strategy.rb

require 'omniauth/key_store'

module OmniAuth
  class NoSessionError < StandardError; end
  # The Strategy is the base unit of OmniAuth's ability to
  # wrangle multiple providers. Each strategy provided by
  # OmniAuth includes this mixin to gain the default functionality
  # necessary to be compatible with the OmniAuth library.
  module Strategy # rubocop:disable ModuleLength
    def self.included(base)
      OmniAuth.strategies << base

      base.extend ClassMethods
      base.class_eval do
        option :setup, false
        option :skip_info, false
        option :origin_param, 'origin'
      end
    end

    module ClassMethods
      # Returns an inherited set of default options set at the class-level
      # for each strategy.
      def default_options
        # existing = superclass.default_options if superclass.respond_to?(:default_options)
        existing = superclass.respond_to?(:default_options) ? superclass.default_options : {}
        @default_options ||= OmniAuth::Strategy::Options.new(existing)
      end

      # This allows for more declarative subclassing of strategies by allowing
      # default options to be set using a simple configure call.
      #
      # @param options [Hash] If supplied, these will be the default options (deep-merged into the superclass's default options).
      # @yield [Options] The options Mash that allows you to set your defaults as you'd like.
      #
      # @example Using a yield to configure the default options.
      #
      #   class MyStrategy
      #     include OmniAuth::Strategy
      #
      #     configure do |c|
      #       c.foo = 'bar'
      #     end
      #   end
      #
      # @example Using a hash to configure the default options.
      #
      #   class MyStrategy
      #     include OmniAuth::Strategy
      #     configure foo: 'bar'
      #   end
      def configure(options = nil)
        if block_given?
          yield default_options
        else
          default_options.deep_merge!(options)
        end
      end

      # Directly declare a default option for your class. This is a useful from
      # a documentation perspective as it provides a simple line-by-line analysis
      # of the kinds of options your strategy provides by default.
      #
      # @param name [Symbol] The key of the default option in your configuration hash.
      # @param value [Object] The value your object defaults to. Nil if not provided.
      #
      # @example
      #
      #   class MyStrategy
      #     include OmniAuth::Strategy
      #
      #     option :foo, 'bar'
      #     option
      #   end
      def option(name, value = nil)
        default_options[name] = value
      end

      # Sets (and retrieves) option key names for initializer arguments to be
      # recorded as. This takes care of 90% of the use cases for overriding
      # the initializer in OmniAuth Strategies.
      def args(args = nil)
        if args
          @args = Array(args)
          return
        end
        existing = superclass.respond_to?(:args) ? superclass.args : []
        (instance_variable_defined?(:@args) && @args) || existing
      end

      %w[uid info extra credentials].each do |fetcher|
        class_eval <<-RUBY, __FILE__, __LINE__ + 1
          attr_reader :#{fetcher}_proc
          private :#{fetcher}_proc

          def #{fetcher}(&block)
            return #{fetcher}_proc unless block_given?
            @#{fetcher}_proc = block
          end

          def #{fetcher}_stack(context)
            compile_stack(self.ancestors, :#{fetcher}, context)
          end
        RUBY
      end

      def compile_stack(ancestors, method, context)
        stack = ancestors.inject([]) do |a, ancestor|
          a << context.instance_eval(&ancestor.send(method)) if ancestor.respond_to?(method) && ancestor.send(method)
          a
        end
        stack.reverse!
      end
    end

    attr_reader :app, :env, :options, :response

    # Initializes the strategy by passing in the Rack endpoint,
    # the unique URL segment name for this strategy, and any
    # additional arguments. An `options` hash is automatically
    # created from the last argument if it is a hash.
    #
    # @param app [Rack application] The application on which this middleware is applied.
    #
    # @overload new(app, options = {})
    #   If nothing but a hash is supplied, initialized with the supplied options
    #   overriding the strategy's default options via a deep merge.
    # @overload new(app, *args, options = {})
    #   If the strategy has supplied custom arguments that it accepts, they may
    #   will be passed through and set to the appropriate values.
    #
    # @yield [Options] Yields options to block for further configuration.
    def initialize(app, *args, &block) # rubocop:disable UnusedMethodArgument
      @app = app
      @env = nil
      @options = self.class.default_options.dup

      options.deep_merge!(args.pop) if args.last.is_a?(Hash)
      options[:name] ||= self.class.to_s.split('::').last.downcase

      self.class.args.each do |arg|
        break if args.empty?

        options[arg] = args.shift
      end

      # Make sure that all of the args have been dealt with, otherwise error out.
      raise(ArgumentError.new("Received wrong number of arguments. #{args.inspect}")) unless args.empty?

      yield options if block_given?
    end

    def inspect
      "#<#{self.class}>"
    end

    # Direct access to the OmniAuth logger, automatically prefixed
    # with this strategy's name.
    #
    # @example
    #   log :warn, "This is a warning."
    def log(level, message)
      OmniAuth.logger.send(level, "(#{name}) #{message}")
    end

    # Duplicates this instance and runs #call! on it.
    # @param [Hash] The Rack environment.
    def call(env)
      dup.call!(env)
    end

    # The logic for dispatching any additional actions that need
    # to be taken. For instance, calling the request phase if
    # the request path is recognized.
    #
    # @param env [Hash] The Rack environment.
    def call!(env) # rubocop:disable CyclomaticComplexity, PerceivedComplexity
      unless env['rack.session']
        error = OmniAuth::NoSessionError.new('You must provide a session to use OmniAuth.')
        raise(error)
      end

      warn_if_using_get

      @env = env
      @env['omniauth.strategy'] = self if on_auth_path?

      return mock_call!(env) if OmniAuth.config.test_mode

      begin
        return options_call if on_auth_path? && options_request?
        return request_call if on_request_path? && OmniAuth.config.allowed_request_methods.include?(request.request_method.downcase.to_sym)
        return callback_call if on_callback_path?
        return other_phase if respond_to?(:other_phase)
      rescue => ex
        return fail!(ex.message, ex)
      end

      @app.call(env)
    end

    def warn_if_using_get
      return unless OmniAuth.config.allowed_request_methods.include?(:get)
      return if OmniAuth.config.silence_get_warning

      log :warn, <<-WARN
  You are using GET as an allowed request method for OmniAuth. This may leave
  you open to CSRF attacks. As of v2.0.0, OmniAuth by default allows only POST
  to its own routes. You should review the following resources to guide your
  mitigation:
  https://github.com/omniauth/omniauth/wiki/Resolving-CVE-2015-9284
  https://github.com/omniauth/omniauth/issues/960
  https://nvd.nist.gov/vuln/detail/CVE-2015-9284
  https://github.com/omniauth/omniauth/pull/809

  You can ignore this warning by setting:
  OmniAuth.config.silence_get_warning = true
      WARN
    end

    # Responds to an OPTIONS request.
    def options_call
      OmniAuth.config.before_options_phase.call(env) if OmniAuth.config.before_options_phase
      verbs = OmniAuth.config.allowed_request_methods.collect(&:to_s).collect(&:upcase).join(', ')
      [200, {'Allow' => verbs}, []]
    end

    # Performs the steps necessary to run the request phase of a strategy.
    def request_call # rubocop:disable CyclomaticComplexity, MethodLength, PerceivedComplexity
      setup_phase
      log :info, 'Request phase initiated.'

      # store query params from the request url, extracted in the callback_phase
      session['omniauth.params'] = request.GET

      OmniAuth.config.request_validation_phase.call(env) if OmniAuth.config.request_validation_phase
      OmniAuth.config.before_request_phase.call(env) if OmniAuth.config.before_request_phase

      if options.form.respond_to?(:call)
        log :info, 'Rendering form from supplied Rack endpoint.'
        options.form.call(env)
      elsif options.form
        log :info, 'Rendering form from underlying application.'
        call_app!
      elsif !options.origin_param
        request_phase
      else
        if request.params[options.origin_param]
          env['rack.session']['omniauth.origin'] = request.params[options.origin_param]
        elsif env['HTTP_REFERER'] && !env['HTTP_REFERER'].match(/#{request_path}$/)
          env['rack.session']['omniauth.origin'] = env['HTTP_REFERER']
        end

        request_phase
      end
    rescue OmniAuth::AuthenticityError => e
      fail!(:authenticity_error, e)
    end

    # Performs the steps necessary to run the callback phase of a strategy.
    def callback_call
      setup_phase
      log :info, 'Callback phase initiated.'
      @env['omniauth.origin'] = session.delete('omniauth.origin')
      @env['omniauth.origin'] = nil if env['omniauth.origin'] == ''
      @env['omniauth.params'] = session.delete('omniauth.params') || {}
      OmniAuth.config.before_callback_phase.call(@env) if OmniAuth.config.before_callback_phase
      callback_phase
    end

    # Returns true if the environment recognizes either the
    # request or callback path.
    def on_auth_path?
      on_request_path? || on_callback_path?
    end

    def on_request_path?
      if options[:request_path].respond_to?(:call)
        options[:request_path].call(env)
      else
        on_path?(request_path)
      end
    end

    def on_callback_path?
      on_path?(callback_path)
    end

    def on_path?(path)
      current_path.casecmp(path).zero?
    end

    def options_request?
      request.request_method == 'OPTIONS'
    end

    # This is called in lieu of the normal request process
    # in the event that OmniAuth has been configured to be
    # in test mode.
    def mock_call!(*)
      return mock_request_call if on_request_path? && OmniAuth.config.allowed_request_methods.include?(request.request_method.downcase.to_sym)
      return mock_callback_call if on_callback_path?

      call_app!
    end

    def mock_request_call
      setup_phase

      session['omniauth.params'] = request.GET
      OmniAuth.config.before_request_phase.call(env) if OmniAuth.config.before_request_phase
      if options.origin_param
        if request.params[options.origin_param]
          session['omniauth.origin'] = request.params[options.origin_param]
        elsif env['HTTP_REFERER'] && !env['HTTP_REFERER'].match(/#{request_path}$/)
          session['omniauth.origin'] = env['HTTP_REFERER']
        end
      end

      redirect(callback_url)
    end

    def mock_callback_call
      setup_phase
      @env['omniauth.origin'] = session.delete('omniauth.origin')
      @env['omniauth.origin'] = nil if env['omniauth.origin'] == ''
      @env['omniauth.params'] = session.delete('omniauth.params') || {}

      mocked_auth = OmniAuth.mock_auth_for(name.to_s)
      if mocked_auth.is_a?(Symbol)
        fail!(mocked_auth)
      else
        @env['omniauth.auth'] = mocked_auth
        OmniAuth.config.before_callback_phase.call(@env) if OmniAuth.config.before_callback_phase
        call_app!
      end
    end

    # The setup phase looks for the `:setup` option to exist and,
    # if it is, will call either the Rack endpoint supplied to the
    # `:setup` option or it will call out to the setup path of the
    # underlying application. This will default to `/auth/:provider/setup`.
    def setup_phase
      if options[:setup].respond_to?(:call)
        log :info, 'Setup endpoint detected, running now.'
        options[:setup].call(env)
      elsif options[:setup]
        log :info, 'Calling through to underlying application for setup.'
        setup_env = env.merge('PATH_INFO' => setup_path, 'REQUEST_METHOD' => 'GET')
        call_app!(setup_env)
      end
    end

    # @abstract This method is called when the user is on the request path. You should
    # perform any information gathering you need to be able to authenticate
    # the user in this phase.
    def request_phase
      raise(NotImplementedError)
    end

    def uid
      self.class.uid_stack(self).last
    end

    def info
      merge_stack(self.class.info_stack(self))
    end

    def credentials
      merge_stack(self.class.credentials_stack(self))
    end

    def extra
      merge_stack(self.class.extra_stack(self))
    end

    def auth_hash
      hash = AuthHash.new(:provider => name, :uid => uid)
      hash.info = info unless skip_info?
      hash.credentials = credentials if credentials
      hash.extra = extra if extra
      hash
    end

    # Determines whether or not user info should be retrieved. This
    # allows some strategies to save a call to an external API service
    # for existing users. You can use it either by setting the `:skip_info`
    # to true or by setting `:skip_info` to a Proc that takes a uid and
    # evaluates to true when you would like to skip info.
    #
    # @example
    #
    #   use MyStrategy, :skip_info => lambda{|uid| User.find_by_uid(uid)}
    def skip_info?
      return false unless options.skip_info?
      return true unless options.skip_info.respond_to?(:call)

      options.skip_info.call(uid)
    end

    def callback_phase
      env['omniauth.auth'] = auth_hash
      call_app!
    end

    def path_prefix
      options[:path_prefix] || OmniAuth.config.path_prefix
    end

    def custom_path(kind)
      if options[kind].respond_to?(:call)
        result = options[kind].call(env)
        return nil unless result.is_a?(String)

        result
      else
        options[kind]
      end
    end

    def request_path
      @request_path ||= options[:request_path].is_a?(String) ? options[:request_path] : "#{path_prefix}/#{name}"
    end

    def callback_path
      @callback_path ||= begin
        path = options[:callback_path] if options[:callback_path].is_a?(String)
        path ||= current_path if options[:callback_path].respond_to?(:call) && options[:callback_path].call(env)
        path ||= custom_path(:request_path)
        path ||= "#{path_prefix}/#{name}/callback"
        path
      end
    end

    def setup_path
      options[:setup_path] || "#{path_prefix}/#{name}/setup"
    end

    CURRENT_PATH_REGEX = %r{/$}.freeze
    EMPTY_STRING       = ''.freeze
    def current_path
      @current_path ||= request.path_info.downcase.sub(CURRENT_PATH_REGEX, EMPTY_STRING)
    end

    def query_string
      request.query_string.empty? ? '' : "?#{request.query_string}"
    end

    def call_app!(env = @env)
      @app.call(env)
    end

    def full_host
      case OmniAuth.config.full_host
      when String
        OmniAuth.config.full_host
      when Proc
        OmniAuth.config.full_host.call(env)
      else
        # in Rack 1.3.x, request.url explodes if scheme is nil
        if request.scheme && request.url.match(URI::ABS_URI)
          uri = URI.parse(request.url.gsub(/\?.*$/, ''))
          uri.path = ''
          # sometimes the url is actually showing http inside rails because the
          # other layers (like nginx) have handled the ssl termination.
          uri.scheme = 'https' if ssl? # rubocop:disable BlockNesting
          uri.to_s
        else ''
        end
      end
    end

    def callback_url
      full_host + script_name + callback_path + query_string
    end

    def script_name
      @env['SCRIPT_NAME'] || ''
    end

    def session
      @env['rack.session']
    end

    def request
      @request ||= Rack::Request.new(@env)
    end

    def name
      options[:name]
    end

    def redirect(uri)
      r = Rack::Response.new

      if options[:iframe]
        r.write("<script type='text/javascript' charset='utf-8'>top.location.href = '#{uri}';</script>")
      else
        r.write("Redirecting to #{uri}...")
        r.redirect(uri)
      end

      r.finish
    end

    def user_info
      {}
    end

    def fail!(message_key, exception = nil)
      env['omniauth.error'] = exception
      env['omniauth.error.type'] = message_key.to_sym
      env['omniauth.error.strategy'] = self

      if exception
        log :error, "Authentication failure! #{message_key}: #{exception.class}, #{exception.message}"
      else
        log :error, "Authentication failure! #{message_key} encountered."
      end

      OmniAuth.config.on_failure.call(env)
    end

    def dup
      super.tap do
        @options = @options.dup
      end
    end

    class Options < OmniAuth::KeyStore; end

  protected

    def merge_stack(stack)
      stack.inject({}) do |a, e|
        a.merge!(e)
        a
      end
    end

    def ssl?
      request.env['HTTPS'] == 'on' ||
        request.env['HTTP_X_FORWARDED_SSL'] == 'on' ||
        request.env['HTTP_X_FORWARDED_SCHEME'] == 'https' ||
        (request.env['HTTP_X_FORWARDED_PROTO'] && request.env['HTTP_X_FORWARDED_PROTO'].split(',')[0] == 'https') ||
        request.env['rack.url_scheme'] == 'https'
    end
  end
end