[Security] client-to-client security :: Summary and todo's

Dirk Meyer dmeyer at tzi.de
Sat Aug 23 11:21:38 CDT 2008


Pavel Simerda wrote:
> On Sat, 23 Aug 2008 16:23:28 +0200
> Dirk Meyer <dmeyer at tzi.de> wrote:
>
>> Pedro Melo wrote:
>> > Hi,
>> >
>> > On Aug 23, 2008, at 2:12 PM, Dirk Meyer wrote:
>> >> IMHO OAuth is kind of stupid. I have to trust a server I do not
>> >> know. No, the point is that I can upload a certificate to my XMPP
>> >> server and the owner of that certificate (a bot, a client I do not
>> >> trust) can log in using SASL-EXTERNAL as me without having the
>> >> password.
>> >
>> > OAuth is not stupid. The server you do not trust is your own XMPP
>> > server. If you don't trust that, well, what are you doing connected
>> > to him?
>> 
>> Oops, sorry, I messed up OAuth and OpenID. My fault, ignore me.
>> 
>
> Neither OpenID seems stupid to me. "Stupid" is a word that only means
> you didn't bother to find more information. When one knows what's going
> on, he might use "insuitable for oure purpose because...".

OK, "stupid" is a bad word. Maybe: good good idea lost. The propblem
is that OpenID provider do not trust each other (except for blogs
maybe). E.g. every Yahoo id is an OpenID ... great. But I need a Yahoo
id to log on into flickr because they do not trust my OpenID
server. We also plan to install OpenID here at the university for some
stuff but you must have an OpenID from the university because we do
not trust Yahoo. So instead to have one OpenID (good idea) you have
several (good idea lost). But that is my opinion.

>> > I can ask my XMPP server for a opaque token that I provide to my bot
>> > and he can use that to authenticate.
>> >
>> > Having said that, I also like your "upload-certificate" idea.
>> 
>> Combine OAuth with SASL for server login .... nice one. Use your XMPP
>> connection to generate a token and give that to the new not-so-trusted
>> client and it can log in with it. The client gives away its
>> certificate for future logins.
>
> Isn't OAuth HTTP? Does it bring anything useful enough for XMPP instead
> of a need to use HTTP besides? Correct me if I'm wrong.

http://www.xmpp.org/extensions/xep-0235.html

>> Direct should be possible if only one is behind a NAT or a
>> firewall. If both are you need the help of a TURN server. Well, there
>> is STUNT (STUN over TCP) but IMHO this is a bad hack and it won't work
>> with all router. You could also add UPnP IGD to open a port on your
>> router, or the similar method apple used (I can not remember the name
>> right now, it is an IETF draft) or you can put a TURN server on your
>> router.
>
> Erm, there are many possibilities to start a session between two
> clients behind a NAT. Why do we have Jingle-ICE if not for sending data
> over NATs? UPNP is a good choice when users have access to router
> administration (home use).

UPnP is a working choice, but bad. Just google for it. Since it is
based on HTTP attackers found a way to open ports on your
router. Besides that, I do not like the idea that every app can open
ports.


Dirk

-- 
C++: The power, elegance and simplicity of a hand grenade. (Kenneth C. Dyke)



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