MOVEONLY: tx functions to consensus/tx_verify.o

Functions related to transaction verification.

2 files changed, 324 insertions, 0 deletions

diff --git a/src/consensus/tx_verify.cpp b/src/consensus/tx_verify.cpp
new file mode 100644
index 0000000000..043f4cf95c
--- /dev/null
+++ b/src/consensus/tx_verify.cpp
@@ -0,0 +1,246 @@
+// Copyright (c) 2017-2017 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "tx_verify.h"
+
+#include "consensus.h"
+#include "primitives/transaction.h"
+#include "script/interpreter.h"
+#include "validation.h"
+
+// TODO remove the following dependencies
+#include "chain.h"
+#include "coins.h"
+#include "utilmoneystr.h"
+ 
+bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
+{
+    if (tx.nLockTime == 0)
+        return true;
+    if ((int64_t)tx.nLockTime < ((int64_t)tx.nLockTime < LOCKTIME_THRESHOLD ? (int64_t)nBlockHeight : nBlockTime))
+        return true;
+    for (const auto& txin : tx.vin) {
+        if (!(txin.nSequence == CTxIn::SEQUENCE_FINAL))
+            return false;
+    }
+    return true;
+}
+
+std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block)
+{
+    assert(prevHeights->size() == tx.vin.size());
+
+    // Will be set to the equivalent height- and time-based nLockTime
+    // values that would be necessary to satisfy all relative lock-
+    // time constraints given our view of block chain history.
+    // The semantics of nLockTime are the last invalid height/time, so
+    // use -1 to have the effect of any height or time being valid.
+    int nMinHeight = -1;
+    int64_t nMinTime = -1;
+
+    // tx.nVersion is signed integer so requires cast to unsigned otherwise
+    // we would be doing a signed comparison and half the range of nVersion
+    // wouldn't support BIP 68.
+    bool fEnforceBIP68 = static_cast<uint32_t>(tx.nVersion) >= 2
+                      && flags & LOCKTIME_VERIFY_SEQUENCE;
+
+    // Do not enforce sequence numbers as a relative lock time
+    // unless we have been instructed to
+    if (!fEnforceBIP68) {
+        return std::make_pair(nMinHeight, nMinTime);
+    }
+
+    for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
+        const CTxIn& txin = tx.vin[txinIndex];
+
+        // Sequence numbers with the most significant bit set are not
+        // treated as relative lock-times, nor are they given any
+        // consensus-enforced meaning at this point.
+        if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {
+            // The height of this input is not relevant for sequence locks
+            (*prevHeights)[txinIndex] = 0;
+            continue;
+        }
+
+        int nCoinHeight = (*prevHeights)[txinIndex];
+
+        if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) {
+            int64_t nCoinTime = block.GetAncestor(std::max(nCoinHeight-1, 0))->GetMedianTimePast();
+            // NOTE: Subtract 1 to maintain nLockTime semantics
+            // BIP 68 relative lock times have the semantics of calculating
+            // the first block or time at which the transaction would be
+            // valid. When calculating the effective block time or height
+            // for the entire transaction, we switch to using the
+            // semantics of nLockTime which is the last invalid block
+            // time or height.  Thus we subtract 1 from the calculated
+            // time or height.
+
+            // Time-based relative lock-times are measured from the
+            // smallest allowed timestamp of the block containing the
+            // txout being spent, which is the median time past of the
+            // block prior.
+            nMinTime = std::max(nMinTime, nCoinTime + (int64_t)((txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) << CTxIn::SEQUENCE_LOCKTIME_GRANULARITY) - 1);
+        } else {
+            nMinHeight = std::max(nMinHeight, nCoinHeight + (int)(txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) - 1);
+        }
+    }
+
+    return std::make_pair(nMinHeight, nMinTime);
+}
+
+bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair)
+{
+    assert(block.pprev);
+    int64_t nBlockTime = block.pprev->GetMedianTimePast();
+    if (lockPair.first >= block.nHeight || lockPair.second >= nBlockTime)
+        return false;
+
+    return true;
+}
+
+bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block)
+{
+    return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));
+}
+
+unsigned int GetLegacySigOpCount(const CTransaction& tx)
+{
+    unsigned int nSigOps = 0;
+    for (const auto& txin : tx.vin)
+    {
+        nSigOps += txin.scriptSig.GetSigOpCount(false);
+    }
+    for (const auto& txout : tx.vout)
+    {
+        nSigOps += txout.scriptPubKey.GetSigOpCount(false);
+    }
+    return nSigOps;
+}
+
+unsigned int GetP2SHSigOpCount(const CTransaction& tx, const CCoinsViewCache& inputs)
+{
+    if (tx.IsCoinBase())
+        return 0;
+
+    unsigned int nSigOps = 0;
+    for (unsigned int i = 0; i < tx.vin.size(); i++)
+    {
+        const CTxOut &prevout = inputs.GetOutputFor(tx.vin[i]);
+        if (prevout.scriptPubKey.IsPayToScriptHash())
+            nSigOps += prevout.scriptPubKey.GetSigOpCount(tx.vin[i].scriptSig);
+    }
+    return nSigOps;
+}
+
+int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& inputs, int flags)
+{
+    int64_t nSigOps = GetLegacySigOpCount(tx) * WITNESS_SCALE_FACTOR;
+
+    if (tx.IsCoinBase())
+        return nSigOps;
+
+    if (flags & SCRIPT_VERIFY_P2SH) {
+        nSigOps += GetP2SHSigOpCount(tx, inputs) * WITNESS_SCALE_FACTOR;
+    }
+
+    for (unsigned int i = 0; i < tx.vin.size(); i++)
+    {
+        const CTxOut &prevout = inputs.GetOutputFor(tx.vin[i]);
+        nSigOps += CountWitnessSigOps(tx.vin[i].scriptSig, prevout.scriptPubKey, &tx.vin[i].scriptWitness, flags);
+    }
+    return nSigOps;
+}
+
+bool CheckTransaction(const CTransaction& tx, CValidationState &state, bool fCheckDuplicateInputs)
+{
+    // Basic checks that don't depend on any context
+    if (tx.vin.empty())
+        return state.DoS(10, false, REJECT_INVALID, "bad-txns-vin-empty");
+    if (tx.vout.empty())
+        return state.DoS(10, false, REJECT_INVALID, "bad-txns-vout-empty");
+    // Size limits (this doesn't take the witness into account, as that hasn't been checked for malleability)
+    if (::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS) > MAX_BLOCK_BASE_SIZE)
+        return state.DoS(100, false, REJECT_INVALID, "bad-txns-oversize");
+
+    // Check for negative or overflow output values
+    CAmount nValueOut = 0;
+    for (const auto& txout : tx.vout)
+    {
+        if (txout.nValue < 0)
+            return state.DoS(100, false, REJECT_INVALID, "bad-txns-vout-negative");
+        if (txout.nValue > MAX_MONEY)
+            return state.DoS(100, false, REJECT_INVALID, "bad-txns-vout-toolarge");
+        nValueOut += txout.nValue;
+        if (!MoneyRange(nValueOut))
+            return state.DoS(100, false, REJECT_INVALID, "bad-txns-txouttotal-toolarge");
+    }
+
+    // Check for duplicate inputs - note that this check is slow so we skip it in CheckBlock
+    if (fCheckDuplicateInputs) {
+        std::set<COutPoint> vInOutPoints;
+        for (const auto& txin : tx.vin)
+        {
+            if (!vInOutPoints.insert(txin.prevout).second)
+                return state.DoS(100, false, REJECT_INVALID, "bad-txns-inputs-duplicate");
+        }
+    }
+
+    if (tx.IsCoinBase())
+    {
+        if (tx.vin[0].scriptSig.size() < 2 || tx.vin[0].scriptSig.size() > 100)
+            return state.DoS(100, false, REJECT_INVALID, "bad-cb-length");
+    }
+    else
+    {
+        for (const auto& txin : tx.vin)
+            if (txin.prevout.IsNull())
+                return state.DoS(10, false, REJECT_INVALID, "bad-txns-prevout-null");
+    }
+
+    return true;
+}
+
+bool Consensus::CheckTxInputs(const CTransaction& tx, CValidationState& state, const CCoinsViewCache& inputs, int nSpendHeight)
+{
+        // This doesn't trigger the DoS code on purpose; if it did, it would make it easier
+        // for an attacker to attempt to split the network.
+        if (!inputs.HaveInputs(tx))
+            return state.Invalid(false, 0, "", "Inputs unavailable");
+
+        CAmount nValueIn = 0;
+        CAmount nFees = 0;
+        for (unsigned int i = 0; i < tx.vin.size(); i++)
+        {
+            const COutPoint &prevout = tx.vin[i].prevout;
+            const CCoins *coins = inputs.AccessCoins(prevout.hash);
+            assert(coins);
+
+            // If prev is coinbase, check that it's matured
+            if (coins->IsCoinBase()) {
+                if (nSpendHeight - coins->nHeight < COINBASE_MATURITY)
+                    return state.Invalid(false,
+                        REJECT_INVALID, "bad-txns-premature-spend-of-coinbase",
+                        strprintf("tried to spend coinbase at depth %d", nSpendHeight - coins->nHeight));
+            }
+
+            // Check for negative or overflow input values
+            nValueIn += coins->vout[prevout.n].nValue;
+            if (!MoneyRange(coins->vout[prevout.n].nValue) || !MoneyRange(nValueIn))
+                return state.DoS(100, false, REJECT_INVALID, "bad-txns-inputvalues-outofrange");
+
+        }
+
+        if (nValueIn < tx.GetValueOut())
+            return state.DoS(100, false, REJECT_INVALID, "bad-txns-in-belowout", false,
+                strprintf("value in (%s) < value out (%s)", FormatMoney(nValueIn), FormatMoney(tx.GetValueOut())));
+
+        // Tally transaction fees
+        CAmount nTxFee = nValueIn - tx.GetValueOut();
+        if (nTxFee < 0)
+            return state.DoS(100, false, REJECT_INVALID, "bad-txns-fee-negative");
+        nFees += nTxFee;
+        if (!MoneyRange(nFees))
+            return state.DoS(100, false, REJECT_INVALID, "bad-txns-fee-outofrange");
+    return true;
+}
diff --git a/src/consensus/tx_verify.h b/src/consensus/tx_verify.h
new file mode 100644
index 0000000000..d46d3294ca
--- /dev/null
+++ b/src/consensus/tx_verify.h
@@ -0,0 +1,78 @@
+// Copyright (c) 2017-2017 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_CONSENSUS_TX_VERIFY_H
+#define BITCOIN_CONSENSUS_TX_VERIFY_H
+
+#include <stdint.h>
+#include <vector>
+
+class CBlockIndex;
+class CCoinsViewCache;
+class CTransaction;
+class CValidationState;
+
+/** Transaction validation functions */
+
+/** Context-independent validity checks */
+bool CheckTransaction(const CTransaction& tx, CValidationState& state, bool fCheckDuplicateInputs=true);
+
+namespace Consensus {
+/**
+ * Check whether all inputs of this transaction are valid (no double spends and amounts)
+ * This does not modify the UTXO set. This does not check scripts and sigs.
+ * Preconditions: tx.IsCoinBase() is false.
+ */
+bool CheckTxInputs(const CTransaction& tx, CValidationState& state, const CCoinsViewCache& inputs, int nSpendHeight);
+} // namespace Consensus
+
+/** Auxiliary functions for transaction validation (ideally should not be exposed) */
+
+/**
+ * Count ECDSA signature operations the old-fashioned (pre-0.6) way
+ * @return number of sigops this transaction's outputs will produce when spent
+ * @see CTransaction::FetchInputs
+ */
+unsigned int GetLegacySigOpCount(const CTransaction& tx);
+
+/**
+ * Count ECDSA signature operations in pay-to-script-hash inputs.
+ * 
+ * @param[in] mapInputs Map of previous transactions that have outputs we're spending
+ * @return maximum number of sigops required to validate this transaction's inputs
+ * @see CTransaction::FetchInputs
+ */
+unsigned int GetP2SHSigOpCount(const CTransaction& tx, const CCoinsViewCache& mapInputs);
+
+/**
+ * Compute total signature operation cost of a transaction.
+ * @param[in] tx     Transaction for which we are computing the cost
+ * @param[in] inputs Map of previous transactions that have outputs we're spending
+ * @param[out] flags Script verification flags
+ * @return Total signature operation cost of tx
+ */
+int64_t GetTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& inputs, int flags);
+
+/**
+ * Check if transaction is final and can be included in a block with the
+ * specified height and time. Consensus critical.
+ */
+bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime);
+
+/**
+ * Calculates the block height and previous block's median time past at
+ * which the transaction will be considered final in the context of BIP 68.
+ * Also removes from the vector of input heights any entries which did not
+ * correspond to sequence locked inputs as they do not affect the calculation.
+ */
+std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block);
+
+bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair);
+/**
+ * Check if transaction is final per BIP 68 sequence numbers and can be included in a block.
+ * Consensus critical. Takes as input a list of heights at which tx's inputs (in order) confirmed.
+ */
+bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block);
+
+#endif // BITCOIN_CONSENSUS_TX_VERIFY_H