lnwallet: obtain+verify aux sigs for all second level HTLCs

In this commit, we start to use the new AuxSigner to obtain+verify aux sigs for all second level HTLCs. This is similar to the existing SigPool, but we'll only attempt to do this if the AuxSigner is present (won't be for most channels).

chainreg/chainregistry.go

@@ -68,6 +68,10 @@ type Config struct {
 	// leaves for certain custom channel types.
 	AuxLeafStore fn.Option[lnwallet.AuxLeafStore]
 
+	// AuxSigner is an optional signer that can be used to sign auxiliary
+	// leaves for certain custom channel types.
+	AuxSigner fn.Option[lnwallet.AuxSigner]
+
 	// BlockCache is the main cache for storing block information.
 	BlockCache *blockcache.BlockCache
 

config_builder.go

@@ -170,10 +170,14 @@ type AuxComponents struct {
 	MsgRouter fn.Option[protofsm.MsgRouter]
 
 	// AuxFundingController is an optional controller that can be used to
-	// modify the way we handle certain custom chanenl types. It's also
+	// modify the way we handle certain custom channel types. It's also
 	// able to automatically handle new custom protocol messages related to
 	// the funding process.
 	AuxFundingController fn.Option[funding.AuxFundingController]
+
+	// AuxSigner is an optional signer that can be used to sign auxiliary
+	// leaves for certain custom channel types.
+	AuxSigner fn.Option[lnwallet.AuxSigner]
 }
 
 // DefaultWalletImpl is the default implementation of our normal, btcwallet
@@ -580,6 +584,7 @@ func (d *DefaultWalletImpl) BuildWalletConfig(ctx context.Context,
 		ChanStateDB:                 dbs.ChanStateDB.ChannelStateDB(),
 		NeutrinoCS:                  neutrinoCS,
 		AuxLeafStore:                aux.AuxLeafStore,
+		AuxSigner:                   aux.AuxSigner,
 		ActiveNetParams:             d.cfg.ActiveNetParams,
 		FeeURL:                      d.cfg.FeeURL,
 		Dialer: func(addr string) (net.Conn, error) {
@@ -732,6 +737,7 @@ func (d *DefaultWalletImpl) BuildChainControl(
 		NetParams:             *walletConfig.NetParams,
 		CoinSelectionStrategy: walletConfig.CoinSelectionStrategy,
 		AuxLeafStore:          partialChainControl.Cfg.AuxLeafStore,
+		AuxSigner:             partialChainControl.Cfg.AuxSigner,
 	}
 
 	// The broadcast is already always active for neutrino nodes, so we
@@ -911,10 +917,6 @@ type DatabaseInstances struct {
 	// for native SQL queries for tables that already support it. This may
 	// be nil if the use-native-sql flag was not set.
 	NativeSQLStore *sqldb.BaseDB
-
-	// AuxLeafStore is an optional data source that can be used by custom
-	// channels to fetch+store various data.
-	AuxLeafStore fn.Option[lnwallet.AuxLeafStore]
 }
 
 // DefaultDatabaseBuilder is a type that builds the default database backends

contractcourt/chain_arbitrator.go

@@ -221,6 +221,10 @@ type ChainArbitratorConfig struct {
 	// AuxLeafStore is an optional store that can be used to store auxiliary
 	// leaves for certain custom channel types.
 	AuxLeafStore fn.Option[lnwallet.AuxLeafStore]
+
+	// AuxSigner is an optional signer that can be used to sign auxiliary
+	// leaves for certain custom channel types.
+	AuxSigner fn.Option[lnwallet.AuxSigner]
 }
 
 // ChainArbitrator is a sub-system that oversees the on-chain resolution of all
@@ -307,6 +311,9 @@ func (a *arbChannel) NewAnchorResolutions() (*lnwallet.AnchorResolutions,
 	a.c.cfg.AuxLeafStore.WhenSome(func(s lnwallet.AuxLeafStore) {
 		chanOpts = append(chanOpts, lnwallet.WithLeafStore(s))
 	})
+	a.c.cfg.AuxSigner.WhenSome(func(s lnwallet.AuxSigner) {
+		chanOpts = append(chanOpts, lnwallet.WithAuxSigner(s))
+	})
 
 	chanMachine, err := lnwallet.NewLightningChannel(
 		a.c.cfg.Signer, channel, nil, chanOpts...,
@@ -357,6 +364,9 @@ func (a *arbChannel) ForceCloseChan() (*lnwallet.LocalForceCloseSummary, error)
 	a.c.cfg.AuxLeafStore.WhenSome(func(s lnwallet.AuxLeafStore) {
 		chanOpts = append(chanOpts, lnwallet.WithLeafStore(s))
 	})
+	a.c.cfg.AuxSigner.WhenSome(func(s lnwallet.AuxSigner) {
+		chanOpts = append(chanOpts, lnwallet.WithAuxSigner(s))
+	})
 
 	// Finally, we'll force close the channel completing
 	// the force close workflow.

funding/manager.go

@@ -548,6 +548,10 @@ type Config struct {
 	// able to automatically handle new custom protocol messages related to
 	// the funding process.
 	AuxFundingController fn.Option[AuxFundingController]
+
+	// AuxSigner is an optional signer that can be used to sign auxiliary
+	// leaves for certain custom channel types.
+	AuxSigner fn.Option[lnwallet.AuxSigner]
 }
 
 // Manager acts as an orchestrator/bridge between the wallet's
@@ -1077,6 +1081,9 @@ func (f *Manager) advanceFundingState(channel *channeldb.OpenChannel,
 	f.cfg.AuxLeafStore.WhenSome(func(s lnwallet.AuxLeafStore) {
 		chanOpts = append(chanOpts, lnwallet.WithLeafStore(s))
 	})
+	f.cfg.AuxSigner.WhenSome(func(s lnwallet.AuxSigner) {
+		chanOpts = append(chanOpts, lnwallet.WithAuxSigner(s))
+	})
 
 	// We create the state-machine object which wraps the database state.
 	lnChannel, err := lnwallet.NewLightningChannel(

htlcswitch/link.go

@@ -2143,6 +2143,7 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 			CommitSig:  msg.CommitSig,
 			HtlcSigs:   msg.HtlcSigs,
 			PartialSig: msg.PartialSig,
+			AuxSigBlob: msg.ExtraData,
 		})
 		if err != nil {
 			// If we were unable to reconstruct their proposed
@@ -2556,6 +2557,7 @@ func (l *channelLink) updateCommitTx() error {
 		CommitSig:  newCommit.CommitSig,
 		HtlcSigs:   newCommit.HtlcSigs,
 		PartialSig: newCommit.PartialSig,
+		ExtraData:  newCommit.AuxSigBlob,
 	}
 	l.cfg.Peer.SendMessage(false, commitSig)