Example #1
0
// IsFinalizedTransaction determines whether or not a transaction is finalized.
func IsFinalizedTransaction(tx *btcutil.Tx, blockHeight int32, blockTime time.Time) bool {
	msgTx := tx.MsgTx()

	// Lock time of zero means the transaction is finalized.
	lockTime := msgTx.LockTime
	if lockTime == 0 {
		return true
	}

	// The lock time field of a transaction is either a block height at
	// which the transaction is finalized or a timestamp depending on if the
	// value is before the txscript.LockTimeThreshold.  When it is under the
	// threshold it is a block height.
	blockTimeOrHeight := int64(0)
	if lockTime < txscript.LockTimeThreshold {
		blockTimeOrHeight = int64(blockHeight)
	} else {
		blockTimeOrHeight = blockTime.Unix()
	}
	if int64(lockTime) < blockTimeOrHeight {
		return true
	}

	// At this point, the transaction's lock time hasn't occurred yet, but
	// the transaction might still be finalized if the sequence number
	// for all transaction inputs is maxed out.
	for _, txIn := range msgTx.TxIn {
		if txIn.Sequence != math.MaxUint32 {
			return false
		}
	}
	return true
}
Example #2
0
// addOrphan adds an orphan transaction to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) addOrphan(tx *btcutil.Tx, tag Tag) {
	// Nothing to do if no orphans are allowed.
	if mp.cfg.Policy.MaxOrphanTxs <= 0 {
		return
	}

	// Limit the number orphan transactions to prevent memory exhaustion.
	// This will periodically remove any expired orphans and evict a random
	// orphan if space is still needed.
	mp.limitNumOrphans()

	mp.orphans[*tx.Hash()] = &orphanTx{
		tx:         tx,
		tag:        tag,
		expiration: time.Now().Add(orphanTTL),
	}
	for _, txIn := range tx.MsgTx().TxIn {
		if _, exists := mp.orphansByPrev[txIn.PreviousOutPoint]; !exists {
			mp.orphansByPrev[txIn.PreviousOutPoint] =
				make(map[chainhash.Hash]*btcutil.Tx)
		}
		mp.orphansByPrev[txIn.PreviousOutPoint][*tx.Hash()] = tx
	}

	log.Debugf("Stored orphan transaction %v (total: %d)", tx.Hash(),
		len(mp.orphans))
}
Example #3
0
// removeTransaction is the internal function which implements the public
// RemoveTransaction.  See the comment for RemoveTransaction for more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) removeTransaction(tx *btcutil.Tx, removeRedeemers bool) {
	txHash := tx.Hash()
	if removeRedeemers {
		// Remove any transactions which rely on this one.
		for i := uint32(0); i < uint32(len(tx.MsgTx().TxOut)); i++ {
			prevOut := wire.OutPoint{Hash: *txHash, Index: i}
			if txRedeemer, exists := mp.outpoints[prevOut]; exists {
				mp.removeTransaction(txRedeemer, true)
			}
		}
	}

	// Remove the transaction if needed.
	if txDesc, exists := mp.pool[*txHash]; exists {
		// Remove unconfirmed address index entries associated with the
		// transaction if enabled.
		if mp.cfg.AddrIndex != nil {
			mp.cfg.AddrIndex.RemoveUnconfirmedTx(txHash)
		}

		// Mark the referenced outpoints as unspent by the pool.
		for _, txIn := range txDesc.Tx.MsgTx().TxIn {
			delete(mp.outpoints, txIn.PreviousOutPoint)
		}
		delete(mp.pool, *txHash)
		atomic.StoreInt64(&mp.lastUpdated, time.Now().Unix())
	}
}
Example #4
0
// ExtractWitnessCommitment attempts to locate, and return the witness
// commitment for a block. The witness commitment is of the form:
// SHA256(witness root || witness nonce). The function additionally returns a
// boolean indicating if the witness root was located within any of the txOut's
// in the passed transaction. The witness commitment is stored as the data push
// for an OP_RETURN with special magic bytes to aide in location.
func ExtractWitnessCommitment(tx *btcutil.Tx) ([]byte, bool) {
	var witnessCommitment []byte

	// The witness commitment *must* be located within one of the coinbase
	// transaction's outputs.
	if !IsCoinBase(tx) {
		return witnessCommitment, false
	}

	msgTx := tx.MsgTx()
	witFound := false
	for i := len(msgTx.TxOut) - 1; i >= 0; i-- {
		// The public key script that contains the witness commitment
		// must shared a prefix with the WitnessMagicBytes, and be at
		// least 38 bytes.
		pkScript := msgTx.TxOut[i].PkScript
		if len(pkScript) >= 38 &&
			bytes.HasPrefix(pkScript, WitnessMagicBytes) {

			// The witness commitment itself is a 32-byte hash
			// directly after the WitnessMagicBytes. The remaining
			// bytes beyond the 38th byte currently have no consensus
			// meaning.
			witnessCommitment = msgTx.TxOut[i].PkScript[6:38]
			witFound = true
			break
		}
	}

	return witnessCommitment, witFound
}
Example #5
0
// removeOrphanDoubleSpends removes all orphans which spend outputs spent by the
// passed transaction from the orphan pool.  Removing those orphans then leads
// to removing all orphans which rely on them, recursively.  This is necessary
// when a transaction is added to the main pool because it may spend outputs
// that orphans also spend.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) removeOrphanDoubleSpends(tx *btcutil.Tx) {
	msgTx := tx.MsgTx()
	for _, txIn := range msgTx.TxIn {
		for _, orphan := range mp.orphansByPrev[txIn.PreviousOutPoint] {
			mp.removeOrphan(orphan, true)
		}
	}
}
Example #6
0
func serializeTx(tx *btcutil.Tx) []byte {
	var buf bytes.Buffer
	err := tx.MsgTx().Serialize(&buf)
	if err != nil {
		panic(err)
	}
	return buf.Bytes()
}
Example #7
0
// GetTransactionWeight computes the value of the weight metric for a given
// transaction. Currently the weight metric is simply the sum of the
// transactions's serialized size without any witness data scaled
// proportionally by the WitnessScaleFactor, and the transaction's serialized
// size including any witness data.
func GetTransactionWeight(tx *btcutil.Tx) int64 {
	msgTx := tx.MsgTx()

	baseSize := msgTx.SerializeSizeStripped()
	totalSize := msgTx.SerializeSize()

	// (baseSize * 3) + totalSize
	return int64((baseSize * (WitnessScaleFactor - 1)) + totalSize)
}
Example #8
0
// isNonstandardTransaction determines whether a transaction contains any
// scripts which are not one of the standard types.
func isNonstandardTransaction(tx *btcutil.Tx) bool {
	// Check all of the output public key scripts for non-standard scripts.
	for _, txOut := range tx.MsgTx().TxOut {
		scriptClass := txscript.GetScriptClass(txOut.PkScript)
		if scriptClass == txscript.NonStandardTy {
			return true
		}
	}
	return false
}
Example #9
0
// RemoveDoubleSpends removes all transactions which spend outputs spent by the
// passed transaction from the memory pool.  Removing those transactions then
// leads to removing all transactions which rely on them, recursively.  This is
// necessary when a block is connected to the main chain because the block may
// contain transactions which were previously unknown to the memory pool.
//
// This function is safe for concurrent access.
func (mp *TxPool) RemoveDoubleSpends(tx *btcutil.Tx) {
	// Protect concurrent access.
	mp.mtx.Lock()
	for _, txIn := range tx.MsgTx().TxIn {
		if txRedeemer, ok := mp.outpoints[txIn.PreviousOutPoint]; ok {
			if !txRedeemer.Hash().IsEqual(tx.Hash()) {
				mp.removeTransaction(txRedeemer, true)
			}
		}
	}
	mp.mtx.Unlock()
}
Example #10
0
// checkPoolDoubleSpend checks whether or not the passed transaction is
// attempting to spend coins already spent by other transactions in the pool.
// Note it does not check for double spends against transactions already in the
// main chain.
//
// This function MUST be called with the mempool lock held (for reads).
func (mp *TxPool) checkPoolDoubleSpend(tx *btcutil.Tx) error {
	for _, txIn := range tx.MsgTx().TxIn {
		if txR, exists := mp.outpoints[txIn.PreviousOutPoint]; exists {
			str := fmt.Sprintf("output %v already spent by "+
				"transaction %v in the memory pool",
				txIn.PreviousOutPoint, txR.Hash())
			return txRuleError(wire.RejectDuplicate, str)
		}
	}

	return nil
}
Example #11
0
// spendTransaction updates the passed view by marking the inputs to the passed
// transaction as spent.  It also adds all outputs in the passed transaction
// which are not provably unspendable as available unspent transaction outputs.
func spendTransaction(utxoView *blockchain.UtxoViewpoint, tx *btcutil.Tx, height int32) error {
	for _, txIn := range tx.MsgTx().TxIn {
		originHash := &txIn.PreviousOutPoint.Hash
		originIndex := txIn.PreviousOutPoint.Index
		entry := utxoView.LookupEntry(originHash)
		if entry != nil {
			entry.SpendOutput(originIndex)
		}
	}

	utxoView.AddTxOuts(tx, height)
	return nil
}
Example #12
0
// connectTransaction updates the view by adding all new utxos created by the
// passed transaction and marking all utxos that the transactions spend as
// spent.  In addition, when the 'stxos' argument is not nil, it will be updated
// to append an entry for each spent txout.  An error will be returned if the
// view does not contain the required utxos.
func (view *UtxoViewpoint) connectTransaction(tx *btcutil.Tx, blockHeight int32, stxos *[]spentTxOut) error {
	// Coinbase transactions don't have any inputs to spend.
	if IsCoinBase(tx) {
		// Add the transaction's outputs as available utxos.
		view.AddTxOuts(tx, blockHeight)
		return nil
	}

	// Spend the referenced utxos by marking them spent in the view and,
	// if a slice was provided for the spent txout details, append an entry
	// to it.
	for _, txIn := range tx.MsgTx().TxIn {
		originIndex := txIn.PreviousOutPoint.Index
		entry := view.entries[txIn.PreviousOutPoint.Hash]

		// Ensure the referenced utxo exists in the view.  This should
		// never happen unless there is a bug is introduced in the code.
		if entry == nil {
			return AssertError(fmt.Sprintf("view missing input %v",
				txIn.PreviousOutPoint))
		}
		entry.SpendOutput(originIndex)

		// Don't create the stxo details if not requested.
		if stxos == nil {
			continue
		}

		// Populate the stxo details using the utxo entry.  When the
		// transaction is fully spent, set the additional stxo fields
		// accordingly since those details will no longer be available
		// in the utxo set.
		var stxo = spentTxOut{
			compressed: false,
			version:    entry.Version(),
			amount:     entry.AmountByIndex(originIndex),
			pkScript:   entry.PkScriptByIndex(originIndex),
		}
		if entry.IsFullySpent() {
			stxo.height = entry.BlockHeight()
			stxo.isCoinBase = entry.IsCoinBase()
		}

		// Append the entry to the provided spent txouts slice.
		*stxos = append(*stxos, stxo)
	}

	// Add the transaction's outputs as available utxos.
	view.AddTxOuts(tx, blockHeight)
	return nil
}
Example #13
0
// CountP2SHSigOps returns the number of signature operations for all input
// transactions which are of the pay-to-script-hash type.  This uses the
// precise, signature operation counting mechanism from the script engine which
// requires access to the input transaction scripts.
func CountP2SHSigOps(tx *btcutil.Tx, isCoinBaseTx bool, utxoView *UtxoViewpoint) (int, error) {
	// Coinbase transactions have no interesting inputs.
	if isCoinBaseTx {
		return 0, nil
	}

	// Accumulate the number of signature operations in all transaction
	// inputs.
	msgTx := tx.MsgTx()
	totalSigOps := 0
	for txInIndex, txIn := range msgTx.TxIn {
		// Ensure the referenced input transaction is available.
		originTxHash := &txIn.PreviousOutPoint.Hash
		originTxIndex := txIn.PreviousOutPoint.Index
		txEntry := utxoView.LookupEntry(originTxHash)
		if txEntry == nil || txEntry.IsOutputSpent(originTxIndex) {
			str := fmt.Sprintf("unable to find unspent output "+
				"%v referenced from transaction %s:%d",
				txIn.PreviousOutPoint, tx.Hash(), txInIndex)
			return 0, ruleError(ErrMissingTx, str)
		}

		// We're only interested in pay-to-script-hash types, so skip
		// this input if it's not one.
		pkScript := txEntry.PkScriptByIndex(originTxIndex)
		if !txscript.IsPayToScriptHash(pkScript) {
			continue
		}

		// Count the precise number of signature operations in the
		// referenced public key script.
		sigScript := txIn.SignatureScript
		numSigOps := txscript.GetPreciseSigOpCount(sigScript, pkScript,
			true)

		// We could potentially overflow the accumulator so check for
		// overflow.
		lastSigOps := totalSigOps
		totalSigOps += numSigOps
		if totalSigOps < lastSigOps {
			str := fmt.Sprintf("the public key script from output "+
				"%v contains too many signature operations - "+
				"overflow", txIn.PreviousOutPoint)
			return 0, ruleError(ErrTooManySigOps, str)
		}
	}

	return totalSigOps, nil
}
Example #14
0
func (c *RPCClient) onRecvTx(tx *btcutil.Tx, block *btcjson.BlockDetails) {
	blk, err := parseBlock(block)
	if err != nil {
		// Log and drop improper notification.
		log.Errorf("recvtx notification bad block: %v", err)
		return
	}

	rec, err := wtxmgr.NewTxRecordFromMsgTx(tx.MsgTx(), time.Now())
	if err != nil {
		log.Errorf("Cannot create transaction record for relevant "+
			"tx: %v", err)
		return
	}
	select {
	case c.enqueueNotification <- RelevantTx{rec, blk}:
	case <-c.quit:
	}
}
Example #15
0
// AddTxOuts adds all outputs in the passed transaction which are not provably
// unspendable to the view.  When the view already has entries for any of the
// outputs, they are simply marked unspent.  All fields will be updated for
// existing entries since it's possible it has changed during a reorg.
func (view *UtxoViewpoint) AddTxOuts(tx *btcutil.Tx, blockHeight int32) {
	// When there are not already any utxos associated with the transaction,
	// add a new entry for it to the view.
	entry := view.LookupEntry(tx.Hash())
	if entry == nil {
		entry = newUtxoEntry(tx.MsgTx().Version, IsCoinBase(tx),
			blockHeight)
		view.entries[*tx.Hash()] = entry
	} else {
		entry.blockHeight = blockHeight
	}
	entry.modified = true

	// Loop all of the transaction outputs and add those which are not
	// provably unspendable.
	for txOutIdx, txOut := range tx.MsgTx().TxOut {
		if txscript.IsUnspendable(txOut.PkScript) {
			continue
		}

		// Update existing entries.  All fields are updated because it's
		// possible (although extremely unlikely) that the existing
		// entry is being replaced by a different transaction with the
		// same hash.  This is allowed so long as the previous
		// transaction is fully spent.
		if output, ok := entry.sparseOutputs[uint32(txOutIdx)]; ok {
			output.spent = false
			output.compressed = false
			output.amount = txOut.Value
			output.pkScript = txOut.PkScript
			continue
		}

		// Add the unspent transaction output.
		entry.sparseOutputs[uint32(txOutIdx)] = &utxoOutput{
			spent:      false,
			compressed: false,
			amount:     txOut.Value,
			pkScript:   txOut.PkScript,
		}
	}
	return
}
Example #16
0
// CountSigOps returns the number of signature operations for all transaction
// input and output scripts in the provided transaction.  This uses the
// quicker, but imprecise, signature operation counting mechanism from
// txscript.
func CountSigOps(tx *btcutil.Tx) int {
	msgTx := tx.MsgTx()

	// Accumulate the number of signature operations in all transaction
	// inputs.
	totalSigOps := 0
	for _, txIn := range msgTx.TxIn {
		numSigOps := txscript.GetSigOpCount(txIn.SignatureScript)
		totalSigOps += numSigOps
	}

	// Accumulate the number of signature operations in all transaction
	// outputs.
	for _, txOut := range msgTx.TxOut {
		numSigOps := txscript.GetSigOpCount(txOut.PkScript)
		totalSigOps += numSigOps
	}

	return totalSigOps
}
Example #17
0
// addTransaction adds the passed transaction to the memory pool.  It should
// not be called directly as it doesn't perform any validation.  This is a
// helper for maybeAcceptTransaction.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) addTransaction(utxoView *blockchain.UtxoViewpoint, tx *btcutil.Tx, height int32, fee int64) *TxDesc {
	// Add the transaction to the pool and mark the referenced outpoints
	// as spent by the pool.
	txD := &TxDesc{
		TxDesc: mining.TxDesc{
			Tx:       tx,
			Added:    time.Now(),
			Height:   height,
			Fee:      fee,
			FeePerKB: fee * 1000 / int64(tx.MsgTx().SerializeSize()),
		},
		StartingPriority: mining.CalcPriority(tx.MsgTx(), utxoView, height),
	}
	mp.pool[*tx.Hash()] = txD

	for _, txIn := range tx.MsgTx().TxIn {
		mp.outpoints[txIn.PreviousOutPoint] = tx
	}
	atomic.StoreInt64(&mp.lastUpdated, time.Now().Unix())

	// Add unconfirmed address index entries associated with the transaction
	// if enabled.
	if mp.cfg.AddrIndex != nil {
		mp.cfg.AddrIndex.AddUnconfirmedTx(tx, utxoView)
	}

	return txD
}
Example #18
0
// ValidateTransactionScripts validates the scripts for the passed transaction
// using multiple goroutines.
func ValidateTransactionScripts(tx *btcutil.Tx, utxoView *UtxoViewpoint,
	flags txscript.ScriptFlags, sigCache *txscript.SigCache,
	hashCache *txscript.HashCache) error {

	// If the hashcache doesn't yet has the sighash midstate for this
	// transaction, then we'll compute them now so we can re-use them
	// amongst all worker validation goroutines.
	if !hashCache.ContainsHashes(tx.Hash()) {
		hashCache.AddSigHashes(tx.MsgTx())
	}

	// The same pointer to the transaction's sighash midstate will be
	// re-used amongst all validation goroutines. By pre-computing the
	// sighash here instead of during validation, we ensure the sighashes
	// are only computed once.
	cachedHashes, _ := hashCache.GetSigHashes(tx.Hash())

	// Collect all of the transaction inputs and required information for
	// validation.
	txIns := tx.MsgTx().TxIn
	txValItems := make([]*txValidateItem, 0, len(txIns))
	for txInIdx, txIn := range txIns {
		// Skip coinbases.
		if txIn.PreviousOutPoint.Index == math.MaxUint32 {
			continue
		}

		txVI := &txValidateItem{
			txInIndex: txInIdx,
			txIn:      txIn,
			tx:        tx,
			sigHashes: cachedHashes,
		}
		txValItems = append(txValItems, txVI)
	}

	// Validate all of the inputs.
	validator := newTxValidator(utxoView, flags, sigCache, hashCache)
	return validator.Validate(txValItems)
}
Example #19
0
// checkInputsStandard performs a series of checks on a transaction's inputs
// to ensure they are "standard".  A standard transaction input within the
// context of this function is one whose referenced public key script is of a
// standard form and, for pay-to-script-hash, does not have more than
// maxStandardP2SHSigOps signature operations.  However, it should also be noted
// that standard inputs also are those which have a clean stack after execution
// and only contain pushed data in their signature scripts.  This function does
// not perform those checks because the script engine already does this more
// accurately and concisely via the txscript.ScriptVerifyCleanStack and
// txscript.ScriptVerifySigPushOnly flags.
func checkInputsStandard(tx *btcutil.Tx, utxoView *blockchain.UtxoViewpoint) error {
	// NOTE: The reference implementation also does a coinbase check here,
	// but coinbases have already been rejected prior to calling this
	// function so no need to recheck.

	for i, txIn := range tx.MsgTx().TxIn {
		// It is safe to elide existence and index checks here since
		// they have already been checked prior to calling this
		// function.
		prevOut := txIn.PreviousOutPoint
		entry := utxoView.LookupEntry(&prevOut.Hash)
		originPkScript := entry.PkScriptByIndex(prevOut.Index)
		switch txscript.GetScriptClass(originPkScript) {
		case txscript.NonStandardTy:
			str := fmt.Sprintf("transaction input #%d has a "+
				"non-standard script form", i)
			return txRuleError(wire.RejectNonstandard, str)
		}
	}

	return nil
}
Example #20
0
// FetchUtxoView loads utxo details about the input transactions referenced by
// the passed transaction from the point of view of the end of the main chain.
// It also attempts to fetch the utxo details for the transaction itself so the
// returned view can be examined for duplicate unspent transaction outputs.
//
// This function is safe for concurrent access however the returned view is NOT.
func (b *BlockChain) FetchUtxoView(tx *btcutil.Tx) (*UtxoViewpoint, error) {
	b.chainLock.RLock()
	defer b.chainLock.RUnlock()

	// Create a set of needed transactions based on those referenced by the
	// inputs of the passed transaction.  Also, add the passed transaction
	// itself as a way for the caller to detect duplicates that are not
	// fully spent.
	txNeededSet := make(map[chainhash.Hash]struct{})
	txNeededSet[*tx.Hash()] = struct{}{}
	if !IsCoinBase(tx) {
		for _, txIn := range tx.MsgTx().TxIn {
			txNeededSet[txIn.PreviousOutPoint.Hash] = struct{}{}
		}
	}

	// Request the utxos from the point of view of the end of the main
	// chain.
	view := NewUtxoViewpoint()
	err := view.fetchUtxosMain(b.db, txNeededSet)
	return view, err
}
Example #21
0
// AddUnconfirmedTx adds all addresses related to the transaction to the
// unconfirmed (memory-only) address index.
//
// NOTE: This transaction MUST have already been validated by the memory pool
// before calling this function with it and have all of the inputs available in
// the provided utxo view.  Failure to do so could result in some or all
// addresses not being indexed.
//
// This function is safe for concurrent access.
func (idx *AddrIndex) AddUnconfirmedTx(tx *btcutil.Tx, utxoView *blockchain.UtxoViewpoint) {
	// Index addresses of all referenced previous transaction outputs.
	//
	// The existence checks are elided since this is only called after the
	// transaction has already been validated and thus all inputs are
	// already known to exist.
	for _, txIn := range tx.MsgTx().TxIn {
		entry := utxoView.LookupEntry(&txIn.PreviousOutPoint.Hash)
		if entry == nil {
			// Ignore missing entries.  This should never happen
			// in practice since the function comments specifically
			// call out all inputs must be available.
			continue
		}
		pkScript := entry.PkScriptByIndex(txIn.PreviousOutPoint.Index)
		idx.indexUnconfirmedAddresses(pkScript, tx)
	}

	// Index addresses of all created outputs.
	for _, txOut := range tx.MsgTx().TxOut {
		idx.indexUnconfirmedAddresses(txOut.PkScript, tx)
	}
}
Example #22
0
// GetSigOpCost returns the unified sig op cost for the passed transaction
// respecting current active soft-forks which modified sig op cost counting.
// The unified sig op cost for a transaction is computed as the sum of: the
// legacy sig op count scaled according to the WitnessScaleFactor, the sig op
// count for all p2sh inputs scaled by the WitnessScaleFactor, and finally the
// unscaled sig op count for any inputs spending witness programs.
func GetSigOpCost(tx *btcutil.Tx, isCoinBaseTx bool, utxoView *UtxoViewpoint,
	bip16, segWit bool) (int, error) {

	numSigOps := CountSigOps(tx) * WitnessScaleFactor
	if bip16 {
		numP2SHSigOps, err := CountP2SHSigOps(tx, isCoinBaseTx, utxoView)
		if err != nil {
			return 0, nil
		}
		numSigOps += (numP2SHSigOps * WitnessScaleFactor)
	}

	if segWit && !isCoinBaseTx {
		msgTx := tx.MsgTx()
		for txInIndex, txIn := range msgTx.TxIn {
			// Ensure the referenced input transaction is available.
			originTxHash := &txIn.PreviousOutPoint.Hash
			originTxIndex := txIn.PreviousOutPoint.Index
			txEntry := utxoView.LookupEntry(originTxHash)
			if txEntry == nil || txEntry.IsOutputSpent(originTxIndex) {
				str := fmt.Sprintf("unable to find unspent output "+
					"%v referenced from transaction %s:%d",
					txIn.PreviousOutPoint, tx.Hash(), txInIndex)
				return 0, ruleError(ErrMissingTx, str)
			}

			witness := txIn.Witness
			sigScript := txIn.SignatureScript
			pkScript := txEntry.PkScriptByIndex(originTxIndex)

			numSigOps += txscript.GetWitnessSigOpCount(sigScript, pkScript, witness)
		}

	}

	return numSigOps, nil
}
Example #23
0
// ExtractCoinbaseHeight attempts to extract the height of the block from the
// scriptSig of a coinbase transaction.  Coinbase heights are only present in
// blocks of version 2 or later.  This was added as part of BIP0034.
func ExtractCoinbaseHeight(coinbaseTx *btcutil.Tx) (int32, error) {
	sigScript := coinbaseTx.MsgTx().TxIn[0].SignatureScript
	if len(sigScript) < 1 {
		str := "the coinbase signature script for blocks of " +
			"version %d or greater must start with the " +
			"length of the serialized block height"
		str = fmt.Sprintf(str, serializedHeightVersion)
		return 0, ruleError(ErrMissingCoinbaseHeight, str)
	}

	// Detect the case when the block height is a small integer encoded with
	// as single byte.
	opcode := int(sigScript[0])
	if opcode == txscript.OP_0 {
		return 0, nil
	}
	if opcode >= txscript.OP_1 && opcode <= txscript.OP_16 {
		return int32(opcode - (txscript.OP_1 - 1)), nil
	}

	// Otherwise, the opcode is the length of the following bytes which
	// encode in the block height.
	serializedLen := int(sigScript[0])
	if len(sigScript[1:]) < serializedLen {
		str := "the coinbase signature script for blocks of " +
			"version %d or greater must start with the " +
			"serialized block height"
		str = fmt.Sprintf(str, serializedLen)
		return 0, ruleError(ErrMissingCoinbaseHeight, str)
	}

	serializedHeightBytes := make([]byte, 8, 8)
	copy(serializedHeightBytes, sigScript[1:serializedLen+1])
	serializedHeight := binary.LittleEndian.Uint64(serializedHeightBytes)

	return int32(serializedHeight), nil
}
Example #24
0
// maybeAddOrphan potentially adds an orphan to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) maybeAddOrphan(tx *btcutil.Tx, tag Tag) error {
	// Ignore orphan transactions that are too large.  This helps avoid
	// a memory exhaustion attack based on sending a lot of really large
	// orphans.  In the case there is a valid transaction larger than this,
	// it will ultimtely be rebroadcast after the parent transactions
	// have been mined or otherwise received.
	//
	// Note that the number of orphan transactions in the orphan pool is
	// also limited, so this equates to a maximum memory used of
	// mp.cfg.Policy.MaxOrphanTxSize * mp.cfg.Policy.MaxOrphanTxs (which is ~5MB
	// using the default values at the time this comment was written).
	serializedLen := tx.MsgTx().SerializeSize()
	if serializedLen > mp.cfg.Policy.MaxOrphanTxSize {
		str := fmt.Sprintf("orphan transaction size of %d bytes is "+
			"larger than max allowed size of %d bytes",
			serializedLen, mp.cfg.Policy.MaxOrphanTxSize)
		return txRuleError(wire.RejectNonstandard, str)
	}

	// Add the orphan if the none of the above disqualified it.
	mp.addOrphan(tx, tag)

	return nil
}
Example #25
0
// removeOrphan is the internal function which implements the public
// RemoveOrphan.  See the comment for RemoveOrphan for more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) removeOrphan(tx *btcutil.Tx, removeRedeemers bool) {
	// Nothing to do if passed tx is not an orphan.
	txHash := tx.Hash()
	otx, exists := mp.orphans[*txHash]
	if !exists {
		return
	}

	// Remove the reference from the previous orphan index.
	for _, txIn := range otx.tx.MsgTx().TxIn {
		orphans, exists := mp.orphansByPrev[txIn.PreviousOutPoint]
		if exists {
			delete(orphans, *txHash)

			// Remove the map entry altogether if there are no
			// longer any orphans which depend on it.
			if len(orphans) == 0 {
				delete(mp.orphansByPrev, txIn.PreviousOutPoint)
			}
		}
	}

	// Remove any orphans that redeem outputs from this one if requested.
	if removeRedeemers {
		prevOut := wire.OutPoint{Hash: *txHash}
		for txOutIdx := range tx.MsgTx().TxOut {
			prevOut.Index = uint32(txOutIdx)
			for _, orphan := range mp.orphansByPrev[prevOut] {
				mp.removeOrphan(orphan, true)
			}
		}
	}

	// Remove the transaction from the orphan pool.
	delete(mp.orphans, *txHash)
}
Example #26
0
// checkTransactionStandard performs a series of checks on a transaction to
// ensure it is a "standard" transaction.  A standard transaction is one that
// conforms to several additional limiting cases over what is considered a
// "sane" transaction such as having a version in the supported range, being
// finalized, conforming to more stringent size constraints, having scripts
// of recognized forms, and not containing "dust" outputs (those that are
// so small it costs more to process them than they are worth).
func checkTransactionStandard(tx *btcutil.Tx, height int32,
	medianTimePast time.Time, minRelayTxFee btcutil.Amount,
	maxTxVersion int32) error {

	// The transaction must be a currently supported version.
	msgTx := tx.MsgTx()
	if msgTx.Version > maxTxVersion || msgTx.Version < 1 {
		str := fmt.Sprintf("transaction version %d is not in the "+
			"valid range of %d-%d", msgTx.Version, 1,
			maxTxVersion)
		return txRuleError(wire.RejectNonstandard, str)
	}

	// The transaction must be finalized to be standard and therefore
	// considered for inclusion in a block.
	if !blockchain.IsFinalizedTransaction(tx, height, medianTimePast) {
		return txRuleError(wire.RejectNonstandard,
			"transaction is not finalized")
	}

	// Since extremely large transactions with a lot of inputs can cost
	// almost as much to process as the sender fees, limit the maximum
	// size of a transaction.  This also helps mitigate CPU exhaustion
	// attacks.
	txWeight := blockchain.GetTransactionWeight(tx)
	if txWeight > maxStandardTxWeight {
		str := fmt.Sprintf("weight of transaction %v is larger than max "+
			"allowed weight of %v", txWeight, maxStandardTxWeight)
		return txRuleError(wire.RejectNonstandard, str)
	}

	for i, txIn := range msgTx.TxIn {
		// Each transaction input signature script must not exceed the
		// maximum size allowed for a standard transaction.  See
		// the comment on maxStandardSigScriptSize for more details.
		sigScriptLen := len(txIn.SignatureScript)
		if sigScriptLen > maxStandardSigScriptSize {
			str := fmt.Sprintf("transaction input %d: signature "+
				"script size of %d bytes is large than max "+
				"allowed size of %d bytes", i, sigScriptLen,
				maxStandardSigScriptSize)
			return txRuleError(wire.RejectNonstandard, str)
		}

		// Each transaction input signature script must only contain
		// opcodes which push data onto the stack.
		if !txscript.IsPushOnlyScript(txIn.SignatureScript) {
			str := fmt.Sprintf("transaction input %d: signature "+
				"script is not push only", i)
			return txRuleError(wire.RejectNonstandard, str)
		}
	}

	// None of the output public key scripts can be a non-standard script or
	// be "dust" (except when the script is a null data script).
	numNullDataOutputs := 0
	for i, txOut := range msgTx.TxOut {
		scriptClass := txscript.GetScriptClass(txOut.PkScript)
		err := checkPkScriptStandard(txOut.PkScript, scriptClass)
		if err != nil {
			// Attempt to extract a reject code from the error so
			// it can be retained.  When not possible, fall back to
			// a non standard error.
			rejectCode := wire.RejectNonstandard
			if rejCode, found := extractRejectCode(err); found {
				rejectCode = rejCode
			}
			str := fmt.Sprintf("transaction output %d: %v", i, err)
			return txRuleError(rejectCode, str)
		}

		// Accumulate the number of outputs which only carry data.  For
		// all other script types, ensure the output value is not
		// "dust".
		if scriptClass == txscript.NullDataTy {
			numNullDataOutputs++
		} else if isDust(txOut, minRelayTxFee) {
			str := fmt.Sprintf("transaction output %d: payment "+
				"of %d is dust", i, txOut.Value)
			return txRuleError(wire.RejectDust, str)
		}
	}

	// A standard transaction must not have more than one output script that
	// only carries data.
	if numNullDataOutputs > 1 {
		str := "more than one transaction output in a nulldata script"
		return txRuleError(wire.RejectNonstandard, str)
	}

	return nil
}
Example #27
0
// IsCoinBase determines whether or not a transaction is a coinbase.  A coinbase
// is a special transaction created by miners that has no inputs.  This is
// represented in the block chain by a transaction with a single input that has
// a previous output transaction index set to the maximum value along with a
// zero hash.
//
// This function only differs from IsCoinBaseTx in that it works with a higher
// level util transaction as opposed to a raw wire transaction.
func IsCoinBase(tx *btcutil.Tx) bool {
	return IsCoinBaseTx(tx.MsgTx())
}
Example #28
0
// CheckTransactionInputs performs a series of checks on the inputs to a
// transaction to ensure they are valid.  An example of some of the checks
// include verifying all inputs exist, ensuring the coinbase seasoning
// requirements are met, detecting double spends, validating all values and fees
// are in the legal range and the total output amount doesn't exceed the input
// amount, and verifying the signatures to prove the spender was the owner of
// the bitcoins and therefore allowed to spend them.  As it checks the inputs,
// it also calculates the total fees for the transaction and returns that value.
//
// NOTE: The transaction MUST have already been sanity checked with the
// CheckTransactionSanity function prior to calling this function.
func CheckTransactionInputs(tx *btcutil.Tx, txHeight int32, utxoView *UtxoViewpoint, chainParams *chaincfg.Params) (int64, error) {
	// Coinbase transactions have no inputs.
	if IsCoinBase(tx) {
		return 0, nil
	}

	txHash := tx.Hash()
	var totalSatoshiIn int64
	for txInIndex, txIn := range tx.MsgTx().TxIn {
		// Ensure the referenced input transaction is available.
		originTxHash := &txIn.PreviousOutPoint.Hash
		utxoEntry := utxoView.LookupEntry(originTxHash)
		if utxoEntry == nil {
			str := fmt.Sprintf("unable to find unspent output "+
				"%v referenced from transaction %s:%d",
				txIn.PreviousOutPoint, tx.Hash(), txInIndex)
			return 0, ruleError(ErrMissingTx, str)
		}

		// Ensure the transaction is not spending coins which have not
		// yet reached the required coinbase maturity.
		if utxoEntry.IsCoinBase() {
			originHeight := utxoEntry.BlockHeight()
			blocksSincePrev := txHeight - originHeight
			coinbaseMaturity := int32(chainParams.CoinbaseMaturity)
			if blocksSincePrev < coinbaseMaturity {
				str := fmt.Sprintf("tried to spend coinbase "+
					"transaction %v from height %v at "+
					"height %v before required maturity "+
					"of %v blocks", originTxHash,
					originHeight, txHeight,
					coinbaseMaturity)
				return 0, ruleError(ErrImmatureSpend, str)
			}
		}

		// Ensure the transaction is not double spending coins.
		originTxIndex := txIn.PreviousOutPoint.Index
		if utxoEntry.IsOutputSpent(originTxIndex) {
			str := fmt.Sprintf("transaction %s:%d tried to double "+
				"spend output %v", txHash, txInIndex,
				txIn.PreviousOutPoint)
			return 0, ruleError(ErrDoubleSpend, str)
		}

		// Ensure the transaction amounts are in range.  Each of the
		// output values of the input transactions must not be negative
		// or more than the max allowed per transaction.  All amounts in
		// a transaction are in a unit value known as a satoshi.  One
		// bitcoin is a quantity of satoshi as defined by the
		// SatoshiPerBitcoin constant.
		originTxSatoshi := utxoEntry.AmountByIndex(originTxIndex)
		if originTxSatoshi < 0 {
			str := fmt.Sprintf("transaction output has negative "+
				"value of %v", btcutil.Amount(originTxSatoshi))
			return 0, ruleError(ErrBadTxOutValue, str)
		}
		if originTxSatoshi > btcutil.MaxSatoshi {
			str := fmt.Sprintf("transaction output value of %v is "+
				"higher than max allowed value of %v",
				btcutil.Amount(originTxSatoshi),
				btcutil.MaxSatoshi)
			return 0, ruleError(ErrBadTxOutValue, str)
		}

		// The total of all outputs must not be more than the max
		// allowed per transaction.  Also, we could potentially overflow
		// the accumulator so check for overflow.
		lastSatoshiIn := totalSatoshiIn
		totalSatoshiIn += originTxSatoshi
		if totalSatoshiIn < lastSatoshiIn ||
			totalSatoshiIn > btcutil.MaxSatoshi {
			str := fmt.Sprintf("total value of all transaction "+
				"inputs is %v which is higher than max "+
				"allowed value of %v", totalSatoshiIn,
				btcutil.MaxSatoshi)
			return 0, ruleError(ErrBadTxOutValue, str)
		}
	}

	// Calculate the total output amount for this transaction.  It is safe
	// to ignore overflow and out of range errors here because those error
	// conditions would have already been caught by checkTransactionSanity.
	var totalSatoshiOut int64
	for _, txOut := range tx.MsgTx().TxOut {
		totalSatoshiOut += txOut.Value
	}

	// Ensure the transaction does not spend more than its inputs.
	if totalSatoshiIn < totalSatoshiOut {
		str := fmt.Sprintf("total value of all transaction inputs for "+
			"transaction %v is %v which is less than the amount "+
			"spent of %v", txHash, totalSatoshiIn, totalSatoshiOut)
		return 0, ruleError(ErrSpendTooHigh, str)
	}

	// NOTE: bitcoind checks if the transaction fees are < 0 here, but that
	// is an impossible condition because of the check above that ensures
	// the inputs are >= the outputs.
	txFeeInSatoshi := totalSatoshiIn - totalSatoshiOut
	return txFeeInSatoshi, nil
}
Example #29
0
// CheckTransactionSanity performs some preliminary checks on a transaction to
// ensure it is sane.  These checks are context free.
func CheckTransactionSanity(tx *btcutil.Tx) error {
	// A transaction must have at least one input.
	msgTx := tx.MsgTx()
	if len(msgTx.TxIn) == 0 {
		return ruleError(ErrNoTxInputs, "transaction has no inputs")
	}

	// A transaction must have at least one output.
	if len(msgTx.TxOut) == 0 {
		return ruleError(ErrNoTxOutputs, "transaction has no outputs")
	}

	// A transaction must not exceed the maximum allowed block payload when
	// serialized.
	serializedTxSize := tx.MsgTx().SerializeSizeStripped()
	if serializedTxSize > MaxBlockBaseSize {
		str := fmt.Sprintf("serialized transaction is too big - got "+
			"%d, max %d", serializedTxSize, MaxBlockBaseSize)
		return ruleError(ErrTxTooBig, str)
	}

	// Ensure the transaction amounts are in range.  Each transaction
	// output must not be negative or more than the max allowed per
	// transaction.  Also, the total of all outputs must abide by the same
	// restrictions.  All amounts in a transaction are in a unit value known
	// as a satoshi.  One bitcoin is a quantity of satoshi as defined by the
	// SatoshiPerBitcoin constant.
	var totalSatoshi int64
	for _, txOut := range msgTx.TxOut {
		satoshi := txOut.Value
		if satoshi < 0 {
			str := fmt.Sprintf("transaction output has negative "+
				"value of %v", satoshi)
			return ruleError(ErrBadTxOutValue, str)
		}
		if satoshi > btcutil.MaxSatoshi {
			str := fmt.Sprintf("transaction output value of %v is "+
				"higher than max allowed value of %v", satoshi,
				btcutil.MaxSatoshi)
			return ruleError(ErrBadTxOutValue, str)
		}

		// Two's complement int64 overflow guarantees that any overflow
		// is detected and reported.  This is impossible for Bitcoin, but
		// perhaps possible if an alt increases the total money supply.
		totalSatoshi += satoshi
		if totalSatoshi < 0 {
			str := fmt.Sprintf("total value of all transaction "+
				"outputs exceeds max allowed value of %v",
				btcutil.MaxSatoshi)
			return ruleError(ErrBadTxOutValue, str)
		}
		if totalSatoshi > btcutil.MaxSatoshi {
			str := fmt.Sprintf("total value of all transaction "+
				"outputs is %v which is higher than max "+
				"allowed value of %v", totalSatoshi,
				btcutil.MaxSatoshi)
			return ruleError(ErrBadTxOutValue, str)
		}
	}

	// Check for duplicate transaction inputs.
	existingTxOut := make(map[wire.OutPoint]struct{})
	for _, txIn := range msgTx.TxIn {
		if _, exists := existingTxOut[txIn.PreviousOutPoint]; exists {
			return ruleError(ErrDuplicateTxInputs, "transaction "+
				"contains duplicate inputs")
		}
		existingTxOut[txIn.PreviousOutPoint] = struct{}{}
	}

	// Coinbase script length must be between min and max length.
	if IsCoinBase(tx) {
		slen := len(msgTx.TxIn[0].SignatureScript)
		if slen < MinCoinbaseScriptLen || slen > MaxCoinbaseScriptLen {
			str := fmt.Sprintf("coinbase transaction script length "+
				"of %d is out of range (min: %d, max: %d)",
				slen, MinCoinbaseScriptLen, MaxCoinbaseScriptLen)
			return ruleError(ErrBadCoinbaseScriptLen, str)
		}
	} else {
		// Previous transaction outputs referenced by the inputs to this
		// transaction must not be null.
		for _, txIn := range msgTx.TxIn {
			prevOut := &txIn.PreviousOutPoint
			if isNullOutpoint(prevOut) {
				return ruleError(ErrBadTxInput, "transaction "+
					"input refers to previous output that "+
					"is null")
			}
		}
	}

	return nil
}
Example #30
0
// maybeAcceptTransaction is the internal function which implements the public
// MaybeAcceptTransaction.  See the comment for MaybeAcceptTransaction for
// more details.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *TxPool) maybeAcceptTransaction(tx *btcutil.Tx, isNew, rateLimit, rejectDupOrphans bool) ([]*chainhash.Hash, *TxDesc, error) {
	txHash := tx.Hash()

	// Don't accept the transaction if it already exists in the pool.  This
	// applies to orphan transactions as well when the reject duplicate
	// orphans flag is set.  This check is intended to be a quick check to
	// weed out duplicates.
	if mp.isTransactionInPool(txHash) || (rejectDupOrphans &&
		mp.isOrphanInPool(txHash)) {

		str := fmt.Sprintf("already have transaction %v", txHash)
		return nil, nil, txRuleError(wire.RejectDuplicate, str)
	}

	// Perform preliminary sanity checks on the transaction.  This makes
	// use of blockchain which contains the invariant rules for what
	// transactions are allowed into blocks.
	err := blockchain.CheckTransactionSanity(tx)
	if err != nil {
		if cerr, ok := err.(blockchain.RuleError); ok {
			return nil, nil, chainRuleError(cerr)
		}
		return nil, nil, err
	}

	// A standalone transaction must not be a coinbase transaction.
	if blockchain.IsCoinBase(tx) {
		str := fmt.Sprintf("transaction %v is an individual coinbase",
			txHash)
		return nil, nil, txRuleError(wire.RejectInvalid, str)
	}

	// Don't accept transactions with a lock time after the maximum int32
	// value for now.  This is an artifact of older bitcoind clients which
	// treated this field as an int32 and would treat anything larger
	// incorrectly (as negative).
	if tx.MsgTx().LockTime > math.MaxInt32 {
		str := fmt.Sprintf("transaction %v has a lock time after "+
			"2038 which is not accepted yet", txHash)
		return nil, nil, txRuleError(wire.RejectNonstandard, str)
	}

	// Get the current height of the main chain.  A standalone transaction
	// will be mined into the next block at best, so its height is at least
	// one more than the current height.
	bestHeight := mp.cfg.BestHeight()
	nextBlockHeight := bestHeight + 1

	medianTimePast := mp.cfg.MedianTimePast()

	// Don't allow non-standard transactions if the network parameters
	// forbid their acceptance.
	if !mp.cfg.Policy.AcceptNonStd {
		err = checkTransactionStandard(tx, nextBlockHeight,
			medianTimePast, mp.cfg.Policy.MinRelayTxFee,
			mp.cfg.Policy.MaxTxVersion)
		if err != nil {
			// Attempt to extract a reject code from the error so
			// it can be retained.  When not possible, fall back to
			// a non standard error.
			rejectCode, found := extractRejectCode(err)
			if !found {
				rejectCode = wire.RejectNonstandard
			}
			str := fmt.Sprintf("transaction %v is not standard: %v",
				txHash, err)
			return nil, nil, txRuleError(rejectCode, str)
		}
	}

	// The transaction may not use any of the same outputs as other
	// transactions already in the pool as that would ultimately result in a
	// double spend.  This check is intended to be quick and therefore only
	// detects double spends within the transaction pool itself.  The
	// transaction could still be double spending coins from the main chain
	// at this point.  There is a more in-depth check that happens later
	// after fetching the referenced transaction inputs from the main chain
	// which examines the actual spend data and prevents double spends.
	err = mp.checkPoolDoubleSpend(tx)
	if err != nil {
		return nil, nil, err
	}

	// Fetch all of the unspent transaction outputs referenced by the inputs
	// to this transaction.  This function also attempts to fetch the
	// transaction itself to be used for detecting a duplicate transaction
	// without needing to do a separate lookup.
	utxoView, err := mp.fetchInputUtxos(tx)
	if err != nil {
		if cerr, ok := err.(blockchain.RuleError); ok {
			return nil, nil, chainRuleError(cerr)
		}
		return nil, nil, err
	}

	// Don't allow the transaction if it exists in the main chain and is not
	// not already fully spent.
	txEntry := utxoView.LookupEntry(txHash)
	if txEntry != nil && !txEntry.IsFullySpent() {
		return nil, nil, txRuleError(wire.RejectDuplicate,
			"transaction already exists")
	}
	delete(utxoView.Entries(), *txHash)

	// Transaction is an orphan if any of the referenced input transactions
	// don't exist.  Adding orphans to the orphan pool is not handled by
	// this function, and the caller should use maybeAddOrphan if this
	// behavior is desired.
	var missingParents []*chainhash.Hash
	for originHash, entry := range utxoView.Entries() {
		if entry == nil || entry.IsFullySpent() {
			// Must make a copy of the hash here since the iterator
			// is replaced and taking its address directly would
			// result in all of the entries pointing to the same
			// memory location and thus all be the final hash.
			hashCopy := originHash
			missingParents = append(missingParents, &hashCopy)
		}
	}
	if len(missingParents) > 0 {
		return missingParents, nil, nil
	}

	// Don't allow the transaction into the mempool unless its sequence
	// lock is active, meaning that it'll be allowed into the next block
	// with respect to its defined relative lock times.
	sequenceLock, err := mp.cfg.CalcSequenceLock(tx, utxoView)
	if err != nil {
		if cerr, ok := err.(blockchain.RuleError); ok {
			return nil, nil, chainRuleError(cerr)
		}
		return nil, nil, err
	}
	if !blockchain.SequenceLockActive(sequenceLock, nextBlockHeight,
		medianTimePast) {
		return nil, nil, txRuleError(wire.RejectNonstandard,
			"transaction's sequence locks on inputs not met")
	}

	// Perform several checks on the transaction inputs using the invariant
	// rules in blockchain for what transactions are allowed into blocks.
	// Also returns the fees associated with the transaction which will be
	// used later.
	txFee, err := blockchain.CheckTransactionInputs(tx, nextBlockHeight,
		utxoView, mp.cfg.ChainParams)
	if err != nil {
		if cerr, ok := err.(blockchain.RuleError); ok {
			return nil, nil, chainRuleError(cerr)
		}
		return nil, nil, err
	}

	// Don't allow transactions with non-standard inputs if the network
	// parameters forbid their acceptance.
	if !mp.cfg.Policy.AcceptNonStd {
		err := checkInputsStandard(tx, utxoView)
		if err != nil {
			// Attempt to extract a reject code from the error so
			// it can be retained.  When not possible, fall back to
			// a non standard error.
			rejectCode, found := extractRejectCode(err)
			if !found {
				rejectCode = wire.RejectNonstandard
			}
			str := fmt.Sprintf("transaction %v has a non-standard "+
				"input: %v", txHash, err)
			return nil, nil, txRuleError(rejectCode, str)
		}
	}

	// NOTE: if you modify this code to accept non-standard transactions,
	// you should add code here to check that the transaction does a
	// reasonable number of ECDSA signature verifications.

	// Don't allow transactions with an excessive number of signature
	// operations which would result in making it impossible to mine.  Since
	// the coinbase address itself can contain signature operations, the
	// maximum allowed signature operations per transaction is less than
	// the maximum allowed signature operations per block.
	// TODO(roasbeef): last bool should be conditional on segwit activation
	sigOpCost, err := blockchain.GetSigOpCost(tx, false, utxoView, true, true)
	if err != nil {
		if cerr, ok := err.(blockchain.RuleError); ok {
			return nil, nil, chainRuleError(cerr)
		}
		return nil, nil, err
	}
	if sigOpCost > mp.cfg.Policy.MaxSigOpCostPerTx {
		str := fmt.Sprintf("transaction %v sigop cost is too high: %d > %d",
			txHash, sigOpCost, maxStandardSigOpsCost)
		return nil, nil, txRuleError(wire.RejectNonstandard, str)
	}

	// Don't allow transactions with fees too low to get into a mined block.
	//
	// Most miners allow a free transaction area in blocks they mine to go
	// alongside the area used for high-priority transactions as well as
	// transactions with fees.  A transaction size of up to 1000 bytes is
	// considered safe to go into this section.  Further, the minimum fee
	// calculated below on its own would encourage several small
	// transactions to avoid fees rather than one single larger transaction
	// which is more desirable.  Therefore, as long as the size of the
	// transaction does not exceeed 1000 less than the reserved space for
	// high-priority transactions, don't require a fee for it.
	serializedSize := blockchain.GetTxVirtualSize(tx)
	minFee := calcMinRequiredTxRelayFee(serializedSize,
		mp.cfg.Policy.MinRelayTxFee)
	if serializedSize >= (DefaultBlockPrioritySize-1000) && txFee < minFee {
		str := fmt.Sprintf("transaction %v has %d fees which is under "+
			"the required amount of %d", txHash, txFee,
			minFee)
		return nil, nil, txRuleError(wire.RejectInsufficientFee, str)
	}

	// Require that free transactions have sufficient priority to be mined
	// in the next block.  Transactions which are being added back to the
	// memory pool from blocks that have been disconnected during a reorg
	// are exempted.
	if isNew && !mp.cfg.Policy.DisableRelayPriority && txFee < minFee {
		currentPriority := mining.CalcPriority(tx.MsgTx(), utxoView,
			nextBlockHeight)
		if currentPriority <= mining.MinHighPriority {
			str := fmt.Sprintf("transaction %v has insufficient "+
				"priority (%g <= %g)", txHash,
				currentPriority, mining.MinHighPriority)
			return nil, nil, txRuleError(wire.RejectInsufficientFee, str)
		}
	}

	// Free-to-relay transactions are rate limited here to prevent
	// penny-flooding with tiny transactions as a form of attack.
	if rateLimit && txFee < minFee {
		nowUnix := time.Now().Unix()
		// Decay passed data with an exponentially decaying ~10 minute
		// window - matches bitcoind handling.
		mp.pennyTotal *= math.Pow(1.0-1.0/600.0,
			float64(nowUnix-mp.lastPennyUnix))
		mp.lastPennyUnix = nowUnix

		// Are we still over the limit?
		if mp.pennyTotal >= mp.cfg.Policy.FreeTxRelayLimit*10*1000 {
			str := fmt.Sprintf("transaction %v has been rejected "+
				"by the rate limiter due to low fees", txHash)
			return nil, nil, txRuleError(wire.RejectInsufficientFee, str)
		}
		oldTotal := mp.pennyTotal

		mp.pennyTotal += float64(serializedSize)
		log.Tracef("rate limit: curTotal %v, nextTotal: %v, "+
			"limit %v", oldTotal, mp.pennyTotal,
			mp.cfg.Policy.FreeTxRelayLimit*10*1000)
	}

	// Verify crypto signatures for each input and reject the transaction if
	// any don't verify.
	err = blockchain.ValidateTransactionScripts(tx, utxoView,
		txscript.StandardVerifyFlags, mp.cfg.SigCache,
		mp.cfg.HashCache)
	if err != nil {
		if cerr, ok := err.(blockchain.RuleError); ok {
			return nil, nil, chainRuleError(cerr)
		}
		return nil, nil, err
	}

	// Add to transaction pool.
	txD := mp.addTransaction(utxoView, tx, bestHeight, txFee)

	log.Debugf("Accepted transaction %v (pool size: %v)", txHash,
		len(mp.pool))

	return nil, txD, nil
}