[jdev] Alternate MUC Authentication Mechanisms

[Dave Cridland]

On Thu Oct 21 22:11:50 2010, Alex Milowski wrote:
> On Thu, Oct 21, 2010 at 2:00 PM, Dave Cridland <dave at cridland.net>  
> wrote:
> > On Thu Oct 21 20:08:42 2010, Alex Milowski wrote:
> >>
> >> Most simply, I want to be able to use something like DIGEST
> >> authentication to keep the shared secret from being exposed.  I  
> think
> >> that is a simple request that is fairly straightforward to  
> accomodate.
> >>  A simple hash scheme doesn't protect against replay attacks and  
> so
> >> we do need the challenge in the mix somehow.
> >
> > Who are you assuming, in this threat model, is doing the replay?
> 
> Anyone who has somehow intercepted traffic.  One simple example  
> would
> be a server that is logging stanzas for some reason.
> 
> Also, if someone's server has been compromised and they join the
> protected room, the attacker now has the authentication stanza
> sequence.  With any kind of challenge whose response includes a  
> nonce
> and uses a one-way hash, the attacker is going to have a much harder
> time decoding the response (if they can at all) and attempting to
> crack the secret.  Of course, this depends on the method chosen.   
> They
> most certainly can't use a replay attack.

But in these cases, the attacker can not only read, but spoof,  
traffic. In which case they can at least insert traffic of their  
choosing into a session.

Also, if they have the challenge and response in the clear, they can  
perform a dictionary attack offline.

I suspect you're way past hashing the room's secret and well into at  
least signing stanzas (and having a provisioning step for  
certificates, optionally), if not encrypting them.

Dave.
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