Re: [dm-crypt] [ANNOUNCE] cryptsetup 1.3.0-rc1 (test release candidate)

[Rudolf Deilmann <rudolf.deilmann@gmail.com>]

On Mon, 14 Mar 2011 18:44:05 +0100
Milan Broz <mbroz@redhat.com> wrote:
> p.s. Please let me know if you tested crypto backend support
> or loop-AES compatibility mode (and report problems, if there is
> any:-)

Thanks for your work, Milan.

I've tried to open some old loop-AES partitions with this version and
kernel 2.6.38-rc8. It basically seems to work (however, it seems to be
slower than original loop-aes as your comment regarding speed suggests)

Two notes:

1) Keyfile handling

The following didn't work with one keyfile:

cryptsetup --key-file /path/keyfile -s 256 loopaesOpen <device> <name>

but this did work:

cat /path/keyfile | \\
  cryptsetup --key-file - -s 256 loopaesOpen <device> <name> 


I didn't have this problem with another keyfile.


2) Offset, skip and sizelimit support

It was common to store the gpg-keyfile in the head of an partition. See
for example http://loop-aes.sourceforge.net/aespipe.README: 

---
3.3. Example 3 - Encrypted CD-ROM
[...]
mount -t iso9660 /dev/cdrom /cdrom -o
loop=/dev/loop0,encryption=AES128,gpgkey=/dev/cdrom,offset=8192 
---

I was able to open such a partition with plain dmsetup; 'cryptsetup
loopaesOpen' didn't work because '--size','--skip' and '--offset' are
not supported. Perhaps you could add support for these switches to
loopaesOpen; the necessary changes in cryptsetup seems trivial.
( '--offset' - but not '--skip' - is already mentioned in the manpage
as a supported option for loopaesOpen )

mfg,
 Rudi