[dm-crypt] Passphrase stops working.

Two Spirit twospirit6905 at gmail.com
Wed Jul 18 23:34:58 CEST 2012


Hello, I just wanted to get back to you. After wasting a huge amount of
time trying to restore my data and have it  lost  for a second and third
time, I have reproduced the problem and can confirm that it does exist.

I'm still [can't believe it] am doing testing and have some theories which
I'm checking out to isolate more if the problem is LUKS or mdadm that is
causing the
corruption to LUKS. Testing with small test files does not reproduce the
problem, however in full scale mode the
problem exists and with 4TB drives, rebuild time takes quite a bit of time.
The problem is that the
first disk of a 4 disk mdadm raid drive looses its partition table (was
originally msdos partition type 0xfd linux auto-raid created in ubuntu-8.04
with mdadm metadata-0.9). This "corruption/bug/feature" is why LUKS no
longer works. The raid5 has been grown with almost every iteration of new
hard drive capacity without fail except when going from the 2TB to 4TB
upgrade. The mdadm raid5 with the LUKS decrypted (cryptsetup luksOpen)
works and does not recognize that there is any corruption, so as long as
the HA server is up and running, the sysadmin has no clue there is a
problem since "cryptsetup luksOpen" is only done rarely or on reboot. The
disks 2,3, and 4 seem OK with my limited knowledge.

I have since found out that metadata-0.9 only supports up to 2TB drives. I
suspect that the problem is when growing a live raid past the 2TB boundary
is when the corruption is seen. The raid is operating at 2TB drive capacity
 (lowest common drive size) but has 4TB drives in the mix while in the
process of growing the raid.

I am not focusing my testing right now on isolating the problem, but
converting to mdadm metadata-1.2 to see if the problem goes away. I ran
across other os imposed file system maximum limitations (which evidently
were arbitrarily imposed) so I'm upgrading to ubuntu-12.04 which removes
these. So at best I can confirm that the problem won't exist with a new mix
of mdadm/cryptsetup/gpt using parted (new sizes also past the fdisk/msdos
partition maximums too) doesn't exist, but I suspect that other people who
are just upgrading to higher capacities might run across the same problem I
ran across.

To address your first statement, I'm starting to think too it is not a LUKS
generated problem, but the problem does corrupt LUKS.


On Mon, Jul 9, 2012 at 12:10 AM, Arno Wagner <arno at wagner.name> wrote:

> First, this does not sound like a LUKS problem, but something
> else.
>
> Second, a second passphrase is basically worthless as "backup".
> As described in the FAQ, what you need is a LUKS header backup.
>
> Now, as you describe, this happened only after a while.
> This indicated there is some conection to the data on the
> partition.
>
> One possibility is that you have the data not in the LUKS
> container, but overlayed with it. This would mean a) your
> data is not encrypted and b) at some time you overwrite
> the keyslot area with data, breaking the LUKS header. A possible
> other alternative is that you placed the RAID superblock in
> the keyslot area, but that should only kill one passphrase.
>
> The only other idea I have at this time is that you got the
> partition boders wrong when going to GPT and that somehow cause
> other data to end up in the LUKS keyslot area.
>
> It cpould be something else entirely, of course.
>
> Please give all commands you use, including raid creation
> and mounting and a full partion table dump. You can also
> email me the LUKS header (see FAQ), and I can look  for
> corruption. This does not compromise your security if you
> do not use this header again or if the keyslots are not
> recoverable (or if you trust me to destroy the header after
> I look at it).
>
> Arno
>
>
>
> On Sun, Jul 08, 2012 at 09:41:19PM -0700, Two Spirit wrote:
> > I created a 4 drive RAID5 setup using mdadm and upgrading from 2TB drives
> > to the new Hitachi 7200RPM 4TB drives. I can initially open my luks
> > partition, but later can no longer access it.
> >
> > I can no longer access my LUKS partition even tho I have the right
> > passphrases. It was working and then at an unknown point in time loose
> > access to LUKS. I've used the same procedures for upgrading from 500G to
> > 1TB to 1.5TB to 2TB. After the first time this happened a week ago, I
> > thought maybe there was some corruption so I added a 2nd Key as a backup.
> > After the second time the LUKS became unaccessible, none of the keys
> worked.
> >
> > I put LUKS on it using
> >
> > cryptsetup -c aes -s 256 -y luksFormat /dev/md0
> >
> > # cryptsetup luksOpen /dev/md0 md0_crypt
> > Enter LUKS passphrase:
> > Enter LUKS passphrase:
> > Enter LUKS passphrase:
> > Command failed: No key available with this passphrase.
> >
> > The first time this happened while I was upgrading to 4TB drives, I
> thought
> > it was a fluke, and ultimately had to recover from backups. I went an
> used
> > luksAddKey to add a 2nd key as a backup. It happened again and I tried
> both
> > passphrases, and neither worked. The only thing I'm doing differently
> this
> > time around is that I've upgraded to 4TB drives which use GPT instead of
> > fdisk.
> >
> > The last time I had to even reboot the box was over 2 years ago.
> >
> > I'm using ubuntu-8.04-server with kernel 2.6.24-29 and upgraded to
> > -2.6.24-31, but that didn't fix the problem.
>
> > _______________________________________________
> > dm-crypt mailing list
> > dm-crypt at saout.de
> > http://www.saout.de/mailman/listinfo/dm-crypt
>
>
> --
> Arno Wagner,    Dr. sc. techn., Dipl. Inform.,   Email: arno at wagner.name
> GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25
> 338F
> ----
> One of the painful things about our time is that those who feel certainty
> are stupid, and those with any imagination and understanding are filled
> with doubt and indecision. -- Bertrand Russell
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