1  // Copyright (c) 2025-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 <consensus/merkle.h>
 6  #include <test/fuzz/fuzz.h>
 7  #include <test/fuzz/FuzzedDataProvider.h>
 8  #include <test/fuzz/util.h>
 9  #include <test/util/str.h>
10  #include <util/strencodings.h>
11  #include <hash.h>
12  
13  #include <cassert>
14  #include <cstdint>
15  #include <vector>
16  
17  uint256 ComputeMerkleRootFromPath(const CBlock& block, uint32_t position, const std::vector<uint256>& merkle_path) {
18      if (position >= block.vtx.size()) {
19          throw std::out_of_range("Position out of range");
20      }
21  
22      uint256 current_hash = block.vtx[position]->GetHash().ToUint256();
23  
24      for (const uint256& sibling : merkle_path) {
25          if (position % 2 == 0) {
26              current_hash = Hash(current_hash, sibling);
27          } else {
28              current_hash = Hash(sibling, current_hash);
29          }
30          position = position / 2;
31      }
32  
33      return current_hash;
34  }
35  
36  FUZZ_TARGET(merkle)
37  {
38      FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
39  
40      const bool with_witness = fuzzed_data_provider.ConsumeBool();
41      std::optional<CBlock> block {ConsumeDeserializable<CBlock>(fuzzed_data_provider, with_witness ? TX_WITH_WITNESS : TX_NO_WITNESS)};
42      if (!block){
43          return;
44      }
45      const size_t num_txs = block->vtx.size();
46      std::vector<uint256> tx_hashes;
47      tx_hashes.reserve(num_txs);
48  
49      for (size_t i = 0; i < num_txs; ++i) {
50          tx_hashes.push_back(block->vtx[i]->GetHash().ToUint256());
51      }
52  
53      // Test ComputeMerkleRoot
54      bool mutated = fuzzed_data_provider.ConsumeBool(); // output param, initial value shouldn't matter
55      const uint256 merkle_root = ComputeMerkleRoot(tx_hashes, fuzzed_data_provider.ConsumeBool() ? &mutated : nullptr);
56  
57      // Basic sanity checks for ComputeMerkleRoot
58      if (tx_hashes.size() == 1) {
59          assert(merkle_root == tx_hashes[0]);
60      }
61  
62  
63      const uint256 block_merkle_root = BlockMerkleRoot(*block, &mutated);
64      if (tx_hashes.size() == 1) {
65          assert(block_merkle_root == tx_hashes[0]);
66      }
67  
68      if (!block->vtx.empty()){
69          const uint256 block_witness_merkle_root = BlockWitnessMerkleRoot(*block);
70          if (tx_hashes.size() == 1) {
71              assert(block_witness_merkle_root == uint256());
72          }
73      }
74  
75      // Test TransactionMerklePath
76      const uint32_t position = fuzzed_data_provider.ConsumeIntegralInRange<uint32_t>(0, num_txs > 0 ? num_txs - 1 : 0);
77      std::vector<uint256> merkle_path = TransactionMerklePath(*block, position);
78  
79      // Check that the root we compute from TransactionMerklePath equals the same merkle_root and block_merkle_root
80      if (tx_hashes.size() > 1) {
81          uint256 merkle_root_from_merkle_path = ComputeMerkleRootFromPath(*block, position, merkle_path);
82          assert(merkle_root_from_merkle_path == merkle_root);
83          assert(merkle_root_from_merkle_path == block_merkle_root);
84      }
85  
86      // Basic sanity checks for TransactionMerklePath
87      assert(merkle_path.size() <= 32); // Maximum depth of a Merkle tree with 2^32 leaves
88      if (num_txs == 1 || num_txs == 0) {
89          assert(merkle_path.empty()); // Single transaction has no path
90      }
91  
92  }