Re: Steve Bellovin: ssh2 mitm attack?

[Dave Dykstra <dwd%bell-labs.com@localhost>]

I pointed this out on the openssh-unix-dev mailing list in January
    http://marc.theaimsgroup.com/?l=openssh-unix-dev&m=101069187914700&w=2
and there was some discussion but Marcus didn't seem to think it was
worth worrying about.

- Dave Dykstra


On Fri, Jul 26, 2002 at 03:55:23PM -0400, Bill Sommerfeld wrote:
> [before anyone panics, this is a variant on the "hijack the connection
> and substitute a different host key".
> 
> The problem described here is that at least some implementations
> effectively maintain separate host key databases per (host key
> algorithm, major protocol revision) pair, so that you get the
> non-scary "no host key known" user prompt rather than the scary "host
> key has changed" when a man-in-the-middle attacker does an
> upgrade/downgrade/host key algorithm change.
> 
> 					- Bill]
> 				
> ------- Forwarded Message
> 
> X-Mailer: exmh version 2.5 07/13/2001 with nmh-1.0.4
> From: Steve Bellovin <smb%research.att.com@localhost>
> To: sommerfeld%eng.sun.com@localhost
> Subject: ssh2 mitm attack?
> Cc: jis%mit.edu@localhost
> Mime-Version: 1.0
> Content-Type: text/plain; charset=us-ascii
> Date: Thu, 25 Jul 2002 07:48:54 -0400
> Message-Id: <20020725114855.358CD7B4D%berkshire.research.att.com@localhost>
> Content-Length: 363
> 
> Bill, have a look at http://www.phrack.org/show.php?p=59&a=11http://www.phrack.org/show.php?p=59&a=11
> and in particular at the ssh2-only attack.  Are any changes to the 
> drafts necessary?  (I haven't had a chance to read them in light of 
> this advisory.)
> 
> 		--Steve Bellovin, http://www.research.att.com/~smb (me)
> 		http://www.wilyhacker.com ("Firewalls" book)
> 
> 
> 
> ------- End of Forwarded Message