79 lines · cpp
1//===-- strcmp_fuzz.cpp ---------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8///9/// Fuzzing test for llvm-libc strcmp implementation.10///11//===----------------------------------------------------------------------===//12#include "src/string/strcmp.h"13#include <stddef.h>14#include <stdint.h>15 16// The general structure is to take the value of the first byte, set size1 to17// that value, and add the null terminator. size2 will then contain the rest of18// the bytes in data.19// For example, with inputs (data={2, 6, 4, 8, 0}, size=5):20// size1: data[0] = 221// data1: {2, 6} + '\0' = {2, 6, '\0'}22// size2: size - size1 = 323// data2: {4, 8, '\0'}24extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {25 // Verify the size is at least 1 and the data is null terminated.26 if (!size || data[size - 1] != '\0')27 return 0;28 29 const size_t size1 = (data[0] <= size ? data[0] : size);30 const size_t size2 = size - size1;31 32 // The first size will always be at least 1 since33 // we need to append the null terminator. The second size34 // needs to be checked since it must also contain the null35 // terminator.36 if (!size2)37 return 0;38 39 // Copy the data into new containers.40 // Add one to data1 for null terminator.41 uint8_t *data1 = new uint8_t[size1 + 1];42 uint8_t *data2 = new uint8_t[size2];43 if (!data1 || !data2)44 __builtin_trap();45 46 size_t i;47 for (i = 0; i < size1; ++i)48 data1[i] = data[i];49 data1[size1] = '\0'; // Add null terminator to data1.50 51 for (size_t j = 0; j < size2; ++j)52 data2[j] = data[i++];53 54 const char *s1 = reinterpret_cast<const char *>(data1);55 const char *s2 = reinterpret_cast<const char *>(data2);56 size_t k = 0;57 // Iterate until a null terminator is hit or the character comparison is58 // different.59 while (s1[k] && s2[k] && s1[k] == s2[k])60 ++k;61 62 const unsigned char ch1 = static_cast<unsigned char>(s1[k]);63 const unsigned char ch2 = static_cast<unsigned char>(s2[k]);64 // The expected result should be the difference between the first non-equal65 // characters of s1 and s2. If all characters are equal, the expected result66 // should be '\0' - '\0' = 0.67 if (LIBC_NAMESPACE::strcmp(s1, s2) != ch1 - ch2)68 __builtin_trap();69 70 // Verify reversed operands. This should be the negated value of the previous71 // result, except of course if the previous result was zero.72 if (LIBC_NAMESPACE::strcmp(s2, s1) != ch2 - ch1)73 __builtin_trap();74 75 delete[] data1;76 delete[] data2;77 return 0;78}79