Date: Thu, 21 Jun 2007 19:23:44 +0200
From: Adrian Bunk <bunk@stusta.de>
To: Alexander Wuerstlein <arw@arw.name>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] signed binaries support [0/4]
Message-ID: <20070621172344.GQ12950@stusta.de>
References: <20070621155516.GA6838@faui01.informatik.uni-erlangen.de> <20070621161758.GP12950@stusta.de> <20070621162917.GB9741@cip.informatik.uni-erlangen.de>
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On Thu, Jun 21, 2007 at 06:29:17PM +0200, Alexander Wuerstlein wrote:
> On 070621 18:19, Adrian Bunk <bunk@stusta.de> wrote:
> > On Thu, Jun 21, 2007 at 05:55:16PM +0200, Johannes Schlumberger wrote:
> > 
> > > Hi,
> > 
> > Hi Johannes,
> > 
> > > We (two students of CS) built a system for signing binaries and verifying them
> > > before executing. Our main focus was to implement a way to inhibit execution
> > > of suid-binaries, which are not trustworthy (i.e. not signed).
> > >...
> > 
> > doesn't anyone who is able to install a not trustworthy suid-binary 
> > already have the priviliges to do anything he wants to without requiring 
> > an suid bit?
> 
> Yes, quite correct in most cases. But if you have taken control of a computer
> on of the more common ways to keep the control for some time is the
> installation of a suid-binary (e.g. as part of a rootkit). 

There are so many ways for manipulating a computer that controlling 
setuid binaries hardly brings a real security gain.

> One could also imagine a scenario where an attacker controls some filesystems
> (on external storage perhaps) where he can of course manipulate the suid bit,
> but he does not have direct control over the attacked system unless he can
> execute that file.

And unless the filesystem is mounted without nosuid...

> Ciao,
> 
> Alexander Wuerstlein.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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