Date: Sun, 10 Sep 2006 12:41:05 +0200
From: David Madore <david.madore@ens.fr>
To: Pavel Machek <pavel@ucw.cz>
Cc: Linux Kernel mailing-list <linux-kernel@vger.kernel.org>
Subject: Re: patch to make Linux capabilities into something useful (v 0.3.1)
Message-ID: <20060910104105.GB5865@clipper.ens.fr>
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On Sat, Sep 09, 2006 at 11:40:38AM +0000, Pavel Machek wrote:
> > > If you can find another uid to hijack, that other uid has bad
> > > problems. And I do not think you'll commonly find another uid to
> > > hijack.
> > 
> > How about another gid, then?  Should we reset all caps on sgid exec?
> 
> Yes. Any setuid/setgid exec is a security barrier, and weird (or new)
> semantics may not cross that barrier.

Right, so what I was saying was: if you reset all regular caps on sgid
exec, anyone can trivially reset all regular caps by creating a sgid
program (users are always members of a great many groups so "finding
another gid to hijack" is trivial).  So CAP_REG_SXID needs to be off
all the time, so we lose again.

But I'll make this a securebit ("unsanitized sxid"), with the behavior
you advertise as default (0).

> > Ultimately a compromise is to be reached between security and
> > flexibility...  The problem is, I don't know who should make the
> > decision.
> 
> Go for security here. (Normally, consensus on the list is needed for
> merging the patch).

I am now completely convinced the patch will never be merged. :-(
Linux will have useless caps forever...

-- 
     David A. Madore
    (david.madore@ens.fr,
     http://www.madore.org/~david/ )
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