** CONFIDENTIAL **

From: Dan Trottier <dan@maccs.dcss.mcmaster.ca>
Date: Sun, 15 Dec 1996 11:47:26 -0400
To: "David L. Potter" <csuite-dev-owner@chebucto.ns.ca>,

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Hi,

On Dec 15, 10:23am, "David L. Potter" wrote:
} Subject: Re: ** CONFIDENTIAL **
> 
> With respect to "access" to the shell... my understanding is that 
> limiting a users access to dot files is in many ways protecting them from 
> themselves and thus maintaining a 'stable' configuration across a large 
> number of users (certainly makes it a lot easier for the volunteers!)
> 
> There have always been ways to view hidden files but anyone who can use 
> vi is 'on their on hook' if they mash a dot file.
> 
> As long as a user is logging on through a regular account, their time 
> limits will remain in effect. Users that discover and use these 'holes' 
> should do suitable pennance... I favour making them write documentation 
> but then I have a bias... ;-)


I did some experimenting a while back with an older release of csuite to
resolve this particular problem. The approach I took was to replace the 
normal #!/bin/sh at the top of the cfn script with #!/usr/lib/rsh. For 
those of you not familiar with /usr/lib/rsh it is called "restricted shell"
and it allows a system administrator to limit what directories and commands
a shell user can access.

By using /usr/lib/rsh instead of /bin/sh you can make sure that if users do
break out of the lynx interface they are still fairly tightly controlled.
Most versions of Unix come with such a restricted shell.

I found no real problems using /usr/lib/rsh over /bin/sh. The trick is in
making sure you create a fairly restricted PATH variable. Restricted shell
users can use ".." in their cd commands, they can't specify commands with
path components (like /usr/bin/mail) and are restricted in other ways. The
man page on "sh" should talk about it more.


dan

-- 
Dan Trottier                                                  dan@mcmaster.ca
Dept of Computer Science & Systems           http://www.dcss.mcmaster.ca/~dan
McMaster University, Hamilton, Ontario                  (905) 525-9140 x23444

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