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// Copyright (c) 2021 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "quic/core/quic_chaos_protector.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <limits>
#include <memory>
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "quic/core/crypto/quic_random.h"
#include "quic/core/frames/quic_crypto_frame.h"
#include "quic/core/frames/quic_frame.h"
#include "quic/core/frames/quic_padding_frame.h"
#include "quic/core/frames/quic_ping_frame.h"
#include "quic/core/quic_data_reader.h"
#include "quic/core/quic_data_writer.h"
#include "quic/core/quic_framer.h"
#include "quic/core/quic_packets.h"
#include "quic/core/quic_stream_frame_data_producer.h"
#include "quic/platform/api/quic_bug_tracker.h"
#include "common/platform/api/quiche_logging.h"
namespace quic {
QuicChaosProtector::QuicChaosProtector(const QuicCryptoFrame& crypto_frame,
int num_padding_bytes,
size_t packet_size,
QuicFramer* framer,
QuicRandom* random)
: packet_size_(packet_size),
crypto_data_length_(crypto_frame.data_length),
crypto_buffer_offset_(crypto_frame.offset),
level_(crypto_frame.level),
remaining_padding_bytes_(num_padding_bytes),
framer_(framer),
random_(random) {
QUICHE_DCHECK_NE(framer_, nullptr);
QUICHE_DCHECK_NE(framer_->data_producer(), nullptr);
QUICHE_DCHECK_NE(random_, nullptr);
}
QuicChaosProtector::~QuicChaosProtector() {
DeleteFrames(&frames_);
}
absl::optional<size_t> QuicChaosProtector::BuildDataPacket(
const QuicPacketHeader& header,
char* buffer) {
if (!CopyCryptoDataToLocalBuffer()) {
return absl::nullopt;
}
SplitCryptoFrame();
AddPingFrames();
SpreadPadding();
ReorderFrames();
return BuildPacket(header, buffer);
}
WriteStreamDataResult QuicChaosProtector::WriteStreamData(
QuicStreamId id,
QuicStreamOffset offset,
QuicByteCount data_length,
QuicDataWriter* /*writer*/) {
QUIC_BUG(chaos stream) << "This should never be called; id " << id
<< " offset " << offset << " data_length "
<< data_length;
return STREAM_MISSING;
}
bool QuicChaosProtector::WriteCryptoData(EncryptionLevel level,
QuicStreamOffset offset,
QuicByteCount data_length,
QuicDataWriter* writer) {
if (level != level_) {
QUIC_BUG(chaos bad level) << "Unexpected " << level << " != " << level_;
return false;
}
// This is `offset + data_length > buffer_offset_ + buffer_length_`
// but with integer overflow protection.
if (offset < crypto_buffer_offset_ || data_length > crypto_data_length_ ||
offset - crypto_buffer_offset_ > crypto_data_length_ - data_length) {
QUIC_BUG(chaos bad lengths)
<< "Unexpected buffer_offset_ " << crypto_buffer_offset_ << " offset "
<< offset << " buffer_length_ " << crypto_data_length_
<< " data_length " << data_length;
return false;
}
writer->WriteBytes(&crypto_data_buffer_[offset - crypto_buffer_offset_],
data_length);
return true;
}
bool QuicChaosProtector::CopyCryptoDataToLocalBuffer() {
crypto_frame_buffer_ = std::make_unique<char[]>(packet_size_);
frames_.push_back(QuicFrame(
new QuicCryptoFrame(level_, crypto_buffer_offset_, crypto_data_length_)));
// We use |framer_| to serialize the CRYPTO frame in order to extract its
// data from the crypto data producer. This ensures that we reuse the
// usual serialization code path, but has the downside that we then need to
// parse the offset and length in order to skip over those fields.
QuicDataWriter writer(packet_size_, crypto_frame_buffer_.get());
if (!framer_->AppendCryptoFrame(*frames_.front().crypto_frame, &writer)) {
QUIC_BUG(chaos write crypto data);
return false;
}
QuicDataReader reader(crypto_frame_buffer_.get(), writer.length());
uint64_t parsed_offset, parsed_length;
if (!reader.ReadVarInt62(&parsed_offset) ||
!reader.ReadVarInt62(&parsed_length)) {
QUIC_BUG(chaos parse crypto frame);
return false;
}
absl::string_view crypto_data = reader.ReadRemainingPayload();
crypto_data_buffer_ = crypto_data.data();
QUICHE_DCHECK_EQ(parsed_offset, crypto_buffer_offset_);
QUICHE_DCHECK_EQ(parsed_length, crypto_data_length_);
QUICHE_DCHECK_EQ(parsed_length, crypto_data.length());
return true;
}
void QuicChaosProtector::SplitCryptoFrame() {
const int max_overhead_of_adding_a_crypto_frame =
static_cast<int>(QuicFramer::GetMinCryptoFrameSize(
crypto_buffer_offset_ + crypto_data_length_, crypto_data_length_));
// Pick a random number of CRYPTO frames to add.
constexpr uint64_t kMaxAddedCryptoFrames = 10;
const uint64_t num_added_crypto_frames =
random_->InsecureRandUint64() % (kMaxAddedCryptoFrames + 1);
for (uint64_t i = 0; i < num_added_crypto_frames; i++) {
if (remaining_padding_bytes_ < max_overhead_of_adding_a_crypto_frame) {
break;
}
// Pick a random frame and split it by shrinking the picked frame and
// moving the second half of its data to a new frame that is then appended
// to |frames|.
size_t frame_to_split_index =
random_->InsecureRandUint64() % frames_.size();
QuicCryptoFrame* frame_to_split =
frames_[frame_to_split_index].crypto_frame;
if (frame_to_split->data_length <= 1) {
continue;
}
const int frame_to_split_old_overhead =
static_cast<int>(QuicFramer::GetMinCryptoFrameSize(
frame_to_split->offset, frame_to_split->data_length));
const QuicPacketLength frame_to_split_new_data_length =
1 + (random_->InsecureRandUint64() % (frame_to_split->data_length - 1));
const QuicPacketLength new_frame_data_length =
frame_to_split->data_length - frame_to_split_new_data_length;
const QuicStreamOffset new_frame_offset =
frame_to_split->offset + frame_to_split_new_data_length;
frame_to_split->data_length -= new_frame_data_length;
frames_.push_back(QuicFrame(
new QuicCryptoFrame(level_, new_frame_offset, new_frame_data_length)));
const int frame_to_split_new_overhead =
static_cast<int>(QuicFramer::GetMinCryptoFrameSize(
frame_to_split->offset, frame_to_split->data_length));
const int new_frame_overhead =
static_cast<int>(QuicFramer::GetMinCryptoFrameSize(
new_frame_offset, new_frame_data_length));
QUICHE_DCHECK_LE(frame_to_split_new_overhead, frame_to_split_old_overhead);
// Readjust padding based on increased overhead.
remaining_padding_bytes_ -= new_frame_overhead;
remaining_padding_bytes_ -= frame_to_split_new_overhead;
remaining_padding_bytes_ += frame_to_split_old_overhead;
}
}
void QuicChaosProtector::AddPingFrames() {
if (remaining_padding_bytes_ == 0) {
return;
}
constexpr uint64_t kMaxAddedPingFrames = 10;
const uint64_t num_ping_frames =
random_->InsecureRandUint64() %
std::min<uint64_t>(kMaxAddedPingFrames, remaining_padding_bytes_);
for (uint64_t i = 0; i < num_ping_frames; i++) {
frames_.push_back(QuicFrame(QuicPingFrame()));
}
remaining_padding_bytes_ -= static_cast<int>(num_ping_frames);
}
void QuicChaosProtector::ReorderFrames() {
// Walk the array backwards and swap each frame with a random earlier one.
for (size_t i = frames_.size() - 1; i > 0; i--) {
std::swap(frames_[i], frames_[random_->InsecureRandUint64() % (i + 1)]);
}
}
void QuicChaosProtector::SpreadPadding() {
for (auto it = frames_.begin(); it != frames_.end(); ++it) {
const int padding_bytes_in_this_frame =
random_->InsecureRandUint64() % (remaining_padding_bytes_ + 1);
if (padding_bytes_in_this_frame <= 0) {
continue;
}
it = frames_.insert(
it, QuicFrame(QuicPaddingFrame(padding_bytes_in_this_frame)));
++it; // Skip over the padding frame we just added.
remaining_padding_bytes_ -= padding_bytes_in_this_frame;
}
if (remaining_padding_bytes_ > 0) {
frames_.push_back(QuicFrame(QuicPaddingFrame(remaining_padding_bytes_)));
}
}
absl::optional<size_t> QuicChaosProtector::BuildPacket(
const QuicPacketHeader& header,
char* buffer) {
QuicStreamFrameDataProducer* original_data_producer =
framer_->data_producer();
framer_->set_data_producer(this);
size_t length =
framer_->BuildDataPacket(header, frames_, buffer, packet_size_, level_);
framer_->set_data_producer(original_data_producer);
if (length == 0) {
return absl::nullopt;
}
return length;
}
} // namespace quic
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