1  // Copyright (c) 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 <index/txospenderindex.h>
  6  
  7  #include <common/args.h>
  8  #include <crypto/siphash.h>
  9  #include <dbwrapper.h>
 10  #include <flatfile.h>
 11  #include <index/base.h>
 12  #include <index/disktxpos.h>
 13  #include <interfaces/chain.h>
 14  #include <logging.h>
 15  #include <node/blockstorage.h>
 16  #include <primitives/block.h>
 17  #include <primitives/transaction.h>
 18  #include <random.h>
 19  #include <serialize.h>
 20  #include <streams.h>
 21  #include <tinyformat.h>
 22  #include <uint256.h>
 23  #include <util/fs.h>
 24  #include <validation.h>
 25  
 26  #include <cstdio>
 27  #include <exception>
 28  #include <ios>
 29  #include <string>
 30  #include <utility>
 31  #include <vector>
 32  
 33  /* The database is used to find the spending transaction of a given utxo.
 34   * For every input of every transaction it stores a key that is a pair(siphash(input outpoint), transaction location on disk) and an empty value.
 35   * To find the spending transaction of an outpoint, we perform a range query on siphash(outpoint), and for each returned key load the transaction
 36   * and return it if it does spend the provided outpoint.
 37   */
 38  
 39  // LevelDB key prefix. We only have one key for now but it will make it easier to add others if needed.
 40  constexpr uint8_t DB_TXOSPENDERINDEX{'s'};
 41  
 42  std::unique_ptr<TxoSpenderIndex> g_txospenderindex;
 43  
 44  struct DBKey {
 45      uint64_t hash;
 46      CDiskTxPos pos;
 47  
 48      explicit DBKey(const uint64_t& hash_in, const CDiskTxPos& pos_in) : hash(hash_in), pos(pos_in) {}
 49  
 50      SERIALIZE_METHODS(DBKey, obj)
 51      {
 52          uint8_t prefix{DB_TXOSPENDERINDEX};
 53          READWRITE(prefix);
 54          if (prefix != DB_TXOSPENDERINDEX) {
 55              throw std::ios_base::failure("Invalid format for spender index DB key");
 56          }
 57          READWRITE(obj.hash);
 58          READWRITE(obj.pos);
 59      }
 60  };
 61  
 62  TxoSpenderIndex::TxoSpenderIndex(std::unique_ptr<interfaces::Chain> chain, size_t n_cache_size, bool f_memory, bool f_wipe)
 63      : BaseIndex(std::move(chain), "txospenderindex"), m_db{std::make_unique<DB>(gArgs.GetDataDirNet() / "indexes" / "txospenderindex" / "db", n_cache_size, f_memory, f_wipe)}
 64  {
 65      if (!m_db->Read("siphash_key", m_siphash_key)) {
 66          FastRandomContext rng(false);
 67          m_siphash_key = {rng.rand64(), rng.rand64()};
 68          m_db->Write("siphash_key", m_siphash_key, /*fSync=*/ true);
 69      }
 70  }
 71  
 72  interfaces::Chain::NotifyOptions TxoSpenderIndex::CustomOptions()
 73  {
 74      interfaces::Chain::NotifyOptions options;
 75      options.disconnect_data = true;
 76      return options;
 77  }
 78  
 79  static uint64_t CreateKeyPrefix(std::pair<uint64_t, uint64_t> siphash_key, const COutPoint& vout)
 80  {
 81      return PresaltedSipHasher(siphash_key.first, siphash_key.second)(vout.hash.ToUint256(), vout.n);
 82  }
 83  
 84  static DBKey CreateKey(std::pair<uint64_t, uint64_t> siphash_key, const COutPoint& vout, const CDiskTxPos& pos)
 85  {
 86      return DBKey(CreateKeyPrefix(siphash_key, vout), pos);
 87  }
 88  
 89  void TxoSpenderIndex::WriteSpenderInfos(const std::vector<std::pair<COutPoint, CDiskTxPos>>& items)
 90  {
 91      CDBBatch batch(*m_db);
 92      for (const auto& [outpoint, pos] : items) {
 93          DBKey key(CreateKey(m_siphash_key, outpoint, pos));
 94          // key is hash(spent outpoint) | disk pos, value is empty
 95          batch.Write(key, "");
 96      }
 97      m_db->WriteBatch(batch);
 98  }
 99  
100  
101  void TxoSpenderIndex::EraseSpenderInfos(const std::vector<std::pair<COutPoint, CDiskTxPos>>& items)
102  {
103      CDBBatch batch(*m_db);
104      for (const auto& [outpoint, pos] : items) {
105          batch.Erase(CreateKey(m_siphash_key, outpoint, pos));
106      }
107      m_db->WriteBatch(batch);
108  }
109  
110  static std::vector<std::pair<COutPoint, CDiskTxPos>> BuildSpenderPositions(const interfaces::BlockInfo& block)
111  {
112      std::vector<std::pair<COutPoint, CDiskTxPos>> items;
113      items.reserve(block.data->vtx.size());
114  
115      CDiskTxPos pos({block.file_number, block.data_pos}, GetSizeOfCompactSize(block.data->vtx.size()));
116      for (const auto& tx : block.data->vtx) {
117          if (!tx->IsCoinBase()) {
118              for (const auto& input : tx->vin) {
119                  items.emplace_back(input.prevout, pos);
120              }
121          }
122          pos.nTxOffset += ::GetSerializeSize(TX_WITH_WITNESS(*tx));
123      }
124  
125      return items;
126  }
127  
128  
129  bool TxoSpenderIndex::CustomAppend(const interfaces::BlockInfo& block)
130  {
131      WriteSpenderInfos(BuildSpenderPositions(block));
132      return true;
133  }
134  
135  bool TxoSpenderIndex::CustomRemove(const interfaces::BlockInfo& block)
136  {
137      EraseSpenderInfos(BuildSpenderPositions(block));
138      return true;
139  }
140  
141  util::Expected<TxoSpender, std::string> TxoSpenderIndex::ReadTransaction(const CDiskTxPos& tx_pos) const
142  {
143      AutoFile file{m_chainstate->m_blockman.OpenBlockFile(tx_pos, /*fReadOnly=*/true)};
144      if (file.IsNull()) {
145          return util::Unexpected("cannot open block");
146      }
147      CBlockHeader header;
148      TxoSpender spender;
149      try {
150          file >> header;
151          file.seek(tx_pos.nTxOffset, SEEK_CUR);
152          file >> TX_WITH_WITNESS(spender.tx);
153          spender.block_hash = header.GetHash();
154          return spender;
155      } catch (const std::exception& e) {
156          return util::Unexpected(e.what());
157      }
158  }
159  
160  util::Expected<std::optional<TxoSpender>, std::string> TxoSpenderIndex::FindSpender(const COutPoint& txo) const
161  {
162      const uint64_t prefix{CreateKeyPrefix(m_siphash_key, txo)};
163      std::unique_ptr<CDBIterator> it(m_db->NewIterator());
164      DBKey key(prefix, CDiskTxPos());
165  
166      // find all keys that start with the outpoint hash, load the transaction at the location specified in the key
167      // and return it if it does spend the provided outpoint
168      for (it->Seek(std::pair{DB_TXOSPENDERINDEX, prefix}); it->Valid() && it->GetKey(key) && key.hash == prefix; it->Next()) {
169          if (const auto spender{ReadTransaction(key.pos)}) {
170              for (const auto& input : spender->tx->vin) {
171                  if (input.prevout == txo) {
172                      return std::optional{*spender};
173                  }
174              }
175          } else {
176              LogError("Deserialize or I/O error - %s", spender.error());
177              return util::Unexpected{strprintf("IO error finding spending tx for outpoint %s:%d.", txo.hash.GetHex(), txo.n)};
178          }
179      }
180      return util::Expected<std::optional<TxoSpender>, std::string>(std::nullopt);
181  }
182  
183  BaseIndex::DB& TxoSpenderIndex::GetDB() const { return *m_db; }