Re: [PATCH] signed binaries support [0/4]

[Adrian Bunk <bunk@stusta.de>]

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