Re: [dm-crypt] encrypted root: prevent / detect tampering with kernel / initrd

[Olivier Sessink <oliviersessink@gmail.com>]

Heinz Diehl wrote:
> On 28.12.2009, Olivier Sessink wrote: 
> 
>> yes you are 100% right from a perfect security viewpoint. However,
>> we're looking at a "regular user" deployment, and we know that our
>> regular users are not going to look after their devices as good as
>> most IT security professionals will do (they might even carry their
>> password in their wallet, or tell the password over the phone). So
>> our aim is not 100% perfect security, but just "make it (a lot)
>> harder" to get to the data.
> 
> Anybody who has the skills and the motivation to modify your kernel/initrd
> is far from being your "regular user", and is most likely able and has the
> expertise to do other things to your machine as well.

I'm not so sure about that. Most script kiddies can modify an initrd 
(just google for 'dm-crypt evil maid' and you'll find at least one 
script-kiddie level recipe). But I don't think there are many script 
kiddies that can do a TEMPEST attack or install a physical keylogger in 
a laptop.

> "Please repeat with me: there is no way to avoid or detect backdoors if
> physical access to the machine has ever been granted." (Werner Koch on
> gnupg-users 19.02.2009 on exactly the same topic).

add to that: "encryption is not perfect if your house is not TEMPEST 
proof or burglar proof, or if you can be blackmailed, or if you have 
children that can be kidnapped, or if they simply drug you, etc. etc."

If somebody is really determined to get to your data they will succeed, 
skilled or not skilled. I suppose everybody on this list knows this one: 
http://imgs.xkcd.com/comics/security.png

Olivier