Hi,

> NFS can be forced over TCP and secured.

Or you could use 
http://www.math.ualberta.ca/imaging/snfs/

but basically you have a chicken and egg problem because your utilities used
to tunnel nfs have to be present before mounting the root, but the root is 
nfs mounted.

> Are you saying you have a method to tunnel through SSH the xdm
> host selection and authentication dialogue?  This UDP based

No, no. There is no xdm in my setup. There is a ssh login and then ssh starts
the window manager.

> transaction would either have to be keyed (if tunneled)  
> against a token, or otherwise externally keyed, to avoid a
> MitM interception and substitution at that cleartext phase,
> would it not?

With tftp, there is no possibility of avoiding MitM attack, anyway.

> I'm not saying it cannot be -- but I do not see how, and am 
> unaware of such a working implementation ... (I would sure 
> like to see such a writeup) 

You may have a look at lts_ssh (under Xtras/Patrice Dumas). There is no 
graphical login, but it could be doable. We had a discussion about that
with David Jhonston.

> > It is not secure, but it is nfs read only. The only issue seems to me man in 
> > the middle attack providing bad binaries over nfs.
> 
> This is solveable, post authentication -- the issue is earlier.

If you use tftp, it seems to me (but I may be wrong) that there is no way of
avoiding man in the middle.

> no -- X messages and keystroke interception are cleartext
> until it gets back to the X-server, unless a tunnel is set up 
> to catch all the traffic from before authentication starts -- 

That's what I do.

> there is no 'event' to transition into a trustable crypto 
> layer which initiates entirely 'across the wire'.  The keys 
> and patterns leading to the keying are exposed sufficiently 
> for reverseing, without external keying.

You're right.

Pat


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