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LibWeb: Avoid UAF parsing an XML document's charset

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The value returned by get_final_encoding() was a temporarily allocated
string which we were holding a view into.
This commit is contained in:
Timothy Flynn 2024-04-03 21:59:03 -04:00 • committed by Andreas Kling
commit 3dee703227
Notes: sideshowbarker 2024-07-17 03:03:37 +09:00
1 changed files with 7 additions and 6 deletions
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13
Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp
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@ -295,21 +295,22 @@ void XMLHttpRequest::set_document_response()
return;
// 5. If finalMIME is an HTML MIME type, then:
Optional<StringView> charset;
Optional<String> charset;
JS::GCPtr<DOM::Document> document;
if (final_mine.is_html()) {
// 5.1. Let charset be the result of get a final encoding for xhr.
charset = MUST(get_final_encoding());
if (auto final_encoding = MUST(get_final_encoding()); final_encoding.has_value())
charset = MUST(String::from_utf8(*final_encoding));
// 5.2. If charset is null, prescan the first 1024 bytes of xhr’s received bytes and if that does not terminate unsuccessfully then let charset be the return value.
document = DOM::Document::create(realm());
if (!charset.has_value())
if (auto found_charset = HTML::run_prescan_byte_stream_algorithm(*document, m_received_bytes); found_charset.has_value())
charset = MUST(String::from_byte_string(found_charset.value())).bytes_as_string_view();
charset = MUST(String::from_byte_string(found_charset.value()));
// 5.3. If charset is null, then set charset to UTF-8.
if (!charset.has_value())
charset = "UTF-8"sv;
charset = "UTF-8"_string;
// 5.4. Let document be a document that represents the result parsing xhr’s received bytes following the rules set forth in the HTML Standard for an HTML parser with scripting disabled and a known definite encoding charset.
auto parser = HTML::HTMLParser::create(*document, m_received_bytes, charset.value());
@ -330,10 +331,10 @@ void XMLHttpRequest::set_document_response()
// 7. If charset is null, then set charset to UTF-8.
if (!charset.has_value())
charset = "UTF-8"sv;
charset = "UTF-8"_string;
// 8. Set document’s encoding to charset.
document->set_encoding(MUST(String::from_utf8(charset.value())));
document->set_encoding(move(charset));
// 9. Set document’s content type to finalMIME.
document->set_content_type(MUST(final_mine.serialized()));