Date: Mon, 20 Jul 1998 03:27:10 +0200 From: Andreas Klemm <andreas@klemm.gtn.com> To: Sue Blake <sue@welearn.com.au> Cc: freebsd-ports@FreeBSD.ORG Subject: Re: nethack permissions Message-ID: <19980720032710.B1203@klemm.gtn.com> In-Reply-To: <19980720111801.63717@welearn.com.au>; from Sue Blake on Mon, Jul 20, 1998 at 11:18:01AM %2B1000 References: <19980720080447.24765@welearn.com.au> <19980720023344.A2875@klemm.gtn.com> <19980720111801.63717@welearn.com.au>
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On Mon, Jul 20, 1998 at 11:18:01AM +1000, Sue Blake wrote:
> On Mon, Jul 20, 1998 at 02:33:44AM +0200, Andreas Klemm wrote:
> > On Mon, Jul 20, 1998 at 08:04:47AM +1000, Sue Blake wrote:
> > > The nethack-3.2.2 package package sets user and group to games.games
> > > and permissions 664 for every file in /usr/local/lib/nethackdir/
> > > This has been deliberately set both in PLIST and in patch-aa (I think)
> > >
> > > Running nethack fails with:
> > > Warning: cannot write scoreboard file /usr/local/lib/nethackdir/record
> > > No write permission to lock perm!
> > >
> > > What's the trick here? Are well behaved users supposed to be rewarded
> > > by adding them to the games group or something?
> >
> > /usr/local/bin/nethack is a wrapper shell script that calls the
> > real nethack binary in ${PREFIX}/lib/nethack, that runs SGID games:
> > -rwxr-sr-x 1 games games 1339278 19 Jul 14:15 nethack
>
> Sorry to be so uninformed, but I don't understand those details. Are
> you saying there's a mechanism to make it work OK for ordinary users
> even though the files are games.games? That's not how it works here.
>
> Or are you saing that it's only supposed to be played only by people in
> the games group? That'd be something I'd need to be told.
In Unix there are possibilities to set user or group id on execution
of a file. That's the "s" in a long listing
chmod o+s sets the SUID (set user id) flag
chmod g+s sets the SGID (set group id) flag
The nethack binary has the SGID bit set. This means, it
runs under the group games on execution. Since the record
file is writeable by the games group, users who play nethack
have no difficulty to play nethack and to update the record
file by the games if needed.
--
Andreas Klemm http://www.FreeBSD.ORG/~andreas
What gives you 90% more speed, for example, in kernel compilation ?
http://www.FreeBSD.ORG/~fsmp/SMP/akgraph-a/graph1.html
"NT = Not Today" (Maggie Biggs) ``powered by FreeBSD SMP''
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