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Relax IsStandard rules for pay-to-script-hash transactions

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Relax the AreInputsStandard() tests for P2SH transactions --
allow any Script in a P2SH transaction to be relayed/mined,
as long as it has 15 or fewer signature operations.

Rationale: https://gist.github.com/gavinandresen/88be40c141bc67acb247

I don't have an easy way to test this, but the code changes are
straightforward and I've updated the AreInputsStandard unit tests.
pull/4365/head
Gavin Andresen 11 years ago
parent 36db6633c3
commit 7f3b4e9569
No known key found for this signature in database
GPG Key ID: 7588242FBE38D3A8
3 changed files with 97 additions and 66 deletions
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37
src/main.cpp
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@ -582,15 +582,13 @@ bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
} }
// //
// Check transaction inputs, and make sure any // Check transaction inputs to mitigate two
// pay-to-script-hash transactions are evaluating IsStandard scripts // potential denial-of-service attacks:
// //
// Why bother? To avoid denial-of-service attacks; an attacker // 1. scriptSigs with extra data stuffed into them,
// can submit a standard HASH... OP_EQUAL transaction, // not consumed by scriptPubKey (or P2SH script)
// which will get accepted into blocks. The redemption // 2. P2SH scripts with a crazy number of expensive
// script can be anything; an attacker could use a very // CHECKSIG/CHECKMULTISIG operations
// expensive-to-check-upon-redemption script like:
// DUP CHECKSIG DROP ... repeated 100 times... OP_1
// //
bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs) bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
{ {
@ -614,8 +612,9 @@ bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
// Transactions with extra stuff in their scriptSigs are // Transactions with extra stuff in their scriptSigs are
// non-standard. Note that this EvalScript() call will // non-standard. Note that this EvalScript() call will
// be quick, because if there are any operations // be quick, because if there are any operations
// beside "push data" in the scriptSig the // beside "push data" in the scriptSig
// IsStandard() call returns false // IsStandard() will have already returned false
// and this method isn't called.
vector<vector<unsigned char> > stack; vector<vector<unsigned char> > stack;
if (!EvalScript(stack, tx.vin[i].scriptSig, tx, i, false, 0)) if (!EvalScript(stack, tx.vin[i].scriptSig, tx, i, false, 0))
return false; return false;
@ -627,17 +626,21 @@ bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
CScript subscript(stack.back().begin(), stack.back().end()); CScript subscript(stack.back().begin(), stack.back().end());
vector<vector<unsigned char> > vSolutions2; vector<vector<unsigned char> > vSolutions2;
txnouttype whichType2; txnouttype whichType2;
if (!Solver(subscript, whichType2, vSolutions2)) if (Solver(subscript, whichType2, vSolutions2))
return false; {
if (whichType2 == TX_SCRIPTHASH) int tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
return false;
int tmpExpected;
tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
if (tmpExpected < 0) if (tmpExpected < 0)
return false; return false;
nArgsExpected += tmpExpected; nArgsExpected += tmpExpected;
} }
else
{
// Any other Script with less than 15 sigops OK:
unsigned int sigops = subscript.GetSigOpCount(true);
// ... extra data left on the stack after execution is OK, too:
return (sigops <= MAX_P2SH_SIGOPS);
}
}
if (stack.size() != (unsigned int)nArgsExpected) if (stack.size() != (unsigned int)nArgsExpected)
return false; return false;

2
src/main.h
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@ -43,6 +43,8 @@ static const unsigned int DEFAULT_BLOCK_PRIORITY_SIZE = 50000;
static const unsigned int MAX_STANDARD_TX_SIZE = 100000; static const unsigned int MAX_STANDARD_TX_SIZE = 100000;
/** The maximum allowed number of signature check operations in a block (network rule) */ /** The maximum allowed number of signature check operations in a block (network rule) */
static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50; static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
/** Maxiumum number of signature check operations in an IsStandard() P2SH script */
static const unsigned int MAX_P2SH_SIGOPS = 15;
/** The maximum number of orphan transactions kept in memory */ /** The maximum number of orphan transactions kept in memory */
static const unsigned int MAX_ORPHAN_TRANSACTIONS = MAX_BLOCK_SIZE/100; static const unsigned int MAX_ORPHAN_TRANSACTIONS = MAX_BLOCK_SIZE/100;
/** Default for -maxorphanblocks, maximum number of orphan blocks kept in memory */ /** Default for -maxorphanblocks, maximum number of orphan blocks kept in memory */

118
src/test/script_P2SH_tests.cpp
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@ -256,46 +256,61 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
CCoinsView coinsDummy; CCoinsView coinsDummy;
CCoinsViewCache coins(coinsDummy); CCoinsViewCache coins(coinsDummy);
CBasicKeyStore keystore; CBasicKeyStore keystore;
CKey key[3]; CKey key[6];
vector<CPubKey> keys; vector<CPubKey> keys;
for (int i = 0; i < 3; i++) for (int i = 0; i < 6; i++)
{ {
key[i].MakeNewKey(true); key[i].MakeNewKey(true);
keystore.AddKey(key[i]); keystore.AddKey(key[i]);
keys.push_back(key[i].GetPubKey());
} }
for (int i = 0; i < 3; i++)
keys.push_back(key[i].GetPubKey());
CMutableTransaction txFrom; CMutableTransaction txFrom;
txFrom.vout.resize(6); txFrom.vout.resize(7);
// First three are standard: // First three are standard:
CScript pay1; pay1.SetDestination(key[0].GetPubKey().GetID()); CScript pay1; pay1.SetDestination(key[0].GetPubKey().GetID());
keystore.AddCScript(pay1); keystore.AddCScript(pay1);
CScript payScriptHash1; payScriptHash1.SetDestination(pay1.GetID());
CScript pay1of3; pay1of3.SetMultisig(1, keys); CScript pay1of3; pay1of3.SetMultisig(1, keys);
txFrom.vout[0].scriptPubKey = payScriptHash1; txFrom.vout[0].scriptPubKey.SetDestination(pay1.GetID()); // P2SH (OP_CHECKSIG)
txFrom.vout[0].nValue = 1000; txFrom.vout[0].nValue = 1000;
txFrom.vout[1].scriptPubKey = pay1; txFrom.vout[1].scriptPubKey = pay1; // ordinary OP_CHECKSIG
txFrom.vout[1].nValue = 2000; txFrom.vout[1].nValue = 2000;
txFrom.vout[2].scriptPubKey = pay1of3; txFrom.vout[2].scriptPubKey = pay1of3; // ordinary OP_CHECKMULTISIG
txFrom.vout[2].nValue = 3000; txFrom.vout[2].nValue = 3000;
// Last three non-standard: // vout[3] is complicated 1-of-3 AND 2-of-3
CScript empty; // ... that is OK if wrapped in P2SH:
keystore.AddCScript(empty); CScript oneAndTwo;
txFrom.vout[3].scriptPubKey = empty; oneAndTwo << OP_1 << key[0].GetPubKey() << key[1].GetPubKey() << key[2].GetPubKey();
oneAndTwo << OP_3 << OP_CHECKMULTISIGVERIFY;
oneAndTwo << OP_2 << key[3].GetPubKey() << key[4].GetPubKey() << key[5].GetPubKey();
oneAndTwo << OP_3 << OP_CHECKMULTISIG;
keystore.AddCScript(oneAndTwo);
txFrom.vout[3].scriptPubKey.SetDestination(oneAndTwo.GetID());
txFrom.vout[3].nValue = 4000; txFrom.vout[3].nValue = 4000;
// Can't use SetPayToScriptHash, it checks for the empty Script. So:
txFrom.vout[4].scriptPubKey << OP_HASH160 << Hash160(empty) << OP_EQUAL; // vout[4] is max sigops:
CScript fifteenSigops; fifteenSigops << OP_1;
for (int i = 0; i < MAX_P2SH_SIGOPS; i++)
fifteenSigops << key[i%3].GetPubKey();
fifteenSigops << OP_15 << OP_CHECKMULTISIG;
keystore.AddCScript(fifteenSigops);
txFrom.vout[4].scriptPubKey.SetDestination(fifteenSigops.GetID());
txFrom.vout[4].nValue = 5000; txFrom.vout[4].nValue = 5000;
CScript oneOfEleven;
oneOfEleven << OP_1; // vout[5/6] are non-standard because they exceed MAX_P2SH_SIGOPS
for (int i = 0; i < 11; i++) CScript sixteenSigops; sixteenSigops << OP_16 << OP_CHECKMULTISIG;
oneOfEleven << key[0].GetPubKey(); keystore.AddCScript(sixteenSigops);
oneOfEleven << OP_11 << OP_CHECKMULTISIG; txFrom.vout[5].scriptPubKey.SetDestination(fifteenSigops.GetID());
txFrom.vout[5].scriptPubKey.SetDestination(oneOfEleven.GetID()); txFrom.vout[5].nValue = 5000;
txFrom.vout[5].nValue = 6000; CScript twentySigops; twentySigops << OP_CHECKMULTISIG;
keystore.AddCScript(twentySigops);
txFrom.vout[6].scriptPubKey.SetDestination(twentySigops.GetID());
txFrom.vout[6].nValue = 6000;
coins.SetCoins(txFrom.GetHash(), CCoins(txFrom, 0)); coins.SetCoins(txFrom.GetHash(), CCoins(txFrom, 0));
@ -303,19 +318,24 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
txTo.vout.resize(1); txTo.vout.resize(1);
txTo.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID()); txTo.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
txTo.vin.resize(3); txTo.vin.resize(5);
txTo.vin[0].prevout.n = 0; for (int i = 0; i < 5; i++)
txTo.vin[0].prevout.hash = txFrom.GetHash(); {
txTo.vin[i].prevout.n = i;
txTo.vin[i].prevout.hash = txFrom.GetHash();
}
BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 0)); BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 0));
txTo.vin[1].prevout.n = 1;
txTo.vin[1].prevout.hash = txFrom.GetHash();
BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 1)); BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 1));
txTo.vin[2].prevout.n = 2;
txTo.vin[2].prevout.hash = txFrom.GetHash();
BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 2)); BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 2));
// SignSignature doesn't know how to sign these. We're
// not testing validating signatures, so just create
// dummy signatures that DO include the correct P2SH scripts:
txTo.vin[3].scriptSig << OP_11 << OP_11 << static_cast<vector<unsigned char> >(oneAndTwo);
txTo.vin[4].scriptSig << static_cast<vector<unsigned char> >(fifteenSigops);
BOOST_CHECK(::AreInputsStandard(txTo, coins)); BOOST_CHECK(::AreInputsStandard(txTo, coins));
BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txTo, coins), 1U); // 22 P2SH sigops for all inputs (1 for vin[0], 6 for vin[3], 15 for vin[4]
BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txTo, coins), 22U);
// Make sure adding crap to the scriptSigs makes them non-standard: // Make sure adding crap to the scriptSigs makes them non-standard:
for (int i = 0; i < 3; i++) for (int i = 0; i < 3; i++)
@ -326,23 +346,29 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
txTo.vin[i].scriptSig = t; txTo.vin[i].scriptSig = t;
} }
CMutableTransaction txToNonStd; CMutableTransaction txToNonStd1;
txToNonStd.vout.resize(1); txToNonStd1.vout.resize(1);
txToNonStd.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID()); txToNonStd1.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
txToNonStd.vout[0].nValue = 1000; txToNonStd1.vout[0].nValue = 1000;
txToNonStd.vin.resize(2); txToNonStd1.vin.resize(1);
txToNonStd.vin[0].prevout.n = 4; txToNonStd1.vin[0].prevout.n = 5;
txToNonStd.vin[0].prevout.hash = txFrom.GetHash(); txToNonStd1.vin[0].prevout.hash = txFrom.GetHash();
txToNonStd.vin[0].scriptSig << Serialize(empty); txToNonStd1.vin[0].scriptSig << static_cast<vector<unsigned char> >(sixteenSigops);
txToNonStd.vin[1].prevout.n = 5;
txToNonStd.vin[1].prevout.hash = txFrom.GetHash(); BOOST_CHECK(!::AreInputsStandard(txToNonStd1, coins));
txToNonStd.vin[1].scriptSig << OP_0 << Serialize(oneOfEleven); BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txToNonStd1, coins), 16U);
BOOST_CHECK(!::AreInputsStandard(txToNonStd, coins)); CMutableTransaction txToNonStd2;
BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txToNonStd, coins), 11U); txToNonStd2.vout.resize(1);
txToNonStd2.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
txToNonStd.vin[0].scriptSig.clear(); txToNonStd2.vout[0].nValue = 1000;
BOOST_CHECK(!::AreInputsStandard(txToNonStd, coins)); txToNonStd2.vin.resize(1);
txToNonStd2.vin[0].prevout.n = 6;
txToNonStd2.vin[0].prevout.hash = txFrom.GetHash();
txToNonStd2.vin[0].scriptSig << static_cast<vector<unsigned char> >(twentySigops);
BOOST_CHECK(!::AreInputsStandard(txToNonStd2, coins));
BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txToNonStd2, coins), 20U);
} }
BOOST_AUTO_TEST_SUITE_END() BOOST_AUTO_TEST_SUITE_END()

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