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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/websockets/websocket_chunk_assembler.h"
#include "base/compiler_specific.h"
#include "base/containers/extend.h"
#include "base/containers/span.h"
#include "base/types/expected.h"
#include "net/base/net_errors.h"
#include "net/websockets/websocket_errors.h"
#include "net/websockets/websocket_frame.h"
namespace net {
namespace {
// This uses type uint64_t to match the definition of
// WebSocketFrameHeader::payload_length in websocket_frame.h.
constexpr uint64_t kMaxControlFramePayload = 125;
// Utility function to create a WebSocketFrame
std::unique_ptr<WebSocketFrame> MakeWebSocketFrame(
const WebSocketFrameHeader& header,
base::span<uint8_t> payload) {
auto frame = std::make_unique<WebSocketFrame>(header.opcode);
frame->header.CopyFrom(header);
if (header.masked) {
MaskWebSocketFramePayload(header.masking_key, 0, payload);
}
frame->payload = payload;
return frame;
}
} // namespace
WebSocketChunkAssembler::WebSocketChunkAssembler() = default;
WebSocketChunkAssembler::~WebSocketChunkAssembler() = default;
void WebSocketChunkAssembler::Reset() {
current_frame_header_.reset();
chunk_buffer_.clear();
state_ = AssemblyState::kInitialFrame;
}
base::expected<std::unique_ptr<WebSocketFrame>, net::Error>
WebSocketChunkAssembler::HandleChunk(
std::unique_ptr<WebSocketFrameChunk> chunk) {
if (state_ == AssemblyState::kMessageFinished) {
Reset();
}
if (chunk->header) {
CHECK_EQ(state_, AssemblyState::kInitialFrame);
CHECK(!current_frame_header_);
current_frame_header_ = std::move(chunk->header);
}
CHECK(current_frame_header_);
const WebSocketFrameHeader::OpCode opcode = current_frame_header_->opcode;
const bool is_control_frame =
WebSocketFrameHeader::IsKnownControlOpCode(opcode) ||
WebSocketFrameHeader::IsReservedControlOpCode(opcode);
const bool is_data_frame = WebSocketFrameHeader::IsKnownDataOpCode(opcode) ||
WebSocketFrameHeader::IsReservedDataOpCode(opcode);
CHECK(is_control_frame || is_data_frame);
if (is_control_frame && !current_frame_header_->final) {
return base::unexpected(ERR_WS_PROTOCOL_ERROR);
}
if (is_control_frame &&
current_frame_header_->payload_length > kMaxControlFramePayload) {
return base::unexpected(ERR_WS_PROTOCOL_ERROR);
}
const bool is_first_chunk = state_ == AssemblyState::kInitialFrame;
const bool is_final_chunk = chunk->final_chunk;
const bool is_empty_middle_chunk =
!is_first_chunk && !is_final_chunk && chunk->payload.empty();
if (is_empty_middle_chunk) {
return base::unexpected(ERR_IO_PENDING);
}
// Handle single-chunk frame without buffering
const bool is_single_chunk_frame = is_first_chunk && is_final_chunk;
if (is_single_chunk_frame) {
CHECK_EQ(current_frame_header_->payload_length, chunk->payload.size());
auto frame = MakeWebSocketFrame(*current_frame_header_,
base::as_writable_bytes(chunk->payload));
state_ = AssemblyState::kMessageFinished;
return frame;
}
// For data frames, process each chunk separately without accumulating all
// in memory (streaming to render process)
if (is_data_frame) {
auto frame = MakeWebSocketFrame(*current_frame_header_,
base::as_writable_bytes(chunk->payload));
// Since we are synthesizing a frame that the origin server didn't send,
// we need to comply with the requirement ourselves.
if (state_ == AssemblyState::kContinuationFrame) {
// This is needed to satisfy the constraint of RFC7692:
//
// An endpoint MUST NOT set the "Per-Message Compressed" bit of control
// frames and non-first fragments of a data message.
frame->header.opcode = WebSocketFrameHeader::kOpCodeContinuation;
frame->header.reserved1 = false;
frame->header.reserved2 = false;
frame->header.reserved3 = false;
}
frame->header.payload_length = chunk->payload.size();
frame->header.final = current_frame_header_->final && chunk->final_chunk;
if (is_final_chunk) {
state_ = AssemblyState::kMessageFinished;
} else {
state_ = AssemblyState::kContinuationFrame;
}
return frame;
}
CHECK(is_control_frame && current_frame_header_->final);
// Control frames should be processed as a unit as they are small in size.
base::Extend(chunk_buffer_, chunk->payload);
if (!chunk->final_chunk) {
state_ = AssemblyState::kControlFrame;
return base::unexpected(ERR_IO_PENDING);
}
state_ = AssemblyState::kMessageFinished;
CHECK_EQ(current_frame_header_->payload_length, chunk_buffer_.size());
auto frame = MakeWebSocketFrame(*current_frame_header_,
base::as_writable_byte_span(chunk_buffer_));
state_ = AssemblyState::kMessageFinished;
return frame;
}
} // namespace net
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