[Standards] XEP-0045: Members fetching the "members" list

Matthew Wild mwild1 at gmail.com
Fri Nov 9 09:27:45 UTC 2018


Hi folks,

There are a couple of issues with this section of XEP-0045:
https://xmpp.org/extensions/xep-0045.html#modifymember

In particular, I think this text was squeezed in at a later date:

"
Note: A service SHOULD also return the member list to any occupant in
a members-only room; i.e., it SHOULD NOT generate a <forbidden/> error
when a member in the room requests the member list. This functionality
can assist clients in showing all the existing members even if some of
them are not in the room, e.g. to help a member determine if another
user should be invited. A service SHOULD also allow any member to
retrieve the member list even if not yet an occupant.
"

Firstly, I think that although it says this behaviour is conditional
on the room being members-only, I think it should more correctly be
conditional on the room being non-anonymous. Otherwise JIDs of other
users are leaked through this mechanism, even if the room is
semi-anonymous. Implementing the behaviour as defined will cause an
unexpected privacy leak for anyone who configured their room so that
JIDs are visible to "moderators only" (as per XEP-0045 config form
wording).

With that out of the way, I think the MUC should additionally allow
requesting the admin and owner lists (again, only if the room is
non-anonymous and already reveals the JIDs of occupants). There is
little point in the described feature if it is not able to retrieve
the full list of affiliated users.

I believe ejabberd already implements what I wrote above, and I'm
planning to implement the same logic in Prosody. Assuming nobody finds
a reason to object, we should probably update the XEP accordingly.

Regards,
Matthew


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