1  // Copyright (c) 2017-2021 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/tx_verify.h>
  6  
  7  #include <chain.h>
  8  #include <coins.h>
  9  #include <consensus/amount.h>
 10  #include <consensus/consensus.h>
 11  #include <consensus/validation.h>
 12  #include <primitives/transaction.h>
 13  #include <script/interpreter.h>
 14  #include <util/check.h>
 15  #include <util/moneystr.h>
 16  
 17  bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
 18  {
 19      if (tx.nLockTime == 0)
 20          return true;
 21      if ((int64_t)tx.nLockTime < ((int64_t)tx.nLockTime < LOCKTIME_THRESHOLD ? (int64_t)nBlockHeight : nBlockTime))
 22          return true;
 23  
 24      // Even if tx.nLockTime isn't satisfied by nBlockHeight/nBlockTime, a
 25      // transaction is still considered final if all inputs' nSequence ==
 26      // SEQUENCE_FINAL (0xffffffff), in which case nLockTime is ignored.
 27      //
 28      // Because of this behavior OP_CHECKLOCKTIMEVERIFY/CheckLockTime() will
 29      // also check that the spending input's nSequence != SEQUENCE_FINAL,
 30      // ensuring that an unsatisfied nLockTime value will actually cause
 31      // IsFinalTx() to return false here:
 32      for (const auto& txin : tx.vin) {
 33          if (!(txin.nSequence == CTxIn::SEQUENCE_FINAL))
 34              return false;
 35      }
 36      return true;
 37  }
 38  
 39  std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)
 40  {
 41      assert(prevHeights.size() == tx.vin.size());
 42  
 43      // Will be set to the equivalent height- and time-based nLockTime
 44      // values that would be necessary to satisfy all relative lock-
 45      // time constraints given our view of block chain history.
 46      // The semantics of nLockTime are the last invalid height/time, so
 47      // use -1 to have the effect of any height or time being valid.
 48      int nMinHeight = -1;
 49      int64_t nMinTime = -1;
 50  
 51      bool fEnforceBIP68 = tx.version >= 2 && flags & LOCKTIME_VERIFY_SEQUENCE;
 52  
 53      // Do not enforce sequence numbers as a relative lock time
 54      // unless we have been instructed to
 55      if (!fEnforceBIP68) {
 56          return std::make_pair(nMinHeight, nMinTime);
 57      }
 58  
 59      for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
 60          const CTxIn& txin = tx.vin[txinIndex];
 61  
 62          // Sequence numbers with the most significant bit set are not
 63          // treated as relative lock-times, nor are they given any
 64          // consensus-enforced meaning at this point.
 65          if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {
 66              // The height of this input is not relevant for sequence locks
 67              prevHeights[txinIndex] = 0;
 68              continue;
 69          }
 70  
 71          int nCoinHeight = prevHeights[txinIndex];
 72  
 73          if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) {
 74              const int64_t nCoinTime{Assert(block.GetAncestor(std::max(nCoinHeight - 1, 0)))->GetMedianTimePast()};
 75              // NOTE: Subtract 1 to maintain nLockTime semantics
 76              // BIP 68 relative lock times have the semantics of calculating
 77              // the first block or time at which the transaction would be
 78              // valid. When calculating the effective block time or height
 79              // for the entire transaction, we switch to using the
 80              // semantics of nLockTime which is the last invalid block
 81              // time or height.  Thus we subtract 1 from the calculated
 82              // time or height.
 83  
 84              // Time-based relative lock-times are measured from the
 85              // smallest allowed timestamp of the block containing the
 86              // txout being spent, which is the median time past of the
 87              // block prior.
 88              nMinTime = std::max(nMinTime, nCoinTime + (int64_t)((txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) << CTxIn::SEQUENCE_LOCKTIME_GRANULARITY) - 1);
 89          } else {
 90              nMinHeight = std::max(nMinHeight, nCoinHeight + (int)(txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) - 1);
 91          }
 92      }
 93  
 94      return std::make_pair(nMinHeight, nMinTime);
 95  }
 96  
 97  bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair)
 98  {
 99      assert(block.pprev);
100      int64_t nBlockTime = block.pprev->GetMedianTimePast();
101      if (lockPair.first >= block.nHeight || lockPair.second >= nBlockTime)
102          return false;
103  
104      return true;
105  }
106  
107  bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)
108  {
109      return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));
110  }
111  
112  unsigned int GetLegacySigOpCount(const CTransaction& tx)
113  {
114      unsigned int nSigOps = 0;
115      for (const auto& txin : tx.vin)
116      {
117          nSigOps += txin.scriptSig.GetSigOpCount(false);
118      }
119      for (const auto& txout : tx.vout)
120      {
121          nSigOps += txout.scriptPubKey.GetSigOpCount(false);
122      }
123      return nSigOps;
124  }
125  
126  unsigned int GetP2SHSigOpCount(const CTransaction& tx, const CCoinsViewCache& inputs)
127  {
128      if (tx.IsCoinBase())
129          return 0;
130  
131      unsigned int nSigOps = 0;
132      for (unsigned int i = 0; i < tx.vin.size(); i++)
133      {
134          const Coin& coin = inputs.AccessCoin(tx.vin[i].prevout);
135          assert(!coin.IsSpent());
136          const CTxOut &prevout = coin.out;
137          if (prevout.scriptPubKey.IsPayToScriptHash())
138              nSigOps += prevout.scriptPubKey.GetSigOpCount(tx.vin[i].scriptSig);
139      }
140      return nSigOps;
141  }
142  
143  int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& inputs, uint32_t flags)
144  {
145      int64_t nSigOps = GetLegacySigOpCount(tx) * WITNESS_SCALE_FACTOR;
146  
147      if (tx.IsCoinBase())
148          return nSigOps;
149  
150      if (flags & SCRIPT_VERIFY_P2SH) {
151          nSigOps += GetP2SHSigOpCount(tx, inputs) * WITNESS_SCALE_FACTOR;
152      }
153  
154      for (unsigned int i = 0; i < tx.vin.size(); i++)
155      {
156          const Coin& coin = inputs.AccessCoin(tx.vin[i].prevout);
157          assert(!coin.IsSpent());
158          const CTxOut &prevout = coin.out;
159          nSigOps += CountWitnessSigOps(tx.vin[i].scriptSig, prevout.scriptPubKey, &tx.vin[i].scriptWitness, flags);
160      }
161      return nSigOps;
162  }
163  
164  bool Consensus::CheckTxInputs(const CTransaction& tx, TxValidationState& state, const CCoinsViewCache& inputs, int nSpendHeight, CAmount& txfee)
165  {
166      // are the actual inputs available?
167      if (!inputs.HaveInputs(tx)) {
168          return state.Invalid(TxValidationResult::TX_MISSING_INPUTS, "bad-txns-inputs-missingorspent",
169                           strprintf("%s: inputs missing/spent", __func__));
170      }
171  
172      CAmount nValueIn = 0;
173      for (unsigned int i = 0; i < tx.vin.size(); ++i) {
174          const COutPoint &prevout = tx.vin[i].prevout;
175          const Coin& coin = inputs.AccessCoin(prevout);
176          assert(!coin.IsSpent());
177  
178          // If prev is coinbase, check that it's matured
179          if (coin.IsCoinBase() && nSpendHeight - coin.nHeight < COINBASE_MATURITY) {
180              return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND, "bad-txns-premature-spend-of-coinbase",
181                  strprintf("tried to spend coinbase at depth %d", nSpendHeight - coin.nHeight));
182          }
183  
184          // Check for negative or overflow input values
185          nValueIn += coin.out.nValue;
186          if (!MoneyRange(coin.out.nValue) || !MoneyRange(nValueIn)) {
187              return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-inputvalues-outofrange");
188          }
189      }
190  
191      const CAmount value_out = tx.GetValueOut();
192      if (nValueIn < value_out) {
193          return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-in-belowout",
194              strprintf("value in (%s) < value out (%s)", FormatMoney(nValueIn), FormatMoney(value_out)));
195      }
196  
197      // Tally transaction fees
198      const CAmount txfee_aux = nValueIn - value_out;
199      if (!MoneyRange(txfee_aux)) {
200          return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-fee-outofrange");
201      }
202  
203      txfee = txfee_aux;
204      return true;
205  }