diff options
Diffstat (limited to 'src/policy')
| -rw-r--r-- | src/policy/policy.cpp | 178 | ||||
| -rw-r--r-- | src/policy/policy.h | 17 |
2 files changed, 195 insertions, 0 deletions
diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp new file mode 100644 index 0000000000..169fef4af4 --- /dev/null +++ b/src/policy/policy.cpp @@ -0,0 +1,178 @@ +// Copyright (c) 2009-2010 Satoshi Nakamoto +// Copyright (c) 2009-2014 The Bitcoin developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +// NOTE: This file is intended to be customised by the end user, and includes only local node policy logic + +#include "policy/policy.h" + +#include "main.h" +#include "tinyformat.h" +#include "util.h" +#include "utilstrencodings.h" + +#include <boost/foreach.hpp> + + /** + * Check transaction inputs to mitigate two + * potential denial-of-service attacks: + * + * 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 + * + * Check transaction inputs, and make sure any + * pay-to-script-hash transactions are evaluating IsStandard scripts + * + * 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 + */ + +bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType) +{ + std::vector<std::vector<unsigned char> > vSolutions; + if (!Solver(scriptPubKey, whichType, vSolutions)) + return false; + + if (whichType == TX_MULTISIG) + { + unsigned char m = vSolutions.front()[0]; + unsigned char n = vSolutions.back()[0]; + // Support up to x-of-3 multisig txns as standard + if (n < 1 || n > 3) + return false; + if (m < 1 || m > n) + return false; + } + + return whichType != TX_NONSTANDARD; +} + +bool IsStandardTx(const CTransaction& tx, std::string& reason) +{ + if (tx.nVersion > CTransaction::CURRENT_VERSION || tx.nVersion < 1) { + reason = "version"; + return false; + } + + // Extremely large transactions with lots of inputs can cost the network + // almost as much to process as they cost the sender in fees, because + // computing signature hashes is O(ninputs*txsize). Limiting transactions + // to MAX_STANDARD_TX_SIZE mitigates CPU exhaustion attacks. + unsigned int sz = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION); + if (sz >= MAX_STANDARD_TX_SIZE) { + reason = "tx-size"; + return false; + } + + BOOST_FOREACH(const CTxIn& txin, tx.vin) + { + // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed + // keys. (remember the 520 byte limit on redeemScript size) That works + // out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)+3=1627 + // bytes of scriptSig, which we round off to 1650 bytes for some minor + // future-proofing. That's also enough to spend a 20-of-20 + // CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not + // considered standard) + if (txin.scriptSig.size() > 1650) { + reason = "scriptsig-size"; + return false; + } + if (!txin.scriptSig.IsPushOnly()) { + reason = "scriptsig-not-pushonly"; + return false; + } + } + + unsigned int nDataOut = 0; + txnouttype whichType; + BOOST_FOREACH(const CTxOut& txout, tx.vout) { + if (!::IsStandard(txout.scriptPubKey, whichType)) { + reason = "scriptpubkey"; + return false; + } + + if (whichType == TX_NULL_DATA) + nDataOut++; + else if ((whichType == TX_MULTISIG) && (!fIsBareMultisigStd)) { + reason = "bare-multisig"; + return false; + } else if (txout.IsDust(::minRelayTxFee)) { + reason = "dust"; + return false; + } + } + + // only one OP_RETURN txout is permitted + if (nDataOut > 1) { + reason = "multi-op-return"; + return false; + } + + return true; +} + +bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs) +{ + if (tx.IsCoinBase()) + return true; // Coinbases don't use vin normally + + for (unsigned int i = 0; i < tx.vin.size(); i++) + { + const CTxOut& prev = mapInputs.GetOutputFor(tx.vin[i]); + + std::vector<std::vector<unsigned char> > vSolutions; + txnouttype whichType; + // get the scriptPubKey corresponding to this input: + const CScript& prevScript = prev.scriptPubKey; + if (!Solver(prevScript, whichType, vSolutions)) + return false; + int nArgsExpected = ScriptSigArgsExpected(whichType, vSolutions); + if (nArgsExpected < 0) + return false; + + // 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 + // IsStandardTx() will have already returned false + // and this method isn't called. + std::vector<std::vector<unsigned char> > stack; + if (!EvalScript(stack, tx.vin[i].scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker())) + return false; + + if (whichType == TX_SCRIPTHASH) + { + if (stack.empty()) + return false; + CScript subscript(stack.back().begin(), stack.back().end()); + std::vector<std::vector<unsigned char> > vSolutions2; + txnouttype whichType2; + 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) + return false; + } + + return true; +} diff --git a/src/policy/policy.h b/src/policy/policy.h index 48e192d559..1551aecde8 100644 --- a/src/policy/policy.h +++ b/src/policy/policy.h @@ -10,6 +10,10 @@ #include "script/interpreter.h" #include "script/standard.h" +#include <string> + +class CCoinsViewCache; + /** Default for -blockmaxsize and -blockminsize, which control the range of sizes the mining code will create **/ static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000; static const unsigned int DEFAULT_BLOCK_MIN_SIZE = 0; @@ -38,4 +42,17 @@ static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY /** For convenience, standard but not mandatory verify flags. */ static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS; +bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType); + /** + * Check for standard transaction types + * @return True if all outputs (scriptPubKeys) use only standard transaction forms + */ +bool IsStandardTx(const CTransaction& tx, std::string& reason); + /** + * Check for standard transaction types + * @param[in] mapInputs Map of previous transactions that have outputs we're spending + * @return True if all inputs (scriptSigs) use only standard transaction forms + */ +bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs); + #endif // BITCOIN_POLICY_H |