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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40284755): Remove this and spanify to fix the errors.
#pragma allow_unsafe_buffers
#endif
#include "net/spdy/fuzzing/hpack_fuzz_util.h"
#include <algorithm>
#include <cmath>
#include <memory>
#include "base/containers/span.h"
#include "base/numerics/byte_conversions.h"
#include "base/rand_util.h"
#include "net/third_party/quiche/src/quiche/common/http/http_header_block.h"
#include "net/third_party/quiche/src/quiche/http2/hpack/hpack_constants.h"
namespace spdy {
namespace {
using quiche::HttpHeaderBlock;
// Sampled exponential distribution parameters:
// Number of headers in each header set.
const size_t kHeaderCountMean = 7;
const size_t kHeaderCountMax = 50;
// Selected index within list of headers.
const size_t kHeaderIndexMean = 20;
const size_t kHeaderIndexMax = 200;
// Approximate distribution of header name lengths.
const size_t kNameLengthMean = 5;
const size_t kNameLengthMax = 30;
// Approximate distribution of header value lengths.
const size_t kValueLengthMean = 15;
const size_t kValueLengthMax = 75;
} // namespace
using base::RandBytesAsString;
using std::map;
HpackFuzzUtil::GeneratorContext::GeneratorContext() = default;
HpackFuzzUtil::GeneratorContext::~GeneratorContext() = default;
HpackFuzzUtil::Input::Input() = default;
HpackFuzzUtil::Input::~Input() = default;
HpackFuzzUtil::FuzzerContext::FuzzerContext() = default;
HpackFuzzUtil::FuzzerContext::~FuzzerContext() = default;
// static
void HpackFuzzUtil::InitializeGeneratorContext(GeneratorContext* context) {
// Seed the generator with common header fixtures.
context->names.push_back(":authority");
context->names.push_back(":path");
context->names.push_back(":status");
context->names.push_back("cookie");
context->names.push_back("content-type");
context->names.push_back("cache-control");
context->names.push_back("date");
context->names.push_back("user-agent");
context->names.push_back("via");
context->values.push_back("/");
context->values.push_back("/index.html");
context->values.push_back("200");
context->values.push_back("404");
context->values.push_back("");
context->values.push_back("baz=bing; foo=bar; garbage");
context->values.push_back("baz=bing; fizzle=fazzle; garbage");
context->values.push_back("rudolph=the-red-nosed-reindeer");
context->values.push_back("had=a;very_shiny=nose");
context->values.push_back("and\0if\0you\0ever\1saw\0it;");
context->values.push_back("u; would=even;say-it\xffglows");
}
// static
HttpHeaderBlock HpackFuzzUtil::NextGeneratedHeaderSet(
GeneratorContext* context) {
HttpHeaderBlock headers;
size_t header_count =
1 + SampleExponential(kHeaderCountMean, kHeaderCountMax);
for (size_t j = 0; j != header_count; ++j) {
size_t name_index = SampleExponential(kHeaderIndexMean, kHeaderIndexMax);
size_t value_index = SampleExponential(kHeaderIndexMean, kHeaderIndexMax);
std::string name, value;
if (name_index >= context->names.size()) {
context->names.push_back(RandBytesAsString(
1 + SampleExponential(kNameLengthMean, kNameLengthMax)));
name = context->names.back();
} else {
name = context->names[name_index];
}
if (value_index >= context->values.size()) {
context->values.push_back(RandBytesAsString(
1 + SampleExponential(kValueLengthMean, kValueLengthMax)));
value = context->values.back();
} else {
value = context->values[value_index];
}
headers[name] = value;
}
return headers;
}
// static
size_t HpackFuzzUtil::SampleExponential(size_t mean, size_t sanity_bound) {
// Use `1-base::RandDouble()` to avoid log(0).
return std::min(static_cast<size_t>(-std::log(1 - base::RandDouble()) * mean),
sanity_bound);
}
// static
bool HpackFuzzUtil::NextHeaderBlock(Input* input, std::string_view* out) {
// ClusterFuzz may truncate input files if the fuzzer ran out of allocated
// disk space. Be tolerant of these.
if (input->RemainingBytes().size() < sizeof(uint32_t)) {
return false;
}
uint32_t length = base::U32FromBigEndian(input->ReadSpan<sizeof(uint32_t)>());
if (input->RemainingBytes().size() < length) {
return false;
}
auto block = base::as_chars(input->ReadSpan(length));
*out = std::string_view(block.begin(), block.end());
return true;
}
// static
std::string HpackFuzzUtil::HeaderBlockPrefix(size_t block_size) {
std::array<uint8_t, 4u> buf =
base::U32ToBigEndian(base::checked_cast<uint32_t>(block_size));
return std::string(buf.begin(), buf.end());
}
// static
void HpackFuzzUtil::InitializeFuzzerContext(FuzzerContext* context) {
context->first_stage = std::make_unique<HpackDecoderAdapter>();
context->first_stage_handler = std::make_unique<RecordingHeadersHandler>();
context->first_stage->HandleControlFrameHeadersStart(
context->first_stage_handler.get());
context->second_stage = std::make_unique<HpackEncoder>();
context->third_stage = std::make_unique<HpackDecoderAdapter>();
context->third_stage_handler = std::make_unique<RecordingHeadersHandler>();
context->third_stage->HandleControlFrameHeadersStart(
context->third_stage_handler.get());
}
// static
bool HpackFuzzUtil::RunHeaderBlockThroughFuzzerStages(
FuzzerContext* context,
std::string_view input_block) {
// First stage: Decode the input header block. This may fail on invalid input.
if (!context->first_stage->HandleControlFrameHeadersData(
input_block.data(), input_block.size())) {
return false;
}
if (!context->first_stage->HandleControlFrameHeadersComplete()) {
return false;
}
// Second stage: Re-encode the decoded header block. This must succeed.
std::string second_stage_out = context->second_stage->EncodeHeaderBlock(
context->first_stage_handler->decoded_block());
// Third stage: Expect a decoding of the re-encoded block to succeed, but
// don't require it. It's possible for the stage-two encoder to produce an
// output which violates decoder size tolerances.
if (!context->third_stage->HandleControlFrameHeadersData(
second_stage_out.data(), second_stage_out.length())) {
return false;
}
if (!context->third_stage->HandleControlFrameHeadersComplete()) {
return false;
}
return true;
}
// static
void HpackFuzzUtil::FlipBits(uint8_t* buffer,
size_t buffer_length,
size_t flip_per_thousand) {
uint64_t buffer_bit_length = buffer_length * 8u;
uint64_t bits_to_flip = flip_per_thousand * (1 + buffer_bit_length / 1024);
// Iteratively identify & flip offsets in the buffer bit-sequence.
for (uint64_t i = 0; i != bits_to_flip; ++i) {
uint64_t bit_offset = base::RandUint64() % buffer_bit_length;
buffer[bit_offset / 8u] ^= (1 << (bit_offset % 8u));
}
}
} // namespace spdy
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