Re: [gentoo-user] Re: Kernel upgrade and now LUKS failure

[Stefan G. Weichinger]

Am 18.05.2010 23:16, schrieb Jan Engelhardt:
> yOn Tuesday 2010-05-18 22:17, Stefan G. Weichinger wrote:
>>
>> I saved my history, unfortunately only the last steps were kept,
>> but I am able to reconstruct:
>>
>> The block-device is /dev/VG01/sgwcrypt ...
>>
>> #I tried a more complicated KEY KEY=`head -c 79 /dev/urandom`
>
> Well, I'm not going to blame you yet, but the shell is pretty
> binary-unsafe -- and you have just invoked that voodoo again.
>
> # head -c79 /dev/urandom >t-crypt.ukey; \ hexdump -C <t-crypt.ukey;
> \ KEY=$(cat t-crypt.ukey); \ echo -n "$KEY" | hexdump -C; \ echo -n
> "$KEY" | wc; 00000000  a4 b2 c8 a0 4f c9 00 37  66 f3 0c 20 2d 5c 05
> e7  |....O..7f.. -\..| 00000010  cd 5e 5d 00 5d e1 18 2a  1a 8b 2d 41
> 22 e7 66 0e  |.^].]..*..-A".f.| 00000020  b0 a3 1d 41 1e 23 1d 00  f8
> b2 b2 bc 34 28 94 fe  |...A.#......4(..| 00000030  ba 0f 45 11 b5 c6
> d8 a1  ca c2 ec 08 5e 48 d4 7f  |..E.........^H..| 00000040  17 a8 75
> af ef ef f1 7a  0f 2f bf 64 c2 3a 9c     |..u....z./.d.:.| 0000004f
>
> 00000000  a4 b2 c8 a0 4f c9 37 66  f3 0c 20 2d 5c 05 e7 cd
> |....O.7f.. -\...| 00000010  5e 5d 5d e1 18 2a 1a 8b  2d 41 22 e7 66
> 0e b0 a3  |^]]..*..-A".f...| 00000020  1d 41 1e 23 1d f8 b2 b2  bc 34
> 28 94 fe ba 0f 45  |.A.#.....4(....E| 00000030  11 b5 c6 d8 a1 ca c2
> ec  08 5e 48 d4 7f 17 a8 75  |.........^H....u| 00000040  af ef ef f1
> 7a 0f 2f bf  64 c2 3a 9c              |....z./.d.:.| 0000004c 0
> 2      76
>
> So what was once 79 bytes has been reduced to 76 by means of the $()
> or backtick operator.
>
> Not a problem for the crypto utilities per se, but I wanted to point
> out that you are effectively only having a 76-long key here. The
> chance to get a key shorter than the requested 79 is 27%.
>
>> # avoid newline here echo -n $KEY | openssl aes-256-cbc >
>> /etc/security/super.key
>>
>> # format it, using "--keyfile=-" as mentioned in bugs ... openssl
>> aes-256-cbc -d -in /etc/security/super.key | cryptsetup -v
>> --key-file=- --cipher aes-cbc-plain --key-size 256 luksFormat
>> /dev/VG01/sgwcrypt
>>
>> # open it openssl aes-256-cbc -d -in /etc/security/super.key |
>> cryptsetup -v --key-file=-  luksOpen /dev/VG01/sgwcrypt newhome
>
> Turns out cryptsetup has yet another oddity. With LUKS, --key-file=-
> is moot. Instead....
>
> [fkey is the unencrypted one]
>
> # cryptsetup luksFormat /dev/loop94 t-crypt.fkey && \ cryptsetup
> --key-file=- luksOpen /dev/loop94 x94 <t-crypt.fkey Key slot 0
> unlocked.
>
>
> And you thought that doc/bugs.txt described all cryptsetup CLI
> oddities.
>
> *facepalm*
>
> ANYWAY.
>
>
> If I proceed with this luks container now, all succeeds:
>
> # mkfs.ext4 /dev/mapper/x94 mke2fs 1.41.9 (22-Aug-2009) ... #
> cryptsetup remove x94
>
> First, let's see if raw passthrough works:
>
> # ./mount.crypt -vo keyfile=t-crypt.fkey,fsk_cipher=none /dev/loop94
> /mnt command: 'readlink' '-fn' '/dev/loop94' command: 'readlink'
> '-fn' '/mnt' mount.crypt(crypto-dmc.c:144): Using _dev_loop94 as
> dmdevice name command: 'mount' '-n' '/dev/mapper/_dev_loop94' '/mnt'
>  # df /mnt Filesystem           1K-blocks      Used Available Use%
> Mounted on /dev/loop94              62465      5365     53875  10%
> /mnt # PMT_DEBUG_UMOUNT=1 ./umount.crypt /mnt
>
>
> Now the openssl-encrypted file:
>
> # ./mount.crypt -vo
> keyfile=t-crypt.key,fsk_cipher=aes-256-cbc,fsk_hash=md5 /dev/loop94
> /mnt command: 'readlink' '-fn' '/dev/loop94' command: 'readlink'
> '-fn' '/mnt' Password: mount.crypt(crypto-dmc.c:144): Using
> _dev_loop94 as dmdevice name command: 'mount' '-n'
> '/dev/mapper/_dev_loop94' '/mnt' # df /mnt Filesystem
> 1K-blocks      Used Available Use% Mounted on /dev/loop94
> 62465      5365     53875  10% /mnt
>
>
> Match?

Frankly: dunno ;-)
Yes, I am able to follow and understand in general so far ... but ...

Assuming that "I am too stupid": Where is the how-to-do-it?

So far the only thing I really understood "You are doing it wrong".

But where is the "Do it this way and you are safe" ?

I wouldn't post here if I were competent enough to know all these details.

Concerning encryption I am at the USER-level, you know for sure ;-)

Just trying to feed back my problems to maybe detect bugs or my mistakes.

Stefan