1 /* 2 * Copyright (c) 2017 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef TEST_FUZZERS_FUZZ_DATA_HELPER_H_ 12 #define TEST_FUZZERS_FUZZ_DATA_HELPER_H_ 13 14 #include <limits> 15 16 #include "api/array_view.h" 17 #include "modules/rtp_rtcp/source/byte_io.h" 18 19 namespace webrtc { 20 namespace test { 21 22 // Helper class to take care of the fuzzer input, read from it, and keep track 23 // of when the end of the data has been reached. 24 class FuzzDataHelper { 25 public: 26 explicit FuzzDataHelper(rtc::ArrayView<const uint8_t> data); 27 28 // Returns true if n bytes can be read. CanReadBytes(size_t n)29 bool CanReadBytes(size_t n) const { return data_ix_ + n <= data_.size(); } 30 31 // Reads and returns data of type T. 32 template <typename T> Read()33 T Read() { 34 RTC_CHECK(CanReadBytes(sizeof(T))); 35 T x = ByteReader<T>::ReadLittleEndian(&data_[data_ix_]); 36 data_ix_ += sizeof(T); 37 return x; 38 } 39 40 // Reads and returns data of type T. Returns default_value if not enough 41 // fuzzer input remains to read a T. 42 template <typename T> ReadOrDefaultValue(T default_value)43 T ReadOrDefaultValue(T default_value) { 44 if (!CanReadBytes(sizeof(T))) { 45 return default_value; 46 } 47 return Read<T>(); 48 } 49 50 // Like ReadOrDefaultValue, but replaces the value 0 with default_value. 51 template <typename T> ReadOrDefaultValueNotZero(T default_value)52 T ReadOrDefaultValueNotZero(T default_value) { 53 static_assert(std::is_integral<T>::value, ""); 54 T x = ReadOrDefaultValue(default_value); 55 return x == 0 ? default_value : x; 56 } 57 58 // Returns one of the elements from the provided input array. The selection 59 // is based on the fuzzer input data. If not enough fuzzer data is available, 60 // the method will return the first element in the input array. The reason for 61 // not flagging this as an error is to allow the method to be called from 62 // class constructors, and in constructors we typically do not handle 63 // errors. The code will work anyway, and the fuzzer will likely see that 64 // providing more data will actually make this method return something else. 65 template <typename T, size_t N> SelectOneOf(const T (& select_from)[N])66 T SelectOneOf(const T (&select_from)[N]) { 67 static_assert(N <= std::numeric_limits<uint8_t>::max(), ""); 68 // Read an index between 0 and select_from.size() - 1 from the fuzzer data. 69 uint8_t index = ReadOrDefaultValue<uint8_t>(0) % N; 70 return select_from[index]; 71 } 72 ReadByteArray(size_t bytes)73 rtc::ArrayView<const uint8_t> ReadByteArray(size_t bytes) { 74 if (!CanReadBytes(bytes)) { 75 return rtc::ArrayView<const uint8_t>(nullptr, 0); 76 } 77 const size_t index_to_return = data_ix_; 78 data_ix_ += bytes; 79 return data_.subview(index_to_return, bytes); 80 } 81 82 // If sizeof(T) > BytesLeft then the remaining bytes will be used and the rest 83 // of the object will be zero initialized. 84 template <typename T> CopyTo(T * object)85 void CopyTo(T* object) { 86 memset(object, 0, sizeof(T)); 87 88 size_t bytes_to_copy = std::min(BytesLeft(), sizeof(T)); 89 memcpy(object, data_.data() + data_ix_, bytes_to_copy); 90 data_ix_ += bytes_to_copy; 91 } 92 BytesRead()93 size_t BytesRead() const { return data_ix_; } 94 BytesLeft()95 size_t BytesLeft() const { return data_.size() - data_ix_; } 96 97 private: 98 rtc::ArrayView<const uint8_t> data_; 99 size_t data_ix_ = 0; 100 }; 101 102 } // namespace test 103 } // namespace webrtc 104 105 #endif // TEST_FUZZERS_FUZZ_DATA_HELPER_H_ 106