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Date:      Mon, 11 Dec 2000 01:35:51 -0500
From:      Chris Richards <richards+bsd@CS.Princeton.EDU>
To:        Robert Watson <rwatson@FreeBSD.org>
Cc:        Garrett Wollman <wollman@khavrinen.lcs.mit.edu>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/etc crontab
Message-ID:  <20001211013551.A30301@ethel.williams.edu>
In-Reply-To: <Pine.NEB.3.96L.1001210142216.24257C-100000@fledge.watson.org>; from rwatson@FreeBSD.org on Sun, Dec 10, 2000 at 02:26:05PM -0500
References:  <200012101856.NAA30441@khavrinen.lcs.mit.edu> <Pine.NEB.3.96L.1001210142216.24257C-100000@fledge.watson.org>

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On Sun, Dec 10, 2000 at 02:26:05PM -0500, Robert Watson wrote:

> > > As such, any random process running as any random user can acquire
> > > the lock and stack up all your periodic scripts,
> > 
> > If and only if they are allowed to open the file in the first place.
> 
> This is correct.  However, this does not apply to the periodic binary,
> directories, or most base system files, unfortunately.  Maybe we need a
> /var/run/locks with appropriate turnstile files with appropriate modes
> set.

I don't understand what you mean to say here.  What's to prevent the
creation of a /var/run/periodic.lock, for example, with mode 600?
Then periodic, running as root, will be able to aquire the advisory
lock on this file, and ordinary users won't.  The possibility of a DoS
is thus eliminated.

Am I missing something obvious?  In the quoted material above, you
seem to be suggesting that it is insecure to use most base system
files as lock files.  True -- but what would be the point in doing so?

-chris


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