交易的独立验证
在第6章中，我们看到钱包软件通过收集UTXO（未使用的交易输出）、提供适当的身份验证数据，然后构建分配给新所有者的新输出来创建交易。然后，生成的交易被发送到比特币网络中的相邻节点，以便在整个比特币网络中传播。
然而，在将交易转发到其邻居之前，每个接收到交易的比特币节点都会首先验证该交易。这确保只有有效的交易才会在网络中传播，而无效的交易则会在首个遇到它们的节点处被丢弃。
每个节点都会根据长长的检查清单验证每个交易(可对比tx_check.cpp的CheckTransaction、validation.cpp来分析)：
交易的语法和数据结构必须正确。
输入和输出列表都不为空。
交易的重量足够小，以便使其适合在一个区块中。
每个输出值以及总值必须在允许的值范围内（大于等于零，但不超过2100万比特币）。
锁定时间等于INT_MAX，或者锁定时间和序列值符合锁定时间和BIP68规则。
交易中包含的签名操作（SIGOPS）的数量少于签名操作限制
花费的输出与内存池中的输出或主分支中未花费的输出匹配。
对于每个输入，如果引用的输出交易是coinbase输出，则必须至少有COINBASE_MATURITY（100）次确认。任何绝对或相对锁定时间也必须满足。节点可能在它们成熟之前转发交易到一个区块，因为如果包含在下一个区块中，它们就会成熟。
如果输入值的总和小于输出值的总和，则拒绝。
每个输入的脚本必须针对相应的输出脚本进行验证。
请注意，这些条件随着时间的推移而改变，以添加新功能或解决新类型的拒绝服务攻击。
通过在收到每个交易并在传播之前进行独立验证，每个节点构建了一个有效但尚未确认的交易池，称为内存池或mempool。
tx_check.cpp::CheckTransaction
bool CheckTransaction(const CTransaction& tx, TxValidationState& state)
{
// 输入和输出列表都不为空。
// Basic checks that don't depend on any context
if (tx.vin.empty())
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vin-empty");
if (tx.vout.empty())
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vout-empty");
// 交易的重量足够小，以便使其适合在一个区块中。
// Size limits (this doesn't take the witness into account, as that hasn't been checked for malleability)
if (::GetSerializeSize(TX_NO_WITNESS(tx)) * WITNESS_SCALE_FACTOR > MAX_BLOCK_WEIGHT) {
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-oversize");
}
// 每个输出值以及总值必须在允许的值范围内（大于等于零，但不超过2100万比特币）。
// Check for negative or overflow output values (see CVE-2010-5139)
CAmount nValueOut = 0;
for (const auto& txout : tx.vout)
{
if (txout.nValue < 0)
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vout-negative");
if (txout.nValue > MAX_MONEY)
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-vout-toolarge");
nValueOut += txout.nValue;
if (!MoneyRange(nValueOut))
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-txouttotal-toolarge");
}
// Check for duplicate inputs (see CVE-2018-17144)
// While Consensus::CheckTxInputs does check if all inputs of a tx are available, and UpdateCoins marks all inputs
// of a tx as spent, it does not check if the tx has duplicate inputs.
// Failure to run this check will result in either a crash or an inflation bug, depending on the implementation of
// the underlying coins database.
std::set<COutPoint> vInOutPoints;
for (const auto& txin : tx.vin) {
if (!vInOutPoints.insert(txin.prevout).second)
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-inputs-duplicate");
}
if (tx.IsCoinBase())
{
if (tx.vin[0].scriptSig.size() < 2 || tx.vin[0].scriptSig.size() > 100)
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-cb-length");
}
else
{
for (const auto& txin : tx.vin)
if (txin.prevout.IsNull())
return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-prevout-null");
}
return true;
}validation.cpp::CheckBlock
bool CheckBlock(const CBlock& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW, bool fCheckMerkleRoot)
{
// These are checks that are independent of context.
if (block.fChecked)
return true;
// Check that the header is valid (particularly PoW). This is mostly
// redundant with the call in AcceptBlockHeader.
if (!CheckBlockHeader(block, state, consensusParams, fCheckPOW))
return false;
// Signet only: check block solution
if (consensusParams.signet_blocks && fCheckPOW && !CheckSignetBlockSolution(block, consensusParams)) {
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-signet-blksig", "signet block signature validation failure");
}
// Check the merkle root.
if (fCheckMerkleRoot && !CheckMerkleRoot(block, state)) {
return false;
}
// All potential-corruption validation must be done before we do any
// transaction validation, as otherwise we may mark the header as invalid
// because we receive the wrong transactions for it.
// Note that witness malleability is checked in ContextualCheckBlock, so no
// checks that use witness data may be performed here.
// Size limits
if (block.vtx.empty() || block.vtx.size() * WITNESS_SCALE_FACTOR > MAX_BLOCK_WEIGHT || ::GetSerializeSize(TX_NO_WITNESS(block)) * WITNESS_SCALE_FACTOR > MAX_BLOCK_WEIGHT)
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-blk-length", "size limits failed");
// First transaction must be coinbase, the rest must not be
if (block.vtx.empty() || !block.vtx[0]->IsCoinBase())
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cb-missing", "first tx is not coinbase");
for (unsigned int i = 1; i < block.vtx.size(); i++)
if (block.vtx[i]->IsCoinBase())
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-cb-multiple", "more than one coinbase");
// Check transactions
// Must check for duplicate inputs (see CVE-2018-17144)
for (const auto& tx : block.vtx) {
TxValidationState tx_state;
if (!CheckTransaction(*tx, tx_state)) {
// CheckBlock() does context-free validation checks. The only
// possible failures are consensus failures.
assert(tx_state.GetResult() == TxValidationResult::TX_CONSENSUS);
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, tx_state.GetRejectReason(),
strprintf("Transaction check failed (tx hash %s) %s", tx->GetHash().ToString(), tx_state.GetDebugMessage()));
}
}
unsigned int nSigOps = 0;
for (const auto& tx : block.vtx)
{
nSigOps += GetLegacySigOpCount(*tx);
}
if (nSigOps * WITNESS_SCALE_FACTOR > MAX_BLOCK_SIGOPS_COST)
return state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "bad-blk-sigops", "out-of-bounds SigOpCount");
if (fCheckPOW && fCheckMerkleRoot)
block.fChecked = true;
return true;
}Last updated