MicroSD assigned to dom0 and not to sys-usb

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468ezc+5r0...@guerrillamail.com

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Aug 1, 2016, 3:35:29 PM8/1/16
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Hi,

My MicroSD while attached is assigned to dom0 and not sys-usb as is supposed. Notwithstanding, USB devices are still assigned to sys-usb.

Is this the intended behavior? Doesn't this increases, in the same manner as usb devices does, the surface attack in dom0?

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Marek Marczykowski-Górecki

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Aug 1, 2016, 3:37:16 PM8/1/16
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On Mon, Aug 01, 2016 at 07:35:26PM +0000, 468ezc+5r0fnwy87qeag via qubes-users wrote:
> Hi,
>
> My MicroSD while attached is assigned to dom0 and not sys-usb as is supposed. Notwithstanding, USB devices are still assigned to sys-usb.
>
> Is this the intended behavior? Doesn't this increases, in the same manner as usb devices does, the surface attack in dom0?

Your (micro)SD card reader is probably not a USB device, but PCI device.
Yes, it's better to assign it to some VM - sys-usb is ok. You can do
this in VM settings - "Devices" tab.

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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Franz

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Aug 1, 2016, 5:47:26 PM8/1/16
to Marek Marczykowski-Górecki, 468ezc+5r0...@guerrillamail.com, qubes...@googlegroups.com
On Mon, Aug 1, 2016 at 4:37 PM, Marek Marczykowski-Górecki <marm...@invisiblethingslab.com> wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

On Mon, Aug 01, 2016 at 07:35:26PM +0000, 468ezc+5r0fnwy87qeag via qubes-users wrote:
> Hi,
>
> My MicroSD while attached is assigned to dom0 and not sys-usb as is supposed. Notwithstanding, USB devices are still assigned to sys-usb.
>
> Is this the intended behavior? Doesn't this increases, in the same manner as usb devices does, the surface attack in dom0?

Your (micro)SD card reader is probably not a USB device, but PCI device.
Yes, it's better to assign it to some VM - sys-usb is ok. You can do
this in VM settings - "Devices" tab.


any hint to identify which is the PCI device that handles SD cards?

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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Marek Marczykowski-Górecki

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Aug 1, 2016, 5:59:09 PM8/1/16
to Franz, 468ezc+5r0...@guerrillamail.com, qubes...@googlegroups.com
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On Mon, Aug 01, 2016 at 06:47:21PM -0300, Franz wrote:
> On Mon, Aug 1, 2016 at 4:37 PM, Marek Marczykowski-Górecki <
> marm...@invisiblethingslab.com> wrote:
>
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA256
> >
> > On Mon, Aug 01, 2016 at 07:35:26PM +0000, 468ezc+5r0fnwy87qeag via
> > qubes-users wrote:
> > > Hi,
> > >
> > > My MicroSD while attached is assigned to dom0 and not sys-usb as is
> > supposed. Notwithstanding, USB devices are still assigned to sys-usb.
> > >
> > > Is this the intended behavior? Doesn't this increases, in the same
> > manner as usb devices does, the surface attack in dom0?
> >
> > Your (micro)SD card reader is probably not a USB device, but PCI device.
> > Yes, it's better to assign it to some VM - sys-usb is ok. You can do
> > this in VM settings - "Devices" tab.
> >
> >
> any hint to identify which is the PCI device that handles SD cards?

It should be something obvious - like "SD Host controler", or "SD/MMC
card reader".

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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Jeremy Rand

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Aug 2, 2016, 10:56:39 PM8/2/16
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Marek Marczykowski-Górecki:
> On Mon, Aug 01, 2016 at 07:35:26PM +0000, 468ezc+5r0fnwy87qeag via qubes-users wrote:
>> Hi,
>
>> My MicroSD while attached is assigned to dom0 and not sys-usb as is supposed. Notwithstanding, USB devices are still assigned to sys-usb.
>
>> Is this the intended behavior? Doesn't this increases, in the same manner as usb devices does, the surface attack in dom0?
>
> Your (micro)SD card reader is probably not a USB device, but PCI device.
> Yes, it's better to assign it to some VM - sys-usb is ok. You can do
> this in VM settings - "Devices" tab.

Seems to me that assigning the SD controller to a different VM than
sys-usb would eliminate some attack vectors, since if they're assigned
to the same VM, IOMMU won't prevent software accessing the SD card from
attacking software accessing the USB devices (and vice versa). A
doomsday scenario that comes to mind is when the USB controller is being
used to connect to the Internet via a phone tether, and the SD card is
storing some high-value data. (My doomsday imagination is limited;
perhaps there are better doomsday scenarios.)

Is my intuition on this corect?

Of course, using a separate VM means increased RAM usage, which may or
may not be worth it.

Cheers,
-Jeremy Rand

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Marek Marczykowski-Górecki

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Aug 3, 2016, 3:21:31 AM8/3/16
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Generally yes, but I think it's rather little value. If you have
higi-value data, you should encrypt it anyway. Outside of device-facing
VM of course. Generally the VM where you (or someone else) can plug
potentially malicious device, should not be trusted.

> Of course, using a separate VM means increased RAM usage, which may or
> may not be worth it.
>
> Cheers,
> -Jeremy Rand
>



- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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