Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pasteur!ucbvax!tut.cis.ohio-state.edu!rutgers!bellcore!faline!thumper!ulysses!mhuxo!mhuxu!att!chinet!les
From: les@chinet.chi.il.us (Leslie Mikesell)
Newsgroups: comp.unix.wizards
Subject: Re: lpr output filters
Message-ID: <8185@chinet.chi.il.us>
Date: 10 Apr 89 03:49:31 GMT
References: <1158@novavax.UUCP> <48300020@hcx3> <1159@novavax.UUCP>
Reply-To: les@chinet.chi.il.us (Leslie Mikesell)
Organization: Chinet - Public Access Unix
Lines: 20

In article <1159@novavax.UUCP> gls@novavax.UUCP (Gary Schaps) writes:
>> > Does it seem reasonable to try to create an lpr output filter which 
>> > selectively prevents certain files from being printed?

>I would like to "protect" certain files by making them "view only". 

Not possible if the users are moderately competent.  If the user has
read access he can use many methods of printing which might circumvent
anything you might try to filter out (like reading into an editor and
extracting the interesting pieces).  The best you could do would be
to make the files unreadable by normal users and provide a setuid program
that displays the contents only if the output is directly to a terminal.
Then you still have to deal with the possibility of hardcopy terminals,
printers on the aux port, and PC's emulating terminals with the session
being logged to disk or printer.  If you don't have dial-up access,
perhaps those possibilities would not be a problem but there are still
things that might be done with ptys or rlogin sessions back to the
same host that would fool your display program.

Les Mikesell