I sincerely think you're all missing the point here.
The observation is in fact something that can be used by rootkit
writers or developers of other forms of malware. Meaning that this is
always something else that people who work to make Linux a safer
environment will have to watch and look for (think of rootkit
detectors, for an example). I'm glad they've reported it, as someone
might be using it already for God knows how long. All very stealthy.
All I can think is that this is a very good opportunity for us to
rethink some designs and see if a little bit of effort wouldn't be
worth the advantages a patch might bring.
Don't get me wrong. I truly appreciate the freedom that Linux
provides, but this "well, root should be able to do anything, anyway"
mentality won't get this OS anywhere security-wise. If everyone
thought like that, then I'd guess that sys_call_table would be an
exported symbol until now, linux-gate wouldn't be randomized, and so
on.
Just a thought.
Cheers,
Julio Auto
On 10/4/06, Chase Venters <[email protected]> wrote:
> On Tuesday 03 October 2006 14:12, SHELLCODE Security Research wrote:
> > Hello,
> > The present document aims to demonstrate a design weakness found in the
> > handling of simply
> > linked lists used to register binary formats handled by
> > Linux kernel, and affects all the kernel families
> > (2.0/2.2/2.4/2.6), allowing the insertion of infection modules in
> > kernel? space that can be used by malicious users to create infection
> > tools, for example rootkits.
>
> Yay, you've been Slashdotted!
>
> Question: Why did you personally submit this to Slashdot when it is absolutely
> clear that the observation is akin to figuring out a process can call fork()
> and exec() and become "/bin/rm" with an argv of "/bin/rm", "-rf", and "*"?
>
> Is this what you call good marketing?
>
> > POC, details and proposed solution at:
> > English version: http://www.shellcode.com.ar/docz/binfmt-en.pdf
> > Spanish version: http://www.shellcode.com.ar/docz/binfmt-es.pdf
> >
>
> Thanks,
> Chase
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
On Tuesday 03 October 2006 23:08, Julio Auto wrote:
> I sincerely think you're all missing the point here.
>
> The observation is in fact something that can be used by rootkit
> writers or developers of other forms of malware. Meaning that this is
> always something else that people who work to make Linux a safer
> environment will have to watch and look for (think of rootkit
> detectors, for an example). I'm glad they've reported it, as someone
> might be using it already for God knows how long. All very stealthy.
> All I can think is that this is a very good opportunity for us to
> rethink some designs and see if a little bit of effort wouldn't be
> worth the advantages a patch might bring.
>
> Don't get me wrong. I truly appreciate the freedom that Linux
> provides, but this "well, root should be able to do anything, anyway"
> mentality won't get this OS anywhere security-wise. If everyone
> thought like that, then I'd guess that sys_call_table would be an
> exported symbol until now, linux-gate wouldn't be randomized, and so
> on.
Julio,
No one is trying to paper over any real problem here. This attack relies on
being able to insert an arbitrary kernel module into the running kernel. If
you can do that, you can literally load _any_ code you want. Attaching to the
binfmt callback list is one of about a billion things you could do.
If you're worried about this kind of attack, the only way to be safe is to
turn off kernel module support or use another mechanism to restrict who can
load them.
I think it's a little bit silly for a "security researcher" to simultaneously
publish stuff in the news and in a developer community, especially if the
threat is totally phony to begin with.
> Just a thought.
>
> Cheers,
>
> Julio Auto
Thanks,
Chase
> On 10/4/06, Chase Venters <[email protected]> wrote:
> > On Tuesday 03 October 2006 14:12, SHELLCODE Security Research wrote:
> > > Hello,
> > > The present document aims to demonstrate a design weakness found in the
> > > handling of simply
> > > linked lists used to register binary formats handled by
> > > Linux kernel, and affects all the kernel families
> > > (2.0/2.2/2.4/2.6), allowing the insertion of infection modules in
> > > kernel? space that can be used by malicious users to create infection
> > > tools, for example rootkits.
> >
> > Yay, you've been Slashdotted!
> >
> > Question: Why did you personally submit this to Slashdot when it is
> > absolutely clear that the observation is akin to figuring out a process
> > can call fork() and exec() and become "/bin/rm" with an argv of
> > "/bin/rm", "-rf", and "*"?
> >
> > Is this what you call good marketing?
> >
> > > POC, details and proposed solution at:
> > > English version: http://www.shellcode.com.ar/docz/binfmt-en.pdf
> > > Spanish version: http://www.shellcode.com.ar/docz/binfmt-es.pdf
> >
> > Thanks,
> > Chase
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel"
> > in the body of a message to [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
On Oct 04, 2006, at 00:08:57, Julio Auto wrote:
> I sincerely think you're all missing the point here.
No, _you're_ missing the point.
> The observation is in fact something that can be used by rootkit
> writers or developers of other forms of malware.
This attack relies on being able to load an arbitrary attacker-
defined kernel module. Full Stop. If you can load code into
privileged mode it's game over regardless of what other designs and
restrictions are in place. The "default" security model is that only
root can load kernel code, but using SELinux or other methods it's
possible to entirely prevent anything from being loaded after system
boot or written to the kernel or bootloader images.
If the attacker gains kernel code access, it doesn't matter what
"simply linked list" or whatever other garbage is being used, they
can just overwrite the existing ELF loader with their shellcode if
they want. Or they could insert a filesystem patch which always
loads a virus into any ELF binary at load. Or they could just fork a
kernel thread and run their shellcode there. Or they could load a
copy of Windows from the CD drive and boot into that from Linux.
Kernel-level access implies ultimate trust and security, and
*nothing* is going to change that.
Cheers,
Kyle Moffett
I'm thinking of starting a 'security research' firm and pointing out
that if you can physically swap the boot device on a machine and
reboot you can run 'arbitrary code'.
I might also point out the new boot device could have NetBSD on it,
and gloss over the hundreds of other things that would be both
possible and expectedly so...
On 04/10/06, Kyle Moffett <[email protected]> wrote:
> On Oct 04, 2006, at 00:08:57, Julio Auto wrote:
> > I sincerely think you're all missing the point here.
>
> No, _you're_ missing the point.
>
> > The observation is in fact something that can be used by rootkit
> > writers or developers of other forms of malware.
>
> This attack relies on being able to load an arbitrary attacker-
> defined kernel module. Full Stop. If you can load code into
> privileged mode it's game over regardless of what other designs and
> restrictions are in place. The "default" security model is that only
> root can load kernel code, but using SELinux or other methods it's
> possible to entirely prevent anything from being loaded after system
> boot or written to the kernel or bootloader images.
>
> If the attacker gains kernel code access, it doesn't matter what
> "simply linked list" or whatever other garbage is being used, they
> can just overwrite the existing ELF loader with their shellcode if
> they want. Or they could insert a filesystem patch which always
> loads a virus into any ELF binary at load. Or they could just fork a
> kernel thread and run their shellcode there. Or they could load a
> copy of Windows from the CD drive and boot into that from Linux.
>
> Kernel-level access implies ultimate trust and security, and
> *nothing* is going to change that.
>
> Cheers,
> Kyle Moffett
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
Ar Maw, 2006-10-03 am 23:25 -0500, ysgrifennodd Chase Venters:
> I think it's a little bit silly for a "security researcher" to simultaneously
> publish stuff in the news and in a developer community, especially if the
> threat is totally phony to begin with.
Given the way it was carefully fed to slashdot I suspect it may in fact
be someone with brains who wanted to make slashdot look stupid and spoof
them. If so they certainly scored 10/10 on that.
On Wed, 2006-10-04 at 15:55 +0100, Alan Cox wrote:
> Ar Maw, 2006-10-03 am 23:25 -0500, ysgrifennodd Chase Venters:
> > I think it's a little bit silly for a "security researcher" to simultaneously
> > publish stuff in the news and in a developer community, especially if the
> > threat is totally phony to begin with.
>
> Given the way it was carefully fed to slashdot I suspect it may in fact
> be someone with brains who wanted to make slashdot look stupid and spoof
> them. If so they certainly scored 10/10 on that.
Brains are required to make slashdot look stupid ?