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Date:      Fri, 28 Sep 2001 10:19:48 -0600
From:      Nate Williams <nate@yogotech.com>
To:        Gregory Neil Shapiro <gshapiro@FreeBSD.org>
Cc:        nate@yogotech.com (Nate Williams), cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/crypto/openssh atomicio.h auth-chall.c auth2-chall.c canohost.h clientloop.h groupaccess.c groupaccess.h kexdh.c kexgex.c log.h mac.c mac.h misc.c misc.h pathnames.h
Message-ID:  <15284.41764.337979.488670@nomad.yogotech.com>
In-Reply-To: <15284.41365.425727.42065@horsey.gshapiro.net>
References:  <200109280133.f8S1Xr363615@freefall.freebsd.org> <20010928015644.N84277-100000@achilles.silby.com> <20010928013527.A8101@xor.obsecurity.org> <15284.36137.254842.551909@nomad.yogotech.com> <15284.40817.364418.89517@horsey.gshapiro.net> <15284.40987.681415.432076@nomad.yogotech.com> <15284.41365.425727.42065@horsey.gshapiro.net>

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> >> No, it does make sense to have both. 
> 
> nate> Not in the client ocnfiguration, which I thought was being discussed.
> nate> Or am I confused?
> 
> I could be wrong (I assumed the server config).  However, even in the
> client case, could the ssh client be connecting to either a protocol 1 sshd
> or a protcol 2 sshd.  If you list "Protocol 1", attempts to contact a
> protocol 2 only sshd would fail;

Not if you type 'ssh -2'.  I just tried it.

> if you list "Protocol 2", attempts to
> contact a protocol 1 only sshd would fail;

True, but that's because there is no way to force the client to do a
SSH1 connection.  However, the client is capable of supporting ssh v1,
it's just not available to you via the command line. (Note to developers
listening, that would be a good command-line switch to add, like 
'ssh -1'.)

> if you list "Protocol 1,2",
> attempts to contact either a protocol 1 or protocol 2 only server would
> succeed.  Note that these are all assumptions and I should really check the
> code for confirmation but the man page seems to agree:
> 
>      Protocol
>              Specifies the protocol versions ssh should support in order of
>              preference.  The possible values are ``1'' and ``2''.  Multiple
>              versions must be comma-separated.  The default is ``1,2''.  This
>              means that ssh tries version 1 and falls back to version 2 if
>              version 1 is not available.

Unfortunately, as people have pointed out, the 'fallback' option doesn't
in fact work, because once a client attempts a particular protocol, it
stays with it even with the handshake fails.



Nate

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