record: add TLV encoding/decoding for blinded route data blobs

This commit adds encoding and decoding for blinded route data blobs.
TLV fields such as path_id (which are only used for the final hop)
are omitted to minimize the change size.

record/blinded_data_test.go

@@ -0,0 +1,197 @@
+package record
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"math"
+	"testing"
+
+	"github.com/btcsuite/btcd/btcec/v2"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/stretchr/testify/require"
+)
+
+//nolint:lll
+const pubkeyStr = "02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619"
+
+func pubkey(t *testing.T) *btcec.PublicKey {
+	t.Helper()
+
+	nodeBytes, err := hex.DecodeString(pubkeyStr)
+	require.NoError(t, err)
+
+	nodePk, err := btcec.ParsePubKey(nodeBytes)
+	require.NoError(t, err)
+
+	return nodePk
+}
+
+// TestBlindedDataEncoding tests encoding and decoding of blinded data blobs.
+// These tests specifically cover cases where the variable length encoded
+// integers values have different numbers of leading zeros trimmed because
+// these TLVs are the first composite records with variable length tlvs
+// (previously, a variable length integer would take up the whole record).
+func TestBlindedDataEncoding(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name        string
+		baseFee     uint32
+		htlcMin     lnwire.MilliSatoshi
+		features    *lnwire.FeatureVector
+		constraints bool
+	}{
+		{
+			name:    "zero variable values",
+			baseFee: 0,
+			htlcMin: 0,
+		},
+		{
+			name:    "zeros trimmed",
+			baseFee: math.MaxUint32 / 2,
+			htlcMin: math.MaxUint64 / 2,
+		},
+		{
+			name:    "no zeros trimmed",
+			baseFee: math.MaxUint32,
+			htlcMin: math.MaxUint64,
+		},
+		{
+			name:     "nil feature vector",
+			features: nil,
+		},
+		{
+			name:     "non-nil, but empty feature vector",
+			features: lnwire.EmptyFeatureVector(),
+		},
+		{
+			name: "populated feature vector",
+			features: lnwire.NewFeatureVector(
+				lnwire.NewRawFeatureVector(lnwire.AMPOptional),
+				lnwire.Features,
+			),
+		},
+		{
+			name:        "no payment constraints",
+			constraints: true,
+		},
+	}
+
+	for _, testCase := range tests {
+		testCase := testCase
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Create a standard set of blinded route data, using
+			// the values from our test case for the variable
+			// length encoded values.
+			channelID := lnwire.NewShortChanIDFromInt(1)
+			info := PaymentRelayInfo{
+				FeeRate:         2,
+				CltvExpiryDelta: 3,
+				BaseFee:         testCase.baseFee,
+			}
+
+			var constraints *PaymentConstraints
+			if testCase.constraints {
+				constraints = &PaymentConstraints{
+					MaxCltvExpiry:   4,
+					HtlcMinimumMsat: testCase.htlcMin,
+				}
+			}
+
+			encodedData := NewBlindedRouteData(
+				channelID, pubkey(t), info, constraints,
+				testCase.features,
+			)
+
+			encoded, err := EncodeBlindedRouteData(encodedData)
+			require.NoError(t, err)
+
+			b := bytes.NewBuffer(encoded)
+			decodedData, err := DecodeBlindedRouteData(b)
+			require.NoError(t, err)
+
+			require.Equal(t, encodedData, decodedData)
+		})
+	}
+}
+
+// TestBlindedRouteVectors tests encoding/decoding of the test vectors for
+// blinded route data provided in the specification.
+//
+//nolint:lll
+func TestBlindingSpecTestVectors(t *testing.T) {
+	nextBlindingOverrideStr, err := hex.DecodeString("031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f")
+	require.NoError(t, err)
+	nextBlindingOverride, err := btcec.ParsePubKey(nextBlindingOverrideStr)
+	require.NoError(t, err)
+
+	tests := []struct {
+		encoded             string
+		expectedPaymentData *BlindedRouteData
+	}{
+		{
+			encoded: "011a0000000000000000000000000000000000000000000000000000020800000000000006c10a0800240000009627100c06000b69e505dc0e00fd023103123456",
+			expectedPaymentData: NewBlindedRouteData(
+				lnwire.ShortChannelID{
+					BlockHeight: 0,
+					TxIndex:     0,
+					TxPosition:  1729,
+				},
+				nil,
+				PaymentRelayInfo{
+					CltvExpiryDelta: 36,
+					FeeRate:         150,
+					BaseFee:         10000,
+				},
+				&PaymentConstraints{
+					MaxCltvExpiry:   748005,
+					HtlcMinimumMsat: 1500,
+				},
+				lnwire.NewFeatureVector(
+					lnwire.NewRawFeatureVector(),
+					lnwire.Features,
+				),
+			),
+		},
+		{
+			encoded: "020800000000000004510821031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f0a0800300000006401f40c06000b69c105dc0e00",
+			expectedPaymentData: NewBlindedRouteData(
+				lnwire.ShortChannelID{
+					TxPosition: 1105,
+				},
+				nextBlindingOverride,
+				PaymentRelayInfo{
+					CltvExpiryDelta: 48,
+					FeeRate:         100,
+					BaseFee:         500,
+				},
+				&PaymentConstraints{
+					MaxCltvExpiry:   747969,
+					HtlcMinimumMsat: 1500,
+				},
+				lnwire.NewFeatureVector(
+					lnwire.NewRawFeatureVector(),
+					lnwire.Features,
+				)),
+		},
+	}
+
+	for i, test := range tests {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			route, err := hex.DecodeString(test.encoded)
+			require.NoError(t, err)
+
+			buff := bytes.NewBuffer(route)
+
+			decodedRoute, err := DecodeBlindedRouteData(buff)
+			require.NoError(t, err)
+
+			require.Equal(
+				t, test.expectedPaymentData, decodedRoute,
+			)
+		})
+	}
+}