| // Copyright 2016 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. |
| |
| #ifndef BASE_TEST_FUZZED_DATA_PROVIDER_H_ |
| #define BASE_TEST_FUZZED_DATA_PROVIDER_H_ |
| |
| #include <limits.h> |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| #include <algorithm> |
| #include <cstring> |
| #include <string> |
| #include <type_traits> |
| #include <utility> |
| #include <vector> |
| |
| // A single-header library providing an utility class to break up an array of |
| // bytes (supposedly provided by a fuzzing engine) for multiple consumers. |
| // 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. |
| |
| // TODO(mmoroz): move this out of //base as it should be an independent library. |
| namespace base { |
| |
| class FuzzedDataProvider { |
| public: |
| typedef uint8_t data_type; |
| |
| // |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. |
| template <typename T = data_type> |
| std::vector<T> ConsumeBytes(size_t num_bytes) { |
| static_assert(sizeof(T) == sizeof(data_type), "Incompatible data type."); |
| |
| num_bytes = std::min(num_bytes, remaining_bytes_); |
| |
| // 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 natual choice for other implementations as well. |
| // To increase the odds even more, we also call |shrink_to_fit| below. |
| std::vector<T> result(num_bytes); |
| std::memcpy(result.data(), data_ptr_, num_bytes); |
| Advance(num_bytes); |
| |
| // 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; |
| } |
| |
| // Prefer using |ConsumeBytes| unless you actually need a std::string object. |
| // Returns a std::string containing |num_bytes| of input data. 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(data_type), |
| "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 the 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; |
| for (size_t i = 0; i < max_length && remaining_bytes_ != 0; ++i) { |
| char next = static_cast<char>(data_ptr_[0]); |
| Advance(1); |
| if (next == '\\' && remaining_bytes_ != 0) { |
| next = static_cast<char>(data_ptr_[0]); |
| Advance(1); |
| if (next != '\\') |
| return result; |
| } |
| result += next; |
| } |
| |
| result.shrink_to_fit(); |
| return result; |
| } |
| |
| // Returns a std::vector containing all remaining bytes of the input data. |
| template <typename T = data_type> |
| 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 value from |array|, consuming as many bytes as needed to do so. |
| // |array| must be a fixed-size array. |
| template <typename T, size_t size> |
| T PickValueInArray(T (&array)[size]) { |
| return array[ConsumeIntegralInRange<size_t>(0, 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; |
| } |
| |
| const data_type* data_ptr_; |
| size_t remaining_bytes_; |
| }; |
| |
| } // namespace base |
| |
| #endif // BASE_TEST_FUZZED_DATA_PROVIDER_H_ |