Add test for improperly signed message

Test the case where an adversarial peer signs a message with a key they
didn't originally register with. First, we test that an adversarial peer
will allow the message to pass through validation as they turn off
strict verification (putting themselves at risk), but an honest peer
with strict verification on will never see the message!

floodsub_test.go

@@ -12,10 +12,11 @@ import (
 
 	host "github.com/libp2p/go-libp2p-host"
 	peer "github.com/libp2p/go-libp2p-peer"
+	protocol "github.com/libp2p/go-libp2p-protocol"
 	swarmt "github.com/libp2p/go-libp2p-swarm/testing"
+
 	//bhost "github.com/libp2p/go-libp2p/p2p/host/basic"
 	bhost "github.com/libp2p/go-libp2p-blankhost"
-	"github.com/libp2p/go-libp2p-protocol"
 )
 
 func checkMessageRouting(t *testing.T, topic string, pubs []*PubSub, subs []*Subscription) {
@@ -90,14 +91,18 @@ func connectAll(t *testing.T, hosts []host.Host) {
 	}
 }
 
+func getPubsub(ctx context.Context, h host.Host, opts ...Option) *PubSub {
+	ps, err := NewFloodSub(ctx, h, opts...)
+	if err != nil {
+		panic(err)
+	}
+	return ps
+}
+
 func getPubsubs(ctx context.Context, hs []host.Host, opts ...Option) []*PubSub {
 	var psubs []*PubSub
 	for _, h := range hs {
-		ps, err := NewFloodSub(ctx, h, opts...)
-		if err != nil {
-			panic(err)
-		}
-		psubs = append(psubs, ps)
+		psubs = append(psubs, getPubsub(ctx, h, opts...))
 	}
 	return psubs
 }
@@ -943,3 +948,113 @@ func TestWithSigning(t *testing.T) {
 		t.Fatalf("unexpected data: %s", string(msg.Data))
 	}
 }
+
+func TestImproperlySignedMessageNotRelayed(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	hosts := getNetHosts(t, ctx, 2)
+	adversarialPeer := hosts[0]
+	honestPeer := hosts[1]
+
+	// The adversary enables signing, but disables verification to let through
+	// an incorrectly signed message.
+	adversaryPubSub := getPubsub(
+		ctx,
+		adversarialPeer,
+		WithMessageSigning(true),
+		WithStrictSignatureVerification(false),
+	)
+	honestPubSub := getPubsub(
+		ctx,
+		honestPeer,
+		WithStrictSignatureVerification(true),
+	)
+
+	connect(t, hosts[0], hosts[1])
+
+	var (
+		topic            = "foobar"
+		correctMessage   = []byte("this is a correct message")
+		incorrectMessage = []byte("this is the incorrect message")
+	)
+
+	_, err := adversaryPubSub.Subscribe(topic)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	adversarialPeerSubscription, err := adversaryPubSub.Subscribe(topic)
+	if err != nil {
+		t.Fatal(err)
+	}
+	honestPeerSubscription, err := honestPubSub.Subscribe(topic)
+	if err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(time.Millisecond * 10)
+
+	// First the adversary sends the correct message.
+	err = adversaryPubSub.Publish(topic, correctMessage)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Change the sign key for the adversarial peer, and send the second message.
+	adversaryPubSub.signID = honestPubSub.signID
+	adversaryPubSub.signKey = honestPubSub.host.Peerstore().PrivKey(honestPubSub.signID)
+	err = adversaryPubSub.Publish(topic, incorrectMessage)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var adversaryMessages []*Message
+	adversaryContext, adversaryCancel := context.WithCancel(ctx)
+	go func(ctx context.Context) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				msg, err := adversarialPeerSubscription.Next(ctx)
+				if err != nil {
+					return
+				}
+				adversaryMessages = append(adversaryMessages, msg)
+			}
+		}
+	}(adversaryContext)
+
+	<-time.After(2 * time.Second)
+	adversaryCancel()
+
+	if len(adversaryMessages) != 2 {
+		t.Fatalf("got %d messages, expected 2", len(adversaryMessages))
+	}
+
+	// the honest peer's validation process will drop the message;
+	// next will never furnish the incorrect message.
+	var honestPeerMessages []*Message
+	honestPeerContext, honestPeerCancel := context.WithCancel(ctx)
+	go func(ctx context.Context) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				msg, err := honestPeerSubscription.Next(ctx)
+				if err != nil {
+					return
+				}
+				honestPeerMessages = append(honestPeerMessages, msg)
+			}
+		}
+	}(honestPeerContext)
+
+	<-time.After(2 * time.Second)
+	honestPeerCancel()
+
+	if len(honestPeerMessages) != 1 {
+		t.Fatalf("got %d messages, expected 1", len(honestPeerMessages))
+	}
+}