lnd+server+watchtower: allow Standalone access to the tor controller

This commit lets the watchtower automatically create hidden services
by giving it a pointer to a TorController. The server was also slightly
refactored so that it was not the sole owner of the TorController.

lnd.go

@@ -45,6 +45,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
 	"github.com/lightningnetwork/lnd/macaroons"
 	"github.com/lightningnetwork/lnd/signal"
+	"github.com/lightningnetwork/lnd/tor"
 	"github.com/lightningnetwork/lnd/walletunlocker"
 	"github.com/lightningnetwork/lnd/watchtower"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
@@ -473,6 +474,28 @@ func Main(lisCfg ListenerCfg) error {
 		defer towerClientDB.Close()
 	}
 
+	// If tor is active and either v2 or v3 onion services have been specified,
+	// make a tor controller and pass it into both the watchtower server and
+	// the regular lnd server.
+	var torController *tor.Controller
+	if cfg.Tor.Active && (cfg.Tor.V2 || cfg.Tor.V3) {
+		torController = tor.NewController(
+			cfg.Tor.Control, cfg.Tor.TargetIPAddress, cfg.Tor.Password,
+		)
+
+		// Start the tor controller before giving it to any other subsystems.
+		if err := torController.Start(); err != nil {
+			err := fmt.Errorf("unable to initialize tor controller: %v", err)
+			ltndLog.Error(err)
+			return err
+		}
+		defer func() {
+			if err := torController.Stop(); err != nil {
+				ltndLog.Errorf("error stopping tor controller: %v", err)
+			}
+		}()
+	}
+
 	var tower *watchtower.Standalone
 	if cfg.Watchtower.Active {
 		// Segment the watchtower directory by chain and network.
@@ -506,7 +529,7 @@ func Main(lisCfg ListenerCfg) error {
 			return err
 		}
 
-		wtConfig, err := cfg.Watchtower.Apply(&watchtower.Config{
+		wtCfg := &watchtower.Config{
 			BlockFetcher:   activeChainControl.chainIO,
 			DB:             towerDB,
 			EpochRegistrar: activeChainControl.chainNotifier,
@@ -519,7 +542,23 @@ func Main(lisCfg ListenerCfg) error {
 			NodePrivKey: towerPrivKey,
 			PublishTx:   activeChainControl.wallet.PublishTransaction,
 			ChainHash:   *activeNetParams.GenesisHash,
-		}, lncfg.NormalizeAddresses)
+		}
+
+		// If there is a tor controller (user wants auto hidden services), then
+		// store a pointer in the watchtower config.
+		if torController != nil {
+			wtCfg.TorController = torController
+			wtCfg.WatchtowerKeyPath = cfg.Tor.WatchtowerKeyPath
+
+			switch {
+			case cfg.Tor.V2:
+				wtCfg.Type = tor.V2
+			case cfg.Tor.V3:
+				wtCfg.Type = tor.V3
+			}
+		}
+
+		wtConfig, err := cfg.Watchtower.Apply(wtCfg, lncfg.NormalizeAddresses)
 		if err != nil {
 			err := fmt.Errorf("Unable to configure watchtower: %v",
 				err)
@@ -543,6 +582,7 @@ func Main(lisCfg ListenerCfg) error {
 	server, err := newServer(
 		cfg.Listeners, chanDB, towerClientDB, activeChainControl,
 		idPrivKey, walletInitParams.ChansToRestore, chainedAcceptor,
+		torController,
 	)
 	if err != nil {
 		err := fmt.Errorf("Unable to create server: %v", err)

server.go

@@ -322,7 +322,8 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 	towerClientDB *wtdb.ClientDB, cc *chainControl,
 	privKey *btcec.PrivateKey,
 	chansToRestore walletunlocker.ChannelsToRecover,
-	chanPredicate chanacceptor.ChannelAcceptor) (*server, error) {
+	chanPredicate chanacceptor.ChannelAcceptor,
+	torController *tor.Controller) (*server, error) {
 
 	var err error
 
@@ -428,6 +429,8 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		// schedule
 		sphinx: hop.NewOnionProcessor(sphinxRouter),
 
+		torController: torController,
+
 		persistentPeers:         make(map[string]bool),
 		persistentPeersBackoff:  make(map[string]time.Duration),
 		persistentConnReqs:      make(map[string][]*connmgr.ConnReq),
@@ -598,16 +601,6 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		selfAddrs = append(selfAddrs, ip)
 	}
 
-	// If we were requested to route connections through Tor and to
-	// automatically create an onion service, we'll initiate our Tor
-	// controller and establish a connection to the Tor server.
-	if cfg.Tor.Active && (cfg.Tor.V2 || cfg.Tor.V3) {
-		s.torController = tor.NewController(
-			cfg.Tor.Control, cfg.Tor.TargetIPAddress,
-			cfg.Tor.Password,
-		)
-	}
-
 	chanGraph := chanDB.ChannelGraph()
 
 	// We'll now reconstruct a node announcement based on our current
@@ -1251,7 +1244,7 @@ func (s *server) Start() error {
 	var startErr error
 	s.start.Do(func() {
 		if s.torController != nil {
-			if err := s.initTorController(); err != nil {
+			if err := s.createNewHiddenService(); err != nil {
 				startErr = err
 				return
 			}
@@ -1442,10 +1435,6 @@ func (s *server) Stop() error {
 
 		close(s.quit)
 
-		if s.torController != nil {
-			s.torController.Stop()
-		}
-
 		// Shutdown the wallet, funding manager, and the rpc server.
 		s.chanStatusMgr.Stop()
 		s.cc.chainNotifier.Stop()
@@ -1965,14 +1954,9 @@ func (s *server) initialPeerBootstrap(ignore map[autopilot.NodeID]struct{},
 	}
 }
 
-// initTorController initiliazes the Tor controller backed by lnd and
-// automatically sets up a v2 onion service in order to listen for inbound
-// connections over Tor.
-func (s *server) initTorController() error {
-	if err := s.torController.Start(); err != nil {
-		return err
-	}
-
+// createNewHiddenService automatically sets up a v2 or v3 onion service in
+// order to listen for inbound connections over Tor.
+func (s *server) createNewHiddenService() error {
 	// Determine the different ports the server is listening on. The onion
 	// service's virtual port will map to these ports and one will be picked
 	// at random when the onion service is being accessed.

watchtower/config.go

@@ -34,8 +34,8 @@ var (
 )
 
 // Config defines the resources and parameters used to configure a Watchtower.
-// All nil-able elements with the Config must be set in order for the Watchtower
-// to function properly.
+// All nil-able elements besides tor-related ones must be set in order for the
+// Watchtower to function properly.
 type Config struct {
 	// ChainHash identifies the chain that the watchtower will be monitoring
 	// for breaches and that will be advertised in the server's Init message
@@ -89,4 +89,16 @@ type Config struct {
 	// message from the other end, if the connection has stopped buffering
 	// the server's replies.
 	WriteTimeout time.Duration
+
+	// TorController allows the watchtower to optionally setup an onion hidden
+	// service.
+	TorController *tor.Controller
+
+	// WatchtowerKeyPath allows the watchtower to specify where the private key
+	// for a watchtower hidden service should be stored.
+	WatchtowerKeyPath string
+
+	// Type specifies the hidden service type (V2 or V3) that the watchtower
+	// will create.
+	Type tor.OnionType
 }

watchtower/standalone.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/lightningnetwork/lnd/brontide"
+	"github.com/lightningnetwork/lnd/tor"
 	"github.com/lightningnetwork/lnd/watchtower/lookout"
 	"github.com/lightningnetwork/lnd/watchtower/wtserver"
 )
@@ -112,6 +113,15 @@ func (w *Standalone) Start() error {
 
 	log.Infof("Starting watchtower")
 
+	// If a tor controller exists in the config, then automatically create a
+	// hidden service for the watchtower to accept inbound connections from.
+	if w.cfg.TorController != nil {
+		log.Infof("Creating watchtower hidden service")
+		if err := w.createNewHiddenService(); err != nil {
+			return err
+		}
+	}
+
 	if err := w.lookout.Start(); err != nil {
 		return err
 	}
@@ -142,6 +152,39 @@ func (w *Standalone) Stop() error {
 	return nil
 }
 
+// createNewHiddenService automatically sets up a v2 or v3 onion service in
+// order to listen for inbound connections over Tor.
+func (w *Standalone) createNewHiddenService() error {
+	// Get all the ports the watchtower is listening on. These will be used to
+	// map the hidden service's virtual port.
+	listenPorts := make([]int, 0, len(w.listeners))
+	for _, listener := range w.listeners {
+		port := listener.Addr().(*net.TCPAddr).Port
+		listenPorts = append(listenPorts, port)
+	}
+
+	// Once we've created the port mapping, we can automatically create the
+	// hidden service. The service's private key will be saved on disk in order
+	// to persistently have access to this hidden service across restarts.
+	onionCfg := tor.AddOnionConfig{
+		VirtualPort: DefaultPeerPort,
+		TargetPorts: listenPorts,
+		Store:       tor.NewOnionFile(w.cfg.WatchtowerKeyPath, 0600),
+		Type:        w.cfg.Type,
+	}
+
+	addr, err := w.cfg.TorController.AddOnion(onionCfg)
+	if err != nil {
+		return err
+	}
+
+	// Append this address to ExternalIPs so that it will be exposed in
+	// tower info calls.
+	w.cfg.ExternalIPs = append(w.cfg.ExternalIPs, addr)
+
+	return nil
+}
+
 // PubKey returns the public key for the watchtower used to authentication and
 // encrypt traffic with clients.
 //