Improve IDONTWANT Flood Protection (#590)

In this PR we add in a new config parameter called `MaxIDontWantLength`
which would be very similarly used as `MaxIHaveLength` has been used of
`IHAVE` messgaes . This parameter has been set as the value of `10` now.

The main purpose is to bring how IDONTWANT messages are handled in line
with how IHAVE have been handled. We add the relevant changes to the
`handleIDontWant` method along with adding in a new regression test for
this check.

gossipsub.go

@@ -68,6 +68,7 @@ var (
 	GossipSubGraftFloodThreshold              = 10 * time.Second
 	GossipSubMaxIHaveLength                   = 5000
 	GossipSubMaxIHaveMessages                 = 10
+	GossipSubMaxIDontWantLength               = 10
 	GossipSubMaxIDontWantMessages             = 1000
 	GossipSubIWantFollowupTime                = 3 * time.Second
 	GossipSubIDontWantMessageThreshold        = 1024 // 1KB
@@ -218,6 +219,10 @@ type GossipSubParams struct {
 	// MaxIHaveMessages is the maximum number of IHAVE messages to accept from a peer within a heartbeat.
 	MaxIHaveMessages int
 
+	// MaxIDontWantLength is the maximum number of messages to include in an IDONTWANT message. Also controls
+	// the maximum number of IDONTWANT ids we will accept to protect against IDONTWANT floods. This value
+	// should be adjusted if your system anticipates a larger amount than specified per heartbeat.
+	MaxIDontWantLength int
 	// MaxIDontWantMessages is the maximum number of IDONTWANT messages to accept from a peer within a heartbeat.
 	MaxIDontWantMessages int
 
@@ -303,6 +308,7 @@ func DefaultGossipSubParams() GossipSubParams {
 		GraftFloodThreshold:       GossipSubGraftFloodThreshold,
 		MaxIHaveLength:            GossipSubMaxIHaveLength,
 		MaxIHaveMessages:          GossipSubMaxIHaveMessages,
+		MaxIDontWantLength:        GossipSubMaxIDontWantLength,
 		MaxIDontWantMessages:      GossipSubMaxIDontWantMessages,
 		IWantFollowupTime:         GossipSubIWantFollowupTime,
 		IDontWantMessageThreshold: GossipSubIDontWantMessageThreshold,
@@ -1009,9 +1015,18 @@ func (gs *GossipSubRouter) handleIDontWant(p peer.ID, ctl *pb.ControlMessage) {
 	}
 	gs.peerdontwant[p]++
 
+	totalUnwantedIds := 0
 	// Remember all the unwanted message ids
+mainIDWLoop:
 	for _, idontwant := range ctl.GetIdontwant() {
 		for _, mid := range idontwant.GetMessageIDs() {
+			// IDONTWANT flood protection
+			if totalUnwantedIds >= gs.params.MaxIDontWantLength {
+				log.Debugf("IDONWANT: peer %s has advertised too many ids (%d) within this message; ignoring", p, totalUnwantedIds)
+				break mainIDWLoop
+			}
+
+			totalUnwantedIds++
 			gs.unwanted[p][computeChecksum(mid)] = gs.params.IDontWantMessageTTL
 		}
 	}

gossipsub_spam_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/base64"
+	"fmt"
 	"strconv"
 	"sync"
 	"testing"
@@ -891,6 +892,53 @@ func TestGossipsubAttackSpamIDONTWANT(t *testing.T) {
 	<-ctx.Done()
 }
 
+func TestGossipsubHandleIDontwantSpam(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	hosts := getDefaultHosts(t, 2)
+
+	msgID := func(pmsg *pb.Message) string {
+		// silly content-based test message-ID: just use the data as whole
+		return base64.URLEncoding.EncodeToString(pmsg.Data)
+	}
+
+	psubs := make([]*PubSub, 2)
+	psubs[0] = getGossipsub(ctx, hosts[0], WithMessageIdFn(msgID))
+	psubs[1] = getGossipsub(ctx, hosts[1], WithMessageIdFn(msgID))
+
+	connect(t, hosts[0], hosts[1])
+
+	topic := "foobar"
+	for _, ps := range psubs {
+		_, err := ps.Subscribe(topic)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	exceededIDWLength := GossipSubMaxIDontWantLength + 1
+	var idwIds []string
+	for i := 0; i < exceededIDWLength; i++ {
+		idwIds = append(idwIds, fmt.Sprintf("idontwant-%d", i))
+	}
+	rPid := hosts[1].ID()
+	ctrlMessage := &pb.ControlMessage{Idontwant: []*pb.ControlIDontWant{{MessageIDs: idwIds}}}
+	grt := psubs[0].rt.(*GossipSubRouter)
+	grt.handleIDontWant(rPid, ctrlMessage)
+
+	if grt.peerdontwant[rPid] != 1 {
+		t.Errorf("Wanted message count of %d but received %d", 1, grt.peerdontwant[rPid])
+	}
+	mid := fmt.Sprintf("idontwant-%d", GossipSubMaxIDontWantLength-1)
+	if _, ok := grt.unwanted[rPid][computeChecksum(mid)]; !ok {
+		t.Errorf("Desired message id was not stored in the unwanted map: %s", mid)
+	}
+
+	mid = fmt.Sprintf("idontwant-%d", GossipSubMaxIDontWantLength)
+	if _, ok := grt.unwanted[rPid][computeChecksum(mid)]; ok {
+		t.Errorf("Unwanted message id was stored in the unwanted map: %s", mid)
+	}
+}
+
 type mockGSOnRead func(writeMsg func(*pb.RPC), irpc *pb.RPC)
 
 func newMockGS(ctx context.Context, t *testing.T, attacker host.Host, onReadMsg mockGSOnRead) {