[3/3] aux revocation: breach-to-confirmation revocation flow

channeldb/channel.go

@@ -286,6 +286,13 @@ type openChannelTlvData struct {
 	// Note: if not set, it means either the channel has not been
 	// closed yet, or it was closed before this field was introduced.
 	closeConfirmationHeight tlv.OptionalRecordT[tlv.TlvType9, uint32]
+
+	// revocationAuxSigs is an optional blob carrying the revocation aux
+	// signatures attached to the most recently sent RevokeAndAck. It is
+	// only ever set for aux/custom (taproot asset) channels, so the same
+	// signatures can be re-attached if that RevokeAndAck has to be
+	// retransmitted on channel reestablish.
+	revocationAuxSigs tlv.OptionalRecordT[tlv.TlvType10, tlv.Blob]
 }
 
 // encode serializes the openChannelTlvData to the given io.Writer.
@@ -313,6 +320,11 @@ func (c *openChannelTlvData) encode(w io.Writer) error {
 			tlvRecords = append(tlvRecords, h.Record())
 		},
 	)
+	c.revocationAuxSigs.WhenSome(
+		func(sigs tlv.RecordT[tlv.TlvType10, tlv.Blob]) {
+			tlvRecords = append(tlvRecords, sigs.Record())
+		},
+	)
 
 	tlv.SortRecords(tlvRecords)
 
@@ -331,6 +343,7 @@ func (c *openChannelTlvData) decode(r io.Reader) error {
 	tapscriptRoot := c.tapscriptRoot.Zero()
 	blob := c.customBlob.Zero()
 	closeConfHeight := c.closeConfirmationHeight.Zero()
+	revocationAuxSigs := c.revocationAuxSigs.Zero()
 
 	// Create the tlv stream.
 	tlvStream, err := tlv.NewStream(
@@ -343,6 +356,7 @@ func (c *openChannelTlvData) decode(r io.Reader) error {
 		blob.Record(),
 		c.confirmationHeight.Record(),
 		closeConfHeight.Record(),
+		revocationAuxSigs.Record(),
 	)
 	if err != nil {
 		return err
@@ -365,6 +379,9 @@ func (c *openChannelTlvData) decode(r io.Reader) error {
 	if _, ok := tlvs[closeConfHeight.TlvType()]; ok {
 		c.closeConfirmationHeight = tlv.SomeRecordT(closeConfHeight)
 	}
+	if _, ok := tlvs[revocationAuxSigs.TlvType()]; ok {
+		c.revocationAuxSigs = tlv.SomeRecordT(revocationAuxSigs)
+	}
 
 	return nil
 }
@@ -630,6 +647,9 @@ func amendOpenChannelTlvData(channel *OpenChannel, auxData openChannelTlvData) {
 	auxData.closeConfirmationHeight.WhenSomeV(func(h uint32) {
 		channel.CloseConfirmationHeight = fn.Some(h)
 	})
+	auxData.revocationAuxSigs.WhenSomeV(func(sigs tlv.Blob) {
+		channel.RevocationAuxSigs = fn.Some(sigs)
+	})
 }
 
 // extractOpenChannelTlvData creates a new openChannelTlvData from the given
@@ -673,6 +693,11 @@ func extractOpenChannelTlvData(channel *OpenChannel) openChannelTlvData {
 			tlv.NewPrimitiveRecord[tlv.TlvType9](h),
 		)
 	})
+	channel.RevocationAuxSigs.WhenSome(func(sigs tlv.Blob) {
+		auxData.revocationAuxSigs = tlv.SomeRecordT(
+			tlv.NewPrimitiveRecord[tlv.TlvType10](sigs),
+		)
+	})
 
 	return auxData
 }

channeldb/channel_test.go

@@ -732,7 +732,9 @@ func TestChannelStateTransition(t *testing.T) {
 		},
 	}
 
-	_, err = channel.UpdateCommitment(&commitment, unsignedAckedUpdates)
+	_, err = channel.UpdateCommitment(
+		&commitment, unsignedAckedUpdates, fn.None[tlv.Blob](),
+	)
 	require.NoError(t, err, "unable to update commitment")
 
 	// Assert that update is correctly written to the database.

channeldb/db_test.go

@@ -14,13 +14,15 @@ import (
 	"github.com/btcsuite/btcd/btcutil/v2"
 	"github.com/btcsuite/btcd/chainhash/v2"
 	"github.com/btcsuite/btcd/wire/v2"
+	"github.com/lightningnetwork/lnd/fn/v2"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/lightningnetwork/lnd/shachain"
+	"github.com/lightningnetwork/lnd/tlv"
 	"github.com/stretchr/testify/require"
 )
 
@@ -382,7 +384,7 @@ func TestRestoreChannelShells(t *testing.T) {
 	// Ensure that it isn't possible to modify the commitment state machine
 	// of this restored channel.
 	channel := nodeChans[0]
-	_, err = channel.UpdateCommitment(nil, nil)
+	_, err = channel.UpdateCommitment(nil, nil, fn.None[tlv.Blob]())
 	if err != ErrNoRestoredChannelMutation {
 		t.Fatalf("able to mutate restored channel")
 	}

chanstate/open_channel.go

@@ -222,6 +222,15 @@ type OpenChannel struct {
 	// immutable.
 	CustomBlob fn.Option[tlv.Blob]
 
+	// RevocationAuxSigs is an optional blob carrying the revocation aux
+	// signatures attached to the most recently sent RevokeAndAck. It is
+	// only ever set for aux/custom (taproot asset) channels, and is
+	// persisted so the exact same signatures can be re-attached if that
+	// RevokeAndAck has to be retransmitted on channel reestablish. Only
+	// the latest revocation can ever be owed to the peer, so a single
+	// slot suffices; it is overwritten on every revocation.
+	RevocationAuxSigs fn.Option[tlv.Blob]
+
 	// Db persists channel state through the Store contract. This field
 	// intentionally keeps the existing name while callers still construct
 	// channels through the channeldb compatibility alias. The store
@@ -791,7 +800,8 @@ func (c *OpenChannel) SyncPending(addr net.Addr, pendingHeight uint32) error {
 // commitment. Keys correspond to htlc indices and values indicate whether the
 // htlc was settled or failed.
 func (c *OpenChannel) UpdateCommitment(newCommitment *ChannelCommitment,
-	unsignedAckedUpdates []LogUpdate) (map[uint64]bool, error) {
+	unsignedAckedUpdates []LogUpdate,
+	revocationAuxSigs fn.Option[tlv.Blob]) (map[uint64]bool, error) {
 
 	c.Lock()
 	defer c.Unlock()
@@ -803,6 +813,13 @@ func (c *OpenChannel) UpdateCommitment(newCommitment *ChannelCommitment,
 		return nil, ErrNoRestoredChannelMutation
 	}
 
+	// Record the aux sigs attached to the RevokeAndAck this commitment
+	// update corresponds to (custom channels only, None otherwise), so
+	// they persist alongside it and survive for retransmission. This
+	// overwrites the previous revocation's sigs, which can no longer be
+	// owed to the peer.
+	c.RevocationAuxSigs = revocationAuxSigs
+
 	finalHtlcs, err := c.Db.UpdateChannelCommitment(
 		c, newCommitment, unsignedAckedUpdates,
 	)