watchtower: introduce CommitmentType

In this commit a new enum, CommitmentType, is introduced and initially
there are 3 CommitmentTypes: Legacy, LegacyTweakless and Anchor.

Then, various methods are added to `CommitmentType`. This allows us to
remove a bunch of "if-else" chains from the `wtclient` and `lookout`
code. This will also make things easier to extend when a new commitment
type (like Taproot) is added.

watchtower/blob/commitments.go

@@ -0,0 +1,174 @@
+package blob
+
+import (
+	"fmt"
+
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+// CommitmentType characterises the various properties of the breach commitment
+// transaction.
+type CommitmentType uint8
+
+const (
+	// LegacyCommitment represents a legacy commitment transaction where
+	// anchor outputs are not yet used and so the to_remote output is just
+	// a regular but tweaked P2WKH.
+	LegacyCommitment CommitmentType = iota
+
+	// LegacyTweaklessCommitment is similar to the LegacyCommitment with the
+	// added detail of the to_remote output not being tweaked.
+	LegacyTweaklessCommitment
+
+	// AnchorCommitment represents the commitment transaction of an
+	// anchor channel. The key differences are that the to_remote is
+	// encumbered by a 1 block CSV and so is thus a P2WSH output.
+	AnchorCommitment
+)
+
+// ToLocalInput constructs the input that will be used to spend the to_local
+// output.
+func (c CommitmentType) ToLocalInput(info *lnwallet.BreachRetribution) (
+	input.Input, error) {
+
+	witnessType, err := c.ToLocalWitnessType()
+	if err != nil {
+		return nil, err
+	}
+
+	return input.NewBaseInput(
+		&info.RemoteOutpoint, witnessType, info.RemoteOutputSignDesc, 0,
+	), nil
+}
+
+// ToRemoteInput constructs the input that will be used to spend the to_remote
+// output.
+func (c CommitmentType) ToRemoteInput(info *lnwallet.BreachRetribution) (
+	input.Input, error) {
+
+	witnessType, err := c.ToRemoteWitnessType()
+	if err != nil {
+		return nil, err
+	}
+
+	switch c {
+	case LegacyCommitment, LegacyTweaklessCommitment:
+		return input.NewBaseInput(
+			&info.LocalOutpoint, witnessType,
+			info.LocalOutputSignDesc, 0,
+		), nil
+
+	case AnchorCommitment:
+		// Anchor channels have a CSV-encumbered to-remote output. We'll
+		// construct a CSV input and assign the proper CSV delay of 1.
+		return input.NewCsvInput(
+			&info.LocalOutpoint, witnessType,
+			info.LocalOutputSignDesc, 0, 1,
+		), nil
+
+	default:
+		return nil, fmt.Errorf("unknown commitment type: %v", c)
+	}
+}
+
+// ToLocalWitnessType is the input type of the to_local output.
+func (c CommitmentType) ToLocalWitnessType() (input.WitnessType, error) {
+	switch c {
+	case LegacyTweaklessCommitment, LegacyCommitment, AnchorCommitment:
+		return input.CommitmentRevoke, nil
+
+	default:
+		return nil, fmt.Errorf("unknown commitment type: %v", c)
+	}
+}
+
+// ToRemoteWitnessType is the input type of the to_remote output.
+func (c CommitmentType) ToRemoteWitnessType() (input.WitnessType, error) {
+	switch c {
+	case LegacyTweaklessCommitment:
+		return input.CommitSpendNoDelayTweakless, nil
+
+	case LegacyCommitment:
+		return input.CommitmentNoDelay, nil
+
+	case AnchorCommitment:
+		return input.CommitmentToRemoteConfirmed, nil
+
+	default:
+		return nil, fmt.Errorf("unknown commitment type: %v", c)
+	}
+}
+
+// ToRemoteWitnessSize is the size of the witness that will be required to spend
+// the to_remote output.
+func (c CommitmentType) ToRemoteWitnessSize() (int, error) {
+	switch c {
+	// Legacy channels (both tweaked and non-tweaked) spend from P2WKH
+	// output.
+	case LegacyTweaklessCommitment, LegacyCommitment:
+		return input.P2WKHWitnessSize, nil
+
+	// Anchor channels spend a to-remote confirmed P2WSH output.
+	case AnchorCommitment:
+		return input.ToRemoteConfirmedWitnessSize, nil
+
+	default:
+		return 0, fmt.Errorf("unknown commitment type: %v", c)
+	}
+}
+
+// ToLocalWitnessSize is the size of the witness that will be required to spend
+// the to_local output.
+func (c CommitmentType) ToLocalWitnessSize() (int, error) {
+	switch c {
+	// An older ToLocalPenaltyWitnessSize constant used to underestimate the
+	// size by one byte. The difference in weight can cause different output
+	// values on the sweep transaction, so we mimic the original bug and
+	// create signatures using the original weight estimate.
+	case LegacyTweaklessCommitment, LegacyCommitment:
+		return input.ToLocalPenaltyWitnessSize - 1, nil
+
+	case AnchorCommitment:
+		return input.ToLocalPenaltyWitnessSize, nil
+
+	default:
+		return 0, fmt.Errorf("unknown commitment type: %v", c)
+	}
+}
+
+// ParseRawSig parses a wire.TxWitness and creates an lnwire.Sig.
+func (c CommitmentType) ParseRawSig(witness wire.TxWitness) (lnwire.Sig,
+	error) {
+
+	switch c {
+	case LegacyCommitment, LegacyTweaklessCommitment, AnchorCommitment:
+		// Check that the witness has at least one item.
+		if len(witness) < 1 {
+			return lnwire.Sig{}, fmt.Errorf("the witness should " +
+				"have at least one element")
+		}
+
+		// Check that the first witness element is non-nil. This is to
+		// ensure that the witness length check below does not panic.
+		if witness[0] == nil {
+			return lnwire.Sig{}, fmt.Errorf("the first witness " +
+				"element should not be nil")
+		}
+
+		// Parse the DER-encoded signature from the first position of
+		// the resulting witness. We trim an extra byte to remove the
+		// sighash flag.
+		rawSignature := witness[0][:len(witness[0])-1]
+
+		// Re-encode the DER signature into a fixed-size 64 byte
+		// signature.
+		return lnwire.NewSigFromECDSARawSignature(rawSignature)
+
+	default:
+		return lnwire.Sig{}, fmt.Errorf("unknown commitment type: %v",
+			c)
+	}
+}

watchtower/blob/type.go

@@ -3,6 +3,8 @@ package blob
 import (
 	"fmt"
 	"strings"
+
+	"github.com/lightningnetwork/lnd/channeldb"
 )
 
 // Flag represents a specify option that can be present in a Type.
@@ -81,6 +83,27 @@ func (t Type) Identifier() (string, error) {
 	}
 }
 
+// CommitmentType returns the appropriate CommitmentType for the given blob Type
+// and channel type.
+func (t Type) CommitmentType(chanType *channeldb.ChannelType) (CommitmentType,
+	error) {
+
+	switch {
+	case t.Has(FlagAnchorChannel):
+		return AnchorCommitment, nil
+
+	case t.Has(FlagCommitOutputs):
+		if chanType != nil && chanType.IsTweakless() {
+			return LegacyTweaklessCommitment, nil
+		}
+
+		return LegacyCommitment, nil
+
+	default:
+		return 0, ErrUnknownBlobType
+	}
+}
+
 // Has returns true if the Type has the passed flag enabled.
 func (t Type) Has(flag Flag) bool {
 	return Flag(t)&flag == flag

watchtower/lookout/justice_descriptor.go

@@ -264,6 +264,11 @@ func (p *JusticeDescriptor) CreateJusticeTxn() (*wire.MsgTx, error) {
 		weightEstimate input.TxWeightEstimator
 	)
 
+	commitmentType, err := p.SessionInfo.Policy.BlobType.CommitmentType(nil)
+	if err != nil {
+		return nil, err
+	}
+
 	// Add the sweep address's contribution, depending on whether it is a
 	// p2wkh or p2wsh output.
 	switch len(p.JusticeKit.SweepAddress) {
@@ -290,16 +295,13 @@ func (p *JusticeDescriptor) CreateJusticeTxn() (*wire.MsgTx, error) {
 		return nil, err
 	}
 
-	// An older ToLocalPenaltyWitnessSize constant used to underestimate the
-	// size by one byte. The diferrence in weight can cause different output
-	// values on the sweep transaction, so we mimic the original bug to
-	// avoid invalidating signatures by older clients. For anchor channels
-	// we correct this and use the correct witness size.
-	if p.JusticeKit.BlobType.IsAnchorChannel() {
-		weightEstimate.AddWitnessInput(input.ToLocalPenaltyWitnessSize)
-	} else {
-		weightEstimate.AddWitnessInput(input.ToLocalPenaltyWitnessSize - 1)
+	// Get the weight for the to-local witness and add that to the
+	// estimator.
+	toLocalWitnessSize, err := commitmentType.ToLocalWitnessSize()
+	if err != nil {
+		return nil, err
 	}
+	weightEstimate.AddWitnessInput(toLocalWitnessSize)
 
 	sweepInputs = append(sweepInputs, toLocalInput)
 
@@ -319,11 +321,14 @@ func (p *JusticeDescriptor) CreateJusticeTxn() (*wire.MsgTx, error) {
 		log.Debugf("Found to remote witness output=%#v, stack=%v",
 			toRemoteInput.txOut, toRemoteInput.witness)
 
-		if p.JusticeKit.BlobType.IsAnchorChannel() {
-			weightEstimate.AddWitnessInput(input.ToRemoteConfirmedWitnessSize)
-		} else {
-			weightEstimate.AddWitnessInput(input.P2WKHWitnessSize)
+		// Get the weight for the to-remote witness and add that to the
+		// estimator.
+		toRemoteWitnessSize, err := commitmentType.ToRemoteWitnessSize()
+		if err != nil {
+			return nil, err
 		}
+
+		weightEstimate.AddWitnessInput(toRemoteWitnessSize)
 	}
 
 	// TODO(conner): sweep htlc outputs

watchtower/lookout/justice_descriptor_test.go

@@ -92,15 +92,13 @@ func testJusticeDescriptor(t *testing.T, blobType blob.Type) {
 	)
 
 	// Parse the key pairs for all keys used in the test.
-	revSK, revPK := btcec.PrivKeyFromBytes(
-		revPrivBytes,
-	)
-	_, toLocalPK := btcec.PrivKeyFromBytes(
-		toLocalPrivBytes,
-	)
-	toRemoteSK, toRemotePK := btcec.PrivKeyFromBytes(
-		toRemotePrivBytes,
-	)
+	revSK, revPK := btcec.PrivKeyFromBytes(revPrivBytes)
+	_, toLocalPK := btcec.PrivKeyFromBytes(toLocalPrivBytes)
+	toRemoteSK, toRemotePK := btcec.PrivKeyFromBytes(toRemotePrivBytes)
+
+	// Get the commitment type.
+	commitType, err := blobType.CommitmentType(nil)
+	require.NoError(t, err)
 
 	// Create the signer, and add the revocation and to-remote privkeys.
 	signer := wtmock.NewMockSigner()
@@ -113,11 +111,11 @@ func testJusticeDescriptor(t *testing.T, blobType blob.Type) {
 	toLocalScript, err := input.CommitScriptToSelf(
 		csvDelay, toLocalPK, revPK,
 	)
-	require.Nil(t, err)
+	require.NoError(t, err)
 
 	// Compute the to-local witness script hash.
 	toLocalScriptHash, err := input.WitnessScriptHash(toLocalScript)
-	require.Nil(t, err)
+	require.NoError(t, err)
 
 	// Compute the to-remote redeem script, witness script hash, and
 	// sequence numbers.
@@ -147,12 +145,12 @@ func testJusticeDescriptor(t *testing.T, blobType blob.Type) {
 		toRemoteRedeemScript, err = input.CommitScriptToRemoteConfirmed(
 			toRemotePK,
 		)
-		require.Nil(t, err)
+		require.NoError(t, err)
 
 		toRemoteScriptHash, err = input.WitnessScriptHash(
 			toRemoteRedeemScript,
 		)
-		require.Nil(t, err)
+		require.NoError(t, err)
 
 		// As it should be.
 		toRemoteSigningScript = toRemoteRedeemScript
@@ -161,7 +159,7 @@ func testJusticeDescriptor(t *testing.T, blobType blob.Type) {
 		toRemoteScriptHash, err = input.CommitScriptUnencumbered(
 			toRemotePK,
 		)
-		require.Nil(t, err)
+		require.NoError(t, err)
 
 		// NOTE: This is the _pkscript_.
 		toRemoteSigningScript = toRemoteScriptHash
@@ -188,26 +186,24 @@ func testJusticeDescriptor(t *testing.T, blobType blob.Type) {
 	// Compute the weight estimate for our justice transaction.
 	var weightEstimate input.TxWeightEstimator
 
-	// An older ToLocalPenaltyWitnessSize constant used to underestimate the
-	// size by one byte. The diferrence in weight can cause different output
-	// values on the sweep transaction, so we mimic the original bug and
-	// create signatures using the original weight estimate. For anchor
-	// channels we fix this and use the correct witness size.
-	if isAnchorChannel {
-		weightEstimate.AddWitnessInput(input.ToLocalPenaltyWitnessSize)
-	} else {
-		weightEstimate.AddWitnessInput(input.ToLocalPenaltyWitnessSize - 1)
-	}
+	// Add the local witness size to the weight estimator.
+	toLocalWitnessSize, err := commitType.ToLocalWitnessSize()
+	require.NoError(t, err)
+	weightEstimate.AddWitnessInput(toLocalWitnessSize)
 
-	if isAnchorChannel {
-		weightEstimate.AddWitnessInput(input.ToRemoteConfirmedWitnessSize)
-	} else {
-		weightEstimate.AddWitnessInput(input.P2WKHWitnessSize)
-	}
+	// Add the remote witness size to the weight estimator.
+	toRemoteWitnessSize, err := commitType.ToRemoteWitnessSize()
+	require.NoError(t, err)
+	weightEstimate.AddWitnessInput(toRemoteWitnessSize)
+
+	// Add the sweep output to the weight estimator.
 	weightEstimate.AddP2WKHOutput()
+
+	// Add the reward output to the weight estimator.
 	if blobType.Has(blob.FlagReward) {
 		weightEstimate.AddP2WKHOutput()
 	}
+
 	txWeight := weightEstimate.Weight()
 
 	// Create a session info so that simulate agreement of the sweep
@@ -263,7 +259,7 @@ func testJusticeDescriptor(t *testing.T, blobType blob.Type) {
 		totalAmount, int64(txWeight), justiceKit.SweepAddress,
 		sessionInfo.RewardAddress,
 	)
-	require.Nil(t, err)
+	require.NoError(t, err)
 
 	// Attach the txouts and BIP69 sort the resulting transaction.
 	justiceTxn.TxOut = outputs

watchtower/wtclient/backup_task.go

@@ -12,7 +12,6 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet"
-	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/blob"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
 )
@@ -37,8 +36,9 @@ import (
 //     necessary components are stripped out and encrypted before being sent to
 //     the tower in a StateUpdate.
 type backupTask struct {
-	id         wtdb.BackupID
-	breachInfo *lnwallet.BreachRetribution
+	id             wtdb.BackupID
+	breachInfo     *lnwallet.BreachRetribution
+	commitmentType blob.CommitmentType
 
 	// state-dependent variables
 
@@ -127,6 +127,11 @@ func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
 		return err
 	}
 
+	commitType, err := session.Policy.BlobType.CommitmentType(&chanType)
+	if err != nil {
+		return err
+	}
+
 	// Parse the non-dust outputs from the breach transaction,
 	// simultaneously computing the total amount contained in the inputs
 	// present. We can't compute the exact output values at this time
@@ -147,48 +152,23 @@ func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
 	// to that output as local, though relative to their commitment, it is
 	// paying to-the-remote party (which is us).
 	if breachInfo.RemoteOutputSignDesc != nil {
-		toLocalInput = input.NewBaseInput(
-			&breachInfo.RemoteOutpoint,
-			input.CommitmentRevoke,
-			breachInfo.RemoteOutputSignDesc,
-			0,
-		)
+		toLocalInput, err = commitType.ToLocalInput(breachInfo)
+		if err != nil {
+			return err
+		}
+
 		totalAmt += breachInfo.RemoteOutputSignDesc.Output.Value
 	}
 	if breachInfo.LocalOutputSignDesc != nil {
-		var witnessType input.WitnessType
-		switch {
-		case chanType.HasAnchors():
-			witnessType = input.CommitmentToRemoteConfirmed
-		case chanType.IsTweakless():
-			witnessType = input.CommitSpendNoDelayTweakless
-		default:
-			witnessType = input.CommitmentNoDelay
-		}
-
-		// Anchor channels have a CSV-encumbered to-remote output. We'll
-		// construct a CSV input in that case and assign the proper CSV
-		// delay of 1, otherwise we fallback to the a regular P2WKH
-		// to-remote output for tweaked or tweakless channels.
-		if chanType.HasAnchors() {
-			toRemoteInput = input.NewCsvInput(
-				&breachInfo.LocalOutpoint,
-				witnessType,
-				breachInfo.LocalOutputSignDesc,
-				0, 1,
-			)
-		} else {
-			toRemoteInput = input.NewBaseInput(
-				&breachInfo.LocalOutpoint,
-				witnessType,
-				breachInfo.LocalOutputSignDesc,
-				0,
-			)
+		toRemoteInput, err = commitType.ToRemoteInput(breachInfo)
+		if err != nil {
+			return err
 		}
 
 		totalAmt += breachInfo.LocalOutputSignDesc.Output.Value
 	}
 
+	t.commitmentType = commitType
 	t.breachInfo = breachInfo
 	t.toLocalInput = toLocalInput
 	t.toRemoteInput = toRemoteInput
@@ -202,34 +182,20 @@ func (t *backupTask) bindSession(session *wtdb.ClientSessionBody,
 	// Next, add the contribution from the inputs that are present on this
 	// breach transaction.
 	if t.toLocalInput != nil {
-		// An older ToLocalPenaltyWitnessSize constant used to
-		// underestimate the size by one byte. The diferrence in weight
-		// can cause different output values on the sweep transaction,
-		// so we mimic the original bug and create signatures using the
-		// original weight estimate. For anchor channels we'll go ahead
-		// an use the correct penalty witness when signing our justice
-		// transactions.
-		if chanType.HasAnchors() {
-			weightEstimate.AddWitnessInput(
-				input.ToLocalPenaltyWitnessSize,
-			)
-		} else {
-			weightEstimate.AddWitnessInput(
-				input.ToLocalPenaltyWitnessSize - 1,
-			)
+		toLocalWitnessSize, err := commitType.ToLocalWitnessSize()
+		if err != nil {
+			return err
 		}
+
+		weightEstimate.AddWitnessInput(toLocalWitnessSize)
 	}
 	if t.toRemoteInput != nil {
-		// Legacy channels (both tweaked and non-tweaked) spend from
-		// P2WKH output. Anchor channels spend a to-remote confirmed
-		// P2WSH  output.
-		if chanType.HasAnchors() {
-			weightEstimate.AddWitnessInput(
-				input.ToRemoteConfirmedWitnessSize,
-			)
-		} else {
-			weightEstimate.AddWitnessInput(input.P2WKHWitnessSize)
+		toRemoteWitnessSize, err := commitType.ToRemoteWitnessSize()
+		if err != nil {
+			return err
 		}
+
+		weightEstimate.AddWitnessInput(toRemoteWitnessSize)
 	}
 
 	// All justice transactions will either use segwit v0 (p2wkh + p2wsh)
@@ -349,6 +315,7 @@ func (t *backupTask) craftSessionPayload(
 	// Now, iterate through the list of inputs that were initially added to
 	// the transaction and store the computed witness within the justice
 	// kit.
+	commitType := t.commitmentType
 	for _, inp := range inputs {
 		// Lookup the input's new post-sort position.
 		i := inputIndex[*inp.OutPoint()]
@@ -361,17 +328,17 @@ func (t *backupTask) craftSessionPayload(
 			return hint, nil, err
 		}
 
-		// Parse the DER-encoded signature from the first position of
-		// the resulting witness. We trim an extra byte to remove the
-		// sighash flag.
-		witness := inputScript.Witness
-		rawSignature := witness[0][:len(witness[0])-1]
+		signature, err := commitType.ParseRawSig(inputScript.Witness)
+		if err != nil {
+			return hint, nil, err
+		}
 
-		// Re-encode the DER signature into a fixed-size 64 byte
-		// signature.
-		signature, err := lnwire.NewSigFromECDSARawSignature(
-			rawSignature,
-		)
+		toLocalWitnessType, err := commitType.ToLocalWitnessType()
+		if err != nil {
+			return hint, nil, err
+		}
+
+		toRemoteWitnessType, err := commitType.ToRemoteWitnessType()
 		if err != nil {
 			return hint, nil, err
 		}
@@ -380,14 +347,9 @@ func (t *backupTask) craftSessionPayload(
 		// using the input's witness type to select the appropriate
 		// field
 		switch inp.WitnessType() {
-		case input.CommitmentRevoke:
+		case toLocalWitnessType:
 			justiceKit.CommitToLocalSig = signature
-
-		case input.CommitSpendNoDelayTweakless:
-			fallthrough
-		case input.CommitmentNoDelay:
-			fallthrough
-		case input.CommitmentToRemoteConfirmed:
+		case toRemoteWitnessType:
 			justiceKit.CommitToRemoteSig = signature
 		default:
 			return hint, nil, fmt.Errorf("invalid witness type: %v",

watchtower/wtclient/backup_task_internal_test.go

@@ -72,6 +72,7 @@ type backupTaskTest struct {
 // corresponding BreachInfo, as well as setting the wtpolicy.Policy of the given
 // session.
 func genTaskTest(
+	t *testing.T,
 	name string,
 	stateNum uint64,
 	toLocalAmt int64,
@@ -91,15 +92,12 @@ func genTaskTest(
 	}
 
 	// Parse the key pairs for all keys used in the test.
-	revSK, revPK := btcec.PrivKeyFromBytes(
-		revPrivBytes,
-	)
-	_, toLocalPK := btcec.PrivKeyFromBytes(
-		toLocalPrivBytes,
-	)
-	toRemoteSK, toRemotePK := btcec.PrivKeyFromBytes(
-		toRemotePrivBytes,
-	)
+	revSK, revPK := btcec.PrivKeyFromBytes(revPrivBytes)
+	_, toLocalPK := btcec.PrivKeyFromBytes(toLocalPrivBytes)
+	toRemoteSK, toRemotePK := btcec.PrivKeyFromBytes(toRemotePrivBytes)
+
+	commitType, err := blobType.CommitmentType(&chanType)
+	require.NoError(t, err)
 
 	// Create the signer, and add the revocation and to-remote privkeys.
 	signer := wtmock.NewMockSigner()
@@ -174,12 +172,9 @@ func genTaskTest(
 			Hash:  txid,
 			Index: index,
 		}
-		toLocalInput = input.NewBaseInput(
-			&breachInfo.RemoteOutpoint,
-			input.CommitmentRevoke,
-			breachInfo.RemoteOutputSignDesc,
-			0,
-		)
+		toLocalInput, err = commitType.ToLocalInput(breachInfo)
+		require.NoError(t, err)
+
 		index++
 	}
 	if toRemoteAmt > 0 {
@@ -188,31 +183,8 @@ func genTaskTest(
 			Index: index,
 		}
 
-		var witnessType input.WitnessType
-		switch {
-		case chanType.HasAnchors():
-			witnessType = input.CommitmentToRemoteConfirmed
-		case chanType.IsTweakless():
-			witnessType = input.CommitSpendNoDelayTweakless
-		default:
-			witnessType = input.CommitmentNoDelay
-		}
-
-		if chanType.HasAnchors() {
-			toRemoteInput = input.NewCsvInput(
-				&breachInfo.LocalOutpoint,
-				witnessType,
-				breachInfo.LocalOutputSignDesc,
-				0, 1,
-			)
-		} else {
-			toRemoteInput = input.NewBaseInput(
-				&breachInfo.LocalOutpoint,
-				witnessType,
-				breachInfo.LocalOutputSignDesc,
-				0,
-			)
-		}
+		toRemoteInput, err = commitType.ToRemoteInput(breachInfo)
+		require.NoError(t, err)
 	}
 
 	return backupTaskTest{
@@ -312,6 +284,7 @@ func TestBackupTask(t *testing.T) {
 
 		backupTaskTests = append(backupTaskTests, []backupTaskTest{
 			genTaskTest(
+				t,
 				"commit no-reward, both outputs",
 				100,                        // stateNum
 				200000,                     // toLocalAmt
@@ -325,6 +298,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit no-reward, to-local output only",
 				1000,                        // stateNum
 				200000,                      // toLocalAmt
@@ -338,6 +312,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit no-reward, to-remote output only",
 				1,                            // stateNum
 				0,                            // toLocalAmt
@@ -351,6 +326,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit no-reward, to-remote output only, creates dust",
 				1,                              // stateNum
 				0,                              // toLocalAmt
@@ -364,6 +340,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit no-reward, no outputs, fee rate exceeds inputs",
 				300,                          // stateNum
 				0,                            // toLocalAmt
@@ -377,6 +354,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit no-reward, no outputs, fee rate of 0 creates dust",
 				300,                     // stateNum
 				0,                       // toLocalAmt
@@ -390,6 +368,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit reward, both outputs",
 				100,                      // stateNum
 				200000,                   // toLocalAmt
@@ -403,6 +382,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit reward, to-local output only",
 				1000,                      // stateNum
 				200000,                    // toLocalAmt
@@ -416,6 +396,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit reward, to-remote output only",
 				1,                          // stateNum
 				0,                          // toLocalAmt
@@ -429,6 +410,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit reward, to-remote output only, creates dust",
 				1,                            // stateNum
 				0,                            // toLocalAmt
@@ -442,6 +424,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit reward, no outputs, fee rate exceeds inputs",
 				300,                          // stateNum
 				0,                            // toLocalAmt
@@ -455,6 +438,7 @@ func TestBackupTask(t *testing.T) {
 				chanType,
 			),
 			genTaskTest(
+				t,
 				"commit reward, no outputs, fee rate of 0 creates dust",
 				300,                     // stateNum
 				0,                       // toLocalAmt