Merge pull request #1655 from Roasbeef/send-to-route-defense

routing: ensure generateSphinxPacket can handle being passed empty set of routes

routing/router.go

@@ -38,6 +38,13 @@ const (
 	defaultPayAttemptTimeout = time.Duration(time.Second * 60)
 )
 
+var (
+	// ErrNoRouteHopsProvided is returned when a caller attempts to
+	// construct a new sphinx packet, but provides an empty set of hops for
+	// each route.
+	ErrNoRouteHopsProvided = fmt.Errorf("empty route hops provided")
+)
+
 // ChannelGraphSource represents the source of information about the topology
 // of the lightning network. It's responsible for the addition of nodes, edges,
 // applying edge updates, and returning the current block height with which the
@@ -1412,6 +1419,14 @@ func (r *ChannelRouter) FindRoutes(target *btcec.PublicKey,
 // be sent to the first hop within the route.
 func generateSphinxPacket(route *Route, paymentHash []byte) ([]byte,
 	*sphinx.Circuit, error) {
+
+	// As a sanity check, we'll ensure that the set of hops has been
+	// properly filled in, otherwise, we won't actually be able to
+	// construct a route.
+	if len(route.Hops) == 0 {
+		return nil, nil, ErrNoRouteHopsProvided
+	}
+
 	// First obtain all the public keys along the route which are contained
 	// in each hop.
 	nodes := make([]*btcec.PublicKey, len(route.Hops))

routing/router_test.go

@@ -9,14 +9,14 @@ import (
 	"testing"
 	"time"
 
+	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/htlcswitch"
-	"github.com/btcsuite/btcd/wire"
 
+	"github.com/btcsuite/btcd/btcec"
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/lnwire"
-	"github.com/btcsuite/btcd/btcec"
 )
 
 // defaultNumRoutes is the default value for the maximum number of routes to
@@ -1941,3 +1941,16 @@ func TestIsStaleEdgePolicy(t *testing.T) {
 		t.Fatalf("router failed to detect fresh edge policy")
 	}
 }
+
+// TestEmptyRoutesGenerateSphinxPacket tests that the generateSphinxPacket
+// function is able to gracefully handle being passed a nil set of hops for the
+// route by the caller.
+func TestEmptyRoutesGenerateSphinxPacket(t *testing.T) {
+	t.Parallel()
+
+	emptyRoute := &Route{}
+	_, _, err := generateSphinxPacket(emptyRoute, testHash[:])
+	if err != ErrNoRouteHopsProvided {
+		t.Fatalf("expected empty hops error: instead got: %v", err)
+	}
+}