[Freedombox-discuss] Encrypted root file systems with Mandos

[James Vasile]

On Sat, 18 Feb 2012 12:06:34 +0100, Björn Påhlsson <belorn+freedom at recompile.se> wrote:
> As a developer of the Mandos projekt, I have wanted to see if Mandos
> could be used to improve a freedom box. Of course I am slightly
> biased, but I think Mandos could be really useful for those who own a
> freedom box now but are not encrypting the data on it. So with this
> mail I was hoping to both suggest the usage of Mandos for freedom box
> users, and also ask if someone could please test it, given that I
> don't own a box myself. To make Mandos work, the program has some code
> in the initrd image, and given the nature of embedded platforms this
> might be an issue. For instance, i notice that debwrt (a Debian
> version of OpenWRT) does not seem to have an initrd, so I do not know
> if that is the case for freedom box.
> 
> A quick and small description of Mandos: The intent is to raise the
> bar of data security by letting users have a completely encrypted file
> system with the only cost being the initial installation &
> configuration. Similar to when using a RFID tag to login, with Mandos
> the user does not need to type in password each time the machine needs
> to boot up. The basic idea is that so long two machines are up and
> running, they can be sending the keys to each other for when they need
> to reboot, but if they are stolen, or taken to be analyzed in a lab,
> then they are locked and behave like any other encrypted data the
> analyzer do not have the key for. The technical details are at the
> website http://www.recompile.se/mandos or you can just get it from
> Debian "testing" repository.

The need to enter a key on a headless FreedomBox on reboot has been a
sticking point on encrypting the fs.  Mandos sounds like a move in the
right direction.  As an initial matter, FreedomBoxes should stand alone
(e.g. the key should be on board), but maybe once some friends are
connected in, dispersing the key (in chunks) to some friends with good
uptime means you'll be able to retrieve the chunks and reassemble them
to allow a reboot.  This should happen free of user intervention or else
FreedomBoxes will be vulnerable to reboot DOS attacks.  Obviously this
would only be useul to a subset of FreedomBox users.

One question I have is how the booting box authenticates to the
key-serving box?  Why does key transfer happen at home but not in a lab?
Some FreedomBoxes will undoubtedly move with their owners from home to
dorm to hotel to office.  How does Mandos know it has not been captured?

Regards,
James