llvm-project/libc/fuzzing/string/strcmp_fuzz.cpp

79 lines
2.7 KiB
C++

//===-- strcmp_fuzz.cpp ---------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
///
/// Fuzzing test for llvm-libc strcmp implementation.
///
//===----------------------------------------------------------------------===//
#include "src/string/strcmp.h"
#include <stddef.h>
#include <stdint.h>
// The general structure is to take the value of the first byte, set size1 to
// that value, and add the null terminator. size2 will then contain the rest of
// the bytes in data.
// For example, with inputs (data={2, 6, 4, 8, 0}, size=5):
// size1: data[0] = 2
// data1: {2, 6} + '\0' = {2, 6, '\0'}
// size2: size - size1 = 3
// data2: {4, 8, '\0'}
extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
// Verify the size is at least 1 and the data is null terminated.
if (!size || data[size - 1] != '\0')
return 0;
const size_t size1 = (data[0] <= size ? data[0] : size);
const size_t size2 = size - size1;
// The first size will always be at least 1 since
// we need to append the null terminator. The second size
// needs to be checked since it must also contain the null
// terminator.
if (!size2)
return 0;
// Copy the data into new containers.
// Add one to data1 for null terminator.
uint8_t *data1 = new uint8_t[size1 + 1];
uint8_t *data2 = new uint8_t[size2];
if (!data1 || !data2)
__builtin_trap();
size_t i;
for (i = 0; i < size1; ++i)
data1[i] = data[i];
data1[size1] = '\0'; // Add null terminator to data1.
for (size_t j = 0; j < size2; ++j)
data2[j] = data[i++];
const char *s1 = reinterpret_cast<const char *>(data1);
const char *s2 = reinterpret_cast<const char *>(data2);
size_t k = 0;
// Iterate until a null terminator is hit or the character comparison is
// different.
while (s1[k] && s2[k] && s1[k] == s2[k])
++k;
const unsigned char ch1 = static_cast<unsigned char>(s1[k]);
const unsigned char ch2 = static_cast<unsigned char>(s2[k]);
// The expected result should be the difference between the first non-equal
// characters of s1 and s2. If all characters are equal, the expected result
// should be '\0' - '\0' = 0.
if (__llvm_libc::strcmp(s1, s2) != ch1 - ch2)
__builtin_trap();
// Verify reversed operands. This should be the negated value of the previous
// result, except of course if the previous result was zero.
if (__llvm_libc::strcmp(s2, s1) != ch2 - ch1)
__builtin_trap();
delete[] data1;
delete[] data2;
return 0;
}