openssh PTY allocation

Damien Miller djm at
Wed Jul 27 17:25:05 EST 2011

On Sat, 23 Jul 2011, Mordechai T. Abzug wrote:

> We recently upgraded to openss 5.8p2 from a somewhat older version.
> This broke openssh login to ScreenOS devices.  These devices don't
> support PTY allocation.  Apparently, ssh now reacts to PTY allocation
> failure by failing the login.  This is a change from the previous
> behavior.  The simple workaround is ssh -T $device.

The problem is a bug in ScreenOS, it refuses pty-req channel requests
when the tty modes blob exceeds 256 bytes in length. If you want a
workaround that preserves the usability of the tty, then comment out
a couple of less-important modes in ttymodes.h and recompile


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