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Date: Sun, 8 Jan 2012 22:18:07 +0100
From: Alistair Crooks <>
Cc: Florian Weimer <>
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

which allows for userspace-mounting of devices and filesystems
thereon.  Unknown provenance USB sticks are one of the use cases

	+ 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? ;-)


PS. Obvious disclaimer - I am biased.
PPS. Just reading REAMDE right now
Alistair Crooks

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