1// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2// See https://llvm.org/LICENSE.txt for license information.
3// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4
5// This test computes a checksum of the data (all but the last 4 bytes),
6// and then compares the last 4 bytes with the computed value.
7// A fuzzer with cmp traces is expected to defeat this check.
8#include <cstdint>
9#include <cstdio>
10#include <cstdlib>
11#include <cstring>
12
13// A modified jenkins_one_at_a_time_hash initialized by non-zero,
14// so that simple_hash(0) != 0. See also
15// https://en.wikipedia.org/wiki/Jenkins_hash_function
16static uint32_t simple_hash(const uint8_t *Data, size_t Size) {
17 uint32_t Hash = 0x12039854;
18 for (uint32_t i = 0; i < Size; i++) {
19 Hash += Data[i];
20 Hash += (Hash << 10);
21 Hash ^= (Hash >> 6);
22 }
23 Hash += (Hash << 3);
24 Hash ^= (Hash >> 11);
25 Hash += (Hash << 15);
26 return Hash;
27}
28
29extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
30 if (Size < 14)
31 return 0;
32
33 uint32_t Hash = simple_hash(&Data[0], Size - 4);
34 uint32_t Want = reinterpret_cast<const uint32_t *>(&Data[Size - 4])[0];
35 if (Hash != Want)
36 return 0;
37 fprintf(stderr, "BINGO; simple_hash defeated: %x == %x\n", (unsigned int)Hash,
38 (unsigned int)Want);
39 exit(1);
40 return 0;
41}
42