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

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.
0.10
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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  1. 37
      src/main.cpp
  2. 2
      src/main.h
  3. 118
      src/test/script_P2SH_tests.cpp

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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