On Thu, Jun 21, 2007 at 07:34:45PM +0200, Alexander Wuerstlein wrote:
> On 070621 19:26, Adrian Bunk <[email protected]> wrote:
> > On Thu, Jun 21, 2007 at 06:29:17PM +0200, Alexander Wuerstlein wrote:
> > > On 070621 18:19, Adrian Bunk <[email protected]> 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.
>
> Even if it does not really improve security too much it can be helpful as a
> part of a larger system. For example around here we use a 'sbit-checker' that
> basically does a 'find' and 'chmod', which we would be able to replace by this
> patch.
Something that sounds as if it would increase security but doesn't
really increase security is actually bad since it gives users a false
impression of security.
> Also our patch is not solely about suid-binaries, we just implemented
> suid-checking because it seemed a simple and obvious thing to do. Our real aim
> was to implement binary signatures, which can be used in numerous security
> related checks around the kernel. Btw. if you have any good ideas where one
> could use them, please tell us :)
Linux systems usually ship and heavily use interpreters like bash, perl
or python.
Does writing an ELF loader in perl circumvent everything you want to do?
> 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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