On Tue, 19 Feb 2002, Paul Robertson wrote:
:> :If you're using SSH, you should make every attempt to restrict the daemon
:> :to accepting version 2 of the protocol *only*.
:>
:> why?
:
:v2 is a good protocol.

agreed.  you are implying that v1 is bad.  this is false.

:> :The v1 fallback stuff will
:>
:> what v1 fallback stuff?
:
:Most sshd programs (including OpenSSH) will negotiate a lower version by
:default if the client wants it.

true.

:> :allow an attacker to use the horribly broken 1.5 stuff.
:>
:> what is horribly broken?
:>
:> there is a lot of FUD going around about SSH protocol 1. see
:> http://www.openssh.com/security.html for security information on SSH and
:> OpenSSH.
:
:Right, you'll want to pay attention to the line (on the page you
:reference) that says "OpenSSH has the SSH 1 protocol deficiency that might
:make an insertion attack difficult but possible.  The CORE-SDI deattack
:mechanism is ued to eliminate the common case.  Ways of solving this problem
:are being investigated, since the SSH 1 protocol is not dead yet."

i'm glad we got to the details rather than broad handwaving.  protocol 1
does have weaknesses, however it is not horribly broken as you say, and
its support in OpenSSH has hastened the migration to protocol 2 by
permitting people to better manage large migration efforts.

:If you don't *have* to support v1 clients, there's _no_ reason to support
:the v1 protocol

yes, agreed :)

:and given the weaknesses in implementations the argument
:for not supporting it is compelling.

are you referring to the deattack buffer overflow? implementation
vulnerabilities are addressed by keeping your software patched.

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