1  // Copyright (c) 2023-present The Bitcoin Core developers
 2  // Distributed under the MIT software license, see the accompanying
 3  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 4  
 5  #include <test/util/random.h>
 6  
 7  #include <logging.h>
 8  #include <random.h>
 9  #include <uint256.h>
10  #include <util/check.h>
11  
12  #include <cstdlib>
13  #include <iostream>
14  
15  std::atomic<bool> g_seeded_g_prng_zero{false};
16  
17  extern void MakeRandDeterministicDANGEROUS(const uint256& seed) noexcept;
18  
19  void SeedRandomStateForTest(SeedRand seedtype)
20  {
21      constexpr auto RANDOM_CTX_SEED{"RANDOM_CTX_SEED"};
22  
23      // Do this once, on the first call, regardless of seedtype, because once
24      // MakeRandDeterministicDANGEROUS is called, the output of GetRandHash is
25      // no longer truly random. It should be enough to get the seed once for the
26      // process.
27      static const auto g_ctx_seed = []() -> std::optional<uint256> {
28          if (EnableFuzzDeterminism()) return {};
29          // If RANDOM_CTX_SEED is set, use that as seed.
30          if (const char* num{std::getenv(RANDOM_CTX_SEED)}) {
31              if (auto num_parsed{uint256::FromUserHex(num)}) {
32                  return *num_parsed;
33              } else {
34                  std::cerr << RANDOM_CTX_SEED << " must consist of up to " << uint256::size() * 2 << " hex digits (\"0x\" prefix allowed), it was set to: '" << num << "'.\n";
35                  std::abort();
36              }
37          }
38          // Otherwise use a (truly) random value.
39          return GetRandHash();
40      }();
41  
42      g_seeded_g_prng_zero = seedtype == SeedRand::ZEROS;
43      if (EnableFuzzDeterminism()) {
44          Assert(g_seeded_g_prng_zero); // Only SeedRandomStateForTest(SeedRand::ZEROS) is allowed in fuzz tests
45          Assert(!g_used_g_prng);       // The global PRNG must not have been used before SeedRandomStateForTest(SeedRand::ZEROS)
46      }
47      const uint256& seed{seedtype == SeedRand::FIXED_SEED ? g_ctx_seed.value() : uint256::ZERO};
48      LogInfo("Setting random seed for current tests to %s=%s\n", RANDOM_CTX_SEED, seed.GetHex());
49      MakeRandDeterministicDANGEROUS(seed);
50  }