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src/test/fuzz/FuzzedDataProvider.h
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//===- FuzzedDataProvider.h - Utility header for fuzz targets ---*- C++ -* ===// | |||||
// | |||||
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | |||||
// See https://llvm.org/LICENSE.txt for license information. | |||||
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | |||||
// | |||||
//===----------------------------------------------------------------------===// | |||||
// A single header library providing an utility class to break up an array of | |||||
// bytes. Whenever run on the same input, provides the same output, as long as | |||||
// its methods are called in the same order, with the same arguments. | |||||
//===----------------------------------------------------------------------===// | |||||
#ifndef LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_ | |||||
#define LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_ | |||||
#include <climits> | |||||
#include <cstddef> | |||||
#include <cstdint> | |||||
#include <algorithm> | |||||
#include <cstring> | |||||
#include <initializer_list> | |||||
#include <string> | |||||
#include <type_traits> | |||||
#include <utility> | |||||
#include <vector> | |||||
class FuzzedDataProvider { | |||||
public: | |||||
// |data| is an array of length |size| that the FuzzedDataProvider wraps to | |||||
// provide more granular access. |data| must outlive the FuzzedDataProvider. | |||||
FuzzedDataProvider(const uint8_t *data, size_t size) | |||||
: data_ptr_(data), remaining_bytes_(size) {} | |||||
~FuzzedDataProvider() = default; | |||||
// Returns a std::vector containing |num_bytes| of input data. If fewer than | |||||
// |num_bytes| of data remain, returns a shorter std::vector containing all | |||||
// of the data that's left. Can be used with any byte sized type, such as | |||||
// char, uint8_t, uint8_t, etc. | |||||
template <typename T> std::vector<T> ConsumeBytes(size_t num_bytes) { | |||||
num_bytes = std::min(num_bytes, remaining_bytes_); | |||||
return ConsumeBytes<T>(num_bytes, num_bytes); | |||||
} | |||||
// Similar to |ConsumeBytes|, but also appends the terminator value at the | |||||
// end of the resulting vector. Useful, when a mutable null-terminated | |||||
// C-string is needed, for example. But that is a rare case. Better avoid | |||||
// it, if possible, and prefer using |ConsumeBytes| or | |||||
// |ConsumeBytesAsString| methods. | |||||
template <typename T> | |||||
std::vector<T> ConsumeBytesWithTerminator(size_t num_bytes, | |||||
T terminator = 0) { | |||||
num_bytes = std::min(num_bytes, remaining_bytes_); | |||||
std::vector<T> result = ConsumeBytes<T>(num_bytes + 1, num_bytes); | |||||
result.back() = terminator; | |||||
return result; | |||||
} | |||||
// Returns a std::string containing |num_bytes| of input data. Using this | |||||
// and | |||||
// |.c_str()| on the resulting string is the best way to get an immutable | |||||
// null-terminated C string. If fewer than |num_bytes| of data remain, | |||||
// returns a shorter std::string containing all of the data that's left. | |||||
std::string ConsumeBytesAsString(size_t num_bytes) { | |||||
static_assert( | |||||
sizeof(std::string::value_type) == sizeof(uint8_t), | |||||
"ConsumeBytesAsString cannot convert the data to a string."); | |||||
num_bytes = std::min(num_bytes, remaining_bytes_); | |||||
std::string result( | |||||
reinterpret_cast<const std::string::value_type *>(data_ptr_), | |||||
num_bytes); | |||||
Advance(num_bytes); | |||||
return result; | |||||
} | |||||
// Returns a number in the range [min, max] by consuming bytes from the | |||||
// input data. The value might not be uniformly distributed in the given | |||||
// range. If there's no input data left, always returns |min|. |min| must | |||||
// be less than or equal to |max|. | |||||
template <typename T> T ConsumeIntegralInRange(T min, T max) { | |||||
static_assert(std::is_integral<T>::value, | |||||
"An integral type is required."); | |||||
static_assert(sizeof(T) <= sizeof(uint64_t), | |||||
"Unsupported integral type."); | |||||
if (min > max) abort(); | |||||
// Use the biggest type possible to hold the range and the result. | |||||
uint64_t range = static_cast<uint64_t>(max) - min; | |||||
uint64_t result = 0; | |||||
size_t offset = 0; | |||||
while (offset < sizeof(T) * CHAR_BIT && (range >> offset) > 0 && | |||||
remaining_bytes_ != 0) { | |||||
// Pull bytes off the end of the seed data. Experimentally, this | |||||
// seems to allow the fuzzer to more easily explore the input space. | |||||
// This makes sense, since it works by modifying inputs that caused | |||||
// new code to run, and this data is often used to encode length of | |||||
// data read by |ConsumeBytes|. Separating out read lengths makes it | |||||
// easier modify the contents of the data that is actually read. | |||||
--remaining_bytes_; | |||||
result = (result << CHAR_BIT) | data_ptr_[remaining_bytes_]; | |||||
offset += CHAR_BIT; | |||||
} | |||||
// Avoid division by 0, in case |range + 1| results in overflow. | |||||
if (range != std::numeric_limits<decltype(range)>::max()) | |||||
result = result % (range + 1); | |||||
return static_cast<T>(min + result); | |||||
} | |||||
// Returns a std::string of length from 0 to |max_length|. When it runs out | |||||
// of input data, returns what remains of the input. Designed to be more | |||||
// stable with respect to a fuzzer inserting characters than just picking a | |||||
// random length and then consuming that many bytes with |ConsumeBytes|. | |||||
std::string ConsumeRandomLengthString(size_t max_length) { | |||||
// Reads bytes from the start of |data_ptr_|. Maps "\\" to "\", and maps | |||||
// "\" followed by anything else to the end of the string. As a result | |||||
// of this logic, a fuzzer can insert characters into the string, and | |||||
// the string will be lengthened to include those new characters, | |||||
// resulting in a more stable fuzzer than picking the length of a string | |||||
// independently from picking its contents. | |||||
std::string result; | |||||
// Reserve the anticipated capaticity to prevent several reallocations. | |||||
result.reserve(std::min(max_length, remaining_bytes_)); | |||||
for (size_t i = 0; i < max_length && remaining_bytes_ != 0; ++i) { | |||||
char next = ConvertUnsignedToSigned<char>(data_ptr_[0]); | |||||
Advance(1); | |||||
if (next == '\\' && remaining_bytes_ != 0) { | |||||
next = ConvertUnsignedToSigned<char>(data_ptr_[0]); | |||||
Advance(1); | |||||
if (next != '\\') break; | |||||
} | |||||
result += next; | |||||
} | |||||
result.shrink_to_fit(); | |||||
return result; | |||||
} | |||||
// Returns a std::vector containing all remaining bytes of the input data. | |||||
template <typename T> std::vector<T> ConsumeRemainingBytes() { | |||||
return ConsumeBytes<T>(remaining_bytes_); | |||||
} | |||||
// Prefer using |ConsumeRemainingBytes| unless you actually need a | |||||
// std::string object. Returns a std::vector containing all remaining bytes | |||||
// of the input data. | |||||
std::string ConsumeRemainingBytesAsString() { | |||||
return ConsumeBytesAsString(remaining_bytes_); | |||||
} | |||||
// Returns a number in the range [Type's min, Type's max]. The value might | |||||
// not be uniformly distributed in the given range. If there's no input data | |||||
// left, always returns |min|. | |||||
template <typename T> T ConsumeIntegral() { | |||||
return ConsumeIntegralInRange(std::numeric_limits<T>::min(), | |||||
std::numeric_limits<T>::max()); | |||||
} | |||||
// Reads one byte and returns a bool, or false when no data remains. | |||||
bool ConsumeBool() { return 1 & ConsumeIntegral<uint8_t>(); } | |||||
// Returns a copy of a value selected from a fixed-size |array|. | |||||
template <typename T, size_t size> | |||||
T PickValueInArray(const T (&array)[size]) { | |||||
static_assert(size > 0, "The array must be non empty."); | |||||
return array[ConsumeIntegralInRange<size_t>(0, size - 1)]; | |||||
} | |||||
template <typename T> | |||||
T PickValueInArray(std::initializer_list<const T> list) { | |||||
// static_assert(list.size() > 0, "The array must be non empty."); | |||||
return *(list.begin() + | |||||
ConsumeIntegralInRange<size_t>(0, list.size() - 1)); | |||||
} | |||||
// Return an enum value. The enum must start at 0 and be contiguous. It must | |||||
// also contain |kMaxValue| aliased to its largest (inclusive) value. Such | |||||
// as: enum class Foo { SomeValue, OtherValue, kMaxValue = OtherValue }; | |||||
template <typename T> T ConsumeEnum() { | |||||
static_assert(std::is_enum<T>::value, "|T| must be an enum type."); | |||||
return static_cast<T>(ConsumeIntegralInRange<uint32_t>( | |||||
0, static_cast<uint32_t>(T::kMaxValue))); | |||||
} | |||||
// Reports the remaining bytes available for fuzzed input. | |||||
size_t remaining_bytes() { return remaining_bytes_; } | |||||
private: | |||||
FuzzedDataProvider(const FuzzedDataProvider &) = delete; | |||||
FuzzedDataProvider &operator=(const FuzzedDataProvider &) = delete; | |||||
void Advance(size_t num_bytes) { | |||||
if (num_bytes > remaining_bytes_) abort(); | |||||
data_ptr_ += num_bytes; | |||||
remaining_bytes_ -= num_bytes; | |||||
} | |||||
template <typename T> | |||||
std::vector<T> ConsumeBytes(size_t size, size_t num_bytes_to_consume) { | |||||
static_assert(sizeof(T) == sizeof(uint8_t), "Incompatible data type."); | |||||
// The point of using the size-based constructor below is to increase | |||||
// the odds of having a vector object with capacity being equal to the | |||||
// length. That part is always implementation specific, but at least | |||||
// both libc++ and libstdc++ allocate the requested number of bytes in | |||||
// that constructor, which seems to be a natural choice for other | |||||
// implementations as well. To increase the odds even more, we also call | |||||
// |shrink_to_fit| below. | |||||
std::vector<T> result(size); | |||||
std::memcpy(result.data(), data_ptr_, num_bytes_to_consume); | |||||
Advance(num_bytes_to_consume); | |||||
// Even though |shrink_to_fit| is also implementation specific, we | |||||
// expect it to provide an additional assurance in case vector's | |||||
// constructor allocated a buffer which is larger than the actual amount | |||||
// of data we put inside it. | |||||
result.shrink_to_fit(); | |||||
return result; | |||||
} | |||||
template <typename TS, typename TU> TS ConvertUnsignedToSigned(TU value) { | |||||
static_assert(sizeof(TS) == sizeof(TU), "Incompatible data types."); | |||||
static_assert(!std::numeric_limits<TU>::is_signed, | |||||
"Source type must be unsigned."); | |||||
// TODO(Dor1s): change to `if constexpr` once C++17 becomes mainstream. | |||||
if (std::numeric_limits<TS>::is_modulo) return static_cast<TS>(value); | |||||
// Avoid using implementation-defined unsigned to signer conversions. | |||||
// To learn more, see https://stackoverflow.com/questions/13150449. | |||||
if (value <= std::numeric_limits<TS>::max()) | |||||
return static_cast<TS>(value); | |||||
else { | |||||
constexpr auto TS_min = std::numeric_limits<TS>::min(); | |||||
return TS_min + static_cast<char>(value - TS_min); | |||||
} | |||||
} | |||||
const uint8_t *data_ptr_; | |||||
size_t remaining_bytes_; | |||||
}; | |||||
#endif // LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_ |