86 lines · cpp
1//===-- strstr_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 strstr implementation.10///11//===----------------------------------------------------------------------===//12 13#include "src/string/strlen.h"14#include "src/string/strstr.h"15#include <stddef.h>16#include <stdint.h>17 18// Simple loop to compare two strings up to a size n.19static int simple_memcmp(const char *left, const char *right, size_t n) {20 for (; n && *left == *right; ++left, ++right, --n)21 ;22 return n ? *left - *right : 0;23}24 25// The general structure is to take the value of the first byte, set size1 to26// that value, and add the null terminator. size2 will then contain the rest of27// the bytes in data.28// For example, with inputs (data={2, 6, 4, 8, 0}, size=5):29// size1: data[0] = 230// data1: {2, 6} + '\0' = {2, 6, '\0'}31// size2: size - size1 = 332// data2: {4, 8, '\0'}33extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {34 // Verify the size is at least 1 and the data is null terminated.35 if (!size || data[size - 1] != '\0')36 return 0;37 const size_t size1 = (data[0] <= size ? data[0] : size);38 // The first size will always be at least 1 since39 // we need to append the null terminator. The second size40 // needs to be checked since it must also contain the null41 // terminator.42 if (size - size1 == 0)43 return 0;44 45 // Copy the data into a new container.46 uint8_t *container = new uint8_t[size1 + 1];47 if (!container)48 __builtin_trap();49 50 size_t i;51 for (i = 0; i < size1; ++i)52 container[i] = data[i];53 container[size1] = '\0'; // Add null terminator to container.54 55 const char *needle = reinterpret_cast<const char *>(container);56 const char *haystack = reinterpret_cast<const char *>(data + i);57 const char *result = LIBC_NAMESPACE::strstr(haystack, needle);58 59 // A null terminator may exist earlier in each, so this needs to be recorded.60 const size_t haystack_size = LIBC_NAMESPACE::strlen(haystack);61 const size_t needle_size = LIBC_NAMESPACE::strlen(needle);62 63 if (result) {64 // The needle is in the haystack.65 // 1. Verify that the result matches the needle.66 if (simple_memcmp(needle, result, needle_size) != 0)67 __builtin_trap();68 69 const char *haystack_ptr = haystack;70 // 2. Verify that the result is the first occurrence of the needle.71 for (; haystack_ptr != result; ++haystack_ptr) {72 if (simple_memcmp(needle, haystack_ptr, needle_size) == 0)73 __builtin_trap(); // There was an earlier occurrence of the needle.74 }75 } else {76 // No result was found. Verify that the needle doesn't exist within the77 // haystack.78 for (size_t i = 0; i + needle_size < haystack_size; ++i) {79 if (simple_memcmp(needle, haystack + i, needle_size) == 0)80 __builtin_trap(); // There was an earlier occurrence of the needle.81 }82 }83 delete[] container;84 return 0;85}86