Add option to verify Origin header in CSRF checks

actionpack/lib/action_controller/metal/request_forgery_protection.rb

@@ -77,6 +77,10 @@ module RequestForgeryProtection
       config_accessor :log_warning_on_csrf_failure
       self.log_warning_on_csrf_failure = true
 
+      # Controls whether the Origin header is checked in addition to the CSRF token.
+      config_accessor :forgery_protection_origin_check
+      self.forgery_protection_origin_check = false
+
       helper_method :form_authenticity_token
       helper_method :protect_against_forgery?
     end
@@ -257,8 +261,19 @@ def non_xhr_javascript_response?
       # * Does the X-CSRF-Token header match the form_authenticity_token
       def verified_request?
         !protect_against_forgery? || request.get? || request.head? ||
-          valid_authenticity_token?(session, form_authenticity_param) ||
-          valid_authenticity_token?(session, request.headers['X-CSRF-Token'])
+          (valid_request_origin? && any_authenticity_token_valid?)
+      end
+
+      # Checks if any of the authenticity tokens from the request are valid.
+      def any_authenticity_token_valid?
+        request_authenticity_tokens.any? do |token|
+          valid_authenticity_token?(session, token)
+        end
+      end
+
+      # Possible authenticity tokens sent in the request.
+      def request_authenticity_tokens
+        [form_authenticity_param, request.x_csrf_token]
       end
 
       # Sets the token value for the current session.
@@ -336,5 +351,16 @@ def form_authenticity_param
       def protect_against_forgery?
         allow_forgery_protection
       end
+
+      # Checks if the request originated from the same origin by looking at the
+      # Origin header.
+      def valid_request_origin?
+        if forgery_protection_origin_check
+          # We accept blank origin headers because some user agents don't send it.
+          request.origin.nil? || request.origin == request.base_url
+        else
+          true
+        end
+      end
   end
 end

actionpack/lib/action_dispatch/http/request.rb

@@ -36,8 +36,8 @@ class Request
         HTTP_ACCEPT HTTP_ACCEPT_CHARSET HTTP_ACCEPT_ENCODING
         HTTP_ACCEPT_LANGUAGE HTTP_CACHE_CONTROL HTTP_FROM
         HTTP_NEGOTIATE HTTP_PRAGMA HTTP_CLIENT_IP
-        HTTP_X_FORWARDED_FOR HTTP_VERSION
-        HTTP_X_REQUEST_ID HTTP_X_FORWARDED_HOST
+        HTTP_X_FORWARDED_FOR HTTP_ORIGIN HTTP_VERSION
+        HTTP_X_CSRF_TOKEN HTTP_X_REQUEST_ID HTTP_X_FORWARDED_HOST
         SERVER_ADDR
         ].freeze
 

actionpack/test/controller/request_forgery_protection_test.rb

@@ -304,6 +304,41 @@ def test_should_allow_put_with_token_in_header
     assert_not_blocked { put :index }
   end
 
+  def test_should_allow_post_with_origin_checking_and_correct_origin
+    forgery_protection_origin_check do
+      session[:_csrf_token] = @token
+      @controller.stub :form_authenticity_token, @token do
+        assert_not_blocked do
+          @request.set_header 'HTTP_ORIGIN', 'http://test.host'
+          post :index, params: { custom_authenticity_token: @token }
+        end
+      end
+    end
+  end
+
+  def test_should_allow_post_with_origin_checking_and_no_origin
+    forgery_protection_origin_check do
+      session[:_csrf_token] = @token
+      @controller.stub :form_authenticity_token, @token do
+        assert_not_blocked do
+          post :index, params: { custom_authenticity_token: @token }
+        end
+      end
+    end
+  end
+
+  def test_should_block_post_with_origin_checking_and_wrong_origin
+    forgery_protection_origin_check do
+      session[:_csrf_token] = @token
+      @controller.stub :form_authenticity_token, @token do
+        assert_blocked do
+          @request.set_header 'HTTP_ORIGIN', 'http://bad.host'
+          post :index, params: { custom_authenticity_token: @token }
+        end
+      end
+    end
+  end
+
   def test_should_warn_on_missing_csrf_token
     old_logger = ActionController::Base.logger
     logger = ActiveSupport::LogSubscriber::TestHelper::MockLogger.new
@@ -405,6 +440,16 @@ def assert_cross_origin_blocked
   def assert_cross_origin_not_blocked
     assert_not_blocked { yield }
   end
+
+  def forgery_protection_origin_check
+    old_setting = ActionController::Base.forgery_protection_origin_check
+    ActionController::Base.forgery_protection_origin_check = true
+    begin
+      yield
+    ensure
+      ActionController::Base.forgery_protection_origin_check = old_setting
+    end
+  end
 end
 
 # OK let's get our test on

guides/source/configuring.md

@@ -345,6 +345,8 @@ The schema dumper adds one additional configuration option:
 
 * `config.action_controller.allow_forgery_protection` enables or disables CSRF protection. By default this is `false` in test mode and `true` in all other modes.
 
+* `config.action_controller.forgery_protection_origin_check` configures whether the HTTP `Origin` header should be checked against the site's origin as an additional CSRF defense.
+
 * `config.action_controller.relative_url_root` can be used to tell Rails that you are [deploying to a subdirectory](configuring.html#deploy-to-a-subdirectory-relative-url-root). The default is `ENV['RAILS_RELATIVE_URL_ROOT']`.
 
 * `config.action_controller.permit_all_parameters` sets all the parameters for mass assignment to be permitted by default. The default value is `false`.

railties/lib/rails/generators/rails/app/templates/config/initializers/request_forgery_protection.rb

@@ -0,0 +1,4 @@
+# Be sure to restart your server when you modify this file.
+
+# Enable origin-checking CSRF mitigation.
+Rails.application.config.action_controller.forgery_protection_origin_check = true