From owner-freebsd-questions@FreeBSD.ORG  Tue Mar 13 00:32:20 2012
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	Mon, 12 Mar 2012 19:33:30 -0500 (CDT)
Date: Mon, 12 Mar 2012 19:33:30 -0500 (CDT)
From: Robert Bonomi <bonomi@mail.r-bonomi.com>
Message-Id: <201203130033.q2D0XUwg048729@mail.r-bonomi.com>
To: eam1edward@gmail.com, freebsd@edvax.de
In-Reply-To: <4F5E7D1F.9030703@gmail.com>
Cc: freebsd-questions@freebsd.org
Subject: Re: Editor With NO Shell Access?
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> From owner-freebsd-questions@freebsd.org  Mon Mar 12 17:46:04 2012
> Date: Mon, 12 Mar 2012 15:47:59 -0700
> From: "Edward M." <eam1edward@gmail.com>
> To: Polytropon <freebsd@edvax.de>
> Cc: freebsd-questions@freebsd.org
> Subject: Re: Editor With NO Shell Access?
>
> On 03/12/2012 03:23 PM, Polytropon wrote:
> > On Mon, 12 Mar 2012 15:19:51 -0700, Edward M. wrote:
> >> On 03/12/2012 03:10 PM, Polytropon wrote:
> >>> /etc/shells to work, but a passwd entry like
> >>>
> >>>     bob:*:1234:1234:Two-loop-Bob:/home/bob:/usr/local/bin/joe
> >>
> >>     I think this would not  let the user to login,etc
> > I'm not sure... I assume logging in is handled by /usr/bin/login,
> > and control is then (i. e. after successful login) transferred
> > to the login shell, which is the program specified in the
> > "shell" field (see "man 5 passwd") of /etc/passwd. How is
> > login supposed to know if the program specified in this
> > field is actually a dialog shell?
> >
> >  From "man 1 login" I read that many shells have a built-in
> > login command, but /usr/bin/login is the system's default
> > binary for this purpose if the "shell" (quotes deserved if
> > it is an editor as shown in my assumption) has no capability
> > of performing a login.
> >
> >
> >
>     Now i gotta try this out.   Off to
>     hosed my system.

If other configuration is set up right (e.g. /etc/shells), you can name 
*any* executable as the 'shell' field in /etc/passwd, and have it work.

"Long, long, ago", I used this for client 'on demand' system back-up.  They 
just put the tape in the drive, and logged in as the 'backup' user.


*HOWEVER* this is -not- a solution for the OP's "problem", as a skilled,
_malicious_, user can change, say,  vi(1)'s idea of what executable it
should invoke when a '!', or '!!' command is issued.