// 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(str)
}
// The transaction must be finalized to be standard and therefore
// considered for inclusion in a block.
if !btcchain.IsFinalizedTransaction(tx, height, time.Now()) {
return TxRuleError("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(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(str)
}
// Each transaction input signature script must only contain
// opcodes which push data onto the stack.
if !btcscript.IsPushOnlyScript(txIn.SignatureScript) {
str := fmt.Sprintf("transaction input %d: signature "+
"script is not push only", i)
return TxRuleError(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 !btcscript.HasCanonicalPushes(txIn.SignatureScript) {
str := fmt.Sprintf("transaction input %d: signature "+
"script has a non-canonical data push", i)
return TxRuleError(str)
}
}
// None of the output public key scripts can be a non-standard script or
// be "dust".
numNullDataOutputs := 0
for i, txOut := range msgTx.TxOut {
scriptClass := btcscript.GetScriptClass(txOut.PkScript)
err := checkPkScriptStandard(txOut.PkScript, scriptClass)
if err != nil {
str := fmt.Sprintf("transaction output %d: %v", i, err)
return TxRuleError(str)
}
// Accumulate the number of outputs which only carry data.
if scriptClass == btcscript.NullDataTy {
numNullDataOutputs++
}
if isDust(txOut) {
str := fmt.Sprintf("transaction output %d: payment "+
"of %d is dust", i, txOut.Value)
return TxRuleError(str)
}
}
// A standard transaction must not have more than one output script that
// only carries data.
if numNullDataOutputs > 1 {
return TxRuleError("more than one transaction output is a " +
"nulldata script")
}
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 *btcwire.MsgTx, height int64) error {
// The transaction must be a currently supported version.
if tx.Version > btcwire.TxVersion || tx.Version < 1 {
str := fmt.Sprintf("transaction version %d is not in the "+
"valid range of %d-%d", tx.Version, 1,
btcwire.TxVersion)
return TxRuleError(str)
}
// The transaction must be finalized to be standard and therefore
// considered for inclusion in a block.
if !btcchain.IsFinalizedTransaction(tx, height, time.Now()) {
str := fmt.Sprintf("transaction is not finalized")
return TxRuleError(str)
}
// 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.
var serializedTxBuf bytes.Buffer
err := tx.Serialize(&serializedTxBuf)
if err != nil {
return err
}
serializedLen := serializedTxBuf.Len()
if serializedLen > maxStandardTxSize {
str := fmt.Sprintf("transaction size of %v is larger than max "+
"allowed size of %v", serializedLen, maxStandardTxSize)
return TxRuleError(str)
}
for i, txIn := range tx.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(str)
}
// Each transaction input signature script must only contain
// opcodes which push data onto the stack.
if !btcscript.IsPushOnlyScript(txIn.SignatureScript) {
str := fmt.Sprintf("transaction input %d: signature "+
"script is not push only", i)
return TxRuleError(str)
}
}
// None of the output public key scripts can be a non-standard script or
// be "dust".
for i, txOut := range tx.TxOut {
err := checkPkScriptStandard(txOut.PkScript)
if err != nil {
str := fmt.Sprintf("transaction output %d: %v", i, err)
return TxRuleError(str)
}
if isDust(txOut) {
str := fmt.Sprintf("transaction output %d: payment "+
"of %d is dust", i, txOut.Value)
return TxRuleError(str)
}
}
return nil
}