1 // Copyright (c) 2017-2020 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 <consensus/consensus.h>
8 #include <primitives/transaction.h>
9 #include <script/interpreter.h>
10 #include <consensus/validation.h>
11
12 // TODO remove the following dependencies
13 #include <chain.h>
14 #include <coins.h>
15 #include <util/moneystr.h>
16
IsFinalTx(const CTransaction & tx,int nBlockHeight,int64_t nBlockTime)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
CalculateSequenceLocks(const CTransaction & tx,int flags,std::vector<int> & prevHeights,const CBlockIndex & block)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 // tx.nVersion is signed integer so requires cast to unsigned otherwise
52 // we would be doing a signed comparison and half the range of nVersion
53 // wouldn't support BIP 68.
54 bool fEnforceBIP68 = static_cast<uint32_t>(tx.nVersion) >= 2
55 && flags & LOCKTIME_VERIFY_SEQUENCE;
56
57 // Do not enforce sequence numbers as a relative lock time
58 // unless we have been instructed to
59 if (!fEnforceBIP68) {
60 return std::make_pair(nMinHeight, nMinTime);
61 }
62
63 for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
64 const CTxIn& txin = tx.vin[txinIndex];
65
66 // Sequence numbers with the most significant bit set are not
67 // treated as relative lock-times, nor are they given any
68 // consensus-enforced meaning at this point.
69 if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {
70 // The height of this input is not relevant for sequence locks
71 prevHeights[txinIndex] = 0;
72 continue;
73 }
74
75 int nCoinHeight = prevHeights[txinIndex];
76
77 if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) {
78 int64_t nCoinTime = block.GetAncestor(std::max(nCoinHeight-1, 0))->GetMedianTimePast();
79 // NOTE: Subtract 1 to maintain nLockTime semantics
80 // BIP 68 relative lock times have the semantics of calculating
81 // the first block or time at which the transaction would be
82 // valid. When calculating the effective block time or height
83 // for the entire transaction, we switch to using the
84 // semantics of nLockTime which is the last invalid block
85 // time or height. Thus we subtract 1 from the calculated
86 // time or height.
87
88 // Time-based relative lock-times are measured from the
89 // smallest allowed timestamp of the block containing the
90 // txout being spent, which is the median time past of the
91 // block prior.
92 nMinTime = std::max(nMinTime, nCoinTime + (int64_t)((txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) << CTxIn::SEQUENCE_LOCKTIME_GRANULARITY) - 1);
93 } else {
94 nMinHeight = std::max(nMinHeight, nCoinHeight + (int)(txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) - 1);
95 }
96 }
97
98 return std::make_pair(nMinHeight, nMinTime);
99 }
100
EvaluateSequenceLocks(const CBlockIndex & block,std::pair<int,int64_t> lockPair)101 bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair)
102 {
103 assert(block.pprev);
104 int64_t nBlockTime = block.pprev->GetMedianTimePast();
105 if (lockPair.first >= block.nHeight || lockPair.second >= nBlockTime)
106 return false;
107
108 return true;
109 }
110
SequenceLocks(const CTransaction & tx,int flags,std::vector<int> & prevHeights,const CBlockIndex & block)111 bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>& prevHeights, const CBlockIndex& block)
112 {
113 return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));
114 }
115
GetLegacySigOpCount(const CTransaction & tx)116 unsigned int GetLegacySigOpCount(const CTransaction& tx)
117 {
118 unsigned int nSigOps = 0;
119 for (const auto& txin : tx.vin)
120 {
121 nSigOps += txin.scriptSig.GetSigOpCount(false);
122 }
123 for (const auto& txout : tx.vout)
124 {
125 nSigOps += txout.scriptPubKey.GetSigOpCount(false);
126 }
127 return nSigOps;
128 }
129
GetP2SHSigOpCount(const CTransaction & tx,const CCoinsViewCache & inputs)130 unsigned int GetP2SHSigOpCount(const CTransaction& tx, const CCoinsViewCache& inputs)
131 {
132 if (tx.IsCoinBase())
133 return 0;
134
135 unsigned int nSigOps = 0;
136 for (unsigned int i = 0; i < tx.vin.size(); i++)
137 {
138 const Coin& coin = inputs.AccessCoin(tx.vin[i].prevout);
139 assert(!coin.IsSpent());
140 const CTxOut &prevout = coin.out;
141 if (prevout.scriptPubKey.IsPayToScriptHash())
142 nSigOps += prevout.scriptPubKey.GetSigOpCount(tx.vin[i].scriptSig);
143 }
144 return nSigOps;
145 }
146
GetTransactionSigOpCost(const CTransaction & tx,const CCoinsViewCache & inputs,int flags)147 int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& inputs, int flags)
148 {
149 int64_t nSigOps = GetLegacySigOpCount(tx) * WITNESS_SCALE_FACTOR;
150
151 if (tx.IsCoinBase())
152 return nSigOps;
153
154 if (flags & SCRIPT_VERIFY_P2SH) {
155 nSigOps += GetP2SHSigOpCount(tx, inputs) * WITNESS_SCALE_FACTOR;
156 }
157
158 for (unsigned int i = 0; i < tx.vin.size(); i++)
159 {
160 const Coin& coin = inputs.AccessCoin(tx.vin[i].prevout);
161 assert(!coin.IsSpent());
162 const CTxOut &prevout = coin.out;
163 nSigOps += CountWitnessSigOps(tx.vin[i].scriptSig, prevout.scriptPubKey, &tx.vin[i].scriptWitness, flags);
164 }
165 return nSigOps;
166 }
167
CheckTxInputs(const CTransaction & tx,TxValidationState & state,const CCoinsViewCache & inputs,int nSpendHeight,CAmount & txfee)168 bool Consensus::CheckTxInputs(const CTransaction& tx, TxValidationState& state, const CCoinsViewCache& inputs, int nSpendHeight, CAmount& txfee)
169 {
170 // are the actual inputs available?
171 if (!inputs.HaveInputs(tx)) {
172 return state.Invalid(TxValidationResult::TX_MISSING_INPUTS, "bad-txns-inputs-missingorspent",
173 strprintf("%s: inputs missing/spent", __func__));
174 }
175
176 CAmount nValueIn = 0;
177 for (unsigned int i = 0; i < tx.vin.size(); ++i) {
178 const COutPoint &prevout = tx.vin[i].prevout;
179 const Coin& coin = inputs.AccessCoin(prevout);
180 assert(!coin.IsSpent());
181
182 // If prev is coinbase, check that it's matured
183 if (coin.IsCoinBase() && nSpendHeight - coin.nHeight < COINBASE_MATURITY) {
184 return state.Invalid(TxValidationResult::TX_PREMATURE_SPEND, "bad-txns-premature-spend-of-coinbase",
185 strprintf("tried to spend coinbase at depth %d", nSpendHeight - coin.nHeight));
186 }
187
188 // Check for negative or overflow input values
189 nValueIn += coin.out.nValue;
190 if (!MoneyRange(coin.out.nValue) || !MoneyRange(nValueIn)) {
191 return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-inputvalues-outofrange");
192 }
193 }
194
195 const CAmount value_out = tx.GetValueOut();
196 if (nValueIn < value_out) {
197 return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-in-belowout",
198 strprintf("value in (%s) < value out (%s)", FormatMoney(nValueIn), FormatMoney(value_out)));
199 }
200
201 // Tally transaction fees
202 const CAmount txfee_aux = nValueIn - value_out;
203 if (!MoneyRange(txfee_aux)) {
204 return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-fee-outofrange");
205 }
206
207 txfee = txfee_aux;
208 return true;
209 }
210