watchtower: support taproot channel commitments

cmd/lncli/wtclient.go

@@ -284,8 +284,14 @@ var policyCommand = cli.Command{
 				"policy. (default)",
 		},
 		cli.BoolFlag{
-			Name:  "anchor",
-			Usage: "Retrieve the anchor tower client's current policy.",
+			Name: "anchor",
+			Usage: "Retrieve the anchor tower client's current " +
+				"policy.",
+		},
+		cli.BoolFlag{
+			Name: "taproot",
+			Usage: "Retrieve the taproot tower client's current " +
+				"policy.",
 		},
 	},
 }
@@ -305,6 +311,8 @@ func policy(ctx *cli.Context) error {
 		policyType = wtclientrpc.PolicyType_ANCHOR
 	case ctx.Bool("legacy"):
 		policyType = wtclientrpc.PolicyType_LEGACY
+	case ctx.Bool("taproot"):
+		policyType = wtclientrpc.PolicyType_TAPROOT
 
 	// For backwards compatibility with original rpc behavior.
 	default:

docs/release-notes/release-notes-0.18.0.md

@@ -85,7 +85,13 @@
   control to [handle pathfinding errors](https://github.com/lightningnetwork/lnd/pull/8095)
   for blinded paths are also included.
 * A new config value,
-  [http-header-timeout](https://github.com/lightningnetwork/lnd/pull/7715), is added so users can specify the amount of time the http server will wait for a request to complete before closing the connection. The default value is 5 seconds.
+  [http-header-timeout](https://github.com/lightningnetwork/lnd/pull/7715), is 
+  added so users can specify the amount of time the http server will wait for a 
+  request to complete before closing the connection. The default value is 5 
+  seconds.
+* Update [watchtowers to be Taproot
+  ready](https://github.com/lightningnetwork/lnd/pull/7733)
+
 
 * [`routerrpc.usestatusinitiated` is
   introduced](https://github.com/lightningnetwork/lnd/pull/8177) to signal that
@@ -190,7 +196,7 @@
 * [Add a watchtower tower client
   multiplexer](https://github.com/lightningnetwork/lnd/pull/7702) to manage
   tower clients of different types.
- 
+
 * [Introduce CommitmentType and JusticeKit
   interface](https://github.com/lightningnetwork/lnd/pull/7736) to simplify the
   code. 

input/script_utils.go

@@ -2124,27 +2124,14 @@ func NewLocalCommitScriptTree(csvTimeout uint32,
 
 	// First, we'll need to construct the tapLeaf that'll be our delay CSV
 	// clause.
-	builder := txscript.NewScriptBuilder()
-	builder.AddData(schnorr.SerializePubKey(selfKey))
-	builder.AddOp(txscript.OP_CHECKSIG)
-	builder.AddInt64(int64(csvTimeout))
-	builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY)
-	builder.AddOp(txscript.OP_DROP)
-
-	delayScript, err := builder.Script()
+	delayScript, err := TaprootLocalCommitDelayScript(csvTimeout, selfKey)
 	if err != nil {
 		return nil, err
 	}
 
 	// Next, we'll need to construct the revocation path, which is just a
 	// simple checksig script.
-	builder = txscript.NewScriptBuilder()
-	builder.AddData(schnorr.SerializePubKey(selfKey))
-	builder.AddOp(txscript.OP_DROP)
-	builder.AddData(schnorr.SerializePubKey(revokeKey))
-	builder.AddOp(txscript.OP_CHECKSIG)
-
-	revokeScript, err := builder.Script()
+	revokeScript, err := TaprootLocalCommitRevokeScript(selfKey, revokeKey)
 	if err != nil {
 		return nil, err
 	}
@@ -2176,6 +2163,35 @@ func NewLocalCommitScriptTree(csvTimeout uint32,
 	}, nil
 }
 
+// TaprootLocalCommitDelayScript builds the tap leaf with the CSV delay script
+// for the to-local output.
+func TaprootLocalCommitDelayScript(csvTimeout uint32,
+	selfKey *btcec.PublicKey) ([]byte, error) {
+
+	builder := txscript.NewScriptBuilder()
+	builder.AddData(schnorr.SerializePubKey(selfKey))
+	builder.AddOp(txscript.OP_CHECKSIG)
+	builder.AddInt64(int64(csvTimeout))
+	builder.AddOp(txscript.OP_CHECKSEQUENCEVERIFY)
+	builder.AddOp(txscript.OP_DROP)
+
+	return builder.Script()
+}
+
+// TaprootLocalCommitRevokeScript builds the tap leaf with the revocation path
+// for the to-local output.
+func TaprootLocalCommitRevokeScript(selfKey, revokeKey *btcec.PublicKey) (
+	[]byte, error) {
+
+	builder := txscript.NewScriptBuilder()
+	builder.AddData(schnorr.SerializePubKey(selfKey))
+	builder.AddOp(txscript.OP_DROP)
+	builder.AddData(schnorr.SerializePubKey(revokeKey))
+	builder.AddOp(txscript.OP_CHECKSIG)
+
+	return builder.Script()
+}
+
 // TaprootCommitScriptToSelf creates the taproot witness program that commits
 // to the revocation (script path) and delay path (script path) in a single
 // taproot output key. Both the delay script and the revocation script are part

itest/lnd_revocation_test.go

@@ -715,30 +715,24 @@ func testRevokedCloseRetributionRemoteHodl(ht *lntest.HarnessTest) {
 // asserts that Willy responds by broadcasting the justice transaction on
 // Carol's behalf sweeping her funds without a reward.
 func testRevokedCloseRetributionAltruistWatchtower(ht *lntest.HarnessTest) {
-	testCases := []struct {
-		name    string
-		anchors bool
-	}{{
-		name:    "anchors",
-		anchors: true,
-	}, {
-		name:    "legacy",
-		anchors: false,
-	}}
-
-	for _, tc := range testCases {
-		tc := tc
+	for _, commitType := range []lnrpc.CommitmentType{
+		lnrpc.CommitmentType_LEGACY,
+		lnrpc.CommitmentType_ANCHORS,
+		lnrpc.CommitmentType_SIMPLE_TAPROOT,
+	} {
+		testName := fmt.Sprintf("%v", commitType.String())
+		ct := commitType
 		testFunc := func(ht *lntest.HarnessTest) {
 			testRevokedCloseRetributionAltruistWatchtowerCase(
-				ht, tc.anchors,
+				ht, ct,
 			)
 		}
 
-		success := ht.Run(tc.name, func(tt *testing.T) {
+		success := ht.Run(testName, func(tt *testing.T) {
 			st := ht.Subtest(tt)
 
 			st.RunTestCase(&lntest.TestCase{
-				Name:     tc.name,
+				Name:     testName,
 				TestFunc: testFunc,
 			})
 		})
@@ -756,7 +750,7 @@ func testRevokedCloseRetributionAltruistWatchtower(ht *lntest.HarnessTest) {
 }
 
 func testRevokedCloseRetributionAltruistWatchtowerCase(ht *lntest.HarnessTest,
-	anchors bool) {
+	commitType lnrpc.CommitmentType) {
 
 	const (
 		chanAmt     = funding.MaxBtcFundingAmount
@@ -767,18 +761,19 @@ func testRevokedCloseRetributionAltruistWatchtowerCase(ht *lntest.HarnessTest,
 
 	// Since we'd like to test some multi-hop failure scenarios, we'll
 	// introduce another node into our test network: Carol.
-	carolArgs := []string{"--hodl.exit-settle"}
-	if anchors {
-		carolArgs = append(carolArgs, "--protocol.anchors")
-	}
+	carolArgs := lntest.NodeArgsForCommitType(commitType)
+	carolArgs = append(carolArgs, "--hodl.exit-settle")
+
 	carol := ht.NewNode("Carol", carolArgs)
 
 	// Willy the watchtower will protect Dave from Carol's breach. He will
 	// remain online in order to punish Carol on Dave's behalf, since the
 	// breach will happen while Dave is offline.
 	willy := ht.NewNode(
-		"Willy", []string{"--watchtower.active",
-			"--watchtower.externalip=" + externalIP},
+		"Willy", []string{
+			"--watchtower.active",
+			"--watchtower.externalip=" + externalIP,
+		},
 	)
 
 	willyInfo := willy.RPC.GetInfoWatchtower()
@@ -801,13 +796,8 @@ func testRevokedCloseRetributionAltruistWatchtowerCase(ht *lntest.HarnessTest,
 	// Dave will be the breached party. We set --nolisten to ensure Carol
 	// won't be able to connect to him and trigger the channel data
 	// protection logic automatically.
-	daveArgs := []string{
-		"--nolisten",
-		"--wtclient.active",
-	}
-	if anchors {
-		daveArgs = append(daveArgs, "--protocol.anchors")
-	}
+	daveArgs := lntest.NodeArgsForCommitType(commitType)
+	daveArgs = append(daveArgs, "--nolisten", "--wtclient.active")
 	dave := ht.NewNode("Dave", daveArgs)
 
 	addTowerReq := &wtclientrpc.AddTowerRequest{
@@ -833,8 +823,10 @@ func testRevokedCloseRetributionAltruistWatchtowerCase(ht *lntest.HarnessTest,
 	// closure by Carol, we'll first open up a channel between them with a
 	// 0.5 BTC value.
 	params := lntest.OpenChannelParams{
-		Amt:     3 * (chanAmt / 4),
-		PushAmt: chanAmt / 4,
+		Amt:            3 * (chanAmt / 4),
+		PushAmt:        chanAmt / 4,
+		CommitmentType: commitType,
+		Private:        true,
 	}
 	chanPoint := ht.OpenChannel(dave, carol, params)
 
@@ -956,7 +948,7 @@ func testRevokedCloseRetributionAltruistWatchtowerCase(ht *lntest.HarnessTest,
 		willyBalResp := willy.RPC.WalletBalance()
 
 		if willyBalResp.ConfirmedBalance != 0 {
-			return fmt.Errorf("Expected Willy to have no funds "+
+			return fmt.Errorf("expected Willy to have no funds "+
 				"after justice transaction was mined, found %v",
 				willyBalResp)
 		}
@@ -994,7 +986,7 @@ func testRevokedCloseRetributionAltruistWatchtowerCase(ht *lntest.HarnessTest,
 	ht.AssertNumPendingForceClose(dave, 0)
 
 	// If this is an anchor channel, Dave would sweep the anchor.
-	if anchors {
+	if lntest.CommitTypeHasAnchors(commitType) {
 		ht.MineBlocksAndAssertNumTxes(1, 1)
 	}
 

lnrpc/wtclientrpc/wtclient.go

@@ -273,9 +273,9 @@ func (c *WatchtowerClient) ListTowers(ctx context.Context,
 	// for the legacy client to the existing tower.
 	rpcTowers := make(map[wtdb.TowerID]*Tower)
 	for blobType, towers := range towersPerBlobType {
-		policyType := PolicyType_LEGACY
-		if blobType.IsAnchorChannel() {
-			policyType = PolicyType_ANCHOR
+		policyType, err := blobTypeToPolicyType(blobType)
+		if err != nil {
+			return nil, err
 		}
 
 		for _, tower := range towers {
@@ -331,9 +331,9 @@ func (c *WatchtowerClient) GetTowerInfo(ctx context.Context,
 
 	var resTower *Tower
 	for blobType, tower := range towersPerBlobType {
-		policyType := PolicyType_LEGACY
-		if blobType.IsAnchorChannel() {
-			policyType = PolicyType_ANCHOR
+		policyType, err := blobTypeToPolicyType(blobType)
+		if err != nil {
+			return nil, err
 		}
 
 		rpcTower := marshallTower(
@@ -437,15 +437,9 @@ func (c *WatchtowerClient) Policy(ctx context.Context,
 		return nil, err
 	}
 
-	var blobType blob.Type
-	switch req.PolicyType {
-	case PolicyType_LEGACY:
-		blobType = blob.TypeAltruistCommit
-	case PolicyType_ANCHOR:
-		blobType = blob.TypeAltruistAnchorCommit
-	default:
-		return nil, fmt.Errorf("unknown policy type: %v",
-			req.PolicyType)
+	blobType, err := policyTypeToBlobType(req.PolicyType)
+	if err != nil {
+		return nil, err
 	}
 
 	policy, err := c.cfg.ClientMgr.Policy(blobType)
@@ -525,3 +519,35 @@ func marshallTower(tower *wtclient.RegisteredTower, policyType PolicyType,
 
 	return rpcTower
 }
+
+func blobTypeToPolicyType(t blob.Type) (PolicyType, error) {
+	switch t {
+	case blob.TypeAltruistTaprootCommit:
+		return PolicyType_TAPROOT, nil
+
+	case blob.TypeAltruistAnchorCommit:
+		return PolicyType_ANCHOR, nil
+
+	case blob.TypeAltruistCommit:
+		return PolicyType_LEGACY, nil
+
+	default:
+		return 0, fmt.Errorf("unknown blob type: %s", t)
+	}
+}
+
+func policyTypeToBlobType(t PolicyType) (blob.Type, error) {
+	switch t {
+	case PolicyType_TAPROOT:
+		return blob.TypeAltruistTaprootCommit, nil
+
+	case PolicyType_ANCHOR:
+		return blob.TypeAltruistAnchorCommit, nil
+
+	case PolicyType_LEGACY:
+		return blob.TypeAltruistCommit, nil
+
+	default:
+		return 0, fmt.Errorf("unknown policy type: %s", t)
+	}
+}