lnwallet: update the witness generation funcs for sender's HTLC output
This commit updates all the spendHtlcSpend* functions which are used to spend each of the possible clauses within the HTLC contract placed on the sender’s commitment transaction.
This commit is contained in:
Olaoluwa Osuntokun
parent
8f5129e08f
commit
d697c6ca9a
@ -270,32 +270,29 @@ func senderHTLCScript(senderKey, receiverKey, revocationKey *btcec.PublicKey,
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}
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// senderHtlcSpendRevoke constructs a valid witness allowing the receiver of an
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// HTLC to claim the output with knowledge of the revocation preimage in the
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// HTLC to claim the output with knowledge of the revocation private key in the
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// scenario that the sender of the HTLC broadcasts a previously revoked
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// commitment transaction. A valid spend requires knowledge of the preimage to
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// the commitment transaction's revocation hash, and a valid signature under
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// the receiver's public key.
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func senderHtlcSpendRevoke(commitScript []byte, outputAmt btcutil.Amount,
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reciverKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
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revokePreimage []byte) (wire.TxWitness, error) {
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// commitment transaction. A valid spend requires knowledge of the private key
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// that corresponds to their revocation base point and also the private key fro
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// the per commitment point, and a valid signature under the combined public
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// key.
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func senderHtlcSpendRevoke(signer Signer, signDesc *SignDescriptor,
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revokeKey *btcec.PublicKey, sweepTx *wire.MsgTx) (wire.TxWitness, error) {
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hashCache := txscript.NewTxSigHashes(sweepTx)
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sweepSig, err := txscript.RawTxInWitnessSignature(
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sweepTx, hashCache, 0, int64(outputAmt), commitScript,
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txscript.SigHashAll, reciverKey)
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sweepSig, err := signer.SignOutputRaw(sweepTx, signDesc)
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if err != nil {
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return nil, err
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}
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// In order to force script execution to enter the revocation clause,
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// we place two one's as the first items in the final evaluated witness
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// stack.
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witnessStack := wire.TxWitness(make([][]byte, 5))
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witnessStack[0] = sweepSig
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witnessStack[1] = revokePreimage
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witnessStack[2] = []byte{1}
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witnessStack[3] = []byte{1}
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witnessStack[4] = commitScript
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// The stack required to sweep a revoke HTLC output consists simply of
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// the exact witness stack as one of a regular p2wkh spend. The only
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// difference is that the keys used were derived in an adversarial
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// manner in order to encode the revocation contract into a sig+key
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// pair.
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witnessStack := wire.TxWitness(make([][]byte, 3))
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witnessStack[0] = append(sweepSig, byte(txscript.SigHashAll))
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witnessStack[1] = revokeKey.SerializeCompressed()
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witnessStack[2] = signDesc.WitnessScript
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return witnessStack, nil
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}
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@ -303,70 +300,49 @@ func senderHtlcSpendRevoke(commitScript []byte, outputAmt btcutil.Amount,
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// senderHtlcSpendRedeem constructs a valid witness allowing the receiver of an
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// HTLC to redeem the pending output in the scenario that the sender broadcasts
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// their version of the commitment transaction. A valid spend requires
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// knowledge of the payment preimage, and a valid signature under the
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// receivers public key.
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func senderHtlcSpendRedeem(commitScript []byte, outputAmt btcutil.Amount,
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reciverKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
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paymentPreimage []byte) (wire.TxWitness, error) {
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// knowledge of the payment preimage, and a valid signature under the receivers
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// public key.
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func senderHtlcSpendRedeem(signer Signer, signDesc *SignDescriptor,
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sweepTx *wire.MsgTx, paymentPreimage []byte) (wire.TxWitness, error) {
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hashCache := txscript.NewTxSigHashes(sweepTx)
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sweepSig, err := txscript.RawTxInWitnessSignature(
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sweepTx, hashCache, 0, int64(outputAmt), commitScript,
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txscript.SigHashAll, reciverKey)
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sweepSig, err := signer.SignOutputRaw(sweepTx, signDesc)
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if err != nil {
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return nil, err
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}
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// We force script execution into the HTLC redemption clause by placing
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// a one, then a zero as the first items in the final evaluated
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// witness stack.
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witnessStack := wire.TxWitness(make([][]byte, 5))
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witnessStack[0] = sweepSig
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// The stack require to spend this output is simply the signature
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// generated above under the receiver's public key, and the payment
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// pre-image.
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witnessStack := wire.TxWitness(make([][]byte, 3))
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witnessStack[0] = append(sweepSig, byte(txscript.SigHashAll))
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witnessStack[1] = paymentPreimage
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witnessStack[2] = nil
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witnessStack[3] = []byte{1}
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witnessStack[4] = commitScript
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witnessStack[2] = signDesc.WitnessScript
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return witnessStack, nil
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}
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// htlcSpendTimeout constructs a valid witness allowing the sender of an HTLC
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// to recover the pending funds after an absolute, then relative locktime
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// period.
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func senderHtlcSpendTimeout(commitScript []byte, outputAmt btcutil.Amount,
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senderKey *btcec.PrivateKey, sweepTx *wire.MsgTx,
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absoluteTimeout, relativeTimeout uint32) (wire.TxWitness, error) {
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// senderHtlcSpendTimeout constructs a valid witness allowing the sender of an
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// HTLC to activate the time locked covenant clause of a soon to be expired
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// HTLC. This script simply spends the multi-sig output using the
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// pre-generated HTLC timeout transaction.
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func senderHtlcSpendTimeout(reciverSig []byte, signer Signer,
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signDesc *SignDescriptor, htlcTimeoutTx *wire.MsgTx) (wire.TxWitness, error) {
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// Since the HTLC output has an absolute timeout before we're permitted
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// to sweep the output, we need to set the locktime of this sweeping
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// transaction to that absolute value in order to pass Script
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// verification.
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sweepTx.LockTime = absoluteTimeout
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// Additionally, we're required to wait a relative period of time
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// before we can sweep the output in order to allow the other party to
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// contest our claim of validity to this version of the commitment
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// transaction.
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sweepTx.TxIn[0].Sequence = lockTimeToSequence(false, relativeTimeout)
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// Finally, OP_CSV requires that the version of the transaction
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// spending a pkscript with OP_CSV within it *must* be >= 2.
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sweepTx.Version = 2
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hashCache := txscript.NewTxSigHashes(sweepTx)
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sweepSig, err := txscript.RawTxInWitnessSignature(
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sweepTx, hashCache, 0, int64(outputAmt), commitScript,
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txscript.SigHashAll, senderKey)
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sweepSig, err := signer.SignOutputRaw(htlcTimeoutTx, signDesc)
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if err != nil {
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return nil, err
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}
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// We place a zero as the first item of the evaluated witness stack in
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// order to force Script execution to the HTLC timeout clause.
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witnessStack := wire.TxWitness(make([][]byte, 3))
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witnessStack[0] = sweepSig
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witnessStack[1] = nil
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witnessStack[2] = commitScript
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// order to force Script execution to the HTLC timeout clause. The
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// second zero is require to consume the extra pop due to a bug in the
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// original OP_CHECKMULTISIG.
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witnessStack := wire.TxWitness(make([][]byte, 5))
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witnessStack[0] = nil
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witnessStack[1] = append(reciverSig, byte(txscript.SigHashAll))
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witnessStack[2] = append(sweepSig, byte(txscript.SigHashAll))
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witnessStack[3] = nil
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witnessStack[4] = signDesc.WitnessScript
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return witnessStack, nil
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}
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