input+lnwallet: Add scripts for CSV delayed HTLC outputs

We also increase the witness size for these types to account for the 3
extra bytes. The size won't be correct in all cases, but it is just an
upper bound in any case.

input/script_utils.go

@@ -150,6 +150,9 @@ func Ripemd160H(d []byte) []byte {
 //    * The receiver of the HTLC sweeping all the funds in the case that a
 //      revoked commitment transaction bearing this HTLC was broadcast.
 //
+// If confirmedSpend=true, a 1 OP_CSV check will be added to the non-revocation
+// cases, to allow sweeping only after confirmation.
+//
 // Possible Input Scripts:
 //    SENDR: <0> <sendr sig>  <recvr sig> <0> (spend using HTLC timeout transaction)
 //    RECVR: <recvr sig>  <preimage>
@@ -168,9 +171,11 @@ func Ripemd160H(d []byte) []byte {
 //         OP_HASH160 <ripemd160(payment hash)> OP_EQUALVERIFY
 //         OP_CHECKSIG
 //     OP_ENDIF
+//     [1 OP_CHECKSEQUENCEVERIFY OP_DROP] <- if allowing confirmed spend only.
 // OP_ENDIF
 func SenderHTLCScript(senderHtlcKey, receiverHtlcKey,
-	revocationKey *btcec.PublicKey, paymentHash []byte) ([]byte, error) {
+	revocationKey *btcec.PublicKey, paymentHash []byte,
+	confirmedSpend bool) ([]byte, error) {
 
 	builder := txscript.NewScriptBuilder()
 
@@ -243,6 +248,14 @@ func SenderHTLCScript(senderHtlcKey, receiverHtlcKey,
 	// Close out the OP_IF statement above.
 	builder.AddOp(txscript.OP_ENDIF)
 
+	// Add 1 block CSV delay if a confirmation is required for the
+	// non-revocation clauses.
+	if confirmedSpend {
+		builder.AddOp(txscript.OP_1)
+		builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY)
+		builder.AddOp(txscript.OP_DROP)
+	}
+
 	// Close out the OP_IF statement at the top of the script.
 	builder.AddOp(txscript.OP_ENDIF)
 
@@ -362,6 +375,9 @@ func SenderHtlcSpendTimeout(receiverSig []byte, signer Signer,
 //   * The sender of the HTLC sweeps the HTLC on-chain after the timeout period
 //     of the HTLC has passed.
 //
+// If confirmedSpend=true, a 1 OP_CSV check will be added to the non-revocation
+// cases, to allow sweeping only after confirmation.
+//
 // Possible Input Scripts:
 //    RECVR: <0> <sender sig> <recvr sig> <preimage> (spend using HTLC success transaction)
 //    REVOK: <sig> <key>
@@ -381,10 +397,11 @@ func SenderHtlcSpendTimeout(receiverSig []byte, signer Signer,
 //         OP_DROP <cltv expiry> OP_CHECKLOCKTIMEVERIFY OP_DROP
 //         OP_CHECKSIG
 //     OP_ENDIF
+//     [1 OP_CHECKSEQUENCEVERIFY OP_DROP] <- if allowing confirmed spend only.
 // OP_ENDIF
 func ReceiverHTLCScript(cltvExpiry uint32, senderHtlcKey,
 	receiverHtlcKey, revocationKey *btcec.PublicKey,
-	paymentHash []byte) ([]byte, error) {
+	paymentHash []byte, confirmedSpend bool) ([]byte, error) {
 
 	builder := txscript.NewScriptBuilder()
 
@@ -467,6 +484,14 @@ func ReceiverHTLCScript(cltvExpiry uint32, senderHtlcKey,
 	// Close out the inner if statement.
 	builder.AddOp(txscript.OP_ENDIF)
 
+	// Add 1 block CSV delay for non-revocation clauses if confirmation is
+	// required.
+	if confirmedSpend {
+		builder.AddOp(txscript.OP_1)
+		builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY)
+		builder.AddOp(txscript.OP_DROP)
+	}
+
 	// Close out the outer if statement.
 	builder.AddOp(txscript.OP_ENDIF)
 

input/script_utils_test.go

@@ -235,7 +235,7 @@ func TestHTLCSenderSpendValidation(t *testing.T) {
 		// counterpart.
 		htlcWitnessScript, err = SenderHTLCScript(
 			aliceLocalKey, bobLocalKey, revocationKey,
-			paymentHash[:],
+			paymentHash[:], false,
 		)
 		if err != nil {
 			t.Fatalf("unable to create htlc sender script: %v", err)
@@ -496,7 +496,7 @@ func TestHTLCReceiverSpendValidation(t *testing.T) {
 		// counterpart.
 		htlcWitnessScript, err = ReceiverHTLCScript(
 			cltvTimeout, aliceLocalKey, bobLocalKey, revocationKey,
-			paymentHash[:],
+			paymentHash[:], false,
 		)
 		if err != nil {
 			t.Fatalf("unable to create htlc sender script: %v", err)

input/size.go

@@ -213,7 +213,7 @@ const (
 	//      - witness_script (to_local_script)
 	ToLocalPenaltyWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize
 
-	// AcceptedHtlcScriptSize 139 bytes
+	// AcceptedHtlcScriptSize 142 bytes
 	//      - OP_DUP: 1 byte
 	//      - OP_HASH160: 1 byte
 	//      - OP_DATA: 1 byte (RIPEMD160(SHA256(revocationkey)) length)
@@ -247,11 +247,14 @@ const (
 	//                      - OP_DROP: 1 byte
 	//                      - OP_CHECKSIG: 1 byte
 	//              - OP_ENDIF: 1 byte
+	//              - OP_1: 1 byte		// These 3 extra bytes are used for both confirmed and regular
+	//              - OP_CSV: 1 byte	// HTLC script types. The size won't be correct in all cases,
+	//              - OP_DROP: 1 byte	// but it is just an upper bound used for fee estimation in any case.
 	//      - OP_ENDIF: 1 byte
 	AcceptedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 7*1 + 20 + 4*1 +
-		33 + 5*1 + 4 + 5*1
+		33 + 5*1 + 4 + 8*1
 
-	// AcceptedHtlcTimeoutWitnessSize 216
+	// AcceptedHtlcTimeoutWitnessSize 219
 	//      - number_of_witness_elements: 1 byte
 	//      - sender_sig_length: 1 byte
 	//      - sender_sig: 73 bytes
@@ -260,7 +263,7 @@ const (
 	//      - witness_script: (accepted_htlc_script)
 	AcceptedHtlcTimeoutWitnessSize = 1 + 1 + 73 + 1 + 1 + AcceptedHtlcScriptSize
 
-	// AcceptedHtlcPenaltyWitnessSize 249 bytes
+	// AcceptedHtlcPenaltyWitnessSize 252 bytes
 	//      - number_of_witness_elements: 1 byte
 	//      - revocation_sig_length: 1 byte
 	//      - revocation_sig: 73 bytes
@@ -270,7 +273,7 @@ const (
 	//      - witness_script (accepted_htlc_script)
 	AcceptedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + AcceptedHtlcScriptSize
 
-	// OfferedHtlcScriptSize 133 bytes
+	// OfferedHtlcScriptSize 136 bytes
 	//      - OP_DUP: 1 byte
 	//      - OP_HASH160: 1 byte
 	//      - OP_DATA: 1 byte (RIPEMD160(SHA256(revocationkey)) length)
@@ -301,10 +304,13 @@ const (
 	//                      - OP_EQUALVERIFY: 1 byte
 	//                      - OP_CHECKSIG: 1 byte
 	//              - OP_ENDIF: 1 byte
+	//              - OP_1: 1 byte
+	//              - OP_CSV: 1 byte
+	//              - OP_DROP: 1 byte
 	//      - OP_ENDIF: 1 byte
-	OfferedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 10*1 + 33 + 5*1 + 20 + 4*1
+	OfferedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 10*1 + 33 + 5*1 + 20 + 7*1
 
-	// OfferedHtlcSuccessWitnessSize 317 bytes
+	// OfferedHtlcSuccessWitnessSize 320 bytes
 	//      - number_of_witness_elements: 1 byte
 	//      - nil_length: 1 byte
 	//      - receiver_sig_length: 1 byte
@@ -317,7 +323,7 @@ const (
 	//      - witness_script (offered_htlc_script)
 	OfferedHtlcSuccessWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 + OfferedHtlcScriptSize
 
-	// OfferedHtlcPenaltyWitnessSize 243 bytes
+	// OfferedHtlcPenaltyWitnessSize 246 bytes
 	//      - number_of_witness_elements: 1 byte
 	//      - revocation_sig_length: 1 byte
 	//      - revocation_sig: 73 bytes

lnwallet/commitment.go

@@ -510,28 +510,28 @@ func genHtlcScript(chanType channeldb.ChannelType, isIncoming, ourCommit bool,
 	case isIncoming && ourCommit:
 		witnessScript, err = input.ReceiverHTLCScript(timeout,
 			keyRing.RemoteHtlcKey, keyRing.LocalHtlcKey,
-			keyRing.RevocationKey, rHash[:])
+			keyRing.RevocationKey, rHash[:], false)
 
 	// We're being paid via an HTLC by the remote party, and the HTLC is
 	// being added to their commitment transaction, so we use the sender's
 	// version of the HTLC script.
 	case isIncoming && !ourCommit:
 		witnessScript, err = input.SenderHTLCScript(keyRing.RemoteHtlcKey,
-			keyRing.LocalHtlcKey, keyRing.RevocationKey, rHash[:])
+			keyRing.LocalHtlcKey, keyRing.RevocationKey, rHash[:], false)
 
 	// We're sending an HTLC which is being added to our commitment
 	// transaction. Therefore, we need to use the sender's version of the
 	// HTLC script.
 	case !isIncoming && ourCommit:
 		witnessScript, err = input.SenderHTLCScript(keyRing.LocalHtlcKey,
-			keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
+			keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:], false)
 
 	// Finally, we're paying the remote party via an HTLC, which is being
 	// added to their commitment transaction. Therefore, we use the
 	// receiver's version of the HTLC script.
 	case !isIncoming && !ourCommit:
 		witnessScript, err = input.ReceiverHTLCScript(timeout, keyRing.LocalHtlcKey,
-			keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:])
+			keyRing.RemoteHtlcKey, keyRing.RevocationKey, rHash[:], false)
 	}
 	if err != nil {
 		return nil, nil, err

sweep/txgenerator_test.go

@@ -14,7 +14,7 @@ var (
 		input.HtlcOfferedRemoteTimeout,
 		input.WitnessKeyHash,
 	}
-	expectedWeight  = int64(1459)
+	expectedWeight  = int64(1462)
 	expectedSummary = "1 CommitmentTimeLock, 1 " +
 		"HtlcAcceptedSuccessSecondLevel, 1 HtlcOfferedRemoteTimeout, " +
 		"1 WitnessKeyHash"