Pre-boot authentication / geli-aware bootcode

[Simon L. B. Nielsen]

On Fri, Jun 15, 2012 at 7:11 PM, Matt Piechota <piechota at argolis.org> wrote:
> On 06/15/2012 01:40 PM, Simon L. B. Nielsen wrote:
>>
>> On Jun 11, 2012 1:22 AM, "Robert Simmons"<rsimmons0 at gmail.com>  wrote:
>>>
>>> Would it be possible to make FreeBSD's bootcode aware of geli encrypted
>>
>> volumes?
>>>
>>> I would like to enter the password and begin decryption so that the
>>> kernel and /boot are inside the encrypted volume.  Ideally the only
>>> unencrypted area of the disk would be the gpt protected mbr and the
>>> bootcode.
>>>
>>> I know that Truecrypt is able to do something like this with its
>>> truecrypt boot loader, is something like this possible with FreeBSD
>>> without using Truecrypt?
>>
>> I just booted off a USB flash key. Then your entire drive can be
>> encrypted.
>>
>
> While true, the point (to me at least) is that with your kernel (and in
> Linux's case, initrd) in the clear it's possible for someone to bury a
> trojan of some sort in there waiting for you to boot up and start doing
> something nefarious (open backdoors, keylogging, etc.). I suppose you could
> check hashes of the kernel stuff and whatnot on booting to see if they
> haven't been modified, but that's not fool-proof either. That's obviously
> some pretty cloak and dagger stuff, but the company I work for requires full
> disk encryption. I've never actually asked if /boot counts, somewhat fearing
> the answer and resulting hassle from the largely paper-pushing security
> types.

If you are worried about somebody compromising the system with direct
access, you can't fix that if you are booting of it. Truecrypt does
not prevent somebody compromising the truecrypt loader from gaining
access to your system after you have supplied the compromised loader
with your password.

10 seconds of google searching:
http://theinvisiblethings.blogspot.ie/2009/10/evil-maid-goes-after-truecrypt.html

> The USB key method isn't bad, but it realistically only adds obfuscation
> unless you keep your laptop and the key separate. Knowing myself, I'd forget
> one or the other fairly often. :)

I got a USB key which was ~1.2x2cm (from memory) so I just kept it in
my keychain, and it was only attached to a computer when the system
was booting (well, mostly) and when I had to upgrade kernel so I would
say it added more than obfuscation, but nothing is perfect. As I could
not get in at home without said keychain forgetting it wasn't really
much of a problem (or rather, more of a problem wrt. getting in than
wrt. booting laptop :-) ).

It also provide a second factor'ish authentcation for the laptop as I
used GELI keyfiles on the USB key as part of the encryption key.

Not saying it's perfect, but worked well for me (past tense as I don't
use a FreeBSD laptop anymore).

Frankly I think there is a much simpler solution to this problem... if
you ever not loose access long enough to the laptop that somebody
could have done something funny, wipe drive and reinstall. It all
depends on your level of paranoia / requirements for security.

PS. just because you are paranoid, doesn't mean they are not out to get you :-).

-- 
Simon