[4/5]: lnwallet: add new AuxSigner interface to mirror SigPool

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)
 

lnwallet/aux_signer.go

@@ -0,0 +1,149 @@
+package lnwallet
+
+import (
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/fn"
+	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+// BaseAuxJob is a struct that contains the common fields that are shared among
+// the aux sign/verify jobs.
+type BaseAuxJob struct {
+	// OutputIndex is the output index of the HTLC on the commitment
+	// transaction being signed.
+	//
+	// NOTE: If the output is dust from the PoV of the commitment chain,
+	// then this value will be -1.
+	OutputIndex int32
+
+	// KeyRing is the commitment key ring that contains the keys needed to
+	// generate the second level HTLC signatures.
+	KeyRing CommitmentKeyRing
+
+	// HTLC is the HTLC that is being signed or verified.
+	HTLC PaymentDescriptor
+
+	// Incoming is a boolean that indicates if the HTLC is incoming or
+	// outgoing.
+	Incoming bool
+
+	// CommitBlob is the commitment transaction blob that contains the aux
+	// information for this channel.
+	CommitBlob fn.Option[tlv.Blob]
+
+	// HtlcLeaf is the aux tap leaf that corresponds to the HTLC being
+	// signed/verified.
+	HtlcLeaf input.AuxTapLeaf
+}
+
+// AuxSigJob is a struct that contains all the information needed to sign an
+// HTLC for custom channels.
+type AuxSigJob struct {
+	// SignDesc is the sign desc for this HTLC.
+	SignDesc input.SignDescriptor
+
+	BaseAuxJob
+
+	// Resp is a channel that will be used to send the result of the sign
+	// job.
+	Resp chan AuxSigJobResp
+
+	// Cancel is a channel that should be closed if the caller wishes to
+	// abandon all pending sign jobs part of a single batch.
+	Cancel chan struct{}
+}
+
+// NewAuxSigJob creates a new AuxSigJob.
+func NewAuxSigJob(sigJob SignJob, keyRing CommitmentKeyRing, incoming bool,
+	htlc PaymentDescriptor, commitBlob fn.Option[tlv.Blob],
+	htlcLeaf input.AuxTapLeaf, cancelChan chan struct{}) AuxSigJob {
+
+	return AuxSigJob{
+		SignDesc: sigJob.SignDesc,
+		BaseAuxJob: BaseAuxJob{
+			OutputIndex: sigJob.OutputIndex,
+			KeyRing:     keyRing,
+			HTLC:        htlc,
+			Incoming:    incoming,
+			CommitBlob:  commitBlob,
+			HtlcLeaf:    htlcLeaf,
+		},
+		Resp:   make(chan AuxSigJobResp, 1),
+		Cancel: cancelChan,
+	}
+}
+
+// AuxSigJobResp is a struct that contains the result of a sign job.
+type AuxSigJobResp struct {
+	// SigBlob is the signature blob that was generated for the HTLC. This
+	// is an opaque TLV field that may contain the signature and other data.
+	SigBlob fn.Option[tlv.Blob]
+
+	// HtlcIndex is the index of the HTLC that was signed.
+	HtlcIndex uint64
+
+	// Err is the error that occurred when executing the specified
+	// signature job. In the case that no error occurred, this value will
+	// be nil.
+	Err error
+}
+
+// AuxVerifyJob is a struct that contains all the information needed to verify
+// an HTLC for custom channels.
+type AuxVerifyJob struct {
+	// SigBlob is the signature blob that was generated for the HTLC. This
+	// is an opaque TLV field that may contain the signature and other data.
+	SigBlob fn.Option[tlv.Blob]
+
+	BaseAuxJob
+
+	// Cancel is a channel that should be closed if the caller wishes to
+	// abandon the job.
+	Cancel chan struct{}
+
+	// ErrResp is a channel that will be used to send the result of the
+	// verify job.
+	ErrResp chan error
+}
+
+// NewAuxVerifyJob creates a new AuxVerifyJob.
+func NewAuxVerifyJob(sig fn.Option[tlv.Blob], keyRing CommitmentKeyRing,
+	incoming bool, htlc PaymentDescriptor, commitBlob fn.Option[tlv.Blob],
+	htlcLeaf input.AuxTapLeaf) AuxVerifyJob {
+
+	return AuxVerifyJob{
+		SigBlob: sig,
+		BaseAuxJob: BaseAuxJob{
+			KeyRing:    keyRing,
+			HTLC:       htlc,
+			Incoming:   incoming,
+			CommitBlob: commitBlob,
+			HtlcLeaf:   htlcLeaf,
+		},
+	}
+}
+
+// AuxSigner is an interface that is used to sign and verify HTLCs for custom
+// channels. It is similar to the existing SigPool, but uses opaque blobs to
+// shuffle around signature information and other metadata.
+type AuxSigner interface {
+	// SubmitSecondLevelSigBatch takes a batch of aux sign jobs and
+	// processes them asynchronously.
+	SubmitSecondLevelSigBatch(chanState *channeldb.OpenChannel,
+		commitTx *wire.MsgTx, sigJob []AuxSigJob) error
+
+	// PackSigs takes a series of aux signatures and packs them into a
+	// single blob that can be sent alongside the CommitSig messages.
+	PackSigs([]fn.Option[tlv.Blob]) (fn.Option[tlv.Blob], error)
+
+	// UnpackSigs takes a packed blob of signatures and returns the
+	// original signatures for each HTLC, keyed by HTLC index.
+	UnpackSigs(fn.Option[tlv.Blob]) ([]fn.Option[tlv.Blob], error)
+
+	// VerifySecondLevelSigs attempts to synchronously verify a batch of aux
+	// sig jobs.
+	VerifySecondLevelSigs(chanState *channeldb.OpenChannel,
+		commitTx *wire.MsgTx, verifyJob []AuxVerifyJob) error
+}