lnwire: add custom records field to type CommitSig

lnwire/commit_sig.go

@@ -45,6 +45,10 @@ type CommitSig struct {
 	// being signed for. In this case, the above Sig type MUST be blank.
 	PartialSig OptPartialSigWithNonceTLV
 
+	// CustomRecords maps TLV types to byte slices, storing arbitrary data
+	// intended for inclusion in the ExtraData field.
+	CustomRecords CustomRecords
+
 	// ExtraData is the set of data that was appended to this message to
 	// fill out the full maximum transport message size. These fields can
 	// be used to specify optional data such as custom TLV fields.
@@ -53,9 +57,7 @@ type CommitSig struct {
 
 // NewCommitSig creates a new empty CommitSig message.
 func NewCommitSig() *CommitSig {
-	return &CommitSig{
-		ExtraData: make([]byte, 0),
-	}
+	return &CommitSig{}
 }
 
 // A compile time check to ensure CommitSig implements the lnwire.Message
@@ -67,34 +69,37 @@ var _ Message = (*CommitSig)(nil)
 //
 // This is part of the lnwire.Message interface.
 func (c *CommitSig) Decode(r io.Reader, pver uint32) error {
+	// msgExtraData is a temporary variable used to read the message extra
+	// data field from the reader.
+	var msgExtraData ExtraOpaqueData
+
 	err := ReadElements(r,
 		&c.ChanID,
 		&c.CommitSig,
 		&c.HtlcSigs,
+		&msgExtraData,
 	)
 	if err != nil {
 		return err
 	}
 
-	var tlvRecords ExtraOpaqueData
-	if err := ReadElements(r, &tlvRecords); err != nil {
-		return err
-	}
-
+	// Extract TLV records from the extra data field.
 	partialSig := c.PartialSig.Zero()
-	typeMap, err := tlvRecords.ExtractRecords(&partialSig)
+
+	customRecords, parsed, extraData, err := ParseAndExtractCustomRecords(
+		msgExtraData, &partialSig,
+	)
 	if err != nil {
 		return err
 	}
 
 	// Set the corresponding TLV types if they were included in the stream.
-	if val, ok := typeMap[c.PartialSig.TlvType()]; ok && val == nil {
+	if _, ok := parsed[partialSig.TlvType()]; ok {
 		c.PartialSig = tlv.SomeRecordT(partialSig)
 	}
 
-	if len(tlvRecords) != 0 {
-		c.ExtraData = tlvRecords
-	}
+	c.CustomRecords = customRecords
+	c.ExtraData = extraData
 
 	return nil
 }
@@ -108,7 +113,10 @@ func (c *CommitSig) Encode(w *bytes.Buffer, pver uint32) error {
 	c.PartialSig.WhenSome(func(sig PartialSigWithNonceTLV) {
 		recordProducers = append(recordProducers, &sig)
 	})
-	err := EncodeMessageExtraData(&c.ExtraData, recordProducers...)
+
+	extraData, err := MergeAndEncode(
+		recordProducers, c.ExtraData, c.CustomRecords,
+	)
 	if err != nil {
 		return err
 	}
@@ -125,7 +133,7 @@ func (c *CommitSig) Encode(w *bytes.Buffer, pver uint32) error {
 		return err
 	}
 
-	return WriteBytes(w, c.ExtraData)
+	return WriteBytes(w, extraData)
 }
 
 // MsgType returns the integer uniquely identifying this message type on the

lnwire/commit_sig_test.go

@@ -0,0 +1,168 @@
+package lnwire
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+
+	"github.com/btcsuite/btcd/btcec/v2"
+	"github.com/btcsuite/btcd/btcec/v2/schnorr/musig2"
+	"github.com/lightningnetwork/lnd/tlv"
+	"github.com/stretchr/testify/require"
+)
+
+// testCase is a test case for the CommitSig message.
+type commitSigTestCase struct {
+	// Msg is the message to be encoded and decoded.
+	Msg CommitSig
+
+	// ExpectEncodeError is a flag that indicates whether we expect the
+	// encoding of the message to fail.
+	ExpectEncodeError bool
+}
+
+// generateCommitSigTestCases generates a set of CommitSig message test cases.
+func generateCommitSigTestCases(t *testing.T) []commitSigTestCase {
+	// Firstly, we'll set basic values for the message fields.
+	//
+	// Generate random channel ID.
+	chanIDBytes, err := generateRandomBytes(32)
+	require.NoError(t, err)
+
+	var chanID ChannelID
+	copy(chanID[:], chanIDBytes)
+
+	// Generate random commit sig.
+	commitSigBytes, err := generateRandomBytes(64)
+	require.NoError(t, err)
+
+	sig, err := NewSigFromSchnorrRawSignature(commitSigBytes)
+	require.NoError(t, err)
+
+	sigScalar := new(btcec.ModNScalar)
+	sigScalar.SetByteSlice(sig.RawBytes())
+
+	var nonce [musig2.PubNonceSize]byte
+	copy(nonce[:], commitSigBytes)
+
+	sigWithNonce := NewPartialSigWithNonce(nonce, *sigScalar)
+	partialSig := MaybePartialSigWithNonce(sigWithNonce)
+
+	// Define custom records.
+	recordKey1 := uint64(MinCustomRecordsTlvType + 1)
+	recordValue1, err := generateRandomBytes(10)
+	require.NoError(t, err)
+
+	recordKey2 := uint64(MinCustomRecordsTlvType + 2)
+	recordValue2, err := generateRandomBytes(10)
+	require.NoError(t, err)
+
+	customRecords := CustomRecords{
+		recordKey1: recordValue1,
+		recordKey2: recordValue2,
+	}
+
+	// Construct an instance of extra data that contains records with TLV
+	// types below the minimum custom records threshold and that lack
+	// corresponding fields in the message struct. Content should persist in
+	// the extra data field after encoding and decoding.
+	var (
+		recordBytes45 = []byte("recordBytes45")
+		tlvRecord45   = tlv.NewPrimitiveRecord[tlv.TlvType45](
+			recordBytes45,
+		)
+
+		recordBytes55 = []byte("recordBytes55")
+		tlvRecord55   = tlv.NewPrimitiveRecord[tlv.TlvType55](
+			recordBytes55,
+		)
+	)
+
+	var extraData ExtraOpaqueData
+	err = extraData.PackRecords(
+		[]tlv.RecordProducer{&tlvRecord45, &tlvRecord55}...,
+	)
+	require.NoError(t, err)
+
+	invalidCustomRecords := CustomRecords{
+		MinCustomRecordsTlvType - 1: recordValue1,
+	}
+
+	return []commitSigTestCase{
+		{
+			Msg: CommitSig{
+				ChanID:        chanID,
+				CommitSig:     sig,
+				PartialSig:    partialSig,
+				CustomRecords: customRecords,
+				ExtraData:     extraData,
+			},
+		},
+		// Add a test case where the blinding point field is not
+		// populated.
+		{
+			Msg: CommitSig{
+				ChanID:        chanID,
+				CommitSig:     sig,
+				CustomRecords: customRecords,
+			},
+		},
+		// Add a test case where the custom records field is not
+		// populated.
+		{
+			Msg: CommitSig{
+				ChanID:     chanID,
+				CommitSig:  sig,
+				PartialSig: partialSig,
+			},
+		},
+		// Add a case where the custom records are invalid.
+		{
+			Msg: CommitSig{
+				ChanID:        chanID,
+				CommitSig:     sig,
+				PartialSig:    partialSig,
+				CustomRecords: invalidCustomRecords,
+			},
+			ExpectEncodeError: true,
+		},
+	}
+}
+
+// TestCommitSigEncodeDecode tests CommitSig message encoding and decoding for
+// all supported field values.
+func TestCommitSigEncodeDecode(t *testing.T) {
+	t.Parallel()
+
+	// Generate test cases.
+	testCases := generateCommitSigTestCases(t)
+
+	// Execute test cases.
+	for tcIdx, tc := range testCases {
+		t.Run(fmt.Sprintf("testcase-%d", tcIdx), func(t *testing.T) {
+			// Encode test case message.
+			var buf bytes.Buffer
+			err := tc.Msg.Encode(&buf, 0)
+
+			// Check if we expect an encoding error.
+			if tc.ExpectEncodeError {
+				require.Error(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+
+			// Decode the encoded message bytes message.
+			var actualMsg CommitSig
+			decodeReader := bytes.NewReader(buf.Bytes())
+			err = actualMsg.Decode(decodeReader, 0)
+			require.NoError(t, err)
+
+			// The signature type isn't serialized.
+			actualMsg.CommitSig.ForceSchnorr()
+
+			// Compare the two messages to ensure equality.
+			require.Equal(t, tc.Msg, actualMsg)
+		})
+	}
+}

lnwire/lnwire_test.go

@@ -945,6 +945,8 @@ func TestLightningWireProtocol(t *testing.T) {
 				}
 			}
 
+			req.CustomRecords = randCustomRecords(t, r)
+
 			// 50/50 chance to attach a partial sig.
 			if r.Int31()%2 == 0 {
 				req.PartialSig = somePartialSigWithNonce(t, r)