class SymmetricEncryption::Reader
Read from encrypted files and other IO streams
Features:
-
Decryption on the fly whilst reading files
-
Large file support by only buffering small amounts of data in memory
Attributes
Return the number of bytes read so far from the input stream
Returns the Cipher
encryption version used to encrypt this file Returns nil when the header was not present in the stream and no :version
option was supplied
Note: When no header is present, the version is set to the one supplied
in the options
Public Class Methods
Decrypt an entire file.
Returns [Integer] the number of unencrypted bytes written to the target file.
Params:
source: [String|IO] Source file_name or IOStream target: [String|IO] Target file_name or IOStream
Notes:
-
The file contents are streamed so that the entire file is not loaded into memory.
# File lib/symmetric_encryption/reader.rb, line 95 def self.decrypt(source:, target:, **args) Reader.open(source, **args) { |input_file| IO.copy_stream(input_file, target) } end
Returns [true|false] whether the file or stream contains any data excluding the header should it have one
# File lib/symmetric_encryption/reader.rb, line 101 def self.empty?(file_name_or_stream) open(file_name_or_stream, &:eof?) end
Returns [true|false] whether the file contains the encryption header
# File lib/symmetric_encryption/reader.rb, line 106 def self.header_present?(file_name) ::File.open(file_name, "rb") { |file| new(file).header_present? } end
Decrypt data before reading from the supplied stream
# File lib/symmetric_encryption/reader.rb, line 117 def initialize(ios, buffer_size: 4096, version: nil) @ios = ios @buffer_size = buffer_size @version = version @header_present = false @closed = false @read_buffer = "".b raise(ArgumentError, "Buffer size cannot be smaller than 128") unless @buffer_size >= 128 read_header end
Open a file for reading, or use the supplied IO Stream
Parameters:
file_name_or_stream: The file_name to open if a string, otherwise the stream to use The file or stream will be closed on completion, use .initialize to avoid having the stream closed automatically buffer_size: Amount of data to read at a time. Minimum Value 128 Default: 16384
Note: Decryption occurs before decompression
# Example: Read and decrypt a line at a time from a file SymmetricEncryption::Reader.open
('test_file') do |file|
file.each_line {|line| p line }
end
# Example: Read and decrypt entire file in memory # Not recommended for large files SymmetricEncryption::Reader.open
('test_file') {|f| f.read }
# Example: Reading a limited number of bytes at a time from the file SymmetricEncryption::Reader.open
('test_file') do |file|
file.read(1) file.read(5) file.read
end
# Example: Read and decrypt 5 bytes at a time until the end of file is reached SymmetricEncryption::Reader.open
('test_file') do |file|
while !file.eof? do file.read(5) end
end
# Example: Read, Unencrypt and decompress data in a file SymmetricEncryption::Reader.open
('encrypted_compressed.zip', compress: true) do |file|
file.each_line {|line| p line }
end
# Example: Reading from a CSV file
require 'csv' begin
csv = CSV.new(SymmetricEncryption::Reader.open('csv_encrypted')) csv.each {|row| p row}
ensure
csv.close if csv
end
# File lib/symmetric_encryption/reader.rb, line 62 def self.open(file_name_or_stream, buffer_size: 16_384, **args, &block) ios = file_name_or_stream.is_a?(String) ? ::File.open(file_name_or_stream, "rb") : file_name_or_stream begin file = new(ios, buffer_size: buffer_size, **args) file = Zlib::GzipReader.new(file) if !file.eof? && file.compressed? block ? block.call(file) : file ensure file.close if block && file && (file.respond_to?(:closed?) && !file.closed?) end end
Read the entire contents of a file or stream into memory.
Notes:
-
Do not use this method for reading large files.
# File lib/symmetric_encryption/reader.rb, line 78 def self.read(file_name_or_stream, **args) Reader.open(file_name_or_stream, **args, &:read) end
Public Instance Methods
Close the IO Stream
Note: Also closes the passed in io stream or file
It is recommended to call Symmetric::EncryptedStream.open or Symmetric::EncryptedStream.io rather than creating an instance of Symmetric::EncryptedStream directly to ensure that the encrypted stream is closed before the stream itself is closed
# File lib/symmetric_encryption/reader.rb, line 160 def close(close_child_stream = true) return if closed? @ios.close if close_child_stream @closed = true end
Returns whether the stream being read is compressed
Should be called before any reads are performed to determine if the file or stream is compressed.
Returns true when the header is present in the stream and it is compressed Returns false when the header is present in the stream and it is not compressed Returns nil when the header is not present in the stream
Note: The file will not be decompressed automatically when compressed.
To decompress the data automatically call SymmetricEncryption.open
# File lib/symmetric_encryption/reader.rb, line 141 def compressed? @compressed end
ios.each(sep_string=ānā) {|line| block } => ios ios.each_line(sep_string=ānā) {|line| block } => ios Executes the block for every line in ios, where lines are separated by sep_string. ios must be opened for reading or an IOError will be raised.
# File lib/symmetric_encryption/reader.rb, line 240 def each_line(sep_string = "\n") yield gets(sep_string) until eof? self end
Returns whether the end of file has been reached for this stream
# File lib/symmetric_encryption/reader.rb, line 248 def eof? @read_buffer.empty? && @ios.eof? end
Flush the read stream
Needed by XLS gem
# File lib/symmetric_encryption/reader.rb, line 169 def flush @ios.flush end
Reads a single decrypted line from the file up to and including the optional sep_string. A sep_string of nil reads the entire contents of the file Returns nil on eof The stream must be opened for reading or an IOError will be raised.
# File lib/symmetric_encryption/reader.rb, line 219 def gets(sep_string, length = nil) return read(length) if sep_string.nil? # Read more data until we get the sep_string while (index = @read_buffer.index(sep_string)).nil? && !@ios.eof? break if length && @read_buffer.length >= length read_block end index ||= -1 data = @read_buffer.slice!(0..index) @pos += data.length return nil if data.empty? && eof? data end
After opening a file Returns [true|false] whether the file being read has an encryption header
# File lib/symmetric_encryption/reader.rb, line 112 def header_present? @header_present end
Read from the stream and return the decrypted data See IOS#read
Reads at most length bytes from the I/O stream, or to the end of file if length is omitted or is nil. length must be a non-negative integer or nil.
At end of file, it returns nil if no more data is available, or the last remaining bytes
# File lib/symmetric_encryption/reader.rb, line 187 def read(length = nil, outbuf = nil) data = outbuf.nil? ? "" : outbuf.clear remaining_length = length until remaining_length&.zero? || eof? read_block(remaining_length) if @read_buffer.empty? if remaining_length && remaining_length < @read_buffer.length data << @read_buffer.slice!(0, remaining_length) else data << @read_buffer @read_buffer.clear end remaining_length = length - data.length if length end @pos += data.length data unless data.empty? && length && length.positive? end
Reads a single decrypted line from the file up to and including the optional sep_string. Raises EOFError on eof The stream must be opened for reading or an IOError will be raised.
# File lib/symmetric_encryption/reader.rb, line 211 def readline(sep_string = "\n") gets(sep_string) || raise(EOFError, "End of file reached when trying to read a line") end
Rewind back to the beginning of the file
# File lib/symmetric_encryption/reader.rb, line 256 def rewind @read_buffer.clear @ios.rewind read_header end
Seeks to a given offset (Integer) in the stream according to the value of whence:
IO::SEEK_CUR | Seeks to _amount_ plus current position --------------+---------------------------------------------------- IO::SEEK_END | Seeks to _amount_ plus end of stream (you probably | want a negative value for _amount_) --------------+---------------------------------------------------- IO::SEEK_SET | Seeks to the absolute location given by _amount_
WARNING: IO::SEEK_SET will jump to the beginning of the file and
then re-read upto the point specified
WARNING: IO::SEEK_END will read the entire file and then again
upto the point specified
# File lib/symmetric_encryption/reader.rb, line 274 def seek(amount, whence = IO::SEEK_SET) offset = 0 case whence when IO::SEEK_SET offset = amount rewind when IO::SEEK_CUR if amount >= 0 offset = amount else offset = @pos + amount rewind end when IO::SEEK_END rewind # Read and decrypt entire file a block at a time to get its total # unencrypted size size = 0 until eof? read_block size += @read_buffer.size @read_buffer.clear end rewind offset = size + amount else raise(ArgumentError, "unknown whence:#{whence} supplied to seek()") end read(offset) if offset.positive? 0 end
Return the size of the file rounded up to the nearest encryption block size
Needed by XLS gem
# File lib/symmetric_encryption/reader.rb, line 175 def size @ios.size end
Private Instance Methods
# File lib/symmetric_encryption/reader.rb, line 364 def closed? @closed || @ios.respond_to?(:closed?) && @ios.closed? end
# File lib/symmetric_encryption/reader.rb, line 349 def decrypt(buf) return if buf.nil? || buf.empty? @read_buffer << @stream_cipher.update(buf) @read_buffer << @stream_cipher.final if @ios.eof? end
Read a block of data and append the decrypted data in the read buffer
# File lib/symmetric_encryption/reader.rb, line 342 def read_block(length = nil) buf = @ios.read(length || @buffer_size, @output_buffer ||= "".b) decrypt(buf) end
Read the header from the file if present
# File lib/symmetric_encryption/reader.rb, line 309 def read_header @pos = 0 # Read first block and check for the header buf = @ios.read(@buffer_size, @output_buffer ||= "".b) # Use cipher specified in header, or global cipher if it has no header iv, key, cipher_name, cipher = nil header = Header.new if header.parse!(buf) @header_present = true @compressed = header.compressed? @version = header.version cipher = header.cipher cipher_name = header.cipher_name || cipher.cipher_name key = header.key iv = header.iv else @header_present = false @compressed = nil cipher = SymmetricEncryption.cipher(@version) cipher_name = cipher.cipher_name end @stream_cipher = ::OpenSSL::Cipher.new(cipher_name) @stream_cipher.decrypt @stream_cipher.key = key || cipher.send(:key) @stream_cipher.iv = iv || cipher.iv decrypt(buf) end