Add Support for P2TR Fallback Addresses in BOLT-11

docs/release-notes/release-notes-0.20.0.md

@@ -55,6 +55,9 @@ when the appropriate TLV flag is set. This allows for HTLCs carrying metadata to
 reflect their state on the channel commitment without having to send or receive
 a certain amount of msats.
 
+- Added support for [P2TR Fallback Addresses](
+  https://github.com/lightningnetwork/lnd/pull/9975) in BOLT-11 invoices.
+
 ## Functional Enhancements
 * [Add](https://github.com/lightningnetwork/lnd/pull/9677)
   `ConfirmationsUntilActive` and `ConfirmationHeight` field to the

zpay32/decode.go

@@ -15,10 +15,18 @@ import (
 	"github.com/btcsuite/btcd/btcutil/bech32"
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
+	"github.com/btcsuite/btcd/txscript"
 	"github.com/lightningnetwork/lnd/fn/v2"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
+const (
+	fallbackVersionWitness    = txscript.BaseSegwitWitnessVersion
+	fallbackVersionTaproot    = txscript.TaprootWitnessVersion
+	fallbackVersionPubkeyHash = 17
+	fallbackVersionScriptHash = 18
+)
+
 var (
 	// ErrInvalidUTF8Description is returned if the invoice description is
 	// not valid UTF-8.
@@ -529,7 +537,7 @@ func parseFallbackAddr(data []byte, net *chaincfg.Params) (btcutil.Address, erro
 
 	version := data[0]
 	switch version {
-	case 0:
+	case fallbackVersionWitness:
 		witness, err := bech32.ConvertBits(data[1:], 5, 8, false)
 		if err != nil {
 			return nil, err
@@ -548,7 +556,16 @@ func parseFallbackAddr(data []byte, net *chaincfg.Params) (btcutil.Address, erro
 		if err != nil {
 			return nil, err
 		}
-	case 17:
+	case fallbackVersionTaproot:
+		witness, err := bech32.ConvertBits(data[1:], 5, 8, false)
+		if err != nil {
+			return nil, err
+		}
+		addr, err = btcutil.NewAddressTaproot(witness, net)
+		if err != nil {
+			return nil, err
+		}
+	case fallbackVersionPubkeyHash:
 		pubKeyHash, err := bech32.ConvertBits(data[1:], 5, 8, false)
 		if err != nil {
 			return nil, err
@@ -558,7 +575,7 @@ func parseFallbackAddr(data []byte, net *chaincfg.Params) (btcutil.Address, erro
 		if err != nil {
 			return nil, err
 		}
-	case 18:
+	case fallbackVersionScriptHash:
 		scriptHash, err := bech32.ConvertBits(data[1:], 5, 8, false)
 		if err != nil {
 			return nil, err

zpay32/encode.go

@@ -202,13 +202,15 @@ func writeTaggedFields(bufferBase32 *bytes.Buffer, invoice *Invoice) error {
 		var version byte
 		switch addr := invoice.FallbackAddr.(type) {
 		case *btcutil.AddressPubKeyHash:
-			version = 17
+			version = fallbackVersionPubkeyHash
 		case *btcutil.AddressScriptHash:
-			version = 18
+			version = fallbackVersionScriptHash
 		case *btcutil.AddressWitnessPubKeyHash:
 			version = addr.WitnessVersion()
 		case *btcutil.AddressWitnessScriptHash:
 			version = addr.WitnessVersion()
+		case *btcutil.AddressTaproot:
+			version = addr.WitnessVersion()
 		default:
 			return fmt.Errorf("unknown fallback address type")
 		}

zpay32/invoice_internal_test.go

@@ -593,19 +593,34 @@ func TestParseFallbackAddr(t *testing.T) {
 	t.Parallel()
 
 	testAddrTestnetData, _ := bech32.ConvertBits(testAddrTestnet.ScriptAddress(), 8, 5, true)
-	testAddrTestnetDataWithVersion := append([]byte{17}, testAddrTestnetData...)
+	testAddrTestnetDataWithVersion := append(
+		[]byte{fallbackVersionPubkeyHash}, testAddrTestnetData...,
+	)
 
 	testRustyAddrData, _ := bech32.ConvertBits(testRustyAddr.ScriptAddress(), 8, 5, true)
-	testRustyAddrDataWithVersion := append([]byte{17}, testRustyAddrData...)
+	testRustyAddrDataWithVersion := append(
+		[]byte{fallbackVersionPubkeyHash}, testRustyAddrData...,
+	)
 
 	testAddrMainnetP2SHData, _ := bech32.ConvertBits(testAddrMainnetP2SH.ScriptAddress(), 8, 5, true)
-	testAddrMainnetP2SHDataWithVersion := append([]byte{18}, testAddrMainnetP2SHData...)
+	testAddrMainnetP2SHDataWithVersion := append(
+		[]byte{fallbackVersionScriptHash}, testAddrMainnetP2SHData...,
+	)
 
 	testAddrMainnetP2WPKHData, _ := bech32.ConvertBits(testAddrMainnetP2WPKH.ScriptAddress(), 8, 5, true)
-	testAddrMainnetP2WPKHDataWithVersion := append([]byte{0}, testAddrMainnetP2WPKHData...)
+	testAddrMainnetP2WPKHDataWithVersion := append(
+		[]byte{fallbackVersionWitness}, testAddrMainnetP2WPKHData...,
+	)
 
 	testAddrMainnetP2WSHData, _ := bech32.ConvertBits(testAddrMainnetP2WSH.ScriptAddress(), 8, 5, true)
-	testAddrMainnetP2WSHDataWithVersion := append([]byte{0}, testAddrMainnetP2WSHData...)
+	testAddrMainnetP2WSHDataWithVersion := append(
+		[]byte{fallbackVersionWitness}, testAddrMainnetP2WSHData...,
+	)
+
+	testAddrMainnetP2TRData, _ := bech32.ConvertBits(
+		testAddrMainnetP2TR.ScriptAddress(), 8, 5, true)
+	testAddrMainnetP2TRDataWithVersion := append(
+		[]byte{fallbackVersionTaproot}, testAddrMainnetP2TRData...)
 
 	tests := []struct {
 		data   []byte
@@ -651,6 +666,17 @@ func TestParseFallbackAddr(t *testing.T) {
 			valid:  true,
 			result: testAddrMainnetP2WSH,
 		},
+		{
+			data:   testAddrMainnetP2TRDataWithVersion,
+			net:    &chaincfg.MainNetParams,
+			valid:  true,
+			result: testAddrMainnetP2TR,
+		},
+		{
+			data:  testAddrMainnetP2TRDataWithVersion[:10],
+			net:   &chaincfg.MainNetParams,
+			valid: false, // data too short for P2TR address
+		},
 	}
 
 	for i, test := range tests {

zpay32/invoice_test.go

@@ -71,6 +71,9 @@ var (
 	testAddrMainnetP2SH, _   = btcutil.DecodeAddress("3EktnHQD7RiAE6uzMj2ZifT9YgRrkSgzQX", &chaincfg.MainNetParams)
 	testAddrMainnetP2WPKH, _ = btcutil.DecodeAddress("bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4", &chaincfg.MainNetParams)
 	testAddrMainnetP2WSH, _  = btcutil.DecodeAddress("bc1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3qccfmv3", &chaincfg.MainNetParams)
+	testAddrMainnetP2TR, _   = btcutil.DecodeAddress("bc1pptdvg0d2nj99568"+
+		"qn6ssdy4cygnwuxgw2ukmnwgwz7jpqjz2kszse2s3lm",
+		&chaincfg.MainNetParams)
 
 	testHopHintPubkeyBytes1, _ = hex.DecodeString("029e03a901b85534ff1e92c43c74431f7ce72046060fcf7a95c37e148f78c77255")
 	testHopHintPubkey1, _      = btcec.ParsePubKey(testHopHintPubkeyBytes1)
@@ -299,8 +302,14 @@ func TestDecodeEncode(t *testing.T) {
 		},
 		{
 			// Ignore unknown witness version in fallback address.
-			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrqsfpppw508d6qejxtdg4y5r3zarvary0c5xw7k8txqv6x0a75xuzp0zsdzk5hq6tmfgweltvs6jk5nhtyd9uqksvr48zga9mw08667w8264gkspluu66jhtcmct36nx363km6cquhhv2cpc6q43r",
-			valid:          true,
+			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqq" +
+				"qsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan" +
+				"79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrq" +
+				"sfp4z6yn92zrp97a6q5hhh8swys7uf4hm9tr8a0xylnk" +
+				"26fvkg3jx0sdsxvma0zvf2h0pycyyzdrmjncq6lzrfuw" +
+				"xfhv6gzz4q5303n3up6as4ghe5qthg7x20z7vae8w5rq" +
+				"u6de3g4jl7kvuap3qedprqsqqmgqqm6s8sl",
+			valid: true,
 			decodedInvoice: func() *Invoice {
 				return &Invoice{
 					Net:             &chaincfg.MainNetParams,
@@ -649,6 +658,74 @@ func TestDecodeEncode(t *testing.T) {
 				i.Destination = nil
 			},
 		},
+		{
+			// On mainnet, with fallback (p2tr) address "bc1pptdvg0d
+			// 2nj99568qn6ssdy4cygnwuxgw2ukmnwgwz7jpqjz2kszse2s3lm"
+			encodedInvoice: "lnbc20m1pvjluezpp5qqqsyqcyq5rqwzqfqq" +
+				"qsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqypqhp58yjmdan" +
+				"79s6qqdhdzgynm4zwqd5d7xmw5fk98klysy043l2ahrq" +
+				"sfp4pptdvg0d2nj99568qn6ssdy4cygnwuxgw2ukmnwg" +
+				"wz7jpqjz2kszs9zs3tmcpgulwc0ruwc2cm97udy6sdfe" +
+				"nwvha8qlkfwx49sgk40kze4kwsh706rae3uc30ltpwpw" +
+				"mjyhc3uan4ljz56wksg5gsnhrrhcqsrq93d",
+
+			valid: true,
+			decodedInvoice: func() *Invoice {
+				return &Invoice{
+					Net:             &chaincfg.MainNetParams,
+					MilliSat:        &testMillisat20mBTC,
+					Timestamp:       time.Unix(1496314658, 0),
+					PaymentHash:     &testPaymentHash,
+					DescriptionHash: &testDescriptionHash,
+					Destination:     testPubKey,
+					FallbackAddr:    testAddrMainnetP2TR,
+					Features:        emptyFeatures,
+				}
+			},
+			beforeEncoding: func(i *Invoice) {
+				// Since this destination pubkey was recovered
+				// from the signature, we must set it nil before
+				// encoding to get back the same invoice string.
+				i.Destination = nil
+			},
+		},
+		{
+			// On mainnet, with fallback (p2tr) address "bc1pptdvg0d
+			// 2nj99568qn6ssdy4cygnwuxgw2ukmnwgwz7jpqjz2kszse2s3lm"
+			// using the test vector payment from BOLT 11
+			encodedInvoice: "lnbc20m1pvjluezsp5zyg3zyg3zyg3zyg3zy" +
+				"g3zyg3zyg3zyg3zyg3zyg3zyg3zyg3zygspp5qqqsyqc" +
+				"yq5rqwzqfqqqsyqcyq5rqwzqfqqqsyqcyq5rqwzqfqyp" +
+				"qhp58yjmdan79s6qqdhdzgynm4zwqd5d7xmw5fk98kly" +
+				"sy043l2ahrqsfp4pptdvg0d2nj99568qn6ssdy4cygnw" +
+				"uxgw2ukmnwgwz7jpqjz2kszs9qrsgqy606dznq28exny" +
+				"dt2r4c29y56xjtn3sk4mhgjtl4pg2y4ar3249rq4ajlm" +
+				"j9jy8zvlzw7cr8mggqzm842xfr0v72rswzq9xvr4hknf" +
+				"sqwmn6xd",
+
+			valid: true,
+			decodedInvoice: func() *Invoice {
+				return &Invoice{
+					Net:             &chaincfg.MainNetParams,
+					MilliSat:        &testMillisat20mBTC,
+					Timestamp:       time.Unix(1496314658, 0),
+					PaymentHash:     &testPaymentHash,
+					DescriptionHash: &testDescriptionHash,
+					Destination:     testPubKey,
+					FallbackAddr:    testAddrMainnetP2TR,
+					Features: lnwire.NewFeatureVector(
+						lnwire.NewRawFeatureVector(
+							8, 14,
+						),
+						lnwire.Features,
+					),
+					PaymentAddr: fn.Some(specPaymentAddr),
+				}
+			},
+			// Skip encoding since LND encode the tagged fields
+			// in a different order.
+			skipEncoding: true,
+		},
 		{
 			// Send 2500uBTC for a cup of coffee with a custom CLTV
 			// expiry value.