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.
This commit is contained in:
Gavin Andresen
parent
36db6633c3
commit
7f3b4e9569
3 changed files with 95 additions and 64 deletions
43
src/main.cpp
43
src/main.cpp
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@ -582,15 +582,13 @@ bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
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}
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//
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// Check transaction inputs, and make sure any
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// pay-to-script-hash transactions are evaluating IsStandard scripts
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// Check transaction inputs to mitigate two
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// potential denial-of-service attacks:
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//
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// Why bother? To avoid denial-of-service attacks; an attacker
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// can submit a standard HASH... OP_EQUAL transaction,
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// which will get accepted into blocks. The redemption
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// script can be anything; an attacker could use a very
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// expensive-to-check-upon-redemption script like:
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// DUP CHECKSIG DROP ... repeated 100 times... OP_1
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// 1. scriptSigs with extra data stuffed into them,
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// not consumed by scriptPubKey (or P2SH script)
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// 2. P2SH scripts with a crazy number of expensive
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// CHECKSIG/CHECKMULTISIG operations
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//
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bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
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{
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@ -614,8 +612,9 @@ bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
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// Transactions with extra stuff in their scriptSigs are
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// non-standard. Note that this EvalScript() call will
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// be quick, because if there are any operations
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// beside "push data" in the scriptSig the
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// IsStandard() call returns false
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// beside "push data" in the scriptSig
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// IsStandard() will have already returned false
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// and this method isn't called.
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vector<vector<unsigned char> > stack;
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if (!EvalScript(stack, tx.vin[i].scriptSig, tx, i, false, 0))
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return false;
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@ -627,16 +626,20 @@ bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
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CScript subscript(stack.back().begin(), stack.back().end());
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vector<vector<unsigned char> > vSolutions2;
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txnouttype whichType2;
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if (!Solver(subscript, whichType2, vSolutions2))
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return false;
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if (whichType2 == TX_SCRIPTHASH)
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return false;
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int tmpExpected;
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tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
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if (tmpExpected < 0)
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return false;
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nArgsExpected += tmpExpected;
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if (Solver(subscript, whichType2, vSolutions2))
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{
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int tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
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if (tmpExpected < 0)
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return false;
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nArgsExpected += tmpExpected;
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}
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else
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{
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// Any other Script with less than 15 sigops OK:
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unsigned int sigops = subscript.GetSigOpCount(true);
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// ... extra data left on the stack after execution is OK, too:
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return (sigops <= MAX_P2SH_SIGOPS);
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}
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}
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if (stack.size() != (unsigned int)nArgsExpected)
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@ -43,6 +43,8 @@ static const unsigned int DEFAULT_BLOCK_PRIORITY_SIZE = 50000;
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static const unsigned int MAX_STANDARD_TX_SIZE = 100000;
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/** The maximum allowed number of signature check operations in a block (network rule) */
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static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
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/** Maxiumum number of signature check operations in an IsStandard() P2SH script */
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static const unsigned int MAX_P2SH_SIGOPS = 15;
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/** The maximum number of orphan transactions kept in memory */
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static const unsigned int MAX_ORPHAN_TRANSACTIONS = MAX_BLOCK_SIZE/100;
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/** Default for -maxorphanblocks, maximum number of orphan blocks kept in memory */
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@ -256,46 +256,61 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
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CCoinsView coinsDummy;
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CCoinsViewCache coins(coinsDummy);
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CBasicKeyStore keystore;
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CKey key[3];
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CKey key[6];
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vector<CPubKey> keys;
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for (int i = 0; i < 3; i++)
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for (int i = 0; i < 6; i++)
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{
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key[i].MakeNewKey(true);
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keystore.AddKey(key[i]);
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keys.push_back(key[i].GetPubKey());
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}
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for (int i = 0; i < 3; i++)
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keys.push_back(key[i].GetPubKey());
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CMutableTransaction txFrom;
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txFrom.vout.resize(6);
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txFrom.vout.resize(7);
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// First three are standard:
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CScript pay1; pay1.SetDestination(key[0].GetPubKey().GetID());
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keystore.AddCScript(pay1);
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CScript payScriptHash1; payScriptHash1.SetDestination(pay1.GetID());
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CScript pay1of3; pay1of3.SetMultisig(1, keys);
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txFrom.vout[0].scriptPubKey = payScriptHash1;
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txFrom.vout[0].scriptPubKey.SetDestination(pay1.GetID()); // P2SH (OP_CHECKSIG)
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txFrom.vout[0].nValue = 1000;
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txFrom.vout[1].scriptPubKey = pay1;
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txFrom.vout[1].scriptPubKey = pay1; // ordinary OP_CHECKSIG
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txFrom.vout[1].nValue = 2000;
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txFrom.vout[2].scriptPubKey = pay1of3;
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txFrom.vout[2].scriptPubKey = pay1of3; // ordinary OP_CHECKMULTISIG
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txFrom.vout[2].nValue = 3000;
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// Last three non-standard:
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CScript empty;
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keystore.AddCScript(empty);
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txFrom.vout[3].scriptPubKey = empty;
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// vout[3] is complicated 1-of-3 AND 2-of-3
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// ... that is OK if wrapped in P2SH:
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CScript oneAndTwo;
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oneAndTwo << OP_1 << key[0].GetPubKey() << key[1].GetPubKey() << key[2].GetPubKey();
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oneAndTwo << OP_3 << OP_CHECKMULTISIGVERIFY;
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oneAndTwo << OP_2 << key[3].GetPubKey() << key[4].GetPubKey() << key[5].GetPubKey();
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oneAndTwo << OP_3 << OP_CHECKMULTISIG;
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keystore.AddCScript(oneAndTwo);
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txFrom.vout[3].scriptPubKey.SetDestination(oneAndTwo.GetID());
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txFrom.vout[3].nValue = 4000;
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// Can't use SetPayToScriptHash, it checks for the empty Script. So:
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txFrom.vout[4].scriptPubKey << OP_HASH160 << Hash160(empty) << OP_EQUAL;
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// vout[4] is max sigops:
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CScript fifteenSigops; fifteenSigops << OP_1;
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for (int i = 0; i < MAX_P2SH_SIGOPS; i++)
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fifteenSigops << key[i%3].GetPubKey();
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fifteenSigops << OP_15 << OP_CHECKMULTISIG;
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keystore.AddCScript(fifteenSigops);
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txFrom.vout[4].scriptPubKey.SetDestination(fifteenSigops.GetID());
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txFrom.vout[4].nValue = 5000;
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CScript oneOfEleven;
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oneOfEleven << OP_1;
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for (int i = 0; i < 11; i++)
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oneOfEleven << key[0].GetPubKey();
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oneOfEleven << OP_11 << OP_CHECKMULTISIG;
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txFrom.vout[5].scriptPubKey.SetDestination(oneOfEleven.GetID());
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txFrom.vout[5].nValue = 6000;
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// vout[5/6] are non-standard because they exceed MAX_P2SH_SIGOPS
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CScript sixteenSigops; sixteenSigops << OP_16 << OP_CHECKMULTISIG;
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keystore.AddCScript(sixteenSigops);
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txFrom.vout[5].scriptPubKey.SetDestination(fifteenSigops.GetID());
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txFrom.vout[5].nValue = 5000;
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CScript twentySigops; twentySigops << OP_CHECKMULTISIG;
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keystore.AddCScript(twentySigops);
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txFrom.vout[6].scriptPubKey.SetDestination(twentySigops.GetID());
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txFrom.vout[6].nValue = 6000;
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coins.SetCoins(txFrom.GetHash(), CCoins(txFrom, 0));
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@ -303,19 +318,24 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
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txTo.vout.resize(1);
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txTo.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
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txTo.vin.resize(3);
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txTo.vin[0].prevout.n = 0;
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txTo.vin[0].prevout.hash = txFrom.GetHash();
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txTo.vin.resize(5);
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for (int i = 0; i < 5; i++)
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{
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txTo.vin[i].prevout.n = i;
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txTo.vin[i].prevout.hash = txFrom.GetHash();
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}
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BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 0));
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txTo.vin[1].prevout.n = 1;
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txTo.vin[1].prevout.hash = txFrom.GetHash();
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BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 1));
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txTo.vin[2].prevout.n = 2;
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txTo.vin[2].prevout.hash = txFrom.GetHash();
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BOOST_CHECK(SignSignature(keystore, txFrom, txTo, 2));
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// SignSignature doesn't know how to sign these. We're
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// not testing validating signatures, so just create
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// dummy signatures that DO include the correct P2SH scripts:
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txTo.vin[3].scriptSig << OP_11 << OP_11 << static_cast<vector<unsigned char> >(oneAndTwo);
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txTo.vin[4].scriptSig << static_cast<vector<unsigned char> >(fifteenSigops);
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BOOST_CHECK(::AreInputsStandard(txTo, coins));
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BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txTo, coins), 1U);
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// 22 P2SH sigops for all inputs (1 for vin[0], 6 for vin[3], 15 for vin[4]
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BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txTo, coins), 22U);
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// Make sure adding crap to the scriptSigs makes them non-standard:
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for (int i = 0; i < 3; i++)
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@ -326,23 +346,29 @@ BOOST_AUTO_TEST_CASE(AreInputsStandard)
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txTo.vin[i].scriptSig = t;
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}
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CMutableTransaction txToNonStd;
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txToNonStd.vout.resize(1);
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txToNonStd.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
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txToNonStd.vout[0].nValue = 1000;
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txToNonStd.vin.resize(2);
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txToNonStd.vin[0].prevout.n = 4;
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txToNonStd.vin[0].prevout.hash = txFrom.GetHash();
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txToNonStd.vin[0].scriptSig << Serialize(empty);
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txToNonStd.vin[1].prevout.n = 5;
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txToNonStd.vin[1].prevout.hash = txFrom.GetHash();
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txToNonStd.vin[1].scriptSig << OP_0 << Serialize(oneOfEleven);
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CMutableTransaction txToNonStd1;
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txToNonStd1.vout.resize(1);
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txToNonStd1.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
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txToNonStd1.vout[0].nValue = 1000;
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txToNonStd1.vin.resize(1);
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txToNonStd1.vin[0].prevout.n = 5;
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txToNonStd1.vin[0].prevout.hash = txFrom.GetHash();
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txToNonStd1.vin[0].scriptSig << static_cast<vector<unsigned char> >(sixteenSigops);
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BOOST_CHECK(!::AreInputsStandard(txToNonStd, coins));
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BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txToNonStd, coins), 11U);
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BOOST_CHECK(!::AreInputsStandard(txToNonStd1, coins));
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BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txToNonStd1, coins), 16U);
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txToNonStd.vin[0].scriptSig.clear();
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BOOST_CHECK(!::AreInputsStandard(txToNonStd, coins));
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CMutableTransaction txToNonStd2;
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txToNonStd2.vout.resize(1);
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txToNonStd2.vout[0].scriptPubKey.SetDestination(key[1].GetPubKey().GetID());
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txToNonStd2.vout[0].nValue = 1000;
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txToNonStd2.vin.resize(1);
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txToNonStd2.vin[0].prevout.n = 6;
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txToNonStd2.vin[0].prevout.hash = txFrom.GetHash();
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txToNonStd2.vin[0].scriptSig << static_cast<vector<unsigned char> >(twentySigops);
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BOOST_CHECK(!::AreInputsStandard(txToNonStd2, coins));
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BOOST_CHECK_EQUAL(GetP2SHSigOpCount(txToNonStd2, coins), 20U);
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}
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BOOST_AUTO_TEST_SUITE_END()
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