Re: Digital UNIX/Irix mesg problem

[earthpig () YOYO CC MONASH EDU AU (Andrew Snare)]

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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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