policy.cpp

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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 <coins.h>
#include <common/system.h>
#include <policy/policy.h>
#include <script/interpreter.h>
 
Amount GetDustThreshold(const CTxOut &txout, const CFeeRate &dustRelayFeeIn) {
    if (txout.scriptPubKey.IsUnspendable()) {
        return Amount::zero();
    }
 
    size_t nSize = GetSerializeSize(txout);
 
    // the 148 mentioned above
    nSize += (32 + 4 + 1 + 107 + 4);
 
    return dustRelayFeeIn.GetFee(nSize);
}
 
bool IsDust(const CTxOut &txout, const CFeeRate &dustRelayFeeIn) {
    return (txout.nValue < GetDustThreshold(txout, dustRelayFeeIn));
}
 
bool IsStandard(const CScript &scriptPubKey,
                const std::optional<unsigned> &max_datacarrier_bytes,
                TxoutType &whichType) {
    std::vector<std::vector<uint8_t>> vSolutions;
    whichType = Solver(scriptPubKey, vSolutions);
 
    if (whichType == TxoutType::NONSTANDARD) {
        return false;
    } else if (whichType == TxoutType::MULTISIG) {
        uint8_t m = vSolutions.front()[0];
        uint8_t 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 == TxoutType::NULL_DATA) {
        if (!max_datacarrier_bytes ||
            scriptPubKey.size() > *max_datacarrier_bytes) {
            return false;
        }
    }
 
    return true;
}
 
bool IsStandardTx(const CTransaction &tx,
                  const std::optional<unsigned> &max_datacarrier_bytes,
                  bool permit_bare_multisig, const CFeeRate &dust_relay_fee,
                  std::string &reason) {
    // Only allow these tx versions, there is no point accepting a tx that
    // violates the consensus rules
    if (tx.nVersion > CTransaction::MAX_VERSION ||
        tx.nVersion < CTransaction::MIN_VERSION) {
        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.
    uint32_t sz = tx.GetTotalSize();
    if (sz > MAX_STANDARD_TX_SIZE) {
        reason = "tx-size";
        return false;
    }
 
    for (const CTxIn &txin : tx.vin) {
        if (txin.scriptSig.size() > MAX_TX_IN_SCRIPT_SIG_SIZE) {
            reason = "scriptsig-size";
            return false;
        }
        if (!txin.scriptSig.IsPushOnly()) {
            reason = "scriptsig-not-pushonly";
            return false;
        }
    }
 
    unsigned int nDataOut = 0;
    TxoutType whichType;
    for (const CTxOut &txout : tx.vout) {
        if (!::IsStandard(txout.scriptPubKey, max_datacarrier_bytes,
                          whichType)) {
            reason = "scriptpubkey";
            return false;
        }
 
        if (whichType == TxoutType::NULL_DATA) {
            nDataOut++;
        } else if ((whichType == TxoutType::MULTISIG) &&
                   (!permit_bare_multisig)) {
            reason = "bare-multisig";
            return false;
        } else if (IsDust(txout, dust_relay_fee)) {
            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,
                       uint32_t flags) {
    if (tx.IsCoinBase()) {
        // Coinbases don't use vin normally.
        return true;
    }
 
    for (const CTxIn &in : tx.vin) {
        const CTxOut &prev = mapInputs.AccessCoin(in.prevout).GetTxOut();
 
        std::vector<std::vector<uint8_t>> vSolutions;
        TxoutType whichType = Solver(prev.scriptPubKey, vSolutions);
        if (whichType == TxoutType::NONSTANDARD) {
            return false;
        }
    }
 
    return true;
}
 
int64_t GetVirtualTransactionSize(int64_t nSize, int64_t nSigChecks,
                                  unsigned int bytes_per_sigCheck) {
    return std::max(nSize, nSigChecks * bytes_per_sigCheck);
}
 
int64_t GetVirtualTransactionSize(const CTransaction &tx, int64_t nSigChecks,
                                  unsigned int bytes_per_sigCheck) {
    return GetVirtualTransactionSize(::GetSerializeSize(tx), nSigChecks,
                                     bytes_per_sigCheck);
}
 
int64_t GetVirtualTransactionInputSize(const CTxIn &txin, int64_t nSigChecks,
                                       unsigned int bytes_per_sigCheck) {
    return GetVirtualTransactionSize(::GetSerializeSize(txin), nSigChecks,
                                     bytes_per_sigCheck);
}