class Aws::Sigv4::Signer
Utility class for creating AWS signature version 4 signature. This class provides two methods for generating signatures:
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{#sign_request} - Computes a signature of the given request, returning the hash of headers that should be applied to the request.
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{#presign_url} - Computes a presigned request with an expiration. By default, the body of this request is not signed and the request expires in 15 minutes.
## Configuration
To use the signer, you need to specify the service, region, and credentials. The service name is normally the endpoint prefix to an AWS service. For example:
ec2.us-west-1.amazonaws.com => ec2
The region is normally the second portion of the endpoint, following the service name.
ec2.us-west-1.amazonaws.com => us-west-1
It is important to have the correct service and region name, or the signature will be invalid.
## Credentials
The signer requires credentials. You can configure the signer with static credentials:
signer = Aws::Sigv4::Signer.new( service: 's3', region: 'us-east-1', # static credentials access_key_id: 'akid', secret_access_key: 'secret' )
You can also provide refreshing credentials via the ‘:credentials_provider`. If you are using the AWS SDK for Ruby, you can use any of the credential classes:
signer = Aws::Sigv4::Signer.new( service: 's3', region: 'us-east-1', credentials_provider: Aws::InstanceProfileCredentials.new )
Other AWS SDK for Ruby classes that can be provided via ‘:credentials_provider`:
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‘Aws::Credentials`
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‘Aws::SharedCredentials`
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‘Aws::InstanceProfileCredentials`
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‘Aws::AssumeRoleCredentials`
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‘Aws::ECSCredentials`
A credential provider is any object that responds to ‘#credentials` returning another object that responds to `#access_key_id`, `#secret_access_key`, and `#session_token`.
Attributes
@return [Boolean] When ‘true` the `x-amz-content-sha256` header will be signed and
returned in the signature headers.
@return [#credentials] Returns an object that responds to
`#credentials`, returning an object that responds to the following methods: * `#access_key_id` => String * `#secret_access_key` => String * `#session_token` => String, nil * `#set?` => Boolean
@return [String]
@return [String]
@return [Set<String>] Returns a set of header names that should not be signed.
All header names have been downcased.
Public Class Methods
@overload initialize(service:, region:, access_key_id:, secret_access_key:, session_token:nil, **options)
@param [String] :service The service signing name, e.g. 's3'. @param [String] :region The region name, e.g. 'us-east-1'. @param [String] :access_key_id @param [String] :secret_access_key @param [String] :session_token (nil)
@overload initialize(service:, region:, credentials:, **options)
@param [String] :service The service signing name, e.g. 's3'. @param [String] :region The region name, e.g. 'us-east-1'. @param [Credentials] :credentials Any object that responds to the following methods: * `#access_key_id` => String * `#secret_access_key` => String * `#session_token` => String, nil * `#set?` => Boolean
@overload initialize(service:, region:, credentials_provider
:, **options)
@param [String] :service The service signing name, e.g. 's3'. @param [String] :region The region name, e.g. 'us-east-1'. @param [#credentials] :credentials_provider An object that responds to `#credentials`, returning an object that responds to the following methods: * `#access_key_id` => String * `#secret_access_key` => String * `#session_token` => String, nil * `#set?` => Boolean
@option options [Array<String>] :unsigned_headers ([]) A list of
headers that should not be signed. This is useful when a proxy modifies headers, such as 'User-Agent', invalidating a signature.
@option options [Boolean] :uri_escape_path (true) When ‘true`,
the request URI path is uri-escaped as part of computing the canonical request string. This is required for every service, except Amazon S3, as of late 2016.
@option options [Boolean] :apply_checksum_header (true) When ‘true`,
the computed content checksum is returned in the hash of signature headers. This is required for AWS Glacier, and optional for every other AWS service as of late 2016.
# File lib/aws-sigv4/signer.rb, line 118 def initialize(options = {}) @service = extract_service(options) @region = extract_region(options) @credentials_provider = extract_credentials_provider(options) @unsigned_headers = Set.new((options.fetch(:unsigned_headers, [])).map(&:downcase)) @unsigned_headers << 'authorization' @unsigned_headers << 'x-amzn-trace-id' [:uri_escape_path, :apply_checksum_header].each do |opt| instance_variable_set("@#{opt}", options.key?(opt) ? !!options[:opt] : true) end end
Private Class Methods
@api private
# File lib/aws-sigv4/signer.rb, line 586 def uri_escape(string) if string.nil? nil else CGI.escape(string.encode('UTF-8')).gsub('+', '%20').gsub('%7E', '~') end end
@api private
# File lib/aws-sigv4/signer.rb, line 581 def uri_escape_path(path) path.gsub(/[^\/]+/) { |part| uri_escape(part) } end
Public Instance Methods
Signs a URL with query authentication. Using query parameters to authenticate requests is useful when you want to express a request entirely in a URL. This method is also referred as presigning a URL.
See [Authenticating Requests: Using Query Parameters (AWS Signature
Version 4)](docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html) for more information.
To generate a presigned URL, you must provide a HTTP URI and the http method.
url = signer.presigned_url( http_method: 'GET', url: 'https://my-bucket.s3-us-east-1.amazonaws.com/key', expires_in: 60 )
By default, signatures are valid for 15 minutes. You can specify the number of seconds for the URL to expire in.
url = signer.presigned_url( http_method: 'GET', url: 'https://my-bucket.s3-us-east-1.amazonaws.com/key', expires_in: 3600 # one hour )
You can provide a hash of headers that you plan to send with the request. Every ‘X-Amz-*’ header you plan to send with the request must be provided, or the signature is invalid. Other headers are optional, but should be provided for security reasons.
url = signer.presigned_url( http_method: 'PUT', url: 'https://my-bucket.s3-us-east-1.amazonaws.com/key', headers: { 'X-Amz-Meta-Custom' => 'metadata' } )
@option options [required, String] :http_method The HTTP request method,
e.g. 'GET', 'HEAD', 'PUT', 'POST', 'PATCH', or 'DELETE'.
@option options [required, String, HTTPS::URI, HTTP::URI] :url
The URI to sign.
@option options [Hash] :headers ({}) Headers that should
be signed and sent along with the request. All x-amz-* headers must be present during signing. Other headers are optional.
@option options [Integer<Seconds>] :expires_in (900)
How long the presigned URL should be valid for. Defaults to 15 minutes (900 seconds).
@option options [optional, String, IO] :body
If the `:body` is set, then a SHA256 hexdigest will be computed of the body. If `:body_digest` is set, this option is ignored. If neither are set, then the `:body_digest` will be computed of the empty string.
@option options [optional, String] :body_digest
The SHA256 hexdigest of the request body. If you wish to send the presigned request without signing the body, you can pass 'UNSIGNED-PAYLOAD' as the `:body_digest` in place of passing `:body`.
@option options [Time] :time (Time.now) Time of the signature.
You should only set this value for testing.
@return [HTTPS::URI, HTTP::URI]
# File lib/aws-sigv4/signer.rb, line 314 def presign_url(options) creds = get_credentials http_method = extract_http_method(options) url = extract_url(options) headers = downcase_headers(options[:headers]) headers['host'] = host(url) datetime = headers['x-amz-date'] datetime ||= (options[:time] || Time.now).utc.strftime("%Y%m%dT%H%M%SZ") date = datetime[0,8] content_sha256 = headers['x-amz-content-sha256'] content_sha256 ||= options[:body_digest] content_sha256 ||= sha256_hexdigest(options[:body] || '') params = {} params['X-Amz-Algorithm'] = 'AWS4-HMAC-SHA256' params['X-Amz-Credential'] = credential(creds, date) params['X-Amz-Date'] = datetime params['X-Amz-Expires'] = extract_expires_in(options) params['X-Amz-SignedHeaders'] = signed_headers(headers) params['X-Amz-Security-Token'] = creds.session_token if creds.session_token params = params.map do |key, value| "#{uri_escape(key)}=#{uri_escape(value)}" end.join('&') if url.query url.query += '&' + params else url.query = params end creq = canonical_request(http_method, url, headers, content_sha256) sts = string_to_sign(datetime, creq) url.query += '&X-Amz-Signature=' + signature(creds.secret_access_key, date, sts) url end
Computes a version 4 signature signature. Returns the resultant signature as a hash of headers to apply to your HTTP request. The given request is not modified.
signature = signer.sign_request( http_method: 'PUT', url: 'https://domain.com', headers: { 'Abc' => 'xyz', }, body: 'body' # String or IO object ) # Apply the following hash of headers to your HTTP request signature.headers['Host'] signature.headers['X-Amz-Date'] signature.headers['X-Amz-Security-Token'] signature.headers['X-Amz-Content-Sha256'] signature.headers['Authorization']
In addition to computing the signature headers, the canonicalized request, string to sign and content sha256 checksum are also available. These values are useful for debugging signature errors returned by AWS.
signature.canonical_request #=> "..." signature.string_to_sign #=> "..." signature.content_sha256 #=> "..."
@param [Hash] request
@option request [required, String] :http_method One of
'GET', 'HEAD', 'PUT', 'POST', 'PATCH', or 'DELETE'
@option request [required, String, URI::HTTPS, URI::HTTP] :url
The request URI. Must be a valid HTTP or HTTPS URI.
@option request [optional, Hash] :headers ({}) A hash of headers
to sign. If the 'X-Amz-Content-Sha256' header is set, the `:body` is optional and will not be read.
@option request [otpional, String, IO] :body (”) The HTTP request body.
A sha256 checksum is computed of the body unless the 'X-Amz-Content-Sha256' header is set.
@return [Signature] Return an instance of {Signature} that has
a `#headers` method. The headers must be applied to your request.
# File lib/aws-sigv4/signer.rb, line 202 def sign_request(request) creds = get_credentials http_method = extract_http_method(request) url = extract_url(request) headers = downcase_headers(request[:headers]) datetime = headers['x-amz-date'] datetime ||= Time.now.utc.strftime("%Y%m%dT%H%M%SZ") date = datetime[0,8] content_sha256 = headers['x-amz-content-sha256'] content_sha256 ||= sha256_hexdigest(request[:body] || '') sigv4_headers = {} sigv4_headers['host'] = host(url) sigv4_headers['x-amz-date'] = datetime sigv4_headers['x-amz-security-token'] = creds.session_token if creds.session_token sigv4_headers['x-amz-content-sha256'] ||= content_sha256 if @apply_checksum_header headers = headers.merge(sigv4_headers) # merge so we do not modify given headers hash # compute signature parts creq = canonical_request(http_method, url, headers, content_sha256) sts = string_to_sign(datetime, creq) sig = signature(creds.secret_access_key, date, sts) # apply signature sigv4_headers['authorization'] = [ "AWS4-HMAC-SHA256 Credential=#{credential(creds, date)}", "SignedHeaders=#{signed_headers(headers)}", "Signature=#{sig}", ].join(', ') # Returning the signature components. Signature.new( headers: sigv4_headers, string_to_sign: sts, canonical_request: creq, content_sha256: content_sha256 ) end
Private Instance Methods
# File lib/aws-sigv4/signer.rb, line 452 def canonical_header_value(value) value.match(/^".*"$/) ? value : value.gsub(/\s+/, ' ').strip end
# File lib/aws-sigv4/signer.rb, line 440 def canonical_headers(headers) headers = headers.inject([]) do |headers, (k,v)| if @unsigned_headers.include?(k) headers else headers << [k,v] end end headers = headers.sort_by(&:first) headers.map{|k,v| "#{k}:#{canonical_header_value(v.to_s)}" }.join("\n") end
# File lib/aws-sigv4/signer.rb, line 358 def canonical_request(http_method, url, headers, content_sha256) [ http_method, path(url), normalized_querystring(url.query || ''), canonical_headers(headers) + "\n", signed_headers(headers), content_sha256, ].join("\n") end
# File lib/aws-sigv4/signer.rb, line 387 def credential(credentials, date) "#{credentials.access_key_id}/#{credential_scope(date)}" end
# File lib/aws-sigv4/signer.rb, line 378 def credential_scope(date) [ date, @region, @service, 'aws4_request', ].join('/') end
# File lib/aws-sigv4/signer.rb, line 574 def credentials_set?(credentials) credentials.access_key_id && credentials.secret_access_key end
# File lib/aws-sigv4/signer.rb, line 539 def downcase_headers(headers) (headers || {}).to_hash.inject({}) do |hash, (key, value)| hash[key.downcase] = value hash end end
# File lib/aws-sigv4/signer.rb, line 511 def extract_credentials_provider(options) if options[:credentials_provider] options[:credentials_provider] elsif options.key?(:credentials) || options.key?(:access_key_id) StaticCredentialsProvider.new(options) else raise Errors::MissingCredentialsError end end
# File lib/aws-sigv4/signer.rb, line 546 def extract_expires_in(options) case options[:expires_in] when nil then 900.to_s when Integer then options[:expires_in].to_s else msg = "expected :expires_in to be a number of seconds" raise ArgumentError, msg end end
# File lib/aws-sigv4/signer.rb, line 521 def extract_http_method(request) if request[:http_method] request[:http_method].upcase else msg = "missing required option :http_method" raise ArgumentError, msg end end
# File lib/aws-sigv4/signer.rb, line 503 def extract_region(options) if options[:region] options[:region] else raise Errors::MissingRegionError end end
# File lib/aws-sigv4/signer.rb, line 494 def extract_service(options) if options[:service] options[:service] else msg = "missing required option :service" raise ArgumentError, msg end end
# File lib/aws-sigv4/signer.rb, line 530 def extract_url(request) if request[:url] URI.parse(request[:url].to_s) else msg = "missing required option :url" raise ArgumentError, msg end end
# File lib/aws-sigv4/signer.rb, line 564 def get_credentials credentials = @credentials_provider.credentials if credentials_set?(credentials) credentials else msg = 'unable to sign request without credentials set' raise Errors::MissingCredentialsError.new(msg) end end
# File lib/aws-sigv4/signer.rb, line 490 def hexhmac(key, value) OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha256'), key, value) end
# File lib/aws-sigv4/signer.rb, line 486 def hmac(key, value) OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha256'), key, value) end
# File lib/aws-sigv4/signer.rb, line 456 def host(uri) if standard_port?(uri) uri.host else "#{uri.host}:#{uri.port}" end end
# File lib/aws-sigv4/signer.rb, line 409 def normalized_querystring(querystring) params = querystring.split('&') params = params.map { |p| p.match(/=/) ? p : p + '=' } # We have to sort by param name and preserve order of params that # have the same name. Default sort <=> in JRuby will swap members # occasionally when <=> is 0 (considered still sorted), but this # causes our normalized query string to not match the sent querystring. # When names match, we then sort by their original order params = params.each.with_index.sort do |a, b| a, a_offset = a a_name = a.split('=')[0] b, b_offset = b b_name = b.split('=')[0] if a_name == b_name a_offset <=> b_offset else a_name <=> b_name end end.map(&:first).join('&') end
# File lib/aws-sigv4/signer.rb, line 399 def path(url) path = url.path path = '/' if path == '' if @uri_escape_path uri_escape_path(path) else path end end
@param [File, Tempfile, IO#read, String] value @return [String<SHA256 Hexdigest>]
# File lib/aws-sigv4/signer.rb, line 471 def sha256_hexdigest(value) if (File === value || Tempfile === value) && !value.path.nil? && File.exist?(value.path) OpenSSL::Digest::SHA256.file(value).hexdigest elsif value.respond_to?(:read) sha256 = OpenSSL::Digest::SHA256.new while chunk = value.read(1024 * 1024) # 1MB sha256.update(chunk) end value.rewind sha256.hexdigest else OpenSSL::Digest::SHA256.hexdigest(value) end end
# File lib/aws-sigv4/signer.rb, line 391 def signature(secret_access_key, date, string_to_sign) k_date = hmac("AWS4" + secret_access_key, date) k_region = hmac(k_date, @region) k_service = hmac(k_region, @service) k_credentials = hmac(k_service, 'aws4_request') hexhmac(k_credentials, string_to_sign) end
# File lib/aws-sigv4/signer.rb, line 430 def signed_headers(headers) headers.inject([]) do |signed_headers, (header, _)| if @unsigned_headers.include?(header) signed_headers else signed_headers << header end end.sort.join(';') end
# File lib/aws-sigv4/signer.rb, line 464 def standard_port?(uri) (uri.scheme == 'http' && uri.port == 80) || (uri.scheme == 'https' && uri.port == 443) end
# File lib/aws-sigv4/signer.rb, line 369 def string_to_sign(datetime, canonical_request) [ 'AWS4-HMAC-SHA256', datetime, credential_scope(datetime[0,8]), sha256_hexdigest(canonical_request), ].join("\n") end
# File lib/aws-sigv4/signer.rb, line 556 def uri_escape(string) self.class.uri_escape(string) end
# File lib/aws-sigv4/signer.rb, line 560 def uri_escape_path(string) self.class.uri_escape_path(string) end