freebsd security - Dec 2005 - geli or gbde encryption of slices

Hello,

I was playing around with geli an gbde after last EuroBSDCon. 
I liked the idea of encrypting my data which resides in /home/$user.
Since this is a "single" user laptop i intended to encrypt the
whole /home partition. Well no problems with that. But i wanted
the lockfile or keyfile on a seperate usb disc. Which would be
mounted or used during boot of the system. I also used gshsec on
the usb disc to even make things more difficult. 

Well here is what i found. You can't use a none mounted disc for 
the keys, to take things further geli asks for the access passphrease
before any filesystems except / is mounted. Gbde fails also because
the system can't do interactivaly query for the passphrase. 

I wanted to use a 3 way authentication for the slice, encrypted fs, 
a usb key and passphrase. I can use geli without the usb key (keyfile).
But that would render a possible bruteforce entry. 

Is there a way to have something similar like this working? I even
thought of using something like vendor, product and serial ids for
the "keyfile" which could be used with any usbdevice on the usb bus.

Have any of you thought about these things and have a way to do 
this sort of thing (keyfile on usbdrive).

Robert
 
-- 
Microsoft: Where do you want to go today?
Linux: Where do you want to go tomorrow?
FreeBSD: Are you guys coming or what?
OpenBSD: Hey guys you left some holes out there!

On Sun, Dec 11, 2005 at 01:33:46PM +0100, Robert Blacquiere wrote:
+> Hello,
+> 
+> I was playing around with geli an gbde after last EuroBSDCon. 
+> I liked the idea of encrypting my data which resides in /home/$user.
+> Since this is a "single" user laptop i intended to encrypt the
+> whole /home partition. Well no problems with that. But i wanted
+> the lockfile or keyfile on a seperate usb disc. Which would be
+> mounted or used during boot of the system. I also used gshsec on
+> the usb disc to even make things more difficult. 
+> 
+> Well here is what i found. You can't use a none mounted disc for 
+> the keys, to take things further geli asks for the access passphrease
+> before any filesystems except / is mounted. Gbde fails also because
+> the system can't do interactivaly query for the passphrase. 

Unfortunately we needed to make a choice here: allow to encrypt /usr/,
etc. or allow for getting keys from more sources.

You can still do what you want, but not via rc.d/geli directly.

Geli(8) itself allows to use key from the raw device or anything else,
rc.d/geli is the thing which is not such flexible.
You may want to try adding some code to /etc/rc.local (which will take
part of the key from passphrase, part from USB Pen Drive and part for
gshsec(8) device):

	(cat /mnt/pendrive/keyfile.bin && dd if=/dev/shsec/key bs=64k count=1)
| /sbin/geli attach -k /dev/stdin /dev/ad0s1e
	fsck_ffs -p /dev/ad0s1e.eli
	mount /dev/ad0s1e.eli /mnt/secure

Assuming that /mnt/pendrive is already mounted (it should be if placed
in /etc/fstab).

+> I wanted to use a 3 way authentication for the slice, encrypted fs, 
+> a usb key and passphrase. I can use geli without the usb key (keyfile).
+> But that would render a possible bruteforce entry. 

Even when you use passphrase only, geli(8) provides PKCS#5v2 to
strength it.
I'm using it with 131072 iterations, so it is 2^17 times harder to
brute-force my passphrase and takes about 2-3 seconds to attach
encrypted device on my laptop.

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 187 bytes
Desc: not available
Url :
http://lists.freebsd.org/pipermail/freebsd-security/attachments/20051216/66ca542d/attachment.bin