Re: Dynamically allocated port on reverse forward

On Tuesday 17 August 2010 06:59:33 ADFHAU wrote:
> Hi,
> 
> > If I invoke ssh this way:
> >     ssh -R 0:localhost:22 remote_ssh_server
> > 
> > ssh prints a debug message like:
> >    Allocated port 40454 for remote forward ....
> > 
> > before it drops to the shell.
> > 
> > Is there a way of querying the allocated port on the remote site to
> > make it usable within scripts? For example to execute a command via
> > ssh on the origin site in this case.
> 
> If you could determine the ancestry of the script process, back to the
> sshd driving it and then look up the pid in lsof or netstat output,
> you could probably do it.
> 
> That or if the script had access to logs and the logging level were
> high enough.

Determine the sshd process can be done via $PPID from thin the login shell:
    echo "shell pid: $$, sshd pid: $PPID"

Unfortunately using lsof -p $PPID (or /proc/$PPID) doesn't work in this case 
because the login user doesn't have read permissions to query the sshd process 
(not the sshd daemon). Unless lsof is executed as root this doesn't work.

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