[1/3]: Preparatory work for Forwarding Blinded Routes

channeldb/channel.go

@@ -35,6 +35,10 @@ const (
 	// begins to be interpreted as an absolute block height, rather than a
 	// relative one.
 	AbsoluteThawHeightThreshold uint32 = 500000
+
+	// HTLCBlindingPointTLV is the tlv type used for storing blinding
+	// points with HTLCs.
+	HTLCBlindingPointTLV tlv.Type = 0
 )
 
 var (
@@ -2316,7 +2320,56 @@ type HTLC struct {
 	// Note that this extra data is stored inline with the OnionBlob for
 	// legacy reasons, see serialization/deserialization functions for
 	// detail.
-	ExtraData []byte
+	ExtraData lnwire.ExtraOpaqueData
+
+	// BlindingPoint is an optional blinding point included with the HTLC.
+	//
+	// Note: this field is not a part of on-disk representation of the
+	// HTLC. It is stored in the ExtraData field, which is used to store
+	// a TLV stream of additional information associated with the HTLC.
+	BlindingPoint lnwire.BlindingPointRecord
+}
+
+// serializeExtraData encodes a TLV stream of extra data to be stored with a
+// HTLC. It uses the update_add_htlc TLV types, because this is where extra
+// data is passed with a HTLC. At present blinding points are the only extra
+// data that we will store, and the function is a no-op if a nil blinding
+// point is provided.
+//
+// This function MUST be called to persist all HTLC values when they are
+// serialized.
+func (h *HTLC) serializeExtraData() error {
+	var records []tlv.RecordProducer
+	h.BlindingPoint.WhenSome(func(b tlv.RecordT[lnwire.BlindingPointTlvType,
+		*btcec.PublicKey]) {
+
+		records = append(records, &b)
+	})
+
+	return h.ExtraData.PackRecords(records...)
+}
+
+// deserializeExtraData extracts TLVs from the extra data persisted for the
+// htlc and populates values in the struct accordingly.
+//
+// This function MUST be called to populate the struct properly when HTLCs
+// are deserialized.
+func (h *HTLC) deserializeExtraData() error {
+	if len(h.ExtraData) == 0 {
+		return nil
+	}
+
+	blindingPoint := h.BlindingPoint.Zero()
+	tlvMap, err := h.ExtraData.ExtractRecords(&blindingPoint)
+	if err != nil {
+		return err
+	}
+
+	if val, ok := tlvMap[h.BlindingPoint.TlvType()]; ok && val == nil {
+		h.BlindingPoint = tlv.SomeRecordT(blindingPoint)
+	}
+
+	return nil
 }
 
 // SerializeHtlcs writes out the passed set of HTLC's into the passed writer
@@ -2340,6 +2393,12 @@ func SerializeHtlcs(b io.Writer, htlcs ...HTLC) error {
 	}
 
 	for _, htlc := range htlcs {
+		// Populate TLV stream for any additional fields contained
+		// in the TLV.
+		if err := htlc.serializeExtraData(); err != nil {
+			return err
+		}
+
 		// The onion blob and hltc data are stored as a single var
 		// bytes blob.
 		onionAndExtraData := make(
@@ -2425,6 +2484,12 @@ func DeserializeHtlcs(r io.Reader) ([]HTLC, error) {
 				onionAndExtraData[lnwire.OnionPacketSize:],
 			)
 		}
+
+		// Finally, deserialize any TLVs contained in that extra data
+		// if they are present.
+		if err := htlcs[i].deserializeExtraData(); err != nil {
+			return nil, err
+		}
 	}
 
 	return htlcs, nil

channeldb/channel_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/lightningnetwork/lnd/lntest/channels"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/shachain"
+	"github.com/lightningnetwork/lnd/tlv"
 	"github.com/stretchr/testify/require"
 )
 
@@ -1606,9 +1607,25 @@ func TestHTLCsExtraData(t *testing.T) {
 		OnionBlob:     lnmock.MockOnion(),
 	}
 
+	// Add a blinding point to a htlc.
+	blindingPointHTLC := HTLC{
+		Signature:     testSig.Serialize(),
+		Incoming:      false,
+		Amt:           10,
+		RHash:         key,
+		RefundTimeout: 1,
+		OnionBlob:     lnmock.MockOnion(),
+		BlindingPoint: tlv.SomeRecordT(
+			tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](
+				pubKey,
+			),
+		),
+	}
+
 	testCases := []struct {
-		name  string
-		htlcs []HTLC
+		name        string
+		htlcs       []HTLC
+		blindingIdx int
 	}{
 		{
 			// Serialize multiple HLTCs with no extra data to
@@ -1620,30 +1637,12 @@ func TestHTLCsExtraData(t *testing.T) {
 			},
 		},
 		{
+			// Some HTLCs with extra data, some without.
 			name: "mixed extra data",
 			htlcs: []HTLC{
 				mockHtlc,
-				{
-					Signature:     testSig.Serialize(),
-					Incoming:      false,
-					Amt:           10,
-					RHash:         key,
-					RefundTimeout: 1,
-					OnionBlob:     lnmock.MockOnion(),
-					ExtraData:     []byte{1, 2, 3},
-				},
+				blindingPointHTLC,
 				mockHtlc,
-				{
-					Signature:     testSig.Serialize(),
-					Incoming:      false,
-					Amt:           10,
-					RHash:         key,
-					RefundTimeout: 1,
-					OnionBlob:     lnmock.MockOnion(),
-					ExtraData: bytes.Repeat(
-						[]byte{9}, 999,
-					),
-				},
 			},
 		},
 	}
@@ -1661,7 +1660,15 @@ func TestHTLCsExtraData(t *testing.T) {
 			r := bytes.NewReader(b.Bytes())
 			htlcs, err := DeserializeHtlcs(r)
 			require.NoError(t, err)
-			require.Equal(t, testCase.htlcs, htlcs)
+
+			require.EqualValues(t, len(testCase.htlcs), len(htlcs))
+			for i, htlc := range htlcs {
+				// We use the extra data field when we
+				// serialize, so we set to nil to be able to
+				// assert on equal for the test.
+				htlc.ExtraData = nil
+				require.Equal(t, testCase.htlcs[i], htlc)
+			}
 		})
 	}
 }

lnwallet/channel.go

@@ -31,6 +31,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/shachain"
+	"github.com/lightningnetwork/lnd/tlv"
 )
 
 var (
@@ -371,6 +372,12 @@ type PaymentDescriptor struct {
 	// isForwarded denotes if an incoming HTLC has been forwarded to any
 	// possible upstream peers in the route.
 	isForwarded bool
+
+	// BlindingPoint is an optional ephemeral key used in route blinding.
+	// This value is set for nodes that are relaying payments inside of a
+	// blinded route (ie, not the introduction node) from update_add_htlc's
+	// TLVs.
+	BlindingPoint *btcec.PublicKey
 }
 
 // PayDescsFromRemoteLogUpdates converts a slice of LogUpdates received from the
@@ -411,6 +418,7 @@ func PayDescsFromRemoteLogUpdates(chanID lnwire.ShortChannelID, height uint64,
 					Height: height,
 					Index:  uint16(i),
 				},
+				BlindingPoint: wireMsg.BlingingPointOrNil(),
 			}
 			pd.OnionBlob = make([]byte, len(wireMsg.OnionBlob))
 			copy(pd.OnionBlob[:], wireMsg.OnionBlob[:])
@@ -736,6 +744,14 @@ func (c *commitment) toDiskCommit(ourCommit bool) *channeldb.ChannelCommitment {
 			Incoming:      false,
 		}
 		copy(h.OnionBlob[:], htlc.OnionBlob)
+		if htlc.BlindingPoint != nil {
+			h.BlindingPoint = tlv.SomeRecordT(
+				//nolint:lll
+				tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](
+					htlc.BlindingPoint,
+				),
+			)
+		}
 
 		if ourCommit && htlc.sig != nil {
 			h.Signature = htlc.sig.Serialize()
@@ -760,7 +776,14 @@ func (c *commitment) toDiskCommit(ourCommit bool) *channeldb.ChannelCommitment {
 			Incoming:      true,
 		}
 		copy(h.OnionBlob[:], htlc.OnionBlob)
-
+		if htlc.BlindingPoint != nil {
+			h.BlindingPoint = tlv.SomeRecordT(
+				//nolint:lll
+				tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](
+					htlc.BlindingPoint,
+				),
+			)
+		}
 		if ourCommit && htlc.sig != nil {
 			h.Signature = htlc.sig.Serialize()
 		}
@@ -859,6 +882,12 @@ func (lc *LightningChannel) diskHtlcToPayDesc(feeRate chainfee.SatPerKWeight,
 		theirWitnessScript: theirWitnessScript,
 	}
 
+	htlc.BlindingPoint.WhenSome(func(b tlv.RecordT[
+		lnwire.BlindingPointTlvType, *btcec.PublicKey]) {
+
+		pd.BlindingPoint = b.Val
+	})
+
 	return pd, nil
 }
 
@@ -1548,6 +1577,7 @@ func (lc *LightningChannel) logUpdateToPayDesc(logUpdate *channeldb.LogUpdate,
 			HtlcIndex:             wireMsg.ID,
 			LogIndex:              logUpdate.LogIndex,
 			addCommitHeightRemote: commitHeight,
+			BlindingPoint:         wireMsg.BlingingPointOrNil(),
 		}
 		pd.OnionBlob = make([]byte, len(wireMsg.OnionBlob))
 		copy(pd.OnionBlob[:], wireMsg.OnionBlob[:])
@@ -1745,6 +1775,7 @@ func (lc *LightningChannel) remoteLogUpdateToPayDesc(logUpdate *channeldb.LogUpd
 			HtlcIndex:            wireMsg.ID,
 			LogIndex:             logUpdate.LogIndex,
 			addCommitHeightLocal: commitHeight,
+			BlindingPoint:        wireMsg.BlingingPointOrNil(),
 		}
 		pd.OnionBlob = make([]byte, len(wireMsg.OnionBlob))
 		copy(pd.OnionBlob, wireMsg.OnionBlob[:])
@@ -3607,6 +3638,14 @@ func (lc *LightningChannel) createCommitDiff(
 				PaymentHash: pd.RHash,
 			}
 			copy(htlc.OnionBlob[:], pd.OnionBlob)
+			if pd.BlindingPoint != nil {
+				htlc.BlindingPoint = tlv.SomeRecordT(
+					//nolint:lll
+					tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](
+						pd.BlindingPoint,
+					),
+				)
+			}
 			logUpdate.UpdateMsg = htlc
 
 			// Gather any references for circuits opened by this Add
@@ -3736,12 +3775,21 @@ func (lc *LightningChannel) getUnsignedAckedUpdates() []channeldb.LogUpdate {
 		// four messages that it corresponds to.
 		switch pd.EntryType {
 		case Add:
+			var b lnwire.BlindingPointRecord
+			if pd.BlindingPoint != nil {
+				tlv.SomeRecordT(
+					//nolint:lll
+					tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](pd.BlindingPoint),
+				)
+			}
+
 			htlc := &lnwire.UpdateAddHTLC{
-				ChanID:      chanID,
-				ID:          pd.HtlcIndex,
-				Amount:      pd.Amount,
-				Expiry:      pd.Timeout,
-				PaymentHash: pd.RHash,
+				ChanID:        chanID,
+				ID:            pd.HtlcIndex,
+				Amount:        pd.Amount,
+				Expiry:        pd.Timeout,
+				PaymentHash:   pd.RHash,
+				BlindingPoint: b,
 			}
 			copy(htlc.OnionBlob[:], pd.OnionBlob)
 			logUpdate.UpdateMsg = htlc
@@ -5742,6 +5790,14 @@ func (lc *LightningChannel) ReceiveRevocation(revMsg *lnwire.RevokeAndAck) (
 				Expiry:      pd.Timeout,
 				PaymentHash: pd.RHash,
 			}
+			if pd.BlindingPoint != nil {
+				htlc.BlindingPoint = tlv.SomeRecordT(
+					//nolint:lll
+					tlv.NewPrimitiveRecord[lnwire.BlindingPointTlvType](
+						pd.BlindingPoint,
+					),
+				)
+			}
 			copy(htlc.OnionBlob[:], pd.OnionBlob)
 			logUpdate.UpdateMsg = htlc
 			addUpdates = append(addUpdates, logUpdate)
@@ -6079,6 +6135,7 @@ func (lc *LightningChannel) htlcAddDescriptor(htlc *lnwire.UpdateAddHTLC,
 		HtlcIndex:      lc.localUpdateLog.htlcCounter,
 		OnionBlob:      htlc.OnionBlob[:],
 		OpenCircuitKey: openKey,
+		BlindingPoint:  htlc.BlingingPointOrNil(),
 	}
 }
 
@@ -6129,13 +6186,14 @@ func (lc *LightningChannel) ReceiveHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, err
 	}
 
 	pd := &PaymentDescriptor{
-		EntryType: Add,
-		RHash:     PaymentHash(htlc.PaymentHash),
-		Timeout:   htlc.Expiry,
-		Amount:    htlc.Amount,
-		LogIndex:  lc.remoteUpdateLog.logIndex,
-		HtlcIndex: lc.remoteUpdateLog.htlcCounter,
-		OnionBlob: htlc.OnionBlob[:],
+		EntryType:     Add,
+		RHash:         PaymentHash(htlc.PaymentHash),
+		Timeout:       htlc.Expiry,
+		Amount:        htlc.Amount,
+		LogIndex:      lc.remoteUpdateLog.logIndex,
+		HtlcIndex:     lc.remoteUpdateLog.htlcCounter,
+		OnionBlob:     htlc.OnionBlob[:],
+		BlindingPoint: htlc.BlingingPointOrNil(),
 	}
 
 	localACKedIndex := lc.remoteCommitChain.tail().ourMessageIndex