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

actionpack/lib/action_controller/request_forgery_protection.rb

@@ -83,7 +83,11 @@ 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:
@@ -92,12 +96,16 @@ 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      ||
-          !verifiable_request_format? ||
-          form_authenticity_token == params[request_forgery_protection_token]
+        !protect_against_forgery?                            ||
+          request.get?                                       ||
+          form_authenticity_token == form_authenticity_param ||
+          form_authenticity_token == request.headers['X-CSRF-Token']
       end
-    
+
+      def form_authenticity_param
+        params[request_forgery_protection_token]
+      end
+
       def verifiable_request_format?
         !request.content_type.nil? && request.content_type.verify_request?
       end

actionpack/lib/action_view/helpers.rb

@@ -19,6 +19,7 @@ module ClassMethods
     include BenchmarkHelper
     include CacheHelper
     include CaptureHelper
+    include CsrfHelper
     include DateHelper
     include DebugHelper
     include FormHelper

actionpack/lib/action_view/helpers/csrf_helper.rb

+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)}"/>)
+        end
+      end
+    end
+  end
+end

actionpack/test/controller/request_forgery_protection_test.rb

@@ -30,6 +30,10 @@ def unsafe
     render :text => 'pwn'
   end
   
+  def meta
+    render :inline => "<%= csrf_meta_tag %>"
+  end
+
   def rescue_action(e) raise e end
 end
 
@@ -58,7 +62,17 @@ def rescue_action(e) raise e end
   include RequestForgeryProtectionActions
 end
 
-class FreeCookieController < CsrfCookieMonsterController
+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
   
   def index
@@ -103,127 +117,85 @@ def test_should_allow_post_without_token_on_unsafe_action
      assert_response :success
    end
 
-  def test_should_not_allow_html_post_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_raises(ActionController::InvalidAuthenticityToken) { post :index, :format => :html }
-  end
   
-  def test_should_not_allow_html_put_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_raises(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_raises(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_raises(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_raises(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_raises(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_raises(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_raises(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_raises(ActionController::InvalidAuthenticityToken) do
-      @request.env['CONTENT_TYPE'] = Mime::MULTIPART_FORM.to_s
-      delete :index, :format => 'xml'
-    end
+  def test_should_not_allow_xhr_post_without_token
+    assert_blocked { xhr :post, :index }
   end
 
-  def test_should_allow_xhr_post_without_token
-    assert_nothing_raised { xhr :post, :index }
-  end
-  def test_should_not_allow_xhr_post_with_html_without_token
-    @request.env['CONTENT_TYPE'] = Mime::URL_ENCODED_FORM.to_s
-    assert_raise(ActionController::InvalidAuthenticityToken) { 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 }
-  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
+    @request.session[:something_like_user_id] = 1
+    yield
+    assert_nil @request.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
@@ -243,6 +215,11 @@ def session_id() '123' end
     @token = OpenSSL::HMAC.hexdigest(OpenSSL::Digest::Digest.new('SHA1'), 'abc', '123')
     ActionController::Base.request_forgery_protection_token = :authenticity_token
   end
+
+  def test_should_emit_meta_tag 
+    get :meta
+    assert_equal %(<meta name="csrf-param" content="authenticity_token"/>\n<meta name="csrf-token" content="#{@token}"/>), @response.body
+  end
 end
 
 class RequestForgeryProtectionWithoutSecretControllerTest < Test::Unit::TestCase
@@ -257,11 +234,11 @@ def session_id() '123' end
     ActionController::Base.request_forgery_protection_token = :authenticity_token
   end
   
-  # def test_should_raise_error_without_secret
-  #   assert_raises ActionController::InvalidAuthenticityToken do
-  #     get :index
-  #   end
-  # end
+   def test_should_raise_error_without_secret
+     assert_raises ActionController::InvalidAuthenticityToken do
+       get :index
+     end
+   end
 end
 
 class CsrfCookieMonsterControllerTest < Test::Unit::TestCase
@@ -303,25 +280,9 @@ def test_should_allow_all_methods_without_token
       assert_nothing_raised { send(method, :index)}
     end
   end
-end
 
-class SessionOffControllerTest < Test::Unit::TestCase
-  def setup
-    @controller = SessionOffController.new
-    @request    = ActionController::TestRequest.new
-    @response   = ActionController::TestResponse.new
-    @token      = OpenSSL::HMAC.hexdigest(OpenSSL::Digest::Digest.new('SHA1'), 'abc', '123')
+  def test_should_not_emit_meta_tag 
+    get :meta
+    assert @response.body.blank?, "Response body should be blank"
   end
-
-  # TODO: Rewrite this test.
-  # This test was passing but for the wrong reason.
-  # Sessions aren't really being turned off, so an exception was raised
-  # because sessions weren't on - not because the token didn't match.
-  #
-  # def test_should_raise_correct_exception
-  #   @request.session = {} # session(:off) doesn't appear to work with controller tests
-  #   assert_raises(ActionController::InvalidAuthenticityToken) do
-  #     post :index, :authenticity_token => @token, :format => :html
-  #   end
-  # end
 end