feat: dos protected topic relay msgs based on meta field

waku/v2/protocol/relay/validators.go

@@ -0,0 +1,49 @@
+package relay
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"encoding/hex"
+
+	pubsub "github.com/libp2p/go-libp2p-pubsub"
+	"github.com/libp2p/go-libp2p/core/peer"
+	"github.com/waku-org/go-waku/waku/v2/hash"
+	"github.com/waku-org/go-waku/waku/v2/protocol/pb"
+	"go.uber.org/zap"
+	proto "google.golang.org/protobuf/proto"
+)
+
+// Application level message hash
+func MsgHash(pubSubTopic string, msg *pb.WakuMessage) []byte {
+	// TODO: Other fields?
+	return hash.SHA256([]byte(pubSubTopic), msg.Payload, []byte(msg.ContentTopic))
+}
+
+func (w *WakuRelay) AddSignedTopicValidator(topic string, publicKey *ecdsa.PublicKey) {
+	w.log.Info("adding validator to signed topic", zap.String("topic", topic), zap.String("publicKey", hex.EncodeToString(elliptic.Marshal(publicKey.Curve, publicKey.X, publicKey.Y))))
+	w.pubsub.RegisterTopicValidator(topic, func(ctx context.Context, peerID peer.ID, message *pubsub.Message) bool {
+		msg := new(pb.WakuMessage)
+		err := proto.Unmarshal(message.Data, msg)
+		if err != nil {
+			return false
+		}
+
+		msgHash := MsgHash(topic, msg)
+		signature := msg.Meta
+
+		return ecdsa.VerifyASN1(publicKey, msgHash, signature)
+	})
+}
+
+func (w *WakuRelay) SignMessage(privKey *ecdsa.PrivateKey, topic string, msg *pb.WakuMessage) error {
+	msgHash := MsgHash(topic, msg)
+	sign, err := ecdsa.SignASN1(rand.Reader, privKey, msgHash)
+	if err != nil {
+		return err
+	}
+
+	msg.Meta = sign
+	return nil
+}