[4394] in bugtraq
Re: Digital UNIX/Irix mesg problem
daemon@ATHENA.MIT.EDU (Andrew Snare)
Fri May 2 01:55:21 1997
Date: Thu, 1 May 1997 14:33:22 +1000
Reply-To: Andrew Snare <earthpig@YOYO.CC.MONASH.EDU.AU>
From: Andrew Snare <earthpig@YOYO.CC.MONASH.EDU.AU>
X-To: John Sheehy <jes@GROVE.UFL.EDU>
To: BUGTRAQ@NETSPACE.ORG
In-Reply-To: "Your message of Tue, 29 Apr 1997 18:35:04 -0400."
<Pine.OSF.3.95.970429182405.14400Q-100000@bay>
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John Sheehy recently penned:
/*
* On Tue, 29 Apr 1997, Tom Leffingwell wrote:
*
* | This is rather stupid and not much of a bug, but it shouldn't
* | happen. Basically, the permissions on your tty are set correctly, with
* | messages on, during login. If you turn them off, and then turn them back
* | on, your tty becomes world writable. (Actually, you don't have to turn
* | them off, mesg y automatically sets permissions that way). I don't
* | remember that being that way in Digital UNIX 3, but I can't think of a box
* [...]
*
* On Digital Unix 3.2D-1:
[results snipped]
* OSF1 ns V3.2 62 alpha
[and again]
* This is rather annoying. Time to write a script to replace mesg.
*/
Yep, it is annoying. In writing such a script I also found that screen
(when running suid root) also sets the owner of the pseudo-tty's it
allocates to have the wrong owning group -- it sets the owning group to be
the primary group the user is in, not the terminal group. This means that
for write to work mesg y must indeed make the group world-writeable. My
solution has been to just detect the owning group. If it's not terminal,
spit out a warning message and revert to the old buggy behaviour. YMMV.
- Andrew
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