// calcPriority returns a transaction priority given a transaction and the sum
// of each of its input values multiplied by their age (# of confirmations).
// Thus, the final formula for the priority is:
// sum(inputValue * inputAge) / adjustedTxSize
func calcPriority(tx *btcutil.Tx, serializedTxSize int, inputValueAge float64) float64 {
// In order to encourage spending multiple old unspent transaction
// outputs thereby reducing the total set, don't count the constant
// overhead for each input as well as enough bytes of the signature
// script to cover a pay-to-script-hash redemption with a compressed
// pubkey. This makes additional inputs free by boosting the priority
// of the transaction accordingly. No more incentive is given to avoid
// encouraging gaming future transactions through the use of junk
// outputs. This is the same logic used in the reference
// implementation.
//
// The constant overhead for a txin is 41 bytes since the previous
// outpoint is 36 bytes + 4 bytes for the sequence + 1 byte the
// signature script length.
//
// A compressed pubkey pay-to-script-hash redemption with a maximum len
// signature is of the form:
// [OP_DATA_73 <73-byte sig> + OP_DATA_35 + {OP_DATA_33
// <33 byte compresed pubkey> + OP_CHECKSIG}]
//
// Thus 1 + 73 + 1 + 1 + 33 + 1 = 110
overhead := 0
for _, txIn := range tx.MsgTx().TxIn {
// Max inputs + size can't possibly overflow here.
overhead += 41 + minInt(110, len(txIn.SignatureScript))
}
if overhead >= serializedTxSize {
return 0.0
}
return inputValueAge / float64(serializedTxSize-overhead)
}
// checkSerializedHeight checks if the signature script in the passed
// transaction starts with the serialized block height of wantHeight.
func checkSerializedHeight(coinbaseTx *btcutil.Tx, wantHeight int64) 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 ruleError(ErrMissingCoinbaseHeight, str)
}
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 ruleError(ErrMissingCoinbaseHeight, str)
}
serializedHeightBytes := make([]byte, 8, 8)
copy(serializedHeightBytes, sigScript[1:serializedLen+1])
serializedHeight := binary.LittleEndian.Uint64(serializedHeightBytes)
if int64(serializedHeight) != wantHeight {
str := fmt.Sprintf("the coinbase signature script serialized "+
"block height is %d when %d was expected",
serializedHeight, wantHeight)
return ruleError(ErrBadCoinbaseHeight, str)
}
return nil
}
// IsFinalizedTransaction determines whether or not a transaction is finalized.
func IsFinalizedTransaction(tx *btcutil.Tx, blockHeight int64, 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 lockTimeThreshold. When it is under the
// threshold it is a block height.
blockTimeOrHeight := int64(0)
if lockTime < lockTimeThreshold {
blockTimeOrHeight = blockHeight
} else {
blockTimeOrHeight = blockTime.Unix()
}
if int64(lockTime) < blockTimeOrHeight {
return true
}
// At this point, the transaction's lock time hasn't occured 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
}
// ValidateTransactionScripts validates the scripts for the passed transaction
// using multiple goroutines.
func ValidateTransactionScripts(tx *btcutil.Tx, txStore TxStore, flags txscript.ScriptFlags) error {
// 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,
}
txValItems = append(txValItems, txVI)
}
// Validate all of the inputs.
validator := newTxValidator(txStore, flags)
if err := validator.Validate(txValItems); err != nil {
return err
}
return nil
}
// logSkippedDeps logs any dependencies which are also skipped as a result of
// skipping a transaction while generating a block template at the trace level.
func logSkippedDeps(tx *btcutil.Tx, deps *list.List) {
if deps == nil {
return
}
for e := deps.Front(); e != nil; e = e.Next() {
item := e.Value.(*txPrioItem)
minrLog.Tracef("Skipping tx %s since it depends on %s\n",
item.tx.Sha(), tx.Sha())
}
}
// isNonstandardTransaction determines whether a transaction contains any
// scripts which are not one of the standard types.
func isNonstandardTransaction(tx *btcutil.Tx) bool {
// TODO(davec): Should there be checks for the input signature scripts?
// 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
}
// 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 *txMemPool) 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.Sha())
return txRuleError(btcwire.RejectDuplicate, str)
}
}
return nil
}
// 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 *txMemPool) RemoveDoubleSpends(tx *btcutil.Tx) {
// Protect concurrent access.
mp.Lock()
defer mp.Unlock()
for _, txIn := range tx.MsgTx().TxIn {
if txRedeemer, ok := mp.outpoints[txIn.PreviousOutPoint]; ok {
if !txRedeemer.Sha().IsEqual(tx.Sha()) {
mp.removeTransaction(txRedeemer)
}
}
}
}
// 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 *txMemPool) addTransaction(tx *btcutil.Tx, height, fee int64) {
// Add the transaction to the pool and mark the referenced outpoints
// as spent by the pool.
mp.pool[*tx.Sha()] = &TxDesc{
Tx: tx,
Added: time.Now(),
Height: height,
Fee: fee,
}
for _, txIn := range tx.MsgTx().TxIn {
mp.outpoints[txIn.PreviousOutPoint] = tx
}
mp.lastUpdated = time.Now()
}
// 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.
func IsCoinBase(tx *btcutil.Tx) bool {
msgTx := tx.MsgTx()
// A coin base must only have one transaction input.
if len(msgTx.TxIn) != 1 {
return false
}
// The previous output of a coin base must have a max value index and
// a zero hash.
prevOut := msgTx.TxIn[0].PreviousOutPoint
if prevOut.Index != math.MaxUint32 || !prevOut.Hash.IsEqual(zeroHash) {
return false
}
return true
}
// FetchTransactionStore fetches 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 transaction itself so the returned TxStore can be
// examined for duplicate transactions.
func (b *BlockChain) FetchTransactionStore(tx *btcutil.Tx) (TxStore, error) {
// Create a set of needed transactions from the transactions referenced
// by the inputs of the passed transaction. Also, add the passed
// transaction itself as a way for the caller to detect duplicates.
txNeededSet := make(map[btcwire.ShaHash]struct{})
txNeededSet[*tx.Sha()] = struct{}{}
for _, txIn := range tx.MsgTx().TxIn {
txNeededSet[txIn.PreviousOutPoint.Hash] = struct{}{}
}
// Request the input transactions from the point of view of the end of
// the main chain without including fully spent trasactions in the
// results. Fully spent transactions are only needed for chain
// reorganization which does not apply here.
txStore := fetchTxStoreMain(b.db, txNeededSet, false)
return txStore, nil
}
// ProcessTransaction is the main workhorse for handling insertion of new
// free-standing transactions into the memory pool. It includes functionality
// such as rejecting duplicate transactions, ensuring transactions follow all
// rules, orphan transaction handling, and insertion into the memory pool.
//
// This function is safe for concurrent access.
func (mp *txMemPool) ProcessTransaction(tx *btcutil.Tx, allowOrphan, rateLimit bool) error {
// Protect concurrent access.
mp.Lock()
defer mp.Unlock()
txmpLog.Tracef("Processing transaction %v", tx.Sha())
// Potentially accept the transaction to the memory pool.
missingParents, err := mp.maybeAcceptTransaction(tx, true, rateLimit)
if err != nil {
return err
}
if len(missingParents) == 0 {
// Generate the inventory vector and relay it.
iv := btcwire.NewInvVect(btcwire.InvTypeTx, tx.Sha())
mp.server.RelayInventory(iv, tx)
// Accept any orphan transactions that depend on this
// transaction (they may no longer be orphans if all inputs
// are now available) and repeat for those accepted
// transactions until there are no more.
err := mp.processOrphans(tx.Sha())
if err != nil {
return err
}
} else {
// The transaction is an orphan (has inputs missing). Reject
// it if the flag to allow orphans is not set.
if !allowOrphan {
// Only use the first missing parent transaction in
// the error message.
//
// NOTE: RejectDuplicate is really not an accurate
// reject code here, but it matches the reference
// implementation and there isn't a better choice due
// to the limited number of reject codes. Missing
// inputs is assumed to mean they are already spent
// which is not really always the case.
str := fmt.Sprintf("orphan transaction %v references "+
"outputs of unknown or fully-spent "+
"transaction %v", tx.Sha(), missingParents[0])
return txRuleError(btcwire.RejectDuplicate, str)
}
// Potentially add the orphan transaction to the orphan pool.
err := mp.maybeAddOrphan(tx)
if err != nil {
return err
}
}
return nil
}
// checkInputsStandard performs a series of checks on a transaction's inputs
// to ensure they are "standard". A standard transaction input is one that
// that consumes the expected number of elements from the stack and that number
// is the same as the output script pushes. This help prevent resource
// exhaustion attacks by "creative" use of scripts that are super expensive to
// process like OP_DUP OP_CHECKSIG OP_DROP repeated a large number of times
// followed by a final OP_TRUE.
func checkInputsStandard(tx *btcutil.Tx, txStore blockchain.TxStore) 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
originTx := txStore[prevOut.Hash].Tx.MsgTx()
originPkScript := originTx.TxOut[prevOut.Index].PkScript
// Calculate stats for the script pair.
scriptInfo, err := txscript.CalcScriptInfo(txIn.SignatureScript,
originPkScript, true)
if err != nil {
str := fmt.Sprintf("transaction input #%d script parse "+
"failure: %v", i, err)
return txRuleError(btcwire.RejectNonstandard, str)
}
// A negative value for expected inputs indicates the script is
// non-standard in some way.
if scriptInfo.ExpectedInputs < 0 {
str := fmt.Sprintf("transaction input #%d expects %d "+
"inputs", i, scriptInfo.ExpectedInputs)
return txRuleError(btcwire.RejectNonstandard, str)
}
// The script pair is non-standard if the number of available
// inputs does not match the number of expected inputs.
if scriptInfo.NumInputs != scriptInfo.ExpectedInputs {
str := fmt.Sprintf("transaction input #%d expects %d "+
"inputs, but referenced output script provides "+
"%d", i, scriptInfo.ExpectedInputs,
scriptInfo.NumInputs)
return txRuleError(btcwire.RejectNonstandard, str)
}
}
return nil
}
// 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 *txMemPool) removeTransaction(tx *btcutil.Tx) {
// Remove any transactions which rely on this one.
txHash := tx.Sha()
for i := uint32(0); i < uint32(len(tx.MsgTx().TxOut)); i++ {
outpoint := btcwire.NewOutPoint(txHash, i)
if txRedeemer, exists := mp.outpoints[*outpoint]; exists {
mp.removeTransaction(txRedeemer)
}
}
// Remove the transaction and mark the referenced outpoints as unspent
// by the pool.
if txDesc, exists := mp.pool[*txHash]; exists {
for _, txIn := range txDesc.Tx.MsgTx().TxIn {
delete(mp.outpoints, txIn.PreviousOutPoint)
}
delete(mp.pool, *txHash)
mp.lastUpdated = time.Now()
}
}
// 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
}
// 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, txStore TxStore) (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 _, txIn := range msgTx.TxIn {
// Ensure the referenced input transaction is available.
txInHash := &txIn.PreviousOutPoint.Hash
originTx, exists := txStore[*txInHash]
if !exists || originTx.Err != nil || originTx.Tx == nil {
str := fmt.Sprintf("unable to find input transaction "+
"%v referenced from transaction %v", txInHash,
tx.Sha())
return 0, ruleError(ErrMissingTx, str)
}
originMsgTx := originTx.Tx.MsgTx()
// Ensure the output index in the referenced transaction is
// available.
originTxIndex := txIn.PreviousOutPoint.Index
if originTxIndex >= uint32(len(originMsgTx.TxOut)) {
str := fmt.Sprintf("out of bounds input index %d in "+
"transaction %v referenced from transaction %v",
originTxIndex, txInHash, tx.Sha())
return 0, ruleError(ErrBadTxInput, str)
}
// We're only interested in pay-to-script-hash types, so skip
// this input if it's not one.
pkScript := originMsgTx.TxOut[originTxIndex].PkScript
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 index %d in transaction %v contains "+
"too many signature operations - overflow",
originTxIndex, txInHash)
return 0, ruleError(ErrTooManySigOps, str)
}
}
return totalSigOps, nil
}
// maybeAddOrphan potentially adds an orphan to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) maybeAddOrphan(tx *btcutil.Tx) 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
// maxOrphanTxSize * maxOrphanTransactions (which is 500MB as of the
// time this comment was written).
serializedLen := tx.MsgTx().SerializeSize()
if serializedLen > maxOrphanTxSize {
str := fmt.Sprintf("orphan transaction size of %d bytes is "+
"larger than max allowed size of %d bytes",
serializedLen, maxOrphanTxSize)
return txRuleError(btcwire.RejectNonstandard, str)
}
// Add the orphan if the none of the above disqualified it.
mp.addOrphan(tx)
return nil
}
// spendTransaction updates the passed transaction store by marking the inputs
// to the passed transaction as spent. It also adds the passed transaction to
// the store at the provided height.
func spendTransaction(txStore blockchain.TxStore, tx *btcutil.Tx, height int64) error {
for _, txIn := range tx.MsgTx().TxIn {
originHash := &txIn.PreviousOutPoint.Hash
originIndex := txIn.PreviousOutPoint.Index
if originTx, exists := txStore[*originHash]; exists {
originTx.Spent[originIndex] = true
}
}
txStore[*tx.Sha()] = &blockchain.TxData{
Tx: tx,
Hash: tx.Sha(),
BlockHeight: height,
Spent: make([]bool, len(tx.MsgTx().TxOut)),
Err: nil,
}
return nil
}
// addOrphan adds an orphan transaction to the orphan pool.
//
// This function MUST be called with the mempool lock held (for writes).
func (mp *txMemPool) addOrphan(tx *btcutil.Tx) {
// Limit the number orphan transactions to prevent memory exhaustion. A
// random orphan is evicted to make room if needed.
mp.limitNumOrphans()
mp.orphans[*tx.Sha()] = tx
for _, txIn := range tx.MsgTx().TxIn {
originTxHash := txIn.PreviousOutPoint.Hash
if mp.orphansByPrev[originTxHash] == nil {
mp.orphansByPrev[originTxHash] = list.New()
}
mp.orphansByPrev[originTxHash].PushBack(tx)
}
txmpLog.Debugf("Stored orphan transaction %v (total: %d)", tx.Sha(),
len(mp.orphans))
}
// 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().SerializeSize()
if serializedTxSize > btcwire.MaxBlockPayload {
str := fmt.Sprintf("serialized transaction is too big - got "+
"%d, max %d", serializedTxSize, btcwire.MaxBlockPayload)
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)
}
// TODO(davec): No need to check < 0 here as satoshi is
// guaranteed to be positive per the above check. Also need
// to add overflow checks.
totalSatoshi += satoshi
if totalSatoshi < 0 {
str := fmt.Sprintf("total value of all transaction "+
"outputs has negative value of %v", totalSatoshi)
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[btcwire.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
}
// 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 int64) error {
msgTx := tx.MsgTx()
// The transaction must be a currently supported version.
if msgTx.Version > btcwire.TxVersion || msgTx.Version < 1 {
str := fmt.Sprintf("transaction version %d is not in the "+
"valid range of %d-%d", msgTx.Version, 1,
btcwire.TxVersion)
return txRuleError(btcwire.RejectNonstandard, str)
}
// The transaction must be finalized to be standard and therefore
// considered for inclusion in a block.
if !blockchain.IsFinalizedTransaction(tx, height, time.Now()) {
return txRuleError(btcwire.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.
serializedLen := msgTx.SerializeSize()
if serializedLen > maxStandardTxSize {
str := fmt.Sprintf("transaction size of %v is larger than max "+
"allowed size of %v", serializedLen, maxStandardTxSize)
return txRuleError(btcwire.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(btcwire.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(btcwire.RejectNonstandard, str)
}
// Each transaction input signature script must only contain
// canonical data pushes. A canonical data push is one where
// the minimum possible number of bytes is used to represent
// the data push as possible.
if !txscript.HasCanonicalPushes(txIn.SignatureScript) {
str := fmt.Sprintf("transaction input %d: signature "+
"script has a non-canonical data push", i)
return txRuleError(btcwire.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, found := extractRejectCode(err)
if !found {
rejectCode = btcwire.RejectNonstandard
}
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) {
str := fmt.Sprintf("transaction output %d: payment "+
"of %d is dust", i, txOut.Value)
return txRuleError(btcwire.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(btcwire.RejectNonstandard, str)
}
return nil
}
// 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 *txMemPool) maybeAcceptTransaction(tx *btcutil.Tx, isNew, rateLimit bool) ([]*btcwire.ShaHash, error) {
txHash := tx.Sha()
// Don't accept the transaction if it already exists in the pool. This
// applies to orphan transactions as well. This check is intended to
// be a quick check to weed out duplicates.
if mp.haveTransaction(txHash) {
str := fmt.Sprintf("already have transaction %v", txHash)
return nil, txRuleError(btcwire.RejectDuplicate, str)
}
// Perform preliminary sanity checks on the transaction. This makes
// use of btcchain 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, chainRuleError(cerr)
}
return 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, txRuleError(btcwire.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, txRuleError(btcwire.RejectNonstandard, str)
}
// Get the current height of the main chain. A standalone transaction
// will be mined into the next block at best, so it's height is at least
// one more than the current height.
_, curHeight, err := mp.server.db.NewestSha()
if err != nil {
// This is an unexpected error so don't turn it into a rule
// error.
return nil, err
}
nextBlockHeight := curHeight + 1
// Don't allow non-standard transactions if the network parameters
// forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkTransactionStandard(tx, nextBlockHeight)
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 = btcwire.RejectNonstandard
}
str := fmt.Sprintf("transaction %v is not standard: %v",
txHash, err)
return 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, err
}
// Fetch all of the transactions 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.
txStore, err := mp.fetchInputTransactions(tx)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// Don't allow the transaction if it exists in the main chain and is not
// not already fully spent.
if txD, exists := txStore[*txHash]; exists && txD.Err == nil {
for _, isOutputSpent := range txD.Spent {
if !isOutputSpent {
return nil, txRuleError(btcwire.RejectDuplicate,
"transaction already exists")
}
}
}
delete(txStore, *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 []*btcwire.ShaHash
for _, txD := range txStore {
if txD.Err == database.ErrTxShaMissing {
missingParents = append(missingParents, txD.Hash)
}
}
if len(missingParents) != 0 {
return missingParents, nil
}
// Perform several checks on the transaction inputs using the invariant
// rules in btcchain 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, txStore)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// Don't allow transactions with non-standard inputs if the network
// parameters forbid their relaying.
if !activeNetParams.RelayNonStdTxs {
err := checkInputsStandard(tx, txStore)
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 = btcwire.RejectNonstandard
}
str := fmt.Sprintf("transaction %v has a non-standard "+
"input: %v", txHash, err)
return 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.
numSigOps, err := blockchain.CountP2SHSigOps(tx, false, txStore)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
numSigOps += blockchain.CountSigOps(tx)
if numSigOps > maxSigOpsPerTx {
str := fmt.Sprintf("transaction %v has too many sigops: %d > %d",
txHash, numSigOps, maxSigOpsPerTx)
return nil, txRuleError(btcwire.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 := int64(tx.MsgTx().SerializeSize())
minFee := calcMinRequiredTxRelayFee(serializedSize)
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, txRuleError(btcwire.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()
// we decay passed data with an exponentially decaying ~10
// minutes 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 >= cfg.FreeTxRelayLimit*10*1000 {
str := fmt.Sprintf("transaction %v has been rejected "+
"by the rate limiter due to low fees", txHash)
return nil, txRuleError(btcwire.RejectInsufficientFee, str)
}
oldTotal := mp.pennyTotal
mp.pennyTotal += float64(serializedSize)
txmpLog.Tracef("rate limit: curTotal %v, nextTotal: %v, "+
"limit %v", oldTotal, mp.pennyTotal,
cfg.FreeTxRelayLimit*10*1000)
}
// Verify crypto signatures for each input and reject the transaction if
// any don't verify.
err = blockchain.ValidateTransactionScripts(tx, txStore,
standardScriptVerifyFlags)
if err != nil {
if cerr, ok := err.(blockchain.RuleError); ok {
return nil, chainRuleError(cerr)
}
return nil, err
}
// Add to transaction pool.
mp.addTransaction(tx, curHeight, txFee)
txmpLog.Debugf("Accepted transaction %v (pool size: %v)", txHash,
len(mp.pool))
if mp.server.rpcServer != nil {
// Notify websocket clients about mempool transactions.
mp.server.rpcServer.ntfnMgr.NotifyMempoolTx(tx, isNew)
// Potentially notify any getblocktemplate long poll clients
// about stale block templates due to the new transaction.
mp.server.rpcServer.gbtWorkState.NotifyMempoolTx(mp.lastUpdated)
}
return nil, nil
}
// 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.
func CheckTransactionInputs(tx *btcutil.Tx, txHeight int64, txStore TxStore) (int64, error) {
// Coinbase transactions have no inputs.
if IsCoinBase(tx) {
return 0, nil
}
txHash := tx.Sha()
var totalSatoshiIn int64
for _, txIn := range tx.MsgTx().TxIn {
// Ensure the input is available.
txInHash := &txIn.PreviousOutPoint.Hash
originTx, exists := txStore[*txInHash]
if !exists || originTx.Err != nil || originTx.Tx == nil {
str := fmt.Sprintf("unable to find input transaction "+
"%v for transaction %v", txInHash, txHash)
return 0, ruleError(ErrMissingTx, str)
}
// Ensure the transaction is not spending coins which have not
// yet reached the required coinbase maturity.
if IsCoinBase(originTx.Tx) {
originHeight := originTx.BlockHeight
blocksSincePrev := txHeight - originHeight
if blocksSincePrev < coinbaseMaturity {
str := fmt.Sprintf("tried to spend coinbase "+
"transaction %v from height %v at "+
"height %v before required maturity "+
"of %v blocks", txInHash, originHeight,
txHeight, coinbaseMaturity)
return 0, ruleError(ErrImmatureSpend, str)
}
}
// Ensure the transaction is not double spending coins.
originTxIndex := txIn.PreviousOutPoint.Index
if originTxIndex >= uint32(len(originTx.Spent)) {
str := fmt.Sprintf("out of bounds input index %d in "+
"transaction %v referenced from transaction %v",
originTxIndex, txInHash, txHash)
return 0, ruleError(ErrBadTxInput, str)
}
if originTx.Spent[originTxIndex] {
str := fmt.Sprintf("transaction %v tried to double "+
"spend output %v", txHash, 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 := originTx.Tx.MsgTx().TxOut[originTxIndex].Value
if originTxSatoshi < 0 {
str := fmt.Sprintf("transaction output has negative "+
"value of %v", 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",
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)
}
// Mark the referenced output as spent.
originTx.Spent[originTxIndex] = true
}
// 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
}
