// receiverHtlcSpendTimeout constructs a valid witness allowing the sender of
// an HTLC to recover the pending funds after an absolute timeout in the
// scenario that the receiver of the HTLC broadcasts their version of the
// commitment transaction.
func receiverHtlcSpendTimeout(commitScript []byte, outputAmt btcutil.Amount,
senderKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
absoluteTimeout uint32) (wire.TxWitness, error) {
// The HTLC output has an absolute time period before we are permitted
// to recover the pending funds. Therefore we need to set the locktime
// on this sweeping transaction in order to pass Script verification.
sweepTx.LockTime = absoluteTimeout
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, senderKey)
if err != nil {
return nil, err
}
witnessStack := wire.TxWitness(make([][]byte, 4))
witnessStack[0] = sweepSig
witnessStack[1] = []byte{0}
witnessStack[2] = []byte{0}
witnessStack[3] = commitScript
return witnessStack, nil
}
// CommitSpendTimeout constructs a valid witness allowing the owner of a
// particular commitment transaction to spend the output returning settled
// funds back to themselves after a relative block timeout. In order to
// properly spend the transaction, the target input's sequence number should be
// set accordingly based off of the target relative block timeout within the
// redeem script. Additionally, OP_CSV requires that the version of the
// transaction spending a pkscript with OP_CSV within it *must* be >= 2.
func CommitSpendTimeout(signer Signer, signDesc *SignDescriptor,
sweepTx *wire.MsgTx) (wire.TxWitness, error) {
// Ensure the transaction version supports the validation of sequence
// locks and CSV semantics.
if sweepTx.Version < 2 {
return nil, fmt.Errorf("version of passed transaction MUST "+
"be >= 2, not %v", sweepTx.Version)
}
// With the sequence number in place, we're now able to properly sign
// off on the sweep transaction.
sweepSig, err := signer.SignOutputRaw(sweepTx, signDesc)
if err != nil {
return nil, err
}
// Place a zero as the first item in the evaluated witness stack to
// force script execution to the timeout spend clause.
witnessStack := wire.TxWitness(make([][]byte, 3))
witnessStack[0] = append(sweepSig, byte(txscript.SigHashAll))
witnessStack[1] = []byte{0}
witnessStack[2] = signDesc.WitnessScript
return witnessStack, nil
}
// receiverHtlcSpendRevoke constructs a valid witness allowing the sender of an
// HTLC within a previously revoked commitment transaction to re-claim the
// pending funds in the case that the receiver broadcasts this revoked
// commitment transaction.
func receiverHtlcSpendRevoke(commitScript []byte, outputAmt btcutil.Amount,
senderKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
revokePreimage []byte) (wire.TxWitness, error) {
// TODO(roasbeef): move sig generate outside func, or just factor out?
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, senderKey)
if err != nil {
return nil, err
}
// We place a zero, then one as the first items in the evaluated
// witness stack in order to force script execution to the HTLC
// revocation clause.
witnessStack := wire.TxWitness(make([][]byte, 5))
witnessStack[0] = sweepSig
witnessStack[1] = revokePreimage
witnessStack[2] = []byte{1}
witnessStack[3] = []byte{0}
witnessStack[4] = commitScript
return witnessStack, nil
}
// receiverHtlcSpendRedeem constructs a valid witness allowing the receiver of
// an HTLC to redeem the conditional payment in the event that their commitment
// transaction is broadcast. Since this is a pay out to the receiving party as
// an output on their commitment transaction, a relative time delay is required
// before the output can be spent.
func receiverHtlcSpendRedeem(commitScript []byte, outputAmt btcutil.Amount,
reciverKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
paymentPreimage []byte, relativeTimeout uint32) (wire.TxWitness, error) {
// In order to properly spend the transaction, we need to set the
// sequence number. We do this by convering the relative block delay
// into a sequence number value able to be interpeted by
// OP_CHECKSEQUENCEVERIFY.
sweepTx.TxIn[0].Sequence = lockTimeToSequence(false, relativeTimeout)
// Additionally, OP_CSV requires that the version of the transaction
// spending a pkscript with OP_CSV within it *must* be >= 2.
sweepTx.Version = 2
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, reciverKey)
if err != nil {
return nil, err
}
// Place a one as the first item in the evaluated witness stack to
// force script execution to the HTLC redemption clause.
witnessStack := wire.TxWitness(make([][]byte, 4))
witnessStack[0] = sweepSig
witnessStack[1] = paymentPreimage
witnessStack[2] = []byte{1}
witnessStack[3] = commitScript
return witnessStack, nil
}
// commitSpendNoDelay constructs a valid witness allowing a node to spend their
// settled no-delay output on the counter-party's commitment transaction.
func commitSpendNoDelay(commitScript []byte, outputAmt btcutil.Amount,
commitPriv *btcec.PrivateKey, sweepTx *wire.MsgTx) (wire.TxWitness, error) {
// This is just a regular p2wkh spend which looks something like:
// * witness: <sig> <pubkey>
hashCache := txscript.NewTxSigHashes(sweepTx)
witness, err := txscript.WitnessScript(sweepTx, hashCache, 0,
int64(outputAmt), commitScript, txscript.SigHashAll,
commitPriv, true)
if err != nil {
return nil, err
}
return wire.TxWitness(witness), nil
}
// commitSpendRevoke constructs a valid witness allowing a node to sweep the
// settled output of a malicious counter-party who broadcasts a revoked
// commitment trransaction.
func commitSpendRevoke(commitScript []byte, outputAmt btcutil.Amount,
revocationPriv *btcec.PrivateKey, sweepTx *wire.MsgTx) (wire.TxWitness, error) {
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, revocationPriv)
if err != nil {
return nil, err
}
// Place a 1 as the first item in the evaluated witness stack to
// force script execution to the revocation clause.
witnessStack := wire.TxWitness(make([][]byte, 3))
witnessStack[0] = sweepSig
witnessStack[1] = []byte{1}
witnessStack[2] = commitScript
return witnessStack, nil
}
// htlcSpendTimeout constructs a valid witness allowing the sender of an HTLC
// to recover the pending funds after an absolute, then relative locktime
// period.
func senderHtlcSpendTimeout(commitScript []byte, outputAmt btcutil.Amount,
senderKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
absoluteTimeout, relativeTimeout uint32) (wire.TxWitness, error) {
// Since the HTLC output has an absolute timeout before we're permitted
// to sweep the output, we need to set the locktime of this sweepign
// transaction to that aboslute value in order to pass Script
// verification.
sweepTx.LockTime = absoluteTimeout
// Additionally, we're required to wait a relative period of time
// before we can sweep the output in order to allow the other party to
// contest our claim of validity to this version of the commitment
// transaction.
sweepTx.TxIn[0].Sequence = lockTimeToSequence(false, relativeTimeout)
// Finally, OP_CSV requires that the version of the transaction
// spending a pkscript with OP_CSV within it *must* be >= 2.
sweepTx.Version = 2
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, senderKey)
if err != nil {
return nil, err
}
// We place a zero as the first item of the evaluated witness stack in
// order to force Script execution to the HTLC timeout clause.
witnessStack := wire.TxWitness(make([][]byte, 3))
witnessStack[0] = sweepSig
witnessStack[1] = []byte{0}
witnessStack[2] = commitScript
return witnessStack, nil
}
// senderHtlcSpendRedeem constructs a valid witness allowing the receiver of an
// HTLC to redeem the pending output in the scenario that the sender broadcasts
// their version of the commitment transaction. A valid spend requires
// knowledge of the payment pre-image, and a valid signature under the
// receivers public key.
func senderHtlcSpendRedeem(commitScript []byte, outputAmt btcutil.Amount,
reciverKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
paymentPreimage []byte) (wire.TxWitness, error) {
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, reciverKey)
if err != nil {
return nil, err
}
// We force script execution into the HTLC redemption clause by placing
// a one, then a zero as the first items in the final evalulated
// witness stack.
witnessStack := wire.TxWitness(make([][]byte, 5))
witnessStack[0] = sweepSig
witnessStack[1] = paymentPreimage
witnessStack[2] = []byte{0}
witnessStack[3] = []byte{1}
witnessStack[4] = commitScript
return witnessStack, nil
}
// senderHtlcSpendRevoke constructs a valid witness allowing the reciever of an
// HTLC to claim the output with knowledge of the revocation preimage in the
// scenario that the sender of the HTLC broadcasts a previously revoked
// commitment transaction. A valid spend requires knowledge of the pre-image to
// the commitment transaction's revocation hash, and a valid signature under
// the receiver's public key.
func senderHtlcSpendRevoke(commitScript []byte, outputAmt btcutil.Amount,
reciverKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
revokePreimage []byte) (wire.TxWitness, error) {
hashCache := txscript.NewTxSigHashes(sweepTx)
sweepSig, err := txscript.RawTxInWitnessSignature(
sweepTx, hashCache, 0, int64(outputAmt), commitScript,
txscript.SigHashAll, reciverKey)
if err != nil {
return nil, err
}
// In order to force script execution to enter the revocation clause,
// we place two one's as the first items in the final evalulated
// witness stack.
witnessStack := wire.TxWitness(make([][]byte, 5))
witnessStack[0] = sweepSig
witnessStack[1] = revokePreimage
witnessStack[2] = []byte{1}
witnessStack[3] = []byte{1}
witnessStack[4] = commitScript
return witnessStack, nil
}