From 89da988da11456a775cb5ae3fbc9802d78134762 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Wed, 27 Dec 2023 11:43:14 +0100
Subject: [PATCH] LibWeb: Honor User-Agent spoofing in Fetch headers

This makes spoofing consistent between legacy ResourceLoader loads,
Fetch loads, and the JavaScript `navigator` APIs.
---
 Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp         | 2 +-
 .../Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.cpp    | 4 ++--
 Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.h | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp b/Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
index 9873b770c9..32355f3bf6 100644
--- a/Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
+++ b/Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
@@ -1354,7 +1354,7 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<PendingResponse>> http_network_or_cache_fet
         if (!http_request->header_list()->contains("User-Agent"sv.bytes())) {
             auto header = Infrastructure::Header {
                 .name = MUST(ByteBuffer::copy("User-Agent"sv.bytes())),
-                .value = TRY_OR_THROW_OOM(vm, Infrastructure::default_user_agent_value()),
+                .value = Infrastructure::default_user_agent_value(),
             };
             TRY_OR_THROW_OOM(vm, http_request->header_list()->append(move(header)));
         }
diff --git a/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.cpp b/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.cpp
index 6d0eccca21..eff6255479 100644
--- a/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.cpp
+++ b/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.cpp
@@ -882,10 +882,10 @@ Optional<RangeHeaderValue> parse_single_range_header_value(ReadonlyBytes value)
 }
 
 // https://fetch.spec.whatwg.org/#default-user-agent-value
-ErrorOr<ByteBuffer> default_user_agent_value()
+ByteBuffer default_user_agent_value()
 {
     // A default `User-Agent` value is an implementation-defined header value for the `User-Agent` header.
-    return ByteBuffer::copy(default_user_agent.bytes());
+    return MUST(ByteBuffer::copy(ResourceLoader::the().user_agent().bytes()));
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.h b/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.h
index 23f31652ed..85d9874670 100644
--- a/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.h
+++ b/Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Headers.h
@@ -93,6 +93,6 @@ struct ExtractHeaderParseFailure {
 [[nodiscard]] ErrorOr<Optional<Vector<ByteBuffer>>> extract_header_values(Header const&);
 [[nodiscard]] ErrorOr<Variant<Vector<ByteBuffer>, ExtractHeaderParseFailure, Empty>> extract_header_list_values(ReadonlyBytes, HeaderList const&);
 [[nodiscard]] Optional<RangeHeaderValue> parse_single_range_header_value(ReadonlyBytes);
-[[nodiscard]] ErrorOr<ByteBuffer> default_user_agent_value();
+[[nodiscard]] ByteBuffer default_user_agent_value();
 
 }