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sipasipa
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Precompute sighashes
Original version by Nicolas Dorier. Precomputing version by Pieter Wuille.
1 parent 2c2d471 commit d2c5d04

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8 files changed

+78
-38
lines changed

8 files changed

+78
-38
lines changed

‎src/main.cpp‎

Lines changed: 13 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1492,12 +1492,13 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
14921492

14931493
// Check against previous transactions
14941494
// This is done last to help prevent CPU exhaustion denial-of-service attacks.
1495-
if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true)) {
1495+
CachedHashes cachedHashes(tx);
1496+
if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true, cachedHashes)) {
14961497
// SCRIPT_VERIFY_CLEANSTACK requires SCRIPT_VERIFY_WITNESS, so we
14971498
// need to turn both off, and compare against just turning off CLEANSTACK
14981499
// to see if the failure is specifically due to witness validation.
1499-
if (CheckInputs(tx, state, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true) &&
1500-
!CheckInputs(tx, state, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true)) {
1500+
if (CheckInputs(tx, state, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, cachedHashes) &&
1501+
!CheckInputs(tx, state, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, cachedHashes)) {
15011502
// Only the witness is wrong, so the transaction itself may be fine.
15021503
state.SetCorruptionPossible();
15031504
}
@@ -1513,7 +1514,7 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
15131514
// There is a similar check in CreateNewBlock() to prevent creating
15141515
// invalid blocks, however allowing such transactions into the mempool
15151516
// can be exploited as a DoS attack.
1516-
if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true))
1517+
if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true, cachedHashes))
15171518
{
15181519
return error("%s: BUG! PLEASE REPORT THIS! ConnectInputs failed against MANDATORY but not STANDARD flags %s, %s",
15191520
__func__, hash.ToString(), FormatStateMessage(state));
@@ -1910,7 +1911,7 @@ void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight)
19101911
bool CScriptCheck::operator()() {
19111912
const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
19121913
const CScriptWitness *witness = (nIn < ptxTo->wit.vtxinwit.size()) ? &ptxTo->wit.vtxinwit[nIn].scriptWitness : NULL;
1913-
if (!VerifyScript(scriptSig, scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, amount, cacheStore), &error)) {
1914+
if (!VerifyScript(scriptSig, scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, amount, cacheStore, *cachedHashes), &error)) {
19141915
return false;
19151916
}
19161917
return true;
@@ -1969,7 +1970,7 @@ bool CheckTxInputs(const CTransaction& tx, CValidationState& state, const CCoins
19691970
}
19701971
}// namespace Consensus
19711972

1972-
bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, std::vector<CScriptCheck> *pvChecks)
1973+
bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, CachedHashes& cachedHashes, std::vector<CScriptCheck> *pvChecks)
19731974
{
19741975
if (!tx.IsCoinBase())
19751976
{
@@ -1996,7 +1997,7 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
19961997
assert(coins);
19971998

19981999
// Verify signature
1999-
CScriptCheck check(*coins, tx, i, flags, cacheStore);
2000+
CScriptCheck check(*coins, tx, i, flags, cacheStore, &cachedHashes);
20002001
if (pvChecks) {
20012002
pvChecks->push_back(CScriptCheck());
20022003
check.swap(pvChecks->back());
@@ -2009,7 +2010,7 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi
20092010
// avoid splitting the network between upgraded and
20102011
// non-upgraded nodes.
20112012
CScriptCheck check2(*coins, tx, i,
2012-
flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore);
2013+
flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore, &cachedHashes);
20132014
if (check2())
20142015
return state.Invalid(false, REJECT_NONSTANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));
20152016
}
@@ -2405,6 +2406,8 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
24052406
std::vector<std::pair<uint256, CDiskTxPos> > vPos;
24062407
vPos.reserve(block.vtx.size());
24072408
blockundo.vtxundo.reserve(block.vtx.size() - 1);
2409+
std::vector<CachedHashes> cachedHashes;
2410+
cachedHashes.reserve(block.vtx.size()); // Required so that pointers to individual CachedHashes don't get invalidated
24082411
for (unsigned int i = 0; i < block.vtx.size(); i++)
24092412
{
24102413
const CTransaction &tx = block.vtx[i];
@@ -2451,13 +2454,14 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
24512454
return state.DoS(100, error("ConnectBlock(): too many sigops"),
24522455
REJECT_INVALID, "bad-blk-sigops");
24532456

2457+
cachedHashes.emplace_back(tx);
24542458
if (!tx.IsCoinBase())
24552459
{
24562460
nFees += view.GetValueIn(tx)-tx.GetValueOut();
24572461

24582462
std::vector<CScriptCheck> vChecks;
24592463
bool fCacheResults = fJustCheck; /* Don't cache results if we're actually connecting blocks (still consult the cache, though) */
2460-
if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, nScriptCheckThreads ? &vChecks : NULL))
2464+
if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, cachedHashes[i], nScriptCheckThreads ? &vChecks : NULL))
24612465
return error("ConnectBlock(): CheckInputs on %s failed with %s",
24622466
tx.GetHash().ToString(), FormatStateMessage(state));
24632467
control.Add(vChecks);

‎src/main.h‎

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -38,6 +38,7 @@ class CScriptCheck;
3838
class CTxMemPool;
3939
class CValidationInterface;
4040
class CValidationState;
41+
class CachedHashes;
4142

4243
struct CNodeStateStats;
4344
struct LockPoints;
@@ -347,7 +348,7 @@ int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& i
347348
* instead of being performed inline.
348349
*/
349350
bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &view, bool fScriptChecks,
350-
unsigned int flags, bool cacheStore, std::vector<CScriptCheck> *pvChecks = NULL);
351+
unsigned int flags, bool cacheStore, CachedHashes& cachedHashes, std::vector<CScriptCheck> *pvChecks = NULL);
351352

352353
/** Apply the effects of this transaction on the UTXO set represented by view */
353354
void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight);
@@ -421,12 +422,13 @@ class CScriptCheck
421422
unsigned int nFlags;
422423
bool cacheStore;
423424
ScriptError error;
425+
CachedHashes *cachedHashes;
424426

425427
public:
426428
CScriptCheck(): amount(0), ptxTo(0), nIn(0), nFlags(0), cacheStore(false), error(SCRIPT_ERR_UNKNOWN_ERROR) {}
427-
CScriptCheck(const CCoins& txFromIn, const CTransaction& txToIn, unsigned int nInIn, unsigned int nFlagsIn, bool cacheIn) :
429+
CScriptCheck(const CCoins& txFromIn, const CTransaction& txToIn, unsigned int nInIn, unsigned int nFlagsIn, bool cacheIn, CachedHashes* cachedHashesIn) :
428430
scriptPubKey(txFromIn.vout[txToIn.vin[nInIn].prevout.n].scriptPubKey), amount(txFromIn.vout[txToIn.vin[nInIn].prevout.n].nValue),
429-
ptxTo(&txToIn), nIn(nInIn), nFlags(nFlagsIn), cacheStore(cacheIn), error(SCRIPT_ERR_UNKNOWN_ERROR) { }
431+
ptxTo(&txToIn), nIn(nInIn), nFlags(nFlagsIn), cacheStore(cacheIn), error(SCRIPT_ERR_UNKNOWN_ERROR), cachedHashes(cachedHashesIn) { }
430432

431433
bool operator()();
432434

@@ -438,6 +440,7 @@ class CScriptCheck
438440
std::swap(nFlags, check.nFlags);
439441
std::swap(cacheStore, check.cacheStore);
440442
std::swap(error, check.error);
443+
std::swap(cachedHashes, check.cachedHashes);
441444
}
442445

443446
ScriptError GetScriptError() const { return error; }

‎src/script/bitcoinconsensus.cpp‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -84,8 +84,8 @@ static int verify_script(const unsigned char *scriptPubKey, unsigned int scriptP
8484

8585
// Regardless of the verification result, the tx did not error.
8686
set_error(err, bitcoinconsensus_ERR_OK);
87-
88-
return VerifyScript(tx.vin[nIn].scriptSig, CScript(scriptPubKey, scriptPubKey + scriptPubKeyLen), nIn < tx.wit.vtxinwit.size() ? &tx.wit.vtxinwit[nIn].scriptWitness : NULL, flags, TransactionSignatureChecker(&tx, nIn, amount), NULL);
87+
CachedHashes cachedHashes(tx);
88+
return VerifyScript(tx.vin[nIn].scriptSig, CScript(scriptPubKey, scriptPubKey + scriptPubKeyLen), nIn < tx.wit.vtxinwit.size() ? &tx.wit.vtxinwit[nIn].scriptWitness : NULL, flags, TransactionSignatureChecker(&tx, nIn, amount, cachedHashes), NULL);
8989
} catch (const std::exception&) {
9090
return set_error(err, bitcoinconsensus_ERR_TX_DESERIALIZE); // Error deserializing
9191
}

‎src/script/interpreter.cpp‎

Lines changed: 37 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -1108,37 +1108,57 @@ class CTransactionSignatureSerializer {
11081108
}
11091109
};
11101110

1111+
uint256 GetPrevoutHash(const CTransaction& txTo) {
1112+
CHashWriter ss(SER_GETHASH, 0);
1113+
for (unsigned int n = 0; n < txTo.vin.size(); n++) {
1114+
ss << txTo.vin[n].prevout;
1115+
}
1116+
return ss.GetHash();
1117+
}
1118+
1119+
uint256 GetSequenceHash(const CTransaction& txTo) {
1120+
CHashWriter ss(SER_GETHASH, 0);
1121+
for (unsigned int n = 0; n < txTo.vin.size(); n++) {
1122+
ss << txTo.vin[n].nSequence;
1123+
}
1124+
return ss.GetHash();
1125+
}
1126+
1127+
uint256 GetOutputsHash(const CTransaction& txTo) {
1128+
CHashWriter ss(SER_GETHASH, 0);
1129+
for (unsigned int n = 0; n < txTo.vout.size(); n++) {
1130+
ss << txTo.vout[n];
1131+
}
1132+
return ss.GetHash();
1133+
}
1134+
11111135
} // anon namespace
11121136

1113-
uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion)
1137+
CachedHashes::CachedHashes(const CTransaction& txTo)
1138+
{
1139+
hashPrevouts = GetPrevoutHash(txTo);
1140+
hashSequence = GetSequenceHash(txTo);
1141+
hashOutputs = GetOutputsHash(txTo);
1142+
}
1143+
1144+
uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const CachedHashes* cache)
11141145
{
11151146
if (sigversion == SIGVERSION_WITNESS_V0) {
11161147
uint256 hashPrevouts;
11171148
uint256 hashSequence;
11181149
uint256 hashOutputs;
11191150

11201151
if (!(nHashType & SIGHASH_ANYONECANPAY)) {
1121-
CHashWriter ss(SER_GETHASH, 0);
1122-
for (unsigned int n = 0; n < txTo.vin.size(); n++) {
1123-
ss << txTo.vin[n].prevout;
1124-
}
1125-
hashPrevouts = ss.GetHash(); // TODO: cache this value for all signatures in a transaction
1152+
hashPrevouts = cache ? cache->hashPrevouts : GetPrevoutHash(txTo);
11261153
}
11271154

11281155
if (!(nHashType & SIGHASH_ANYONECANPAY) && (nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
1129-
CHashWriter ss(SER_GETHASH, 0);
1130-
for (unsigned int n = 0; n < txTo.vin.size(); n++) {
1131-
ss << txTo.vin[n].nSequence;
1132-
}
1133-
hashSequence = ss.GetHash(); // TODO: cache this value for all signatures in a transaction
1156+
hashSequence = cache ? cache->hashSequence : GetSequenceHash(txTo);
11341157
}
11351158

1159+
11361160
if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
1137-
CHashWriter ss(SER_GETHASH, 0);
1138-
for (unsigned int n = 0; n < txTo.vout.size(); n++) {
1139-
ss << txTo.vout[n];
1140-
}
1141-
hashOutputs = ss.GetHash(); // TODO: cache this value for all signatures in a transaction
1161+
hashOutputs = cache ? cache->hashOutputs : GetOutputsHash(txTo);
11421162
} else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
11431163
CHashWriter ss(SER_GETHASH, 0);
11441164
ss << txTo.vout[nIn];
@@ -1209,7 +1229,7 @@ bool TransactionSignatureChecker::CheckSig(const vector<unsigned char>& vchSigIn
12091229
int nHashType = vchSig.back();
12101230
vchSig.pop_back();
12111231

1212-
uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion);
1232+
uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion, this->cachedHashes);
12131233

12141234
if (!VerifySignature(vchSig, pubkey, sighash))
12151235
return false;

‎src/script/interpreter.h‎

Lines changed: 11 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -98,13 +98,20 @@ enum
9898

9999
bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned int flags, ScriptError* serror);
100100

101+
struct CachedHashes
102+
{
103+
uint256 hashPrevouts, hashSequence, hashOutputs;
104+
105+
CachedHashes(const CTransaction& tx);
106+
};
107+
101108
enum SigVersion
102109
{
103110
SIGVERSION_BASE = 0,
104111
SIGVERSION_WITNESS_V0 = 1,
105112
};
106113

107-
uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion);
114+
uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const CachedHashes* cache = NULL);
108115

109116
class BaseSignatureChecker
110117
{
@@ -133,12 +140,14 @@ class TransactionSignatureChecker : public BaseSignatureChecker
133140
const CTransaction* txTo;
134141
unsigned int nIn;
135142
const CAmount amount;
143+
const CachedHashes* cachedHashes;
136144

137145
protected:
138146
virtual bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;
139147

140148
public:
141-
TransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn) : txTo(txToIn), nIn(nInIn), amount(amountIn) {}
149+
TransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn) : txTo(txToIn), nIn(nInIn), amount(amountIn), cachedHashes(NULL) {}
150+
TransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, const CachedHashes& cachedHashesIn) : txTo(txToIn), nIn(nInIn), amount(amountIn), cachedHashes(&cachedHashesIn) {}
142151
bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const;
143152
bool CheckLockTime(const CScriptNum& nLockTime) const;
144153
bool CheckSequence(const CScriptNum& nSequence) const;

‎src/script/sigcache.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -22,7 +22,7 @@ class CachingTransactionSignatureChecker : public TransactionSignatureChecker
2222
bool store;
2323

2424
public:
25-
CachingTransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amount, bool storeIn) : TransactionSignatureChecker(txToIn, nInIn, amount), store(storeIn) {}
25+
CachingTransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amount, bool storeIn, CachedHashes& cachedHashesIn) : TransactionSignatureChecker(txToIn, nInIn, amount, cachedHashesIn), store(storeIn) {}
2626

2727
bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;
2828
};

‎src/test/script_P2SH_tests.cpp‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -107,18 +107,20 @@ BOOST_AUTO_TEST_CASE(sign)
107107
}
108108
// All of the above should be OK, and the txTos have valid signatures
109109
// Check to make sure signature verification fails if we use the wrong ScriptSig:
110-
for (int i = 0; i < 8; i++)
110+
for (int i = 0; i < 8; i++) {
111+
CachedHashes cachedHashes(txTo[i]);
111112
for (int j = 0; j < 8; j++)
112113
{
113114
CScript sigSave = txTo[i].vin[0].scriptSig;
114115
txTo[i].vin[0].scriptSig = txTo[j].vin[0].scriptSig;
115-
bool sigOK = CScriptCheck(CCoins(txFrom, 0), txTo[i], 0, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC, false)();
116+
bool sigOK = CScriptCheck(CCoins(txFrom, 0), txTo[i], 0, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC, false, &cachedHashes)();
116117
if (i == j)
117118
BOOST_CHECK_MESSAGE(sigOK, strprintf("VerifySignature %d %d", i, j));
118119
else
119120
BOOST_CHECK_MESSAGE(!sigOK, strprintf("VerifySignature %d %d", i, j));
120121
txTo[i].vin[0].scriptSig = sigSave;
121122
}
123+
}
122124
}
123125

124126
BOOST_AUTO_TEST_CASE(norecurse)

‎src/test/transaction_tests.cpp‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -153,6 +153,7 @@ BOOST_AUTO_TEST_CASE(tx_valid)
153153
BOOST_CHECK_MESSAGE(CheckTransaction(tx, state), strTest);
154154
BOOST_CHECK(state.IsValid());
155155

156+
CachedHashes cachedHashes(tx);
156157
for (unsigned int i = 0; i < tx.vin.size(); i++)
157158
{
158159
if (!mapprevOutScriptPubKeys.count(tx.vin[i].prevout))
@@ -168,7 +169,7 @@ BOOST_AUTO_TEST_CASE(tx_valid)
168169
unsigned int verify_flags = ParseScriptFlags(test[2].get_str());
169170
const CScriptWitness *witness = (i < tx.wit.vtxinwit.size()) ? &tx.wit.vtxinwit[i].scriptWitness : NULL;
170171
BOOST_CHECK_MESSAGE(VerifyScript(tx.vin[i].scriptSig, mapprevOutScriptPubKeys[tx.vin[i].prevout],
171-
witness, verify_flags, TransactionSignatureChecker(&tx, i, amount), &err),
172+
witness, verify_flags, TransactionSignatureChecker(&tx, i, amount, cachedHashes), &err),
172173
strTest);
173174
BOOST_CHECK_MESSAGE(err == SCRIPT_ERR_OK, ScriptErrorString(err));
174175
}
@@ -237,6 +238,7 @@ BOOST_AUTO_TEST_CASE(tx_invalid)
237238
CValidationState state;
238239
fValid = CheckTransaction(tx, state) && state.IsValid();
239240

241+
CachedHashes cachedHashes(tx);
240242
for (unsigned int i = 0; i < tx.vin.size() && fValid; i++)
241243
{
242244
if (!mapprevOutScriptPubKeys.count(tx.vin[i].prevout))
@@ -252,7 +254,7 @@ BOOST_AUTO_TEST_CASE(tx_invalid)
252254
}
253255
const CScriptWitness *witness = (i < tx.wit.vtxinwit.size()) ? &tx.wit.vtxinwit[i].scriptWitness : NULL;
254256
fValid = VerifyScript(tx.vin[i].scriptSig, mapprevOutScriptPubKeys[tx.vin[i].prevout],
255-
witness, verify_flags, TransactionSignatureChecker(&tx, i, amount), &err);
257+
witness, verify_flags, TransactionSignatureChecker(&tx, i, amount, cachedHashes), &err);
256258
}
257259
BOOST_CHECK_MESSAGE(!fValid, strTest);
258260
BOOST_CHECK_MESSAGE(err != SCRIPT_ERR_OK, ScriptErrorString(err));

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