// calcScriptHash will, given the a script and hashtype for the current
// scriptmachine, calculate the doubleSha256 hash of the transaction and
// script to be used for signature signing and verification.
func calcScriptHash(script []parsedOpcode, hashType byte, tx *btcwire.MsgTx, idx int) []byte {
// remove all instances of OP_CODESEPARATOR still left in the script
script = removeOpcode(script, OP_CODESEPARATOR)
// Make a deep copy of the transaction, zeroing out the script
// for all inputs that are not currently being processed.
txCopy := tx.Copy()
for i := range txCopy.TxIn {
var txIn btcwire.TxIn
txIn = *txCopy.TxIn[i]
txCopy.TxIn[i] = &txIn
if i == idx {
// unparseScript cannot fail here, because removeOpcode
// above only returns a valid script.
sigscript, _ := unparseScript(script)
txCopy.TxIn[idx].SignatureScript = sigscript
} else {
txCopy.TxIn[i].SignatureScript = []byte{}
}
}
// Default behaviour has all outputs set up.
for i := range txCopy.TxOut {
var txOut btcwire.TxOut
txOut = *txCopy.TxOut[i]
txCopy.TxOut[i] = &txOut
}
switch hashType & 31 {
case SigHashNone:
txCopy.TxOut = txCopy.TxOut[0:0] // empty slice
for i := range txCopy.TxIn {
if i != idx {
txCopy.TxIn[i].Sequence = 0
}
}
case SigHashSingle:
if idx >= len(txCopy.TxOut) {
// This was created by a buggy implementation.
// In this case we do the same as bitcoind and bitcoinj
// and return 1 (as a uint256 little endian) as an
// error. Unfortunately this was not checked anywhere
// and thus is treated as the actual
// hash.
hash := make([]byte, 32)
hash[0] = 0x01
return hash
}
// Resize output array to up to and including requested index.
txCopy.TxOut = txCopy.TxOut[:idx+1]
// all but current output get zeroed out
for i := 0; i < idx; i++ {
txCopy.TxOut[i].Value = -1
txCopy.TxOut[i].PkScript = []byte{}
}
// Sequence on all other inputs is 0, too.
for i := range txCopy.TxIn {
if i != idx {
txCopy.TxIn[i].Sequence = 0
}
}
default:
// XXX bitcoind treats undefined hashtypes like normal
// SigHashAll for purposes of hash generation.
fallthrough
case SigHashOld:
fallthrough
case SigHashAll:
// nothing special here
}
if hashType&SigHashAnyOneCanPay != 0 {
txCopy.TxIn = txCopy.TxIn[idx : idx+1]
idx = 0
}
var wbuf bytes.Buffer
txCopy.Serialize(&wbuf)
// Append LE 4 bytes hash type
binary.Write(&wbuf, binary.LittleEndian, uint32(hashType))
return btcwire.DoubleSha256(wbuf.Bytes())
}