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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.
This commit is contained in:
Gavin Andresen
2014-06-17 14:18:13 -04:00
parent 36db6633c3
commit 7f3b4e9569
3 changed files with 95 additions and 64 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
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
// pay-to-script-hash transactions are evaluating IsStandard scripts
// Check transaction inputs to mitigate two
// potential denial-of-service attacks:
//
// Why bother? To avoid denial-of-service attacks; an attacker
// can submit a standard HASH... OP_EQUAL transaction,
// which will get accepted into blocks. The redemption
// script can be anything; an attacker could use a very
// expensive-to-check-upon-redemption script like:
// DUP CHECKSIG DROP ... repeated 100 times... OP_1
// 1. scriptSigs with extra data stuffed into them,
// not consumed by scriptPubKey (or P2SH script)
// 2. P2SH scripts with a crazy number of expensive
// CHECKSIG/CHECKMULTISIG operations
//
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
// non-standard. Note that this EvalScript() call will
// be quick, because if there are any operations
// beside "push data" in the scriptSig the
// IsStandard() call returns false
// beside "push data" in the scriptSig
// IsStandard() will have already returned false
// and this method isn't called.
vector<vector<unsigned char> > stack;
if (!EvalScript(stack, tx.vin[i].scriptSig, tx, i, false, 0))
return false;
@@ -627,16 +626,20 @@ bool AreInputsStandard(const CTransaction& tx, CCoinsViewCache& mapInputs)
CScript subscript(stack.back().begin(), stack.back().end());
vector<vector<unsigned char> > vSolutions2;
txnouttype whichType2;
if (!Solver(subscript, whichType2, vSolutions2))
return false;
if (whichType2 == TX_SCRIPTHASH)
return false;
int tmpExpected;
tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
if (tmpExpected < 0)
return false;
nArgsExpected += tmpExpected;
if (Solver(subscript, whichType2, vSolutions2))
{
int tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
if (tmpExpected < 0)
return false;
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)