class ActiveSupport::MessageVerifier - activesupport-4.2.3 Documentation

# 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 < Time.now
      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)

### Public Class Methods

new(secret, options = {}) click to toggle source

    # File lib/active_support/message_verifier.rb, line 30
    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

generate(value) click to toggle source

    # File lib/active_support/message_verifier.rb, line 53
    def generate(value)
      data = encode(@serializer.dump(value))
      "#{data}--#{generate_digest(data)}"
    end

verify(signed_message) click to toggle source

    # File lib/active_support/message_verifier.rb, line 37
    def verify(signed_message)
      raise InvalidSignature if signed_message.blank?

      data, digest = signed_message.split("--")
      if data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data))
        begin
          @serializer.load(decode(data))
        rescue ArgumentError => argument_error
          raise InvalidSignature if argument_error.message =~ %r{invalid base64}
          raise
        end
      else
        raise InvalidSignature
      end
    end

### Private Instance Methods

decode(data) click to toggle source

    # File lib/active_support/message_verifier.rb, line 63
    def decode(data)
      ::Base64.strict_decode64(data)
    end

encode(data) click to toggle source

    # File lib/active_support/message_verifier.rb, line 59
    def encode(data)
      ::Base64.strict_encode64(data)
    end

generate_digest(data) click to toggle source

    # File lib/active_support/message_verifier.rb, line 67
    def generate_digest(data)
      require 'openssl' unless defined?(OpenSSL)
      OpenSSL::HMAC.hexdigest(OpenSSL::Digest.const_get(@digest).new, @secret, data)
    end