AFS and tokenforwarding

Nicolas Williams Nicolas.Williams at
Fri Oct 5 05:23:59 EST 2001

I was thinking that AFS token passing would be mixed with Kerberos
network authentication. If it's Kerberos V then I'd expect mutual auth
to be used.

Then again, I've ever used SSHv1 with Kerberos -- only SSHv2 with
GSS/Kerberos (thanks to Simon Wilkinson's patches) and SSH w/ GSS *does*
require mutual authentication.

So how will you make AFS token passing in SSHv2?

I think you'll need to store .ssh dirs not in home directories, but
somewhere that allows world readability. With Secure NFS this problem
goes away since any client with root/fqdn at REALM principals gets read
access as "nobody" so that, if ~/.ssh and ~/.ssh/authorized_keys* are
world-readable, then sshd can read them before installing the user's
creds (alternatively, it can install them early, then remove them if
authorization fails).


On Thu, Oct 04, 2001 at 09:15:23PM +0200, Bjoern Groenvall wrote:
> >>>>> "Nicolas" == Nicolas Williams <Nicolas.Williams at> writes:
> Nicolas> If the token is forwarded before authentication then you
> Nicolas> don't know if the server is really who you think it is, so
> Nicolas> you might be forwarding your token to an impostor. Ooops.
> I don't think any of the ssh (at least v1) authentication mechanisms
> really authenticate the server. A masquerading server can always
> forward the authentication information to the real server and use that
> response as a legitimate reply. Thus you may still be passing
> credentials down to an impostor. Either way you do it, you can always
> be fooled. A similar problem exists with the common "pass passwords in
> the clear" methods used by ssh. Hopefully this is fixed in v2 but I
> never really bothered to check.
> /Björn
> -- 
>   _     _                                               ,_______________.  
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> Swedish Institute of Computer Science                  |               ||
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