multi: use key locator for lnwallet.MessageSigner

To simplify the message signing API even further, we refactor the
lnwallet.MessageSigner interface to use a key locator instead of the
public key to identify which key should be signed with.

netann/chan_status_manager.go

@@ -8,6 +8,7 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
@@ -43,6 +44,10 @@ type ChanStatusConfig struct {
 	// OurPubKey is the public key identifying this node on the network.
 	OurPubKey *btcec.PublicKey
 
+	// OurKeyLoc is the locator for the public key identifying this node on
+	// the network.
+	OurKeyLoc keychain.KeyLocator
+
 	// MessageSigner signs messages that validate under OurPubKey.
 	MessageSigner lnwallet.MessageSigner
 
@@ -621,7 +626,7 @@ func (m *ChanStatusManager) signAndSendNextUpdate(outpoint wire.OutPoint,
 	}
 
 	err = SignChannelUpdate(
-		m.cfg.MessageSigner, m.cfg.OurPubKey, chanUpdate,
+		m.cfg.MessageSigner, m.cfg.OurKeyLoc, chanUpdate,
 		ChanUpdSetDisable(disabled), ChanUpdSetTimestamp,
 	)
 	if err != nil {

netann/chan_status_manager_test.go

@@ -19,6 +19,10 @@ import (
 	"github.com/lightningnetwork/lnd/netann"
 )
 
+var (
+	testKeyLoc = keychain.KeyLocator{Family: keychain.KeyFamilyNodeKey}
+)
+
 // randOutpoint creates a random wire.Outpoint.
 func randOutpoint(t *testing.T) wire.OutPoint {
 	t.Helper()
@@ -310,7 +314,7 @@ func newManagerCfg(t *testing.T, numChannels int,
 	if err != nil {
 		t.Fatalf("unable to generate key pair: %v", err)
 	}
-	privKeySigner := &keychain.PrivKeyMessageSigner{PrivKey: privKey}
+	privKeySigner := keychain.NewPrivKeyMessageSigner(privKey, testKeyLoc)
 
 	graph := newMockGraph(
 		t, numChannels, startEnabled, startEnabled, privKey.PubKey(),
@@ -322,6 +326,7 @@ func newManagerCfg(t *testing.T, numChannels int,
 		ChanEnableTimeout:        500 * time.Millisecond,
 		ChanDisableTimeout:       time.Second,
 		OurPubKey:                privKey.PubKey(),
+		OurKeyLoc:                testKeyLoc,
 		MessageSigner:            netann.NewNodeSigner(privKeySigner),
 		IsChannelActive:          htlcSwitch.HasActiveLink,
 		ApplyChannelUpdate:       graph.ApplyChannelUpdate,

netann/channel_update.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
@@ -55,7 +56,7 @@ func ChanUpdSetTimestamp(update *lnwire.ChannelUpdate) {
 // monotonically increase from the prior.
 //
 // NOTE: This method modifies the given update.
-func SignChannelUpdate(signer lnwallet.MessageSigner, pubKey *btcec.PublicKey,
+func SignChannelUpdate(signer lnwallet.MessageSigner, keyLoc keychain.KeyLocator,
 	update *lnwire.ChannelUpdate, mods ...ChannelUpdateModifier) error {
 
 	// Apply the requested changes to the channel update.
@@ -64,7 +65,7 @@ func SignChannelUpdate(signer lnwallet.MessageSigner, pubKey *btcec.PublicKey,
 	}
 
 	// Create the DER-encoded ECDSA signature over the message digest.
-	sig, err := SignAnnouncement(signer, pubKey, update)
+	sig, err := SignAnnouncement(signer, keyLoc, update)
 	if err != nil {
 		return err
 	}

netann/channel_update_test.go

@@ -6,7 +6,6 @@ import (
 	"time"
 
 	"github.com/btcsuite/btcd/btcec"
-	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -18,8 +17,8 @@ type mockSigner struct {
 	err error
 }
 
-func (m *mockSigner) SignMessage(pk *btcec.PublicKey,
-	msg []byte) (input.Signature, error) {
+func (m *mockSigner) SignMessage(_ keychain.KeyLocator,
+	_ []byte) (*btcec.Signature, error) {
 
 	if m.err != nil {
 		return nil, m.err
@@ -32,7 +31,7 @@ var _ lnwallet.MessageSigner = (*mockSigner)(nil)
 
 var (
 	privKey, _    = btcec.NewPrivateKey(btcec.S256())
-	privKeySigner = &keychain.PrivKeyMessageSigner{PrivKey: privKey}
+	privKeySigner = keychain.NewPrivKeyMessageSigner(privKey, testKeyLoc)
 
 	pubKey = privKey.PubKey()
 
@@ -130,7 +129,7 @@ func TestUpdateDisableFlag(t *testing.T) {
 			// Attempt to update and sign the new update, specifying
 			// disabled or enabled as prescribed in the test case.
 			err := netann.SignChannelUpdate(
-				tc.signer, pubKey, newUpdate,
+				tc.signer, testKeyLoc, newUpdate,
 				netann.ChanUpdSetDisable(tc.disable),
 				netann.ChanUpdSetTimestamp,
 			)

netann/node_announcement.go

@@ -4,7 +4,7 @@ import (
 	"net"
 	"time"
 
-	"github.com/btcsuite/btcd/btcec"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
@@ -40,7 +40,7 @@ func NodeAnnSetTimestamp(nodeAnn *lnwire.NodeAnnouncement) {
 // update should be the most recent, valid update, otherwise the timestamp may
 // not monotonically increase from the prior.
 func SignNodeAnnouncement(signer lnwallet.MessageSigner,
-	pubKey *btcec.PublicKey, nodeAnn *lnwire.NodeAnnouncement,
+	keyLoc keychain.KeyLocator, nodeAnn *lnwire.NodeAnnouncement,
 	mods ...NodeAnnModifier) error {
 
 	// Apply the requested changes to the node announcement.
@@ -49,7 +49,7 @@ func SignNodeAnnouncement(signer lnwallet.MessageSigner,
 	}
 
 	// Create the DER-encoded ECDSA signature over the message digest.
-	sig, err := SignAnnouncement(signer, pubKey, nodeAnn)
+	sig, err := SignAnnouncement(signer, keyLoc, nodeAnn)
 	if err != nil {
 		return err
 	}

netann/node_signer.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 
 	"github.com/btcsuite/btcd/btcec"
-	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 )
@@ -24,15 +23,15 @@ func NewNodeSigner(keySigner keychain.SingleKeyMessageSigner) *NodeSigner {
 }
 
 // SignMessage signs a double-sha256 digest of the passed msg under the
-// resident node's private key. If the target public key is _not_ the node's
-// private key, then an error will be returned.
-func (n *NodeSigner) SignMessage(pubKey *btcec.PublicKey,
-	msg []byte) (input.Signature, error) {
+// resident node's private key described in the key locator. If the target key
+// locator is _not_ the node's private key, then an error will be returned.
+func (n *NodeSigner) SignMessage(keyLoc keychain.KeyLocator,
+	msg []byte) (*btcec.Signature, error) {
 
 	// If this isn't our identity public key, then we'll exit early with an
 	// error as we can't sign with this key.
-	if !pubKey.IsEqual(n.keySigner.PubKey()) {
-		return nil, fmt.Errorf("unknown public key")
+	if keyLoc != n.keySigner.KeyLocator() {
+		return nil, fmt.Errorf("unknown public key locator")
 	}
 
 	// Otherwise, we'll sign the double-sha256 of the target message.

netann/sign.go

@@ -3,15 +3,15 @@ package netann
 import (
 	"fmt"
 
-	"github.com/btcsuite/btcd/btcec"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
 // SignAnnouncement signs any type of gossip message that is announced on the
 // network.
-func SignAnnouncement(signer lnwallet.MessageSigner, pubKey *btcec.PublicKey,
+func SignAnnouncement(signer lnwallet.MessageSigner, keyLoc keychain.KeyLocator,
 	msg lnwire.Message) (input.Signature, error) {
 
 	var (
@@ -33,5 +33,5 @@ func SignAnnouncement(signer lnwallet.MessageSigner, pubKey *btcec.PublicKey,
 		return nil, fmt.Errorf("unable to get data to sign: %v", err)
 	}
 
-	return signer.SignMessage(pubKey, data)
+	return signer.SignMessage(keyLoc, data)
 }