Using Putty only with port forwarding

From: Urs Thuermann (urs_at_isnogud.escape.de)
Date: 09/12/03 

Date: 12 Sep 2003 11:18:35 +0200

On a Unix (Solaris) server I have OpenSSH 3.4p1 running. I have setup
an account which should be used by a number of users only to do port
forwarding to a given port, but they should not be able to execute a
shell or any other command. In the authorized_keys file of that
account I did

    command="bin/false",no-pty,no-X11-forwarding,permitopen="localhost:2401"\
    ssh-rsa <key-data> <comment>

This works as expected when using the OpenSSH client with -N option to
not execute a command on the remote side, i.e.

    ssh -N -f -L 2401:localhost:2401 user@server

However, some users on Windows machines want to use Putty on the
client side, and I couldn't find a way to prevent Putty from trying to
run a shell or a command on the server. In any case the server would
run /bin/false and disconnect.

One idea I haven't tried yet is to run cat >/dev/null instead of
/bin/false, so the command doesn't exit and the connection is kept.
This is not very elegant however, compared to OpenSSH's -N option. Is
there a way to cleanly do what I want with Putty?

urs

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