Add a better error message when a "null" Origin header occurs

1 files changed, 10 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
index d6cd5fd9e0..b2e6f86eeb 100644
--- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb
+++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
@@ -414,11 +414,21 @@ module ActionController #:nodoc:
         allow_forgery_protection
       end
 
+      NULL_ORIGIN_MESSAGE = <<-MSG.strip_heredoc
+        The browser returned a 'null' origin for a request with origin-based forgery protection turned on. This usually
+        means you have the 'no-referrer' Referrer-Policy header enabled, or that you the request came from a site that
+        refused to give its origin. This makes it impossible for Rails to verify the source of the requests. Likely the
+        best solution is to change your referrer policy to something less strict like same-origin or strict-same-origin.
+        If you cannot change the referrer policy, you can disable origin checking with the
+        Rails.application.config.action_controller.forgery_protection_origin_check setting.
+      MSG
+
       # Checks if the request originated from the same origin by looking at the
       # Origin header.
       def valid_request_origin? # :doc:
         if forgery_protection_origin_check
           # We accept blank origin headers because some user agents don't send it.
+          raise InvalidAuthenticityToken, NULL_ORIGIN_MESSAGE if request.origin == "null"
           request.origin.nil? || request.origin == request.base_url
         else
           true