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Date: Sun, 8 Jan 2012 22:18:07 +0100
From: Alistair Crooks <agc@...bsd.org>
To: oss-security@...ts.openwall.com
Cc: Florian Weimer <fw@...eb.enyo.de>
Subject: Re: Malicious devices & vulnerabilties
On Mon, Jan 09, 2012 at 03:48:20AM +0800, Eugene Teo wrote:
> On 01/08/2012 07:19 PM, Florian Weimer wrote:
> > * Xi Wang:
> >
> >> I am wondering where to draw the line. Should such device drivers
> >> be considered vulnerable or not? Thanks.
> >
> > I think they should be considered vulnerable. Some applications need
> > some robustness to attacks even from the local console (e.g., student
> > computer rooms).
> >
> > USB is also a popular transport in many air-gapped environments.
>
> I would consider them vulnerable with low security impacts. If you are
> fixing such issues, do post them to the list.
One very interesting datapoint here is Antti Kantee's rump subsystem
in NetBSD
http://www.netbsd.org/docs/rump/
http://blog.netbsd.org/tnf/entry/runnable_userspace_meta_programs_in
which allows for userspace-mounting of devices and filesystems
thereon. Unknown provenance USB sticks are one of the use cases
mentioned.
+ rump_msdos: USB sticks with FAT file systems are a common
sight. Mounting an untrusted image from removable media with
the file system driver running in the kernel is risky in many
ways: inopportune unplugging of the media or a corrupted file
system may have adverse effects such as system crashes or
worse. By using the rump_msdos command instead of
mount_msdos, the file system service runs in userspace and is
accessed via puffs. This isolates the main kernel from any
resulting problems such as buffer overflows.
The usage of mount_msdos and rump_msdos are equivalent...
If USB is a transport in air-gapped environments, I personally have a
concern with that. A good thing airgaps aren't used for anything in RL,
right? ;-)
Regards,
Alistair
PS. Obvious disclaimer - I am biased.
PPS. Just reading REAMDE right now
--
Alistair Crooks
{agc,security-officer}@...BSD.org
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