lnwallet: use channel type to derive remote script

Based on the current channel type, we derive the script used for the
to_remote output. Currently only the unencumbered p2wkh type is used,
but that will change with upcoming channel types.

contractcourt/chain_watcher.go

@@ -351,8 +351,9 @@ func isOurCommitment(localChanCfg, remoteChanCfg channeldb.ChannelConfig,
 
 	// With the keys derived, we'll construct the remote script that'll be
 	// present if they have a non-dust balance on the commitment.
-	remotePkScript, err := input.CommitScriptUnencumbered(
+	remoteDelay := uint32(remoteChanCfg.CsvDelay)
-		commitKeyRing.ToRemoteKey,
+	remoteScript, err := lnwallet.CommitScriptToRemote(
+		chanType, remoteDelay, commitKeyRing.ToRemoteKey,
 	)
 	if err != nil {
 		return false, err
@@ -383,7 +384,7 @@ func isOurCommitment(localChanCfg, remoteChanCfg channeldb.ChannelConfig,
 		case bytes.Equal(localPkScript, pkScript):
 			return true, nil
 
-		case bytes.Equal(remotePkScript, pkScript):
+		case bytes.Equal(remoteScript.PkScript, pkScript):
 			return true, nil
 		}
 	}

lnwallet/channel.go

@@ -1871,36 +1871,42 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 	// Next, reconstruct the scripts as they were present at this state
 	// number so we can have the proper witness script to sign and include
 	// within the final witness.
-	remoteDelay := uint32(chanState.RemoteChanCfg.CsvDelay)
+	theirDelay := uint32(chanState.RemoteChanCfg.CsvDelay)
-	remotePkScript, err := input.CommitScriptToSelf(
+	theirPkScript, err := input.CommitScriptToSelf(
-		remoteDelay, keyRing.ToLocalKey, keyRing.RevocationKey,
+		theirDelay, keyRing.ToLocalKey, keyRing.RevocationKey,
 	)
 	if err != nil {
 		return nil, err
 	}
-	remoteWitnessHash, err := input.WitnessScriptHash(remotePkScript)
+	theirWitnessHash, err := input.WitnessScriptHash(theirPkScript)
 	if err != nil {
 		return nil, err
 	}
-	localPkScript, err := input.CommitScriptUnencumbered(keyRing.ToRemoteKey)
+
+	// Since it is the remote breach we are reconstructing, the output going
+	// to us will be a to-remote script with our local params.
+	ourDelay := uint32(chanState.LocalChanCfg.CsvDelay)
+	ourScript, err := CommitScriptToRemote(
+		chanState.ChanType, ourDelay, keyRing.ToRemoteKey,
+	)
 	if err != nil {
 		return nil, err
 	}
 
 	// In order to fully populate the breach retribution struct, we'll need
-	// to find the exact index of the local+remote commitment outputs.
+	// to find the exact index of the commitment outputs.
-	localOutpoint := wire.OutPoint{
+	ourOutpoint := wire.OutPoint{
 		Hash: commitHash,
 	}
-	remoteOutpoint := wire.OutPoint{
+	theirOutpoint := wire.OutPoint{
 		Hash: commitHash,
 	}
 	for i, txOut := range revokedSnapshot.CommitTx.TxOut {
 		switch {
-		case bytes.Equal(txOut.PkScript, localPkScript):
+		case bytes.Equal(txOut.PkScript, ourScript.PkScript):
-			localOutpoint.Index = uint32(i)
+			ourOutpoint.Index = uint32(i)
-		case bytes.Equal(txOut.PkScript, remoteWitnessHash):
+		case bytes.Equal(txOut.PkScript, theirWitnessHash):
-			remoteOutpoint.Index = uint32(i)
+			theirOutpoint.Index = uint32(i)
 		}
 	}
 
@@ -1908,39 +1914,39 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 	// commitment outputs. If either is considered dust using the remote
 	// party's dust limit, the respective sign descriptor will be nil.
 	var (
-		localSignDesc  *input.SignDescriptor
+		ourSignDesc   *input.SignDescriptor
-		remoteSignDesc *input.SignDescriptor
+		theirSignDesc *input.SignDescriptor
 	)
 
-	// Compute the local and remote balances in satoshis.
+	// Compute the balances in satoshis.
-	localAmt := revokedSnapshot.LocalBalance.ToSatoshis()
+	ourAmt := revokedSnapshot.LocalBalance.ToSatoshis()
-	remoteAmt := revokedSnapshot.RemoteBalance.ToSatoshis()
+	theirAmt := revokedSnapshot.RemoteBalance.ToSatoshis()
 
-	// If the local balance exceeds the remote party's dust limit,
+	// If our balance exceeds the remote party's dust limit, instantiate
-	// instantiate the local sign descriptor.
+	// the sign descriptor for our output.
-	if localAmt >= chanState.RemoteChanCfg.DustLimit {
+	if ourAmt >= chanState.RemoteChanCfg.DustLimit {
-		localSignDesc = &input.SignDescriptor{
+		ourSignDesc = &input.SignDescriptor{
 			SingleTweak:   keyRing.LocalCommitKeyTweak,
 			KeyDesc:       chanState.LocalChanCfg.PaymentBasePoint,
-			WitnessScript: localPkScript,
+			WitnessScript: ourScript.WitnessScript,
 			Output: &wire.TxOut{
-				PkScript: localPkScript,
+				PkScript: ourScript.PkScript,
-				Value:    int64(localAmt),
+				Value:    int64(ourAmt),
 			},
 			HashType: txscript.SigHashAll,
 		}
 	}
 
-	// Similarly, if the remote balance exceeds the remote party's dust
+	// Similarly, if their balance exceeds the remote party's dust limit,
-	// limit, assemble the remote sign descriptor.
+	// assemble the sign descriptor for their output, which we can sweep.
-	if remoteAmt >= chanState.RemoteChanCfg.DustLimit {
+	if theirAmt >= chanState.RemoteChanCfg.DustLimit {
-		remoteSignDesc = &input.SignDescriptor{
+		theirSignDesc = &input.SignDescriptor{
 			KeyDesc:       chanState.LocalChanCfg.RevocationBasePoint,
 			DoubleTweak:   commitmentSecret,
-			WitnessScript: remotePkScript,
+			WitnessScript: theirPkScript,
 			Output: &wire.TxOut{
-				PkScript: remoteWitnessHash,
+				PkScript: theirWitnessHash,
-				Value:    int64(remoteAmt),
+				Value:    int64(theirAmt),
 			},
 			HashType: txscript.SigHashAll,
 		}
@@ -1971,7 +1977,7 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 		// remote commitment transaction, and *they* go to the second
 		// level.
 		secondLevelWitnessScript, err := input.SecondLevelHtlcScript(
-			keyRing.RevocationKey, keyRing.ToLocalKey, remoteDelay,
+			keyRing.RevocationKey, keyRing.ToLocalKey, theirDelay,
 		)
 		if err != nil {
 			return nil, err
@@ -2037,13 +2043,13 @@ func NewBreachRetribution(chanState *channeldb.OpenChannel, stateNum uint64,
 		BreachHeight:         breachHeight,
 		RevokedStateNum:      stateNum,
 		PendingHTLCs:         revokedSnapshot.Htlcs,
-		LocalOutpoint:        localOutpoint,
+		LocalOutpoint:        ourOutpoint,
-		LocalOutputSignDesc:  localSignDesc,
+		LocalOutputSignDesc:  ourSignDesc,
-		RemoteOutpoint:       remoteOutpoint,
+		RemoteOutpoint:       theirOutpoint,
-		RemoteOutputSignDesc: remoteSignDesc,
+		RemoteOutputSignDesc: theirSignDesc,
 		HtlcRetributions:     htlcRetributions,
 		KeyRing:              keyRing,
-		RemoteDelay:          remoteDelay,
+		RemoteDelay:          theirDelay,
 	}, nil
 }
 
@@ -4758,7 +4764,10 @@ func NewUnilateralCloseSummary(chanState *channeldb.OpenChannel, signer input.Si
 	// Before we can generate the proper sign descriptor, we'll need to
 	// locate the output index of our non-delayed output on the commitment
 	// transaction.
-	selfP2WKH, err := input.CommitScriptUnencumbered(keyRing.ToRemoteKey)
+	localDelay := uint32(chanState.LocalChanCfg.CsvDelay)
+	selfScript, err := CommitScriptToRemote(
+		chanState.ChanType, localDelay, keyRing.ToRemoteKey,
+	)
 	if err != nil {
 		return nil, fmt.Errorf("unable to create self commit "+
 			"script: %v", err)
@@ -4770,7 +4779,7 @@ func NewUnilateralCloseSummary(chanState *channeldb.OpenChannel, signer input.Si
 	)
 
 	for outputIndex, txOut := range commitTxBroadcast.TxOut {
-		if bytes.Equal(txOut.PkScript, selfP2WKH) {
+		if bytes.Equal(txOut.PkScript, selfScript.PkScript) {
 			selfPoint = &wire.OutPoint{
 				Hash:  *commitSpend.SpenderTxHash,
 				Index: uint32(outputIndex),
@@ -4791,10 +4800,10 @@ func NewUnilateralCloseSummary(chanState *channeldb.OpenChannel, signer input.Si
 			SelfOutputSignDesc: input.SignDescriptor{
 				KeyDesc:       localPayBase,
 				SingleTweak:   keyRing.LocalCommitKeyTweak,
-				WitnessScript: selfP2WKH,
+				WitnessScript: selfScript.WitnessScript,
 				Output: &wire.TxOut{
 					Value:    localBalance,
-					PkScript: selfP2WKH,
+					PkScript: selfScript.PkScript,
 				},
 				HashType: txscript.SigHashAll,
 			},

lnwallet/commitment.go

@@ -162,6 +162,37 @@ func DeriveCommitmentKeys(commitPoint *btcec.PublicKey,
 	return keyRing
 }
 
+// ScriptInfo holds a redeem script and hash.
+type ScriptInfo struct {
+	// PkScript is the output's PkScript.
+	PkScript []byte
+
+	// WitnessScript is the full script required to properly redeem the
+	// output. This field should be set to the full script if a p2wsh
+	// output is being signed. For p2wkh it should be set equal to the
+	// PkScript.
+	WitnessScript []byte
+}
+
+// CommitScriptToRemote creates the script that will pay to the non-owner of
+// the commitment transaction, adding a delay to the script based on the
+// channel type.
+func CommitScriptToRemote(_ channeldb.ChannelType, csvTimeout uint32,
+	key *btcec.PublicKey) (*ScriptInfo, error) {
+
+	p2wkh, err := input.CommitScriptUnencumbered(key)
+	if err != nil {
+		return nil, err
+	}
+
+	// Since this is a regular P2WKH, the WitnessScipt and PkScript should
+	// both be set to the script hash.
+	return &ScriptInfo{
+		WitnessScript: p2wkh,
+		PkScript:      p2wkh,
+	}, nil
+}
+
 // CommitmentBuilder is a type that wraps the type of channel we are dealing
 // with, and abstracts the various ways of constructing commitment
 // transactions.
@@ -292,15 +323,15 @@ func (cb *CommitmentBuilder) createUnsignedCommitmentTx(ourBalance,
 	// out HTLCs.
 	if isOurs {
 		commitTx, err = CreateCommitTx(
-			fundingTxIn(cb.chanState), keyRing, &cb.chanState.LocalChanCfg,
+			cb.chanState.ChanType, fundingTxIn(cb.chanState), keyRing,
-			&cb.chanState.RemoteChanCfg, ourBalance.ToSatoshis(),
+			&cb.chanState.LocalChanCfg, &cb.chanState.RemoteChanCfg,
-			theirBalance.ToSatoshis(),
+			ourBalance.ToSatoshis(), theirBalance.ToSatoshis(),
 		)
 	} else {
 		commitTx, err = CreateCommitTx(
-			fundingTxIn(cb.chanState), keyRing, &cb.chanState.RemoteChanCfg,
+			cb.chanState.ChanType, fundingTxIn(cb.chanState), keyRing,
-			&cb.chanState.LocalChanCfg, theirBalance.ToSatoshis(),
+			&cb.chanState.RemoteChanCfg, &cb.chanState.LocalChanCfg,
-			ourBalance.ToSatoshis(),
+			theirBalance.ToSatoshis(), ourBalance.ToSatoshis(),
 		)
 	}
 	if err != nil {
@@ -389,7 +420,8 @@ func (cb *CommitmentBuilder) createUnsignedCommitmentTx(ourBalance,
 // spent after a relative block delay or revocation event, and a remote output
 // paying the counterparty within the channel, which can be spent immediately
 // or after a delay depending on the commitment type..
-func CreateCommitTx(fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
+func CreateCommitTx(chanType channeldb.ChannelType,
+	fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
 	localChanCfg, remoteChanCfg *channeldb.ChannelConfig,
 	amountToLocal, amountToRemote btcutil.Amount) (*wire.MsgTx, error) {
 
@@ -412,10 +444,9 @@ func CreateCommitTx(fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
 		return nil, err
 	}
 
-	// Next, we create the script paying to the remote. This is just a
+	// Next, we create the script paying to the remote.
-	// regular P2WPKH output, without any added CSV delay.
+	toRemoteScript, err := CommitScriptToRemote(
-	toRemoteWitnessKeyHash, err := input.CommitScriptUnencumbered(
+		chanType, uint32(remoteChanCfg.CsvDelay), keyRing.ToRemoteKey,
-		keyRing.ToRemoteKey,
 	)
 	if err != nil {
 		return nil, err
@@ -436,7 +467,7 @@ func CreateCommitTx(fundingOutput wire.TxIn, keyRing *CommitmentKeyRing,
 	}
 	if amountToRemote >= localChanCfg.DustLimit {
 		commitTx.AddTxOut(&wire.TxOut{
-			PkScript: toRemoteWitnessKeyHash,
+			PkScript: toRemoteScript.PkScript,
 			Value:    int64(amountToRemote),
 		})
 	}

lnwallet/transactions_test.go

@@ -1048,8 +1048,10 @@ func testSpendValidation(t *testing.T, tweakless bool) {
 	// our commitments, if it's tweakless, his key will just be his regular
 	// pubkey.
 	bobPayKey := input.TweakPubKey(bobKeyPub, commitPoint)
+	channelType := channeldb.SingleFunderBit
 	if tweakless {
 		bobPayKey = bobKeyPub
+		channelType = channeldb.SingleFunderTweaklessBit
 	}
 
 	aliceCommitTweak := input.SingleTweakBytes(commitPoint, aliceKeyPub)
@@ -1086,8 +1088,8 @@ func testSpendValidation(t *testing.T, tweakless bool) {
 		ToRemoteKey:   bobPayKey,
 	}
 	commitmentTx, err := CreateCommitTx(
-		*fakeFundingTxIn, keyRing, aliceChanCfg, bobChanCfg,
+		channelType, *fakeFundingTxIn, keyRing, aliceChanCfg,
-		channelBalance, channelBalance,
+		bobChanCfg, channelBalance, channelBalance,
 	)
 	if err != nil {
 		t.Fatalf("unable to create commitment transaction: %v", nil)

lnwallet/wallet.go

@@ -783,8 +783,8 @@ func CreateCommitmentTxns(localBalance, remoteBalance btcutil.Amount,
 	)
 
 	ourCommitTx, err := CreateCommitTx(
-		fundingTxIn, localCommitmentKeys, ourChanCfg, theirChanCfg,
+		chanType, fundingTxIn, localCommitmentKeys, ourChanCfg,
-		localBalance, remoteBalance,
+		theirChanCfg, localBalance, remoteBalance,
 	)
 	if err != nil {
 		return nil, nil, err
@@ -796,8 +796,8 @@ func CreateCommitmentTxns(localBalance, remoteBalance btcutil.Amount,
 	}
 
 	theirCommitTx, err := CreateCommitTx(
-		fundingTxIn, remoteCommitmentKeys, theirChanCfg, ourChanCfg,
+		chanType, fundingTxIn, remoteCommitmentKeys, theirChanCfg,
-		remoteBalance, localBalance,
+		ourChanCfg, remoteBalance, localBalance,
 	)
 	if err != nil {
 		return nil, nil, err