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