Stranger entered our session

[JacquesFreud]

Hi folks, today, Sunday Januari 5th at around 12:00 GMT we were enjoying a nice session (on MTKSF, genre2). All of a sudden a (way too) loud electric guitar started playing (more or less) along but there was no visible participant that we could mute. After checking Jamulus Explorer we saw an empty space amidst us. On Jamulus Live we could not see the ghost paticipant. After talking to it, there appeared a message in the chat saying ‘nou lenguege’, which probably meant it could or would not communicate. Also the spelling (and the latency of the guitar) suggests someone outside Western Europe. We left the server and continued somewhere else in a server we could hide. Any ideas?
Thanks, Jacques

[rdica]

I too have seen this behaviour, the offending IP comes from a Polish ISP. After checking log and blocking the IP via firewall, the playing stops.

A blank client joins, starts playing guitar (its real loud in comparison to others) and is sometimes not visible on the mixerboard. Sometimes it looks like it's coming from another client, other times it appears to be coming from nowhere. One day last week when an incident occcurred, my own clients mixerboard "froze". I had to diconn/reconn to server, the other participants mentioned it appeared I was the source of the errant audio, even though I had no inputs connected to my jamulus client, and I had Mute Myself engaged.

Some GeoIP information regarding the logged source address:

{
  "country": "Poland",
  "countryCode": "PL",
  "timezone": "Europe/Warsaw",
  "offset": 3600,
  "isp": "Orange Polska Spolka Akcyjna",
  "org": "Orange Polska S.A.",
  "as": "AS5617 Orange Polska Spolka Akcyjna",
  "asname": "TPNET"
}

[mcfnord]

I hope we learn how this behavior is accomplished. On my servers I can block an entire ASN. I believe we should provide a centralized IP block list all servers can easily inform and apply.

[JacquesFreud]

Our problem, of course, is that we don’t usually use a server we own. So we will have to rely on ‘outside’ help to solve the problem. Anyway, this was our first time and hopefully this is not going to be a bigger issue.

[ann0see]

along but there was no visible participant that we could mute.

This is concerning. This would mean that we have a quite serious bug in the connection handling - the isIdentified Boolean would not be set correctly. (#1243)
Edit 3.6.2 didn't have this bug fix implemented.

There are formal (mathematical) ways to model the protocol and prove invariants which would allow to find traces where this bug exists.

Doing that is non trivial (for me at least) but it can be done.

Edit: removed mention of dtinth

[rdica]

@ann0see I've seen the behaviour on a 3.9.0 server, wouldn't that have the fix already?

[ann0see]

Yes. It should have this fix.

We might need to go the formal way then. Or at least review the code in depth to maybe find out how this can happen.

[JacquesFreud]

(I was not playing on the server this time - but here we see the phenomenon again.)

[ann0see]

I think the bug got fixed in 2021: https://github.com/jamulussoftware/jamulus/blob/main/ChangeLog#380-2021-06-02

#1243

[rdica]

@JacquesFreud There is nothing that prevents a blank client from joining a server. Legitimate clients with no profile info will appear as shown above, it's not necessarily an indicator of a client connection producing the issue you initially reported.

[JacquesFreud]

@rdica : Of course, we know that. But an anonymus client would not be a reason for us to start this discussion, since that happens frequently. Only, that sort of client can be muted, or reduced in volume. Or the other clients can go solo. This time the ‘intruder’ (it may be accidentally) does not appear in the row of players in Jamulus at all (except in Jamulus Explorer, as you can see on my screen shot). That is disturbing.

[JacquesFreud]

I just checked with the players on the server MTKS.F and indeed there was an uninvited person playing along without being visible. @ann0see: I am not sure what you mean by 'the bug' that 'got fixed'. At least this problem, being a bug or not, is still there.

[ann0see]

It is still there since the server is running an outdated version of Jamulus.
(My suspicion)

The technical problem was that a client could only half connect:
A client could send audio without being identified (= without showing up in the mixer).

The bad behavior issue (playing over a running jam) can only be solved by soloing (technical solution) or writing strict rules in the welcome message - which may or may not be followed.

[JacquesFreud]

Aaaah! Then we should try and make contact with the people that run this MTKS.F Any idea how to do that?

[ann0see]

They luckily seem to have an e-mail address in their welcome message.

[JacquesFreud]

I'll contact them. Thanks.

[anprdev]

I'm using Server and Client version 3.11 and have not seen that issue yet. But have seen it on other Servers in Connection Setup Connect list.
There is sometimes a empty user.

[ann0see]

Empty users can be valid users. Just don't set a name. We cannot and should not prevent that.

[anprdev]

No issue for me just tell what I sometimes see.

[JacquesFreud]

There is a difference between totally anonymous users that can be muted by other players and totally anonymous users that are completely invisible. There is no way to stop them and they can mess up the session. It is ONLY the second category I am talking about.