Change the CSRF whitelisting to only apply to get requests

Unfortunately the previous method of browser detection and XHR whitelisting is unable to prevent requests issued from some Flash animations and Java applets.  To ease the work required to include the CSRF token in ajax requests rails now supports providing the token in a custom http header:

 X-CSRF-Token: ...

This fixes CVE-2011-0447

Author: NZKoz

actionpack/lib/action_controller/request_forgery_protection.rb

@@ -76,7 +76,11 @@ def protect_from_forgery(options = {})
     protected
       # The actual before_filter that is used.  Modify this to change how you handle unverified requests.
       def verify_authenticity_token
-        verified_request? || raise(ActionController::InvalidAuthenticityToken)
+        verified_request? || handle_unverified_request
+      end
+
+      def handle_unverified_request
+        reset_session
       end
 
       # Returns true or false if a request is verified.  Checks:
@@ -85,11 +89,10 @@ def verify_authenticity_token
       # * is it a GET request?  Gets should be safe and idempotent
       # * Does the form_authenticity_token match the given token value from the params?
       def verified_request?
-        !protect_against_forgery?     ||
-          request.method == :get      ||
-          request.xhr?                ||
-          !verifiable_request_format? ||
-          form_authenticity_token == form_authenticity_param
+        !protect_against_forgery?                            ||
+          request.get?                                       ||
+          form_authenticity_token == form_authenticity_param ||
+          form_authenticity_token == request.headers['X-CSRF-Token']
       end
 
       def form_authenticity_param

actionpack/lib/action_view/helpers.rb

@@ -6,6 +6,7 @@ module Helpers #:nodoc:
     autoload :BenchmarkHelper, 'action_view/helpers/benchmark_helper'
     autoload :CacheHelper, 'action_view/helpers/cache_helper'
     autoload :CaptureHelper, 'action_view/helpers/capture_helper'
+    autoload :CsrfHelper, 'action_view/helpers/csrf_helper'
     autoload :DateHelper, 'action_view/helpers/date_helper'
     autoload :DebugHelper, 'action_view/helpers/debug_helper'
     autoload :FormHelper, 'action_view/helpers/form_helper'
@@ -38,6 +39,7 @@ module ClassMethods
     include BenchmarkHelper
     include CacheHelper
     include CaptureHelper
+    include CsrfHelper
     include DateHelper
     include DebugHelper
     include FormHelper

actionpack/lib/action_view/helpers/csrf_helper.rb

@@ -0,0 +1,14 @@
+module ActionView
+  # = Action View CSRF Helper
+  module Helpers
+    module CsrfHelper
+      # Returns a meta tag with the cross-site request forgery protection token
+      # for forms to use. Place this in your head.
+      def csrf_meta_tag
+        if protect_against_forgery?
+          %(<meta name="csrf-param" content="#{h(request_forgery_protection_token)}"/>\n<meta name="csrf-token" content="#{h(form_authenticity_token)}"/>).html_safe
+        end
+      end
+    end
+  end
+end

actionpack/test/controller/request_forgery_protection_test.rb

@@ -23,6 +23,10 @@ def unsafe
     render :text => 'pwn'
   end
 
+  def meta
+    render :inline => "<%= csrf_meta_tag %>"
+  end
+
   def rescue_action(e) raise e end
 end
 
@@ -32,6 +36,16 @@ class RequestForgeryProtectionController < ActionController::Base
   protect_from_forgery :only => :index
 end
 
+class RequestForgeryProtectionControllerUsingOldBehaviour < ActionController::Base
+  include RequestForgeryProtectionActions
+  protect_from_forgery :only => %w(index meta)
+
+  def handle_unverified_request
+    raise(ActionController::InvalidAuthenticityToken)
+  end
+end
+
+
 class FreeCookieController < RequestForgeryProtectionController
   self.allow_forgery_protection = false
 
@@ -54,158 +68,92 @@ def form_authenticity_param
 # common test methods
 
 module RequestForgeryProtectionTests
-  def teardown
-    ActionController::Base.request_forgery_protection_token = nil
-  end
-  
+  def setup
+    @token      = "cf50faa3fe97702ca1ae"
 
-  def test_should_render_form_with_token_tag
-     get :index
-     assert_select 'form>div>input[name=?][value=?]', 'authenticity_token', @token
-   end
-
-   def test_should_render_button_to_with_token_tag
-     get :show_button
-     assert_select 'form>div>input[name=?][value=?]', 'authenticity_token', @token
-   end
-
-   def test_should_render_remote_form_with_only_one_token_parameter
-     get :remote_form
-     assert_equal 1, @response.body.scan(@token).size
-   end
-
-   def test_should_allow_get
-     get :index
-     assert_response :success
-   end
-
-   def test_should_allow_post_without_token_on_unsafe_action
-     post :unsafe
-     assert_response :success
-   end
-
-  def test_should_not_allow_html_post_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_raise(ActionController::InvalidAuthenticityToken) { post :index, :format => :html }
+    ActiveSupport::SecureRandom.stubs(:base64).returns(@token)
+    ActionController::Base.request_forgery_protection_token = :authenticity_token
   end
 
-  def test_should_not_allow_html_put_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_raise(ActionController::InvalidAuthenticityToken) { put :index, :format => :html }
-  end
 
-  def test_should_not_allow_html_delete_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_raise(ActionController::InvalidAuthenticityToken) { delete :index, :format => :html }
-  end
-
-  def test_should_allow_api_formatted_post_without_token
-    assert_nothing_raised do
-      post :index, :format => 'xml'
+  def test_should_render_form_with_token_tag
+    assert_not_blocked do
+      get :index
     end
+    assert_select 'form>div>input[name=?][value=?]', 'authenticity_token', @token
   end
 
-  def test_should_not_allow_api_formatted_put_without_token
-    assert_nothing_raised do
-      put :index, :format => 'xml'
+  def test_should_render_button_to_with_token_tag
+    assert_not_blocked do
+      get :show_button
     end
+    assert_select 'form>div>input[name=?][value=?]', 'authenticity_token', @token
   end
 
-  def test_should_allow_api_formatted_delete_without_token
-    assert_nothing_raised do
-      delete :index, :format => 'xml'
-    end
+  def test_should_allow_get
+    assert_not_blocked { get :index }
   end
 
-  def test_should_not_allow_api_formatted_post_sent_as_url_encoded_form_without_token
-    assert_raise(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-      post :index, :format => 'xml'
-    end
+  def test_should_allow_post_without_token_on_unsafe_action
+    assert_not_blocked { post :unsafe }
   end
 
-  def test_should_not_allow_api_formatted_put_sent_as_url_encoded_form_without_token
-    assert_raise(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-      put :index, :format => 'xml'
-    end
+  def test_should_not_allow_post_without_token
+    assert_blocked { post :index }
   end
 
-  def test_should_not_allow_api_formatted_delete_sent_as_url_encoded_form_without_token
-    assert_raise(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-      delete :index, :format => 'xml'
-    end
+  def test_should_not_allow_post_without_token_irrespective_of_format
+    assert_blocked { post :index, :format=>'xml' }
   end
 
-  def test_should_not_allow_api_formatted_post_sent_as_multipart_form_without_token
-    assert_raise(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::MULTIPART_FORM.to_s
-      post :index, :format => 'xml'
-    end
+  def test_should_not_allow_put_without_token
+    assert_blocked { put :index }
   end
 
-  def test_should_not_allow_api_formatted_put_sent_as_multipart_form_without_token
-    assert_raise(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::MULTIPART_FORM.to_s
-      put :index, :format => 'xml'
-    end
+  def test_should_not_allow_delete_without_token
+    assert_blocked { delete :index }
   end
 
-  def test_should_not_allow_api_formatted_delete_sent_as_multipart_form_without_token
-    assert_raise(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::MULTIPART_FORM.to_s
-      delete :index, :format => 'xml'
-    end
-  end
-  
-  def test_should_allow_xhr_post_without_token
-    assert_nothing_raised { xhr :post, :index }
-  end
-  
-  def test_should_allow_xhr_put_without_token
-    assert_nothing_raised { xhr :put, :index }
-  end
-  
-  def test_should_allow_xhr_delete_without_token
-    assert_nothing_raised { xhr :delete, :index }
+  def test_should_not_allow_xhr_post_without_token
+    assert_blocked { xhr :post, :index }
   end
-  
-  def test_should_allow_xhr_post_with_encoded_form_content_type_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_nothing_raised { xhr :post, :index }
-  end
-  
+
   def test_should_allow_post_with_token
-    post :index, :authenticity_token => @token
-    assert_response :success
+    assert_not_blocked { post :index, :authenticity_token => @token }
   end
 
   def test_should_allow_put_with_token
-    put :index, :authenticity_token => @token
-    assert_response :success
+    assert_not_blocked { put :index, :authenticity_token => @token }
   end
 
   def test_should_allow_delete_with_token
-    delete :index, :authenticity_token => @token
-    assert_response :success
+    assert_not_blocked { delete :index, :authenticity_token => @token }
   end
 
-  def test_should_allow_post_with_xml
-    @request.env['CONTENT_TYPE'] = Mime::XML.to_s
-    post :index, :format => 'xml'
-    assert_response :success
+  def test_should_allow_post_with_token_in_header
+    @request.env['HTTP_X_CSRF_TOKEN'] = @token
+    assert_not_blocked { post :index }
+  end
+
+  def test_should_allow_delete_with_token_in_header
+    @request.env['HTTP_X_CSRF_TOKEN'] = @token
+    assert_not_blocked { delete :index }
   end
 
-  def test_should_allow_put_with_xml
-    @request.env['CONTENT_TYPE'] = Mime::XML.to_s
-    put :index, :format => 'xml'
+  def test_should_allow_put_with_token_in_header
+    @request.env['HTTP_X_CSRF_TOKEN'] = @token
+    assert_not_blocked { put :index }
+  end
+
+  def assert_blocked
+    session[:something_like_user_id] = 1
+    yield
+    assert_nil session[:something_like_user_id], "session values are still present"
     assert_response :success
   end
 
-  def test_should_allow_delete_with_xml
-    @request.env['CONTENT_TYPE'] = Mime::XML.to_s
-    delete :index, :format => 'xml'
+  def assert_not_blocked
+    assert_nothing_raised { yield }
     assert_response :success
   end
 end
@@ -214,15 +162,20 @@ def test_should_allow_delete_with_xml
 
 class RequestForgeryProtectionControllerTest < ActionController::TestCase
   include RequestForgeryProtectionTests
-  def setup
-    @controller = RequestForgeryProtectionController.new
-    @request    = ActionController::TestRequest.new
-    @request.format = :html
-    @response   = ActionController::TestResponse.new
-    @token      = "cf50faa3fe97702ca1ae"
 
-    ActiveSupport::SecureRandom.stubs(:base64).returns(@token)
-    ActionController::Base.request_forgery_protection_token = :authenticity_token
+  test 'should emit a csrf-token meta tag' do
+    ActiveSupport::SecureRandom.stubs(:base64).returns(@token + '<=?')
+    get :meta
+    assert_equal %(<meta name="csrf-param" content="authenticity_token"/>\n<meta name="csrf-token" content="cf50faa3fe97702ca1ae&lt;=?"/>), @response.body
+  end
+end
+
+class RequestForgeryProtectionControllerUsingOldBehaviourTest < ActionController::TestCase
+  include RequestForgeryProtectionTests
+  def assert_blocked
+    assert_raises(ActionController::InvalidAuthenticityToken) do
+      yield
+    end
   end
 end
 
@@ -251,15 +204,30 @@ def test_should_allow_all_methods_without_token
       assert_nothing_raised { send(method, :index)}
     end
   end
+
+  test 'should not emit a csrf-token meta tag' do
+    get :meta
+    assert_blank @response.body
+  end
 end
 
+
+
+
+
 class CustomAuthenticityParamControllerTest < ActionController::TestCase
   def setup
+    ActionController::Base.request_forgery_protection_token = :custom_token_name
+    super
+  end
+
+  def teardown
     ActionController::Base.request_forgery_protection_token = :authenticity_token
+    super
   end
 
   def test_should_allow_custom_token
-    post :index, :authenticity_token => 'foobar'
+    post :index, :custom_token_name => 'foobar'
     assert_response :ok
   end
 end