INT 13, real mode, block write commands and coreboot

Dear Vincent,
dear guys

thanks very much for your reply.
> I don't own a raspi, just another SBC like it.

I think that the embedded solution is the best. 
However, Raspberry hasn't SATA ports, only USBs. 
Please, can you suggest me a SBC like Raspy that also allows SATA connections (eSATA) ? Important is that the SBC support UBUNTU / UBUNTU-like O.S.
> There is no PC BIOS on it, there is firmware for booting, but (I may be wrong) it is not active after boot.

In fact, this is the important thing; I need of a system whose firmware for booting is not active after boot.
> The automounting of partitions is a property of the operating system, so you should make sure to disable it if you don't want your usb keys to be automounted

Ok, I'm agree with you. I have no problem to block the automounting for UBUNTU / UBUNTU-like O.S. In fact my aim is to use:

dd if=/dev/sdX of=$HOME/usbkeyimage.raw bs=1M

to make an image of the suspect drive.

I hope to hear you soon.

Thanks in advance.

Best Regards.

Vincenzo.

Forensic Consultant
Tribunale di Lecce

Studio: Strada di Garibaldi - Contrada Paradisi
73010 Lequile (LE)

cell: 339.7968555
skype: vincenzo.di_salvo

----Messaggio originale----
Da: [e-mail]
Data: 5-set-2017 9.57
A: "[e-mail]", "Coreboot"
Ogg: Re: [coreboot] INT 13, real mode, block write commands and coreboot

Hello,

Please keep the discussion on-list, for the sake of others searching for
the same infos.

On Tue, Sep 5, 2017 at 7:43 AM, [e-mail]
> > Plug it in, dump it without mounting any eventual partitions, and you're
>
> done.
> You can derive from threre for other interfaces like SATA...
>
> Please, about Raspberry, are you sure that plugging a usb drive into it, any
> partitions will not be mounting ? Maybe you have the Raspberry and you have
> noticed this behavior ?

I don't own a raspi, just another SBC like it. There is no PC BIOS on
it, there is
firmware for booting, but (I may be wrong) it is not active after boot.

The automounting of partitions is a property of the operating system, so you
should make sure to disable it if you don't want your usb keys to be
automounted,

Just search in the docs of your linux distribution of choice for a way
to do that,
should be fairly straightforward.
(subjects to search: automount, udev, systemd, sysv-init, etc...)
> I'll check to understand better the raspberry chain: BIOS->PAYLOAD->KERNEL
> contacting the Raspberry technical support.

I don't think you'll met a lot of ARM SBCs with coreboot, they are mostly using
the u-boot bootloader.

But the important thing for you is that the firmware is not used after
boot and that
the OS don't touch the HW. So, as long as the USB key is only plugged
after boot,
the firmware won't have the chance to touch it.

After that a simple:

dd if=/dev/sdX of=$HOME/usbkeyimage.raw bs=1M

and you should have a copy of it to search what you're after.

If you're paranoid, make three distinct copies, sha256sum the key, etc...

You should learn how to use those tools.

But beware this is only scratching the surface, if you're after someone who
knows his thing, you'll have to eventually go deeper, as some disk firmwares
have already been modified to hide some data even from the OS.

[Vincent Legoll]

Hello,

On Thu, Sep 7, 2017 at 8:02 PM, [e-mail]
 wrote:
> However, Raspberry hasn't SATA ports, only USBs.

You can use usb/sata dongle or enclosure if you won't mind the slight
(if usb3 + uasp) performance hit. USB2 won't be practical, due to very
limited bandwidth.

The dd command will work on USB/sata too.
> Please, can you suggest me a SBC like Raspy that also allows SATA
> connections (eSATA) ?

I don't remember if I saw any that has real SATA, (i.e. not an on-board
usb/sata). There ought to be some...

Be careful to choose one that also has native Gbps ethernet, and not
on-board usb/eth chip.

The on-boar usb/something designs are often multiplexed on a single
usb port, so that the bandwith is shared between all devices, that will
kill your performance.

There is a lot of information about those topics on the Armbian site &
forum, see [1]
> Important is that the SBC support UBUNTU / UBUNTU-like
> O.S.

There is an ubuntu flavored armbian, have a look there:

[1] https://www.armbian.com/