Re: automatic mounting of an encrypted harddrive

[Tobias Schula <tobias@schula.org>]

Am Sonntag 08 November 2009 14:34:45 schrieb Florian Kulzer:
> On Sun, Nov 08, 2009 at 13:01:36 +0100, Tobias Schula wrote:
> > Am Samstag 07 November 2009 17:20:44 schrieb Florian Kulzer:
> 
> [...]
> 
> > > Blkid cannot identify the filesystem on sdc1. It should work like this
> > > (my encrypted USB stick is /dev/sda1):
> > >
> > >   $ /sbin/blkid -p /dev/sda1
> > >   /dev/sda1: UUID="60160a54-2d59-46f7-b46f-3490a767e820" VERSION="256"
> > >  TYPE="crypto_LUKS" USAGE="crypto"
> >
> > Ah, I see, this is the output on my computer:
> > 	# /sbin/blkid -p /dev/sdc1
> > 	/dev/sdc1: ambivalent result (probably more filesystems on the device)
> 
> [ snip: util-linux, libblkid1 and libuuid1 are all up-to-date ]
> 
> > > Also, are you sure that you have a standard crypto_LUKS partition? How
> > > did you set it up?
[…]
> >
> > After these steps I was able to plug it in and the KDE device notifier
> > showed me the new drive. But I didn't set it up in Debian but in Kubuntu
> > if that's important.
> 
> I cannot find anything wrong with your procedure. I think the fact that
> you used Kubunutu should not matter.
> 
> Please show me the partition table of the disk/stick and the beginning
> of the LUKS partition, i.e. the output of:
> 
>   fdisk -l /dev/sdc

	# fdisk -l /dev/sdc
	
	Disk /dev/sdc: 640.1 GB, 640135028736 bytes
	255 heads, 63 sectors/track, 77825 cylinders
	Units = cylinders of 16065 * 512 = 8225280 bytes
	Disk identifier: 0x257dbcd5

	   Device Boot      Start         End      Blocks   Id  System
	/dev/sdc1               1       77825   625129281   83  Linux


>   hd -n 80 /dev/sdc1

# hd -n 80 /dev/sdc1
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 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |n...............|
00000040  00 00 00 00 00 00 00 00  73 68 61 31 00 00 00 00  |........sha1....|
00000050
 

Here's one strange thing: I encrypted USB flash drive following the steps 
above. But this time it works! What's the difference between the two?
The following output is from my flash drive:

	# fdisk -l /dev/sdc
	
	Disk /dev/sdc: 8039 MB, 8039300608 bytes
	255 heads, 63 sectors/track, 977 cylinders
	Units = cylinders of 16065 * 512 = 8225280 bytes
	Disk identifier: 0xe8070000
	
	   Device Boot      Start         End      Blocks   Id  System
	/dev/sdc1               1         977     7847721    b  W95 FAT32


# hd -n 80 /dev/sdc1
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  63 62 63 2d 65 73 73 69  |........cbc-essi|
00000030  76 3a 73 68 61 32 35 36  00 00 00 00 00 00 00 00  |v:sha256........|
00000040  00 00 00 00 00 00 00 00  73 68 61 31 00 00 00 00  |........sha1....|
00000050

It seems that Ubuntu uses xts-plain but Sid cbc-essiv and the SHA-256 
algorithm. But it's strange that both drives are recognised by Kubuntu but 
only the flash drive by Debian.


Regards

Tobias