From owner-freebsd-questions  Wed Oct  6 22:23:59 1999
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	id 57D6D20FB8; Wed,  6 Oct 1999 23:23:49 -0600 (MDT)
To: questions@freebsd.org
Subject: ppp across ssh (vpn)
Reply-To: <agifford@infowest.com>
From: "Aaron D. Gifford" <agifford@infowest.com>
Message-Id: <19991007052349.57D6D20FB8@infowest.com>
Date: Wed,  6 Oct 1999 23:23:49 -0600 (MDT)
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Hello,


I was playing around trying to establish a VPN connection by
using userland ppp across SSH.  I believe I have everything
set up the way the ppp.conf.sample and man page described.
It almost works.  I can watch the log files on both sides
of the tunnel.  The client works as expected.  However, on
the server side, I keep getting "tun0: Phase: Exception detected
on descriptor 0" and looking at the PPP code, it would seem
that ssh is for some reason sending out-of-band data (since
the select() man page explains that the only reason for an
exception on a file descriptor is for OOB data).

Looking at my ppp.startvpn.sh script:

  #!/bin/sh
  exec ssh -a -c blowfish -e none -l sshvpnuser -q -x vpn.server.host /usr/sbin/ppp -direct vpnserver

When I add a "-t" to force ssh to allocate a pty and run the
script by hand from the command line, sure enough, I see:

 # ./ppp.startvpn.sh
 ~ÿ}#À!}!}!} $}(}"}'}"}"}&} } } } }!}$}%Ü}%}&&á›ß}$}(À%} }
 <and other PPP-looking stuff>

BUT when I do NOT allocate a pty OR I run the script via PPP
on my client machine, nothing happens and I see the exception
previously mentioned on the server side.

I am assuming that there is some terminal-related traffic,
perhaps, that SSH is doing with OOB data that's causing the
exception, but is maybe handled when there's a pty allocated?
Please, I'm grasping at straws here, playing with stuff I know
nothing about.

Any ideas?  Suggestions?

Thanks!

Aaron out.


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