The first checks on a transaction

1// Copyright (c) 2017-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#include <consensus/tx_check.h>
6
7#include <consensus/amount.h>
8#include <consensus/consensus.h>
9#include <consensus/validation.h>
10#include <primitives/transaction.h>
11#include <script/script.h>
12#include <serialize.h>
13
14#include <set>
15#include <string>
16#include <utility>
17#include <vector>
18
19bool CheckTransaction(const CTransaction& tx, TxValidationState& state)
20{
21    // Basic checks that don't depend on any context
22    if (tx.vin.empty())
23        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vin-empty");
24    if (tx.vout.empty())
25        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vout-empty");
26    // Size limits (this doesn't take the witness into account, as that hasn't been checked for malleability)
27    if (::GetSerializeSize(TX_NO_WITNESS(tx)) * WITNESS_SCALE_FACTOR > MAX_BLOCK_WEIGHT) {
28        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-oversize");
29    }
30
31    // Check for negative or overflow output values (see CVE-2010-5139)
32    CAmount nValueOut = 0;
33    for (const auto& txout : tx.vout)
34    {
35        if (txout.nValue < 0)
36            return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vout-negative");
37        if (txout.nValue > MAX_MONEY)
38            return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vout-toolarge");
39        nValueOut += txout.nValue;
40        if (!MoneyRange(nValueOut))
41            return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-txouttotal-toolarge");
42    }
43
44    // Check for duplicate inputs (see CVE-2018-17144)
45    // While Consensus::CheckTxInputs does check if all inputs of a tx are available, and UpdateCoins marks all inputs
46    // of a tx as spent, it does not check if the tx has duplicate inputs.
47    // Failure to run this check will result in either a crash or an inflation bug, depending on the implementation of
48    // the underlying coins database.
49    std::set<COutPoint> vInOutPoints;
50    for (const auto& txin : tx.vin) {
51        if (!vInOutPoints.insert(txin.prevout).second)
52            return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-inputs-duplicate");
53    }
54
55    if (tx.IsCoinBase())
56    {
57        if (tx.vin[0].scriptSig.size() < 2 || tx.vin[0].scriptSig.size() > 100)
58            return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-cb-length");
59    }
60    else
61    {
62        for (const auto& txin : tx.vin)
63            if (txin.prevout.IsNull())
64                return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-prevout-null");
65    }
66
67    return true;
68}
69