On Mon, Jun 03, 2002 at 01:32:57PM +0200, Ralf S. Engelschall wrote:
> On Mon, Jun 03, 2002, Michael Schloh von Bennewitz wrote:
> 
> > On Fri, May 31, 2002 at 04:48:08PM +0200, Ralf S. Engelschall wrote:
> > >   Log:
> > >     - default to "Protocol 2,1" in server and "Protocol 1,2" in client
> > > 
> > Interessant. Warum ist hier mehr attraktiv den ersten Version beim Klient? Ich
> > nehme an, dass der Grund eine zweite version den SSH Protokol zu schaffen hat
> > mit Sicherheitsproblemen den ersten zu tun.
> 
> Using protocol 1 in the client isn't more attractive, it is a
> work-around to make sure people to not get confused because they no
> longer connect to their servers. The problem is this: server supports
> SSH-1 and SSH-2, but user has only his SSH-1 key on the server (as it
> is the case for most servers I know); user now connects with "Protocol
> 2,1" to server; client and server recognize that SSH-2 should be
> tried; client has no SSH-2 key so SSH-2 connection fails; client stop
> processing because it _DOES NOT_ try again or fallback to SSH-1 (where
> the key exists). The SSH-2 to SSH-1 fallback only works if one side does
> not speak SSH-2 at all. But if both sides speak SSH-2 but suitable key
> is missing, processing stops immediately without any fallbacks. As a
> result the user gets a permission denied and only can connect with "ssh
> -1 ...". So, unless all users have also SSH-2 keys (and stored on the
> server) it is wise they _by default_ use "Protocol 1,2".


So far, I too have configured the openssh I distribute to have the client
default to Protocol 1,2.  However, one of my users pursuaded me I should
reverse it now rather than later because the longer I wait the larger the
impact will be as more users get on board.  Better to bite the bullet now.
Actually, most of my company is still on a ssh-1.2.27 variant and I plan to
upgrade them to openssh soon.  I think it would be better have just one
time of upgrade pain, forcing people to generate a protocol 2 key or switch
to protocol 1 now, rather than switching the default protocol on people in
a future upgrade.

- Dave Dykstra
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