Bug 40249

1. Disable sending <gone/>

Following <http://xmpp.org/extensions/xep-0085.html#table-1>, we could modify our implementation of chat state notifications to send <gone/> after a timeout, rather than when the user closes the Telepathy channel. This would prevent the information leak. (I actually don't think the other client should necessarily show this information to the user, but whatever.) Disabling <gone/> while still sending other notifications violates a SHOULD by my reading of <http://xmpp.org/extensions/xep-0085.html#table-2>.

I think we should do one of two things here:

• Never send <gone/> (violating a SHOULD, and making it harder for clients to do resource (un)locking as per <http://xmpp.org/extensions/xep-0296.html>);
• Send <gone/> after a time-out.


2. Disable typing notifications.

<http://xmpp.org/extensions/xep-0085.html#table-2> and <http://xmpp.org/extensions/xep-0085.html#security> both indeed say that a client MUST provide an option to disable sending typing information. This doesn't really have to be a Gabble option—the chat UI can just not call any methods on the ChatState interface. Making it a CM option would mean you'd have to go implement this in every CM and then set the option on every single account when the user changes it.

To keep this preference consistent across chat UIs (in Gnome we have two, Empathy and the Shell), it could potentially be stored by MC—but equally it could be stored in GSettings.


3. Disable exposing operating system and client name information.

So there are a number of ways an XMPP client gives away its identity:

• XEP-0092 Software Version <http://xmpp.org/extensions/xep-0092.html>. We only report the name (Telepathy Gabble) and version (0.15.5), not OS information. Thus we comply with the MUST in <http://xmpp.org/extensions/xep-0092.html#security>.
• <identity/> elements in disco replies <http://xmpp.org/extensions/xep-0115.html#howitworks>. Our disco replies contain the software name (Telepathy Gabble), version (0.15.5) and client type (phone or pc).
• Caps node name, as included in presence pushes <http://xmpp.org/extensions/xep-0115.html#howitworks>. In our case, this is "http://telepathy.freedesktop.org/caps".
• Telepathy-specific namespaces in our caps replies (e.g. http://telepathy.freedesktop.org/xmpp/tubes), and more generally the unique set of caps that Gabble advertises.

So given that we don't send OS information, and we can't realistically avoid sending enough information to let people we've allowed onto our roster identify that we're using Gabble, I don't think there's much to do here.


4. Other things from reading the KDE bug and the screenshot.

DecloakAutomatically is “let people (specifically, other Gabble users) who aren't on our contact list call us”.

A useful privacy list-related feature to add would be “let people who aren't on our contact list IM us”. Right now, that's left up to the server. I don't think there's a bug for this. There's a draft D-Bus API for this at <http://telepathy.freedesktop.org/spec/Connection_Interface_Communication_Policy.html> but I don't think it's implemented anywhere.

(In reply to comment #1)
> A useful privacy list-related feature to add would be “let people who aren't on
> our contact list IM us”. Right now, that's left up to the server. I don't think
> there's a bug for this. There's a draft D-Bus API for this at
> <http://telepathy.freedesktop.org/spec/Connection_Interface_Communication_Policy.html>
> but I don't think it's implemented anywhere.

Communication policy is Bug #24908.

Another privacy-related thing (discussed on that bug, but IMO out-of-scope for it) is control over how much of your metadata (avatar, contact info etc.) is visible to unapproved users. The main reason we don't have this yet is that in most protocols I've encountered, this is hard-coded in the server - e.g. XMPP avatars and contact info have no defined way to change their visibility, and in most servers they're always public. For the few services where you can change visibility of your metadata (notably Skype), I think the relevant interfaces should grow more functionality, e.g. control over the visibility of your avatar should be on the Avatars interface.

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