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Date:      Tue, 10 Dec 1996 15:35:12 +0100 (MET)
From:      Christoph Kukulies <kuku@gilberto.physik.rwth-aachen.de>
To:        roberte@mep.ruhr-uni-bochum.de (Robert Eckardt)
Cc:        kuku@gilberto.physik.rwth-aachen.de, dwhite@resnet.uoregon.edu, freebsd-questions@freefall.freebsd.org
Subject:   Re: xconsole - /dev/console
Message-ID:  <199612101435.PAA15354@gilberto.physik.rwth-aachen.de>
In-Reply-To: <199612101238.NAA06444@ghost.mep.ruhr-uni-bochum.de> from Robert Eckardt at "Dec 10, 96 01:38:52 pm"

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> > > On Mon, 9 Dec 1996, Christoph Kukulies wrote:
> > > 
> > > > Is there a way to allow a normal user to use xconsole or would
> > > > opening /dev/console to the world compromise security?
> > > 
> > > ?  People have to run startx or log into a xdm-controlled terminal, so
> > > they're authenticated.
> > 
> > It's not that I want to inhibit users seeing the console
> > messages, it was just the point if changing /dev/console's permissions
> > could compromise security anyhow.
> > I've seen /dev/console having crw--w--w- on a Linux system.
> 
> This is usually done by the Give/TakeConsole scripts of xdm.
> TakeConsole:
>   chmod 622 /dev/console            <<<---------
>   chown root /dev/console
> GiveConsole:
>   # By convention, both xconsole and xterm -C check that the
>   # console is owned by the invoking user and is readable before attaching
>   # the console output.  This way a random user can invoke xterm -C without
>   # causing serious grief.
>   #
>   chown $USER /dev/console
> 
> This way only the user at the console logging in via xdm can use
> /dev/console, but all can _send_messages_ there. Thus, console isn't
> opened to "the world" this way.

This may work for the xdm login mechanism but it doesn't work for
startx. I don't use xdm for variuous reasons. First off I don't have a
des xdm - I have des passwords but I havn't yet had time to compile 
a DES xdm. Secondly, xdm always was prone to memory leaks or was
causing the Xserver to leak memory. I don't know how it is
presently but that's why I'm always afraid using xdm.


> I don't know whether this has serious implications on security (like world
> readable disk devices :-)
> 
> Robert
> 
> > --Chris Christoph P. U. Kukulies kuku@gil.physik.rwth-aachen.de
> 
> -- 
> Robert Eckardt                \\ FreeBSD -- solutions for a large universe.(tm)
> RobertE@MEP.Ruhr-Uni-Bochum.de \\       What do you want to boot tomorrow ?(tm)
> http://WWW.MEP.Ruhr-Uni-Bochum.de/~roberte
> For PGP-key finger roberte@gluon.MEP.Ruhr-Uni-Bochum.de
> 

--Chris Christoph P. U. Kukulies kuku@gil.physik.rwth-aachen.de



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