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List:       secure-shell
Subject:    Re: Need some education: Man-in-the-Middle Attacks
From:       Eygene Ryabinkin <rea-sec () codelabs ! ru>
Date:       2006-09-04 12:56:17
Message-ID: 20060904125616.GR920 () codelabs ! ru
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Nathan,
> >> I've simplified this quite a bit, but I hope this is enough to answer
> >> your question without getting too confusing.  ;-)
> >
> >Please, read the RFC 4253 and do not oversimplify the things: there is
> >no challenges in establishing the initial shared secret in SSH transport
> >layer.
> 
> You are refering to the wrong RFC, we are not talking about the
> transport layer here, we are talking about the connection layer, info
> on this can be found in RFC 4251(SSH Protocol Architecture - section
> 4.1).
Pardon me, but (citing RFC4251, section 4.1)
-----
   The server host key is used during key exchange to verify that the
   client is really talking to the correct server.  For this to be
   possible, the client must have a priori knowledge of the server's
   public host key.
-----
And the key exchange is done in the transport layer.

Moreover, section 9.3.4 called 'Man-in-the-middle' recides in the section
9.3 called 'Transport' in the same RFC4251. Don't you think that is
means something ;))

> The initial shared secret is established after you have performed the
> host key checking.
Host key checking is performed during the Diffie-Helmann exchange
at least, see RFC4253, section 8.

Am I wrong?
-- 
Eygene
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