220 lines
8 KiB
C++
220 lines
8 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2016 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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// NOTE: This file is intended to be customised by the end user, and includes only local node policy logic
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#include "policy/policy.h"
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#include "validation.h"
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#include "tinyformat.h"
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#include "util.h"
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#include "utilstrencodings.h"
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#include <boost/foreach.hpp>
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/**
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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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* 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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* 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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*/
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bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType, const bool witnessEnabled)
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{
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std::vector<std::vector<unsigned char> > vSolutions;
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if (!Solver(scriptPubKey, whichType, vSolutions))
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return false;
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if (whichType == TX_MULTISIG)
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{
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unsigned char m = vSolutions.front()[0];
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unsigned char n = vSolutions.back()[0];
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// Support up to x-of-3 multisig txns as standard
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if (n < 1 || n > 3)
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return false;
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if (m < 1 || m > n)
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return false;
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} else if (whichType == TX_NULL_DATA &&
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(!fAcceptDatacarrier || scriptPubKey.size() > nMaxDatacarrierBytes))
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return false;
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else if (!witnessEnabled && (whichType == TX_WITNESS_V0_KEYHASH || whichType == TX_WITNESS_V0_SCRIPTHASH))
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return false;
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return whichType != TX_NONSTANDARD;
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}
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bool IsStandardTx(const CTransaction& tx, std::string& reason, const bool witnessEnabled)
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{
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if (tx.nVersion > CTransaction::MAX_STANDARD_VERSION || tx.nVersion < 1) {
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reason = "version";
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return false;
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}
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// Extremely large transactions with lots of inputs can cost the network
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// almost as much to process as they cost the sender in fees, because
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// computing signature hashes is O(ninputs*txsize). Limiting transactions
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// to MAX_STANDARD_TX_WEIGHT mitigates CPU exhaustion attacks.
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unsigned int sz = GetTransactionWeight(tx);
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if (sz >= MAX_STANDARD_TX_WEIGHT) {
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reason = "tx-size";
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return false;
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}
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BOOST_FOREACH(const CTxIn& txin, tx.vin)
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{
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// Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
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// keys (remember the 520 byte limit on redeemScript size). That works
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// out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)+3=1627
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// bytes of scriptSig, which we round off to 1650 bytes for some minor
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// future-proofing. That's also enough to spend a 20-of-20
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// CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not
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// considered standard.
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if (txin.scriptSig.size() > 1650) {
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reason = "scriptsig-size";
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return false;
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}
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if (!txin.scriptSig.IsPushOnly()) {
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reason = "scriptsig-not-pushonly";
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return false;
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}
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}
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unsigned int nDataOut = 0;
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txnouttype whichType;
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BOOST_FOREACH(const CTxOut& txout, tx.vout) {
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if (!::IsStandard(txout.scriptPubKey, whichType, witnessEnabled)) {
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reason = "scriptpubkey";
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return false;
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}
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if (whichType == TX_NULL_DATA)
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nDataOut++;
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else if ((whichType == TX_MULTISIG) && (!fIsBareMultisigStd)) {
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reason = "bare-multisig";
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return false;
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} else if (txout.IsDust(::minRelayTxFee)) {
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reason = "dust";
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return false;
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}
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}
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// only one OP_RETURN txout is permitted
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if (nDataOut > 1) {
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reason = "multi-op-return";
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return false;
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}
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return true;
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}
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bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
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{
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if (tx.IsCoinBase())
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return true; // Coinbases don't use vin normally
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for (unsigned int i = 0; i < tx.vin.size(); i++)
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{
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const CTxOut& prev = mapInputs.GetOutputFor(tx.vin[i]);
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std::vector<std::vector<unsigned char> > vSolutions;
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txnouttype whichType;
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// get the scriptPubKey corresponding to this input:
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const CScript& prevScript = prev.scriptPubKey;
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if (!Solver(prevScript, whichType, vSolutions))
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return false;
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if (whichType == TX_SCRIPTHASH)
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{
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std::vector<std::vector<unsigned char> > stack;
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// convert the scriptSig into a stack, so we can inspect the redeemScript
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if (!EvalScript(stack, tx.vin[i].scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker(), SIGVERSION_BASE))
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return false;
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if (stack.empty())
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return false;
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CScript subscript(stack.back().begin(), stack.back().end());
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if (subscript.GetSigOpCount(true) > MAX_P2SH_SIGOPS) {
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return false;
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}
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}
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}
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return true;
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}
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bool IsWitnessStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs)
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{
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if (tx.IsCoinBase())
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return true; // Coinbases are skipped
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for (unsigned int i = 0; i < tx.vin.size(); i++)
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{
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// We don't care if witness for this input is empty, since it must not be bloated.
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// If the script is invalid without witness, it would be caught sooner or later during validation.
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if (tx.wit.vtxinwit[i].IsNull())
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continue;
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const CTxOut &prev = mapInputs.GetOutputFor(tx.vin[i]);
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// get the scriptPubKey corresponding to this input:
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CScript prevScript = prev.scriptPubKey;
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if (prevScript.IsPayToScriptHash()) {
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std::vector <std::vector<unsigned char> > stack;
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// If the scriptPubKey is P2SH, we try to extract the redeemScript casually by converting the scriptSig
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// into a stack. We do not check IsPushOnly nor compare the hash as these will be done later anyway.
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// If the check fails at this stage, we know that this txid must be a bad one.
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if (!EvalScript(stack, tx.vin[i].scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker(), SIGVERSION_BASE))
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return false;
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if (stack.empty())
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return false;
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prevScript = CScript(stack.back().begin(), stack.back().end());
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}
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int witnessversion = 0;
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std::vector<unsigned char> witnessprogram;
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// Non-witness program must not be associated with any witness
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if (!prevScript.IsWitnessProgram(witnessversion, witnessprogram))
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return false;
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// Check P2WSH standard limits
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if (witnessversion == 0 && witnessprogram.size() == 32) {
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if (tx.wit.vtxinwit[i].scriptWitness.stack.back().size() > MAX_STANDARD_P2WSH_SCRIPT_SIZE)
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return false;
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size_t sizeWitnessStack = tx.wit.vtxinwit[i].scriptWitness.stack.size() - 1;
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if (sizeWitnessStack > MAX_STANDARD_P2WSH_STACK_ITEMS)
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return false;
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for (unsigned int j = 0; j < sizeWitnessStack; j++) {
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if (tx.wit.vtxinwit[i].scriptWitness.stack[j].size() > MAX_STANDARD_P2WSH_STACK_ITEM_SIZE)
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return false;
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}
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}
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}
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return true;
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}
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unsigned int nBytesPerSigOp = DEFAULT_BYTES_PER_SIGOP;
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int64_t GetVirtualTransactionSize(int64_t nWeight, int64_t nSigOpCost)
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{
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return (std::max(nWeight, nSigOpCost * nBytesPerSigOp) + WITNESS_SCALE_FACTOR - 1) / WITNESS_SCALE_FACTOR;
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}
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int64_t GetVirtualTransactionSize(const CTransaction& tx, int64_t nSigOpCost)
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{
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return GetVirtualTransactionSize(GetTransactionWeight(tx), nSigOpCost);
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}
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