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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core 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
*
* 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, const bool witnessEnabled)
{
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;
} else if (whichType == TX_NULL_DATA &&
(!fAcceptDatacarrier || scriptPubKey.size() > nMaxDatacarrierBytes))
return false;
else if (!witnessEnabled && (whichType == TX_WITNESS_V0_KEYHASH || whichType == TX_WITNESS_V0_SCRIPTHASH))
return false;
return whichType != TX_NONSTANDARD;
}
bool IsStandardTx(const CTransaction& tx, std::string& reason, const bool witnessEnabled)
{
if (tx.nVersion > CTransaction::MAX_STANDARD_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_WEIGHT mitigates CPU exhaustion attacks.
unsigned int sz = GetTransactionWeight(tx);
if (sz >= MAX_STANDARD_TX_WEIGHT) {
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, witnessEnabled)) {
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;
if (whichType == TX_SCRIPTHASH)
{
std::vector<std::vector<unsigned char> > stack;
// convert the scriptSig into a stack, so we can inspect the redeemScript
if (!EvalScript(stack, tx.vin[i].scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker(), SIGVERSION_BASE))
return false;
if (stack.empty())
return false;
CScript subscript(stack.back().begin(), stack.back().end());
if (subscript.GetSigOpCount(true) > MAX_P2SH_SIGOPS) {
return false;
}
}
}
return true;
}
bool IsWitnessStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
{
if (tx.IsCoinBase())
return true; // Coinbases are skipped
for (unsigned int i = 0; i < tx.vin.size(); i++)
{
// We don't care if witness for this input is empty, since it must not be bloated.
// If the script is invalid without witness, it would be caught sooner or later during validation.
if (tx.wit.vtxinwit[i].IsNull())
continue;
const CTxOut &prev = mapInputs.GetOutputFor(tx.vin[i]);
// get the scriptPubKey corresponding to this input:
CScript prevScript = prev.scriptPubKey;
if (prevScript.IsPayToScriptHash()) {
std::vector <std::vector<unsigned char> > stack;
// If the scriptPubKey is P2SH, we try to extract the redeemScript casually by converting the scriptSig
// into a stack. We do not check IsPushOnly nor compare the hash as these will be done later anyway.
// If the check fails at this stage, we know that this txid must be a bad one.
if (!EvalScript(stack, tx.vin[i].scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker(), SIGVERSION_BASE))
return false;
if (stack.empty())
return false;
prevScript = CScript(stack.back().begin(), stack.back().end());
}
int witnessversion = 0;
std::vector<unsigned char> witnessprogram;
// Non-witness program must not be associated with any witness
if (!prevScript.IsWitnessProgram(witnessversion, witnessprogram))
return false;
// Check P2WSH standard limits
if (witnessversion == 0 && witnessprogram.size() == 32) {
if (tx.wit.vtxinwit[i].scriptWitness.stack.back().size() > MAX_STANDARD_P2WSH_SCRIPT_SIZE)
return false;
size_t sizeWitnessStack = tx.wit.vtxinwit[i].scriptWitness.stack.size() - 1;
if (sizeWitnessStack > MAX_STANDARD_P2WSH_STACK_ITEMS)
return false;
for (unsigned int j = 0; j < sizeWitnessStack; j++) {
if (tx.wit.vtxinwit[i].scriptWitness.stack[j].size() > MAX_STANDARD_P2WSH_STACK_ITEM_SIZE)
return false;
}
}
}
return true;
}
unsigned int nBytesPerSigOp = DEFAULT_BYTES_PER_SIGOP;
int64_t GetVirtualTransactionSize(int64_t nWeight, int64_t nSigOpCost)
{
return (std::max(nWeight, nSigOpCost * nBytesPerSigOp) + WITNESS_SCALE_FACTOR - 1) / WITNESS_SCALE_FACTOR;
}
int64_t GetVirtualTransactionSize(const CTransaction& tx, int64_t nSigOpCost)
{
return GetVirtualTransactionSize(GetTransactionWeight(tx), nSigOpCost);
}
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