[dm-crypt] yet another header reconstruction question

Florian Dotzer florian.dotzer at web.de
Tue Feb 16 12:32:06 CET 2016


sent again as text. sorry for HTML input. hopefully it is more readable now . 

Dear Readers of the List .
 
I had a encrypted RAID 5 on my QNAP Device  in /dev/md0.
 
It worked without any problems for about 6 years . 
But space went low and desaster began.
After adding a disk , mdadm had overwritten the 
header (block device /dev/md0 ) like this :
 
6d 64 61 64 6d 3a 20 61 64 64 65 64 20 2f 64 65  mdadm: added /de
76 2f 73 64 63 33 0a 00 00 00 00 00 00 00 00 00  v/sdc3..........
00 00 00 00 00 00 00 00 63 62 63 2d 70 6c 61 69  ........cbc-plai
6e 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  n...............
00 00 00 00 00 00 00 00 73 68 61 31 00 00 00 00  ........sha1....
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00 00 00 00 00 00 00 00 00 00 08 08 00 00 00 20  ...............
bc 31 80 6d da a4 f0 5c ed 9f 24 96 fc 1b 72 6a
 
According to the documentation on-disk-format ,
magic (LUKS 0xba 0xbe )  , version and cipher name 
seem to be overwritten.
 
I'd like to know the possible versions ( 00 01 ? ) and cipher names 
(aes ?) in order to be able to reconstruct the header (fingers crossed )
 
user support from vendor QNAP tried an hour claiming 
'fs super block could not be found'
and finally redirected me to 'commercial $$$upport' . 
 
QNAP advertised my Box with 
'Disks can be AES-encrypted with 256 bit " so
I suspect its something related with aes .
 
(And no , I had no header backup, Ahhh !)
 
Any helpful reply is welcome . 
And yes , I will make backups in the future . ;-))
 
Greetings , Florian


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