watchtower: use ECDH interface for watchtower session

lnd.go

@@ -557,17 +557,14 @@ func Main(cfg *Config, lisCfg ListenerCfg, shutdownChan <-chan struct{}) error {
 		}
 		defer towerDB.Close()
 
-		towerPrivKey, err := activeChainControl.wallet.DerivePrivKey(
-			keychain.KeyDescriptor{
-				KeyLocator: keychain.KeyLocator{
+		towerKeyDesc, err := activeChainControl.keyRing.DeriveKey(
+			keychain.KeyLocator{
 				Family: keychain.KeyFamilyTowerID,
 				Index:  0,
 			},
-			},
 		)
 		if err != nil {
-			err := fmt.Errorf("unable to derive watchtower "+
-				"private key: %v", err)
+			err := fmt.Errorf("error deriving tower key: %v", err)
 			ltndLog.Error(err)
 			return err
 		}
@@ -582,7 +579,9 @@ func Main(cfg *Config, lisCfg ListenerCfg, shutdownChan <-chan struct{}) error {
 					lnwallet.WitnessPubKey, false,
 				)
 			},
-			NodeKeyECDH: towerPrivKey,
+			NodeKeyECDH: keychain.NewPubKeyECDH(
+				towerKeyDesc, activeChainControl.keyRing,
+			),
 			PublishTx: activeChainControl.wallet.PublishTransaction,
 			ChainHash: *activeNetParams.GenesisHash,
 		}

watchtower/config.go

@@ -5,10 +5,10 @@ import (
 	"net"
 	"time"
 
-	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/tor"
 	"github.com/lightningnetwork/lnd/watchtower/lookout"
 )
@@ -65,7 +65,7 @@ type Config struct {
 
 	// NodeKeyECDH is the ECDH capable wrapper of the key to be used in
 	// accepting new brontide connections.
-	NodeKeyECDH *btcec.PrivateKey
+	NodeKeyECDH keychain.SingleKeyECDH
 
 	// PublishTx provides the ability to send a signed transaction to the
 	// network.

watchtower/standalone.go

@@ -72,7 +72,7 @@ func New(cfg *Config) (*Standalone, error) {
 	listeners := make([]net.Listener, 0, len(cfg.ListenAddrs))
 	for _, listenAddr := range cfg.ListenAddrs {
 		listener, err := brontide.NewListener(
-			nil/*TODO fix in next commit*/, listenAddr.String(),
+			cfg.NodeKeyECDH, listenAddr.String(),
 		)
 		if err != nil {
 			return nil, err

watchtower/wtclient/client.go

@@ -11,6 +11,7 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
@@ -337,7 +338,7 @@ func New(config *Config) (*TowerClient, error) {
 // NOTE: This method should only be used when deserialization of a
 // ClientSession's Tower and SessionPrivKey fields is desired, otherwise, the
 // existing ListClientSessions method should be used.
-func getClientSessions(db DB, keyRing SecretKeyRing, forTower *wtdb.TowerID,
+func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
 	passesFilter func(*wtdb.ClientSession) bool) (
 	map[wtdb.SessionID]*wtdb.ClientSession, error) {
 
@@ -358,11 +359,14 @@ func getClientSessions(db DB, keyRing SecretKeyRing, forTower *wtdb.TowerID,
 		}
 		s.Tower = tower
 
-		sessionKey, err := DeriveSessionKey(keyRing, s.KeyIndex)
+		towerKeyDesc, err := keyRing.DeriveKey(keychain.KeyLocator{
+			Family: keychain.KeyFamilyTowerSession,
+			Index:  s.KeyIndex,
+		})
 		if err != nil {
 			return nil, err
 		}
-		s.SessionKeyECDH = sessionKey
+		s.SessionKeyECDH = keychain.NewPubKeyECDH(towerKeyDesc, keyRing)
 
 		// If an optional filter was provided, use it to filter out any
 		// undesired sessions.
@@ -897,10 +901,10 @@ func (c *TowerClient) taskRejected(task *backupTask, curStatus reserveStatus) {
 // dial connects the peer at addr using privKey as our secret key for the
 // connection. The connection will use the configured Net's resolver to resolve
 // the address for either Tor or clear net connections.
-func (c *TowerClient) dial(privKey *btcec.PrivateKey,
+func (c *TowerClient) dial(localKey keychain.SingleKeyECDH,
 	addr *lnwire.NetAddress) (wtserver.Peer, error) {
 
-	return c.cfg.AuthDial(privKey, addr, c.cfg.Dial)
+	return c.cfg.AuthDial(localKey, addr, c.cfg.Dial)
 }
 
 // readMessage receives and parses the next message from the given Peer. An

watchtower/wtclient/client_test.go

@@ -101,10 +101,10 @@ func (m *mockNet) ResolveTCPAddr(network string, address string) (*net.TCPAddr,
 	panic("not implemented")
 }
 
-func (m *mockNet) AuthDial(localPriv *btcec.PrivateKey, netAddr *lnwire.NetAddress,
+func (m *mockNet) AuthDial(local keychain.SingleKeyECDH, netAddr *lnwire.NetAddress,
 	dialer func(string, string) (net.Conn, error)) (wtserver.Peer, error) {
 
-	localPk := localPriv.PubKey()
+	localPk := local.PubKey()
 	localAddr := &net.TCPAddr{
 		IP:   net.IP{0x32, 0x31, 0x30, 0x29},
 		Port: 36723,
@@ -401,6 +401,7 @@ func newHarness(t *testing.T, cfg harnessCfg) *testHarness {
 	if err != nil {
 		t.Fatalf("Unable to generate tower private key: %v", err)
 	}
+	privKeyECDH := &keychain.PrivKeyECDH{PrivKey: privKey}
 
 	towerPubKey := privKey.PubKey()
 
@@ -416,7 +417,7 @@ func newHarness(t *testing.T, cfg harnessCfg) *testHarness {
 		DB:           serverDB,
 		ReadTimeout:  timeout,
 		WriteTimeout: timeout,
-		NodeKeyECDH:  privKey,
+		NodeKeyECDH:  privKeyECDH,
 		NewAddress: func() (btcutil.Address, error) {
 			return addr, nil
 		},

watchtower/wtclient/derivation.go

@@ -1,24 +0,0 @@
-package wtclient
-
-import (
-	"github.com/btcsuite/btcd/btcec"
-	"github.com/lightningnetwork/lnd/keychain"
-)
-
-// DeriveSessionKey accepts an session key index for an existing session and
-// derives the HD private key to be used to authenticate the brontide transport
-// and authenticate requests sent to the tower. The key will use the
-// keychain.KeyFamilyTowerSession and the provided index, giving a BIP43
-// derivation path of:
-//
-//  * m/1017'/coinType'/8/0/index
-func DeriveSessionKey(keyRing ECDHKeyRing,
-	index uint32) (*btcec.PrivateKey, error) {
-
-	return keyRing.DerivePrivKey(keychain.KeyDescriptor{
-		KeyLocator: keychain.KeyLocator{
-			Family: keychain.KeyFamilyTowerSession,
-			Index:  index,
-		},
-	})
-}

watchtower/wtclient/interface.go

@@ -102,14 +102,14 @@ type Dial func(net, addr string) (net.Conn, error)
 // AuthDialer connects to a remote node using an authenticated transport, such as
 // brontide. The dialer argument is used to specify a resolver, which allows
 // this method to be used over Tor or clear net connections.
-type AuthDialer func(localPriv *btcec.PrivateKey, netAddr *lnwire.NetAddress,
+type AuthDialer func(localKey keychain.SingleKeyECDH, netAddr *lnwire.NetAddress,
 	dialer func(string, string) (net.Conn, error)) (wtserver.Peer, error)
 
 // AuthDial is the watchtower client's default method of dialing.
-func AuthDial(localPriv *btcec.PrivateKey, netAddr *lnwire.NetAddress,
+func AuthDial(localKey keychain.SingleKeyECDH, netAddr *lnwire.NetAddress,
 	dialer func(string, string) (net.Conn, error)) (wtserver.Peer, error) {
 
-	return brontide.Dial(nil/*TODO fix in next commit*/, netAddr, dialer)
+	return brontide.Dial(localKey, netAddr, dialer)
 }
 
 // ECDHKeyRing abstracts the ability to derive shared ECDH keys given a
@@ -117,10 +117,6 @@ func AuthDial(localPriv *btcec.PrivateKey, netAddr *lnwire.NetAddress,
 type ECDHKeyRing interface {
 	keychain.ECDHRing
 
-	// DerivePrivKey derives the private key from the root seed using a
-	// key descriptor specifying the key's derivation path.
-	DerivePrivKey(loc keychain.KeyDescriptor) (*btcec.PrivateKey, error)
-
 	// DeriveKey attempts to derive an arbitrary key specified by the
 	// passed KeyLocator. This may be used in several recovery scenarios,
 	// or when manually rotating something like our current default node

watchtower/wtclient/session_negotiator.go

@@ -5,8 +5,8 @@ import (
 	"sync"
 	"time"
 
-	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/blob"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
@@ -58,7 +58,8 @@ type NegotiatorConfig struct {
 	// Dial initiates an outbound brontide connection to the given address
 	// using a specified private key. The peer is returned in the event of a
 	// successful connection.
-	Dial func(*btcec.PrivateKey, *lnwire.NetAddress) (wtserver.Peer, error)
+	Dial func(keychain.SingleKeyECDH, *lnwire.NetAddress) (wtserver.Peer,
+		error)
 
 	// SendMessage writes a wtwire message to remote peer.
 	SendMessage func(wtserver.Peer, wtwire.Message) error
@@ -315,13 +316,21 @@ func (n *sessionNegotiator) createSession(tower *wtdb.Tower,
 		return ErrNoTowerAddrs
 	}
 
-	sessionPriv, err := DeriveSessionKey(n.cfg.SecretKeyRing, keyIndex)
+	sessionKeyDesc, err := n.cfg.SecretKeyRing.DeriveKey(
+		keychain.KeyLocator{
+			Family: keychain.KeyFamilyTowerSession,
+			Index:  keyIndex,
+		},
+	)
 	if err != nil {
 		return err
 	}
+	sessionKey := keychain.NewPubKeyECDH(
+		sessionKeyDesc, n.cfg.SecretKeyRing,
+	)
 
 	for _, lnAddr := range tower.LNAddrs() {
-		err = n.tryAddress(sessionPriv, keyIndex, tower, lnAddr)
+		err := n.tryAddress(sessionKey, keyIndex, tower, lnAddr)
 		switch {
 		case err == ErrPermanentTowerFailure:
 			// TODO(conner): report to iterator? can then be reset
@@ -346,11 +355,11 @@ func (n *sessionNegotiator) createSession(tower *wtdb.Tower,
 // The address should belong to the tower's set of addresses. This method only
 // returns true if all steps succeed and the new session has been persisted, and
 // fails otherwise.
-func (n *sessionNegotiator) tryAddress(privKey *btcec.PrivateKey,
+func (n *sessionNegotiator) tryAddress(sessionKey keychain.SingleKeyECDH,
 	keyIndex uint32, tower *wtdb.Tower, lnAddr *lnwire.NetAddress) error {
 
 	// Connect to the tower address using our generated session key.
-	conn, err := n.cfg.Dial(privKey, lnAddr)
+	conn, err := n.cfg.Dial(sessionKey, lnAddr)
 	if err != nil {
 		return err
 	}
@@ -417,9 +426,7 @@ func (n *sessionNegotiator) tryAddress(privKey *btcec.PrivateKey,
 		// TODO(conner): validate reward address
 		rewardPkScript := createSessionReply.Data
 
-		sessionID := wtdb.NewSessionIDFromPubKey(
-			privKey.PubKey(),
-		)
+		sessionID := wtdb.NewSessionIDFromPubKey(sessionKey.PubKey())
 		clientSession := &wtdb.ClientSession{
 			ClientSessionBody: wtdb.ClientSessionBody{
 				TowerID:        tower.ID,
@@ -428,7 +435,7 @@ func (n *sessionNegotiator) tryAddress(privKey *btcec.PrivateKey,
 				RewardPkScript: rewardPkScript,
 			},
 			Tower:          tower,
-			SessionKeyECDH: privKey,
+			SessionKeyECDH: sessionKey,
 			ID:             sessionID,
 		}
 

watchtower/wtclient/session_queue.go

@@ -6,9 +6,9 @@ import (
 	"sync"
 	"time"
 
-	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
 	"github.com/lightningnetwork/lnd/watchtower/wtserver"
@@ -41,8 +41,8 @@ type sessionQueueConfig struct {
 
 	// Dial allows the client to dial the tower using it's public key and
 	// net address.
-	Dial func(*btcec.PrivateKey,
-		*lnwire.NetAddress) (wtserver.Peer, error)
+	Dial func(keychain.SingleKeyECDH, *lnwire.NetAddress) (wtserver.Peer,
+		error)
 
 	// SendMessage encodes, encrypts, and writes a message to the given peer.
 	SendMessage func(wtserver.Peer, wtwire.Message) error

watchtower/wtdb/client_session.go

@@ -4,7 +4,7 @@ import (
 	"fmt"
 	"io"
 
-	"github.com/btcsuite/btcd/btcec"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/blob"
 	"github.com/lightningnetwork/lnd/watchtower/wtpolicy"
@@ -65,7 +65,7 @@ type ClientSession struct {
 	//
 	// NOTE: This value is not serialized. It is derived using the KeyIndex
 	// on startup to avoid storing private keys on disk.
-	SessionKeyECDH *btcec.PrivateKey
+	SessionKeyECDH keychain.SingleKeyECDH
 }
 
 // ClientSessionBody represents the primary components of a ClientSession that

watchtower/wtmock/keyring.go

@@ -20,29 +20,6 @@ func NewSecretKeyRing() *SecretKeyRing {
 	}
 }
 
-// DerivePrivKey derives the private key for a given key descriptor. If
-// this method is called twice with the same argument, it will return the same
-// private key.
-func (m *SecretKeyRing) DerivePrivKey(
-	desc keychain.KeyDescriptor) (*btcec.PrivateKey, error) {
-
-	m.mu.Lock()
-	defer m.mu.Unlock()
-
-	if key, ok := m.keys[desc.KeyLocator]; ok {
-		return key, nil
-	}
-
-	privKey, err := btcec.NewPrivateKey(btcec.S256())
-	if err != nil {
-		return nil, err
-	}
-
-	m.keys[desc.KeyLocator] = privKey
-
-	return privKey, nil
-}
-
 // DeriveKey attempts to derive an arbitrary key specified by the
 // passed KeyLocator. This may be used in several recovery scenarios,
 // or when manually rotating something like our current default node

watchtower/wtserver/server.go

@@ -8,10 +8,10 @@ import (
 	"sync"
 	"time"
 
-	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/connmgr"
 	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
 	"github.com/lightningnetwork/lnd/watchtower/wtwire"
@@ -35,7 +35,7 @@ type Config struct {
 
 	// NodeKeyECDH is the the ECDH capable wrapper of the key to be used in
 	// accepting new brontide connections.
-	NodeKeyECDH *btcec.PrivateKey
+	NodeKeyECDH keychain.SingleKeyECDH
 
 	// Listeners specifies which address to which clients may connect.
 	Listeners []net.Listener