-module ActiveSupport
- # 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 < Time.now
- # self.current_user = User.find(id)
- # end
- #
- class MessageVerifier
- class InvalidSignature < StandardError; end
-
- def initialize(secret, digest = 'SHA1')
- @secret = secret
- @digest = digest
- end
-
- def verify(signed_message)
- data, digest = signed_message.split("--")
- if digest != generate_digest(data)
- raise InvalidSignature
- else
- Marshal.load(ActiveSupport::Base64.decode64(data))
- end
- end
-
- def generate(value)
- data = ActiveSupport::Base64.encode64s(Marshal.dump(value))
- "#{data}--#{generate_digest(data)}"
- end
-
- private
- def generate_digest(data)
- require 'openssl' unless defined?(OpenSSL)
- OpenSSL::HMAC.hexdigest(OpenSSL::Digest::Digest.new(@digest), @secret, data)
- end
- end
-end