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From: jochen fritz <jfritz@rdrc.rpi.edu>
Subject: Re: xfree86 only works for root?
Message-ID: <h!f32hq@rpi.edu>
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Organization: Rensselaer Polytechnic Institute, Troy, NY
References: <MfIsYa600WBMM8XVtb@andrew.cmu.edu> <1j0q48INNmq1@matt.ksu.ksu.edu> <1993Jan17.143000.28887@cbnewsh.cb.att.com>
Date: Sun, 17 Jan 1993 22:25:32 GMT
Lines: 33
In article <1993Jan17.143000.28887@cbnewsh.cb.att.com> billc@pegasus.ATT.COM (Bill Carpenter) writes:
>
.
.
.
.
>However, there are a couple of other options which my come in handy
>for those in places where it's less convenient to have yet annother
>setUid program.
>
>[1] On Suns and many other places, /etc/utmp is 0666 perms, so anyone
>can write into it. I don't know what the security implications are,
>but it cures this xterm problem.
>
>[2] There is an option for xterm to tell it to not bother trying to
>write in /etc/utmp. I think it's "-ut", but I don't have the man page
>handy. (On the other hand, my xterm isn't can't write into /etc/utmp
>and I don't use that option. Yet, my xterms run without complaining,
>so there may be something to that PTY stuff on your system after all.)
>
There is a third, and IMHO far more iomportant reason: xterm will
chown the slave end of the pty (/dev/ttyp*). This allows it to then
chmod the pty to rw--w--w-, so that only the user of the xterm can
read from it or send commands to the user's shell to be executed by
him. This also prevents putting a trojan on the pty to snoop the
user's commands, and allows the user to chmod the terminal 700 if
others are causing problems.
-joe (jfritz@rdrc.rpi.edu)
--
-joe (jfritz@rdrc.rpi.edu)