ActiveSupport::MessageVerifier
class ActiveSupport::MessageVerifier
MessageVerifier
makes it easy to generate and verify messages which are signed to prevent tampering.
This is useful for cases like remember-me tokens and auto-unsubscribe links where the session store isn't suitable or available.
Remember Me:
cookies[:remember_me] = @verifier.generate([@user.id, 2.weeks.from_now])
In the authentication filter:
id, time = @verifier.verify(cookies[:remember_me]) if Time.now < time self.current_user = User.find(id) end
By default it uses Marshal to serialize the message. If you want to use another serialization method, you can set the serializer in the options hash upon initialization:
@verifier = ActiveSupport::MessageVerifier.new('s3Krit', serializer: YAML)
MessageVerifier
creates HMAC signatures using SHA1 hash algorithm by default. If you want to use a different hash algorithm, you can change it by providing `:digest` key as an option while initializing the verifier:
@verifier = ActiveSupport::MessageVerifier.new('s3Krit', digest: 'SHA256')
Public Class Methods
# File activesupport/lib/active_support/message_verifier.rb, line 36 def initialize(secret, options = {}) raise ArgumentError, 'Secret should not be nil.' unless secret @secret = secret @digest = options[:digest] || 'SHA1' @serializer = options[:serializer] || Marshal end
Public Instance Methods
Generates a signed message for the provided value.
The message is signed with the MessageVerifier
's secret. Without knowing the secret, the original value cannot be extracted from the message.
verifier = ActiveSupport::MessageVerifier.new 's3Krit' verifier.generate 'a private message' # => "BAhJIhRwcml2YXRlLW1lc3NhZ2UGOgZFVA==--e2d724331ebdee96a10fb99b089508d1c72bd772"
# File activesupport/lib/active_support/message_verifier.rb, line 115 def generate(value) data = encode(@serializer.dump(value)) "#{data}--#{generate_digest(data)}" end
Checks if a signed message could have been generated by signing an object with the MessageVerifier
's secret.
verifier = ActiveSupport::MessageVerifier.new 's3Krit' signed_message = verifier.generate 'a private message' verifier.valid_message?(signed_message) # => true tampered_message = signed_message.chop # editing the message invalidates the signature verifier.valid_message?(tampered_message) # => false
# File activesupport/lib/active_support/message_verifier.rb, line 52 def valid_message?(signed_message) return if signed_message.nil? || !signed_message.valid_encoding? || signed_message.blank? data, digest = signed_message.split("--".freeze) data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data)) end
Decodes the signed message using the MessageVerifier
's secret.
verifier = ActiveSupport::MessageVerifier.new 's3Krit' signed_message = verifier.generate 'a private message' verifier.verified(signed_message) # => 'a private message'
Returns nil
if the message was not signed with the same secret.
other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit' other_verifier.verified(signed_message) # => nil
Returns nil
if the message is not Base64-encoded.
invalid_message = "f--46a0120593880c733a53b6dad75b42ddc1c8996d" verifier.verified(invalid_message) # => nil
Raises any error raised while decoding the signed message.
incompatible_message = "test--dad7b06c94abba8d46a15fafaef56c327665d5ff" verifier.verified(incompatible_message) # => TypeError: incompatible marshal file format
# File activesupport/lib/active_support/message_verifier.rb, line 80 def verified(signed_message) if valid_message?(signed_message) begin data = signed_message.split("--".freeze)[0] @serializer.load(decode(data)) rescue ArgumentError => argument_error return if argument_error.message =~ %r{invalid base64} raise end end end
Decodes the signed message using the MessageVerifier
's secret.
verifier = ActiveSupport::MessageVerifier.new 's3Krit' signed_message = verifier.generate 'a private message' verifier.verify(signed_message) # => 'a private message'
Raises InvalidSignature
if the message was not signed with the same secret or was not Base64-encoded.
other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit' other_verifier.verify(signed_message) # => ActiveSupport::MessageVerifier::InvalidSignature
# File activesupport/lib/active_support/message_verifier.rb, line 104 def verify(signed_message) verified(signed_message) || raise(InvalidSignature) end
© 2004–2017 David Heinemeier Hansson
Licensed under the MIT License.