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http: reuse HTTPHeaders to parse chunked trailer

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Chunked transfer trailers are just headers that are included
at the end of the request. We can parse and validate them with code
we already use to read headers. In a future commit we will also
be able to use one MAX_HEADERS_SIZE limit to cover both sections.

Even though we parse and validate, we ignore these data.
This commit is contained in:
Matthew Zipkin
2026-07-23 12:38:12 -04:00
parent 902d8908c9
commit 507e528e84
3 changed files with 15 additions and 20 deletions
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28
src/httpserver.cpp
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@@ -298,12 +298,13 @@ void HTTPHeaders::RemoveAll(std::string_view key)
m_headers.erase(moved.begin(), moved.end());
}
bool HTTPHeaders::Read(util::LineReader& reader)
bool HTTPHeaders::Read(util::LineReader& reader, bool write)
{
// Headers https://httpwg.org/specs/rfc9110.html#rfc.section.6.3
// A sequence of Field Lines https://httpwg.org/specs/rfc9110.html#rfc.section.5.2
size_t start{reader.Consumed()};
while (auto maybe_line = reader.ReadLine()) {
if (reader.Consumed() > MAX_HEADERS_SIZE) throw std::runtime_error("HTTP headers exceed size limit");
if (reader.Consumed() - start > MAX_HEADERS_SIZE) throw std::runtime_error("HTTP headers exceed size limit");
const std::string_view& line = *maybe_line;
@@ -336,7 +337,9 @@ bool HTTPHeaders::Read(util::LineReader& reader)
// that can not be empty.
if (key.empty()) throw std::runtime_error("Empty HTTP header name");
Write(std::string(key), std::move(value));
if (write) {
Write(std::string(key), std::move(value));
}
}
return false;
@@ -447,22 +450,11 @@ bool HTTPRequest::LoadBody(LineReader& reader)
// Last chunk has size 0
if (*chunk_size == 0) {
// Allow (but ignore) Chunked Trailer section, by
// reading CRLF-terminated lines until we read an empty line,
// which indicates the end of this request.
// Validate Chunked Trailer section, which is used for
// additional headers sent at the end of the message.
// At this time we ignore and drop these data after validating.
// See https://httpwg.org/specs/rfc9112.html#rfc.section.7.1.2
const size_t trailer_start{reader.Consumed()};
while (true) {
auto maybe_trailer = reader.ReadLine();
if (reader.Consumed() - trailer_start > MAX_HEADERS_SIZE) {
throw std::runtime_error("HTTP chunked trailer exceeds size limit");
}
if (!maybe_trailer) return false;
if (maybe_trailer->empty()) break;
}
// Complete request has been parsed, reader is now pointing
// to beginning of next request or end of the buffer.
return true;
return m_headers.Read(reader, /*write=*/false);
}
// We are still expecting more data for this chunk