Re: Strange header corruption

[Dis McCarthy <dmcrypt@xxxxxxxxxxx>]

On Wed, Feb 26, 2014 at 7:49 AM, Arno Wagner <arno@xxxxxxxxxxx> wrote:

On Wed, Feb 26, 2014 at 13:13:30 CET, Dis McCarthy wrote:
> Thanks for the help!
>
> Unfortunately I don't have 7T to back up the devices. Is there a relatively
> safe way to test? Worst case, I can make the change, set the entire device
> ro and try, if dm-crypt can decrypt a readonly device.

There is: Copy the first 100MB or so (needed are something like 2MiB, but
better be on the safe side) and work on that via loopback file
(see FAQ Item 2.5). When you can unlock that, you have then a good
header that you can backup the header from the loopback device and
install on the disk via luksHeaderBackup/luksHeaderRestore. Keep a
copy of those first 100MB as backup on a separate device so you can
restore it and can go back to the original state if anything goes
wrong. This does protect your (at the moment broken, but nonetheless
vital) headers from errors. Unlike a full backup, it does not protect
your filesystem in the LUKS container(s), so be careful.

If you are unsure, test disk operations first on a separate disk
and see what they do to make sure you have it under control.

You need to do that for each disk separately. If you cannot get an
unlock, you can run the keyslot-checker on the loopback device
as well and do further analysis there. All that LUKS needs is in
the first 2MiB, see alos FAQ Item 6.12.

Those changes did result in a viewable/dumpable header, but it still won't unlock.

Keyslot checker on both images returns:

parameters (commandline and LUKS header):

  sector size: 512

  threshold:   0.900000

- processing keyslot 0:  start: 0x001000   end: 0x03f800 

- processing keyslot 1:  keyslot not in use

- processing keyslot 2:  keyslot not in use

- processing keyslot 3:  keyslot not in use

- processing keyslot 4:  keyslot not in use

- processing keyslot 5:  keyslot not in use

- processing keyslot 6:  keyslot not in use

- processing keyslot 7:  keyslot not in use

 

> I did confirm farther down the header, the keys and empty slots appear to
> be present.

"Present" is not enough. "Undamaged" is what you need. But
lets fix the missing bytes first and see where that gets
you.

Definitely. Appearances can be deceiving. (And in this case, it looks like they are.)

The complete/corrected headers are attached.

Thanks so much for helping!

 

Arno

> On Feb 25, 2014 11:11 PM, "Arno Wagner" <arno@xxxxxxxxxxx> wrote:
> >
> > This is pretty strange. You seem to have lost parts of the
> > header, but not the hash spec. And it seems to have happened
> > two times.
> >
> > This should not be happening at all. LUKS does not require a
> > "clean shutdown", unless you luksFormat or change
> > passphrases, cryptsetup does not write anything at all for
> > LUKS and even ripping out the disk directly while it
> > runs should not cause any header damage. (It may damage the
> > filesystem in the LUKS container though...).
> >
> > What seems to have happened here is that some application
> > read the header, replaced the first 0x2d bytes (leaving
> > "ain64" of "xts-plain64". It seem to have put in a GUID
> > of sorts. I have no idea what this is. The header was not
> > simply overwritten, so this is something deliberately.
> > On the other hand, no application should write anything to
> > the start of a partition in normal operation.
> >
> > Maybe somebody else here recognizes the pattern seen?
> > Maybe these are SSDs with a serious firmware bug?
> > Or maybe you have wrap-around because the USB3 interface
> > cannot handle the full disk size?
> >
> >
> > As to recovery:
> > 1. Make a sector-wise backup of the whole LUKS containers
> >    or whole disk(s) before messing with anything!
> > 2. Just putting in what should be there in the first
> >    0x2d bytes with a hex editor may be enough to get this
> >    working again if there is no other damage. If there
> >    is damage in the keyslot areas or to the salt values
> >    in the header, no recovery is possible.
> >
> > Hexediting the header is pretty simple, just read the
> > first 1024 bytes (head -c 1024 /dev/disk > hdr.img),
> > hexedit it and then write it back (cat hdr.img > /dev/disk).
> > The risk of doing more damage is high, so do not try this
> > without that backup.
> >
> > Here is what the first 0x2d bytes should look like (defaul
> > parameters):
> >
> > 00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00
> |LUKS....aes.....|
> > 00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
> |................|
> > 00000020  00 00 00 00 00 00 00 00  78 74 73 2d 70 6c 61 69
> |........xts-plai|
> >
> > If after that cryptsetup works, but does not accept
> > your passphrase, you can run the keyslot-checker from
> > the source package and you can post the full headers
> > (592 bytes long) here for more advice.
> >
> > Arno
> >
> >
> >
> >
> >
> > On Tue, Feb 25, 2014 at 15:33:20 CET, Dis McCarthy wrote:
> > > I've got 2 full-device luks devices (usb3) that somehow got corrupted
> > > headers at the same time. They were working, I powered down the system
> to
> > > move some plugs and when I brought it back up, my headers are
> unrecognized.
> > > (See below.) The system is a mac mini running arch linux. It has been
> > > rebooted and powercycled repeatedly since being built and never had an
> > > issue, so I hesitate to blame refit. The only thing I can see is that
> there
> > > was a recent update of cryptsetup (to 1.6.3-2). I'm not sure if the
> devices
> > > were stopped cleanly before reboot (probably not, since its arch..) but
> the
> > > volumes were unmounted and I wouldn't expect to get corruption.
> > >
> > > I'm dumb, and do not have a backup of the headers. (Well.. there might
> be a
> > > backup of one of them. Inside the encrypted volume.. yeah, like I said,
> I'm
> > > dumb. If I get this back, that is getting remedied immediately..)
> > >
> > > Comparing with other users, it looks like some of the entries are
> swapped
> > > around. I started doing a comparison to the on-disk format pdf, but I
> > > haven't had a chance to print it out and get intimate with it yet
> (beyond
> > > noting that LUKS 0xba0xbe is missing of course.)
> > >
> > > Is there any hope? Here is what I've got at the beginning the drives:
> > >
> > > 00000000  00 00 00 00 48 00 00 00  00 00 00 00 32 32 30 64
> > >  |....H.......220d|
> > > 00000010  32 30 33 64 2d 39 62 62  34 2d 34 35 00 00 00 00
> > >  |203d-9bb4-45....|
> > > 00000020  24 00 00 00 12 00 00 00  24 00 00 00 00 00 61 69
> > >  |$.......$.....ai|
> > > 00000030  6e 36 34 00 00 00 00 00  00 00 00 00 00 00 00 00
> > >  |n64.............|
> > > 00000040  00 00 00 00 00 00 00 00  73 68 61 32 35 36 00 00
> > >  |........sha256..|
> > > 00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
> > >  |................|
> > > 00000060  00 00 00 00 00 00 00 00  00 00 10 00 00 00 00 40
> > >  |...............@|
> > > 00000070  da 22 00 00 00 00 24 01  00 00 00 00 00 00 00 00
> > >  |."....$.........|
> > >
> > > and:
> > > 00000000  00 00 00 00 48 00 00 00  00 00 00 00 32 33 63 38
> > >  |....H.......23c8|
> > > 00000010  62 61 33 31 2d 37 61 63  66 2d 34 32 00 00 00 00
> > >  |ba31-7acf-42....|
> > > 00000020  24 00 00 00 12 00 00 00  24 00 00 00 00 00 61 69
> > >  |$.......$.....ai|
> > > 00000030  6e 36 34 00 00 00 00 00  00 00 00 00 00 00 00 00
> > >  |n64.............|
> > > 00000040  00 00 00 00 00 00 00 00  73 68 61 32 35 36 00 00
> > >  |........sha256..|
> > > 00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
> > >  |................|
> > > 00000060  00 00 00 00 00 00 00 00  00 00 10 00 00 00 00 40
> > >  |...............@|
> > > 00000070  de 8b 00 00 00 00 24 01  00 00 00 00 00 00 00 00
> > >  |......$.........|
> > >
> > > Thanks!
> >
> > > _______________________________________________
> > > dm-crypt mailing list
> > > dm-crypt@xxxxxxxx
> > > http://www.saout.de/mailman/listinfo/dm-crypt
> >
> >
> > --
> > Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno@xxxxxxxxxxx
> > GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D
> 9718
> > ----
> > A good decision is based on knowledge and not on numbers. -  Plato
> > _______________________________________________
> > dm-crypt mailing list
> > dm-crypt@xxxxxxxx
> > http://www.saout.de/mailman/listinfo/dm-crypt

> _______________________________________________
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> http://www.saout.de/mailman/listinfo/dm-crypt


--
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno@xxxxxxxxxxx
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
A good decision is based on knowledge and not on numbers. -  Plato
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00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  78 74 73 2d 70 6c 61 69  |........xts-plai|
00000030  6e 36 34 00 00 00 00 00  00 00 00 00 00 00 00 00  |n64.............|
00000040  00 00 00 00 00 00 00 00  73 68 61 32 35 36 00 00  |........sha256..|
00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000060  00 00 00 00 00 00 00 00  00 00 10 00 00 00 00 40  |...............@|
00000070  de 8b 00 00 00 00 24 01  00 00 00 00 00 00 00 00  |......$.........|
00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000090  00 00 00 01 00 00 12 01  c3 00 80 00 2f 21 68 a8  |............/!h.|
000000a0  39 c4 f1 5d 00 01 3e d9  32 33 63 38 62 61 33 31  |9..]..>.23c8ba31|
000000b0  2d 37 61 63 66 2d 34 32  65 31 2d 61 63 31 66 2d  |-7acf-42e1-ac1f-|
000000c0  64 30 65 31 38 66 34 32  39 38 32 65 00 00 00 00  |d0e18f42982e....|
000000d0  00 ac 71 f3 00 05 02 0d  cc 13 e4 7d 28 92 49 f1  |..q........}(.I.|
000000e0  ac 89 7a a3 75 32 4d db  27 18 2d e1 93 9e 97 82  |..z.u2M.'.-.....|
000000f0  90 a6 e0 e7 7a 28 8c 0f  00 00 00 08 00 00 0f a0  |....z(..........|
00000100  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000120  00 00 00 00 00 00 00 00  00 00 02 00 00 00 0f a0  |................|
00000130  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000140  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000150  00 00 00 00 00 00 00 00  00 00 03 f8 00 00 0f a0  |................|
00000160  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000170  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000180  00 00 00 00 00 00 00 00  00 00 05 f0 00 00 0f a0  |................|
00000190  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001b0  00 00 00 00 00 00 00 00  00 00 07 e8 00 00 0f a0  |................|
000001c0  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  00 00 09 e0 00 00 0f a0  |................|
000001f0  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000200  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000210  00 00 00 00 00 00 00 00  00 00 0b d8 00 00 0f a0  |................|
00000220  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000230  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000240  00 00 00 00 00 00 00 00  00 00 0d d0 00 00 0f a0  |................|
00000250  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000260

00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000020  00 00 00 00 00 00 00 00  78 74 73 2d 70 6c 61 69  |........xts-plai|
00000030  6e 36 34 00 00 00 00 00  00 00 00 00 00 00 00 00  |n64.............|
00000040  00 00 00 00 00 00 00 00  73 68 61 32 35 36 00 00  |........sha256..|
00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000060  00 00 00 00 00 00 00 00  00 00 10 00 00 00 00 40  |...............@|
00000070  da 22 00 00 00 00 24 01  00 00 00 00 00 00 00 00  |."....$.........|
00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000090  00 00 00 01 00 00 12 01  c3 00 80 00 79 a3 4c be  |............y.L.|
000000a0  4e 8c bc 93 00 01 47 a3  32 32 30 64 33 30 33 64  |N.....G.220d303d|
000000b0  2d 39 62 62 34 2d 34 35  31 36 2d 38 38 39 65 2d  |-9bb4-4516-889e-|
000000c0  63 39 34 32 39 63 31 33  38 37 36 66 00 00 00 00  |c9429c13876f....|
000000d0  00 ac 71 f3 00 05 41 e4  0a d5 d5 92 47 f4 61 eb  |..q...A.....G.a.|
000000e0  38 e0 05 57 87 34 9b e0  52 30 c9 16 21 a8 39 19  |8..W.4..R0..!.9.|
000000f0  8b cc 09 20 a1 d0 a0 c4  00 00 00 08 00 00 0f a0  |... ............|
00000100  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000120  00 00 00 00 00 00 00 00  00 00 02 00 00 00 0f a0  |................|
00000130  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000140  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000150  00 00 00 00 00 00 00 00  00 00 03 f8 00 00 0f a0  |................|
00000160  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000170  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000180  00 00 00 00 00 00 00 00  00 00 05 f0 00 00 0f a0  |................|
00000190  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001b0  00 00 00 00 00 00 00 00  00 00 07 e8 00 00 0f a0  |................|
000001c0  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  00 00 09 e0 00 00 0f a0  |................|
000001f0  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000200  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000210  00 00 00 00 00 00 00 00  00 00 0b d8 00 00 0f a0  |................|
00000220  00 00 de ad 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000230  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000240  00 00 00 00 00 00 00 00  00 00 0d d0 00 00 0f a0  |................|
00000250  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000260

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