Use request object for context if there's no controller

There is no controller instance when using a redirect route or a
mounted rack application so pass the request object as the context
when resolving dynamic CSP sources in this scenario.

Fixes #34200.

actionpack/CHANGELOG.md

+*   Use request object for context if there's no controller
+
+    There is no controller instance when using a redirect route or a
+    mounted rack application so pass the request object as the context
+    when resolving dynamic CSP sources in this scenario.
+    
+    Fixes #34200.
+    
+    *Andrew White*
+
 *   Apply mapping to symbols returned from dynamic CSP sources
 
     Previously if a dynamic source returned a symbol such as :self it

actionpack/lib/action_dispatch/http/content_security_policy.rb

@@ -22,7 +22,8 @@ def call(env)
 
         if policy = request.content_security_policy
           nonce = request.content_security_policy_nonce
-          headers[header_name(request)] = policy.build(request.controller_instance, nonce)
+          context = request.controller_instance || request
+          headers[header_name(request)] = policy.build(context, nonce)
         end
 
         response

actionpack/test/dispatch/content_security_policy_test.rb

@@ -260,6 +260,7 @@ def index
   ROUTES.draw do
     scope module: "default_content_security_policy_integration_test" do
       get "/", to: "policy#index"
+      get "/redirect", to: redirect("/")
     end
   end
 
@@ -295,14 +296,19 @@ def app
   def test_adds_nonce_to_script_src_content_security_policy_only_once
     get "/"
     get "/"
+    assert_response :success
+    assert_policy "default-src 'self'; script-src https: 'nonce-iyhD0Yc0W+c='"
+  end
+
+  def test_redirect_works_with_dynamic_sources
+    get "/redirect"
+    assert_response :redirect
     assert_policy "default-src 'self'; script-src https: 'nonce-iyhD0Yc0W+c='"
   end
 
   private
 
     def assert_policy(expected, report_only: false)
-      assert_response :success
-
       if report_only
         expected_header = "Content-Security-Policy-Report-Only"
         unexpected_header = "Content-Security-Policy"