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-rw-r--r--actionpack/lib/action_controller/metal/request_forgery_protection.rb74
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