server+routing: pass isAlias to router

This allows the router to determine what is and isn't an alias from
lnd's definition of an alias. Any ChannelAnnouncement that has an
alias ShortChannelID field is not verified on-chain. To prevent a
DoS vector from existing, the gossiper ensures that only the local
lnd node can send its ChannelAnnouncements to the router with an
alias ShortChannelID.

routing/payment_lifecycle_test.go

@@ -473,6 +473,9 @@ func testPaymentLifecycle(t *testing.T, test paymentLifecycleTestCase,
 				return next, nil
 			},
 			Clock: clock.NewTestClock(time.Unix(1, 0)),
+			IsAlias: func(scid lnwire.ShortChannelID) bool {
+				return false
+			},
 		})
 		if err != nil {
 			t.Fatalf("unable to create router %v", err)

routing/router.go

@@ -358,6 +358,10 @@ type Config struct {
 	// Otherwise, we'll only prune the channel when both edges have a very
 	// dated last update.
 	StrictZombiePruning bool
+
+	// IsAlias returns whether a passed ShortChannelID is an alias. This is
+	// only used for our local channels.
+	IsAlias func(scid lnwire.ShortChannelID) bool
 }
 
 // EdgeLocator is a struct used to identify a specific edge.
@@ -1455,8 +1459,12 @@ func (r *ChannelRouter) processUpdate(msg interface{},
 		// If AssumeChannelValid is present, then we are unable to
 		// perform any of the expensive checks below, so we'll
 		// short-circuit our path straight to adding the edge to our
-		// graph.
-		if r.cfg.AssumeChannelValid {
+		// graph. If the passed ShortChannelID is an alias, then we'll
+		// skip validation as it will not map to a legitimate tx. This
+		// is not a DoS vector as only we can add an alias
+		// ChannelAnnouncement from the gossiper.
+		scid := lnwire.NewShortChanIDFromInt(msg.ChannelID)
+		if r.cfg.AssumeChannelValid || r.cfg.IsAlias(scid) {
 			if err := r.cfg.Graph.AddChannelEdge(msg, op...); err != nil {
 				return fmt.Errorf("unable to add edge: %v", err)
 			}

routing/router_test.go

@@ -82,6 +82,9 @@ func (c *testCtx) RestartRouter(t *testing.T) {
 		Control:            makeMockControlTower(),
 		ChannelPruneExpiry: time.Hour * 24,
 		GraphPruneInterval: time.Hour * 2,
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	require.NoError(t, err, "unable to create router")
 	require.NoError(t, router.Start(), "unable to start router")
@@ -165,6 +168,9 @@ func createTestCtxFromGraphInstanceAssumeValid(t *testing.T,
 		Clock:               clock.NewTestClock(time.Unix(1, 0)),
 		AssumeChannelValid:  assumeValid,
 		StrictZombiePruning: strictPruning,
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	require.NoError(t, err, "unable to create router")
 	require.NoError(t, router.Start(), "unable to start router")
@@ -1738,6 +1744,10 @@ func TestWakeUpOnStaleBranch(t *testing.T) {
 
 		// We'll set the delay to zero to prune immediately.
 		FirstTimePruneDelay: 0,
+
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	if err != nil {
 		t.Fatalf("unable to create router %v", err)
@@ -3485,6 +3495,10 @@ func TestSendMPPaymentSucceed(t *testing.T) {
 			next := atomic.AddUint64(&uniquePaymentID, 1)
 			return next, nil
 		},
+
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	require.NoError(t, err, "failed to create router")
 
@@ -3648,6 +3662,10 @@ func TestSendMPPaymentSucceedOnExtraShards(t *testing.T) {
 			next := atomic.AddUint64(&uniquePaymentID, 1)
 			return next, nil
 		},
+
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	require.NoError(t, err, "failed to create router")
 
@@ -3856,6 +3874,10 @@ func TestSendMPPaymentFailed(t *testing.T) {
 			next := atomic.AddUint64(&uniquePaymentID, 1)
 			return next, nil
 		},
+
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	require.NoError(t, err, "failed to create router")
 
@@ -4056,6 +4078,10 @@ func TestSendMPPaymentFailedWithShardsInFlight(t *testing.T) {
 			next := atomic.AddUint64(&uniquePaymentID, 1)
 			return next, nil
 		},
+
+		IsAlias: func(scid lnwire.ShortChannelID) bool {
+			return false
+		},
 	})
 	require.NoError(t, err, "failed to create router")
 

server.go

@@ -920,6 +920,7 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 		PathFindingConfig:   pathFindingConfig,
 		Clock:               clock.NewDefaultClock(),
 		StrictZombiePruning: strictPruning,
+		IsAlias:             aliasmgr.IsAlias,
 	})
 	if err != nil {
 		return nil, fmt.Errorf("can't create router: %v", err)