crdt: fix pubsub validation for crdt messages

Currently, it was not looking at the signer of the message, but at the
peer that relayed it, to verify the validity of the message.

This caused that under certain gossip graph configurations, some nodes would only
get messages via untrusted peers, and thus be unable to sync the chain.

consensus/crdt/consensus.go

@@ -162,8 +162,13 @@ func (css *Consensus) setup() {
 	// from trusted sources)
 	err = css.pubsub.RegisterTopicValidator(
 		topicName,
-		func(ctx context.Context, p peer.ID, msg *pubsub.Message) bool {
-			return css.IsTrustedPeer(ctx, p)
+		func(ctx context.Context, _ peer.ID, msg *pubsub.Message) bool {
+			signer := msg.GetFrom()
+			trusted := css.IsTrustedPeer(ctx, signer)
+			if !trusted {
+				logger.Debug("discarded pubsub message from non trusted source %s ", signer)
+			}
+			return trusted
 		},
 	)
 	if err != nil {