// spendNestedWitnessPubKey generates both a sigScript, and valid witness for
// spending the passed pkScript with the specified input amount. The generated
// sigScript is the version 0 p2wkh witness program corresponding to the queried
// key. The witness stack is identical to that of one which spends a regular
// p2wkh output. The input amount *must* correspond to the output value of the
// previous pkScript, or else verification will fail since the new sighash
// digest algorithm defined in BIP0143 includes the input value in the sighash.
func spendNestedWitnessPubKeyHash(txIn *wire.TxIn, pkScript []byte,
inputValue int64, chainParams *chaincfg.Params, secrets SecretsSource,
tx *wire.MsgTx, hashCache *txscript.TxSigHashes, idx int) error {
// First we need to obtain the key pair related to this p2sh output.
_, addrs, _, err := txscript.ExtractPkScriptAddrs(pkScript,
chainParams)
if err != nil {
return err
}
privKey, compressed, err := secrets.GetKey(addrs[0])
if err != nil {
return err
}
pubKey := privKey.PubKey()
var pubKeyHash []byte
if compressed {
pubKeyHash = btcutil.Hash160(pubKey.SerializeCompressed())
} else {
pubKeyHash = btcutil.Hash160(pubKey.SerializeUncompressed())
}
// Next, we'll generate a valid sigScript that'll allow us to spend
// the p2sh output. The sigScript will contain only a single push of
// the p2wkh witness program corresponding to the matching public key
// of this address.
p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash, chainParams)
if err != nil {
return err
}
witnessProgram, err := txscript.PayToAddrScript(p2wkhAddr)
if err != nil {
return err
}
bldr := txscript.NewScriptBuilder()
bldr.AddData(witnessProgram)
sigScript, err := bldr.Script()
if err != nil {
return err
}
txIn.SignatureScript = sigScript
// With the sigScript in place, we'll next generate the proper witness
// that'll allow us to spend the p2wkh output.
witnessScript, err := txscript.WitnessScript(tx, hashCache, idx,
inputValue, witnessProgram, txscript.SigHashAll, privKey, compressed)
if err != nil {
return err
}
txIn.Witness = witnessScript
return nil
}
// spendWitnessKeyHash generates, and sets a valid witness for spending the
// passed pkScript with the specified input amount. The input amount *must*
// correspond to the output value of the previous pkScript, or else verification
// will fail since the new sighash digest algorithm defined in BIP0143 includes
// the input value in the sighash.
func spendWitnessKeyHash(txIn *wire.TxIn, pkScript []byte,
inputValue int64, chainParams *chaincfg.Params, secrets SecretsSource,
tx *wire.MsgTx, hashCache *txscript.TxSigHashes, idx int) error {
// First obtain the key pair associated with this p2wkh address.
_, addrs, _, err := txscript.ExtractPkScriptAddrs(pkScript,
chainParams)
if err != nil {
return err
}
privKey, compressed, err := secrets.GetKey(addrs[0])
if err != nil {
return err
}
pubKey := privKey.PubKey()
// Once we have the key pair, generate a p2wkh address type, respecting
// the compression type of the generated key.
var pubKeyHash []byte
if compressed {
pubKeyHash = btcutil.Hash160(pubKey.SerializeCompressed())
} else {
pubKeyHash = btcutil.Hash160(pubKey.SerializeUncompressed())
}
p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash, chainParams)
if err != nil {
return err
}
// With the concrete address type, we can now generate the
// corresponding witness program to be used to generate a valid witness
// which will allow us to spend this output.
witnessProgram, err := txscript.PayToAddrScript(p2wkhAddr)
if err != nil {
return err
}
witnessScript, err := txscript.WitnessScript(tx, hashCache, idx,
inputValue, witnessProgram, txscript.SigHashAll, privKey, true)
if err != nil {
return err
}
txIn.Witness = witnessScript
return nil
}