From 7643a079c08ab41b4449952f779d04e2adb78f9e Mon Sep 17 00:00:00 2001
From: Luke Wilde <luke@ladybird.org>
Date: Thu, 28 Nov 2024 12:30:36 +0000
Subject: [PATCH] LibWeb: Enforce Content Security Policy of Fetch responses

---
 .../BlockingAlgorithms.cpp                    | 35 +++++++++++++++++++
 .../BlockingAlgorithms.h                      |  1 +
 Libraries/LibWeb/Fetch/Fetching/Fetching.cpp  |  4 +--
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.cpp b/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.cpp
index 6b8bf4cd852..6d0f63be370 100644
--- a/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.cpp
+++ b/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.cpp
@@ -89,6 +89,7 @@ void report_content_security_policy_violations_for_request(JS::Realm& realm, GC:
     }
 }
 
+// https://w3c.github.io/webappsec-csp/#should-block-request
 Directives::Directive::Result should_request_be_blocked_by_content_security_policy(JS::Realm& realm, GC::Ref<Fetch::Infrastructure::Request> request)
 {
     // 1. Let CSP list be request’s policy container's CSP list.
@@ -122,4 +123,38 @@ Directives::Directive::Result should_request_be_blocked_by_content_security_poli
     return result;
 }
 
+// https://w3c.github.io/webappsec-csp/#should-block-response
+Directives::Directive::Result should_response_to_request_be_blocked_by_content_security_policy(JS::Realm& realm, GC::Ref<Fetch::Infrastructure::Response> response, GC::Ref<Fetch::Infrastructure::Request> request)
+{
+    // 1. Let CSP list be request’s policy container's CSP list.
+    auto csp_list = request->policy_container().get<GC::Ref<HTML::PolicyContainer>>()->csp_list;
+
+    // 2. Let result be "Allowed".
+    auto result = Directives::Directive::Result::Allowed;
+
+    // 3. For each policy of CSP list:
+    // Spec Note: This portion of the check verifies that the page can load the response. That is, that a Service
+    //            Worker hasn't substituted a file which would violate the page’s CSP.
+    for (auto policy : csp_list->policies()) {
+        // 1. For each directive of policy:
+        for (auto directive : policy->directives()) {
+            // 1. If the result of executing directive’s post-request check is "Blocked", then:
+            if (directive->post_request_check(realm, request, response, policy) == Directives::Directive::Result::Blocked) {
+                // 1. Execute § 5.5 Report a violation on the result of executing § 2.4.2 Create a violation object for
+                //    request, and policy. on request, and policy.
+                auto violation = Violation::create_a_violation_object_for_request_and_policy(realm, request, policy);
+                violation->report_a_violation(realm);
+
+                // 2. If policy’s disposition is "enforce", then set result to "Blocked".
+                if (policy->disposition() == Policy::Disposition::Enforce) {
+                    result = Directives::Directive::Result::Blocked;
+                }
+            }
+        }
+    }
+
+    // 4. Return result.
+    return result;
+}
+
 }
diff --git a/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.h b/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.h
index 019526fd837..6272c58f0a1 100644
--- a/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.h
+++ b/Libraries/LibWeb/ContentSecurityPolicy/BlockingAlgorithms.h
@@ -12,5 +12,6 @@ namespace Web::ContentSecurityPolicy {
 
 void report_content_security_policy_violations_for_request(JS::Realm&, GC::Ref<Fetch::Infrastructure::Request>);
 [[nodiscard]] Directives::Directive::Result should_request_be_blocked_by_content_security_policy(JS::Realm&, GC::Ref<Fetch::Infrastructure::Request>);
+[[nodiscard]] Directives::Directive::Result should_response_to_request_be_blocked_by_content_security_policy(JS::Realm&, GC::Ref<Fetch::Infrastructure::Response>, GC::Ref<Fetch::Infrastructure::Request>);
 
 }
diff --git a/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp b/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
index 66a8d0dc2cc..bdf51051c2d 100644
--- a/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
+++ b/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
@@ -528,8 +528,8 @@ WebIDL::ExceptionOr<GC::Ptr<PendingResponse>> main_fetch(JS::Realm& realm, Infra
             if (!response->is_network_error() && (
                     // - should internalResponse to request be blocked as mixed content
                     MixedContent::should_response_to_request_be_blocked_as_mixed_content(request, internal_response) == Infrastructure::RequestOrResponseBlocking::Blocked
-                    // FIXME: - should internalResponse to request be blocked by Content Security Policy
-                    || false
+                    // - should internalResponse to request be blocked by Content Security Policy
+                    || ContentSecurityPolicy::should_response_to_request_be_blocked_by_content_security_policy(realm, internal_response, request) == ContentSecurityPolicy::Directives::Directive::Result::Blocked
                     // - should internalResponse to request be blocked due to its MIME type
                     || Infrastructure::should_response_to_request_be_blocked_due_to_its_mime_type(internal_response, request) == Infrastructure::RequestOrResponseBlocking::Blocked
                     // - should internalResponse to request be blocked due to nosniff