services.
Add the nodev
option to the fourth column of
/etc/fstab
for the line which controls mounting of
any non-root local partitions.
The nodev
mount option prevents files from being
interpreted as character or block devices. The only legitimate location
for device files is the /dev
directory located on the root partition.
The only exception to this is chroot jails, for which it is not advised
to set nodev
on these filesystems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.b. Add nodev Option to Removable Media Partitions
The nodev
mount option prevents files from being
interpreted as character or block devices.
Legitimate character and block devices should exist only in
the /dev
directory on the root partition or within chroot
jails built for system services.
Add the nodev
option to the fourth column of
/etc/fstab
for the line which controls mounting of
any removable media partitions.
The only legitimate location for device files is the /dev
directory
located on the root partition. An exception to this is chroot jails, and it is
not advised to set nodev
on partitions which contain their root
filesystems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MP-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.2.1.c. Add noexec Option to Removable Media Partitions
The noexec
mount option prevents the direct
execution of binaries on the mounted filesystem.
Preventing the direct execution of binaries from removable media (such as a USB
key) provides a defense against malicious software that may be present on such
untrusted media.
Add the noexec
option to the fourth column of
/etc/fstab
for the line which controls mounting of
any removable media partitions.
Allowing users to execute binaries from removable media such as USB keys exposes the system to potential compromise.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MP-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 87. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2.1.d. Add nosuid Option to Removable Media Partitions
The nosuid
mount option prevents set-user-identifier (SUID)
and set-group-identifier (SGID) permissions from taking effect. These permissions
allow users to execute binaries with the same permissions as the owner and group
of the file respectively. Users should not be allowed to introduce SUID and SGID
files into the system via partitions mounted from removeable media.
Add the nosuid
option to the fourth column of
/etc/fstab
for the line which controls mounting of
any removable media partitions.
The presence of SUID and SGID executables should be tightly controlled. Allowing users to introduce SUID or SGID binaries from partitions mounted off of removable media would allow them to introduce their own highly-privileged programs.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MP-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.2.1.e. Add nodev Option to /tmp
The nodev
mount option can be used to prevent device files from
being created in /tmp
.
Legitimate character and block devices should not exist
within temporary directories like /tmp
.
Add the nodev
option to the fourth column of
/etc/fstab
for the line which controls mounting of
/tmp
.
The only legitimate location for device files is the /dev
directory
located on the root partition. The only exception to this is chroot jails.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.f. Add noexec Option to /tmp
The noexec
mount option can be used to prevent binaries
from being executed out of /tmp
.
Add the noexec
option to the fourth column of
/etc/fstab
for the line which controls mounting of
/tmp
.
Allowing users to execute binaries from world-writable directories
such as /tmp
should never be necessary in normal operation and
can expose the system to potential compromise.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.g. Add nosuid Option to /tmp
The nosuid
mount option can be used to prevent
execution of setuid programs in /tmp
. The SUID and SGID permissions
should not be required in these world-writable directories.
Add the nosuid
option to the fourth column of
/etc/fstab
for the line which controls mounting of
/tmp
.
The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.h. Add nodev Option to /dev/shm
The nodev
mount option can be used to prevent creation
of device files in /dev/shm
.
Legitimate character and block devices should not exist
within temporary directories like /dev/shm
.
Add the nodev
option to the fourth column of
/etc/fstab
for the line which controls mounting of
/dev/shm
.
The only legitimate location for device files is the /dev
directory
located on the root partition. The only exception to this is chroot jails.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.i. Add noexec Option to /dev/shm
The noexec
mount option can be used to prevent binaries
from being executed out of /dev/shm
.
It can be dangerous to allow the execution of binaries
from world-writable temporary storage directories such as /dev/shm
.
Add the noexec
option to the fourth column of
/etc/fstab
for the line which controls mounting of
/dev/shm
.
Allowing users to execute binaries from world-writable directories
such as /dev/shm
can expose the system to potential compromise.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.j. Add nosuid Option to /dev/shm
The nosuid
mount option can be used to prevent execution
of setuid programs in /dev/shm
. The SUID and SGID permissions should not
be required in these world-writable directories.
Add the nosuid
option to the fourth column of
/etc/fstab
for the line which controls mounting of
/dev/shm
.
The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.1.k. Bind Mount /var/tmp To /tmp
The /var/tmp
directory is a world-writable directory.
Bind-mount it to /tmp
in order to consolidate temporary storage into
one location protected by the same techniques as /tmp
. To do so, edit
/etc/fstab
and add the following line:
/tmp /var/tmp none rw,nodev,noexec,nosuid,bind 0 0
See the mount(8)
man page for further explanation of bind mounting.
Having multiple locations for temporary storage is not required. Unless absolutely
necessary to meet requirements, the storage location /var/tmp
should be bind mounted to
/tmp
and thus share the same protections.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2. Restrict Dynamic Mounting and Unmounting of Filesystems
Linux includes a number of facilities for the automated addition
and removal of filesystems on a running system. These facilities may be
necessary in many environments, but this capability also carries some risk -- whether direct
risk from allowing users to introduce arbitrary filesystems,
or risk that software flaws in the automated mount facility itself could
allow an attacker to compromise the system.
This command can be used to list the types of filesystems that are
available to the currently executing kernel:
$ find /lib/modules/`uname -r`/kernel/fs -type f -name '*.ko'
If these filesystems are not required then they can be explicitly disabled
in a configuratio file in /etc/modprobe.d
.
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2.2.2.a. Disable Modprobe Loading of USB Storage Driver
To prevent USB storage devices from being used, configure the kernel module loading system
to prevent automatic loading of the USB storage driver.
To configure the system to prevent the usb-storage
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install usb-storage /bin/true
This will prevent the modprobe
program from loading the usb-storage
module, but will not prevent an administrator (or another program) from using the
insmod
program to load the module manually.
USB storage devices such as thumb drives can be used to introduce malicious software.
Remediation script
echo "install usb-storage /bin/true" > /etc/modprobe.d/usb-storage.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1250. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2.2.b. Disable Kernel Support for USB via Bootloader Configuration
All USB support can be disabled by adding the nousb
argument to the kernel's boot loader configuration. To do so,
append "nousb" to the kernel line in /etc/grub.conf
as shown:
kernel /vmlinuz-VERSION ro vga=ext root=/dev/VolGroup00/LogVol00 rhgb quiet nousb
WARNING: Disabling all kernel support for USB will cause problems for
systems with USB-based keyboards, mice, or printers. This configuration is
infeasible for systems which require USB devices, which is common.
Disabling the USB subsystem within the Linux kernel at system boot will protect against potentially malicious USB devices, although it is only practical in specialized systems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1250. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2.2.c. Disable Booting from USB Devices in Boot Firmware
Configure the system boot firmware (historically called BIOS on PC systems) to disallow booting from USB drives.
Booting a system from a USB device would allow an attacker to circumvent any security measures provided by the operating system. Attackers could mount partitions and modify the configuration of the OS.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1250. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2.2.d. Assign Password to Prevent Changes to Boot Firmware Configuration
Assign a password to the system boot firmware (historically called BIOS on PC systems) to require a password for any configuration changes.
Assigning a password to the system boot firmware prevents anyone with physical access from configuring the system to boot from local media and circumvent the operating system's access controls. For systems in physically secure locations, such as a data center or Sensitive Compartmented Information Facility (SCIF), this risk must be weighed against the risk of administrative personnel being unable to conduct recovery operations in a timely fashion.
Security identifiers
- CCE-RHEL7-CCE-TBD
2.2.2.e. Disable the Automounter
The autofs
daemon mounts and unmounts filesystems, such as user
home directories shared via NFS, on demand. In addition, autofs can be used to handle
removable media, and the default configuration provides the cdrom device as /misc/cd
.
However, this method of providing access to removable media is not common, so autofs
can almost always be disabled if NFS is not in use. Even if NFS is required, it may be
possible to configure filesystem mounts statically by editing /etc/fstab
rather than relying on the automounter.
The autofs
service can be disabled with the following command:
$ sudo systemctl disable autofs
Disabling the automounter permits the administrator to
statically control filesystem mounting through /etc/fstab
.
Remediation script
#
# Disable autofs.service for all systemd targets
#
systemctl disable autofs.service
#
# Stop autofs.service if currently running
#
systemctl stop autofs.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1250. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2.2.f. Disable GNOME3 Automounting
The system's default desktop environment, GNOME3, will mount
devices and removable media (such as DVDs, CDs and USB flash drives) whenever
they are inserted into the system. To disable automount and autorun within GNOME3,
the automount
, automount-open
, and autorun-never
settings must be set
under an appropriate configuration file(s) in the /etc/dconf/db/local.d
directory
and locked in /etc/dconf/db/local.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
Disabling automatic mounting in GNOME3 can prevent the introduction of malware via removable media. It will, however, also prevent desktop users from legitimate use of removable media.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-19(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-19(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.2.2.g. Disable Mounting of cramfs
To configure the system to prevent the cramfs
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install cramfs /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install cramfs /bin/true" > /etc/modprobe.d/cramfs.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.h. Disable Mounting of freevxfs
To configure the system to prevent the freevxfs
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install freevxfs /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install freevxfs /bin/true" > /etc/modprobe.d/freevxfs.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.i. Disable Mounting of jffs2
To configure the system to prevent the jffs2
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install jffs2 /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install jffs2 /bin/true" > /etc/modprobe.d/jffs2.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.j. Disable Mounting of hfs
To configure the system to prevent the hfs
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install hfs /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install hfs /bin/true" > /etc/modprobe.d/hfs.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.k. Disable Mounting of hfsplus
To configure the system to prevent the hfsplus
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install hfsplus /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install hfsplus /bin/true" > /etc/modprobe.d/hfsplus.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.l. Disable Mounting of squashfs
To configure the system to prevent the squashfs
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install squashfs /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install squashfs /bin/true" > /etc/modprobe.d/squashfs.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.m. Disable Mounting of udf
To configure the system to prevent the udf
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install udf /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Remediation script
echo "install udf /bin/true" > /etc/modprobe.d/udf.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.2.n. Disable All GNOME3 Thumbnailers
The system's default desktop environment, GNOME3, uses
a number of different thumbnailer programs to generate thumbnails
for any new or modified content in an opened folder. To disable the
execution of these thumbnail applications, the disable-all
setting must be set
under an appropriate configuration file(s) in the /etc/dconf/db/local.d
directory
and locked in /etc/dconf/db/local.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
This effectively prevents an attacker from gaining access to a
system through a flaw in GNOME3's Nautilus thumbnail creators.
An attacker with knowledge of a flaw in a GNOME3 thumbnailer application could craft a malicious file to exploit this flaw. Assuming the attacker could place the malicious file on the local filesystem (via a web upload for example) and assuming a user browses the same location using Nautilus, the malicious file would exploit the thumbnailer with the potential for malicious code execution. It is best to disable these thumbnailer applications unless they are explicitly required.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.3. Verify Permissions on Important Files and Directories
Permissions for many files on a system must be set restrictively to ensure sensitive information is properly protected. This section discusses important permission restrictions which can be verified to ensure that no harmful discrepancies have arisen.
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2.2.3.a. Verify that All World-Writable Directories Have Sticky Bits Set
When the so-called 'sticky bit' is set on a directory,
only the owner of a given file may remove that file from the
directory. Without the sticky bit, any user with write access to a
directory may remove any file in the directory. Setting the sticky
bit prevents users from removing each other's files. In cases where
there is no reason for a directory to be world-writable, a better
solution is to remove that permission rather than to set the sticky
bit. However, if a directory is used by a particular application,
consult that application's documentation instead of blindly
changing modes.
To set the sticky bit on a world-writable directory DIR, run the
following command:
$ sudo chmod +t DIR
Failing to set the sticky bit on public directories allows unauthorized users to delete files in the directory structure.
The only authorized public directories are those temporary directories supplied with the system,
or those designed to be temporary file repositories. The setting is normally reserved for directories
used by the system, by users for temporary file storage (such as /tmp
), and for directories
requiring global read/write access.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20120929 by swells. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.b. Ensure No World-Writable Files Exist
It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor for recurring world-writable files, as these may be symptoms of a misconfigured application or user account.
Data in world-writable files can be modified by any user on the system. In almost all circumstances, files can be configured using a combination of user and group permissions to support whatever legitimate access is needed without the risk caused by world-writable files.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.3.c. Ensure All SGID Executables Are Authorized
The SGID (set group id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SGID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SGID files.
Executable files with the SGID permission run with the privileges of the owner of the file. SGID files of uncertain provenance could allow for unprivileged users to elevate privileges. The presence of these files should be strictly controlled on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
2.2.3.d. Ensure All SUID Executables Are Authorized
The SUID (set user id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SGID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SUID files.
Executable files with the SUID permission run with the privileges of the owner of the file. SUID files of uncertain provenance could allow for unprivileged users to elevate privileges. The presence of these files should be strictly controlled on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
2.2.3.e. Ensure All Files Are Owned by a User
If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user.
Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.3.f. Ensure All Files Are Owned by a Group
If any files are not owned by a group, then the cause of their lack of group-ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate group.
Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.3.g. Ensure All World-Writable Directories Are Owned by a System Account
All directories in local partitions which are world-writable should be owned by root or another system account. If any world-writable directories are not owned by a system account, this should be investigated. Following this, the files should be deleted or assigned to an appropriate group.
Allowing a user account to own a world-writable directory is undesirable because it allows the owner of that directory to remove or replace any files that may be placed in the directory by other users.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20120929 by swells. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8. Verify Permissions on Files with Local Account Information and Credentials
The default restrictive permissions for files which act as
important security databases such as passwd
, shadow
,
group
, and gshadow
files must be maintained. Many utilities
need read access to the passwd
file in order to function properly, but
read access to the shadow
file allows malicious attacks against system
passwords, and should never be enabled.
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2.2.3.8.a. Verify User Who Owns shadow File
To properly set the owner of /etc/shadow
, run the command:
$ sudo chown root /etc/shadow
The /etc/shadow
file contains the list of local
system accounts and stores password hashes. Protection of this file is
critical for system security. Failure to give ownership of this file
to root provides the designated owner with access to sensitive information
which could weaken the system security posture.
Remediation script
chown root /etc/shadow
Security identifiers
- CCE-26795-5
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.b. Verify Group Who Owns shadow File
To properly set the group owner of /etc/shadow
, run the command:
$ sudo chgrp root xsl:value-of select="@file"/>
The /etc/shadow
file stores password hashes. Protection of this file is
critical for system security.
Remediation script
chgrp root /etc/shadow
Security identifiers
- CCE-27125-4
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.c. Verify Permissions on shadow File
To properly set the permissions of /etc/shadow
, run the command:
$ sudo chmod 0000 /etc/shadow
The /etc/shadow
file contains the list of local
system accounts and stores password hashes. Protection of this file is
critical for system security. Failure to give ownership of this file
to root provides the designated owner with access to sensitive information
which could weaken the system security posture.
Remediation script
chmod 0000 /etc/shadow
Security identifiers
- CCE-27100-7
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.d. Verify User Who Owns group File
To properly set the owner of /etc/group
, run the command:
$ sudo chown root /etc/group
The /etc/group
file contains information regarding groups that are configured
on the system. Protection of this file is important for system security.
Remediation script
chown root /etc/group
Security identifiers
- CCE-26933-2
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.e. Verify Group Who Owns group File
To properly set the group owner of /etc/group
, run the command:
$ sudo chgrp root xsl:value-of select="@file"/>
The /etc/group
file contains information regarding groups that are configured
on the system. Protection of this file is important for system security.
Remediation script
chgrp root /etc/group
Security identifiers
- CCE-27037-1
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.f. Verify Permissions on group File
To properly set the permissions of /etc/group
, run the command:
$ sudo chmod 644 /etc/group
The /etc/group
file contains information regarding groups that are configured
on the system. Protection of this file is important for system security.
Remediation script
chmod 644 /etc/group
Security identifiers
- CCE-26949-8
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.g. Verify User Who Owns gshadow File
To properly set the owner of /etc/gshadow
, run the command:
$ sudo chown root /etc/gshadow
The /etc/gshadow
file contains group password hashes. Protection of this file
is critical for system security.
Remediation script
chown root /etc/gshadow
Security identifiers
- CCE-27161-9
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.h. Verify Group Who Owns gshadow File
To properly set the group owner of /etc/gshadow
, run the command:
$ sudo chgrp root xsl:value-of select="@file"/>
The /etc/gshadow
file contains group password hashes. Protection of this file
is critical for system security.
Remediation script
chgrp root /etc/gshadow
Security identifiers
- CCE-26840-9
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.i. Verify Permissions on gshadow File
To properly set the permissions of /etc/gshadow
, run the command:
$ sudo chmod 0000 /etc/gshadow
The /etc/gshadow
file contains group password hashes. Protection of this file
is critical for system security.
Remediation script
chmod 0000 /etc/gshadow
Security identifiers
- CCE-27162-7
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.j. Verify User Who Owns passwd File
To properly set the owner of /etc/passwd
, run the command:
$ sudo chown root /etc/passwd
The /etc/passwd
file contains information about the users that are configured on
the system. Protection of this file is critical for system security.
Remediation script
chown root /etc/passwd
Security identifiers
- CCE-27138-7
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.k. Verify Group Who Owns passwd File
To properly set the group owner of /etc/passwd
, run the command:
$ sudo chgrp root xsl:value-of select="@file"/>
The /etc/passwd
file contains information about the users that are configured on
the system. Protection of this file is critical for system security.
Remediation script
chgrp root /etc/passwd
Security identifiers
- CCE-26639-5
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.8.l. Verify Permissions on passwd File
To properly set the permissions of /etc/passwd
, run the command:
$ sudo chmod 0644 /etc/passwd
If the /etc/passwd
file is writable by a group-owner or the
world the risk of its compromise is increased. The file contains the list of
accounts on the system and associated information, and protection of this file
is critical for system security.
Remediation script
chmod 0644 /etc/passwd
Security identifiers
- CCE-26887-0
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.9. Verify File Permissions Within Some Important Directories
Some directories contain files whose confidentiality or integrity is notably important and may also be susceptible to misconfiguration over time, particularly if unpackaged software is installed. As such, an argument exists to verify that files' permissions within these directories remain configured correctly and restrictively.
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2.2.3.9.a. Verify that Shared Library Files Have Restrictive Permissions
System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default:
/lib
/lib64
/usr/lib
/usr/lib64
Kernel modules, which can be added to the kernel during runtime, are
stored in /lib/modules
. All files in these directories
should not be group-writable or world-writable. If any file in these
directories is found to be group-writable or world-writable, correct
its permission with the following command:
$ sudo chmod go-w FILE
Files from shared library directories are loaded into the address space of processes (including privileged ones) or of the kernel itself at runtime. Restrictive permissions are necessary to protect the integrity of the system.
Remediation script
DIRS="/lib /lib64 /usr/lib /usr/lib64"
for dirPath in $DIRS; do
find "$dirPath" -perm /022 -type f -exec chmod go-w '{}' \;
done
Security identifiers
- CCE-26966-2
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.9.b. Verify that Shared Library Files Have Root Ownership
System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default:
/lib
/lib64
/usr/lib
/usr/lib64
Kernel modules, which can be added to the kernel during runtime, are also
stored in /lib/modules
. All files in these directories should be
owned by the root
user. If the directory, or any file in these
directories, is found to be owned by a user other than root correct its
ownership with the following command:
$ sudo chown root FILE
Files from shared library directories are loaded into the address space of processes (including privileged ones) or of the kernel itself at runtime. Proper ownership is necessary to protect the integrity of the system.
Remediation script
for LIBDIR in /usr/lib /usr/lib64 /lib /lib64
do
if [ -d $LIBDIR ]
then
find -L $LIBDIR \! -user root -exec chown root {} \;
fi
done
Security identifiers
- CCE-26648-6
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20130914 by swells. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.3.9.c. Verify that System Executables Have Restrictive Permissions
System executables are stored in the following directories by default:
/bin
/usr/bin
/usr/local/bin
/sbin
/usr/sbin
/usr/local/sbin
All files in these directories should not be group-writable or world-writable.
If any file FILE in these directories is found
to be group-writable or world-writable, correct its permission with the
following command:
$ sudo chmod go-w FILE
System binaries are executed by privileged users, as well as system services, and restrictive permissions are necessary to ensure execution of these programs cannot be co-opted.
Remediation script
DIRS="/bin /usr/bin /usr/local/bin /sbin /usr/sbin /usr/local/sbin"
for dirPath in $DIRS; do
find "$dirPath" -perm /022 -exec chmod go-w '{}' \;
done
Security identifiers
- CCE-27075-1
References
2.2.3.9.d. Verify that System Executables Have Root Ownership
System executables are stored in the following directories by default:
/bin
/usr/bin
/usr/local/bin
/sbin
/usr/sbin
/usr/local/sbin
All files in these directories should be owned by the root
user.
If any file FILE in these directories is found
to be owned by a user other than root, correct its ownership with the
following command:
$ sudo chown root FILE
System binaries are executed by privileged users as well as system services, and restrictive permissions are necessary to ensure that their execution of these programs cannot be co-opted.
Remediation script
find /bin/ \
/usr/bin/ \
/usr/local/bin/ \
/sbin/ \
/usr/sbin/ \
/usr/local/sbin/ \
\! -user root -execdir chown root {} \;
Security identifiers
- CCE-27119-7
References
2.2.4. Restrict Programs from Dangerous Execution Patterns
The recommendations in this section are designed to ensure that the system's features to protect against potentially dangerous program execution are activated. These protections are applied at the system initialization or kernel level, and defend against certain types of badly-configured or compromised programs.
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2.2.4.a. Restrict Access to Kernel Message Buffer
To set the runtime status of the kernel.dmesg_restrict
kernel parameter,
run the following command:
$ sudo sysctl -w kernel.dmesg_restrict=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
kernel.dmesg_restrict = 1
Unprivileged access to the kernel syslog can expose sensitive kernel address information.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SI-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1314. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.2.4.2. Daemon Umask
The umask is a per-process setting which limits the default permissions for creation of new files and directories. The system includes initialization scripts which set the default umask for system daemons.
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2.2.4.2.a. Set Daemon Umask
The file /etc/init.d/functions
includes initialization
parameters for most or all daemons started at boot time. The default umask of
022 prevents creation of group- or world-writable files. To set the default
umask for daemons, edit the following line, inserting 022 or 027 for
UMASK appropriately:
umask 022
Setting the umask to too restrictive a setting can cause serious errors at
runtime. Many daemons on the system already individually restrict themselves to
a umask of 077 in their own init scripts.
The umask influences the permissions assigned to files created by a process at run time. An unnecessarily permissive umask could result in files being created with insecure permissions.
Remediation script
var_umask_for_daemons="022"
grep -q ^umask /etc/init.d/functions && \
sed -i "s/umask.*/umask $var_umask_for_daemons/g" /etc/init.d/functions
if ! [ $? -eq 0 ]; then
echo "umask $var_umask_for_daemons" >> /etc/init.d/functions
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20140912 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.4.3. Disable Core Dumps
A core dump file is the memory image of an executable
program when it was terminated by the operating system due to
errant behavior. In most cases, only software developers
legitimately need to access these files. The core dump files may
also contain sensitive information, or unnecessarily occupy large
amounts of disk space.
Once a hard limit is set in /etc/security/limits.conf
, a
user cannot increase that limit within his or her own session. If access
to core dumps is required, consider restricting them to only
certain users or groups. See the limits.conf
man page for more
information.
The core dumps of setuid programs are further protected. The
sysctl
variable fs.suid_dumpable
controls whether
the kernel allows core dumps from these programs at all. The default
value of 0 is recommended.
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2.2.4.3.a. Disable Core Dumps for All Users
To disable core dumps for all users, add the following line to
/etc/security/limits.conf
:
* hard core 0
A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.
Remediation script
echo "* hard core 0" >> /etc/security/limits.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.4.3.b. Disable Core Dumps for SUID programs
To set the runtime status of the fs.suid_dumpable
kernel parameter,
run the following command:
$ sudo sysctl -w fs.suid_dumpable=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
fs.suid_dumpable = 0
The core dump of a setuid program is more likely to contain sensitive data, as the program itself runs with greater privileges than the user who initiated execution of the program. Disabling the ability for any setuid program to write a core file decreases the risk of unauthorized access of such data.
Remediation script
#
# Set runtime for fs.suid_dumpable
#
sysctl -q -n -w fs.suid_dumpable=0
#
# If fs.suid_dumpable present in /etc/sysctl.conf, change value to "0"
# else, add "fs.suid_dumpable = 0" to /etc/sysctl.conf
#
if grep --silent ^fs.suid_dumpable /etc/sysctl.conf ; then
sed -i 's/^fs.suid_dumpable.*/fs.suid_dumpable = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set fs.suid_dumpable to 0 per security requirements" >> /etc/sysctl.conf
echo "fs.suid_dumpable = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.4.4. Enable ExecShield
ExecShield describes kernel features that provide
protection against exploitation of memory corruption errors such as buffer
overflows. These features include random placement of the stack and other
memory regions, prevention of execution in memory that should only hold data,
and special handling of text buffers. These protections are enabled by default
on 32-bit systems and controlled through sysctl
variables
kernel.exec-shield
and kernel.randomize_va_space
. On the latest
64-bit systems, kernel.exec-shield
cannot be enabled or disabled with
sysctl
.
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2.2.4.4.a. Enable ExecShield
By default on Red Hat Enterprise Linux 7 64-bit systems, ExecShield
is enabled and can only be disabled if the hardware does not support ExecShield
or is disabled in /etc/default/grub
. For Red Hat Enterprise Linux 7
32-bit systems, sysctl
can be used to enable ExecShield.
ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis. When the kernel places a process's memory regions such as the stack and heap higher than this address, the hardware prevents execution in that address range. This is enabled by default on the latest Red Hat and Fedora systems if supported by the hardware.
Remediation script
#
# Set runtime for kernel.exec-shield
#
sysctl -q -n -w kernel.exec-shield=1
#
# If kernel.exec-shield present in /etc/sysctl.conf, change value to "1"
# else, add "kernel.exec-shield = 1" to /etc/sysctl.conf
#
if grep --silent ^kernel.exec-shield /etc/sysctl.conf ; then
sed -i 's/^kernel.exec-shield.*/kernel.exec-shield = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set kernel.exec-shield to 1 per security requirements" >> /etc/sysctl.conf
echo "kernel.exec-shield = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SC-39. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 2530. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.4.4.b. Enable Randomized Layout of Virtual Address Space
To set the runtime status of the kernel.randomize_va_space
kernel parameter,
run the following command:
$ sudo sysctl -w kernel.randomize_va_space=2
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
kernel.randomize_va_space = 2
Address space layout randomization (ASLR) makes it more difficult for an attacker to predict the location of attack code they have introduced into a process's address space during an attempt at exploitation. Additionally, ASLR makes it more difficult for an attacker to know the location of existing code in order to re-purpose it using return oriented programming (ROP) techniques.
Remediation script
#
# Set runtime for kernel.randomize_va_space
#
sysctl -q -n -w kernel.randomize_va_space=2
#
# If kernel.randomize_va_space present in /etc/sysctl.conf, change value to "2"
# else, add "kernel.randomize_va_space = 2" to /etc/sysctl.conf
#
if grep --silent ^kernel.randomize_va_space /etc/sysctl.conf ; then
sed -i 's/^kernel.randomize_va_space.*/kernel.randomize_va_space = 2/g' /etc/sysctl.conf
else
echo -e "\n# Set kernel.randomize_va_space to 2 per security requirements" >> /etc/sysctl.conf
echo "kernel.randomize_va_space = 2" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SC-30(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.2.4.5. Enable Execute Disable (XD) or No Execute (NX) Support on x86 Systems
Recent processors in the x86 family support the ability to prevent code execution on a per memory page basis. Generically and on AMD processors, this ability is called No Execute (NX), while on Intel processors it is called Execute Disable (XD). This ability can help prevent exploitation of buffer overflow vulnerabilities and should be activated whenever possible. Extra steps must be taken to ensure that this protection is enabled, particularly on 32-bit x86 systems. Other processors, such as Itanium and POWER, have included such support since inception and the standard kernel for those platforms supports the feature. This is enabled by default on the latest Red Hat and Fedora systems if supported by the hardware.
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2.2.4.5.a. Install PAE Kernel on Supported 32-bit x86 Systems
Systems that are using the 64-bit x86 kernel package do not need to install the kernel-PAE package because the 64-bit x86 kernel already includes this support. However, if the system is 32-bit and also supports the PAE and NX features as determined in the previous section, the kernel-PAE package should be installed to enable XD or NX support:
$ sudo yum install kernel-PAE
The installation process should also have configured the
bootloader to load the new kernel at boot. Verify this at reboot
and modify /etc/default/grub
if necessary.
The kernel-PAE package should not be installed on older systems that do not support the XD or NX bit, as this may prevent them from booting.
On 32-bit systems that support the XD or NX bit, the vendor-supplied PAE kernel is required to enable either Execute Disable (XD) or No Execute (NX) support.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.2.4.5.b. Enable NX or XD Support in the BIOS
Reboot the system and enter the BIOS or Setup configuration menu. Navigate the BIOS configuration menu and make sure that the option is enabled. The setting may be located under a Security section. Look for Execute Disable (XD) on Intel-based systems and No Execute (NX) on AMD-based systems.
Computers with the ability to prevent this type of code execution frequently put an option in the BIOS that will allow users to turn the feature on or off at will.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.3. SELinux
SELinux is a feature of the Linux kernel which can be
used to guard against misconfigured or compromised programs.
SELinux enforces the idea that programs should be limited in what
files they can access and what actions they can take.
The default SELinux policy, as configured on Red Hat Enterprise Linux 7, has been
sufficiently developed and debugged that it should be usable on
almost any Red Hat machine with minimal configuration and a small
amount of system administrator training. This policy prevents
system services - including most of the common network-visible
services such as mail servers, FTP servers, and DNS servers - from
accessing files which those services have no valid reason to
access. This action alone prevents a huge amount of possible damage
from network attacks against services, from trojaned software, and
so forth.
This guide recommends that SELinux be enabled using the
default (targeted) policy on every Red Hat system, unless that
system has unusual requirements which make a stronger policy
appropriate.
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2.3.a. Ensure SELinux Not Disabled in /etc/grub.conf
SELinux can be disabled at boot time by an argument in
/etc/grub.conf
.
Remove any instances of selinux=0
from the kernel arguments in that
file to prevent SELinux from being disabled at boot.
Disabling a major host protection feature, such as SELinux, at boot time prevents it from confining system services at boot time. Further, it increases the chances that it will remain off during system operation.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-3(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 22. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 32. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.3.b. Ensure SELinux State is Enforcing
The SELinux state should be set to enforcing
at
system boot time. In the file /etc/selinux/config
, add or correct the
following line to configure the system to boot into enforcing mode:
SELINUX=enforcing
Setting the SELinux state to enforcing ensures SELinux is able to confine potentially compromised processes to the security policy, which is designed to prevent them from causing damage to the system or further elevating their privileges.
Remediation script
var_selinux_state="enforcing"
grep -q ^SELINUX= /etc/selinux/config && \
sed -i "s/SELINUX=.*/SELINUX=$var_selinux_state/g" /etc/selinux/config
if ! [ $? -eq 0 ]; then
echo "SELINUX=$var_selinux_state" >> /etc/selinux/config
fi
Security identifiers
- CCE-26800-3
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-3(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.3.c. Configure SELinux Policy
The SELinux targeted
policy is appropriate for
general-purpose desktops and servers, as well as systems in many other roles.
To configure the system to use this policy, add or correct the following line
in /etc/selinux/config
:
SELINUXTYPE=targeted
Other policies, such as mls
, provide additional security labeling
and greater confinement but are not compatible with many general-purpose
use cases.
Setting the SELinux policy to targeted
or a more specialized policy
ensures the system will confine processes that are likely to be
targeted for exploitation, such as network or system services.
Note: During the development or debugging of SELinux modules, it is common to
temporarily place non-production systems in permissive
mode. In such
temporary cases, SELinux policies should be developed, and once work
is completed, the system should be reconfigured to
targeted
.
Remediation script
var_selinux_policy_name="targeted"
grep -q ^SELINUXTYPE /etc/selinux/config && \
sed -i "s/SELINUXTYPE=.*/SELINUXTYPE=$var_selinux_policy_name/g" /etc/selinux/config
if ! [ $? -eq 0 ]; then
echo "SELINUXTYPE=$var_selinux_policy_name" >> /etc/selinux/config
fi
Security identifiers
- CCE-27135-3
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-3(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.3.d. Uninstall setroubleshoot Package
The SETroubleshoot service notifies desktop users of SELinux
denials. The service provides information around configuration errors,
unauthorized intrusions, and other potential errors.
The setroubleshoot
package can be removed with the following command:
$ sudo yum erase setroubleshoot
The SETroubleshoot service is an unnecessary daemon to have running on a server
Security identifiers
- CCE-
2.3.e. Uninstall mcstrans Package
The mcstransd
daemon provides category label information
to client processes requesting information. The label translations are defined
in /etc/selinux/targeted/setrans.conf
.
The mcstrans
package can be removed with the following command:
$ sudo yum erase mcstrans
Since this service is not used very often, disable it to reduce the amount of potentially vulnerable code running on the system. NOTE: This rule was added in support of the CIS RHEL6 v1.2.0 benchmark. Please note that Red Hat does not feel this rule is security relevant.
Security identifiers
- CCE-
2.3.f. Ensure No Daemons are Unconfined by SELinux
Daemons for which the SELinux policy does not contain rules will inherit the
context of the parent process. Because daemons are launched during
startup and descend from the init
process, they inherit the initrc_t
context.
To check for unconfined daemons, run the following command:
$ sudo ps -eZ | egrep "initrc" | egrep -vw "tr|ps|egrep|bash|awk" | tr ':' ' ' | awk '{ print $NF }'
It should produce no output in a well-configured system.
Daemons which run with the initrc_t
context may cause AVC denials,
or allow privileges that the daemon does not require.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.3.g. Ensure No Device Files are Unlabeled by SELinux
Device files, which are used for communication with important
system resources, should be labeled with proper SELinux types. If any device
files carry the SELinux type unlabeled_t
, investigate the cause and
correct the file's context.
If a device file carries the SELinux type unlabeled_t
, then SELinux
cannot properly restrict access to the device file.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 22. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 32. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4. Account and Access Control
In traditional Unix security, if an attacker gains shell access to a certain login account, they can perform any action or access any file to which that account has access. Therefore, making it more difficult for unauthorized people to gain shell access to accounts, particularly to privileged accounts, is a necessary part of securing a system. This section introduces mechanisms for restricting access to accounts under Red Hat Enterprise Linux 7.
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2.4.1. Protect Accounts by Restricting Password-Based Login
Conventionally, Unix shell accounts are accessed by
providing a username and password to a login program, which tests
these values for correctness using the /etc/passwd
and
/etc/shadow
files. Password-based login is vulnerable to
guessing of weak passwords, and to sniffing and man-in-the-middle
attacks against passwords entered over a network or at an insecure
console. Therefore, mechanisms for accessing accounts by entering
usernames and passwords should be restricted to those which are
operationally necessary.
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2.4.1.1. Restrict Root Logins
Direct root logins should be allowed only for emergency use.
In normal situations, the administrator should access the system
via a unique unprivileged account, and then use su
or sudo
to execute
privileged commands. Discouraging administrators from accessing the
root account directly ensures an audit trail in organizations with
multiple administrators. Locking down the channels through which
root can connect directly also reduces opportunities for
password-guessing against the root account. The login
program
uses the file /etc/securetty
to determine which interfaces
should allow root logins.
The virtual devices /dev/console
and /dev/tty*
represent the system consoles (accessible via
the Ctrl-Alt-F1 through Ctrl-Alt-F6 keyboard sequences on a default
installation). The default securetty file also contains /dev/vc/*
.
These are likely to be deprecated in most environments, but may be retained
for compatibility. Root should also be prohibited from connecting
via network protocols. Other sections of this document
include guidance describing how to prevent root from logging in via SSH.
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2.4.1.1.a. Direct root Logins Not Allowed
To further limit access to the root
account, administrators
can disable root logins at the console by editing the /etc/securetty
file.
This file lists all devices the root user is allowed to login to. If the file does
not exist at all, the root user can login through any communication device on the
system, whether via the console or via a raw network interface. This is dangerous
as user can login to his machine as root via Telnet, which sends the password in
plain text over the network. By default, Red Hat Enteprise Linux's
/etc/securetty
file only allows the root user to login at the console
physically attached to the machine. To prevent root from logging in, remove the
contents of this file. To prevent direct root logins, remove the contents of this
file by typing the following command:
$ sudo echo > /etc/securetty
Disabling direct root logins ensures proper accountability and multifactor authentication to privileged accounts. Users will first login, then escalate to privileged (root) access via su / sudo. This is required for FISMA Low and FISMA Moderate systems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- IA-2(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.1.b. Restrict Virtual Console Root Logins
To restrict root logins through the (deprecated) virtual console devices,
ensure lines of this form do not appear in /etc/securetty
:
vc/1
vc/2
vc/3
vc/4
Preventing direct root login to virtual console devices helps ensure accountability for actions taken on the system using the root account.
Remediation script
sed -i '/^vc\//d' /etc/securetty
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 770. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.1.c. Restrict Serial Port Root Logins
To restrict root logins on serial ports,
ensure lines of this form do not appear in /etc/securetty
:
ttyS0
ttyS1
Preventing direct root login to serial port interfaces helps ensure accountability for actions taken on the systems using the root account.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 770. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.1.d. Restrict Web Browser Use for Administrative Accounts
Enforce policy requiring administrative accounts use web browsers only for local service administration.
If a browser vulnerability is exploited while running with administrative privileges, the entire system could be compromised. Specific exceptions for local service administration should be documented in site-defined policy.
Security identifiers
- CCE-RHEL7-CCE-TBD
2.4.1.1.e. Ensure that System Accounts Do Not Run a Shell Upon Login
Some accounts are not associated with a human
user of the system, and exist to perform some administrative
function. Should an attacker be able to log into these accounts,
they should not be granted access to a shell.
The login shell for each local account is stored in the last field of each line
in /etc/passwd
. System accounts are those user accounts with a user ID less than
1000. The user ID is stored in the third field.
If any system account SYSACCT (other than root) has a login shell,
disable it with the command:
$ sudo usermod -s /sbin/nologin SYSACCT
Do not perform the steps in this section on the root account. Doing so might cause the system to become inaccessible.
Ensuring shells are not given to system accounts upon login makes it more difficult for attackers to make use of system accounts.
Security identifiers
- CCE-26448-1
References
- AC-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.1.f. Verify Only Root Has UID 0
If any account other than root has a UID of 0, this misconfiguration should be investigated and the accounts other than root should be removed or have their UID changed.
An account has root authority if it has a UID of 0. Multiple accounts with a UID of 0 afford more opportunity for potential intruders to guess a password for a privileged account. Proper configuration of sudo is recommended to afford multiple system administrators access to root privileges in an accountable manner.
Remediation script
awk -F: '$3 == 0 && $1 != "root" { print $1 }' /etc/passwd | xargs passwd -l
Security identifiers
- CCE-27175-9
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-2(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.1.g. Root Path Must Be Vendor Default
Assuming root shell is bash, edit the following files:
~/.profile
~/.bashrc
Change any PATH
variables to the vendor default for root and remove any
empty PATH
entries or references to relative paths.
The root account's executable search path must be the vendor default, and must contain only absolute paths.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.2. Verify Proper Storage and Existence of Password Hashes
By default, password hashes for local accounts are stored
in the second field (colon-separated) in
/etc/shadow
. This file should be readable only by
processes running with root credentials, preventing users from
casually accessing others' password hashes and attempting
to crack them.
However, it remains possible to misconfigure the system
and store password hashes
in world-readable files such as /etc/passwd
, or
to even store passwords themselves in plaintext on the system.
Using system-provided tools for password change/creation
should allow administrators to avoid such misconfiguration.
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2.4.1.2.a. Prevent Log In to Accounts With Empty Password
If an account is configured for password authentication
but does not have an assigned password, it may be possible to log
into the account without authentication. Remove any instances of the nullok
option in /etc/pam.d/system-auth
to
prevent logins with empty passwords.
If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.
Remediation script
sed -i 's/\<nullok\>//g' /etc/pam.d/system-auth
Security identifiers
- CCE-27010-8
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.2.b. Verify All Account Password Hashes are Shadowed
If any password hashes are stored in /etc/passwd
(in the second field,
instead of an x
), the cause of this misconfiguration should be
investigated. The account should have its password reset and the hash should be
properly stored, or the account should be deleted entirely.
The hashes for all user account passwords should be stored in
the file /etc/shadow
and never in /etc/passwd
,
which is readable by all users.
Security identifiers
- CCE-27144-5
References
- IA-5(h). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.2.c. All GIDs referenced in /etc/passwd must be defined in /etc/group
Add a group to the system for each GID referenced without a corresponding group.
Inconsistency in GIDs between /etc/passwd
and /etc/group
could lead to a user having unintended rights.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.2.d. Verify No netrc Files Exist
The .netrc
files contain login information
used to auto-login into FTP servers and reside in the user's home
directory. These files may contain unencrypted passwords to
remote FTP servers making them susceptible to access by unauthorized
users and should not be used. Any .netrc
files should be removed.
Unencrypted passwords for remote FTP servers may be stored in .netrc
files. DoD policy requires passwords be encrypted in storage and not used
in access scripts.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.4.1.3. Set Password Expiration Parameters
The file /etc/login.defs
controls several
password-related settings. Programs such as passwd
,
su
, and
login
consult /etc/login.defs
to determine
behavior with regard to password aging, expiration warnings,
and length. See the man page login.defs(5)
for more information.
Users should be forced to change their passwords, in order to
decrease the utility of compromised passwords. However, the need to
change passwords often should be balanced against the risk that
users will reuse or write down passwords if forced to change them
too often. Forcing password changes every 90-360 days, depending on
the environment, is recommended. Set the appropriate value as
PASS_MAX_DAYS
and apply it to existing accounts with the
-M
flag.
The PASS_MIN_DAYS
(-m
) setting prevents password
changes for 7 days after the first change, to discourage password
cycling. If you use this setting, train users to contact an administrator
for an emergency password change in case a new password becomes
compromised. The PASS_WARN_AGE
(-W
) setting gives
users 7 days of warnings at login time that their passwords are about to expire.
For example, for each existing human user USER, expiration parameters
could be adjusted to a 180 day maximum password age, 7 day minimum password
age, and 7 day warning period with the following command:
$ sudo chage -M 180 -m 7 -W 7 USER
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2.4.1.3.a. Set Password Minimum Length in login.defs
To specify password length requirements for new accounts,
edit the file /etc/login.defs
and add or correct the following
lines:
PASS_MIN_LEN 14
The DoD requirement is
14
.
The FISMA requirement is 12
.
If a program consults /etc/login.defs
and also another PAM module
(such as pam_pwquality
) during a password change operation,
then the most restrictive must be satisfied. See PAM section
for more information about enforcing password quality requirements.
Requiring a minimum password length makes password cracking attacks more difficult by ensuring a larger search space. However, any security benefit from an onerous requirement must be carefully weighed against usability problems, support costs, or counterproductive behavior that may result.
Remediation script
var_accounts_password_minlen_login_defs="14"
grep -q ^PASS_MIN_LEN /etc/login.defs && \
sed -i "s/PASS_MIN_LEN.*/PASS_MIN_LEN $var_accounts_password_minlen_login_defs/g" /etc/login.defs
if ! [ $? -eq 0 ]; then
echo "PASS_MIN_LEN $var_accounts_password_minlen_login_defs" >> /etc/login.defs
fi
Security identifiers
- CCE-27123-9
References
- IA-5(f). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.3.b. Set Password Minimum Age
To specify password minimum age for new accounts,
edit the file /etc/login.defs
and add or correct the following line, replacing DAYS appropriately:
PASS_MIN_DAYS DAYS
A value of 1 day is considered for sufficient for many
environments.
The DoD requirement is 1.
Setting the minimum password age protects against users cycling back to a favorite password after satisfying the password reuse requirement.
Remediation script
var_accounts_minimum_age_login_defs="7"
grep -q ^PASS_MIN_DAYS /etc/login.defs && \
sed -i "s/PASS_MIN_DAYS.*/PASS_MIN_DAYS $var_accounts_minimum_age_login_defs/g" /etc/login.defs
if ! [ $? -eq 0 ]; then
echo "PASS_MIN_DAYS $var_accounts_minimum_age_login_defs" >> /etc/login.defs
fi
Security identifiers
- CCE-27002-5
References
- IA-5(f). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 198. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 75. .
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.3.c. Set Password Maximum Age
To specify password maximum age for new accounts,
edit the file /etc/login.defs
and add or correct the following line, replacing DAYS appropriately:
PASS_MAX_DAYS DAYS
A value of 180 days is sufficient for many environments.
The DoD requirement is 60.
Setting the password maximum age ensures users are required to periodically change their passwords. This could possibly decrease the utility of a stolen password. Requiring shorter password lifetimes increases the risk of users writing down the password in a convenient location subject to physical compromise.
Remediation script
var_accounts_maximum_age_login_defs="60"
grep -q ^PASS_MAX_DAYS /etc/login.defs && \
sed -i "s/PASS_MAX_DAYS.*/PASS_MAX_DAYS $var_accounts_maximum_age_login_defs/g" /etc/login.defs
if ! [ $? -eq 0 ]; then
echo "PASS_MAX_DAYS $var_accounts_maximum_age_login_defs" >> /etc/login.defs
fi
Security identifiers
- CCE-27051-2
References
- IA-5(f). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(g). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 180. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 199. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 76. .
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.3.d. Set Password Warning Age
To specify how many days prior to password
expiration that a warning will be issued to users,
edit the file /etc/login.defs
and add or correct
the following line, replacing DAYS appropriately:
PASS_WARN_AGE DAYS
The DoD requirement is 7.
Setting the password warning age enables users to make the change at a practical time.
Remediation script
var_accounts_password_warn_age_login_defs="7"
grep -q ^PASS_WARN_AGE /etc/login.defs && \
sed -i "s/PASS_WARN_AGE.*/PASS_WARN_AGE $var_accounts_password_warn_age_login_defs/g" /etc/login.defs
if ! [ $? -eq 0 ]; then
echo "PASS_WARN_AGE $var_accounts_password_warn_age_login_defs" >> /etc/login.defs
fi
Security identifiers
- CCE-26486-1
References
- AC-2(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(f). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.1.4. Set Account Expiration Parameters
Accounts can be configured to be automatically disabled
after a certain time period,
meaning that they will require administrator interaction to become usable again.
Expiration of accounts after inactivity can be set for all accounts by default
and also on a per-account basis, such as for accounts that are known to be temporary.
To configure automatic expiration of an account following
the expiration of its password (that is, after the password has expired and not been changed),
run the following command, substituting NUM_DAYS
and USER
appropriately:
$ sudo chage -I NUM_DAYS USER
Accounts, such as temporary accounts, can also be configured to expire on an explicitly-set date with the
-E
option.
The file /etc/default/useradd
controls
default settings for all newly-created accounts created with the system's
normal command line utilities.
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2.4.1.4.a. Set Account Expiration Following Inactivity
To specify the number of days after a password expires (which
signifies inactivity) until an account is permanently disabled, add or correct
the following lines in /etc/default/useradd
, substituting
NUM_DAYS
appropriately:
INACTIVE=
A value of 35 is recommended.
If a password is currently on the
verge of expiration, then 35 days remain until the account is automatically
disabled. However, if the password will not expire for another 60 days, then 95
days could elapse until the account would be automatically disabled. See the
useradd
man page for more information. Determining the inactivity
timeout must be done with careful consideration of the length of a "normal"
period of inactivity for users in the particular environment. Setting
the timeout too low incurs support costs and also has the potential to impact
availability of the system to legitimate users.
Disabling inactive accounts ensures that accounts which may not have been responsibly removed are not available to attackers who may have compromised their credentials.
Remediation script
var_account_disable_post_pw_expiration="35"
grep -q ^INACTIVE /etc/default/useradd && \
sed -i "s/INACTIVE.*/INACTIVE=$var_account_disable_post_pw_expiration/g" /etc/default/useradd
if ! [ $? -eq 0 ]; then
echo "INACTIVE=$var_account_disable_post_pw_expiration" >> /etc/default/useradd
fi
Security identifiers
- CCE-TBD
References
- AC-2(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-2(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 16. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 17. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 795. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.1.4.b. Ensure All Accounts on the System Have Unique Names
Change usernames, or delete accounts, so each has a unique name.
Unique usernames allow for accountability on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 770. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 804. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.1.4.c. Assign Expiration Date to Temporary Accounts
Temporary accounts are established as part of normal account activation procedures
when there is a need for short-term accounts. In the event temporary
or emergency accounts are required, configure the system to terminate
them after a documented time period. For every temporary and
emergency account, run the following command to set an expiration date on it,
substituting USER
and YYYY-MM-DD
appropriately:
$ sudo chage -E YYYY-MM-DD USER
YYYY-MM-DD
indicates the documented expiration date for the account.
For U.S. Government systems, the operating system must be configured to automatically terminate
these typoes of accounts after a period of 72 hours.
If temporary user accounts remain active when no longer needed or for
an excessive period, these accounts may be used to gain unauthorized access.
To mitigate this risk, automated termination of all temporary accounts
must be set upon account creation.
Security identifiers
- CCE-27498-5
References
- AC-2(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-2(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 16. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1682. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 2. .
2.4.2. Protect Accounts by Configuring PAM
PAM, or Pluggable Authentication Modules, is a system
which implements modular authentication for Linux programs. PAM provides
a flexible and configurable architecture for authentication, and it should be configured
to minimize exposure to unnecessary risk. This section contains
guidance on how to accomplish that.
PAM is implemented as a set of shared objects which are
loaded and invoked whenever an application wishes to authenticate a
user. Typically, the application must be running as root in order
to take advantage of PAM, because PAM's modules often need to be able
to access sensitive stores of account information, such as /etc/shadow.
Traditional privileged network listeners
(e.g. sshd) or SUID programs (e.g. sudo) already meet this
requirement. An SUID root application, userhelper, is provided so
that programs which are not SUID or privileged themselves can still
take advantage of PAM.
PAM looks in the directory /etc/pam.d
for
application-specific configuration information. For instance, if
the program login attempts to authenticate a user, then PAM's
libraries follow the instructions in the file /etc/pam.d/login
to determine what actions should be taken.
One very important file in /etc/pam.d
is
/etc/pam.d/system-auth
. This file, which is included by
many other PAM configuration files, defines 'default' system authentication
measures. Modifying this file is a good way to make far-reaching
authentication changes, for instance when implementing a
centralized authentication service.
Be careful when making changes to PAM's configuration files. The syntax for these files is complex, and modifications can have unexpected consequences. The default configurations shipped with applications should be sufficient for most users.
Running authconfig
or
system-config-authentication
will re-write the PAM configuration
files, destroying any manually made changes and replacing them with
a series of system defaults. One reference to the configuration
file syntax can be found at
http://www.kernel.org/pub/linux/libs/pam/Linux-PAM-html/sag-configuration-file.html.
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2.4.2.a. Set Last Logon/Access Notification
To configure the system to notify users of last logon/access
using pam_lastlog
, add or correct the pam_lastlog
settings in
/etc/pam.d/postlogin
to read as follows:
session [success=1 default=ignore] pam_succeed_if.so service !~ gdm* service !~ su* quiet
session [default=1] pam_lastlog.so nowtmp showfailed
session optional pam_lastlog.so silent noupdate showfailed
Users need to be aware of activity that occurs regarding their account. Providing users with information regarding the number of unsuccessful attempts that were made to login to their account allows the user to determine if any unauthorized activity has occurred and gives them an opportunity to notify administrators.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 53. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.2.2. Set Password Quality Requirements
The default pam_pwquality
PAM module provides strength
checking for passwords. It performs a number of checks, such as
making sure passwords are not similar to dictionary words, are of
at least a certain length, are not the previous password reversed,
and are not simply a change of case from the previous password. It
can also require passwords to be in certain character classes. The
pam_pwquality
module is the preferred way of configuring
password requirements.
The pam_cracklib
PAM module can also provide strength
checking for passwords as the pam_pwquality
module.
It performs a number of checks, such as making sure passwords are
not similar to dictionary words, are of at least a certain length,
are not the previous password reversed, and are not simply a change
of case from the previous password. It can also require passwords to
be in certain character classes.
The man pages pam_pwquality(8)
and pam_cracklib(8)
provide information on the capabilities and configuration of
each.
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2.4.2.2.1. Set Password Quality Requirements with pam_pwquality
The pam_pwquality
PAM module can be configured to meet
requirements for a variety of policies.
For example, to configure pam_pwquality
to require at least one uppercase
character, lowercase character, digit, and other (special)
character, make sure that pam_pwquality
exists in /etc/pam.d/system-auth
:
password requisite pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=
If no such line exists, add one as the first line of the password section in /etc/pam.d/system-auth
.
Next, modify the settings in /etc/security/pwquality.conf
to match the following:
difok = 4
minlen = 14
dcredit = -1
ucredit = -1
lcredit = -1
ocredit = -1
maxrepeat = 3
The arguments can be modified to ensure compliance with
your organization's security policy. Discussion of each parameter follows.
Note that the password quality requirements are not enforced for the root account for some reason.
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2.4.2.2.1.a. Set Password Retry Prompts Permitted Per-Session
To configure the number of retry prompts that are permitted per-session:
Edit the pam_pwquality.so
statement in /etc/pam.d/system-auth
to
show retry=3
, or a lower value if site policy is more restrictive.
The DoD requirement is a maximum of 3 prompts per session.
Setting the password retry prompts that are permitted on a per-session basis to a low value requires some software, such as SSH, to re-connect. This can slow down and draw additional attention to some types of password-guessing attacks. Note that this is different from account lockout, which is provided by the pam_faillock module.
Remediation script
var_password_pam_retry="3"
if grep -q "retry=" /etc/pam.d/system-auth; then
sed -i --follow-symlink "s/\(retry *= *\).*/\1$var_password_pam_retry/" /etc/pam.d/system-auth
else
sed -i --follow-symlink "/pam_pwquality.so/ s/$/ retry=$var_password_pam_retry/" /etc/pam.d/system-auth
fi
Security identifiers
- CCE-27131-2
References
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20140925 by swells. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.b. Set Password to Maximum of Three Consecutive Repeating Characters
The pam_pwquality module's maxrepeat
parameter controls requirements for
consecutive repeating characters. When set to a positive number, it will reject passwords
which contain more than that number of consecutive characters. Modify the maxrepeat
setting
in /etc/security/pwquality.conf
to equal 3 to prevent a run of (3 + 1) or more identical characters.
Passwords with excessive repeating characters may be more vulnerable to password-guessing attacks.
Remediation script
var_password_pam_maxrepeat="3"
if egrep -q ^maxrepeat[[:space:]]*=[[:space:]]*[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(maxrepeat *= *\).*/\1$var_password_pam_maxrepeat/" /etc/security/pwquality.conf
else
sed -i "/\(maxrepeat *= *\).*/a maxrepeat = $var_password_pam_maxrepeat" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.2.2.1.c. Set Password Strength Minimum Digit Characters
The pam_pwquality module's dcredit
parameter controls requirements for
usage of digits in a password. When set to a negative number, any password will be required to
contain that many digits. When set to a positive number, pam_pwquality will grant +1 additional
length credit for each digit. Modify the dcredit
setting in
/etc/security/pwquality.conf
to require the use of a digit in passwords.
Requiring digits makes password guessing attacks more difficult by ensuring a larger search space.
Remediation script
var_password_pam_dcredit="-1"
if egrep -q ^dcredit[[:space:]]*=[[:space:]]*[-]?[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(dcredit *= *\).*/\1$var_password_pam_dcredit/" /etc/security/pwquality.conf
else
sed -i "/\(dcredit *= *\).*/a dcredit = $var_password_pam_dcredit" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-27163-5
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 194. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 194. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 71. .
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.d. Set Password Minimum Length
The pam_pwquality module's minlen
parameter controls requirements for
minimum characters required in a password. Add minlen=15
after pam_pwquality to set minimum password length requirements.
Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromise the password.
Remediation script
var_password_pam_minlen="15"
if egrep -q ^minlen[[:space:]]*=[[:space:]]*[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(minlen *= *\).*/\1$var_password_pam_minlen/" /etc/security/pwquality.conf
else
sed -i "/\(minlen *= *\).*/a minlen = $var_password_pam_minlen" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-26615-5
References
- IA-5(1)(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 205. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 78. .
- Test attestation on 20140928 by swells. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.e. Set Password Strength Minimum Uppercase Characters
The pam_pwquality module's ucredit=
parameter controls requirements for
usage of uppercase letters in a password. When set to a negative number, any password will be required to
contain that many uppercase characters. When set to a positive number, pam_pwquality will grant +1 additional
length credit for each uppercase character. Modify the ucredit
setting in
/etc/security/pwquality.conf
to require the use of an uppercase character in passwords.
Requiring a minimum number of uppercase characters makes password guessing attacks more difficult by ensuring a larger search space.
Remediation script
var_password_pam_ucredit="-1"
if egrep -q ^ucredit[[:space:]]*=[[:space:]]*[-]?[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(ucredit *= *\).*/\1$var_password_pam_ucredit/" /etc/security/pwquality.conf
else
sed -i "/\(ucredit *= *\).*/a ucredit = $var_password_pam_ucredit" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-26988-6
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 192. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 69. .
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.f. Set Password Strength Minimum Special Characters
The pam_pwquality module's ocredit=
parameter controls requirements for
usage of special (or "other") characters in a password. When set to a negative number, any password will be
required to contain that many special characters. When set to a positive number, pam_pwquality will grant +1
additional length credit for each special character. Modify the ocredit
setting in
/etc/security/pwquality.conf
to equal -1 to require use of a special character in passwords.
Requiring a minimum number of special characters makes password guessing attacks more difficult by ensuring a larger search space.
Remediation script
var_password_pam_ocredit="-1"
if egrep -q ^ocredit[[:space:]]*=[[:space:]]*[-]?[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(ocredit *= *\).*/\1$var_password_pam_ocredit/" /etc/security/pwquality.conf
else
sed -i "/\(ocredit *= *\).*/a ocredit = $var_password_pam_ocredit" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-27151-0
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1619. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 266. .
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.g. Set Password Strength Minimum Lowercase Characters
The pam_pwquality module's lcredit
parameter controls requirements for
usage of lowercase letters in a password. When set to a negative number, any password will be required to
contain that many lowercase characters. When set to a positive number, pam_pwquality will grant +1 additional
length credit for each lowercase character. Modify the lcredit
setting in
/etc/security/pwquality.conf
to require the use of a lowercase character in passwords.
Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.
Remediation script
var_password_pam_lcredit="-1"
if egrep -q ^lcredit[[:space:]]*=[[:space:]]*[-]?[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(lcredit *= *\).*/\1$var_password_pam_lcredit/" /etc/security/pwquality.conf
else
sed -i "/\(lcredit *= *\).*/a lcredit = $var_password_pam_lcredit" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-27111-4
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 193. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 70. .
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.h. Set Password Strength Minimum Different Characters
The pam_pwquality module's difok
parameter controls requirements for usage of different
characters during a password change. Modify the difok
setting in /etc/security/pwquality.conf
to equal 15 to require differing characters when changing passwords. The DoD requirement is 4
.
Requiring a minimum number of different characters during password changes ensures that newly changed passwords should not resemble previously compromised ones. Note that passwords which are changed on compromised systems will still be compromised, however.
Remediation script
var_password_pam_difok="15"
if egrep -q ^difok[[:space:]]*=[[:space:]]*[-]?[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(difok *= *\).*/\1$var_password_pam_difok/" /etc/security/pwquality.conf
else
sed -i "/\(difok *= *\).*/a difok = $var_password_pam_difok" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-26631-2
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 195. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 72. .
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.2.1.i. Set Password Strength Minimum Different Categories
The pam_pwquality module's minclass
parameter controls
requirements for usage of different character classes, or types, of character
that must exist in a password before it is considered valid. For example,
setting this value to three (3) requires that any password must have characters
from at least three different categories in order to be approved. The default
value is zero (0), meaning there are no required classes. There are four
categories available:
* Upper-case characters
* Lower-case characters
* Digits
* Special characters (for example, punctuation)
Modify the minclass
setting in /etc/security/pwquality.conf
entry to require 3
differing categories of characters when changing passwords. The minimum requirement is 3
.
Requiring a minimum number of character categories makes password guessing attacks more difficult by ensuring a larger search space.
Remediation script
var_password_pam_minclass="3"
if egrep -q ^minclass[[:space:]]*=[[:space:]]*[[:digit:]]+ /etc/security/pwquality.conf; then
sed -i "s/^\(minclass *= *\).*/\1$var_password_pam_minclass/" /etc/security/pwquality.conf
else
sed -i "/\(minclass *= *\).*/a minclass = $var_password_pam_minclass" /etc/security/pwquality.conf
fi
Security identifiers
- CCE-27115-5
References
- Test attestation on 20140626 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.3. Set Lockouts for Failed Password Attempts
The pam_faillock
PAM module provides the capability to
lock out user accounts after a number of failed login attempts. Its
documentation is available in
/usr/share/doc/pam-VERSION/txts/README.pam_faillock
.
Locking out user accounts presents the risk of a denial-of-service attack. The lockout policy must weigh whether the risk of such a denial-of-service attack outweighs the benefits of thwarting password guessing attacks.
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2.4.2.3.a. Set Deny For Failed Password Attempts
To configure the system to lock out accounts after a number of incorrect login
attempts using pam_faillock.so
, modify the content of both
/etc/pam.d/system-auth
and /etc/pam.d/password-auth
as follows:
-
add the following line immediately
before
thepam_unix.so
statement in theAUTH
section:auth required pam_faillock.so preauth silent deny=3 unlock_time=604800 fail_interval=900
-
add the following line immediately
after
thepam_unix.so
statement in theAUTH
section:auth [default=die] pam_faillock.so authfail deny=3 unlock_time=604800 fail_interval=900
-
add the following line immediately
before
thepam_unix.so
statement in theACCOUNT
section:account required pam_faillock.so
Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks.
Remediation script
var_accounts_passwords_pam_faillock_deny="3"
AUTH_FILES[0]="/etc/pam.d/system-auth"
AUTH_FILES[1]="/etc/pam.d/password-auth"
for pamFile in "${AUTH_FILES[@]}"
do
# pam_faillock.so already present?
if grep -q "^auth.*pam_faillock.so.*" $pamFile; then
# pam_faillock.so present, deny directive present?
if grep -q "^auth.*[default=die].*pam_faillock.so.*authfail.*deny=" $pamFile; then
# both pam_faillock.so & deny present, just correct deny directive value
sed -i --follow-symlink "s/\(^auth.*required.*pam_faillock.so.*preauth.*silent.*\)\(deny *= *\).*/\1\2$var_accounts_passwords_pam_faillock_deny/" $pamFile
sed -i --follow-symlink "s/\(^auth.*[default=die].*pam_faillock.so.*authfail.*\)\(deny *= *\).*/\1\2$var_accounts_passwords_pam_faillock_deny/" $pamFile
# pam_faillock.so present, but deny directive not yet
else
# append correct deny value to appropriate places
sed -i --follow-symlink "/^auth.*required.*pam_faillock.so.*preauth.*silent.*/ s/$/ deny=$var_accounts_passwords_pam_faillock_deny/" $pamFile
sed -i --follow-symlink "/^auth.*[default=die].*pam_faillock.so.*authfail.*/ s/$/ deny=$var_accounts_passwords_pam_faillock_deny/" $pamFile
fi
# pam_faillock.so not present yet
else
# insert pam_faillock.so preauth & authfail rows with proper value of the 'deny' option
sed -i --follow-symlink "/^auth.*sufficient.*pam_unix.so.*/i auth required pam_faillock.so preauth silent deny=$var_accounts_passwords_pam_faillock_deny" $pamFile
sed -i --follow-symlink "/^auth.*sufficient.*pam_unix.so.*/a auth [default=die] pam_faillock.so authfail deny=$var_accounts_passwords_pam_faillock_deny" $pamFile
sed -i --follow-symlink "/^account.*required.*pam_unix.so/i account required pam_faillock.so" $pamFile
fi
done
Security identifiers
- CCE-26891-2
References
- AC-7(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 44. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 21. .
2.4.2.3.b. Set Lockout Time For Failed Password Attempts
To configure the system to lock out accounts after a number of incorrect login
attempts and require an administrator to unlock the account using pam_faillock.so
,
modify the content of both /etc/pam.d/system-auth
and /etc/pam.d/password-auth
as follows:
-
add the following line immediately
before
thepam_unix.so
statement in theAUTH
section:auth required pam_faillock.so preauth silent deny=3 unlock_time=604800 fail_interval=900
-
add the following line immediately
after
thepam_unix.so
statement in theAUTH
section:auth [default=die] pam_faillock.so authfail deny=3 unlock_time=604800 fail_interval=900
-
add the following line immediately
before
thepam_unix.so
statement in theACCOUNT
section:account required pam_faillock.so
Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks. Ensuring that an administrator is involved in unlocking locked accounts draws appropriate attention to such situations.
Remediation script
var_accounts_passwords_pam_faillock_unlock_time="604800"
AUTH_FILES[0]="/etc/pam.d/system-auth"
AUTH_FILES[1]="/etc/pam.d/password-auth"
for pamFile in "${AUTH_FILES[@]}"
do
# pam_faillock.so already present?
if grep -q "^auth.*pam_faillock.so.*" $pamFile; then
# pam_faillock.so present, unlock_time directive present?
if grep -q "^auth.*[default=die].*pam_faillock.so.*authfail.*unlock_time=" $pamFile; then
# both pam_faillock.so & unlock_time present, just correct unlock_time directive value
sed -i --follow-symlink "s/\(^auth.*required.*pam_faillock.so.*preauth.*silent.*\)\(unlock_time *= *\).*/\1\2$var_accounts_passwords_pam_faillock_unlock_time/" $pamFile
sed -i --follow-symlink "s/\(^auth.*[default=die].*pam_faillock.so.*authfail.*\)\(unlock_time *= *\).*/\1\2$var_accounts_passwords_pam_faillock_unlock_time/" $pamFile
# pam_faillock.so present, but unlock_time directive not yet
else
# append correct unlock_time value to appropriate places
sed -i --follow-symlink "/^auth.*required.*pam_faillock.so.*preauth.*silent.*/ s/$/ unlock_time=$var_accounts_passwords_pam_faillock_unlock_time/" $pamFile
sed -i --follow-symlink "/^auth.*[default=die].*pam_faillock.so.*authfail.*/ s/$/ unlock_time=$var_accounts_passwords_pam_faillock_unlock_time/" $pamFile
fi
# pam_faillock.so not present yet
else
# insert pam_faillock.so preauth & authfail rows with proper value of the 'unlock_time' option
sed -i --follow-symlink "/^auth.*sufficient.*pam_unix.so.*/i auth required pam_faillock.so preauth silent unlock_time=$var_accounts_passwords_pam_faillock_unlock_time" $pamFile
sed -i --follow-symlink "/^auth.*sufficient.*pam_unix.so.*/a auth [default=die] pam_faillock.so authfail unlock_time=$var_accounts_passwords_pam_faillock_unlock_time" $pamFile
sed -i --follow-symlink "/^account.*required.*pam_unix.so/i account required pam_faillock.so" $pamFile
fi
done
Security identifiers
- CCE-26884-7
References
- AC-7(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 47. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.2.3.c. Set Interval For Counting Failed Password Attempts
Utilizing pam_faillock.so
, the fail_interval
directive configures the system to lock out accounts after a number of incorrect login
attempts. Modify the content of both /etc/pam.d/system-auth
and /etc/pam.d/password-auth
as follows:
-
add the following line immediately
before
thepam_unix.so
statement in theAUTH
section:auth required pam_faillock.so preauth silent deny=3 unlock_time=604800 fail_interval=900
-
add the following line immediately
after
thepam_unix.so
statement in theAUTH
section:auth [default=die] pam_faillock.so authfail deny=3 unlock_time=604800 fail_interval=900
-
add the following line immediately
before
thepam_unix.so
statement in theACCOUNT
section:account required pam_faillock.so
Locking out user accounts after a number of incorrect attempts within a specific period of time prevents direct password guessing attacks.
Security identifiers
- CCE-26763-3
References
- AC-7(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 44. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 21. .
2.4.2.3.d. Limit Password Reuse
Do not allow users to reuse recent passwords. This can
be accomplished by using the remember
option for the pam_unix
PAM
module. In the file /etc/pam.d/system-auth
, append
remember=5
to the
line which refers to the pam_unix.so
module, as shown:
password sufficient pam_unix.so existing_options remember=5
The DoD STIG requirement is 5 passwords.
Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user.
Remediation script
var_password_pam_unix_remember="5"
if grep -q "remember=" /etc/pam.d/system-auth; then
sed -i --follow-symlink "s/\(remember *= *\).*/\1$var_password_pam_unix_remember/" /etc/pam.d/system-auth
else
sed -i --follow-symlink "/^password[[:space:]]\+sufficient[[:space:]]\+pam_unix.so/ s/$/ remember=$var_password_pam_unix_remember/" /etc/pam.d/system-auth
fi
Security identifiers
- CCE-26923-3
References
- IA-5(f). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 200. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 77. .
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.4. Set Password Hashing Algorithm
The system's default algorithm for storing password hashes in
/etc/shadow
is SHA-512. This can be configured in several
locations.
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2.4.2.4.a. Set Password Hashing Algorithm in /etc/pam.d/system-auth
In /etc/pam.d/system-auth
, the password
section of
the file controls which PAM modules execute during a password change.
Set the pam_unix.so
module in the
password
section to include the argument sha512
, as shown below:
password sufficient pam_unix.so sha512 other arguments...
This will help ensure when local users change their passwords, hashes for the new
passwords will be generated using the SHA-512 algorithm.
This is the default.
Using a stronger hashing algorithm makes password cracking attacks more difficult.
Remediation script
if ! grep -q "^password.*sufficient.*pam_unix.so.*sha512" /etc/pam.d/system-auth; then
sed -i --follow-symlink "/^password.*sufficient.*pam_unix.so/ s/$/ sha512/" /etc/pam.d/system-auth
fi
Security identifiers
- CCE-27104-9
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.4.b. Set Password Hashing Algorithm in /etc/login.defs
In /etc/login.defs
, add or correct the following line to ensure
the system will use SHA-512 as the hashing algorithm:
ENCRYPT_METHOD SHA512
Using a stronger hashing algorithm makes password cracking attacks more difficult.
Remediation script
if grep --silent ^ENCRYPT_METHOD /etc/login.defs ; then
sed -i 's/^ENCRYPT_METHOD.*/ENCRYPT_METHOD SHA512/g' /etc/login.defs
else
echo "" >> /etc/login.defs
echo "ENCRYPT_METHOD SHA512" >> /etc/login.defs
fi
Security identifiers
- CCE-27124-7
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.2.4.c. Set Password Hashing Algorithm in /etc/libuser.conf
In /etc/libuser.conf
, add or correct the following line in its
[defaults]
section to ensure the system will use the SHA-512
algorithm for password hashing:
crypt_style = sha512
Using a stronger hashing algorithm makes password cracking attacks more difficult.
Security identifiers
- CCE-27053-8
References
- IA-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.3. Secure Session Configuration Files for Login Accounts
When a user logs into a Unix account, the system configures the user's session by reading a number of files. Many of these files are located in the user's home directory, and may have weak permissions as a result of user error or misconfiguration. If an attacker can modify or even read certain types of account configuration information, they can often gain full access to the affected user's account. Therefore, it is important to test and correct configuration file permissions for interactive accounts, particularly those of privileged users such as root or system administrators.
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2.4.3.a. Limit the Number of Concurrent Login Sessions Allowed Per User
Limiting the number of allowed users and sessions per user can limit risks related to Denial of
Service attacks. This addresses concurrent sessions for a single account and does not address
concurrent sessions by a single user via multiple accounts. The DoD requirement is 10. To set the number of concurrent
sessions per user add the following line in /etc/security/limits.conf
:
* hard maxlogins 1
Limiting simultaneous user logins can insulate the system from denial of service problems caused by excessive logins. Automated login processes operating improperly or maliciously may result in an exceptional number of simultaneous login sessions.
Remediation script
var_accounts_max_concurrent_login_sessions="1"
echo "* hard maxlogins $var_accounts_max_concurrent_login_sessions" >> /etc/security/limits.conf
Security identifiers
- CCE-27081-9
References
- AC-10. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 54. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 27. .
2.4.3.b. Ensure that User Home Directories are not Group-Writable or World-Readable
For each human user of the system, view the permissions of the user's home directory:
# ls -ld /home/USER
Ensure that the directory is not group-writable and that it
is not world-readable. If necessary, repair the permissions:
# chmod g-w /home/USER
# chmod o-rwx /home/USER
This action may involve modifying user home directories. Notify your user community, and solicit input if appropriate, before making this type of change.
User home directories contain many configuration files which affect the behavior of a user's account. No user should ever have write permission to another user's home directory. Group shared directories can be configured in sub-directories or elsewhere in the filesystem if they are needed. Typically, user home directories should not be world-readable, as it would disclose file names to other users. If a subset of users need read access to one another's home directories, this can be provided using groups or ACLs.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 225. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.3.3. Ensure that No Dangerous Directories Exist in Root's Path
The active path of the root account can be obtained by starting a new root shell and running:
# echo $PATH
This will produce a colon-separated list of
directories in the path.
Certain path elements could be considered dangerous, as they could lead to root executing unknown or untrusted programs, which could contain malicious code. Since root may sometimes work inside untrusted directories, the
.
character, which represents the
current directory, should never be in the root path, nor should any
directory which can be written to by an unprivileged or
semi-privileged (system) user.
It is a good practice for administrators to always execute privileged commands by typing the full path to the command.
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2.4.3.3.a. Ensure that Root's Path Does Not Include Relative Paths or Null Directories
Ensure that none of the directories in root's path is equal to a single
.
character, or
that it contains any instances that lead to relative path traversal, such as
..
or beginning a path without the slash (/
) character.
Also ensure that there are no "empty" elements in the path, such as in these examples:
PATH=:/bin
PATH=/bin:
PATH=/bin::/sbin
These empty elements have the same effect as a single .
character.
Including these entries increases the risk that root could execute code from an untrusted location.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-6(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.3.3.b. Ensure that Root's Path Does Not Include World or Group-Writable Directories
For each element in root's path, run:
# ls -ld DIR
and ensure that write permissions are disabled for group and
other.
Such entries increase the risk that root could execute code provided by unprivileged users, and potentially malicious code.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-6(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.3.4. Ensure that Users Have Sensible Umask Values
The umask setting controls the default permissions
for the creation of new files.
With a default umask
setting of 077, files and directories
created by users will not be readable by any other user on the
system. Users who wish to make specific files group- or
world-readable can accomplish this by using the chmod command.
Additionally, users can make all their files readable to their
group by default by setting a umask
of 027 in their shell
configuration files. If default per-user groups exist (that is, if
every user has a default group whose name is the same as that
user's username and whose only member is the user), then it may
even be safe for users to select a umask
of 007, making it very
easy to intentionally share files with groups of which the user is
a member.
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2.4.3.4.a. Ensure the Default Bash Umask is Set Correctly
To ensure the default umask for users of the Bash shell is set properly,
add or correct the umask
setting in /etc/bashrc
to read
as follows:
umask 027
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.
Remediation script
var_accounts_user_umask="027"
grep -q umask /etc/bashrc && \
sed -i "s/umask.*/umask $var_accounts_user_umask/g" /etc/bashrc
if ! [ $? -eq 0 ]; then
echo "umask $var_accounts_user_umask" >> /etc/bashrc
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20140912 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.3.4.b. Ensure the Default C Shell Umask is Set Correctly
To ensure the default umask for users of the C shell is set properly,
add or correct the umask
setting in /etc/csh.cshrc
to read as follows:
umask 027
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.
Remediation script
var_accounts_user_umask="027"
grep -q umask /etc/csh.cshrc && \
sed -i "s/umask.*/umask $var_accounts_user_umask/g" /etc/csh.cshrc
if ! [ $? -eq 0 ]; then
echo "umask $var_accounts_user_umask" >> /etc/csh.cshrc
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20140912 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.3.4.c. Ensure the Default Umask is Set Correctly in /etc/profile
To ensure the default umask controlled by /etc/profile
is set properly,
add or correct the umask
setting in /etc/profile
to read as follows:
umask 027
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.
Remediation script
var_accounts_user_umask="027"
grep -q umask /etc/profile && \
sed -i "s/umask.*/umask $var_accounts_user_umask/g" /etc/profile
if ! [ $? -eq 0 ]; then
echo "umask $var_accounts_user_umask" >> /etc/profile
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20120929 by swells. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.3.4.d. Ensure the Default Umask is Set Correctly in login.defs
To ensure the default umask controlled by /etc/login.defs
is set properly,
add or correct the UMASK
setting in /etc/login.defs
to read as follows:
UMASK 027
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read and written to by unauthorized users.
Remediation script
var_accounts_user_umask="027"
grep -q UMASK /etc/login.defs && \
sed -i "s/UMASK.*/UMASK $var_accounts_user_umask/g" /etc/login.defs
if ! [ $? -eq 0 ]; then
echo "UMASK $var_accounts_user_umask" >> /etc/login.defs
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20140912 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4. Protect Physical Console Access
It is impossible to fully protect a system from an attacker with physical access, so securing the space in which the system is located should be considered a necessary step. However, there are some steps which, if taken, make it more difficult for an attacker to quickly or undetectably modify a system from its console.
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2.4.4.a. Require Authentication for Single User Mode
Single-user mode is intended as a system recovery
method, providing a single user root access to the system by
providing a boot option at startup. By default, no authentication
is performed if single-user mode is selected.
By default, single-user mode is protected by requiring a password and is set
in /usr/lib/systemd/system/rescue.service
.
This prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password.
Remediation script
grep -q ^SINGLE /etc/sysconfig/init && \
sed -i "s/SINGLE.*/SINGLE=\/sbin\/sulogin/g" /etc/sysconfig/init
if ! [ $? -eq 0 ]; then
echo "SINGLE=/sbin/sulogin" >> /etc/sysconfig/init
fi
Security identifiers
- CCE-27170-0
References
- IA-2(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 213. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.b. Disable Ctrl-Alt-Del Reboot Activation
By default, the system includes the following line in
/etc/init/control-alt-delete.conf
to reboot the system when the Ctrl-Alt-Del key sequence is pressed:
exec /sbin/shutdown -r now "Control-Alt-Delete pressed"
To configure the system to log a message instead of rebooting the system, alter that line to read as follows:
exec /usr/bin/logger -p security.info "Control-Alt-Delete pressed"
A locally logged-in user who presses Ctrl-Alt-Del, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. In the GNOME graphical environment, risk of unintentional reboot from the Ctrl-Alt-Del sequence is reduced because the user will be prompted before any action is taken.
Remediation script
# The process to disable ctrl+alt+del has changed in RHEL7.
# Reference: https://access.redhat.com/solutions/1123873
ln -sf /dev/null /etc/systemd/system/ctrl-alt-del.target
Security identifiers
- CCE-RHEL7-CCE-TBD
2.4.4.c. Disable Interactive Boot
To disable the ability for users to perform interactive startups,
edit the file /etc/sysconfig/init
.
Add or correct the line:
PROMPT=no
The PROMPT
option allows the console user to perform an
interactive system startup, in which it is possible to select the
set of services which are started on boot.
Using interactive boot, the console user could disable auditing, firewalls, or other services, weakening system security.
Remediation script
grep -q ^PROMPT /etc/sysconfig/init && \
sed -i "s/PROMPT.*/PROMPT=no/g" /etc/sysconfig/init
if ! [ $? -eq 0 ]; then
echo "PROMPT=no" >> /etc/sysconfig/init
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SC-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 213. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.4. Set Boot Loader Password
During the boot process, the boot loader is responsible for starting the execution of the kernel and passing options to it. The boot loader allows for the selection of different kernels - possibly on different partitions or media. The default Red Hat Enterprise Linux boot loader for x86 systems is called GRUB2. Options it can pass to the kernel include single-user mode, which provides root access without any authentication, and the ability to disable SELinux. To prevent local users from modifying the boot parameters and endangering security, protect the boot loader configuration with a password and ensure its configuration file's permissions are set properly.
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2.4.4.4.a. Verify /boot/grub2/grub.cfg User Ownership
The file /boot/grub2/grub.cfg
should
be owned by the root
user to prevent destruction
or modification of the file.
To properly set the owner of /boot/grub2/grub.cfg
, run the command:
$ sudo chown root /boot/grub2/grub.cfg
Only root should be able to modify important boot parameters.
Remediation script
chown root /boot/grub2/grub.cfg
Security identifiers
- CCE-26860-7
References
- AC-6(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 225. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.4.b. Verify /boot/grub2/grub.cfg Group Ownership
The file /boot/grub2/grub.cfg
should
be group-owned by the root
group to prevent
destruction or modification of the file.
To properly set the group owner of /boot/grub2/grub.cfg
, run the command:
$ sudo chgrp root xsl:value-of select="@file"/>
The root
group is a highly-privileged group. Furthermore, the group-owner of this
file should not have any access privileges anyway.
Remediation script
chgrp root /boot/grub2/grub.cfg
Security identifiers
- CCE-26812-8
References
- AC-6(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 225. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.4.c. Verify /boot/grub2/grub.cfg Permissions
File permissions for /boot/grub2/grub.cfg
should be set to 600.
To properly set the permissions of /boot/grub2/grub.cfg
, run the command:
$ sudo chmod 600 /boot/grub2/grub.cfg
Proper permissions ensure that only the root user can modify important boot parameters.
Remediation script
chmod 600 /boot/grub2/grub.cfg
Security identifiers
- CCE-27054-6
References
- AC-6(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 225. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.4.d. Set Boot Loader Password
The grub2 boot loader should have a superuser account and password
protection enabled to protect boot-time settings.
To do so, select a superuser account and password and add them into the
appropriate grub2 configuration file(s) under /etc/grub.d
.
Since plaintext passwords are a security risk, generate a hash for the pasword
by running the following command:
$ grub2-mkpasswd-pbkdf2
When prompted, enter the password that was selected and insert the returned
password hash into the appropriate grub2 configuration file(s) under
/etc/grub.d
immediately after the superuser account.
(Use the output from grub2-mkpasswd-pbkdf2
as the value of
password-hash):
password_pbkdf2 superusers-accountpassword-hash
NOTE: It is recommended not to use common administrator account names like root,
admin, or administrator for the grub2 superuser account.
To meet FISMA Moderate, the bootloader superuser account and password MUST differ from the root account and password. Once the superuser account and password have been added, update the
grub.cfg
file by running:
grub2-mkconfig -o /boot/grub2/grub.cfg
NOTE: Do NOT manually add the superuser account and password to the
grub.cfg
file as the grub2-mkconfig command overwrites this file.
Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode. For more information on how to configure the grub2 superuser account and password, please refer to
-
https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sec-GRUB_2_Password_Protection.html
Security identifiers
- CCE-26809-4
References
- IA-2(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(e). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.5. Configure Screen Locking
When a user must temporarily leave an account
logged-in, screen locking should be employed to prevent passersby
from abusing the account. User education and training is
particularly important for screen locking to be effective, and policies
can be implemented to reinforce this.
Automatic screen locking is only meant as a safeguard for
those cases where a user forgot to lock the screen.
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2.4.4.5.1. Configure GUI Screen Locking
In the default GNOME3 desktop, the screen can be locked
by selecting the user name in the far right corner of the main panel and
selecting Lock.
The following sections detail commands to enforce idle activation of the screensaver,
screen locking, a blank-screen screensaver, and an idle
activation time.
Because users should be trained to lock the screen when they
step away from the computer, the automatic locking feature is only
meant as a backup.
The root account can be screen-locked; however,
the root account should never be used
to log into an X Windows environment and should only be used to
for direct login via console in emergency circumstances.
For more information about enforcing preferences in the GNOME3 environment using the DConf
configuration system, see http://wiki.gnome.org/dconf and
the man page dconf(1)
. For Red Hat specific information on configuring DConf
settings, see https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/7/html/Desktop_Migration_and_Administration_Guide/part-Configuration_and_Administration.html
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2.4.4.5.1.a. Set GNOME3 Screensaver Inactivity Timeout
To set the idle time-out value for inactivity in the GNOME3 desktop to 5 minutes (in seconds),
the idle-delay
setting must be set under an appropriate
configuration file(s) in the /etc/dconf/db/local.d
directory
and locked in /etc/dconf/db/local.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
Setting the idle delay controls when the screensaver will start, and can be combined with screen locking to prevent access from passersby.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-11(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 57. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.4.5.1.b. Enable GNOME3 Screensaver Idle Activation
To activate the screensaver in the GNOME3 desktop after a period of inactivity,
the idle-activation-enabled
setting must be set under an appropriate
configuration file(s) in the /etc/dconf/db/local.d
directory
and locked in /etc/dconf/db/local.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
Enabling idle activation of the screensaver ensures the screensaver will be activated after the idle delay. Applications requiring continuous, real-time screen display (such as network management products) require the login session does not have administrator rights and the display station is located in a controlled-access area.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-11(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 57. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.4.5.1.c. Enable GNOME3 Screensaver Lock After Idle Period
To activate locking of the screensaver in the GNOME3 desktop when it is activated,
the lock-enabled
and lock-delay
setting must be set under an appropriate
configuration file(s) in the /etc/dconf/db/local.d
directory
and locked in /etc/dconf/db/local.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
Enabling the activation of the screen lock after an idle period ensures password entry will be required in order to access the system, preventing access by passersby.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-11(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 57. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.4.5.1.d. Implement Blank Screensaver
To set the screensaver mode in the GNOME3 desktop to a blank screen,
the picture-uri
setting must be set under an appropriate
configuration file(s) in the /etc/dconf/db/local.d
directory
and locked in /etc/dconf/db/local.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
Setting the screensaver mode to blank-only conceals the contents of the display from passersby.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-11(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 60. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.4.5.2. Configure Console Screen Locking
A console screen locking mechanism is provided in the
screen
package, which is not installed by default.
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2.4.4.5.2.a. Install the screen Package
To enable console screen locking, install the screen
package:
$ sudo yum install screen
Instruct users to begin new terminal sessions with the following command:
$ screen
The console can now be locked with the following key combination:
ctrl+a x
Installing screen
ensures a console locking capability is available
for users who may need to suspend console logins.
Remediation script
yum -y install screen
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 58. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.4.4.5.3. Hardware Tokens for Authentication
The use of hardware tokens such as smart cards for system login provides stronger, two-factor authentication than using a username and password. In Red Hat Enterprise Linux servers and workstations, hardware token login is not enabled by default and must be enabled in the system settings.
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2.4.4.5.3.a. Enable Smart Card Login
To enable smart card authentication, consult the documentation at:
-
https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Managing_Smart_Cards/enabling-smart-card-login.html
For guidance on enabling SSH to authenticate against a Common Access Card (CAC), consult documentation at:
-
https://access.redhat.com/solutions/82273
Smart card login provides two-factor authentication stronger than that provided by a username and password combination. Smart cards leverage PKI (public key infrastructure) in order to provide and verify credentials.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 765. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 766. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 767. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 768. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 771. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 772. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 884. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.4.5. Warning Banners for System Accesses
Each system should expose as little information about
itself as possible.
System banners, which are typically displayed just before a
login prompt, give out information about the service or the host's
operating system. This might include the distribution name and the
system kernel version, and the particular version of a network
service. This information can assist intruders in gaining access to
the system as it can reveal whether the system is running
vulnerable software. Most network services can be configured to
limit what information is displayed.
Many organizations implement security policies that require a
system banner provide notice of the system's ownership, provide
warning to unauthorized users, and remind authorized users of their
consent to monitoring.
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2.4.5.a. Modify the System Login Banner
To configure the system login banner:
Edit /etc/issue
. Replace the default text with a message
compliant with the local site policy or a legal disclaimer.
The DoD required text is either:
You are accessing a U.S. Government (USG) Information System (IS) that is
provided for USG-authorized use only. By using this IS (which includes any
device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes
including, but not limited to, penetration testing, COMSEC monitoring, network
operations and defense, personnel misconduct (PM), law enforcement (LE), and
counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject
to routine monitoring, interception, and search, and may be disclosed or used
for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls)
to protect USG interests -- not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative
searching or monitoring of the content of privileged communications, or work
product, related to personal representation or services by attorneys,
psychotherapists, or clergy, and their assistants. Such communications and work
product are private and confidential. See User Agreement for details.
OR:
I've read & consent to terms in IS user agreem't.
An appropriate warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers.
Remediation script
login_banner_text=""
# There was a regular-expression matching various banners, needs to be expanded
expanded=$(echo "$login_banner_text" | sed 's/\[\\s\\n\][+*]/ /g;s/\\//g;s/[^-]- /\n\n-/g')
formatted=$(echo "$expanded" | fold -sw 80)
cat <<EOF >/etc/issue
$formatted
EOF
printf "\n" >> /etc/issue
Security identifiers
- CCE-27303-7
2.4.5.b. Disable the GNOME3 Login User List
In the default graphical environment, users logging
directly into the system are greeted with a login screen that displays
all known users. This functionality should be disabled.
The disable-user-list
setting must be
set under an appropriate configuration file(s) in the /etc/dconf/db/gdm.d
directory
and locked in /etc/dconf/db/gdm.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
Leaving the user list enabled is a security risk since it allows anyone with physical access to the system to quickly enumerate known user accounts without logging in.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.4.5.3. Implement a GUI Warning Banner
In the default graphical environment, users logging directly into the system are greeted with a login screen provided by the GNOME3 Display Manager (GDM). The warning banner should be displayed in this graphical environment for these users. The following sections describe how to configure the GDM login banner.
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2.4.5.3.a. Enable GNOME3 Login Warning Banner
To enable displaying a login warning banner in the GNOME
Display Manager's login screen, the banner-message-enable
setting must be
set under an appropriate configuration file(s) in the /etc/dconf/db/gdm.d
directory
and locked in /etc/dconf/db/gdm.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
To display a banner, this setting must be enabled, and the user must be prevented
from making changes. The banner text must also be set.
An appropriate warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers.
Security identifiers
- CCE-26970-4
2.4.5.3.b. Set the GNOME3 Login Warning Banner Text
To set the text shown by the GNOME3 Display Manager
in the login screen, the banner-message-text
setting must be set under an
appropriate configuration file(s) in the /etc/dconf/db/gdm.d
directory and locked
in /etc/dconf/db/gdm.d/locks
directory to prevent user modification.
After the settings have been set, run dconf update
.
When entering a warning banner that spans several lines, remember
to begin and end the string with '
and use \n
for new lines.
An appropriate warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers.
Security identifiers
- CCE-26892-0
2.5. Network Configuration and Firewalls
Most machines must be connected to a network of some
sort, and this brings with it the substantial risk of network
attack. This section discusses the security impact of decisions
about networking which must be made when configuring a system.
This section also discusses firewalls, network access
controls, and other network security frameworks, which allow
system-level rules to be written that can limit an attackers' ability
to connect to your system. These rules can specify that network
traffic should be allowed or denied from certain IP addresses,
hosts, and networks. The rules can also specify which of the
system's network services are available to particular hosts or
networks.
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2.5.a. Disable Zeroconf Networking
Zeroconf networking allows the system to assign itself an IP
address and engage in IP communication without a statically-assigned address or
even a DHCP server. Automatic address assignment via Zeroconf (or DHCP) is not
recommended. To disable Zeroconf automatic route assignment in the 169.254.0.0
subnet, add or correct the following line in /etc/sysconfig/network
:
NOZEROCONF=yes
Zeroconf addresses are in the network 169.254.0.0. The networking scripts add entries to the system's routing table for these addresses. Zeroconf address assignment commonly occurs when the system is configured to use DHCP but fails to receive an address assignment from the DHCP server.
Remediation script
echo "NOZEROCONF=yes" >> /etc/sysconfig/network
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.5.b. Ensure System is Not Acting as a Network Sniffer
The system should not be acting as a network sniffer, which can capture all traffic on the network to which it is connected. Run the following to determine if any interface is running in promiscuous mode:
$ ip link | grep PROMISC
If any results are returned, then a sniffing process (such as tcpdump or Wireshark) is likely to be using the interface and this should be investigated.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.5.3. Disable Unused Interfaces
Network interfaces expand the attack surface of the
system. Unused interfaces are not monitored or controlled, and
should be disabled.
If the system does not require network communications but still
needs to use the loopback interface, remove all files of the form
ifcfg-interface
except for ifcfg-lo
from
/etc/sysconfig/network-scripts
:
$ sudo rm /etc/sysconfig/network-scripts/ifcfg-interface
If the system is a standalone machine with no need for network access or even
communication over the loopback device, then disable this service.
The network
service can be disabled with the following command:
$ sudo systemctl disable network
2.5.4. Kernel Parameters Which Affect Networking
The sysctl
utility is used to set
parameters which affect the operation of the Linux kernel. Kernel parameters
which affect networking and have security implications are described here.
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2.5.4.1. Network Parameters for Hosts Only
If the system is not going to be used as a router, then setting certain kernel parameters ensure that the host will not perform routing of network traffic.
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2.5.4.1.a. Disable Kernel Parameter for Sending ICMP Redirects by Default
To set the runtime status of the net.ipv4.conf.default.send_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.default.send_redirects = 0
Sending ICMP redirects permits the system to instruct other systems to update their routing information. The ability to send ICMP redirects is only appropriate for systems acting as routers.
Remediation script
#
# Set runtime for net.ipv4.conf.default.send_redirects
#
sysctl -q -n -w net.ipv4.conf.default.send_redirects=0
#
# If net.ipv4.conf.default.send_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.default.send_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.default.send_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.default.send_redirects.*/net.ipv4.conf.default.send_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.default.send_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.default.send_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.1.b. Disable Kernel Parameter for Sending ICMP Redirects for All Interfaces
To set the runtime status of the net.ipv4.conf.all.send_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.all.send_redirects = 0
Sending ICMP redirects permits the system to instruct other systems to update their routing information. The ability to send ICMP redirects is only appropriate for systems acting as routers.
Remediation script
#
# Set runtime for net.ipv4.conf.all.send_redirects
#
sysctl -q -n -w net.ipv4.conf.all.send_redirects=0
#
# If net.ipv4.conf.all.send_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.all.send_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.all.send_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.all.send_redirects.*/net.ipv4.conf.all.send_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.all.send_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.send_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.1.c. Disable Kernel Parameter for IP Forwarding
To set the runtime status of the net.ipv4.ip_forward
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.ip_forward=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.ip_forward = 0
IP forwarding permits the kernel to forward packets from one network interface to another. The ability to forward packets between two networks is only appropriate for systems acting as routers.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2. Network Related Kernel Runtime Parameters for Hosts and Routers
Certain kernel parameters should be set for systems which are acting as either hosts or routers to improve the system's ability defend against certain types of IPv4 protocol attacks.
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2.5.4.2.a. Disable Kernel Parameter for Accepting Source-Routed Packets for All Interfaces
To set the runtime status of the net.ipv4.conf.all.accept_source_route
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.all.accept_source_route = 0
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
Remediation script
#
# Set runtime for net.ipv4.conf.all.accept_source_route
#
sysctl -q -n -w net.ipv4.conf.all.accept_source_route=0
#
# If net.ipv4.conf.all.accept_source_route present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.all.accept_source_route = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.all.accept_source_route /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.all.accept_source_route.*/net.ipv4.conf.all.accept_source_route = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.all.accept_source_route to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.accept_source_route = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.b. Disable Kernel Parameter for Accepting ICMP Redirects for All Interfaces
To set the runtime status of the net.ipv4.conf.all.accept_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.all.accept_redirects = 0
Accepting ICMP redirects has few legitimate uses. It should be disabled unless it is absolutely required.
Remediation script
#
# Set runtime for net.ipv4.conf.all.accept_redirects
#
sysctl -q -n -w net.ipv4.conf.all.accept_redirects=0
#
# If net.ipv4.conf.all.accept_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.all.accept_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.all.accept_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.all.accept_redirects.*/net.ipv4.conf.all.accept_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.all.accept_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.accept_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1503. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.c. Disable Kernel Parameter for Accepting Secure Redirects for All Interfaces
To set the runtime status of the net.ipv4.conf.all.secure_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.all.secure_redirects = 0
Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.
Remediation script
#
# Set runtime for net.ipv4.conf.all.secure_redirects
#
sysctl -q -n -w net.ipv4.conf.all.secure_redirects=0
#
# If net.ipv4.conf.all.secure_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.all.secure_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.all.secure_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.all.secure_redirects.*/net.ipv4.conf.all.secure_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.all.secure_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.secure_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1503. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.d. Enable Kernel Parameter to Log Martian Packets
To set the runtime status of the net.ipv4.conf.all.log_martians
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.all.log_martians=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.all.log_martians = 1
The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected.
Remediation script
#
# Set runtime for net.ipv4.conf.all.log_martians
#
sysctl -q -n -w net.ipv4.conf.all.log_martians=1
#
# If net.ipv4.conf.all.log_martians present in /etc/sysctl.conf, change value to "1"
# else, add "net.ipv4.conf.all.log_martians = 1" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.all.log_martians /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.all.log_martians.*/net.ipv4.conf.all.log_martians = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.all.log_martians to 1 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.log_martians = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.e. Disable Kernel Parameter for Accepting Source-Routed Packets By Default
To set the runtime status of the net.ipv4.conf.default.accept_source_route
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.default.accept_source_route = 0
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
Remediation script
#
# Set runtime for net.ipv4.conf.default.accept_source_route
#
sysctl -q -n -w net.ipv4.conf.default.accept_source_route=0
#
# If net.ipv4.conf.default.accept_source_route present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.default.accept_source_route = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.default.accept_source_route /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.default.accept_source_route.*/net.ipv4.conf.default.accept_source_route = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.default.accept_source_route to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.default.accept_source_route = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.f. Disable Kernel Parameter for Accepting ICMP Redirects By Default
To set the runtime status of the net.ipv4.conf.default.accept_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.default.accept_redirects = 0
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
Remediation script
#
# Set runtime for net.ipv4.conf.default.accept_redirects
#
sysctl -q -n -w net.ipv4.conf.default.accept_redirects=0
#
# If net.ipv4.conf.default.accept_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.default.accept_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.default.accept_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.default.accept_redirects.*/net.ipv4.conf.default.accept_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.default.accept_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.default.accept_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.g. Disable Kernel Parameter for Accepting Secure Redirects By Default
To set the runtime status of the net.ipv4.conf.default.secure_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.default.secure_redirects = 0
Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.
Remediation script
#
# Set runtime for net.ipv4.conf.default.secure_redirects
#
sysctl -q -n -w net.ipv4.conf.default.secure_redirects=0
#
# If net.ipv4.conf.default.secure_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv4.conf.default.secure_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.default.secure_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.default.secure_redirects.*/net.ipv4.conf.default.secure_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.default.secure_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.default.secure_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.h. Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests
To set the runtime status of the net.ipv4.icmp_echo_ignore_broadcasts
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.icmp_echo_ignore_broadcasts = 1
Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.
Remediation script
#
# Set runtime for net.ipv4.icmp_echo_ignore_broadcasts
#
sysctl -q -n -w net.ipv4.icmp_echo_ignore_broadcasts=1
#
# If net.ipv4.icmp_echo_ignore_broadcasts present in /etc/sysctl.conf, change value to "1"
# else, add "net.ipv4.icmp_echo_ignore_broadcasts = 1" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.icmp_echo_ignore_broadcasts /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.icmp_echo_ignore_broadcasts.*/net.ipv4.icmp_echo_ignore_broadcasts = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.icmp_echo_ignore_broadcasts to 1 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.icmp_echo_ignore_broadcasts = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.i. Enable Kernel Parameter to Ignore Bogus ICMP Error Responses
To set the runtime status of the net.ipv4.icmp_ignore_bogus_error_responses
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.icmp_ignore_bogus_error_responses = 1
Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged.
Remediation script
#
# Set runtime for net.ipv4.icmp_ignore_bogus_error_responses
#
sysctl -q -n -w net.ipv4.icmp_ignore_bogus_error_responses=1
#
# If net.ipv4.icmp_ignore_bogus_error_responses present in /etc/sysctl.conf, change value to "1"
# else, add "net.ipv4.icmp_ignore_bogus_error_responses = 1" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.icmp_ignore_bogus_error_responses /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.icmp_ignore_bogus_error_responses.*/net.ipv4.icmp_ignore_bogus_error_responses = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.icmp_ignore_bogus_error_responses to 1 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.icmp_ignore_bogus_error_responses = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.j. Enable Kernel Parameter to Use TCP Syncookies
To set the runtime status of the net.ipv4.tcp_syncookies
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.tcp_syncookies=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.tcp_syncookies = 1
A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected, and enables the system to continue servicing valid connection requests.
Remediation script
#
# Set runtime for net.ipv4.tcp_syncookies
#
sysctl -q -n -w net.ipv4.tcp_syncookies=1
#
# If net.ipv4.tcp_syncookies present in /etc/sysctl.conf, change value to "1"
# else, add "net.ipv4.tcp_syncookies = 1" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.tcp_syncookies /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.tcp_syncookies.*/net.ipv4.tcp_syncookies = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.tcp_syncookies to 1 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.tcp_syncookies = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
2.5.4.2.k. Enable Kernel Parameter to Use Reverse Path Filtering for All Interfaces
To set the runtime status of the net.ipv4.conf.all.rp_filter
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.all.rp_filter=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.all.rp_filter = 1
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.
Remediation script
#
# Set runtime for net.ipv4.conf.all.rp_filter
#
sysctl -q -n -w net.ipv4.conf.all.rp_filter=1
#
# If net.ipv4.conf.all.rp_filter present in /etc/sysctl.conf, change value to "1"
# else, add "net.ipv4.conf.all.rp_filter = 1" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.all.rp_filter /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.all.rp_filter.*/net.ipv4.conf.all.rp_filter = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.all.rp_filter to 1 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.rp_filter = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.4.2.l. Enable Kernel Parameter to Use Reverse Path Filtering by Default
To set the runtime status of the net.ipv4.conf.default.rp_filter
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv4.conf.default.rp_filter=1
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv4.conf.default.rp_filter = 1
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.
Remediation script
#
# Set runtime for net.ipv4.conf.default.rp_filter
#
sysctl -q -n -w net.ipv4.conf.default.rp_filter=1
#
# If net.ipv4.conf.default.rp_filter present in /etc/sysctl.conf, change value to "1"
# else, add "net.ipv4.conf.default.rp_filter = 1" to /etc/sysctl.conf
#
if grep --silent ^net.ipv4.conf.default.rp_filter /etc/sysctl.conf ; then
sed -i 's/^net.ipv4.conf.default.rp_filter.*/net.ipv4.conf.default.rp_filter = 1/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv4.conf.default.rp_filter to 1 per security requirements" >> /etc/sysctl.conf
echo "net.ipv4.conf.default.rp_filter = 1" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.5. Wireless Networking
Wireless networking, such as 802.11
(WiFi) and Bluetooth, can present a security risk to sensitive or
classified systems and networks. Wireless networking hardware is
much more likely to be included in laptop or portable systems than
in desktops or servers.
Removal of hardware provides the greatest assurance that the wireless
capability remains disabled. Acquisition policies often include provisions to
prevent the purchase of equipment that will be used in sensitive spaces and
includes wireless capabilities. If it is impractical to remove the wireless
hardware, and policy permits the device to enter sensitive spaces as long
as wireless is disabled, efforts should instead focus on disabling wireless capability
via software.
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2.5.5.1. Disable Wireless Through Software Configuration
If it is impossible to remove the wireless hardware from the device in question, disable as much of it as possible through software. The following methods can disable software support for wireless networking, but note that these methods do not prevent malicious software or careless users from re-activating the devices.
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2.5.5.1.a. Disable WiFi or Bluetooth in BIOS
Some systems that include built-in wireless support offer the ability to disable the device through the BIOS. This is system-specific; consult your hardware manual or explore the BIOS setup during boot.
Disabling wireless support in the BIOS prevents easy activation of the wireless interface, generally requiring administrators to reboot the system first.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.5.5.1.b. Deactivate Wireless Network Interfaces
Deactivating wireless network interfaces should prevent
normal usage of the wireless capability.
First, identify the interfaces available with the command:
$ ifconfig -a
Additionally, the following command may be used to
determine whether wireless support is included for a
particular interface, though this may not always be a clear
indicator:
$ iwconfig
After identifying any wireless interfaces (which may have
names like wlan0
, ath0
, wifi0
, em1
or
eth0
), deactivate the interface with the command:
$ sudo ifdown interface
These changes will only last until the next reboot. To
disable the interface for future boots, remove the appropriate
interface file from /etc/sysconfig/network-scripts
:
$ sudo rm /etc/sysconfig/network-scripts/ifcfg-interface
Wireless networking allows attackers within physical proximity to launch network-based attacks against systems, including those against local LAN protocols which were not designed with security in mind.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.5.1.c. Disable Bluetooth Service
The bluetooth
service can be disabled with the following command:
$ sudo systemctl disable bluetooth
$ sudo service bluetooth stop
Disabling the bluetooth
service prevents the system from attempting
connections to Bluetooth devices, which entails some security risk.
Nevertheless, variation in this risk decision may be expected due to the
utility of Bluetooth connectivity and its limited range.
Remediation script
#
# Disable bluetooth.service for all systemd targets
#
systemctl disable bluetooth.service
#
# Stop bluetooth.service if currently running
#
systemctl stop bluetooth.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.5.1.d. Disable Bluetooth Kernel Modules
The kernel's module loading system can be configured to prevent
loading of the Bluetooth module. Add the following to
the appropriate /etc/modprobe.d
configuration file
to prevent the loading of the Bluetooth module:
install bluetooth /bin/true
If Bluetooth functionality must be disabled, preventing the kernel from loading the kernel module provides an additional safeguard against its activation.
Remediation script
echo "install bluetooth /bin/true" > /etc/modprobe.d/bluetooth.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-18(3). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20141031 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.6. IPv6
The system includes support for Internet Protocol version 6. A major and often-mentioned improvement over IPv4 is its enormous increase in the number of available addresses. Another important feature is its support for automatic configuration of many network settings.
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2.5.6.1. Disable Support for IPv6 Unless Needed
Despite configuration that suggests support for IPv6 has been disabled, link-local IPv6 address auto-configuration occurs even when only an IPv4 address is assigned. The only way to effectively prevent execution of the IPv6 networking stack is to instruct the system not to activate the IPv6 kernel module.
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2.5.6.1.a. Disable IPv6 Networking Support Automatic Loading
To disable support for (ipv6
) add the following line to
/etc/sysctl.d/ipv6.conf
(or another file in
/etc/sysctl.d
):
net.ipv6.conf.all.disable_ipv6 = 1
This disables IPv6 on all network interfaces as other services and system
functionality require the IPv6 stack loaded to work.
Any unnecessary network stacks - including IPv6 - should be disabled, to reduce the vulnerability to exploitation.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1551. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.6.1.b. Disable Interface Usage of IPv6
To disable interface usage of IPv6, add or correct the following lines in /etc/sysconfig/network
:
NETWORKING_IPV6=no
IPV6INIT=no
Security identifiers
- CCE-RHEL7-CCE-TBD
2.5.6.1.c. Disable Support for RPC IPv6
RPC services for NFSv4 try to load transport modules for
udp6
and tcp6
by default, even if IPv6 has been disabled in
/etc/modprobe.d
. To prevent RPC services such as rpc.mountd
from attempting to start IPv6 network listeners, remove or comment out the
following two lines in /etc/netconfig
:
udp6 tpi_clts v inet6 udp - -
tcp6 tpi_cots_ord v inet6 tcp - -
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.5.6.2. Configure IPv6 Settings if Necessary
A major feature of IPv6 is the extent to which systems implementing it can automatically configure their networking devices using information from the network. From a security perspective, manually configuring important configuration information is preferable to accepting it from the network in an unauthenticated fashion.
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2.5.6.2.a. Manually Assign Global IPv6 Address
To manually assign an IP address for an interface, edit the
file /etc/sysconfig/network-scripts/ifcfg-interface
. Add or correct the
following line (substituting the correct IPv6 address):
IPV6ADDR=2001:0DB8::ABCD/64
Manually assigning an IP address is preferable to accepting one from routers or
from the network otherwise. The example address here is an IPv6 address
reserved for documentation purposes, as defined by RFC3849.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.5.6.2.b. Use Privacy Extensions for Address
To introduce randomness into the automatic generation of IPv6
addresses, add or correct the following line in
/etc/sysconfig/network-scripts/ifcfg-interface
:
IPV6_PRIVACY=rfc3041
Automatically-generated IPv6 addresses are based on the underlying hardware
(e.g. Ethernet) address, and so it becomes possible to track a piece of
hardware over its lifetime using its traffic. If it is important for a system's
IP address to not trivially reveal its hardware address, this setting should be
applied.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.5.6.2.c. Manually Assign IPv6 Router Address
Edit the file
/etc/sysconfig/network-scripts/ifcfg-interface
, and add or correct
the following line (substituting your gateway IP as appropriate):
IPV6_DEFAULTGW=2001:0DB8::0001
Router addresses should be manually set and not accepted via any
auto-configuration or router advertisement.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.5.6.2.4. Disable Automatic Configuration
Disable the system's acceptance of router
advertisements and redirects by adding or correcting the following
line in /etc/sysconfig/network
(note that this does not disable
sending router solicitations):
IPV6_AUTOCONF=no
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2.5.6.2.4.a. Disable Accepting IPv6 Router Advertisements
To set the runtime status of the net.ipv6.conf.default.accept_ra
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_ra=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv6.conf.default.accept_ra = 0
An illicit router advertisement message could result in a man-in-the-middle attack.
Remediation script
#
# Set runtime for net.ipv6.conf.default.accept_ra
#
sysctl -q -n -w net.ipv6.conf.default.accept_ra=0
#
# If net.ipv6.conf.default.accept_ra present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv6.conf.default.accept_ra = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv6.conf.default.accept_ra /etc/sysctl.conf ; then
sed -i 's/^net.ipv6.conf.default.accept_ra.*/net.ipv6.conf.default.accept_ra = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv6.conf.default.accept_ra to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv6.conf.default.accept_ra = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.5.6.2.4.b. Disable Accepting IPv6 Redirects
To set the runtime status of the net.ipv6.conf.default.accept_redirects
kernel parameter,
run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0
If this is not the system's default value, add the following line to /etc/sysctl.conf
:
net.ipv6.conf.default.accept_redirects = 0
An illicit ICMP redirect message could result in a man-in-the-middle attack.
Remediation script
#
# Set runtime for net.ipv6.conf.default.accept_redirects
#
sysctl -q -n -w net.ipv6.conf.default.accept_redirects=0
#
# If net.ipv6.conf.default.accept_redirects present in /etc/sysctl.conf, change value to "0"
# else, add "net.ipv6.conf.default.accept_redirects = 0" to /etc/sysctl.conf
#
if grep --silent ^net.ipv6.conf.default.accept_redirects /etc/sysctl.conf ; then
sed -i 's/^net.ipv6.conf.default.accept_redirects.*/net.ipv6.conf.default.accept_redirects = 0/g' /etc/sysctl.conf
else
echo -e "\n# Set net.ipv6.conf.default.accept_redirects to 0 per security requirements" >> /etc/sysctl.conf
echo "net.ipv6.conf.default.accept_redirects = 0" >> /etc/sysctl.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.5.6.2.5. Limit Network-Transmitted Configuration if Using Static IPv6 Addresses
To limit the configuration information requested from other
systems and accepted from the network on a system that uses
statically-configured IPv6 addresses, add the following lines to
/etc/sysctl.conf
:
net.ipv6.conf.default.router_solicitations = 0
net.ipv6.conf.default.accept_ra_rtr_pref = 0
net.ipv6.conf.default.accept_ra_pinfo = 0
net.ipv6.conf.default.accept_ra_defrtr = 0
net.ipv6.conf.default.autoconf = 0
net.ipv6.conf.default.dad_transmits = 0
net.ipv6.conf.default.max_addresses = 1
The router_solicitations
setting determines how many router
solicitations are sent when bringing up the interface. If addresses are
statically assigned, there is no need to send any solicitations.
The
accept_ra_pinfo
setting controls whether the system will accept
prefix info from the router.
The
accept_ra_defrtr
setting controls whether the system will accept
Hop Limit settings from a router advertisement. Setting it to 0 prevents a
router from changing your default IPv6 Hop Limit for outgoing packets.
The
autoconf
setting controls whether router advertisements can cause
the system to assign a global unicast address to an interface.
The
dad_transmits
setting determines how many neighbor solicitations
to send out per address (global and link-local) when bringing up an interface
to ensure the desired address is unique on the network.
The
max_addresses
setting determines how many global unicast IPv6
addresses can be assigned to each interface. The default is 16, but it should
be set to exactly the number of statically configured global addresses
required.
2.5.7. firewalld
The dynamic firewall daemon firewalld
provides a
dynamically managed firewall with support for network “zones” to assign
a level of trust to a network and its associated connections and interfaces.
It has support for IPv4 and IPv6 firewall settings. It supports Ethernet
bridges and has a separation of runtime and permanent configuration options.
It also has an interface for services or applications to add firewall rules
directly.
A graphical configuration tool, firewall-config
, is used to configure
firewalld
, which in turn uses iptables
tool to communicate
with Netfilter
in the kernel which implements packet filtering.
The firewall service provided by firewalld
is dynamic rather than
static because changes to the configuration can be made at anytime and are
immediately implemented. There is no need to save or apply the changes. No
unintended disruption of existing network connections occurs as no part of
the firewall has to be reloaded.
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2.5.7.1. Inspect and Activate Default firewalld Rules
Firewalls can be used to separate networks into different zones
based on the level of trust the user has decided to place on the devices and
traffic within that network. NetworkManager
informs firewalld to which
zone an interface belongs. An interface's assigned zone can be changed by
NetworkManager
or via the firewall-config
tool.
The zone settings in /etc/firewalld/
are a range of preset settings
which can be quickly applied to a network interface. These are the zones
provided by firewalld sorted according to the default trust level of the
zones from untrusted to trusted:
-
drop
Any incoming network packets are dropped, there is no reply. Only outgoing network connections are possible.
-
block
Any incoming network connections are rejected with an
icmp-host-prohibited
message for IPv4 andicmp6-adm-prohibited
for IPv6. Only network connections initiated from within the system are possible. -
public
For use in public areas. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.
-
external
For use on external networks with masquerading enabled especially for routers. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.
-
dmz
For computers in your demilitarized zone that are publicly-accessible with limited access to your internal network. Only selected incoming connections are accepted.
-
work
For use in work areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.
-
home
For use in home areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.
-
internal
For use on internal networks. You mostly trust the other computers on the networks to not harm your computer. Only selected incoming connections are accepted.
-
trusted
All network connections are accepted.
It is possible to designate one of these zones to be the default zone. When
interface connections are added to NetworkManager
, they are assigned
to the default zone. On installation, the default zone in firewalld is set to
be the public zone.
To find out all the settings of a zone, for example the public zone,
enter the following command as root:
# firewall-cmd --zone=public --list-all
Example output of this command might look like the following:
# firewall-cmd --zone=public --list-all
public
interfaces:
services: mdns dhcpv6-client ssh
ports:
forward-ports:
icmp-blocks: source-quench
To view the network zones currently active, enter the following command as root:
# firewall-cmd --get-service
The following listing displays the result of this command on common Red Hat
Enterprise Linux 7 Server system:
# firewall-cmd --get-service
amanda-client bacula bacula-client dhcp dhcpv6 dhcpv6-client dns ftp
high-availability http https imaps ipp ipp-client ipsec kerberos kpasswd
ldap ldaps libvirt libvirt-tls mdns mountd ms-wbt mysql nfs ntp openvpn
pmcd pmproxy pmwebapi pmwebapis pop3s postgresql proxy-dhcp radius rpc-bind
samba samba-client smtp ssh telnet tftp tftp-client transmission-client
vnc-server wbem-https
Finally to view the network zones that will be active after the next firewalld
service reload, enter the following command as root:
# firewall-cmd --get-service --permanent
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2.5.7.1.a. Verify firewalld Enabled
The firewalld
service can be enabled with the following command:
$ sudo systemctl enable firewalld
The dynamic firewall daemon firewalld
provides a dynamically managed
firewall with support for network “zones”, Ethernet bridges, and has a
separation of runtime and permanent configuration options. It has support for
both IPv4 and IPv6 firewall settings.
Remediation script
#
# Enable firewalld.service for all systemd targets
#
systemctl enable firewalld.service
#
# Start firewalld.service if not currently running
#
systemctl start firewalld.service
Security identifiers
- CCE-RHEL7-CCE-TBD
2.5.7.2. Strengthen the Default Ruleset
The default rules can be strengthened. The system
scripts that activate the firewall rules expect them to be defined
in configuration files under the /etc/firewalld/services
and /etc/firewalld/zones
directories.
The following recommendations describe how to strengthen the
default ruleset configuration file. An alternative to editing this
configuration file is to create a shell script that makes calls to
the firewall-cmd
program to load in rules under the /etc/firewalld/services
and /etc/firewalld/zones
directories.
Instructions apply to both unless otherwise noted. Language and address
conventions for regular firewalld rules are used throughout this section.
The program firewall-config
allows additional services to penetrate the default firewall rules
and automatically adjusts the firewalld
ruleset(s).
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2.5.7.2.a. Set Default firewalld Zone for Incoming Packets
To set the default zone to drop
for
the built-in default zone which processes incoming IPv4 and IPv6 packets,
modify the following line in
/etc/firewalld/firewalld.conf
to be:
DefaultZone=drop
In firewalld
the default zone is applied only after all
the applicable rules in the table are examined for a match. Setting the
default zone to drop
implements proper design for a firewall, i.e.
any packets which are not explicitly permitted should not be
accepted.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 66. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1109. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1154. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1414. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.5.8. Transport Layer Security Support
Support for Transport Layer Security (TLS), and its predecessor, the Secure
Sockets Layer (SSL), is included in Red Hat Enterprise Linux in the OpenSSL software (RPM package
openssl
). TLS provides encrypted and authenticated network
communications, and many network services include support for it. TLS or SSL
can be leveraged to avoid any plaintext transmission of sensitive data.
For information on how to use OpenSSL, see
http://www.openssl.org/docs/HOWTO/. Information on FIPS validation
of OpenSSL is available at http://www.openssl.org/docs/fips/fipsvalidation.html
and http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140val-all.htm.
For information on how to use and implement OpenSSL on Red Hat Enterprise Linux, see
https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/7/html/Security_Guide/sec-Using_OpenSSL.html
2.5.9. Uncommon Network Protocols
The system includes support for several network protocols which are not commonly used. Although security vulnerabilities in kernel networking code are not frequently discovered, the consequences can be dramatic. Ensuring uncommon network protocols are disabled reduces the system's risk to attacks targeted at its implementation of those protocols.
Although these protocols are not commonly used, avoid disruption in your network environment by ensuring they are not needed prior to disabling them.
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2.5.9.a. Disable DCCP Support
The Datagram Congestion Control Protocol (DCCP) is a
relatively new transport layer protocol, designed to support
streaming media and telephony.
To configure the system to prevent the dccp
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install dccp /bin/true
Disabling DCCP protects the system against exploitation of any flaws in its implementation.
Remediation script
echo "install dccp /bin/true" > /etc/modprobe.d/dccp.conf
Security identifiers
- CCE-26828-4
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.9.b. Disable SCTP Support
The Stream Control Transmission Protocol (SCTP) is a
transport layer protocol, designed to support the idea of
message-oriented communication, with several streams of messages
within one connection.
To configure the system to prevent the sctp
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install sctp /bin/true
Disabling SCTP protects the system against exploitation of any flaws in its implementation.
Remediation script
echo "install sctp /bin/true" > /etc/modprobe.d/sctp.conf
Security identifiers
- CCE-27106-4
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.9.c. Disable RDS Support
The Reliable Datagram Sockets (RDS) protocol is a transport
layer protocol designed to provide reliable high- bandwidth,
low-latency communications between nodes in a cluster.
To configure the system to prevent the rds
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install rds /bin/true
Disabling RDS protects the system against exploitation of any flaws in its implementation.
Remediation script
echo "install rds /bin/true" > /etc/modprobe.d/rds.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 382. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.9.d. Disable TIPC Support
The Transparent Inter-Process Communication (TIPC) protocol
is designed to provide communications between nodes in a
cluster.
To configure the system to prevent the tipc
kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d
:
install tipc /bin/true
Disabling TIPC protects the system against exploitation of any flaws in its implementation.
Remediation script
echo "install tipc /bin/true" > /etc/modprobe.d/tipc.conf
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 382. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.5.10. IPSec Support
Support for Internet Protocol Security (IPsec) is provided in Red Hat Enterprise Linux 7 with Libreswan.
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2.5.10.a. Install libreswan Package
The Libreswan package provides an implementation of IPsec
and IKE, which permits the creation of secure tunnels over
untrusted networks.
The libreswan
package can be installed with the following command:
$ sudo yum install libreswan
Providing the ability for remote users or systems to initiate a secure VPN connection protects information when it is transmitted over a wide area network.
Remediation script
yum -y install libreswan
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MA-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1130. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1131. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.6. Configure Syslog
The syslog service has been the default Unix logging mechanism for
many years. It has a number of downsides, including inconsistent log format,
lack of authentication for received messages, and lack of authentication,
encryption, or reliable transport for messages sent over a network. However,
due to its long history, syslog is a de facto standard which is supported by
almost all Unix applications.
In Red Hat Enterprise Linux 7, rsyslog has replaced ksyslogd as the
syslog daemon of choice, and it includes some additional security features
such as reliable, connection-oriented (i.e. TCP) transmission of logs, the
option to log to database formats, and the encryption of log data en route to
a central logging server.
This section discusses how to configure rsyslog for
best effect, and how to use tools provided with the system to maintain and
monitor logs.
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2.6.a. Ensure rsyslog is Installed
Rsyslog is installed by default.
The rsyslog
package can be installed with the following command:
$ sudo yum install rsyslog
The rsyslog package provides the rsyslog daemon, which provides system logging services.
Remediation script
yum -y install rsyslog
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-9(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1311. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1312. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.6.b. Enable rsyslog Service
The rsyslog
service provides syslog-style logging by default on Red Hat Enterprise Linux 7.
The rsyslog
service can be enabled with the following command:
$ sudo systemctl enable rsyslog
The rsyslog
service must be running in order to provide
logging services, which are essential to system administration.
Remediation script
#
# Enable rsyslog.service for all systemd targets
#
systemctl enable rsyslog.service
#
# Start rsyslog.service if not currently running
#
systemctl start rsyslog.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-12. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1557. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1312. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1311. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.6.c. Disable Logwatch on Clients if a Logserver Exists
Does your site have a central logserver which has been configured to report on logs received from all systems? If so:
$ sudo rm /etc/cron.daily/0logwatch
If no logserver exists, it will be necessary for each machine to run Logwatch individually. Using a central
logserver provides the security and reliability benefits discussed earlier, and also makes monitoring logs easier
and less time-intensive for administrators.
Security identifiers
- CCE-RHEL7-CCE-TBD
2.6.4. Ensure Proper Configuration of Log Files
The file /etc/rsyslog.conf
controls where log message are written.
These are controlled by lines called rules, which consist of a
selector and an action.
These rules are often customized depending on the role of the system, the
requirements of the environment, and whatever may enable
the administrator to most effectively make use of log data.
The default rules in Red Hat Enterprise Linux 7 are:
*.info;mail.none;authpriv.none;cron.none /var/log/messages
authpriv.* /var/log/secure
mail.* -/var/log/maillog
cron.* /var/log/cron
*.emerg *
uucp,news.crit /var/log/spooler
local7.* /var/log/boot.log
See the man page rsyslog.conf(5)
for more information.
Note that the rsyslog
daemon can be configured to use a timestamp format that
some log processing programs may not understand. If this occurs,
edit the file /etc/rsyslog.conf
and add or edit the following line:$ ActionFileDefaultTemplate RSYSLOG_TraditionalFileFormat
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2.6.4.a. Ensure Log Files Are Owned By Appropriate User
The owner of all log files written by
rsyslog
should be root.
These log files are determined by the second part of each Rule line in
/etc/rsyslog.conf
and typically all appear in /var/log
.
For each log file LOGFILE referenced in /etc/rsyslog.conf
,
run the following command to inspect the file's owner:
$ ls -l LOGFILE
If the owner is not root
, run the following command to
correct this:
$ sudo chown root LOGFILE
The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1314. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.6.4.b. Ensure Log Files Are Owned By Appropriate Group
The group-owner of all log files written by
rsyslog
should be root.
These log files are determined by the second part of each Rule line in
/etc/rsyslog.conf
and typically all appear in /var/log
.
For each log file LOGFILE referenced in /etc/rsyslog.conf
,
run the following command to inspect the file's group owner:
$ ls -l LOGFILE
If the owner is not root
, run the following command to
correct this:
$ sudo chgrp root LOGFILE
The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SI-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1314. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.6.4.c. Ensure System Log Files Have Correct Permissions
The file permissions for all log files written by
rsyslog
should be set to 600, or more restrictive.
These log files are determined by the second part of each Rule line in
/etc/rsyslog.conf
and typically all appear in /var/log
.
For each log file LOGFILE referenced in /etc/rsyslog.conf
,
run the following command to inspect the file's permissions:
$ ls -l LOGFILE
If the permissions are not 600 or more restrictive,
run the following command to correct this:
$ sudo chmod 0600 LOGFILE
Log files can contain valuable information regarding system configuration. If the system log files are not protected unauthorized users could change the logged data, eliminating their forensic value.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- SI-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1314. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.6.5. Rsyslog Logs Sent To Remote Host
If system logs are to be useful in detecting malicious
activities, it is necessary to send logs to a remote server. An
intruder who has compromised the root account on a machine may
delete the log entries which indicate that the system was attacked
before they are seen by an administrator.
However, it is recommended that logs be stored on the local
host in addition to being sent to the loghost, especially if
rsyslog
has been configured to use the UDP protocol to send
messages over a network. UDP does not guarantee reliable delivery,
and moderately busy sites will lose log messages occasionally,
especially in periods of high traffic which may be the result of an
attack. In addition, remote rsyslog
messages are not
authenticated in any way by default, so it is easy for an attacker to
introduce spurious messages to the central log server. Also, some
problems cause loss of network connectivity, which will prevent the
sending of messages to the central server. For all of these reasons, it is
better to store log messages both centrally and on each host, so
that they can be correlated if necessary.
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2.6.5.a. Ensure Logs Sent To Remote Host
To configure rsyslog to send logs to a remote log server,
open /etc/rsyslog.conf
and read and understand the last section of the file,
which describes the multiple directives necessary to activate remote
logging.
Along with these other directives, the system can be configured
to forward its logs to a particular log server by
adding or correcting one of the following lines,
substituting loghost.example.com
appropriately.
The choice of protocol depends on the environment of the system;
although TCP and RELP provide more reliable message delivery,
they may not be supported in all environments.
To use UDP for log message delivery:
*.* @loghost.example.com
To use TCP for log message delivery:
*.* @@loghost.example.com
To use RELP for log message delivery:
*.* :omrelp:loghost.example.com
A log server (loghost) receives syslog messages from one or more systems. This data can be used as an additional log source in the event a system is compromised and its local logs are suspect. Forwarding log messages to a remote loghost also provides system administrators with a centralized place to view the status of multiple hosts within the enterprise.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-3(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1348. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 136. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.6.6. Configure rsyslogd to Accept Remote Messages If Acting as a Log Server
By default, rsyslog
does not listen over the network
for log messages. If needed, modules can be enabled to allow
the rsyslog daemon to receive messages from other systems and for the system
thus to act as a log server.
If the machine is not a log server, then lines concerning these modules
should remain commented out.
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2.6.6.a. Ensure rsyslog Does Not Accept Remote Messages Unless Acting As Log Server
The rsyslog
daemon should not accept remote messages
unless the system acts as a log server.
To ensure that it is not listening on the network, ensure the following lines are
not found in /etc/rsyslog.conf
:
$ModLoad imtcp
$InputTCPServerRun port
$ModLoad imudp
$UDPServerRun port
$ModLoad imrelp
$InputRELPServerRun port
Any process which receives messages from the network incurs some risk of receiving malicious messages. This risk can be eliminated for rsyslog by configuring it not to listen on the network.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.6.6.b. Enable rsyslog to Accept Messages via TCP, if Acting As Log Server
The rsyslog
daemon should not accept remote messages
unless the system acts as a log server.
If the system needs to act as a central log server, add the following lines to
/etc/rsyslog.conf
to enable reception of messages over TCP:
$ModLoad imtcp
$InputTCPServerRun 514
If the system needs to act as a log server, this ensures that it can receive messages over a reliable TCP connection.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.6.6.c. Enable rsyslog to Accept Messages via UDP, if Acting As Log Server
The rsyslog
daemon should not accept remote messages
unless the system acts as a log server.
If the system needs to act as a central log server, add the following lines to
/etc/rsyslog.conf
to enable reception of messages over UDP:
$ModLoad imudp
$UDPServerRun 514
Many devices, such as switches, routers, and other Unix-like systems, may only support the traditional syslog transmission over UDP. If the system must act as a log server, this enables it to receive their messages as well.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.6.7. Ensure All Logs are Rotated by logrotate
Edit the file /etc/logrotate.d/syslog
. Find the first
line, which should look like this (wrapped for clarity):
/var/log/messages /var/log/secure /var/log/maillog /var/log/spooler \
/var/log/boot.log /var/log/cron {
Edit this line so that it contains a one-space-separated
listing of each log file referenced in /etc/rsyslog.conf
.
All logs in use on a system must be rotated regularly, or the log files will consume disk space over time, eventually interfering with system operation. The file
/etc/logrotate.d/syslog
is the
configuration file used by the logrotate
program to maintain all
log files written by syslog
. By default, it rotates logs weekly and
stores four archival copies of each log. These settings can be
modified by editing /etc/logrotate.conf
, but the defaults are
sufficient for purposes of this guide.
Note that
logrotate
is run nightly by the cron job
/etc/cron.daily/logrotate
. If particularly active logs need to be
rotated more often than once a day, some other mechanism must be
used.
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2.6.7.a. Ensure Logrotate Runs Periodically
The logrotate
utility allows for the automatic rotation of
log files. The frequency of rotation is specified in /etc/logrotate.conf
,
which triggers a cron task. To configure logrotate to run daily, add or correct
the following line in /etc/logrotate.conf
:
# rotate log files frequency
daily
Log files that are not properly rotated run the risk of growing so large that they fill up the /var/log partition. Valuable logging information could be lost if the /var/log partition becomes full.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
2.6.8. Configure Logwatch on the Central Log Server
Is this machine the central log server? If so, edit the file /etc/logwatch/conf/logwatch.conf
as shown below.
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2.6.8.a. Configure Logwatch HostLimit Line
On a central logserver, you want Logwatch to summarize all syslog entries, including those which did not originate
on the logserver itself. The HostLimit
setting tells Logwatch to report on all hosts, not just the one on which it
is running.
HostLimit = no
Security identifiers
- CCE-RHEL7-CCE-TBD
2.6.8.b. Configure Logwatch SplitHosts Line
If SplitHosts
is set, Logwatch will separate entries by hostname. This makes the report longer but significantly
more usable. If it is not set, then Logwatch will not report which host generated a given log entry, and that
information is almost always necessary
SplitHosts = yes
Security identifiers
- CCE-RHEL7-CCE-TBD
2.7. System Accounting with auditd
The audit service provides substantial capabilities
for recording system activities. By default, the service audits about
SELinux AVC denials and certain types of security-relevant events
such as system logins, account modifications, and authentication
events performed by programs such as sudo.
Under its default configuration, auditd
has modest disk space
requirements, and should not noticeably impact system performance.
NOTE: The Linux Audit daemon auditd
can be configured to use
the augenrules
program to read audit rules files (*.rules
)
located in /etc/audit/rules.d
location and compile them to create
the resulting form of the /etc/audit/audit.rules
configuration file
during the daemon startup (default configuration). Alternatively, the auditd
daemon can use the auditctl
utility to read audit rules from the
/etc/audit/audit.rules
configuration file during daemon startup,
and load them into the kernel. The expected behavior is configured via the
appropriate ExecStartPost
directive setting in the
/usr/lib/systemd/system/auditd.service
configuration file.
To instruct the auditd
daemon to use the augenrules
program
to read audit rules (default configuration), use the following setting:
ExecStartPost=-/sbin/augenrules --load
in the /usr/lib/systemd/system/auditd.service
configuration file.
In order to instruct the auditd
daemon to use the auditctl
utility to read audit rules, use the following setting:
ExecStartPost=-/sbin/auditctl -R /etc/audit/audit.rules
in the /usr/lib/systemd/system/auditd.service
configuration file.
Refer to [Service]
section of the /usr/lib/systemd/system/auditd.service
configuration file for further details.
Government networks often have substantial auditing requirements and
auditd
can be configured to meet these
requirements.
Examining some example audit records demonstrates how the Linux audit system
satisfies common requirements.
The following example from Fedora Documentation available at
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/SELinux_Users_and_Administrators_Guide/sect-Security-Enhanced_Linux-Troubleshooting-Fixing_Problems.html#sect-Security-Enhanced_Linux-Fixing_Problems-Raw_Audit_Messages
shows the substantial amount of information captured in a
two typical "raw" audit messages, followed by a breakdown of the most important
fields. In this example the message is SELinux-related and reports an AVC
denial (and the associated system call) that occurred when the Apache HTTP
Server attempted to access the /var/www/html/file1
file (labeled with
the samba_share_t
type):
type=AVC msg=audit(1226874073.147:96): avc: denied { getattr } for pid=2465 comm="httpd"
path="/var/www/html/file1" dev=dm-0 ino=284133 scontext=unconfined_u:system_r:httpd_t:s0
tcontext=unconfined_u:object_r:samba_share_t:s0 tclass=file
type=SYSCALL msg=audit(1226874073.147:96): arch=40000003 syscall=196 success=no exit=-13
a0=b98df198 a1=bfec85dc a2=54dff4 a3=2008171 items=0 ppid=2463 pid=2465 auid=502 uid=48
gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none) ses=6 comm="httpd"
exe="/usr/sbin/httpd" subj=unconfined_u:system_r:httpd_t:s0 key=(null)
-
msg=audit(1226874073.147:96)
-
The number in parentheses is the unformatted time stamp (Epoch time) for the event, which can be converted to standard time by using the
date
command.
-
-
{ getattr }
-
The item in braces indicates the permission that was denied.
getattr
indicates the source process was trying to read the target file's status information. This occurs before reading files. This action is denied due to the file being accessed having the wrong label. Commonly seen permissions includegetattr
,read
, andwrite
.
-
-
comm="httpd"
-
The executable that launched the process. The full path of the executable is found in the
exe=
section of the system call (SYSCALL
) message, which in this case, isexe="/usr/sbin/httpd"
.
-
-
path="/var/www/html/file1"
-
The path to the object (target) the process attempted to access.
-
-
scontext="unconfined_u:system_r:httpd_t:s0"
-
The SELinux context of the process that attempted the denied action. In this case, it is the SELinux context of the Apache HTTP Server, which is running in the
httpd_t
domain.
-
-
tcontext="unconfined_u:object_r:samba_share_t:s0"
-
The SELinux context of the object (target) the process attempted to access. In this case, it is the SELinux context of
file1
. Note: thesamba_share_t
type is not accessible to processes running in thehttpd_t
domain.
-
-
From the system call (
SYSCALL
) message, two items are of interest:success=no
: indicates whether the denial (AVC) was enforced or not.success=no
indicates the system call was not successful (SELinux denied access).success=yes
indicates the system call was successful - this can be seen for permissive domains or unconfined domains, such asinitrc_t
andkernel_t
.exe="/usr/sbin/httpd"
: the full path to the executable that launched the process, which in this case, isexe="/usr/sbin/httpd"
.
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2.7.a. Enable auditd Service
The auditd
service is an essential userspace component of
the Linux Auditing System, as it is responsible for writing audit records to
disk.
The auditd
service can be enabled with the following command:
$ sudo systemctl enable auditd
Ensuring the auditd
service is active ensures
audit records generated by the kernel can be written to disk, or that appropriate
actions will be taken if other obstacles exist.
Remediation script
#
# Enable auditd.service for all systemd targets
#
systemctl enable auditd.service
#
# Start auditd.service if not currently running
#
systemctl start auditd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-10. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 347. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 157. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 172. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 880. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1353. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1462. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1487. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1115. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1454. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 067. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 158. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 831. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1190. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1312. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1263. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 130. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 120. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1589. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.b. Enable Auditing for Processes Which Start Prior to the Audit Daemon
To ensure all processes can be audited, even those which start
prior to the audit daemon, add the argument audit=1
to the default
GRUB 2 command line for the Linux operating system in
/etc/default/grub
, in the manner below:
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=VolGroup/LogVol06 rd.lvm.lv=VolGroup/lv_swap rhgb quiet rd.shell=0 audit=1"
The GRUB 2 configuration file, grub.cfg
,
is automatically updated each time a new kernel is installed. Note that any
changes to /etc/default/grub
require rebuilding the grub.cfg
file. To update the GRUB 2 configuration file manually, use the
grub2-mkconfig -o
command as follows:
-
On BIOS-based machines, issue the following command as
root
:~]# grub2-mkconfig -o /boot/grub2/grub.cfg
-
On UEFI-based machines, issue the following command as
root
:~]# grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
Each process on the system carries an "auditable" flag which indicates whether
its activities can be audited. Although auditd
takes care of enabling
this for all processes which launch after it does, adding the kernel argument
ensures it is set for every process during boot.
Remediation script
# Correct the form of default kernel command line in /etc/default/grub
grep -q ^GRUB_CMDLINE_LINUX=\".*audit=0.*\" /etc/default/grub && \
sed -i "s/audit=[^[:space:]\+]/audit=1/g" /etc/default/grub
if ! [ $? -eq 0 ]; then
sed -i "s/\(GRUB_CMDLINE_LINUX=\)\"\(.*\)\"/\1\"\2 audit=1\"/" /etc/default/grub
fi
# Correct the form of kernel command line for each installed kernel
# in the bootloader
/sbin/grubby --update-kernel=ALL --args="audit=1"
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-14(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-10. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1464. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 130. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.3. Configure auditd Data Retention
The audit system writes data to /var/log/audit/audit.log
. By default,
auditd
rotates 5 logs by size (6MB), retaining a maximum of 30MB of
data in total, and refuses to write entries when the disk is too
full. This minimizes the risk of audit data filling its partition
and impacting other services. This also minimizes the risk of the audit
daemon temporarily disabling the system if it cannot write audit log (which
it can be configured to do).
For a busy
system or a system which is thoroughly auditing system activity, the default settings
for data retention may be
insufficient. The log file size needed will depend heavily on what types
of events are being audited. First configure auditing to log all the events of
interest. Then monitor the log size manually for awhile to determine what file
size will allow you to keep the required data for the correct time period.
Using a dedicated partition for /var/log/audit
prevents the
auditd
logs from disrupting system functionality if they fill, and,
more importantly, prevents other activity in /var
from filling the
partition and stopping the audit trail. (The audit logs are size-limited and
therefore unlikely to grow without bound unless configured to do so.) Some
machines may have requirements that no actions occur which cannot be audited.
If this is the case, then auditd
can be configured to halt the machine
if it runs out of space. Note: Since older logs are rotated,
configuring auditd
this way does not prevent older logs from being
rotated away before they can be viewed.
If your system is configured to halt when logging cannot be performed, make
sure this can never happen under normal circumstances! Ensure that
/var/log/audit
is on its own partition, and that this partition is
larger than the maximum amount of data auditd
will retain
normally.
References
link | previous | next | up | toc | home
2.7.3.a. Configure auditd Number of Logs Retained
Determine how many log files
auditd
should retain when it rotates logs.
Edit the file /etc/audit/auditd.conf
. Add or modify the following
line, substituting NUMLOGS with the correct value of 5:
num_logs = NUMLOGS
Set the value to 5 for general-purpose systems.
Note that values less than 2 result in no log rotation.
The total storage for audit log files must be large enough to retain log information over the period required. This is a function of the maximum log file size and the number of logs retained.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.3.b. Configure auditd Max Log File Size
Determine the amount of audit data (in megabytes)
which should be retained in each log file. Edit the file
/etc/audit/auditd.conf
. Add or modify the following line, substituting
the correct value of 6 for STOREMB:
max_log_file = STOREMB
Set the value to 6
(MB) or higher for general-purpose systems.
Larger values, of course,
support retention of even more audit data.
The total storage for audit log files must be large enough to retain log information over the period required. This is a function of the maximum log file size and the number of logs retained.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.3.c. Configure auditd max_log_file_action Upon Reaching Maximum Log Size
The default action to take when the logs reach their maximum size
is to rotate the log files, discarding the oldest one. To configure the action taken
by auditd
, add or correct the line in /etc/audit/auditd.conf
:
max_log_file_action = ACTION
Possible values for ACTION are described in the auditd.conf
man
page. These include:
-
ignore
-
syslog
-
suspend
-
rotate
-
keep_logs
Set the ACTION
to rotate
to ensure log rotation
occurs. This is the default. The setting is case-insensitive.
Automatically rotating logs (by setting this to rotate
)
minimizes the chances of the system unexpectedly running out of disk space by
being overwhelmed with log data. However, for systems that must never discard
log data, or which use external processes to transfer it and reclaim space,
keep_logs
can be employed.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-11. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.3.d. Configure auditd space_left Action on Low Disk Space
The auditd
service can be configured to take an action
when disk space starts to run low.
Edit the file /etc/audit/auditd.conf
. Modify the following line,
substituting ACTION appropriately:
space_left_action = ACTION
Possible values for ACTION are described in the auditd.conf
man page.
These include:
-
ignore
-
syslog
-
email
-
exec
-
suspend
-
single
-
halt
Set this to email
(instead of the default,
which is suspend
) as it is more likely to get prompt attention. Acceptable values
also include suspend
, single
, and halt
.
Notifying administrators of an impending disk space problem may allow them to take corrective action prior to any disruption.
Remediation script
var_auditd_space_left_action="email"
grep -q ^space_left_action /etc/audit/auditd.conf && \
sed -i "s/space_left_action.*/space_left_action = $var_auditd_space_left_action/g" /etc/audit/auditd.conf
if ! [ $? -eq 0 ]; then
echo "space_left_action = $var_auditd_space_left_action" >> /etc/audit/auditd.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 140. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 143. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.3.e. Configure auditd admin_space_left Action on Low Disk Space
The auditd
service can be configured to take an action
when disk space is running low but prior to running out of space completely.
Edit the file /etc/audit/auditd.conf
. Add or modify the following line,
substituting ACTION appropriately:
admin_space_left_action = ACTION
Set this value to single
to cause the system to switch to single user
mode for corrective action. Acceptable values also include suspend
and
halt
. For certain systems, the need for availability
outweighs the need to log all actions, and a different setting should be
determined. Details regarding all possible values for ACTION are described in the
auditd.conf
man page.
Administrators should be made aware of an inability to record audit records. If a separate partition or logical volume of adequate size is used, running low on space for audit records should never occur.
Remediation script
var_auditd_admin_space_left_action="single"
grep -q ^admin_space_left_action /etc/audit/auditd.conf && \
sed -i "s/admin_space_left_action.*/admin_space_left_action = $var_auditd_admin_space_left_action/g" /etc/audit/auditd.conf
if ! [ $? -eq 0 ]; then
echo "admin_space_left_action = $var_auditd_admin_space_left_action" >> /etc/audit/auditd.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-5(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 140. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1343. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.3.f. Configure auditd mail_acct Action on Low Disk Space
The auditd
service can be configured to send email to
a designated account in certain situations. Add or correct the following line
in /etc/audit/auditd.conf
to ensure that administrators are notified
via email for those situations:
action_mail_acct = root
Email sent to the root account is typically aliased to the administrators of the system, who can take appropriate action.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-5(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 139. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 144. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.3.g. Configure auditd flush priority
The auditd
service can be configured to
synchronously write audit event data to disk. Add or correct the following
line in /etc/audit/auditd.conf
to ensure that audit event data is
fully synchronized with the log files on the disk:
flush = data
Audit data should be synchronously written to disk to ensure log integrity. These parameters assure that all audit event data is fully synchronized with the log files on the disk.
Remediation script
var_auditd_flush="data"
AUDITCONFIG=/etc/audit/auditd.conf
# if flush is present, flush param edited to var_auditd_flush
# else flush param is defined by var_auditd_flush
#
# the freq param is only used value 'incremental' and will be
# commented out if flush != incremental
#
# if flush == incremental && freq param is not defined, it
# will be defined as the package-default value of 20
grep -q ^flush $AUDITCONFIG && \
sed -i 's/^flush.*/flush = '"$var_auditd_flush"'/g' $AUDITCONFIG
if ! [ $? -eq 0 ]; then
echo "flush = $var_auditd_flush" >> $AUDITCONFIG
fi
if ! [ "$var_auditd_flush" == "incremental" ]; then
sed -i 's/^freq/##freq/g' $AUDITCONFIG
elif [ "$var_auditd_flush" == "incremental" ]; then
grep -q freq $AUDITCONFIG && \
sed -i 's/^#\+freq/freq/g' $AUDITCONFIG
if ! [ $? -eq 0 ]; then
echo "freq = 20" >> $AUDITCONFIG
fi
fi
References
2.7.3.h. Configure auditd to use audispd's syslog plugin
To configure the auditd
service to use the
syslog
plug-in of the audispd
audit event multiplexor, set
the active
line in /etc/audisp/plugins.d/syslog.conf
to
yes
. Restart the auditd
service:
$ sudo service auditd restart
The auditd service does not include the ability to send audit records to a centralized server for management directly. It does, however, include a plug-in for audit event multiplexor (audispd) to pass audit records to the local syslog server
Remediation script
grep -q ^active /etc/audisp/plugins.d/syslog.conf && \
sed -i "s/active.*/active = yes/g" /etc/audisp/plugins.d/syslog.conf
if ! [ $? -eq 0 ]; then
echo "active = yes" >> /etc/audisp/plugins.d/syslog.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-3(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 136. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4. Configure auditd Rules for Comprehensive Auditing
The auditd
program can perform comprehensive
monitoring of system activity. This section describes recommended
configuration settings for comprehensive auditing, but a full
description of the auditing system's capabilities is beyond the
scope of this guide. The mailing list linux-audit@redhat.com exists
to facilitate community discussion of the auditing system.
The audit subsystem supports extensive collection of events, including:
-
Tracing of arbitrary system calls (identified by name or number) on entry or exit.
-
Filtering by PID, UID, call success, system call argument (with some limitations), etc.
-
Monitoring of specific files for modifications to the file's contents or metadata.
Auditing rules at startup are controlled by the file /etc/audit/audit.rules
.
Add rules to it to meet the auditing requirements for your organization.
Each line in /etc/audit/audit.rules
represents a series of arguments
that can be passed to auditctl
and can be individually tested
during runtime. See documentation in /usr/share/doc/audit-VERSION
and
in the related man pages for more details.
If copying any example audit rulesets from /usr/share/doc/audit-VERSION
,
be sure to comment out the
lines containing arch=
which are not appropriate for your system's
architecture. Then review and understand the following rules,
ensuring rules are activated as needed for the appropriate
architecture.
After reviewing all the rules, reading the following sections, and
editing as needed, the new rules can be activated as follows:
$ sudo service auditd restart
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2.7.4.a. Record Events that Modify User/Group Information
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following lines to a file with suffix .rules
in the
directory /etc/audit/rules.d
, in order to capture events that modify
account changes:
-w /etc/group -p wa -k audit_rules_usergroup_modification
-w /etc/passwd -p wa -k audit_rules_usergroup_modification
-w /etc/gshadow -p wa -k audit_rules_usergroup_modification
-w /etc/shadow -p wa -k audit_rules_usergroup_modification
-w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following lines to
/etc/audit/audit.rules
file, in order to capture events that modify
account changes:
-w /etc/group -p wa -k audit_rules_usergroup_modification
-w /etc/passwd -p wa -k audit_rules_usergroup_modification
-w /etc/gshadow -p wa -k audit_rules_usergroup_modification
-w /etc/shadow -p wa -k audit_rules_usergroup_modification
-w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification
In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/etc/group" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/group" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "auditctl" "/etc/passwd" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/passwd" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "auditctl" "/etc/gshadow" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/gshadow" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "auditctl" "/etc/shadow" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/shadow" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "auditctl" "/etc/security/opasswd" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/security/opasswd" "wa" "audit_rules_usergroup_modification"
Security identifiers
- CCE-27192-4
References
- AC-2(4). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 18. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 172. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1403. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1404. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1405. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1684. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1683. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1685. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1686. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 476. .
- 239. .
2.7.4.b. Record Events that Modify the System's Network Environment
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following lines to a file with suffix .rules
in the
directory /etc/audit/rules.d
, setting ARCH to either b32 or b64 as
appropriate for your system:
-a always,exit -F arch=ARCH -S sethostname -S setdomainname -k audit_rules_networkconfig_modification
-w /etc/issue -p wa -k audit_rules_networkconfig_modification
-w /etc/issue.net -p wa -k audit_rules_networkconfig_modification
-w /etc/hosts -p wa -k audit_rules_networkconfig_modification
-w /etc/sysconfig/network -p wa -k audit_rules_networkconfig_modification
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following lines to
/etc/audit/audit.rules
file, setting ARCH to either b32 or b64 as
appropriate for your system:
-a always,exit -F arch=ARCH -S sethostname -S setdomainname -k audit_rules_networkconfig_modification
-w /etc/issue -p wa -k audit_rules_networkconfig_modification
-w /etc/issue.net -p wa -k audit_rules_networkconfig_modification
-w /etc/hosts -p wa -k audit_rules_networkconfig_modification
-w /etc/sysconfig/network -p wa -k audit_rules_networkconfig_modification
The network environment should not be modified by anything other than administrator action. Any change to network parameters should be audited.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -k *"
# Use escaped BRE regex to specify rule group
GROUP="set\(host\|domain\)name"
FULL_RULE="-a always,exit -F arch=$ARCH -S sethostname -S setdomainname -k audit_rules_networkconfig_modification"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
# Then perform the remediations for the watch rules
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/etc/issue" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "augenrules" "/etc/issue" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "auditctl" "/etc/issue.net" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "augenrules" "/etc/issue.net" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "auditctl" "/etc/hosts" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "augenrules" "/etc/hosts" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "auditctl" "/etc/sysconfig/network" "wa" "audit_rules_networkconfig_modification"
fix_audit_watch_rule "augenrules" "/etc/sysconfig/network" "wa" "audit_rules_networkconfig_modification"
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.7.4.c. System Audit Logs Must Have Mode 0640 or Less Permissive
Change the mode of the audit log files with the following command:
$ sudo chmod 0640 audit_file
If users can write to audit logs, audit trails can be modified or destroyed.
Remediation script
chmod -R 640 /var/log/audit/*
chmod 640 /etc/audit/audit.rules
Security identifiers
- CCE-27004-1
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.4.d. System Audit Logs Must Be Owned By Root
To properly set the owner of /var/log
, run the command:
$ sudo chown root /var/log
Failure to give ownership of the audit log files to root allows the designated owner, and unauthorized users, potential access to sensitive information.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-9. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 166. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.4.e. Record Events that Modify the System's Mandatory Access Controls
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
:
-w /etc/selinux/ -p wa -k MAC-policy
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-w /etc/selinux/ -p wa -k MAC-policy
The system's mandatory access policy (SELinux) should not be arbitrarily changed by anything other than administrator action. All changes to MAC policy should be audited.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/etc/selinux/" "wa" "MAC-policy"
fix_audit_watch_rule "augenrules" "/etc/selinux/" "wa" "MAC-policy"
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.7.4.f. Record Attempts to Alter Logon and Logout Events
The audit system already collects login information for all users
and root. If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following lines to a file with suffix .rules
in the
directory /etc/audit/rules.d
in order to watch for attempted manual
edits of files involved in storing logon events:
-w /var/log/faillog -p wa -k logins
-w /var/log/lastlog -p wa -k logins
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following lines to
/etc/audit/audit.rules
file in order to watch for unattempted manual
edits of files involved in storing logon events:
-w /var/log/faillog -p wa -k logins
-w /var/log/lastlog -p wa -k logins
Manual editing of these files may indicate nefarious activity, such as an attacker attempting to remove evidence of an intrusion.
Security identifiers
- CCE-27204-7
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.7.4.g. Record Attempts to Alter Process and Session Initiation Information
The audit system already collects process information for all
users and root. If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following lines to a file with suffix .rules
in the
directory /etc/audit/rules.d
in order to watch for attempted manual
edits of files involved in storing such process information:
-w /var/run/utmp -p wa -k session
-w /var/log/btmp -p wa -k session
-w /var/log/wtmp -p wa -k session
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following lines to
/etc/audit/audit.rules
file in order to watch for attempted manual
edits of files involved in storing such process information:
-w /var/run/utmp -p wa -k session
-w /var/log/btmp -p wa -k session
-w /var/log/wtmp -p wa -k session
Manual editing of these files may indicate nefarious activity, such as an attacker attempting to remove evidence of an intrusion.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/var/run/utmp" "wa" "session"
fix_audit_watch_rule "augenrules" "/var/run/utmp" "wa" "session"
fix_audit_watch_rule "auditctl" "/var/log/btmp" "wa" "session"
fix_audit_watch_rule "augenrules" "/var/log/btmp" "wa" "session"
fix_audit_watch_rule "auditctl" "/var/log/wtmp" "wa" "session"
fix_audit_watch_rule "augenrules" "/var/log/wtmp" "wa" "session"
Security identifiers
- CCE-27301-1
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.7.4.h. Ensure auditd Collects Unauthorized Access Attempts to Files (unsuccessful)
At a minimum the audit system should collect unauthorized file
accesses for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following lines to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -k access
If the system is 64 bit then also add the following lines:
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -k access
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -k access
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following lines to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -k access
If the system is 64 bit then also add the following lines:
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -k access
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -k access
Unsuccessful attempts to access files could be an indicator of malicious activity on a system. Auditing these events could serve as evidence of potential system compromise.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
# First fix the -EACCES requirement
PATTERN="-a always,exit -F arch=$ARCH -S .* -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -k *"
# Use escaped BRE regex to specify rule group
GROUP="\(creat\|open\|truncate\)"
FULL_RULE="-a always,exit -F arch=$ARCH -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=4294967295 -k access"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
# Then fix the -EPERM requirement
PATTERN="-a always,exit -F arch=$ARCH -S .* -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -k *"
# No need to change content of $GROUP variable - it's the same as for -EACCES case above
FULL_RULE="-a always,exit -F arch=$ARCH -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=4294967295 -k access"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.i. Ensure auditd Collects Information on the Use of Privileged Commands
At a minimum the audit system should collect the execution of privileged commands for all users and root. To find the relevant setuid / setgid programs, run the following command for each local partition PART:
$ sudo find PART -xdev -type f -perm -4000 -o -type f -perm -2000 2>/dev/null
If the auditd
daemon is configured to use the augenrules
program to read audit rules during daemon startup (the default), add a line of
the following form to a file with suffix .rules
in the directory
/etc/audit/rules.d
for each setuid / setgid program on the system,
replacing the SETUID_PROG_PATH part with the full path of that setuid /
setgid program in the list:
-a always,exit -F path=SETUID_PROG_PATH -F perm=x -F auid>=1000 -F auid!=4294967295 -k privileged
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add a line of the following
form to /etc/audit/audit.rules
for each setuid / setgid program on the
system, replacing the SETUID_PROG_PATH part with the full path of that
setuid / setgid program in the list:
-a always,exit -F path=SETUID_PROG_PATH -F perm=x -F auid>=1000 -F auid!=4294967295 -k privileged
Privileged programs are subject to escalation-of-privilege attacks, which attempt to subvert their normal role of providing some necessary but limited capability. As such, motivation exists to monitor these programs for unusual activity.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(4). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 40. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.4.j. Ensure auditd Collects Information on Exporting to Media (successful)
At a minimum the audit system should collect media exportation
events for all users and root. If the auditd
daemon is configured to
use the augenrules
program to read audit rules during daemon startup
(the default), add the following line to a file with suffix .rules
in
the directory /etc/audit/rules.d
, setting ARCH to either b32 or b64 as
appropriate for your system:
-a always,exit -F arch=ARCH -S mount -F auid>=1000 -F auid!=4294967295 -k export
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file, setting ARCH to either b32 or b64 as
appropriate for your system:
-a always,exit -F arch=ARCH -S mount -F auid>=1000 -F auid!=4294967295 -k export
The unauthorized exportation of data to external media could result in an information leak where classified information, Privacy Act information, and intellectual property could be lost. An audit trail should be created each time a filesystem is mounted to help identify and guard against information loss.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="mount"
FULL_RULE="-a always,exit -F arch=$ARCH -S mount -F auid>=1000 -F auid!=4294967295 -k export"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.4.k. Ensure auditd Collects File Deletion Events by User
At a minimum the audit system should collect file deletion events
for all users and root. If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
, setting ARCH to either b32 or b64 as
appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=1000 -F auid!=4294967295 -k delete
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file, setting ARCH to either b32 or b64 as
appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=1000 -F auid!=4294967295 -k delete
Auditing file deletions will create an audit trail for files that are removed from the system. The audit trail could aid in system troubleshooting, as well as, detecting malicious processes that attempt to delete log files to conceal their presence.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -F auid>=1000 -F auid!=4294967295 -k *"
# Use escaped BRE regex to specify rule group
GROUP="\(rmdir\|unlink\|rename\)"
FULL_RULE="-a always,exit -F arch=$ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=1000 -F auid!=4294967295 -k delete"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-27206-2
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 172. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 468. .
2.7.4.l. Ensure auditd Collects System Administrator Actions
At a minimum the audit system should collect administrator actions
for all users and root. If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the default),
add the following line to a file with suffix .rules
in the directory
/etc/audit/rules.d
:
-w /etc/sudoers -p wa -k actions
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-w /etc/sudoers -p wa -k actions
The actions taken by system administrators should be audited to keep a record of what was executed on the system, as well as, for accountability purposes.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/etc/sudoers" "wa" "actions"
fix_audit_watch_rule "augenrules" "/etc/sudoers" "wa" "actions"
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-2(7)(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
2.7.4.m. Ensure auditd Collects Information on Kernel Module Loading and Unloading
If the auditd
daemon is configured to use the augenrules
program
to read audit rules during daemon startup (the default), add the following lines to a file
with suffix .rules
in the directory /etc/audit/rules.d
to capture kernel module
loading and unloading events, setting ARCH to either b32 or b64 as appropriate for your system:
-w /usr/sbin/insmod -p x -k modules
-w /usr/sbin/rmmod -p x -k modules
-w /usr/sbin/modprobe -p x -k modules
-a always,exit -F arch=ARCH -S init_module -S delete_module -k modules
If the auditd
daemon is configured to use the auditctl
utility to read audit
rules during daemon startup, add the following lines to /etc/audit/audit.rules
file
in order to capture kernel module loading and unloading events, setting ARCH to either b32 or
b64 as appropriate for your system:
-w /usr/sbin/insmod -p x -k modules
-w /usr/sbin/rmmod -p x -k modules
-w /usr/sbin/modprobe -p x -k modules
-a always,exit -F arch=ARCH -S init_module -S delete_module -k modules
The addition/removal of kernel modules can be used to alter the behavior of the kernel and potentially introduce malicious code into kernel space. It is important to have an audit trail of modules that have been introduced into the kernel.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
# Note: 32-bit kernel modules can't be loaded / unloaded on 64-bit kernel =>
# it's not required on a 64-bit system to check also for the presence
# of 32-bit's equivalent of the corresponding rule. Therefore for
# each system it's enought to check presence of system's native rule form.
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -k *"
# Use escaped BRE regex to specify rule group
GROUP="\(init\|delete\)_module"
FULL_RULE="-a always,exit -F arch=$ARCH -S init_module -S delete_module -k modules"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
# Then perform the remediations for the watch rules
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/usr/sbin/insmod" "x" "modules"
fix_audit_watch_rule "augenrules" "/usr/sbin/insmod" "x" "modules"
fix_audit_watch_rule "auditctl" "/usr/sbin/rmmod" "x" "modules"
fix_audit_watch_rule "augenrules" "/usr/sbin/rmmod" "x" "modules"
fix_audit_watch_rule "auditctl" "/usr/sbin/modprobe" "x" "modules"
fix_audit_watch_rule "augenrules" "/usr/sbin/modprobe" "x" "modules"
Security identifiers
- CCE-27129-6
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 172. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 477. .
2.7.4.n. Make the auditd Configuration Immutable
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
in order to make the auditd configuration
immutable:
-e 2
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file in order to make the auditd configuration
immutable:
-e 2
With this setting, a reboot will be required to change any audit rules.
Making the audit configuration immutable prevents accidental as well as malicious modification of the audit rules, although it may be problematic if legitimate changes are needed during system operation
Security identifiers
- CCE-27097-5
References
- AC-6. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
2.7.4.15. Records Events that Modify Date and Time Information
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time. All changes to the system time should be audited.
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2.7.4.15.a. Record attempts to alter time through adjtimex
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S adjtimex -k audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S adjtimex -k audit_time_rules
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S adjtimex -k audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S adjtimex -k audit_time_rules
The -k option allows for the specification of a key in string form that can be
used for better reporting capability through ausearch and aureport. Multiple
system calls can be defined on the same line to save space if desired, but is
not required. See an example of multiple combined syscalls:
-a always,exit -F arch=b64 -S adjtimex -S settimeofday -S clock_settime -k audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1487. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 169. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.15.b. Record attempts to alter time through settimeofday
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S settimeofday -k audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S settimeofday -k audit_time_rules
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S settimeofday -k audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S settimeofday -k audit_time_rules
The -k option allows for the specification of a key in string form that can be
used for better reporting capability through ausearch and aureport. Multiple
system calls can be defined on the same line to save space if desired, but is
not required. See an example of multiple combined syscalls:
-a always,exit -F arch=b64 -S adjtimex -S settimeofday -S clock_settime -k audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1487. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 169. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.15.c. Record Attempts to Alter Time Through stime
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
for both 32 bit and 64 bit systems:
-a always,exit -F arch=b32 -S stime -k audit_time_rules
Since the 64 bit version of the "stime" system call is not defined in the audit
lookup table, the corresponding "-F arch=b64" form of this rule is not expected
to be defined on 64 bit systems (the aforementioned "-F arch=b32" stime rule
form itself is sufficient for both 32 bit and 64 bit systems). If the
auditd
daemon is configured to use the auditctl
utility to
read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file for both 32 bit and 64 bit systems:
-a always,exit -F arch=b32 -S stime -k audit_time_rules
Since the 64 bit version of the "stime" system call is not defined in the audit
lookup table, the corresponding "-F arch=b64" form of this rule is not expected
to be defined on 64 bit systems (the aforementioned "-F arch=b32" stime rule
form itself is sufficient for both 32 bit and 64 bit systems). The -k option
allows for the specification of a key in string form that can be used for
better reporting capability through ausearch and aureport. Multiple system
calls can be defined on the same line to save space if desired, but is not
required. See an example of multiple combined system calls:
-a always,exit -F arch=b64 -S adjtimex -S settimeofday -S clock_settime -k audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1487. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 169. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.15.d. Record Attempts to Alter Time Through clock_settime
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the
default), add the following line to a file with suffix .rules
in the
directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S clock_settime -k audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S clock_settime -k audit_time_rules
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S clock_settime -k audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S clock_settime -k audit_time_rules
The -k option allows for the specification of a key in string form that can
be used for better reporting capability through ausearch and aureport.
Multiple system calls can be defined on the same line to save space if
desired, but is not required. See an example of multiple combined syscalls:
-a always,exit -F arch=b64 -S adjtimex -S settimeofday -S clock_settime -k audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# First perform the remediation of the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -k .*"
GROUP="clock_settime"
FULL_RULE="-a always,exit -F arch=$ARCH -S clock_settime -k audit_time_rules"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1487. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 169. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.15.e. Record Attempts to Alter the localtime File
If the auditd
daemon is configured to use the
augenrules
program to read audit rules during daemon startup (the default),
add the following line to a file with suffix .rules
in the directory
/etc/audit/rules.d
:
-w /etc/localtime -p wa -k audit_time_rules
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-w /etc/localtime -p wa -k audit_time_rules
The -k option allows for the specification of a key in string form that can
be used for better reporting capability through ausearch and aureport and
should always be used.
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_watch_rule "auditctl" "/etc/localtime" "wa" "audit_time_rules"
fix_audit_watch_rule "augenrules" "/etc/localtime" "wa" "audit_time_rules"
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1487. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 169. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16. Record Events that Modify the System's Discretionary Access Controls
At a minimum the audit system should collect file permission
changes for all users and root. Note that the "-F arch=b32" lines should be
present even on a 64 bit system. These commands identify system calls for
auditing. Even if the system is 64 bit it can still execute 32 bit system
calls. Additionally, these rules can be configured in a number of ways while
still achieving the desired effect. An example of this is that the "-S" calls
could be split up and placed on separate lines, however, this is less efficient.
Add the following to /etc/audit/audit.rules
:
-a always,exit -F arch=b32 -S chmod -S fchmod -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod
-a always,exit -F arch=b32 -S chown -S fchown -S fchownat -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
-a always,exit -F arch=b32 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If your system is 64 bit then these lines should be duplicated and the
arch=b32 replaced with arch=b64 as follows:
-a always,exit -F arch=b64 -S chmod -S fchmod -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod
-a always,exit -F arch=b64 -S chown -S fchown -S fchownat -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
-a always,exit -F arch=b64 -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
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2.7.4.16.a. Record Events that Modify the System's Discretionary Access Controls - chmod
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured to
use the augenrules
program to read audit rules during daemon startup
(the default), add the following line to a file with suffix .rules
in
the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chmod"
FULL_RULE="-a always,exit -F arch=$ARCH -S chmod -S fchmod -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.b. Record Events that Modify the System's Discretionary Access Controls - chown
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured to
use the augenrules
program to read audit rules during daemon startup
(the default), add the following line to a file with suffix .rules
in
the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=${ARCH} -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chown"
FULL_RULE="-a always,exit -F arch=${ARCH} -S chown -S fchown -S fchownat -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.c. Record Events that Modify the System's Discretionary Access Controls - fchmod
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured to
use the augenrules
program to read audit rules during daemon startup
(the default), add the following line to a file with suffix .rules
in
the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chmod"
FULL_RULE="-a always,exit -F arch=$ARCH -S chmod -S fchmod -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.d. Record Events that Modify the System's Discretionary Access Controls - fchmodat
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured to
use the augenrules
program to read audit rules during daemon startup
(the default), add the following line to a file with suffix .rules
in
the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=$ARCH -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chmod"
FULL_RULE="-a always,exit -F arch=$ARCH -S chmod -S fchmod -S fchmodat -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.e. Record Events that Modify the System's Discretionary Access Controls - fchown
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=${ARCH} -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chown"
FULL_RULE="-a always,exit -F arch=${ARCH} -S chown -S fchown -S fchownat -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.f. Record Events that Modify the System's Discretionary Access Controls - fchownat
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=${ARCH} -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chown"
FULL_RULE="-a always,exit -F arch=${ARCH} -S chown -S fchown -S fchownat -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.g. Record Events that Modify the System's Discretionary Access Controls - fremovexattr
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="xattr"
FULL_RULE="-a always,exit -F arch=${ARCH} -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.h. Record Events that Modify the System's Discretionary Access Controls - fsetxattr
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="xattr"
FULL_RULE="-a always,exit -F arch=${ARCH} -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.i. Record Events that Modify the System's Discretionary Access Controls - lchown
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit -F arch=${ARCH} -S .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="chown"
FULL_RULE="-a always,exit -F arch=${ARCH} -S chown -S fchown -S fchownat -S lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.j. Record Events that Modify the System's Discretionary Access Controls - lremovexattr
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="xattr"
FULL_RULE="-a always,exit -F arch=${ARCH} -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.k. Record Events that Modify the System's Discretionary Access Controls - lsetxattr
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="xattr"
FULL_RULE="-a always,exit -F arch=${ARCH} -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.l. Record Events that Modify the System's Discretionary Access Controls - removexattr
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="xattr"
FULL_RULE="-a always,exit -F arch=${ARCH} -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
2.7.4.16.m. Record Events that Modify the System's Discretionary Access Controls - setxattr
At a minimum the audit system should collect file permission
changes for all users and root. If the auditd
daemon is configured
to use the augenrules
program to read audit rules during daemon
startup (the default), add the following line to a file with suffix
.rules
in the directory /etc/audit/rules.d
:
-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the auditd
daemon is configured to use the auditctl
utility to read audit rules during daemon startup, add the following line to
/etc/audit/audit.rules
file:
-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=4294967295 -k perm_mod
Note that these rules can be configured in a number of ways while still achieving the desired effect. Here the system calls have been placed independent of other system calls. Grouping these system calls with others as identifying earlier in this guide is more efficient.
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Remediation script
# Include source function library.
. /usr/share/scap-security-guide/remediation_functions
# Perform the remediation for the syscall rule
# Retrieve hardware architecture of the underlying system
[ $(getconf LONG_BIT) = "32" ] && RULE_ARCHS=("b32") || RULE_ARCHS=("b32" "b64")
for ARCH in "${RULE_ARCHS[@]}"
do
PATTERN="-a always,exit .* -F auid>=1000 -F auid!=4294967295 -k *"
GROUP="xattr"
FULL_RULE="-a always,exit -F arch=${ARCH} -S setxattr -S lsetxattr -S fsetxattr -S removexattr -S lremovexattr -S fremovexattr -F auid>=1000 -F auid!=4294967295 -k perm_mod"
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
fix_audit_syscall_rule "auditctl" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
fix_audit_syscall_rule "augenrules" "$PATTERN" "$GROUP" "$ARCH" "$FULL_RULE"
done
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-1(b). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-2(d). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(a). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-12(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IR-5. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
3. Services
The best protection against vulnerable software is running less software. This section describes how to review
the software which Red Hat Enterprise Linux 7 installs on a system and disable software which is not needed. It
then enumerates the software packages installed on a default Red Hat Enterprise Linux 7 system and provides guidance about which
ones can be safely disabled.
Red Hat Enterprise Linux 7 provides a convenient minimal install option that essentially installs the bare necessities for a functional
system. When building Red Hat Enterprise Linux 7 servers, it is highly recommended to select the minimal packages and then build up
the system from there.
Table of Contents
- 3.1. Obsolete Services
-
3.2. Base Services
- 3.2.a. Disable Automatic Bug Reporting Tool (abrtd)
- 3.2.b. Disable Advanced Configuration and Power Interface (acpid)
- 3.2.c. Disable Certmonger Service (certmonger)
- 3.2.d. Disable Control Group Config (cgconfig)
- 3.2.e. Disable Control Group Rules Engine (cgred)
- 3.2.f. Disable CPU Speed (cpuspeed)
- 3.2.g. Enable IRQ Balance (irqbalance)
- 3.2.h. Disable KDump Kernel Crash Analyzer (kdump)
- 3.2.i. Disable Software RAID Monitor (mdmonitor)
- 3.2.j. Disable D-Bus IPC Service (messagebus)
- 3.2.k. Disable Network Console (netconsole)
- 3.2.l. Disable ntpdate Service (ntpdate)
- 3.2.m. Disable Odd Job Daemon (oddjobd)
- 3.2.n. Disable Portreserve (portreserve)
- 3.2.o. Enable Process Accounting (psacct)
- 3.2.p. Disable Apache Qpid (qpidd)
- 3.2.q. Disable Quota Netlink (quota_nld)
- 3.2.r. Disable Network Router Discovery Daemon (rdisc)
- 3.2.s. Disable Red Hat Network Service (rhnsd)
- 3.2.t. Disable Red Hat Subscription Manager Daemon (rhsmcertd)
- 3.2.u. Disable Cyrus SASL Authentication Daemon (saslauthd)
- 3.2.v. Disable SMART Disk Monitoring Service (smartd)
- 3.2.w. Disable System Statistics Reset Service (sysstat)
- 3.3. Cron and At Daemons
-
3.4. SSH Server
- 3.4.a. Disable SSH Server If Possible (Unusual)
- 3.4.b. Remove SSH Server firewalld Firewall exception (Unusual)
-
3.4.3. Configure OpenSSH Server if Necessary
- 3.4.3.a. Allow Only SSH Protocol 2
- 3.4.3.b. Limit Users' SSH Access
- 3.4.3.c. Set SSH Idle Timeout Interval
- 3.4.3.d. Set SSH Client Alive Count
- 3.4.3.e. Disable SSH Support for .rhosts Files
- 3.4.3.f. Disable Host-Based Authentication
- 3.4.3.g. Disable SSH Root Login
- 3.4.3.h. Disable SSH Access via Empty Passwords
- 3.4.3.j. Do Not Allow SSH Environment Options
- 3.4.3.k. Use Only Approved Ciphers
- 3.4.3.l. Use Only Approved MACs
- 3.4.3.13. Strengthen Firewall Configuration if Possible
- 3.5. X Window System
- 3.6. Avahi Server
- 3.7. Print Support
- 3.8. DHCP
- 3.9. Network Time Protocol
-
3.10. Mail Server Software
- 3.10.a. Enable Postfix Service
- 3.10.b. Uninstall Sendmail Package
- 3.10.3. Configure SMTP For Mail Clients
- 3.10.4. Configure Operating System to Protect Mail Server
- 3.11. LDAP
-
3.12. NFS and RPC
- 3.12.1. Disable All NFS Services if Possible
- 3.12.2. Configure All Machines which Use NFS
- 3.12.3. Configure NFS Clients
-
3.12.4. Configure NFS Servers
- 3.12.4.a. Use Root-Squashing on All Exports
- 3.12.4.b. Restrict NFS Clients to Privileged Ports
- 3.12.4.c. Ensure Insecure File Locking is Not Allowed
- 3.12.4.4. Configure the Exports File Restrictively
- 3.12.4.5. Use Access Lists to Enforce Authorization Restrictions
- 3.12.4.6. Export Filesystems Read-Only if Possible
- 3.13. DNS Server
-
3.14. FTP Server
- 3.14.1. Disable vsftpd if Possible
- 3.14.2. Use vsftpd to Provide FTP Service if Necessary
- 3.14.3. Use vsftpd to Provide FTP Service if Necessary
-
3.15. Web Server
- 3.15.1. Disable Apache if Possible
- 3.15.2. Install Apache if Necessary
-
3.15.3. Secure Apache Configuration
- 3.15.3.1. Restrict Web Server Information Leakage
-
3.15.3.2. Minimize Web Server Loadable Modules
-
3.15.3.2.1. httpd Core Modules
- 3.15.3.2.1.a. Disable HTTP Digest Authentication
- 3.15.3.2.1.b. Disable HTTP mod_rewrite
- 3.15.3.2.1.c. Disable LDAP Support
- 3.15.3.2.1.d. Disable Server Side Includes
- 3.15.3.2.1.e. Disable MIME Magic
- 3.15.3.2.1.f. Disable WebDAV (Distributed Authoring and Versioning)
- 3.15.3.2.1.g. Disable Server Activity Status
- 3.15.3.2.1.h. Disable Web Server Configuration Display
- 3.15.3.2.1.i. Disable URL Correction on Misspelled Entries
- 3.15.3.2.1.j. Disable Proxy Support
- 3.15.3.2.1.k. Disable Cache Support
- 3.15.3.2.1.l. Disable CGI Support
- 3.15.3.2.1.13. Minimize Modules for HTTP Basic Authentication
- 3.15.3.2.1.14. Minimize Various Optional Components
- 3.15.3.2.1.15. Minimize Configuration Files Included
-
3.15.3.2.1. httpd Core Modules
- 3.15.3.3. Directory Restrictions
- 3.15.3.4. Use Appropriate Modules to Improve httpd's Security
- 3.15.3.5. Use Denial-of-Service Protection Modules
- 3.15.3.6. Configure PHP Securely
- 3.15.3.7. Configure Operating System to Protect Web Server
- 3.16. IMAP and POP3 Server
- 3.17. Samba(SMB) Microsoft Windows File Sharing Server
- 3.18. Proxy Server
- 3.19. SNMP Server
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3.1. Obsolete Services
This section discusses a number of network-visible
services which have historically caused problems for system
security, and for which disabling or severely limiting the service
has been the best available guidance for some time. As a result of
this, many of these services are not installed as part of Red Hat Enterprise Linux 7
by default.
Organizations which are running these services should
switch to more secure equivalents as soon as possible.
If it remains absolutely necessary to run one of
these services for legacy reasons, care should be taken to restrict
the service as much as possible, for instance by configuring host
firewall software such as firewalld
to restrict access to the
vulnerable service to only those remote hosts which have a known
need to use it.
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3.1.1. Xinetd
The xinetd
service acts as a dedicated listener for some
network services (mostly, obsolete ones) and can be used to provide access
controls and perform some logging. It has been largely obsoleted by other
features, and it is not installed by default. The older Inetd service
is not even available as part of Red Hat Enterprise Linux 7.
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3.1.1.a. Disable xinetd Service
The xinetd
service can be disabled with the following command:
$ sudo systemctl disable xinetd
The xinetd service provides a dedicated listener service for some programs, which is no longer necessary for commonly-used network services. Disabling it ensures that these uncommon services are not running, and also prevents attacks against xinetd itself.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 305. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.1.b. Uninstall xinetd Package
The xinetd
package can be uninstalled with the following command:
$ sudo yum erase xinetd
Removing the xinetd
package decreases the risk of the
xinetd service's accidental (or intentional) activation.
Remediation script
if rpm -qa | grep -q xinetd; then
yum -y remove xinetd
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 305. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.2. Telnet
The telnet protocol does not provide confidentiality or integrity for information transmitted on the network. This includes authentication information such as passwords. Organizations which use telnet should be actively working to migrate to a more secure protocol.
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3.1.2.a. Disable telnet Service
The telnet
service configuration file /etc/xinetd.d/telnet
is not created automatically. If it was created manually, check the
/etc/xinetd.d/telnet
file and ensure that disable = no
is changed to read disable = yes
as follows below:
# description: The telnet server serves telnet sessions; it uses \\
# unencrypted username/password pairs for authentication.
service telnet
{
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID
disable = yes
}
Then the activation of the telnet
service on system boot can be disabled
via the following command:
# systemctl disable telnet.socket
The telnet protocol uses unencrypted network communication, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network. The telnet protocol is also subject to man-in-the-middle attacks.
Security identifiers
- CCE-27158-5
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20140922 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.2.b. Uninstall telnet-server Package
The telnet-server
package can be uninstalled with
the following command:
$ sudo yum erase telnet-server
Removing the telnet-server
package decreases the risk of the
telnet service's accidental (or intentional) activation.
Remediation script
if rpm -qa | grep -q telnet-server; then
yum -y remove telnet-server
fi
Security identifiers
- CCE-27165-0
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.2.c. Remove telnet Clients
The telnet client allows users to start connections to other systems via the telnet protocol.
The telnet
protocol is insecure and unencrypted. The use
of an unencrypted transmission medium could allow an unauthorized user
to steal credentials. The ssh
package provides an
encrypted session and stronger security and is included in Red Hat
Enterprise Linux.
Remediation script
yum -y remove telnet
Security identifiers
- CCE-27039-7
3.1.3. Rlogin, Rsh, and Rexec
The Berkeley r-commands are legacy services which allow cleartext remote access and have an insecure trust model.
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3.1.3.a. Uninstall rsh-server Package
The rsh-server
package can be uninstalled with
the following command:
$ sudo yum erase rsh-server
The rsh-server
package provides several obsolete and insecure
network services. Removing it
decreases the risk of those services' accidental (or intentional)
activation.
Remediation script
yum -y erase rsh-server
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 305. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 381. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.3.b. Disable rexec Service
The rexec
service, which is available with
the rsh-server
package and runs as a service through xinetd,
should be disabled.
The rexec
service can be disabled with the following command:
$ sudo systemctl disable rexec
The rexec service uses unencrypted network communications, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 68. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1436. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.3.c. Disable rsh Service
The rsh
service, which is available with
the rsh-server
package and runs as a service through xinetd,
should be disabled.
The rsh
service can be disabled with the following command:
$ sudo systemctl disable rsh
The rsh service uses unencrypted network communications, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 68. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1436. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.3.d. Uninstal rsh Package
The rsh
package contains the client commands
for the rsh services
These legacy clients contain numerous security exposures and have
been replaced with the more secure SSH package. Even if the server is removed,
it is best to ensure the clients are also removed to prevent users from
inadvertently attempting to use these commands and therefore exposing
their credentials. Note that removing the rsh
package removes
the clients for rsh
,rcp
, and rlogin
.
Security identifiers
- CCE-
References
- Test attestation on 20140530 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.3.e. Disable rlogin Service
The rlogin
service, which is available with
the rsh-server
package and runs as a service through xinetd,
should be disabled.
The rlogin
service can be disabled with the following command:
$ sudo systemctl disable rlogin
The rlogin service uses unencrypted network communications, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1436. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.3.f. Remove Rsh Trust Files
The files /etc/hosts.equiv
and ~/.rhosts
(in
each user's home directory) list remote hosts and users that are trusted by the
local system when using the rshd daemon.
To remove these files, run the following command to delete them from any
location:
$ sudo rm /etc/hosts.equiv
$ rm ~/.rhosts
Trust files are convenient, but when used in conjunction with the R-services, they can allow unauthenticated access to a system.
Remediation script
find -type f -name .rhosts -exec rm -f '{}' \;
rm /etc/hosts.equiv
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1436. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.4. NIS
The Network Information Service (NIS), also known as 'Yellow Pages' (YP), and its successor NIS+ have been made obsolete by Kerberos, LDAP, and other modern centralized authentication services. NIS should not be used because it suffers from security problems inherent in its design, such as inadequate protection of important authentication information.
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3.1.4.a. Uninstall ypserv Package
The ypserv
package can be uninstalled with
the following command:
$ sudo yum erase ypserv
Removing the ypserv
package decreases the risk of the
accidental (or intentional) activation of NIS or NIS+ services.
Remediation script
if rpm -qa | grep -q ypserv; then
yum -y remove ypserv
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 305. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 381. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.4.b. Disable ypbind Service
The ypbind
service, which allows the system to act as a client in
a NIS or NIS+ domain, should be disabled.
The ypbind
service can be disabled with the following command:
$ sudo systemctl disable ypbind
Disabling the ypbind
service ensures the system is not acting
as a client in a NIS or NIS+ domain.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 305. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.4.c. Remove NIS Client
The Network Information Service (NIS), formerly known as Yellow Pages,
is a client-server directory service protocol used to distribute system configuration
files. The NIS client (ypbind
) was used to bind a machine to an NIS server
and receive the distributed configuration files.
The NIS service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that the service be removed.
Security identifiers
- CCE-
3.1.5. TFTP Server
TFTP is a lightweight version of the FTP protocol which has traditionally been used to configure networking equipment. However, TFTP provides little security, and modern versions of networking operating systems frequently support configuration via SSH or other more secure protocols. A TFTP server should be run only if no more secure method of supporting existing equipment can be found.
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3.1.5.a. Disable tftp Service
The tftp
service should be disabled.
The tftp
service can be disabled with the following command:
$ sudo systemctl disable tftp
Disabling the tftp
service ensures the system is not acting
as a TFTP server, which does not provide encryption or authentication.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 1436. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.5.b. Uninstall tftp-server Package
The tftp-server
package can be removed with the following command:
$ sudo yum erase tftp-server
Removing the tftp-server
package decreases the risk of the
accidental (or intentional) activation of tftp services.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 305. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121026 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.5.c. Remove tftp
Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol,
typically used to automatically transfer configuration or boot files between machines.
TFTP does not support authentication and can be easily hacked. The package
tftp
is a client program that allows for connections to a tftp
server.
It is recommended that TFTP be remvoed, unless there is a specific need for TFTP (such as a boot server). In that case, use extreme caution when configuring the services.
Security identifiers
- CCE-
3.1.5.d. Ensure tftp Daemon Uses Secure Mode
If running the tftp
service is necessary, it should be configured
to change its root directory at startup. To do so, ensure
/etc/xinetd.d/tftp
includes -s
as a command line argument, as shown in
the following example (which is also the default):
server_args = -s /var/lib/tftpboot
Using the -s
option causes the TFTP service to only serve files from the
given directory. Serving files from an intentionally-specified directory
reduces the risk of sharing files which should remain private.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.1.6. Chat/Messaging Services
The talk software makes it possible for users to send and receive messages across systems through a terminal session.
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3.1.6.a. Uninstall talk-server Package
The talk-server
package can be removed with the following command:
$ sudo yum erase talk-server
The talk software presents a security risk as it uses unencrypted protocols
for communications. Removing the talk-server
package decreases the
risk of the accidental (or intentional) activation of talk services.
Security identifiers
- CCE-
References
- Test attestation on 20140625 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.1.6.b. Uninstall talk Package
The talk
package contains the client program for the
Internet talk protocol, which allows the user to chat with other users on
different systems. Talk is a communication program which copies lines from one
terminal to the terminal of another user.
The talk software presents a security risk as it uses unencrypted protocols
for communications. Removing the talk
package decreases the
risk of the accidental (or intentional) activation of talk client program.
Security identifiers
- CCE-
References
- Test attestation on 20140625 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2. Base Services
This section addresses the base services that are installed on a Red Hat Enterprise Linux 7 default installation which are not covered in other sections. Some of these services listen on the network and should be treated with particular discretion. Other services are local system utilities that may or may not be extraneous. In general, system services should be disabled if not required.
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3.2.a. Disable Automatic Bug Reporting Tool (abrtd)
The Automatic Bug Reporting Tool (abrtd
) daemon collects
and reports crash data when an application crash is detected. Using a variety
of plugins, abrtd can email crash reports to system administrators, log crash
reports to files, or forward crash reports to a centralized issue tracking
system such as RHTSupport.
The abrtd
service can be disabled with the following command:
$ sudo systemctl disable abrtd
Mishandling crash data could expose sensitive information about vulnerabilities in software executing on the local machine, as well as sensitive information from within a process's address space or registers.
Remediation script
#
# Disable abrtd.service for all systemd targets
#
systemctl disable abrtd.service
#
# Stop abrtd.service if currently running
#
systemctl stop abrtd.service
Security identifiers
- CCE-26872-2
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20140921 by JL. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.b. Disable Advanced Configuration and Power Interface (acpid)
The Advanced Configuration and Power Interface Daemon (acpid
)
dispatches ACPI events (such as power/reset button depressed) to userspace
programs.
The acpid
service can be disabled with the following command:
$ sudo systemctl disable acpid
ACPI support is highly desirable for systems in some network roles, such as laptops or desktops. For other systems, such as servers, it may permit accidental or trivially achievable denial of service situations and disabling it is appropriate.
Remediation script
#
# Disable acpid.service for all systemd targets
#
systemctl disable acpid.service
#
# Stop acpid.service if currently running
#
systemctl stop acpid.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.c. Disable Certmonger Service (certmonger)
Certmonger is a D-Bus based service that attempts to simplify interaction
with certifying authorities on networks which use public-key infrastructure. It is often
combined with Red Hat's IPA (Identity Policy Audit) security information management
solution to aid in the management of certificates.
The certmonger
service can be disabled with the following command:
$ sudo systemctl disable certmonger
The services provided by certmonger may be essential for systems fulfilling some roles a PKI infrastructure, but its functionality is not necessary for many other use cases.
Remediation script
#
# Disable certmonger.service for all systemd targets
#
systemctl disable certmonger.service
#
# Stop certmonger.service if currently running
#
systemctl stop certmonger.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.d. Disable Control Group Config (cgconfig)
Control groups allow an administrator to allocate system resources (such as CPU,
memory, network bandwidth, etc) among a defined group (or groups) of processes executing on
a system. The cgconfig
daemon starts at boot and establishes the predefined control groups.
The cgconfig
service can be disabled with the following command:
$ sudo systemctl disable cgconfig
Unless control groups are used to manage system resources, running the cgconfig service is not necessary.
Remediation script
#
# Disable cgconfig.service for all systemd targets
#
systemctl disable cgconfig.service
#
# Stop cgconfig.service if currently running
#
systemctl stop cgconfig.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.e. Disable Control Group Rules Engine (cgred)
The cgred
service moves tasks into control groups according to
parameters set in the /etc/cgrules.conf
configuration file.
The cgred
service can be disabled with the following command:
$ sudo systemctl disable cgred
Unless control groups are used to manage system resources, running the cgred service service is not necessary.
Remediation script
#
# Disable cgred.service for all systemd targets
#
systemctl disable cgred.service
#
# Stop cgred.service if currently running
#
systemctl stop cgred.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.f. Disable CPU Speed (cpuspeed)
The cpuspeed
service can adjust the clock speed of supported CPUs based upon
the current processing load thereby conserving power and reducing heat.
The cpuspeed
service can be disabled with the following command:
$ sudo systemctl disable cpuspeed
The cpuspeed
service is only necessary if adjusting the CPU clock speed
provides benefit. Traditionally this has included laptops (to enhance battery life),
but may also apply to server or desktop environments where conserving power is
highly desirable or necessary.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.g. Enable IRQ Balance (irqbalance)
The irqbalance
service optimizes the balance between
power savings and performance through distribution of hardware interrupts across
multiple processors.
The irqbalance
service can be enabled with the following command:
$ sudo systemctl enable irqbalance
In an environment with multiple processors (now common), the irqbalance service provides potential speedups for handling interrupt requests.
Remediation script
#
# Enable irqbalance.service for all systemd targets
#
systemctl enable irqbalance.service
#
# Start irqbalance.service if not currently running
#
systemctl start irqbalance.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.h. Disable KDump Kernel Crash Analyzer (kdump)
The kdump
service provides a kernel crash dump analyzer. It uses the kexec
system call to boot a secondary kernel ("capture" kernel) following a system
crash, which can load information from the crashed kernel for analysis.
The kdump
service can be disabled with the following command:
$ sudo systemctl disable kdump
Unless the system is used for kernel development or testing, there is little need to run the kdump service.
Remediation script
#
# Disable kdump.service for all systemd targets
#
systemctl disable kdump.service
#
# Stop kdump.service if currently running
#
systemctl stop kdump.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.i. Disable Software RAID Monitor (mdmonitor)
The mdmonitor
service is used for monitoring a software RAID array; hardware
RAID setups do not use this service.
The mdmonitor
service can be disabled with the following command:
$ sudo systemctl disable mdmonitor
If software RAID monitoring is not required, there is no need to run this service.
Remediation script
#
# Disable mdmonitor.service for all systemd targets
#
systemctl disable mdmonitor.service
#
# Stop mdmonitor.service if currently running
#
systemctl stop mdmonitor.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.j. Disable D-Bus IPC Service (messagebus)
D-Bus provides an IPC mechanism used by
a growing list of programs, such as those used for Gnome, Bluetooth, and Avahi.
Due to these dependencies, disabling D-Bus may not be practical for
many systems.
The messagebus
service can be disabled with the following command:
$ sudo systemctl disable messagebus
If no services which require D-Bus are needed, then it can be disabled. As a broker for IPC between processes of different privilege levels, it could be a target for attack. However, disabling D-Bus is likely to be impractical for any system which needs to provide a graphical login session.
Remediation script
#
# Disable messagebus.service for all systemd targets
#
systemctl disable messagebus.service
#
# Stop messagebus.service if currently running
#
systemctl stop messagebus.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.k. Disable Network Console (netconsole)
The netconsole
service is responsible for loading the
netconsole kernel module, which logs kernel printk messages over UDP to a
syslog server. This allows debugging of problems where disk logging fails and
serial consoles are impractical.
The netconsole
service can be disabled with the following command:
$ sudo systemctl disable netconsole
The netconsole
service is not necessary unless there is a need to debug
kernel panics, which is not common.
Remediation script
#
# Disable netconsole for all run levels
#
chkconfig --level 0123456 netconsole off
#
# Stop netconsole if currently running
#
service netconsole stop
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.l. Disable ntpdate Service (ntpdate)
The ntpdate
service sets the local hardware clock by polling NTP servers
when the system boots. It synchronizes to the NTP servers listed in
/etc/ntp/step-tickers
or /etc/ntp.conf
and then sets the local hardware clock to the newly synchronized
system time.
The ntpdate
service can be disabled with the following command:
$ sudo systemctl disable ntpdate
The ntpdate
service may only be suitable for systems which
are rebooted frequently enough that clock drift does not cause problems between
reboots. In any event, the functionality of the ntpdate service is now
available in the ntpd program and should be considered deprecated.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 382. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.m. Disable Odd Job Daemon (oddjobd)
The oddjobd
service exists to provide an interface and
access control mechanism through which
specified privileged tasks can run tasks for unprivileged client
applications. Communication with oddjobd
through the system message bus.
The oddjobd
service can be disabled with the following command:
$ sudo systemctl disable oddjobd
The oddjobd
service may provide necessary functionality in
some environments, and can be disabled if it is not needed. Execution of
tasks by privileged programs, on behalf of unprivileged ones, has traditionally
been a source of privilege escalation security issues.
Remediation script
#
# Disable oddjobd.service for all systemd targets
#
systemctl disable oddjobd.service
#
# Stop oddjobd.service if currently running
#
systemctl stop oddjobd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 381. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.n. Disable Portreserve (portreserve)
The portreserve
service is a TCP port reservation utility that can
be used to prevent portmap from binding to well known TCP ports that are
required for other services.
The portreserve
service can be disabled with the following command:
$ sudo systemctl disable portreserve
The portreserve
service provides helpful functionality by
preventing conflicting usage of ports in the reserved port range, but it can be
disabled if not needed.
Remediation script
#
# Disable portreserve.service for all systemd targets
#
systemctl disable portreserve.service
#
# Stop portreserve.service if currently running
#
systemctl stop portreserve.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.o. Enable Process Accounting (psacct)
The process accounting service, psacct
, works with programs
including acct
and ac
to allow system administrators to view
user activity, such as commands issued by users of the system.
The psacct
service can be enabled with the following command:
$ sudo systemctl enable psacct
The psacct
service can provide administrators a convenient
view into some user activities. However, it should be noted that the auditing
system and its audit records provide more authoritative and comprehensive
records.
Remediation script
#
# Enable psacct.service for all systemd targets
#
systemctl enable psacct.service
#
# Start psacct.service if not currently running
#
systemctl start psacct.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-12. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.p. Disable Apache Qpid (qpidd)
The qpidd
service provides high speed, secure,
guaranteed delivery services. It is an implementation of the Advanced Message
Queuing Protocol. By default the qpidd service will bind to port 5672 and
listen for connection attempts.
The qpidd
service can be disabled with the following command:
$ sudo systemctl disable qpidd
The qpidd service is automatically installed when the "base"
package selection is selected during installation. The qpidd service listens
for network connections, which increases the attack surface of the system. If
the system is not intended to receive AMQP traffic, then the qpidd
service is not needed and should be disabled or removed.
Remediation script
#
# Disable qpidd.service for all systemd targets
#
systemctl disable qpidd.service
#
# Stop qpidd.service if currently running
#
systemctl stop qpidd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.2.q. Disable Quota Netlink (quota_nld)
The quota_nld
service provides notifications to
users of disk space quota violations. It listens to the kernel via a netlink
socket for disk quota violations and notifies the appropriate user of the
violation using D-Bus or by sending a message to the terminal that the user has
last accessed.
The quota_nld
service can be disabled with the following command:
$ sudo systemctl disable quota_nld
If disk quotas are enforced on the local system, then the
quota_nld
service likely provides useful functionality and should
remain enabled. However, if disk quotas are not used or user notification of
disk quota violation is not desired then there is no need to run this
service.
Remediation script
#
# Disable quota_nld.service for all systemd targets
#
systemctl disable quota_nld.service
#
# Stop quota_nld.service if currently running
#
systemctl stop quota_nld.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.r. Disable Network Router Discovery Daemon (rdisc)
The rdisc
service implements the client side of the ICMP
Internet Router Discovery Protocol (IRDP), which allows discovery of routers on
the local subnet. If a router is discovered then the local routing table is
updated with a corresponding default route. By default this daemon is disabled.
The rdisc
service can be disabled with the following command:
$ sudo systemctl disable rdisc
General-purpose systems typically have their network and routing information configured statically by a system administrator. Workstations or some special-purpose systems often use DHCP (instead of IRDP) to retrieve dynamic network configuration information.
Remediation script
#
# Disable rdisc.service for all systemd targets
#
systemctl disable rdisc.service
#
# Stop rdisc.service if currently running
#
systemctl stop rdisc.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-4. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 382. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.s. Disable Red Hat Network Service (rhnsd)
The Red Hat Network service automatically queries Red Hat Network
servers to determine whether there are any actions that should be executed,
such as package updates. This only occurs if the system was registered to an
RHN server or satellite and managed as such.
The rhnsd
service can be disabled with the following command:
$ sudo systemctl disable rhnsd
Although systems management and patching is extremely important to
system security, management by a system outside the enterprise enclave is not
desirable for some environments. However, if the system is being managed by RHN or
RHN Satellite Server the rhnsd
daemon can remain on.
Remediation script
#
# Disable rhnsd for all run levels
#
chkconfig --level 0123456 rhnsd off
#
# Stop rhnsd if currently running
#
service rhnsd stop
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 382. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.t. Disable Red Hat Subscription Manager Daemon (rhsmcertd)
The Red Hat Subscription Manager (rhsmcertd) periodically checks for
changes in the entitlement certificates for a registered system and updates it
accordingly.
The rhsmcertd
service can be disabled with the following command:
$ sudo systemctl disable rhsmcertd
The rhsmcertd
service can provide administrators with some
additional control over which of their systems are entitled to particular
subscriptions. However, for systems that are managed locally or which are not
expected to require remote changes to their subscription status, it is
unnecessary and can be disabled.
Remediation script
#
# Disable rhsmcertd.service for all systemd targets
#
systemctl disable rhsmcertd.service
#
# Stop rhsmcertd.service if currently running
#
systemctl stop rhsmcertd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.u. Disable Cyrus SASL Authentication Daemon (saslauthd)
The saslauthd
service handles plaintext authentication requests on
behalf of the SASL library. The service isolates all code requiring superuser
privileges for SASL authentication into a single process, and can also be used
to provide proxy authentication services to clients that do not understand SASL
based authentication.
The saslauthd
service can be disabled with the following command:
$ sudo systemctl disable saslauthd
The saslauthd
service provides essential functionality for
performing authentication in some directory environments, such as those which
use Kerberos and LDAP. For others, however, in which only local files may be
consulted, it is not necessary and should be disabled.
Remediation script
#
# Disable saslauthd.service for all systemd targets
#
systemctl disable saslauthd.service
#
# Stop saslauthd.service if currently running
#
systemctl stop saslauthd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-17(8). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.v. Disable SMART Disk Monitoring Service (smartd)
SMART (Self-Monitoring, Analysis, and Reporting Technology) is a
feature of hard drives that allows them to detect symptoms of disk failure and
relay an appropriate warning.
The smartd
service can be disabled with the following command:
$ sudo systemctl disable smartd
SMART can help protect against denial of service due to failing hardware. Nevertheless, if it is not needed or the system's drives are not SMART-capable (such as solid state drives), it can be disabled.
Remediation script
#
# Disable smartd.service for all systemd targets
#
systemctl disable smartd.service
#
# Stop smartd.service if currently running
#
systemctl stop smartd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.2.w. Disable System Statistics Reset Service (sysstat)
The sysstat
service resets various I/O and CPU
performance statistics to zero in order to begin counting from a fresh state
at boot time.
The sysstat
service can be disabled with the following command:
$ sudo systemctl disable sysstat
By default the sysstat
service merely runs a program at
boot to reset the statistics, which can be retrieved using programs such as
sar
and sadc
. These may provide useful insight into system
operation, but unless used this service can be disabled.
Remediation script
#
# Disable sysstat.service for all systemd targets
#
systemctl disable sysstat.service
#
# Stop sysstat.service if currently running
#
systemctl stop sysstat.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.3. Cron and At Daemons
The cron and at services are used to allow commands to be executed at a later time. The cron service is required by almost all systems to perform necessary maintenance tasks, while at may or may not be required on a given system. Both daemons should be configured defensively.
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3.3.a. Enable cron Service
The crond
service is used to execute commands at
preconfigured times. It is required by almost all systems to perform necessary
maintenance tasks, such as notifying root of system activity.
The crond
service can be enabled with the following command:
$ sudo systemctl enable crond
Due to its usage for maintenance and security-supporting tasks, enabling the cron daemon is essential.
Remediation script
#
# Enable crond.service for all systemd targets
#
systemctl enable crond.service
#
# Start crond.service if not currently running
#
systemctl start crond.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.3.b. Disable anacron Service
The cronie-anacron
package, which provides anacron
functionality, is installed by default.
The cronie-anacron
package can be removed with the following command:
$ sudo yum erase cronie-anacron
The anacron
service provides cron
functionality for systems
such as laptops and workstations that may be shut down during the normal times
that cron
jobs are scheduled to run. On systems which do not require this
additional functionality, anacron
could needlessly increase the possible
attack surface for an intruder.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.3.c. Disable At Service (atd)
The at
and batch
commands can be used to
schedule tasks that are meant to be executed only once. This allows delayed
execution in a manner similar to cron, except that it is not
recurring. The daemon atd
keeps track of tasks scheduled via
at
and batch
, and executes them at the specified time.
The atd
service can be disabled with the following command:
$ sudo systemctl disable atd
The atd
service could be used by an unsophisticated insider to carry
out activities outside of a normal login session, which could complicate
accountability. Furthermore, the need to schedule tasks with at
or
batch
is not common.
Remediation script
#
# Disable atd.service for all systemd targets
#
systemctl disable atd.service
#
# Stop atd.service if currently running
#
systemctl stop atd.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.3.4. Restrict at and cron to Authorized Users if Necessary
The /etc/cron.allow
and /etc/at.allow
files contain lists of users who are allowed
to use cron and at to delay execution of processes. If these files exist and
if the corresponding files /etc/cron.deny
and /etc/at.deny
do not exist,
then only users listed in the relevant allow files can run the crontab and at
commands to submit jobs to be run at scheduled intervals.
On many systems, only the system administrator needs the ability to schedule
jobs. Note that even if a given user is not listed in cron.allow
, cron jobs can
still be run as that user. The cron.allow
file controls only administrative access
to the crontab command for scheduling and modifying cron jobs.
To restrict at and cron to only authorized users:
-
Remove the cron.deny file:
$ sudo rm /etc/cron.deny
-
Edit
/etc/cron.allow
, adding one line for each user allowed to use the crontab command to create cron jobs. -
Remove the
at.deny
file:$ sudo rm /etc/at.deny
-
Edit
/etc/at.allow
, adding one line for each user allowed to use the at command to create at jobs.
3.4. SSH Server
The SSH protocol is recommended for remote login and
remote file transfer. SSH provides confidentiality and integrity
for data exchanged between two systems, as well as server
authentication, through the use of public key cryptography. The
implementation included with the system is called OpenSSH, and more
detailed documentation is available from its website,
http://www.openssh.org. Its server program is called sshd
and
provided by the RPM package openssh-server
.
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3.4.a. Disable SSH Server If Possible (Unusual)
The SSH server service, sshd, is commonly needed.
However, if it can be disabled, do so.
The sshd
service can be disabled with the following command:
$ sudo systemctl disable sshd
This is unusual, as SSH is a common method for encrypted and authenticated
remote access.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.b. Remove SSH Server firewalld Firewall exception (Unusual)
By default, inbound connections to SSH's port are allowed. If
the SSH server is not being used, this exception should be removed from the
firewall configuration.
To configure firewalld
to not allow access, run the following command(s):
If inbound SSH connections are not expected, disallowing access to the SSH port will avoid possible exploitation of the port by an attacker.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.4.3. Configure OpenSSH Server if Necessary
If the system needs to act as an SSH server, then
certain changes should be made to the OpenSSH daemon configuration
file /etc/ssh/sshd_config
. The following recommendations can be
applied to this file. See the sshd_config(5)
man page for more
detailed information.
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3.4.3.a. Allow Only SSH Protocol 2
Only SSH protocol version 2 connections should be
permitted. The default setting in
/etc/ssh/sshd_config
is correct, and can be
verified by ensuring that the following
line appears:
Protocol 2
SSH protocol version 1 suffers from design flaws that result in security vulnerabilities and should not be used.
Remediation script
grep -qi ^Protocol /etc/ssh/sshd_config && \
sed -i "s/Protocol.*/Protocol 2/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "Protocol 2" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-27038-9
References
- AC-17(7). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.b. Limit Users' SSH Access
By default, the SSH configuration allows any user with an account
to access the system. In order to specify the users that are allowed to login
via SSH and deny all other users, add or correct the following line in the
/etc/ssh/sshd_config
file:
DenyUsers USER1 USER2
Where USER1
and USER2
are valid user names.
Specifying which accounts are allowed SSH access into the system reduces the possibility of unauthorized access to the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.4.3.c. Set SSH Idle Timeout Interval
SSH allows administrators to set an idle timeout
interval.
After this interval has passed, the idle user will be
automatically logged out.
To set an idle timeout interval, edit the following line in /etc/ssh/sshd_config
as
follows:
ClientAliveInterval interval
The timeout interval is given in seconds. To have a timeout
of 15 minutes, set interval to 900.
If a shorter timeout has already been set for the login shell, that value will preempt any SSH setting made here. Keep in mind that some processes may stop SSH from correctly detecting that the user is idle.
Causing idle users to be automatically logged out guards against compromises one system leading trivially to compromises on another.
Remediation script
sshd_idle_timeout_value="300"
grep -qi ^ClientAliveInterval /etc/ssh/sshd_config && \
sed -i "s/ClientAliveInterval.*/ClientAliveInterval $sshd_idle_timeout_value/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "ClientAliveInterval $sshd_idle_timeout_value" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-26611-4
References
- AC-2(5). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.d. Set SSH Client Alive Count
To ensure the SSH idle timeout occurs precisely when the ClientAliveCountMax
is set,
edit /etc/ssh/sshd_config
as
follows:
ClientAliveCountMax 0
This ensures a user login will be terminated as soon as the ClientAliveCountMax
is reached.
Remediation script
grep -qi ^ClientAliveCountMax /etc/ssh/sshd_config && \
sed -i "s/ClientAliveCountMax.*/ClientAliveCountMax 0/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "ClientAliveCountMax 0" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-27066-0
References
- AC-2(5). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SA-8. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.e. Disable SSH Support for .rhosts Files
SSH can emulate the behavior of the obsolete rsh
command in allowing users to enable insecure access to their
accounts via .rhosts
files.
To ensure this behavior is disabled, add or correct the
following line in /etc/ssh/sshd_config
:
IgnoreRhosts yes
SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.
Remediation script
grep -qi ^IgnoreRhosts /etc/ssh/sshd_config && \
sed -i "s/IgnoreRhosts.*/IgnoreRhosts yes/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "IgnoreRhosts yes" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-27035-5
References
3.4.3.f. Disable Host-Based Authentication
SSH's cryptographic host-based authentication is
more secure than .rhosts
authentication. However, it is
not recommended that hosts unilaterally trust one another, even
within an organization.
To disable host-based authentication, add or correct the
following line in /etc/ssh/sshd_config
:
HostbasedAuthentication no
SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.
Remediation script
grep -q ^HostbasedAuthentication /etc/ssh/sshd_config && \
sed -i "s/HostbasedAuthentication.*/HostbasedAuthentication no/g" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "HostbasedAuthentication no" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-26870-6
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.g. Disable SSH Root Login
The root user should never be allowed to login to a
system directly over a network.
To disable root login via SSH, add or correct the following line
in /etc/ssh/sshd_config
:
PermitRootLogin no
Permitting direct root login reduces auditable information about who ran privileged commands on the system and also allows direct attack attempts on root's password.
Remediation script
SSHD_CONFIG='/etc/ssh/sshd_config'
# Obtain line number of first uncommented case-insensitive occurrence of Match
# block directive (possibly prefixed with whitespace) present in $SSHD_CONFIG
FIRST_MATCH_BLOCK=$(sed -n '/^[[:space:]]*Match[^\n]*/I{=;q}' $SSHD_CONFIG)
# Obtain line number of first uncommented case-insensitive occurence of
# PermitRootLogin directive (possibly prefixed with whitespace) present in
# $SSHD_CONFIG
FIRST_PERMIT_ROOT_LOGIN=$(sed -n '/^[[:space:]]*PermitRootLogin[^\n]*/I{=;q}' $SSHD_CONFIG)
# Case: Match block directive not present in $SSHD_CONFIG
if [ -z "$FIRST_MATCH_BLOCK" ]
then
# Case: PermitRootLogin directive not present in $SSHD_CONFIG yet
if [ -z "$FIRST_PERMIT_ROOT_LOGIN" ]
then
# Append 'PermitRootLogin no' at the end of $SSHD_CONFIG
echo -e "\nPermitRootLogin no" >> $SSHD_CONFIG
# Case: PermitRootLogin directive present in $SSHD_CONFIG already
else
# Replace first uncommented case-insensitive occurrence
# of PermitRootLogin directive
sed -i "$FIRST_PERMIT_ROOT_LOGIN s/^[[:space:]]*PermitRootLogin.*$/PermitRootLogin no/I" $SSHD_CONFIG
fi
# Case: Match block directive present in $SSHD_CONFIG
else
# Case: PermitRootLogin directive not present in $SSHD_CONFIG yet
if [ -z "$FIRST_PERMIT_ROOT_LOGIN" ]
then
# Prepend 'PermitRootLogin no' before first uncommented
# case-insensitive occurrence of Match block directive
sed -i "$FIRST_MATCH_BLOCK s/^\([[:space:]]*Match[^\n]*\)/PermitRootLogin no\n\1/I" $SSHD_CONFIG
# Case: PermitRootLogin directive present in $SSHD_CONFIG and placed
# before first Match block directive
elif [ "$FIRST_PERMIT_ROOT_LOGIN" -lt "$FIRST_MATCH_BLOCK" ]
then
# Replace first uncommented case-insensitive occurrence
# of PermitRootLogin directive
sed -i "$FIRST_PERMIT_ROOT_LOGIN s/^[[:space:]]*PermitRootLogin.*$/PermitRootLogin no/I" $SSHD_CONFIG
# Case: PermitRootLogin directive present in $SSHD_CONFIG and placed
# after first Match block directive
else
# Prepend 'PermitRootLogin no' before first uncommented
# case-insensitive occurrence of Match block directive
sed -i "$FIRST_MATCH_BLOCK s/^\([[:space:]]*Match[^\n]*\)/PermitRootLogin no\n\1/I" $SSHD_CONFIG
fi
fi
Security identifiers
- CCE-26946-4
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-6(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-2(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.h. Disable SSH Access via Empty Passwords
To explicitly disallow remote login from accounts with
empty passwords, add or correct the following line in
/etc/ssh/sshd_config
:
PermitEmptyPasswords no
Any accounts with empty passwords should be disabled immediately, and PAM configuration
should prevent users from being able to assign themselves empty passwords.
Configuring this setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere.
Remediation script
grep -qi ^PermitEmptyPasswords /etc/ssh/sshd_config && \
sed -i "s/PermitEmptyPasswords.*/PermitEmptyPasswords no/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "PermitEmptyPasswords no" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-26864-9
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.i. Enable SSH Warning Banner
To enable the warning banner and ensure it is consistent
across the system, add or correct the following line in /etc/ssh/sshd_config
:
Banner /etc/issue
Another section contains information on how to create an
appropriate system-wide warning banner.
The warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution.
Remediation script
grep -qi ^Banner /etc/ssh/sshd_config && \
sed -i "s/Banner.*/Banner \/etc\/issue/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "" >> /etc/ssh/sshd_config
echo "Banner /etc/issue" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-27314-4
3.4.3.j. Do Not Allow SSH Environment Options
To ensure users are not able to present
environment options to the SSH daemon, add or correct the following line
in /etc/ssh/sshd_config
:
PermitUserEnvironment no
SSH environment options potentially allow users to bypass access restriction in some configurations.
Remediation script
grep -qi ^PermitUserEnvironment /etc/ssh/sshd_config && \
sed -i "s/PermitUserEnvironment.*/PermitUserEnvironment no/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "PermitUserEnvironment no" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-26974-6
References
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.k. Use Only Approved Ciphers
Limit the ciphers to those algorithms which are FIPS-approved.
Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode.
The following line in /etc/ssh/sshd_config
demonstrates use of FIPS-approved ciphers:
Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
The man page sshd_config(5)
contains a list of supported ciphers.
Approved algorithms should impart some level of confidence in their implementation. These are also required for compliance.
Remediation script
grep -qi ^Ciphers /etc/ssh/sshd_config && \
sed -i "s/Ciphers.*/Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc" >> /etc/ssh/sshd_config
fi
Security identifiers
- CCE-27051-2
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AC-17(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- AU-10(5). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-5(1)(c). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- . URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.4.3.l. Use Only Approved MACs
Limit the MACs to those hash algorithms which are FIPS-approved.
The following line in /etc/ssh/sshd_config
demonstrates use of FIPS-approved MACs:
MACs hmac-sha2-512,hmac-sha2-256,hmac-sha1
The man page sshd_config(5)
contains a list of supported MACs.
Approved algorithms should impart some level of confidence in their implementation. These are also required for compliance.
Remediation script
grep -qi ^MACs /etc/ssh/sshd_config && \
sed -i "s/MACs.*/MACs hmac-sha2-512,hmac-sha2-256,hmac-sha1/gI" /etc/ssh/sshd_config
if ! [ $? -eq 0 ]; then
echo "MACs hmac-sha2-512,hmac-sha2-256,hmac-sha1" >> /etc/ssh/sshd_config
fi
References
- AC-17(2). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- IA-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- SC-13. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 68. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1453. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 803. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 2449. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 2450. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 61. .
- 223. .
3.4.3.13. Strengthen Firewall Configuration if Possible
If the SSH server is expected to only receive connections from
the local network, then strengthen the default firewall rule for the SSH service
to only accept connections from the appropriate network segment(s).
Determine an appropriate network block, netwk
, network mask, mask
, and
network protocol, ip_protocol
, representing the machines on your network which will
be allowed to access this SSH server.
Run the following command:
firewall-cmd --permanent --add-rich-rule='rule family="ip_protocol" source address="netwk/mask" service name="ssh" accept'
Restricting SSH access to only trusted network segments reduces exposure of the SSH server to attacks from unauthorized networks.
3.5. X Window System
The X Window System implementation included with the system is called X.org.
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3.5.1. Disable X Windows
Unless there is a mission-critical reason for the system to run a graphical user interface, ensure X is not set to start automatically at boot and remove the X Windows software packages. There is usually no reason to run X Windows on a dedicated server machine, as it increases the system's attack surface and consumes system resources. Administrators of server systems should instead login via SSH or on the text console.
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3.5.1.a. Disable X Windows Startup By Setting Default Target
Setting the system's default target to multi-user will prevent automatic startup of the X server. To do so, run:
$ systemctl set-default multi-user.target
You should see the following output:
rm '/etc/systemd/system/default.target'
ln -s '/usr/lib/systemd/system/multi-user.target' '/etc/systemd/system/default.target'
Unnecessary services should be disabled to decrease the attack surface of the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AC-3. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.5.1.b. Remove the X Windows Package Group
Removing all packages which constitute the X Window System ensures users or malicious software cannot start X. To do so, run the following command:
$ sudo yum groupremove "X Window System"
Unnecessary packages should not be installed to decrease the attack surface of the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.6. Avahi Server
The Avahi daemon implements the DNS Service Discovery and Multicast DNS protocols, which provide service and host discovery on a network. It allows a system to automatically identify resources on the network, such as printers or web servers. This capability is also known as mDNSresponder and is a major part of Zeroconf networking.
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3.6.1. Disable Avahi Server if Possible
Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Disabling it can reduce the system's vulnerability to such attacks.
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3.6.1.a. Disable Avahi Server Software
The avahi-daemon
service can be disabled with the following command:
$ sudo systemctl disable avahi-daemon
Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Its functionality is convenient but is only appropriate if the local network can be trusted.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.6.2. Configure Avahi if Necessary
If your system requires the Avahi daemon, its configuration can be restricted
to improve security. The Avahi daemon configuration file is
/etc/avahi/avahi-daemon.conf
. The following security recommendations
should be applied to this file:
See the avahi-daemon.conf(5)
man page, or documentation at
http://www.avahi.org, for more detailed information about the configuration options.
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3.6.2.a. Serve Avahi Only via Required Protocol
If you are using only IPv4, edit /etc/avahi/avahi-daemon.conf
and ensure
the following line exists in the [server]
section:
use-ipv6=no
Similarly, if you are using only IPv6, disable IPv4 sockets with the line:
use-ipv4=no
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.6.2.b. Check Avahi Responses' TTL Field
To make Avahi ignore packets unless the TTL field is 255, edit
/etc/avahi/avahi-daemon.conf
and ensure the following line
appears in the [server]
section:
check-response-ttl=yes
This helps to ensure that only mDNS responses from the local network are processed, because the TTL field in a packet is decremented from its initial value of 255 whenever it is routed from one network to another. Although a properly-configured router or firewall should not allow mDNS packets into the local network at all, this option provides another check to ensure they are not permitted.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.6.2.c. Prevent Other Programs from Using Avahi's Port
To prevent other mDNS stacks from running, edit /etc/avahi/avahi-daemon.conf
and ensure the following line appears in the [server]
section:
disallow-other-stacks=yes
This helps ensure that only Avahi is responsible for mDNS traffic coming from that port on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.6.2.d. Disable Avahi Publishing
To prevent other mDNS stacks from running, edit /etc/avahi/avahi-daemon.conf
and ensure the following line appears in the [server]
section:
disallow-other-stacks=yes
This helps ensure that only Avahi is responsible for mDNS traffic coming from that port on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.6.2.e. Restrict Information Published by Avahi
If it is necessary to publish some information to the network, it should not be joined
by any extraneous information, or by information supplied by a non-trusted source
on the system.
Prevent user applications from using Avahi to publish services by adding or
correcting the following line in the [publish]
section:
disable-user-service-publishing=yes
Implement as many of the following lines as possible, to restrict the information
published by Avahi.
publish-addresses=no
publish-hinfo=no
publish-workstation=no
publish-domain=no
Inspect the files in the directory /etc/avahi/services/
. Unless there
is an operational need to publish information about each of these services,
delete the corresponding file.
These options prevent publishing attempts from succeeding, and can be applied even if publishing is disabled entirely via disable-publishing. Alternatively, these can be used to restrict the types of published information in the event that some information must be published.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.7. Print Support
The Common Unix Printing System (CUPS) service provides both local
and network printing support. A system running the CUPS service can accept
print jobs from other systems, process them, and send them to the appropriate
printer. It also provides an interface for remote administration through a web
browser. The CUPS service is installed and activated by default. The project
homepage and more detailed documentation are available at http://www.cups.org.
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3.7.a. Disable the CUPS Service
The cups
service can be disabled with the following command:
$ sudo systemctl disable cups
Turn off unneeded services to reduce attack surface.
Remediation script
#
# Disable cups.service for all systemd targets
#
systemctl disable cups.service
#
# Stop cups.service if currently running
# and disable cups.path and cups.socket so
# cups.service can't be activated
#
systemctl stop cups.service
systemctl disable cups.path
systemctl disable cups.socket
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.7.2. Configure the CUPS Service if Necessary
CUPS provides the ability to easily share local printers with other machines over the network. It does this by allowing machines to share lists of available printers. Additionally, each machine that runs the CUPS service can potentially act as a print server. Whenever possible, the printer sharing and print server capabilities of CUPS should be limited or disabled. The following recommendations should demonstrate how to do just that.
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3.7.2.a. Disable Printer Browsing Entirely if Possible
By default, CUPS listens on the network for printer list
broadcasts on UDP port 631. This functionality is called printer browsing.
To disable printer browsing entirely, edit the CUPS configuration
file, located at /etc/cups/cupsd.conf
, to include the following:
Browsing Off
The CUPS print service can be configured to broadcast a list of available printers to the network. Other machines on the network, also running the CUPS print service, can be configured to listen to these broadcasts and add and configure these printers for immediate use. By disabling this browsing capability, the machine will no longer generate or receive such broadcasts.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.7.2.b. Disable Print Server Capabilities
To prevent remote users from potentially connecting to and using locally configured printers, disable the CUPS print server sharing capabilities. To do so, limit how the server will listen for print jobs by removing the more generic port directive from /etc/cups/cupsd.conf:
Port 631
and replacing it with the Listen
directive:
Listen localhost:631
This will prevent remote users from printing to locally configured printers
while still allowing local users on the machine to print normally.
By default, locally configured printers will not be shared over the network, but if this functionality has somehow been enabled, these recommendations will disable it again. Be sure to disable outgoing printer list broadcasts, or remote users will still be able to see the locally configured printers, even if they cannot actually print to them. To limit print serving to a particular set of users, use the Policy directive.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.8. DHCP
The Dynamic Host Configuration Protocol (DHCP) allows
systems to request and obtain an IP address and other configuration
parameters from a server.
This guide recommends configuring networking on clients by manually editing
the appropriate files under /etc/sysconfig
. Use of DHCP can make client
systems vulnerable to compromise by rogue DHCP servers, and should be avoided
unless necessary. If using DHCP is necessary, however, there are best practices
that should be followed to minimize security risk.
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3.8.1. Disable DHCP Server
The DHCP server dhcpd
is not installed or activated by
default. If the software was installed and activated, but the
system does not need to act as a DHCP server, it should be disabled
and removed.
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3.8.1.a. Disable DHCP Service
The dhcpd
service should be disabled on
any system that does not need to act as a DHCP server.
The dhcpd
service can be disabled with the following command:
$ sudo systemctl disable dhcpd
Unmanaged or unintentionally activated DHCP servers may provide faulty information to clients, interfering with the operation of a legitimate site DHCP server if there is one.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.8.1.b. Uninstall DHCP Server Package
If the system does not need to act as a DHCP server,
the dhcp package can be uninstalled.
The dhcp
package can be removed with the following command:
$ sudo yum erase dhcp
Removing the DHCP server ensures that it cannot be easily or accidentally reactivated and disrupt network operation.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.8.2. Disable DHCP Server
If the system must act as a DHCP server, the configuration
information it serves should be minimized. Also, support for other protocols
and DNS-updating schemes should be explicitly disabled unless needed. The
configuration file for dhcpd is called /etc/dhcp/dhcpd.conf
. The file
begins with a number of global configuration options. The remainder of the file
is divided into sections, one for each block of addresses offered by dhcpd,
each of which contains configuration options specific to that address
block.
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3.8.2.a. Do Not Use Dynamic DNS
To prevent the DHCP server from receiving DNS information from
clients, edit /etc/dhcp/dhcpd.conf
, and add or correct the following global
option:
ddns-update-style none;
The ddns-update-style option controls only whether the DHCP server will attempt to act as a Dynamic DNS client. As long as the DNS server itself is correctly configured to reject DDNS attempts, an incorrect ddns-update-style setting on the client is harmless (but should be fixed as a best practice).
The Dynamic DNS protocol is used to remotely update the data served by a DNS server. DHCP servers can use Dynamic DNS to publish information about their clients. This setup carries security risks, and its use is not recommended. If Dynamic DNS must be used despite the risks it poses, it is critical that Dynamic DNS transactions be protected using TSIG or some other cryptographic authentication mechanism. See dhcpd.conf(5) for more information about protecting the DHCP server from passing along malicious DNS data from its clients.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.8.2.b. Deny Decline Messages
Edit /etc/dhcp/dhcpd.conf
and add or correct the following
global option to prevent the DHCP server from responding the DHCPDECLINE
messages, if possible:
deny declines;
The DHCPDECLINE message can be sent by a DHCP client to indicate that it does not consider the lease offered by the server to be valid. By issuing many DHCPDECLINE messages, a malicious client can exhaust the DHCP server's pool of IP addresses, causing the DHCP server to forget old address allocations.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.8.2.c. Deny BOOTP Queries
Unless your network needs to support older BOOTP clients, disable support for the bootp protocol by adding or correcting the global option:
deny bootp;
The bootp option tells dhcpd to respond to BOOTP queries. If support for this simpler protocol is not needed, it should be disabled to remove attack vectors against the DHCP server.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.8.2.d. Configure Logging
Ensure that the following line exists in
/etc/rsyslog.conf
:
daemon.* /var/log/daemon.log
Configure logwatch or other log monitoring tools to summarize error conditions
reported by the dhcpd process.
By default, dhcpd logs notices to the daemon facility. Sending all daemon messages to a dedicated log file is part of the syslog configuration outlined in the Logging and Auditing section
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.8.2.5. Minimize Served Information
Edit /etc/dhcp/dhcpd.conf. Examine each address range section within the file, and ensure that the following options are not defined unless there is an operational need to provide this information via DHCP:
option domain-name
option domain-name-servers
option nis-domain
option nis-servers
option ntp-servers
option routers
option time-offset
By default, the Red Hat Enterprise Linux client installation uses DHCP to request much of the above information from the DHCP server. In particular, domain-name, domain-name-servers, and routers are configured via DHCP. These settings are typically necessary for proper network functionality, but are also usually static across machines at a given site.
Because the configuration information provided by the DHCP server could be maliciously provided to clients by a rogue DHCP server, the amount of information provided via DHCP should be minimized. Remove these definitions from the DHCP server configuration to ensure that legitimate clients do not unnecessarily rely on DHCP for this information.
References
3.8.3. Disable DHCP Client
DHCP is the default network configuration method provided by the system installer, and common on many networks. Nevertheless, manual management of IP addresses for systems implies a greater degree of management and accountability for network activity.
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3.8.3.a. Disable DHCP Client
For each interface on the system (e.g. eth0), edit
/etc/sysconfig/network-scripts/ifcfg-interface
and make the
following changes:
-
Correct the BOOTPROTO line to read:
BOOTPROTO=none
-
Add or correct the following lines, substituting the appropriate values based on your site's addressing scheme:
NETMASK=255.255.255.0 IPADDR=192.168.1.2 GATEWAY=192.168.1.1
DHCP relies on trusting the local network. If the local network is not trusted, then it should not be used. However, the automatic configuration provided by DHCP is commonly used and the alternative, manual configuration, presents an unacceptable burden in many circumstances.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.8.4. Configure DHCP Client if Necessary
If DHCP must be used, then certain configuration changes can
minimize the amount of information it receives and applies from the network,
and thus the amount of incorrect information a rogue DHCP server could
successfully distribute. For more information on configuring dhclient, see the
dhclient(8)
and dhclient.conf(5)
man pages.
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3.8.4.1. Minimize the DHCP-Configured Options
Create the file /etc/dhcp/dhclient.conf
, and add an
appropriate setting for each of the ten configuration settings which can be
obtained via DHCP. For each setting, do one of the following:
If the setting should not be configured remotely by the DHCP server,
select an appropriate static value, and add the line:
supersede setting value;
If the setting should be configured remotely by the DHCP server, add the lines:
request setting;
require setting;
For example, suppose the DHCP server should provide only the IP address itself
and the subnet mask. Then the entire file should look like:
supersede domain-name "example.com";
supersede domain-name-servers 192.168.1.2;
supersede nis-domain "";
supersede nis-servers "";
supersede ntp-servers "ntp.example.com ";
supersede routers 192.168.1.1;
supersede time-offset -18000;
request subnet-mask;
require subnet-mask;
In this example, the options nis-servers and nis-domain are set to empty strings, on the assumption that the deprecated NIS protocol is not in use. It is necessary to supersede settings for unused services so that they cannot be set by a hostile DHCP server. If an option is set to an empty string, dhclient will typically not attempt to configure the service.
By default, the DHCP client program, dhclient, requests and applies
ten configuration options (in addition to the IP address) from the DHCP server.
subnet-mask, broadcast-address, time-offset, routers, domain-name,
domain-name-servers, host-name, nis-domain, nis-servers, and ntp-servers. Many
of the options requested and applied by dhclient may be the same for every
system on a network. It is recommended that almost all configuration options be
assigned statically, and only options which must vary on a host-by-host basis
be assigned via DHCP. This limits the damage which can be done by a rogue DHCP
server. If appropriate for your site, it is also possible to supersede the
host-name directive in /etc/dhcp/dhclient.conf
, establishing a static
hostname for the machine. However, dhclient does not use the host name option
provided by the DHCP server (instead using the value provided by a reverse DNS
lookup).
3.9. Network Time Protocol
The Network Time Protocol is used to manage the system
clock over a network. Computer clocks are not very accurate, so
time will drift unpredictably on unmanaged systems. Central time
protocols can be used both to ensure that time is consistent among
a network of machines, and that their time is consistent with the
outside world.
If every system on a network reliably reports the same time, then it is much
easier to correlate log messages in case of an attack. In addition, a number of
cryptographic protocols (such as Kerberos) use timestamps to prevent certain
types of attacks. If your network does not have synchronized time, these
protocols may be unreliable or even unusable.
Depending on the specifics of the network, global time accuracy may be just as
important as local synchronization, or not very important at all. If your
network is connected to the Internet, using a public timeserver (or one
provided by your enterprise) provides globally accurate timestamps which may be
essential in investigating or responding to an attack which originated outside
of your network.
A typical network setup involves a small number of internal systems operating
as NTP servers, and the remainder obtaining time information from those
internal servers.
There is a choice between the daemons ntpd
and chronyd
, which
are available from the repositories in the ntp
and chrony
packages respectively.
The default chronyd
daemon can work well when external time references
are only intermittently accesible, can perform well even when the network is
congested for longer periods of time, can usually synchronize the clock faster
and with better time accuracy, and quickly adapts to sudden changes in the rate
of the clock, for example, due to changes in the temperature of the crystal
oscillator. Chronyd
should be considered for all systems which are
frequently suspended or otherwise intermittently disconnected and reconnected
to a network. Mobile and virtual systems for example.
The ntpd
NTP daemon fully supports NTP protocol version 4 (RFC 5905),
including broadcast, multicast, manycast clients and servers, and the orphan
mode. It also supports extra authentication schemes based on public-key
cryptography (RFC 5906). The NTP daemon (ntpd
) should be considered
for systems which are normally kept permanently on. Systems which are required
to use broadcast or multicast IP, or to perform authentication of packets with
the Autokey
protocol, should consider using ntpd
.
Refer to https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/ch-Configuring_NTP_Using_the_chrony_Suite.html for more detailed comparison of features of chronyd
and ntpd
daemon features respectively, and for further guidance how to
choose between the two NTP daemons.
The upstream manual pages at http://chrony.tuxfamily.org/manual.html for
chronyd
and http://www.ntp.org for ntpd
provide additional
information on the capabilities and configuration of each of the NTP daemons.
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3.9.a. Enable the NTP Daemon
The chronyd
service can be enabled with the following command:
$ sudo systemctl enable chronyd
Note: The chronyd
daemon is enabled by default.
The
ntpd
service can be enabled with the following command:
$ sudo systemctl enable ntpd
Note: The ntpd
daemon is not enabled by default. Though as mentioned
in the previous sections in certain environments the ntpd
daemon might
be preferred to be used rather than the chronyd
one. Refer to:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/ch-Configuring_NTP_Using_the_chrony_Suite.html
for guidance which NTP daemon to choose depending on the environment used.
Enabling some of chronyd
or ntpd
services ensures
that the NTP daemon will be running and that the system will synchronize its
time to any servers specified. This is important whether the system is
configured to be a client (and synchronize only its own clock) or it is also
acting as an NTP server to other systems. Synchronizing time is essential for
authentication services such as Kerberos, but it is also important for
maintaining accurate logs and auditing possible security breaches.
The chronyd
and ntpd
NTP daemons offer all of the
functionality of ntpdate
, which is now deprecated. Additional
information on this is available at
http://support.ntp.org/bin/view/Dev/DeprecatingNtpdate
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-8(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 160. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.9.b. Specify a Remote NTP Server
To specify a remote NTP server for time synchronization, edit
the file /etc/ntp.conf
. Add or correct the following lines,
substituting the IP or hostname of a remote NTP server for ntpserver:
server ntpserver
This instructs the NTP software to contact that remote server to obtain time
data.
Synchronizing with an NTP server makes it possible to collate system logs from multiple sources or correlate computer events with real time events.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- AU-8(1). URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 160. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.9.c. Specify Additional Remote NTP Servers
Additional NTP servers can be specified for time synchronization
in the file /etc/ntp.conf
. To do so, add additional lines of the
following form, substituting the IP address or hostname of a remote NTP server for
ntpserver:
server ntpserver
Specifying additional NTP servers increases the availability of accurate time data, in the event that one of the specified servers becomes unavailable. This is typical for a system acting as an NTP server for other systems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.10. Mail Server Software
Mail servers are used to send and receive email over the network.
Mail is a very common service, and Mail Transfer Agents (MTAs) are obvious
targets of network attack.
Ensure that machines are not running MTAs unnecessarily,
and configure needed MTAs as defensively as possible.
Very few systems at any site should be configured to directly receive email over the
network. Users should instead use mail client programs to retrieve email
from a central server that supports protocols such as IMAP or POP3.
However, it is normal for most systems to be independently capable of sending email,
for instance so that cron jobs can report output to an administrator.
Most MTAs, including Postfix, support a submission-only mode in which mail can be sent from
the local system to a central site MTA (or directly delivered to a local account),
but the system still cannot receive mail directly over a network.
The alternatives
program in Red Hat Enterprise Linux permits selection of other mail server software
(such as Sendmail), but Postfix is the default and is preferred.
Postfix was coded with security in mind and can also be more effectively contained by
SELinux as its modular design has resulted in separate processes performing specific actions.
More information is available on its website, http://www.postfix.org.
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3.10.a. Enable Postfix Service
The Postfix mail transfer agent is used for local mail delivery
within the system. The default configuration only listens for connections to
the default SMTP port (port 25) on the loopback interface (127.0.0.1). It is
recommended to leave this service enabled for local mail delivery.
The postfix
service can be enabled with the following command:
$ sudo systemctl enable postfix
Local mail delivery is essential to some system maintenance and notification tasks.
Remediation script
#
# Enable postfix.service for all systemd targets
#
systemctl enable postfix.service
#
# Start postfix.service if not currently running
#
systemctl start postfix.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.10.b. Uninstall Sendmail Package
Sendmail is not the default mail transfer agent and is
not installed by default.
The sendmail
package can be removed with the following command:
$ sudo yum erase sendmail
The sendmail software was not developed with security in mind and its design prevents it from being effectively contained by SELinux. Postfix should be used instead.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.10.3. Configure SMTP For Mail Clients
This section discusses settings for Postfix in a submission-only e-mail configuration.
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3.10.3.a. Disable Postfix Network Listening
Edit the file /etc/postfix/main.cf
to ensure that only the following
inet_interfaces
line appears:
inet_interfaces = localhost
This ensures postfix
accepts mail messages
(such as cron job reports) from the local system only,
and not from the network, which protects it from network attack.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 382. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.10.4. Configure Operating System to Protect Mail Server
The guidance in this section is appropriate for any host which is operating as a site MTA, whether the mail server runs using Sendmail, Postfix, or some other software.
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3.10.4.1. Configure SSL Certificates for Use with SMTP AUTH
If SMTP AUTH is to be used, the use of SSL to protect credentials in transit is strongly recommended. There are also configurations for which it may be desirable to encrypt all mail in transit from one MTA to another, though such configurations are beyond the scope of this guide. In either event, the steps for creating and installing an SSL certificate are independent of the MTA in use, and are described here.
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3.10.4.1.1. Ensure Security of Postfix SSL Certificate
Create the PKI directory for mail certificates, if it does not already exist:
$ sudo mkdir /etc/pki/tls/mail
$ sudo chown root:root /etc/pki/tls/mail
$ sudo chmod 755 /etc/pki/tls/mail
Using removable media or some other secure transmission format, install the files generated in the previous
step onto the mail server:
/etc/pki/tls/mail/serverkey.pem: the private key mailserverkey.pem
/etc/pki/tls/mail/servercert.pem: the certificate file mailservercert.pem
Verify the ownership and permissions of these files:
$ sudo chown root:root /etc/pki/tls/mail/serverkey.pem
$ sudo chown root:root /etc/pki/tls/mail/servercert.pem
$ sudo chmod 600 /etc/pki/tls/mail/serverkey.pem
$ sudo chmod 644 /etc/pki/tls/mail/servercert.pem
Verify that the CA's public certificate file has been installed as /etc/pki/tls/CA/cacert.pem
, and has the
correct permissions:
$ sudo chown root:root /etc/pki/tls/CA/cacert.pem
$ sudo chmod 644 /etc/pki/tls/CA/cacert.pem
3.10.4.2. Configure Postfix if Necessary
Postfix stores its configuration files in the directory
/etc/postfix by default. The primary configuration file is
/etc/postfix/main.cf
.
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3.10.4.2.a. Configure SMTP Greeting Banner
Edit /etc/postfix/main.cf
, and add or correct the
following line, substituting some other wording for the banner information if
you prefer:
smtpd_banner = $myhostname ESMTP
The default greeting banner discloses that the listening mail process is Postfix. When remote mail senders connect to the MTA on port 25, they are greeted by an initial banner as part of the SMTP dialogue. This banner is necessary, but it frequently gives away too much information, including the MTA software which is in use, and sometimes also its version number. Remote mail senders do not need this information in order to send mail, so the banner should be changed to reveal only the hostname (which is already known and may be useful) and the word ESMTP, to indicate that the modern SMTP protocol variant is supported.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.10.4.2.2. Configure Postfix Resource Usage to Limit Denial of Service Attacks
Edit /etc/postfix/main.cf
. Edit the following lines to
configure the amount of system resources Postfix can consume:
default_process_limit = 100
smtpd_client_connection_count_limit = 10
smtpd_client_connection_rate_limit = 30
queue_minfree = 20971520
header_size_limit = 51200
message_size_limit = 10485760
smtpd_recipient_limit = 100
The values here are examples.
Note: The values given here are examples, and may
need to be modified for any particular site. By default, the Postfix anvil
process gathers mail receipt statistics. To get information about about what
connection rates are typical at your site, look in /var/log/maillog
for lines with the daemon name postfix/anvil.
These configuration options serve to make it more difficult for
attackers to consume resources on the MTA host. The
default_process_limit
parameter controls how many smtpd
processes can exist at a time, while
smtpd_client_connection_count_limit
controls the number of those which
can be occupied by any one remote sender, and
smtpd_client_connection_rate_limit
controls the number of connections
any one client can make per minute. By default, local hosts (those in
mynetworks
) are exempted from per-client rate limiting. The
queue_minfree
parameter establishes a free space threshold, in order
to stop e-mail receipt before the queue filesystem is entirely full. The
header_size_limit
, message_size_limit
, and
smtpd_recipient_limit
parameters place bounds on the legal sizes of
messages received via SMTP.
3.10.4.2.3. Control Mail Relaying
Postfix's mail relay controls are implemented with the help of the smtpd recipient restrictions option, which controls the restrictions placed on the SMTP dialogue once the sender and recipient envelope addresses are known. The guidance in the following sections should be applied to all machines. If there are machines which must be allowed to relay mail, but which cannot be trusted to relay unconditionally, configure SMTP AUTH with SSL support.
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3.10.4.2.3.1. Configure Trusted Networks and Hosts
Edit /etc/postfix/main.cf
, and configure the contents of
the mynetworks
variable in one of the following ways:
-
If any machine in the subnet containing the MTA may be trusted to relay messages, add or correct the following line:
This is also the default setting, and is in effect if allmynetworks_style = subnet
my_networks_style
directives are commented. -
If only the MTA host itself is trusted to relay messages, add or correct the following line:
mynetworks_style = host
-
If the set of machines which can relay is more complicated, manually specify an entry for each netblock or IP address which is trusted to relay by setting the
mynetworks
variable directly:mynetworks = 10.0.0.0/16, 192.168.1.0/24, 127.0.0.1
The mynetworks
variable must contain only the set of
machines for which this MTA should unconditionally relay mail. This is a trust
relationship - if spammers gain access to these machines, your site will
effectively become an open relay. It is recommended that only machines which
are managed by you or by another trusted organization be placed in mynetworks,
and users of all other machines be required to use SMTP AUTH to send mail.
3.10.4.2.3.2. Enact SMTP Relay Restrictions
To configure Postfix to restrict addresses to which it
will send mail, see:
http://www.postfix.org/SMTPD_ACCESS_README.html#danger
The full contents of smtpd_recipient_restrictions
will
vary by site, since this is a common place to put spam restrictions and other
site-specific options. The permit_mynetworks
option allows all mail to
be relayed from the machines in mynetworks
. Then, the
reject_unauth_destination
option denies all mail whose destination
address is not local, preventing any other machines from relaying. These two
options should always appear in this order, and should usually follow one
another immediately unless SMTP AUTH is used.
3.10.4.2.3.3. Enact SMTP Recipient Restrictions
To configure Postfix to restrict addresses to which it
will send mail, see:
http://www.postfix.org/SMTPD_ACCESS_README.html#danger
The full contents of smtpd_recipient_restrictions
will
vary by site, since this is a common place to put spam restrictions and other
site-specific options. The permit_mynetworks
option allows all mail to
be relayed from the machines in mynetworks
. Then, the
reject_unauth_destination
option denies all mail whose destination
address is not local, preventing any other machines from relaying. These two
options should always appear in this order, and should usually follow one
another immediately unless SMTP AUTH is used.
3.10.4.2.3.4. Require SMTP AUTH Before Relaying from Untrusted Clients
SMTP authentication allows remote clients to relay mail safely by requiring them to authenticate before submitting mail. Postfix's SMTP AUTH uses an authentication library called SASL, which is not part of Postfix itself. To enable the use of SASL authentication, see http://www.postfix.org/SASL_README.html
3.10.4.2.3.5. Use TLS for SMTP AUTH
Postfix provides options to use TLS for certificate-based authentication and encrypted sessions. An encrypted session protects the information that is transmitted with SMTP mail or with SASL authentication. To configure Postfix to protect all SMTP AUTH transactions using TLS, see http://www.postfix.org/TLS_README.html.
3.11. LDAP
LDAP is a popular directory service, that is, a standardized way of looking up information from a central database. Red Hat Enterprise Linux 7 includes software that enables a system to act as both an LDAP client and server.
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3.11.1. Configure OpenLDAP Clients
This section provides information on which security settings are
important to configure in OpenLDAP clients by manually editing the appropriate
configuration files. Red Hat Enterprise Linux 7 provides an automated configuration tool called
authconfig and a graphical wrapper for authconfig called
system-config-authentication
. However, these tools do not provide as
much control over configuration as manual editing of configuration files. The
authconfig tools do not allow you to specify locations of SSL certificate
files, which is useful when trying to use SSL cleanly across several protocols.
Installation and configuration of OpenLDAP on Red Hat Enterprise Linux 7 is available at
https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/ch-Directory_Servers.html.
Before configuring any system to be an LDAP client, ensure that a working LDAP server is present on the network.
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3.11.1.a. Configure LDAP Client to Use TLS For All Transactions
Configure LDAP to enforce TLS use. First, edit the file
/etc/pam_ldap.conf
, and add or correct the following lines:
ssl start_tls
Then review the LDAP server and ensure TLS has been configured.
The ssl directive specifies whether to use ssl or not. If not specified it will default to no. It should be set to start_tls rather than doing LDAP over SSL.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 776. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 778. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1453. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.11.1.b. Configure Certificate Directives for LDAP Use of TLS
Ensure a copy of a trusted CA certificate has been placed in
the file /etc/pki/tls/CA/cacert.pem
. Configure LDAP to enforce TLS
use and to trust certificates signed by that CA. First, edit the file
/etc/pam_ldap.conf
, and add or correct either of the following lines:
tls_cacertdir /etc/pki/tls/CA
or
tls_cacertfile /etc/pki/tls/CA/cacert.pem
Then review the LDAP server and ensure TLS has been configured.
The tls_cacertdir or tls_cacertfile directives are required when tls_checkpeer is configured (which is the default for openldap versions 2.1 and up). These directives define the path to the trust certificates signed by the site CA.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 776. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 778. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1453. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.11.2. Configure OpenLDAP Server
This section details some security-relevant settings for an OpenLDAP server. Installation and configuration of OpenLDAP on Red Hat Enterprise Linux 7 is available at: https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/ch-Directory_Servers.html.
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3.11.2.a. Uninstall openldap-servers Package
The openldap-servers
package should be removed if not in use.
Is this machine the OpenLDAP server? If not, remove the package.
$ sudo yum erase openldap-servers
The openldap-servers RPM is not installed by default on Red Hat Enterprise Linux 7
machines. It is needed only by the OpenLDAP server, not by the
clients which use LDAP for authentication. If the system is not
intended for use as an LDAP Server it should be removed.
Unnecessary packages should not be installed to decrease the attack surface of the system. While this software is clearly essential on an LDAP server, it is not necessary on typical desktop or workstation systems.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- 366. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- Test attestation on 20121024 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.11.2.2. Install and Protect LDAP Certificate Files
Create the PKI directory for LDAP certificates if it does not already exist:
$ sudo mkdir /etc/pki/tls/ldap
$ sudo chown root:root /etc/pki/tls/ldap
$ sudo chmod 755 /etc/pki/tls/ldap
Using removable media or some other secure transmission format, install the certificate files
onto the LDAP server:
-
/etc/pki/tls/ldap/serverkey.pem
: the private keyldapserverkey.pem
-
/etc/pki/tls/ldap/servercert.pem
: the certificate fileldapservercert.pem
Verify the ownership and permissions of these files:
$ sudo chown root:ldap /etc/pki/tls/ldap/serverkey.pem
$ sudo chown root:ldap /etc/pki/tls/ldap/servercert.pem
$ sudo chmod 640 /etc/pki/tls/ldap/serverkey.pem
$ sudo chmod 640 /etc/pki/tls/ldap/servercert.pem
Verify that the CA's public certificate file has been installed as
/etc/pki/tls/CA/cacert.pem
, and has the correct permissions:
$ sudo mkdir /etc/pki/tls/CA
$ sudo chown root:root /etc/pki/tls/CA/cacert.pem
$ sudo chmod 644 /etc/pki/tls/CA/cacert.pem
As a result of these steps, the LDAP server will have access to its own private
certificate and the key with which that certificate is encrypted, and to the
public certificate file belonging to the CA. Note that it would be possible for
the key to be protected further, so that processes running as ldap could not
read it. If this were done, the LDAP server process would need to be restarted
manually whenever the server rebooted.
3.12. NFS and RPC
The Network File System is a popular distributed filesystem for the Unix environment, and is very widely deployed. This section discusses the circumstances under which it is possible to disable NFS and its dependencies, and then details steps which should be taken to secure NFS's configuration. This section is relevant to machines operating as NFS clients, as well as to those operating as NFS servers.
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3.12.1. Disable All NFS Services if Possible
If there is not a reason for the system to operate as either an NFS client or an NFS server, follow all instructions in this section to disable subsystems required by NFS.
The steps in this section will prevent a machine from operating as either an NFS client or an NFS server. Only perform these steps on machines which do not need NFS at all.
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3.12.1.1. Disable Services Used Only by NFS
If NFS is not needed, disable the NFS client daemons nfslock, rpcgssd, and rpcidmapd.
All of these daemons run with elevated privileges, and many listen for network
connections. If they are not needed, they should be disabled to improve system
security posture.
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3.12.1.1.a. Disable Network File System Lock Service (nfslock)
The Network File System Lock (nfslock) service starts the required
remote procedure call (RPC) processes which allow clients to lock files on the
server. If the local machine is not configured to mount NFS filesystems then
this service should be disabled.
The nfslock
service can be disabled with the following command:
$ sudo systemctl disable nfslock
Remediation script
#
# Disable nfs-lock.service for all systemd targets
#
systemctl disable nfs-lock.service
#
# Stop nfs-lock.service if currently running
#
systemctl stop nfs-lock.service
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.1.1.b. Disable Secure RPC Client Service (rpcgssd)
The rpcgssd service manages RPCSEC GSS contexts required to secure protocols
that use RPC (most often Kerberos and NFS). The rpcgssd service is the
client-side of RPCSEC GSS. If the system does not require secure RPC then this
service should be disabled.
The rpcgssd
service can be disabled with the following command:
$ sudo systemctl disable rpcgssd
Remediation script
#
# Disable nfs-secure.service (rpcgssd) for all systemd targets
#
systemctl disable nfs-secure.service
#
# Stop nfs-secure.service (rpcgssd) if currently running
#
systemctl stop nfs-secure.service
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.1.1.c. Disable RPC ID Mapping Service (rpcidmapd)
The rpcidmapd service is used to map user names and groups to UID
and GID numbers on NFSv4 mounts. If NFS is not in use on the local system then
this service should be disabled.
The rpcidmapd
service can be disabled with the following command:
$ sudo systemctl disable rpcidmapd
Remediation script
#
# Disable nfs-idmap.service (rpcidmapd) for all systemd targets
#
systemctl disable nfs-idmap.service
#
# Stop nfs-idmap.service (rpcidmapd) if currently running
#
systemctl stop nfs-idmap.service
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.1.2. Disable netfs if Possible
To determine if any network filesystems handled by netfs are currently mounted on the system execute the following command:
$ mount -t nfs,nfs4,smbfs,cifs,ncpfs
If the command did not return any output then disable netfs.
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3.12.1.2.a. Disable Network File Systems (netfs)
The netfs script manages the boot-time mounting of several types
of networked filesystems, of which NFS and Samba are the most common. If these
filesystem types are not in use, the script can be disabled, protecting the
system somewhat against accidental or malicious changes to /etc/fstab
and against flaws in the netfs script itself.
The netfs
service can be disabled with the following command:
$ sudo systemctl disable netfs
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.2. Configure All Machines which Use NFS
The steps in this section are appropriate for all machines which run NFS, whether they operate as clients or as servers.
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3.12.2.1. Make Each Machine a Client or a Server, not Both
If NFS must be used, it should be deployed in the simplest configuration possible to avoid maintainability problems which may lead to unnecessary security exposure. Due to the reliability and security problems caused by NFS (specially NFSv3 and NFSv2), it is not a good idea for machines which act as NFS servers to also mount filesystems via NFS. At the least, crossed mounts (the situation in which each of two servers mounts a filesystem from the other) should never be used.
3.12.2.2. Configure NFS Services to Use Fixed Ports (NFSv3 and NFSv2)
Firewalling should be done at each host and at the border
firewalls to protect the NFS daemons from remote access, since NFS servers
should never be accessible from outside the organization. However, by default
for NFSv3 and NFSv2, the RPC Bind service assigns each NFS service to a port
dynamically at service startup time. Dynamic ports cannot be protected by port
filtering firewalls such as firewalld
.
Therefore, restrict each service to always use a given port, so that
firewalling can be done effectively. Note that, because of the way RPC is
implemented, it is not possible to disable the RPC Bind service even if ports
are assigned statically to all RPC services.
In NFSv4, the mounting and locking protocols have been incorporated into the
protocol, and the server listens on the the well-known TCP port 2049. As such,
NFSv4 does not need to interact with the rpcbind, lockd, and rpc.statd
daemons, which can and should be disabled in a pure NFSv4 environment. The
rpc.mountd
daemon is still required on the NFS server to setup
exports, but is not involved in any over-the-wire operations.
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3.12.2.2.a. Configure lockd to use static TCP port
Configure the lockd
daemon to use a static TCP port as
opposed to letting the RPC Bind service dynamically assign a port. Edit the
file /etc/sysconfig/nfs
. Add or correct the following line:
LOCKD_TCPPORT=lockd-port
Where lockd-port
is a port which is not used by any other service on
your network.
Restrict service to always use a given port, so that firewalling can be done effectively.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.2.2.b. Configure lockd to use static UDP port
Configure the lockd
daemon to use a static UDP port as
opposed to letting the RPC Bind service dynamically assign a port. Edit the
file /etc/sysconfig/nfs
. Add or correct the following line:
LOCKD_UDPPORT=lockd-port
Where lockd-port
is a port which is not used by any other service on
your network.
Restricting services to always use a given port enables firewalling to be done more effectively.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.2.2.c. Configure statd to use static port
Configure the statd
daemon to use a static port as
opposed to letting the RPC Bind service dynamically assign a port. Edit the
file /etc/sysconfig/nfs
. Add or correct the following line:
STATD_PORT=statd-port
Where statd-port
is a port which is not used by any other service on your network.
Restricting services to always use a given port enables firewalling to be done more effectively.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.2.2.d. Configure mountd to use static port
Configure the mountd
daemon to use a static port as
opposed to letting the RPC Bind service dynamically assign a port. Edit the
file /etc/sysconfig/nfs
. Add or correct the following line:
MOUNTD_PORT=statd-port
Where mountd-port
is a port which is not used by any other service on your network.
Restricting services to always use a given port enables firewalling to be done more effectively.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.3. Configure NFS Clients
The steps in this section are appropriate for machines which operate as NFS clients.
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3.12.3.1. Disable NFS Server Daemons
There is no need to run the NFS server daemons nfs
and
rpcsvcgssd
except on a small number of properly secured machines
designated as NFS servers. Ensure that these daemons are turned off on
clients.
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3.12.3.1.a. Specify UID and GID for Anonymous NFS Connections
To specify the UID and GID for remote root users, edit the /etc/exports
file and add the following for each export:
anonuid=value greater than UID_MAX from /etc/login.defs
anongid=value greater than GID_MAX from /etc/login.defs
Alternatively, functionally equivalent values of 60001, 65534, 65535 may be used.
Specifying the anonymous UID and GID ensures that the remote root user is mapped to a local account which has no permissions on the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.3.1.b. Disable Network File System (nfs)
The Network File System (NFS) service allows remote hosts to mount
and interact with shared filesystems on the local machine. If the local machine
is not designated as a NFS server then this service should be disabled.
The nfs
service can be disabled with the following command:
$ sudo systemctl disable nfs
Unnecessary services should be disabled to decrease the attack surface of the system.
Remediation script
#
# Disable nfs.service for all systemd targets
#
systemctl disable nfs.service
#
# Stop nfs.service if currently running
#
systemctl stop nfs.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.12.3.1.c. Disable Secure RPC Server Service (rpcsvcgssd)
The rpcsvcgssd service manages RPCSEC GSS contexts required to
secure protocols that use RPC (most often Kerberos and NFS). The rpcsvcgssd
service is the server-side of RPCSEC GSS. If the system does not require secure
RPC then this service should be disabled.
The rpcsvcgssd
service can be disabled with the following command:
$ sudo systemctl disable rpcsvcgssd
Unnecessary services should be disabled to decrease the attack surface of the system.
Remediation script
#
# Disable nfs-secure-server.service (rpcsvcgssd) for all systemd targets
#
systemctl disable nfs-secure-server.service
#
# Stop nfs-secure-server.service (rpcsvcgssd) if currently running
#
systemctl stop nfs-secure-server.service
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.12.3.2. Mount Remote Filesystems with Restrictive Options
Edit the file /etc/fstab
. For each filesystem whose type
(column 3) is nfs
or nfs4
, add the text
,nodev,nosuid
to the list of mount options in column 4. If
appropriate, also add ,noexec
.
See the section titled "Restrict Partition Mount Options" for a description of
the effects of these options. In general, execution of files mounted via NFS
should be considered risky because of the possibility that an adversary could
intercept the request and substitute a malicious file. Allowing setuid files to
be executed from remote servers is particularly risky, both for this reason and
because it requires the clients to extend root-level trust to the NFS
server.
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3.12.3.2.a. Mount Remote Filesystems with nodev
Add the nodev
option to the fourth column of
/etc/fstab
for the line which controls mounting of
any NFS mounts.
Legitimate device files should only exist in the /dev directory. NFS mounts should not present device files to users.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- CM-7. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- MP-2. URL: <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-53r4.pdf>.
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.12.3.2.b. Mount Remote Filesystems with nosuid
Add the nosuid
option to the fourth column of
/etc/fstab
for the line which controls mounting of
any NFS mounts.
NFS mounts should not present suid binaries to users. Only vendor-supplied suid executables should be installed to their default location on the local filesystem.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- Test attestation on 20121025 by DS. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
3.12.4. Configure NFS Servers
The steps in this section are appropriate for machines which operate as NFS servers.
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3.12.4.a. Use Root-Squashing on All Exports
If a filesystem is exported using root squashing, requests from root on the client
are considered to be unprivileged (mapped to a user such as nobody). This provides some mild
protection against remote abuse of an NFS server. Root squashing is enabled by default, and
should not be disabled.
Ensure that no line in /etc/exports
contains the option no_root_squash
.
If the NFS server allows root access to local file systems from remote hosts, this access could be used to compromise the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.4.b. Restrict NFS Clients to Privileged Ports
By default, the server NFS implementation requires that all client requests be made
from ports less than 1024. If your organization has control over machines connected to its
network, and if NFS requests are prohibited at the border firewall, this offers some protection
against malicious requests from unprivileged users. Therefore, the default should not be changed.
To ensure that the default has not been changed, ensure no line in
/etc/exports
contains the option insecure
.
Allowing client requests to be made from ports higher than 1024 could allow a unprivileged user to initiate an NFS connection. If the unprivileged user account has been compromised, an attacker could gain access to data on the NFS server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.12.4.c. Ensure Insecure File Locking is Not Allowed
By default the NFS server requires secure file-lock requests,
which require credentials from the client in order to lock a file. Most NFS
clients send credentials with file lock requests, however, there are a few
clients that do not send credentials when requesting a file-lock, allowing the
client to only be able to lock world-readable files. To get around this, the
insecure_locks
option can be used so these clients can access the
desired export. This poses a security risk by potentially allowing the client
access to data for which it does not have authorization.
Remove any instances of the
insecure_locks
option from the file /etc/exports
.
Allowing insecure file locking could allow for sensitive data to be viewed or edited by an unauthorized user.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 764. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
3.12.4.4. Configure the Exports File Restrictively
Linux's NFS implementation uses the file /etc/exports
to control what filesystems
and directories may be accessed via NFS. (See the exports(5)
manpage for more information about the
format of this file.)
The syntax of the exports
file is not necessarily checked fully on reload, and syntax errors
can leave your NFS configuration more open than intended. Therefore, exercise caution when modifying
the file.
The syntax of each line in /etc/exports
is:
/DIR host1(opt1,opt2) host2(opt3)
where /DIR
is a directory or filesystem to export, hostN
is an IP address, netblock,
hostname, domain, or netgroup to which to export, and optN
is an option.
3.12.4.5. Use Access Lists to Enforce Authorization Restrictions
When configuring NFS exports, ensure that each export line in /etc/exports
contains
a list of hosts which are allowed to access that export. If no hosts are specified on an export line,
then that export is available to any remote host which requests it. All lines of the exports file should
specify the hosts (or subnets, if needed) which are allowed to access the exported directory, so that
unknown or remote hosts will be denied.
Authorized hosts can be specified in several different formats:
-
Name or alias that is recognized by the resolver
-
Fully qualified domain name
-
IP address
-
IP subnets in the format
address/netmask
oraddress/CIDR
3.12.4.6. Export Filesystems Read-Only if Possible
If a filesystem is being exported so that users can view the files in a convenient
fashion, but there is no need for users to edit those files, exporting the filesystem read-only
removes an attack vector against the server. The default filesystem export mode is ro
,
so do not specify rw
without a good reason.
3.13. DNS Server
Most organizations have an operational need to run at least one nameserver. However, there are many common attacks involving DNS server software, and this server software should be disabled on any system on which it is not needed.
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3.13.1. Disable DNS Server
DNS software should be disabled on any machine which does not need to be a nameserver. Note that the BIND DNS server software is not installed on Red Hat Enterprise Linux 7 by default. The remainder of this section discusses secure configuration of machines which must be nameservers.
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3.13.1.a. Disable DNS Server
The named
service can be disabled with the following command:
$ sudo systemctl disable named
All network services involve some risk of compromise due to implementation flaws and should be disabled if possible.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.13.1.b. Uninstall bind Package
To remove the bind
package, which contains the
named
service, run the following command:
$ sudo yum erase bind
If there is no need to make DNS server software available, removing it provides a safeguard against its activation.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.13.2. Isolate DNS from Other Services
This section discusses mechanisms for preventing the DNS server from interfering with other services. This is done both to protect the remainder of the network should a nameserver be compromised, and to make direct attacks on nameservers more difficult.
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3.13.2.1. Run DNS Software on Dedicated Servers
Since DNS is a high-risk service which must frequently be made available to the entire Internet, it is strongly recommended that no other services be offered by machines which act as organizational DNS servers.
3.13.2.2. Run DNS Software in a chroot Jail
Install the bind-chroot
package:
$ sudo yum install bind-chroot
Place a valid named.conf file inside the chroot jail:
$ sudo cp /etc/named.conf /var/named/chroot/etc/named.conf
$ sudo chown root:root /var/named/chroot/etc/named.conf
$ sudo chmod 644 /var/named/chroot/etc/named.conf
Create and populate an appropriate zone directory within the jail, based on the
options directive. If your named.conf
includes:
options {
directory "/path/to/DIRNAME ";
...
}
then copy that directory and its contents from the original zone directory:
$ sudo cp -r /path/to/DIRNAME /var/named/chroot/DIRNAME
Add or correct the following line within /etc/sysconfig/named
:
ROOTDIR=/var/named/chroot
If you are running BIND in a chroot jail, then you
should use the jailed named.conf
as the primary nameserver
configuration file. That is, when this guide recommends editing
/etc/named.conf
, you should instead edit
/var/named/chroot/etc/named.conf
.
Chroot jails are not foolproof. However, they serve to make it more difficult for a compromised program to be used to attack the entire host. They do this by restricting a program's ability to traverse the directory upward, so that files outside the jail are not visible to the chrooted process. Since RHEL supports a standard mechanism for placing BIND in a chroot jail, you should take advantage of this feature.
3.13.3. Protect DNS Data from Tampering or Attack
This section discusses DNS configuration options which make it more difficult for attackers to gain access to private DNS data or to modify DNS data.
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3.13.3.a. Disable Zone Transfers from the Nameserver
Is it necessary for a secondary nameserver to receive zone data
via zone transfer from the primary server? If not, follow the instructions in
this section. If so, see the next section for instructions on protecting zone
transfers.
Add or correct the following directive within /etc/named.conf
:
options {
allow-transfer { none; };
...
}
If both the primary and secondary nameserver are under your control, or if you have only one nameserver, it may be possible to use an external configuration management mechanism to distribute zone updates. In that case, it is not necessary to allow zone transfers within BIND itself, so they should be disabled to avoid the potential for abuse.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.13.3.b. Authenticate Zone Transfers
If it is necessary for a secondary nameserver to receive zone data via zone transfer from the primary server, follow the instructions here. Use dnssec-keygen to create a symmetric key file in the current directory:
$ cd /tmp
$ sudo dnssec-keygen -a HMAC-MD5 -b 128 -n HOST dns.example.com
Kdns.example.com .+aaa +iiiii
This output is the name of a file containing the new key. Read the file to find
the base64-encoded key string:
$ sudo cat Kdns.example.com .+NNN +MMMMM .key
dns.example.com IN KEY 512 3 157 base64-key-string
Add the directives to /etc/named.conf
on the primary server:
key zone-transfer-key {
algorithm hmac-md5;
secret "base64-key-string ";
};
zone "example.com " IN {
type master;
allow-transfer { key zone-transfer-key; };
...
};
Add the directives below to /etc/named.conf
on the secondary nameserver:
key zone-transfer-key {
algorithm hmac-md5;
secret "base64-key-string ";
};
server IP-OF-MASTER {
keys { zone-transfer-key; };
};
zone "example.com " IN {
type slave;
masters { IP-OF-MASTER ; };
...
};
The purpose of the dnssec-keygen command is to create the shared secret string base64-key-string. Once this secret has been obtained and inserted into named.conf on the primary and secondary servers, the key files Kdns.example.com .+NNN +MMMMM .key and Kdns.example.com .+NNN +MMMMM .private are no longer needed, and may safely be deleted.
The BIND transaction signature (TSIG) functionality allows primary and secondary nameservers to use a shared secret to verify authorization to perform zone transfers. This method is more secure than using IP-based limiting to restrict nameserver access, since IP addresses can be easily spoofed. However, if you cannot configure TSIG between your servers because, for instance, the secondary nameserver is not under your control and its administrators are unwilling to configure TSIG, you can configure an allow-transfer directive with numerical IP addresses or ACLs as a last resort.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.13.3.c. Disable Dynamic Updates
Is there a mission-critical reason to enable the risky dynamic
update functionality? If not, edit /etc/named.conf
. For each zone
specification, correct the following directive if necessary:
zone "example.com " IN {
allow-update { none; };
...
};
Dynamic updates allow remote servers to add, delete, or modify any entries in your zone file. Therefore, they should be considered highly risky, and disabled unless there is a very good reason for their use. If dynamic updates must be allowed, IP-based ACLs are insufficient protection, since they are easily spoofed. Instead, use TSIG keys (see the previous section for an example), and consider using the update-policy directive to restrict changes to only the precise type of change needed.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.13.3.4. Run Separate DNS Servers for External and Internal Queries
Is it possible to run external and internal nameservers on
separate machines? If so, follow the configuration guidance in this section. On
the external nameserver, edit /etc/named.conf
to add or correct the
following directives:
options {
allow-query { any; };
recursion no;
...
};
zone "example.com " IN {
...
};
On the internal nameserver, edit /etc/named.conf
. Add or correct the
following directives, where SUBNET is the numerical IP representation of your
organization in the form xxx.xxx.xxx.xxx/xx:
acl internal {
SUBNET ;
localhost;
};
options {
allow-query { internal; };
...
};
zone "internal.example.com " IN {
...
};
Enterprise nameservers generally serve two functions. One is to
provide public information about the machines in a domain for the benefit of
outside users who wish to contact those machines, for instance in order to send
mail to users in the enterprise, or to visit the enterprise's external web
page. The other is to provide nameservice to client machines within the
enterprise. Client machines require both private information about enterprise
machines (which may be different from the public information served to the rest
of the world) and public information about machines outside the enterprise,
which is used to send mail or visit websites outside of the organization.
In order to provide the public nameservice function, it is necessary to share
data with untrusted machines which request it - otherwise, the enterprise
cannot be conveniently contacted by outside users. However, internal data
should be protected from disclosure, and serving irrelevant public name queries
for outside domains leaves the DNS server open to cache poisoning and other
attacks. Therefore, local network nameservice functions should not be provided
to untrusted machines.
Separate machines should be used to fill these two functions whenever possible.
3.13.3.5. Use Views to Partition External and Internal Information
If it is not possible to run external and internal nameservers on
separate physical machines, run BIND9 and simulate this feature using views.
Edit /etc/named.conf
. Add or correct the following directives (where
SUBNET is the numerical IP representation of your organization in the form
xxx.xxx.xxx.xxx/xx):
acl internal {
SUBNET ;
localhost;
};
view "internal-view" {
match-clients { internal; };
zone "." IN {
type hint;
file "db.cache";
};
zone "internal.example.com " IN {
...
};
};
view "external-view" {
match-clients { any; };
recursion no;
zone "example.com " IN {
...
};
};
As shown in the example, database files which are required for recursion, such as the root hints file, must be available to any clients which are allowed to make recursive queries. Under typical circumstances, this includes only the internal clients which are allowed to use this server as a general-purpose nameserver.
The view feature is provided by BIND9 as a way to allow a single nameserver to make different sets of data available to different sets of clients. If possible, it is always better to run external and internal nameservers on separate machines, so that even complete compromise of the external server cannot be used to obtain internal data or confuse internal DNS clients. However, this is not always feasible, and use of a feature like views is preferable to leaving internal DNS data entirely unprotected.
3.14. FTP Server
FTP is a common method for allowing remote access to
files. Like telnet, the FTP protocol is unencrypted, which means
that passwords and other data transmitted during the session can be
captured and that the session is vulnerable to hijacking.
Therefore, running the FTP server software is not recommended.
However, there are some FTP server configurations which may
be appropriate for some environments, particularly those which
allow only read-only anonymous access as a means of downloading
data available to the public.
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3.14.1. Disable vsftpd if Possible
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3.14.1.a. Disable vsftpd Service
The vsftpd
service can be disabled with the following command:
$ sudo systemctl disable vsftpd
Running FTP server software provides a network-based avenue of attack, and should be disabled if not needed. Furthermore, the FTP protocol is unencrypted and creates a risk of compromising sensitive information.
Remediation script
if service vsftpd status >/dev/null; then
service vsftpd stop
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.14.1.b. Uninstall vsftpd Package
The vsftpd
package can be removed with the following command:
$ sudo yum erase vsftpd
Removing the vsftpd package decreases the risk of its accidental activation.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.14.2. Use vsftpd to Provide FTP Service if Necessary
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3.14.2.a. Install vsftpd Package
If this machine must operate as an FTP server, install the vsftpd
package via the standard channels.
$ sudo yum install vsftpd
After Red Hat Enterprise Linux 2.1, Red Hat switched from distributing wu-ftpd with Red Hat Enterprise Linux to distributing vsftpd. For security and for consistency with future Red Hat releases, the use of vsftpd is recommended.
Remediation script
yum -y install vsftpd
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.14.3. Use vsftpd to Provide FTP Service if Necessary
The primary vsftpd configuration file is
/etc/vsftpd.conf
, if that file exists, or
/etc/vsftpd/vsftpd.conf
if it does not.
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3.14.3.a. Enable Logging of All FTP Transactions
Add or correct the following configuration options within the vsftpd
configuration file, located at /etc/vsftpd/vsftpd.conf
:
xferlog_enable=YES
xferlog_std_format=NO
log_ftp_protocol=YES
If verbose logging to vsftpd.log
is done, sparse logging of downloads to /var/log/xferlog
will not also occur. However, the information about what files were downloaded is included in the information logged to vsftpd.log
To trace malicious activity facilitated by the FTP service, it must be configured to ensure that all commands sent to
the FTP server are logged using the verbose vsftpd log
format. The default vsftpd log file is /var/log/vsftpd.log
.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.14.3.b. Create Warning Banners for All FTP Users
Edit the vsftpd configuration file, which resides at /etc/vsftpd/vsftpd.conf
by default. Add or correct the following configuration options:
banner_file=/etc/issue
This setting will cause the system greeting banner to be used for FTP connections as well.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.14.3.c. Disable FTP Uploads if Possible
Is there a mission-critical reason for users to upload files via FTP? If not, edit the vsftpd configuration file to add or correct the following configuration options:
write_enable=NO
If FTP uploads are necessary, follow the guidance in the remainder of this section to secure these transactions
as much as possible.
Anonymous FTP can be a convenient way to make files available for universal download. However, it is less common to have a need to allow unauthenticated users to place files on the FTP server. If this must be done, it is necessary to ensure that files cannot be uploaded and downloaded from the same directory.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.14.3.d. Place the FTP Home Directory on its Own Partition
By default, the anonymous FTP root is the home directory of the FTP user account. The df command can be used to verify that this directory is on its own partition.
If there is a mission-critical reason for anonymous users to upload files, precautions must be taken to prevent these users from filling a disk used by other services.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.14.3.5. Restrict the Set of Users Allowed to Access FTP
This section describes how to disable non-anonymous (password-based) FTP logins, or, if it is not possible to do this entirely due to legacy applications, how to restrict insecure FTP login to only those users who have an identified need for this access.
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3.14.3.5.a. Restrict Access to Anonymous Users if Possible
Is there a mission-critical reason for users to transfer files to/from their own accounts using FTP, rather than using a secure protocol like SCP/SFTP? If not, edit the vsftpd configuration file. Add or correct the following configuration option:
local_enable=NO
If non-anonymous FTP logins are necessary, follow the guidance in the remainder of this section to secure
these logins as much as possible.
The use of non-anonymous FTP logins is strongly discouraged. Since SSH clients and servers are widely available, and since SSH provides support for a transfer mode which resembles FTP in user interface, there is no good reason to allow password-based FTP access.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.14.3.5.2. Limit Users Allowed FTP Access if Necessary
If there is a mission-critical reason for users to access their accounts via the insecure FTP protocol, limit the set of users who are allowed this access. Edit the vsftpd configuration file. Add or correct the following configuration options:
userlist_enable=YES
userlist_file=/etc/vsftp.ftpusers
userlist_deny=NO
Edit the file /etc/vsftp.ftpusers
. For each user USERNAME who should be allowed to access the system via FTP, add a line containing that user's name:
USERNAME
If anonymous access is also required, add the anonymous usernames to /etc/vsftp.ftpusers
as well.
anonymous
ftp
Historically, the file /etc/ftpusers
contained a list of users who were not allowed to access the system via FTP. It was used to prevent system users such as the root user from logging in via the insecure FTP protocol. However, when the configuration option userlist deny=NO
is set, vsftpd interprets ftpusers as the set of users who are allowed to login via FTP. Since it should be possible for most users to access their accounts via secure protocols, it is recommended that this setting be used, so that non-anonymous FTP access can be limited to legacy users who have been explicitly identified.
3.14.3.6. Configure Firewalls to Protect the FTP Server
By default, firewalld
blocks access to the ports used by the web server.
To configure firewalld
to allow access, run the following command(s):
firewall-cmd --permanent --add-service=ftp
These settings configure firewalld to allow connections to an FTP server. The first line allows initial connections
to the FTP server port.
FTP is an older protocol which is not very compatible with firewalls. During the initial FTP dialogue, the client
and server negotiate an arbitrary port to be used for data transfer. The ip_conntrack_ftp
module is used by
firewalld to listen to that dialogue and allow connections to the data ports which FTP negotiates. This allows an
FTP server to operate on a machine which is running a firewall.
3.15. Web Server
The web server is responsible for providing access to
content via the HTTP protocol. Web servers represent a significant
security risk because:
-
The HTTP port is commonly probed by malicious sources
-
Web server software is very complex, and includes a long history of vulnerabilities
-
The HTTP protocol is unencrypted and vulnerable to passive monitoring
The system's default web server software is Apache 2 and is
provided in the RPM package httpd
.
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3.15.1. Disable Apache if Possible
If Apache was installed and activated, but the system does not need to act as a web server, then it should be disabled and removed from the system.
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3.15.1.a. Disable httpd Service
The httpd
service can be disabled with the following command:
$ sudo systemctl disable httpd
Running web server software provides a network-based avenue of attack, and should be disabled if not needed.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.15.1.b. Uninstall httpd Package
The httpd
package can be removed with the following command:
$ sudo yum erase httpd
If there is no need to make the web server software available, removing it provides a safeguard against its activation.
Remediation script
if rpm -qa | grep -q httpd; then
yum -y remove httpd
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.15.2. Install Apache if Necessary
If httpd
was not installed and activated, but the system
needs to act as a web server, then it should be installed on the system. Follow these
guidelines to install it defensively. The httpd
package can be installed with
the following command:
$ sudo yum install httpd
This method of installation is recommended over installing the "Web Server"
package group during the system installation process. The Web Server package
group includes many packages which are likely extraneous, while the
command-line method installs only the required httpd
package itself.
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3.15.2.1. Confirm Minimal Built-in Modules Installed
The default httpd
installation minimizes the number of
modules that are compiled directly into the binary (core prefork http_core
mod_so
). This minimizes risk by limiting the capabilities allowed by the
web server.
Query the set of compiled-in modules using the following command:
$ httpd -l
If the number of compiled-in modules is significantly larger than the
aforementioned set, this guide recommends re-installing httpd
with a
reduced configuration. Minimizing the number of modules that are compiled into
the httpd
binary, reduces risk by limiting the capabilities allowed by
the webserver.
3.15.3. Secure Apache Configuration
The httpd
configuration file is
/etc/httpd/conf/httpd.conf
. Apply the recommendations in the remainder
of this section to this file.
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3.15.3.1. Restrict Web Server Information Leakage
The ServerTokens
and ServerSignature
directives determine how
much information the web server discloses about the configuration of the
system.
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3.15.3.1.a. Set httpd ServerTokens Directive to Prod
ServerTokens Prod
restricts information in page headers, returning only the word "Apache."
Add or correct the following directive in /etc/httpd/conf/httpd.conf
:
ServerTokens Prod
Information disclosed to clients about the configuration of the web server and system could be used to plan an attack on the given system. This information disclosure should be restricted to a minimum.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.15.3.1.b. Set httpd ServerSignature Directive to Off
ServerSignature Off
restricts httpd
from displaying server version number
on error pages.
Add or correct the following directive in /etc/httpd/conf/httpd.conf
:
ServerSignature Off
Information disclosed to clients about the configuration of the web server and system could be used to plan an attack on the given system. This information disclosure should be restricted to a minimum.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.15.3.2. Minimize Web Server Loadable Modules
A default installation of httpd
includes a plethora of dynamically shared objects (DSO)
that are loaded at run-time. Unlike the aforementioned compiled-in modules, a DSO can be
disabled in the configuration file by removing the corresponding LoadModule directive.
Note: A DSO only provides additional functionality if associated directives are included
in the httpd
configuration file. It should also be noted that removing a DSO will produce
errors on httpd
startup if the configuration file contains directives that apply to that
module. Refer to http://httpd.apache.org/docs/
for details on which directives
are associated with each DSO.
Following each DSO removal, the configuration can be tested with the following command
to check if everything still works:
$ sudo service httpd configtest
The purpose of each of the modules loaded by default will now be addressed one at a time.
If none of a module's directives are being used, remove it.
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3.15.3.2.1. httpd Core Modules
These modules comprise a basic subset of modules that are likely needed for base httpd
functionality; ensure they are not commented out in /etc/httpd/conf/httpd.conf
:
LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule authn_default_module modules/mod_authn_default.so
LoadModule authz_host_module modules/mod_authz_host.so
LoadModule authz_user_module modules/mod_authz_user.so
LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
LoadModule authz_default_module modules/mod_authz_default.so
LoadModule log_config_module modules/mod_log_config.so
LoadModule logio_module modules/mod_logio.so
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule mime_module modules/mod_mome.so
LoadModule autoindex_module modules/mod_autoindex.so
LoadModule negotiation_module modules/mod_negotiation.so
LoadModule dir_module modules/mod_dir.so
LoadModule alias_module modules/mod_alias.so
Minimizing the number of loadable modules available to the web server reduces risk
by limiting the capabilities allowed by the web server.
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3.15.3.2.1.a. Disable HTTP Digest Authentication
The auth_digest
module provides encrypted authentication sessions.
If this functionality is unnecessary, comment out the related module:
#LoadModule auth_digest_module modules/mod_auth_digest.so
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.b. Disable HTTP mod_rewrite
The mod_rewrite
module is very powerful and can protect against
certain classes of web attacks. However, it is also very complex and has a
significant history of vulnerabilities itself. If its functionality is
unnecessary, comment out the related module:
#LoadModule rewrite_module modules/mod_rewrite.so
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.c. Disable LDAP Support
The ldap
module provides HTTP authentication via an LDAP directory.
If its functionality is unnecessary, comment out the related modules:
#LoadModule ldap_module modules/mod_ldap.so
#LoadModule authnz_ldap_module modules/mod_authnz_ldap.so
If LDAP is to be used, SSL encryption should be used as well.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.d. Disable Server Side Includes
Server Side Includes provide a method of dynamically generating web pages through the insertion of server-side code. However, the technology is also deprecated and introduces significant security concerns. If this functionality is unnecessary, comment out the related module:
#LoadModule include_module modules/mod_include.so
If there is a critical need for Server Side Includes, they should be enabled with the
option IncludesNoExec
to prevent arbitrary code execution. Additionally, user
supplied data should be encoded to prevent cross-site scripting vulnerabilities.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.e. Disable MIME Magic
The mime_magic
module provides a second layer of MIME support that in most configurations
is likely extraneous. If its functionality is unnecessary, comment out the related module:
#LoadModule mime_magic_module modules/mod_mime_magic.so
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.f. Disable WebDAV (Distributed Authoring and Versioning)
WebDAV is an extension of the HTTP protocol that provides distributed and collaborative access to web content. If its functionality is unnecessary, comment out the related modules:
#LoadModule dav_module modules/mod_dav.so
#LoadModule dav_fs_module modules/mod_dav_fs.so
If there is a critical need for WebDAV, extra care should be taken in its configuration.
Since DAV access allows remote clients to manipulate server files, any location on the
server that is DAV enabled should be protected by access controls.
Minimizing the number of loadable modules available to the web server, reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.g. Disable Server Activity Status
The status
module provides real-time access to statistics on the internal operation of
the web server. This may constitute an unnecessary information leak and should be disabled
unless necessary. To do so, comment out the related module:
#LoadModule status_module modules/mod_status.so
If there is a critical need for this module, ensure that access to the status
page is properly restricted to a limited set of hosts in the status handler
configuration.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.h. Disable Web Server Configuration Display
The info
module creates a web page illustrating the configuration of the web server. This
can create an unnecessary security leak and should be disabled.
If its functionality is unnecessary, comment out the module:
#LoadModule info_module modules/mod_info.so
If there is a critical need for this module, use the Location
directive to provide
an access control list to restrict access to the information.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.i. Disable URL Correction on Misspelled Entries
The speling
module attempts to find a document match by allowing one misspelling in an
otherwise failed request. If this functionality is unnecessary, comment out the module:
#LoadModule speling_module modules/mod_speling.so
This functionality weakens server security by making site enumeration easier.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.j. Disable Proxy Support
The proxy
module provides proxying support, allowing httpd
to forward requests and
serve as a gateway for other servers. If its functionality is unnecessary, comment out the module:
#LoadModule proxy_module modules/mod_proxy.so
If proxy support is needed, load mod_proxy
and the appropriate proxy protocol handler
module (one of mod_proxy_http
, mod_proxy_ftp
, or mod_proxy_connect
). Additionally,
make certain that a server is secure before enabling proxying, as open proxy servers
are a security risk. mod_proxy_balancer
enables load balancing, but requires that
mod status
be enabled.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.k. Disable Cache Support
The cache
module allows httpd
to cache data, optimizing access to
frequently accessed content. However, it introduces potential security flaws
such as the possibility of circumventing Allow
and
Deny
directives.
If this functionality is
unnecessary, comment out the module:
#LoadModule cache_module modules/mod_cache.so
If caching is required, it should not be enabled for any limited-access content.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.l. Disable CGI Support
The cgi
module allows HTML to interact with the CGI web programming language.
If this functionality is unnecessary, comment out the module:
#LoadModule cgi_module modules/mod_cgi.so
If the web server requires the use of CGI, enable mod_cgi
.
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.2.1.13. Minimize Modules for HTTP Basic Authentication
The following modules are necessary if this web server will provide content that will
be restricted by a password.
Authentication can be performed using local plain text password files (authn_file
),
local DBM password files (authn_dbm
) or an LDAP directory. The only module required by
the web server depends on your choice of authentication. Comment out the modules you don't
need from the following:
LoadModule authn_file_module modules/mod_authn_file.so
LoadModule authn_dbm_module modules/mod_authn_dbm.so
authn_alias
allows for authentication based on aliases. authn_anon
allows anonymous authentication similar to that of anonymous ftp sites. authz_owner
allows authorization based on file ownership. authz_dbm
allows for authorization
based on group membership if the web server is using DBM authentication.
If the above functionality is unnecessary, comment out the related module:
#LoadModule authn_alias_module modules/mod_authn_alias.so
#LoadModule authn_anon_module modules/mod_authn_anon.so
#LoadModule authz_owner_module modules/mod_authz_owner.so
#LoadModule authz_dbm_module modules/mod_authz_dbm.so
3.15.3.2.1.14. Minimize Various Optional Components
The following modules perform very specific tasks, sometimes providing access to just a few additional directives. If such functionality is not required (or if you are not using these directives), comment out the associated module:
-
External filtering (response passed through external program prior to client delivery)
#LoadModule ext_filter_module modules/mod_ext_filter.so
-
User-specified Cache Control and Expiration
#LoadModule expires_module modules/mod_expires.so
-
Compression Output Filter (provides content compression prior to client delivery)
#LoadModule deflate_module modules/mod_deflate.so
-
HTTP Response/Request Header Customization
#LoadModule headers_module modules/mod_headers.so
-
User activity monitoring via cookies
#LoadModule usertrack_module modules/mod_usertrack.so
-
Dynamically configured mass virtual hosting
#LoadModule vhost_alias_module modules/mod_vhost_alias.so
Minimizing the number of loadable modules available to the web server reduces risk by limiting the capabilities allowed by the web server.
3.15.3.2.1.15. Minimize Configuration Files Included
The Include
directive directs httpd
to load supplementary configuration files
from a provided path. The default configuration loads all files that end in .conf
from the /etc/httpd/conf.d
directory.
To restrict excess configuration, the following line should be commented out and
replaced with Include
directives that only reference required configuration files:
#Include conf.d/*.conf
If the above change was made, ensure that the SSL encryption remains loaded by
explicitly including the corresponding configuration file:
Include conf.d/ssl.conf
If PHP is necessary, a similar alteration must be made:
Include conf.d/php.conf
Explicitly listing the configuration files to be loaded during web server start-up avoids
the possibility of unwanted or malicious configuration files to be automatically included as
part of the server's running configuration.
3.15.3.3. Directory Restrictions
The Directory tags in the web server configuration file allow finer grained access control for a specified directory. All web directories should be configured on a case-by-case basis, allowing access only where needed.
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3.15.3.3.a. Restrict Root Directory
The httpd
root directory should always have the most restrictive configuration enabled.
<Directory / >
Options None
AllowOverride None
Order allow,deny
</Directory>
The Web Server's root directory content should be protected from unauthorized access by web clients.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.3.b. Restrict Web Directory
The default configuration for the web (/var/www/html
) Directory allows directory
indexing (Indexes
) and the following of symbolic links (FollowSymLinks
).
Neither of these is recommended.
The /var/www/html
directory hierarchy should not be viewable via the web, and
symlinks should only be followed if the owner of the symlink also owns the linked file.
Ensure that this policy is adhered to by altering the related section of the configuration:
<Directory "/var/www/html">
# ...
Options SymLinksIfOwnerMatch
# ...
</Directory>
Access to the web server's directory hierarchy could allow access to unauthorized files by web clients. Following symbolic links could also allow such access.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.3.c. Restrict Other Critical Directories
All accessible web directories should be configured with similarly restrictive settings.
The Options
directive should be limited to necessary functionality and the AllowOverride
directive should be used only if needed. The Order
and Deny
access control tags
should be used to deny access by default, allowing access only where necessary.
Directories accessible from a web client should be configured with the least amount of access possible in order to avoid unauthorized access to restricted content or server information.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.3.d. Limit Available Methods
Web server methods are defined in section 9 of RFC 2616 (http://www.ietf.org/rfc/rfc2616.txt).
If a web server does not require the implementation of all available methods,
they should be disabled.
Note: GET
and POST
are the most common methods. A majority of the others
are limited to the WebDAV protocol.
<Directory /var/www/html>
# ...
# Only allow specific methods (this command is case-sensitive!)
<LimitExcept GET POST>
Order allow,deny
</LimitExcept>
# ...
</Directory>
Minimizing the number of available methods to the web client reduces risk by limiting the capabilities allowed by the web server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.4. Use Appropriate Modules to Improve httpd's Security
Among the modules available for httpd
are several whose use may improve the
security of the web server installation. This section recommends and discusses
the deployment of security-relevant modules.
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3.15.3.4.1. Deploy mod_ssl
Because HTTP is a plain text protocol, all traffic is susceptible to passive
monitoring. If there is a need for confidentiality, SSL should be configured
and enabled to encrypt content.
Note: mod_nss
is a FIPS 140-2 certified alternative to mod_ssl
.
The modules share a considerable amount of code and should be nearly identical
in functionality. If FIPS 140-2 validation is required, then mod_nss
should
be used. If it provides some feature or its greater compatibility is required,
then mod_ssl
should be used.
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3.15.3.4.1.a. Install mod_ssl
Install the mod_ssl
module:
$ sudo yum install mod_ssl
mod_ssl
provides encryption capabilities for the httpd
Web server. Unencrypted
content is transmitted in plain text which could be passively monitored and accessed by
unauthorized parties.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.4.2. Deploy mod_security
The security
module provides an application level firewall for httpd
.
Following its installation with the base ruleset, specific configuration advice can be found at
http://www.modsecurity.org/ to design a policy that best matches the security needs of
the web applications. Usage of mod_security
is highly recommended for some environments,
but it should be noted this module does not ship with Red Hat Enterprise Linux itself,
and instead is provided via Extra Packages for Enterprise Linux (EPEL).
For more information on EPEL please refer to http://fedoraproject.org/wiki/EPEL.
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3.15.3.4.2.a. Install mod_security
Install the security
module:
$ sudo yum install mod_security
mod_security
provides an additional level of protection for the web server by
enabling the administrator to implement content access policies and filters at the
application layer.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.5. Use Denial-of-Service Protection Modules
Denial-of-service attacks are difficult to detect and prevent while maintaining acceptable access to authorized users. However, some traffic-shaping modules can be used to address the problem. Well-known DoS protection modules include:
mod_cband mod_bwshare mod_limitipconn mod_evasive
Denial-of-service prevention should be implemented for a web server if such a threat exists.
However, specific configuration details are very dependent on the environment and often best left
at the discretion of the administrator.
3.15.3.6. Configure PHP Securely
PHP is a widely-used and often misconfigured server-side scripting language. It should
be used with caution, but configured appropriately when needed.
Review /etc/php.ini
and make the following changes if possible:
# Do not expose PHP error messages to external users
display_errors = Off
# Enable safe mode
safe_mode = On
# Only allow access to executables in isolated directory
safe_mode_exec_dir = php-required-executables-path
# Limit external access to PHP environment
safe_mode_allowed_env_vars = PHP_
# Restrict PHP information leakage
expose_php = Off
# Log all errors
log_errors = On
# Do not register globals for input data
register_globals = Off
# Minimize allowable PHP post size
post_max_size = 1K
# Ensure PHP redirects appropriately
cgi.force_redirect = 0
# Disallow uploading unless necessary
file_uploads = Off
# Disallow treatment of file requests as fopen calls
allow_url_fopen = Off
# Enable SQL safe mode
sql.safe_mode = On
3.15.3.7. Configure Operating System to Protect Web Server
The following configuration steps should be taken on the machine which hosts the web server, in order to provide as safe an environment as possible for the web server.
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3.15.3.7.1. Restrict File and Directory Access
Minimize access to critical httpd
files and directories.
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3.15.3.7.1.a. Set Permissions on the /var/log/httpd/ Directory
Ensure that the permissions on the web server log directory is set to 700:
$ sudo chmod 700 /var/log/httpd/
This is its default setting.
Access to the web server's log files may allow an unauthorized user or attacker to access information about the web server or alter the server's log files.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.15.3.7.1.b. Set Permissions on the /etc/httpd/conf/ Directory
Set permissions on the web server configuration directory to 750:
$ sudo chmod 750 /etc/httpd/conf/
Access to the web server's configuration files may allow an unauthorized user or attacker to access information about the web server or alter the server's configuration files.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.15.3.7.1.c. Set Permissions on All Configuration Files Inside /etc/httpd/conf/
Set permissions on the web server configuration files to 640:
$ sudo chmod 640 /etc/httpd/conf/*
Access to the web server's configuration files may allow an unauthorized user or attacker to access information about the web server or to alter the server's configuration files.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
3.15.3.7.2. Configure firewalld to Allow Access to the Web Server
By default, firewalld
blocks access to the ports used by the web server.
To configure firewalld
to allow access, run the following command(s):
firewall-cmd --permanent --add-service=http
To configure firewalld
to allow access, run the following command(s):
firewall-cmd --permanent --add-service=https
3.15.3.7.3. Run httpd in a chroot Jail if Practical
Running httpd
inside a chroot
jail is designed to isolate the
web server process to a small section of the filesystem, limiting the damage if
it is compromised. Versions of Apache greater than 2.2.10 (such as the one
included with Red Hat Enterprise Linux 7) provide the ChrootDir
directive. To run Apache
inside a chroot jail in /chroot/apache
, add the following line to
/etc/httpd/conf/httpd.conf
:
ChrootDir /chroot/apache
This
necessitates placing all files required by httpd
inside
/chroot/apache
, including httpd
's binaries, modules,
configuration files, and served web pages. The details of this configuration
are beyond the scope of this guide. This may also require additional SELinux
configuration.
3.16. IMAP and POP3 Server
Dovecot provides IMAP and POP3 services. It is not installed by default. The project page at http://www.dovecot.org contains more detailed information about Dovecot configuration.
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3.16.1. Disable Dovecot
If the system does not need to operate as an IMAP or POP3 server, the dovecot software should be disabled and removed.
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3.16.1.a. Disable Dovecot Service
The dovecot
service can be disabled with the following command:
$ sudo systemctl disable dovecot
Running an IMAP or POP3 server provides a network-based avenue of attack, and should be disabled if not needed.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.16.1.b. Uninstall dovecot Package
The dovecot
package can be uninstalled
with the following command:
$ sudo yum erase dovecot
If there is no need to make the Dovecot software available, removing it provides a safeguard against its activation.
Remediation script
if rpm -qa | grep -q dovecot; then
yum -y remove dovecot
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
3.16.2. Configure Dovecot if Necessary
If the system will operate as an IMAP or POP3 server, the dovecot software should be configured securely by following the recommendations below.
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3.16.2.1. Support Only the Necessary Protocols
Dovecot supports the IMAP and POP3 protocols, as well as
SSL-protected versions of those protocols. Configure the Dovecot server
to support only the protocols needed by your site. Edit /etc/dovecot/dovecot.conf
.
Add or correct the following lines, replacing PROTOCOL
with
only the subset of protocols (imap
, imaps
,
pop3
, pop3s
) required:
protocols = PROTOCOL
If possible, require SSL protection for all transactions. The SSL
protocol variants listen on alternate ports (995 instead of 110 for
pop3s, and 993 instead of 143 for imaps), and require SSL-aware clients.
An alternate approach is to listen on the standard port and require the
client to use the STARTTLS command before authenticating.
Configuring Dovecot to only support the protocols the protocols needed by your site reduces the risk of an attacker using one of the unused protocols to base an attack.
3.16.2.2. Enable SSL Support
SSL should be used to encrypt network traffic between the Dovecot server and its clients. Users must authenticate to the Dovecot server in order to read their mail, and passwords should never be transmitted in clear text. In addition, protecting mail as it is downloaded is a privacy measure, and clients may use SSL certificates to authenticate the server, preventing another system from impersonating the server.
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3.16.2.2.a. Enable the SSL flag in /etc/dovecot.conf
To allow clients to make encrypted connections the ssl
flag in Dovecot's configuration file needs to be set to yes
.
Edit /etc/dovecot/conf.d/10-ssl.conf
and add or correct the following line:
ssl = yes
SSL encrypt network traffic between the Dovecot server and its clients protecting user credentials, mail as it is downloaded, and clients may use SSL certificates to authenticate the server, preventing another system from impersonating the server.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.16.2.2.b. Configure Dovecot to Use the SSL Certificate file
This option tells Dovecot where to find the the mail
server's SSL Certificate.
Edit /etc/dovecot/conf.d/10-ssl.conf
and add or correct the following
line (note: the path below is the default path set by the Dovecot installation. If
you are using a different path, ensure you reference the appropriate file):
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
SSL certificates are used by the client to authenticate the identity of the server, as well as to encrypt credentials and message traffic. Not using SSL to encrypt mail server traffic could allow unauthorized access to credentials and mail messages since they are sent in plain text over the network.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.16.2.2.c. Configure Dovecot to Use the SSL Key file
This option tells Dovecot where to find the the mail
server's SSL Key.
Edit /etc/dovecot/conf.d/10-ssl.conf
and add or correct the following
line (note: the path below is the default path set by the Dovecot installation. If
you are using a different path, ensure you reference the appropriate file):
ssl_key = </etc/pki/dovecot/private/dovecot.pem
SSL certificates are used by the client to authenticate the identity of the server, as well as to encrypt credentials and message traffic. Not using SSL to encrypt mail server traffic could allow unauthorized access to credentials and mail messages since they are sent in plain text over the network.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.16.2.2.d. Disable Plaintext Authentication
To prevent Dovecot from attempting plaintext
authentication of clients, edit /etc/dovecot/conf.d/10-auth.conf
and add
or correct the following line:
disable_plaintext_auth = yes
Using plain text authentication to the mail server could allow an attacker access to credentials by monitoring network traffic.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.16.2.3. Allow IMAP Clients to Access the Server
The default firewalld
configuration does not allow inbound
access to any services. This modification will allow remote hosts to
initiate connections to the IMAP daemon, while keeping all other ports
on the server in their default protected state.
To configure firewalld
to allow access, run the following command(s):
firewall-cmd --permanent --add-port=143/tcp
and
3.17. Samba(SMB) Microsoft Windows File Sharing Server
When properly configured, the Samba service allows
Linux machines to provide file and print sharing to Microsoft
Windows machines. There are two software packages that provide
Samba support. The first, samba-client
, provides a series of
command line tools that enable a client machine to access Samba
shares. The second, simply labeled samba
, provides the Samba
service. It is this second package that allows a Linux machine to
act as an Active Directory server, a domain controller, or as a
domain member. Only the samba-client
package is installed by
default.
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3.17.1. Disable Samba if Possible
Even after the Samba server package has been installed, it will remain disabled. Do not enable this service unless it is absolutely necessary to provide Microsoft Windows file and print sharing functionality.
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3.17.1.a. Disable Samba
The smb
service can be disabled with the following command:
$ sudo systemctl disable smb
Running a Samba server provides a network-based avenue of attack, and should be disabled if not needed.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- 1436. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
3.17.2. Configure Samba if Necessary
All settings for the Samba daemon can be found in
/etc/samba/smb.conf
. Settings are divided between a
[global]
configuration section and a series of user
created share definition sections meant to describe file or print
shares on the system. By default, Samba will operate in user mode
and allow client machines to access local home directories and
printers. It is recommended that these settings be changed or that
additional limitations be set in place.
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3.17.2.a. Disable Root Access to SMB Shares
Administrators should not use administrator accounts to access Samba file and printer shares. Disable the root user and the wheel administrator group:
[share]
invalid users = root @wheel
If administrator accounts cannot be disabled, ensure that local machine
passwords and Samba service passwords do not match.
Typically, administrator access is required when Samba must create user and
machine accounts and shares. Domain member servers and standalone servers may
not need administrator access at all. If that is the case, add the invalid
users parameter to [global]
instead.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.17.2.b. Require Client SMB Packet Signing, if using smbclient
To require samba clients running smbclient
to use
packet signing, add the following to the [global]
section
of the Samba configuration file, /etc/samba/smb.conf
:
client signing = mandatory
Requiring samba clients such as smbclient
to use packet
signing ensures they can
only communicate with servers that support packet signing.
Packet signing can prevent man-in-the-middle attacks which modify SMB packets in transit.
Remediation script
######################################################################
#By Luke "Brisk-OH" Brisk
#luke.brisk@boeing.com or luke.brisk@gmail.com
######################################################################
CLIENTSIGNING=$( grep -ic 'client signing' /etc/samba/smb.conf )
if [ "$CLIENTSIGNING" -eq 0 ]; then
# Add to global section
sed -i 's/\[global\]/\[global\]\n\n\tclient signing = mandatory/g' /etc/samba/smb.conf
else
sed -i 's/[[:blank:]]*client[[:blank:]]signing[[:blank:]]*=[[:blank:]]*no/ client signing = mandatory/g' /etc/samba/smb.conf
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
3.17.2.c. Require Client SMB Packet Signing, if using mount.cifs
Require packet signing of clients who mount Samba
shares using the mount.cifs
program (e.g., those who specify shares
in /etc/fstab
). To do so, ensure signing options (either
sec=krb5i
or sec=ntlmv2i
) are used.
See the mount.cifs(8)
man page for more information. A Samba
client should only communicate with servers who can support SMB
packet signing.
Packet signing can prevent man-in-the-middle attacks which modify SMB packets in transit.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.17.2.4. Restrict SMB File Sharing to Configured Networks
Only users with local user accounts will be able to log in to
Samba shares by default. Shares can be limited to particular users or network
addresses. Use the hosts allow
and hosts deny
directives
accordingly, and consider setting the valid users directive to a limited subset
of users or to a group of users. Separate each address, user, or user group
with a space as follows for a particular share or global:
[share]
hosts allow = 192.168.1. 127.0.0.1
valid users = userone usertwo @usergroup
It is also possible to limit read and write access to particular users with the
read list and write list options, though the permissions set by the system
itself will override these settings. Set the read only attribute for each share
to ensure that global settings will not accidentally override the individual
share settings. Then, as with the valid users directive, separate each user or
group of users with a space:
[share]
read only = yes
write list = userone usertwo @usergroup
The Samba service is only required for sharing files and printers with Microsoft Windows workstations, and even then, other options may exist.
3.17.2.5. Restrict Printer Sharing
By default, Samba utilizes the CUPS printing service to enable
printer sharing with Microsoft Windows workstations. If there are no printers
on the local machine, or if printer sharing with Microsoft Windows is not
required, disable the printer sharing capability by commenting out the
following lines, found in /etc/samba/smb.conf
:
[global]
load printers = yes
cups options = raw
[printers]
comment = All Printers
path = /usr/spool/samba
browseable = no
guest ok = no
writable = no
printable = yes
There may be other options present, but these are the only options enabled and
uncommented by default. Removing the [printers]
share should be enough
for most users. If the Samba printer sharing capability is needed, consider
disabling the Samba network browsing capability or restricting access to a
particular set of users or network addresses. Set the valid users
parameter to a small subset of users or restrict it to a particular group of
users with the shorthand @
. Separate each user or group of users with
a space. For example, under the [printers]
share:
[printers]
valid users = user @printerusers
The Samba service is only required for sharing files and printers with Microsoft Windows workstations, and even then, other options may exist. Do not use the Samba service to share files between Unix or Linux machines.
3.18. Proxy Server
A proxy server is a very desirable target for a potential adversary because much (or all) sensitive data for a given infrastructure may flow through it. Therefore, if one is required, the machine acting as a proxy server should be dedicated to that purpose alone and be stored in a physically secure location. The system's default proxy server software is Squid, and provided in an RPM package of the same name.
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3.18.1. Disable Squid if Possible
If Squid was installed and activated, but the system does not need to act as a proxy server, then it should be disabled and removed.
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3.18.1.a. Disable Squid
The squid
service can be disabled with the following command:
$ sudo systemctl disable squid
Running proxy server software provides a network-based avenue of attack, and should be removed if not needed.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.18.1.b. Uninstall squid Package
The squid
package can be removed with the following command:
$ sudo yum erase squid
If there is no need to make the proxy server software available, removing it provides a safeguard against its activation.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.19. SNMP Server
The Simple Network Management Protocol allows administrators to monitor the state of network devices, including computers. Older versions of SNMP were well-known for weak security, such as plaintext transmission of the community string (used for authentication) and usage of easily-guessable choices for the community string.
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3.19.1. Disable SNMP Server if Possible
The system includes an SNMP daemon that allows for its remote monitoring, though it not installed by default. If it was installed and activated but is not needed, the software should be disabled and removed.
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3.19.1.a. Disable snmpd Service
The snmpd
service can be disabled with the following command:
$ sudo systemctl disable snmpd
Running SNMP software provides a network-based avenue of attack, and should be disabled if not needed.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.19.1.b. Uninstall net-snmp Package
The net-snmp
package provides the snmpd service.
The net-snmp
package can be removed with the following command:
$ sudo yum erase net-snmp
If there is no need to run SNMP server software, removing the package provides a safeguard against its activation.
Remediation script
if rpm -qa | grep -q net-snmp; then
yum -y remove net-snmp
fi
Security identifiers
- CCE-RHEL7-CCE-TBD
3.19.2. Configure SNMP Server if Necessary
If it is necessary to run the snmpd agent on the system, some best practices should be followed to minimize the security risk from the installation. The multiple security models implemented by SNMP cannot be fully covered here so only the following general configuration advice can be offered:
-
use only SNMP version 3 security models and enable the use of authentication and encryption
-
write access to the MIB (Management Information Base) should be allowed only if necessary
-
all access to the MIB should be restricted following a principle of least privilege
-
network access should be limited to the maximum extent possible including restricting to expected network addresses both in the configuration files and in the system firewall rules
-
ensure SNMP agents send traps only to, and accept SNMP queries only from, authorized management stations
-
ensure that permissions on the
snmpd.conf
configuration file (by default, in/etc/snmp
) are 640 or more restrictive -
ensure that any MIB files' permissions are also 640 or more restrictive
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3.19.2.a. Configure SNMP Service to Use Only SNMPv3 or Newer
Edit /etc/snmp/snmpd.conf
, removing any references to rocommunity
, rwcommunity
, or com2sec
.
Upon doing that, restart the SNMP service:
$ sudo service snmpd restart
Earlier versions of SNMP are considered insecure, as they potentially allow unauthorized access to detailed system management information.
Security identifiers
- CCE-RHEL7-CCE-TBD
3.19.2.b. Ensure Default Password Is Not Used
Edit /etc/snmp/snmpd.conf
, remove default community string public
.
Upon doing that, restart the SNMP service:
$ sudo service snmpd restart
Presence of the default SNMP password enables querying of different system aspects and could result in unauthorized knowledge of the system.
Security identifiers
- CCE-RHEL7-CCE-TBD
References
- Test attestation on 20121214 by MAN. URL: <https://github.com/OpenSCAP/scap-security-guide/wiki/Contributors>.
4. Documentation to Support DISA OS SRG Mapping
These groups exist to document how the Red Hat Enterprise Linux product meets (or does not meet) requirements listed in the DISA OS SRG, for those cases where Groups or Rules elsewhere in scap-security-guide do not clearly relate.
Table of Contents
- 4.a. Product Meets this Requirement
- 4.b. Product Meets this Requirement
- 4.c. Product Meets this Requirement
- 4.d. Guidance Does Not Meet this Requirement Due to Impracticality or Scope
- 4.e. Implementation of the Requirement is Not Supported
- 4.f. Guidance Does Not Meet this Requirement Due to Impracticality or Scope
- 4.g. A process for prompt installation of OS updates must exist.
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4.a. Product Meets this Requirement
This requirement is a permanent not a finding. No fix is required.
Red Hat Enterprise Linux meets this requirement through design and implementation.
References
- 42. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 56. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 206. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1084. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 66. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 85. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 86. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 185. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 223. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 171. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 172. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1694. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 770. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 804. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 162. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 163. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 164. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 345. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 346. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1096. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1111. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1291. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 386. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 156. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 186. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1083. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1082. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1090. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 804. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1127. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1128. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1129. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1248. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1265. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1314. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1362. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1368. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1310. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1311. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1328. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1399. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1400. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1404. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1405. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1427. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1499. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1632. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1693. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1665. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1674. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
4.b. Product Meets this Requirement
This requirement is a permanent not a finding. No fix is required.
The Red Hat Enterprise Linux audit system meets this requirement through design and implementation.
References
- 130. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 157. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 131. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 132. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 133. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 134. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 135. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 159. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 174. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
4.c. Product Meets this Requirement
This requirement is a permanent not a finding. No fix is required.
Red Hat Enterprise Linux meets this requirement through design and implementation.
References
- 34. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 35. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 99. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 154. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 226. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 802. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 872. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1086. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1087. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1089. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1091. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1424. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1426. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1428. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1209. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1214. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1237. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1269. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1338. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1425. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1670. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
4.d. Guidance Does Not Meet this Requirement Due to Impracticality or Scope
This requirement is NA. No fix is required.
The guidance does not meet this requirement. The requirement is impractical or out of scope.
References
- 21. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 25. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 28. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 29. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 30. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 165. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 221. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 354. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 553. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 779. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 780. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 781. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1009. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1094. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1123. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1124. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1125. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1132. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1135. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1140. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1141. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1142. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1143. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1145. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1147. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1148. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1166. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1339. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1340. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1341. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1350. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1356. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1373. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1374. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1383. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1391. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1392. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1395. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1662. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
4.e. Implementation of the Requirement is Not Supported
This requirement is a permanent finding and cannot be fixed. An appropriate mitigation for the system must be implemented but this finding cannot be considered fixed.
RHEL7 does not support this requirement.
References
- 20. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 31. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 52. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 144. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1158. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1294. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1295. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1500. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
4.f. Guidance Does Not Meet this Requirement Due to Impracticality or Scope
This requirement is NA. No fix is required.
The guidance does not meet this requirement. The requirement is impractical or out of scope.
References
- 15. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 27. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 218. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 219. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 371. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 372. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 535. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 537. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 539. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1682. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 370. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 37. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 24. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1112. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1126. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1143. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1149. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1157. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1159. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1210. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1211. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1274. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1372. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1376. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1377. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1352. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1401. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1555. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1556. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
- 1150. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
4.g. A process for prompt installation of OS updates must exist.
Procedures to promptly apply software updates must be established and executed. The Red Hat operating system provides support for automating such a process, by running the yum program through a cron job or by managing the system and its packages through the Red Hat Network or a Satellite Server.
This is a manual inquiry about update procedure.
References
- 1232. URL: <http://iase.disa.mil/stigs/cci/Pages/index.aspx>.
Rule Selection
Based on profile: Standard System Security Profile (standard)
This profile contains rules to ensure standard security base of Red Hat Enterprise Linux 7 system.
Colophon
Red Hat and Red Hat Enterprise Linux are either registered trademarks or trademarks of Red Hat, Inc. in the United States and other countries. All other names are registered trademarks or trademarks of their respective companies.