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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
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NZKoz committed Jan 17, 2011
1 parent abe9773 commit 7e86f9b4d2b7dfa974c10ae7e6d8ef90f3d77f06
@@ -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

This comment has been minimized.

@dlitz

dlitz Sep 21, 2011

Doesn't this create a denial-of-service vulnerability? A rogue site can force you to log out, now.

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
@@ -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
@@ -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
@@ -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

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