RedHat 7.0 openssh-2.2.0p1-5 vs ssh 2.3.0

[Richard E. Silverman]

On Sat, 14 Oct 2000, Jack Howarth wrote:

> Hello,
>      I am using RedHat's most recent openssh-2.20p1-5 srpm recompiled
> on Linuxppc under glibc 2.1.95/Linux 2.4-test10pre2/gcc 2.95.3(cvs).
> I have noticed an oddity when connecting to machines running ssh
> 2.3.0's sshd2 server. While the connections occur with no problem
> after awhile the connection fails when idle with the following 
> error message...
> 
> Hm, dispatch protocol error: type 20 plen 136
> 
> Any idea why this is happening?

The "awhile" will be exactly an hour from the start of the session,
regardless of whether it's idle.  The problem is that ssh-2.3.0 implements
session re-keying, and OpenSSH does not.  The default rekey interval is 1
hour, and the OpenSSH client dies when it gets the rekey request.

The rekey is not optional (the client can't refuse to do it), so until
OpenSSH does rekeying, the only way to avoid this is to turn off rekeying
in the server: set RekeyIntervalSeconds to 0.

-- 
  Richard Silverman
  slade at shore.net