diff options
Diffstat (limited to 'actionpack/lib/action_controller/metal/request_forgery_protection.rb')
| -rw-r--r-- | actionpack/lib/action_controller/metal/request_forgery_protection.rb | 74 |
1 files changed, 61 insertions, 13 deletions
diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb index bd64b1f812..8cdb9a7655 100644 --- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb +++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb @@ -5,14 +5,24 @@ module ActionController #:nodoc: class InvalidAuthenticityToken < ActionControllerError #:nodoc: end + class InvalidCrossOriginRequest < ActionControllerError #:nodoc: + end + # Controller actions are protected from Cross-Site Request Forgery (CSRF) attacks # by including a token in the rendered html for your application. This token is # stored as a random string in the session, to which an attacker does not have # access. When a request reaches your application, \Rails verifies the received # token with the token in the session. Only HTML and JavaScript requests are checked, # so this will not protect your XML API (presumably you'll have a different - # authentication scheme there anyway). Also, GET requests are not protected as these - # should be idempotent. + # authentication scheme there anyway). + # + # GET requests are not protected since they don't have side effects like writing + # to the database and don't leak sensitive information. JavaScript requests are + # an exception: a third-party site can use a <script> tag to reference a JavaScript + # URL on your site. When your JavaScript response loads on their site, it executes. + # With carefully crafted JavaScript on their end, sensitive data in your JavaScript + # response may be extracted. To prevent this, only XmlHttpRequest (known as XHR or + # Ajax) requests are allowed to make GET requests for JavaScript responses. # # It's important to remember that XML or JSON requests are also affected and if # you're building an API you'll need something like: @@ -65,17 +75,16 @@ module ActionController #:nodoc: module ClassMethods # Turn on request forgery protection. Bear in mind that only non-GET, HTML/JavaScript requests are checked. # + # class ApplicationController < ActionController::Base + # protect_from_forgery + # end + # # class FooController < ApplicationController # protect_from_forgery except: :index # - # You can disable csrf protection on controller-by-controller basis: - # + # You can disable CSRF protection on controller by skipping the verification before_action: # skip_before_action :verify_authenticity_token # - # It can also be disabled for specific controller actions: - # - # skip_before_action :verify_authenticity_token, except: [:create] - # # Valid Options: # # * <tt>:only/:except</tt> - Passed to the <tt>before_action</tt> call. Set which actions are verified. @@ -89,6 +98,7 @@ module ActionController #:nodoc: self.forgery_protection_strategy = protection_method_class(options[:with] || :null_session) self.request_forgery_protection_token ||= :authenticity_token prepend_before_action :verify_authenticity_token, options + append_after_action :verify_same_origin_request end private @@ -169,18 +179,56 @@ module ActionController #:nodoc: end protected + # The actual before_action that is used to verify the CSRF token. + # Don't override this directly. Provide your own forgery protection + # strategy instead. If you override, you'll disable same-origin + # `<script>` verification. + # + # Lean on the protect_from_forgery declaration to mark which actions are + # due for same-origin request verification. If protect_from_forgery is + # enabled on an action, this before_action flags its after_action to + # verify that JavaScript responses are for XHR requests, ensuring they + # follow the browser's same-origin policy. + def verify_authenticity_token + @marked_for_same_origin_verification = true + + if !verified_request? + logger.warn "Can't verify CSRF token authenticity" if logger + handle_unverified_request + end + end + def handle_unverified_request forgery_protection_strategy.new(self).handle_unverified_request end - # The actual before_action that is used. Modify this to change how you handle unverified requests. - def verify_authenticity_token - unless verified_request? - logger.warn "Can't verify CSRF token authenticity" if logger - handle_unverified_request + CROSS_ORIGIN_JAVASCRIPT_WARNING = "Security warning: an embedded " \ + "<script> tag on another site requested protected JavaScript. " \ + "If you know what you're doing, go ahead and disable forgery " \ + "protection on this action to permit cross-origin JavaScript embedding." + private_constant :CROSS_ORIGIN_JAVASCRIPT_WARNING + + # If `verify_authenticity_token` was run (indicating that we have + # forgery protection enabled for this request) then also verify that + # we aren't serving an unauthorized cross-origin response. + def verify_same_origin_request + if marked_for_same_origin_verification? && non_xhr_javascript_response? + logger.warn CROSS_ORIGIN_JAVASCRIPT_WARNING if logger + raise ActionController::InvalidCrossOriginRequest, CROSS_ORIGIN_JAVASCRIPT_WARNING end end + # If the `verify_authenticity_token` before_action ran, verify that + # JavaScript responses are only served to same-origin GET requests. + def marked_for_same_origin_verification? + defined? @marked_for_same_origin_verification + end + + # Check for cross-origin JavaScript responses. + def non_xhr_javascript_response? + content_type =~ %r(\Atext/javascript) && !request.xhr? + end + # Returns true or false if a request is verified. Checks: # # * is it a GET or HEAD request? Gets should be safe and idempotent |