Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-02-09 Thread Mikulas Patocka
On Tue, 9 Feb 2010, Herbert Xu wrote: Mikulas Patocka mpato...@redhat.com wrote: You should rather add a flag CRYPTO_ALG_CHANGES_STATE to determine that a cipher can't be used to encrypt disks. No, please see my reply in the previous thread. What we should do is fix arc4. I just

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-02-09 Thread Sebastian Andrzej Siewior
* Herbert Xu | 2010-02-09 18:37:18 [+1100]: Mikulas Patocka mpato...@redhat.com wrote: You should rather add a flag CRYPTO_ALG_CHANGES_STATE to determine that a cipher can't be used to encrypt disks. No, please see my reply in the previous thread. What we should do is fix arc4. I just

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-02-09 Thread Herbert Xu
On Tue, Feb 09, 2010 at 09:02:35AM -0500, Mikulas Patocka wrote: What is the fix for arc4? Copy the internal state after a key schedule and restore it with every encryption? arc4 should be a blkcipher, not a cipher. Then it can have an IV which is where thie should be stored. I think

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-02-09 Thread Sebastian Andrzej Siewior
* Herbert Xu | 2010-02-10 07:45:19 [+1100]: Herbert, what happend to the check for streamcipher idea you had? Is it gone? On the other hand it wouldn't be probably that bad to have a Well again whether that should be done is up to the dm-crypt maintainers. Milan liked that afaik. seprate

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-02-09 Thread Herbert Xu
On Tue, Feb 09, 2010 at 10:12:38PM +0100, Sebastian Andrzej Siewior wrote: This is no different to any stream cipher. Sure. So we fix arc4 and don't play mother . Okay I will into this :) That would be awesome. Thanks! -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmVHI~}

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-02-08 Thread Herbert Xu
Mikulas Patocka mpato...@redhat.com wrote: You should rather add a flag CRYPTO_ALG_CHANGES_STATE to determine that a cipher can't be used to encrypt disks. No, please see my reply in the previous thread. What we should do is fix arc4. I just haven't got around to doing it yet. As to

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-01-26 Thread Milan Broz
On 01/26/2010 10:22 AM, Sebastian Andrzej Siewior wrote: * Milan Broz | 2010-01-25 19:39:11 [+0100]: On 01/25/2010 07:29 PM, Mikulas Patocka wrote: When using arc4 to encrypt a block device, the resulting device is unreliable. It reads garbage. That's because arc4 is a stream cipher, if you

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-01-26 Thread Mikulas Patocka
This patch disables the use of arc4 on block devices. arc4 again. it is simply not a block cipher:-) This should be solved inside cryptoAPI and not blacklist it in dm-crypt, see that thread http://article.gmane.org/gmane.linux.kernel.cryptoapi/3441 I some how remember Herbert

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-01-26 Thread Sebastian Andrzej Siewior
* Mikulas Patocka | 2010-01-26 07:27:18 [-0500]: yes, I think it is better. (...and I just forgot to add that test to dm-crypt after that suggestion.) Milan Hmm, there is salsa20 that has block size 1, larger initialization vectors, and can be used to encrypt disks (although salsa20

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-01-26 Thread Mikulas Patocka
On Tue, 26 Jan 2010, Sebastian Andrzej Siewior wrote: * Mikulas Patocka | 2010-01-26 07:27:18 [-0500]: yes, I think it is better. (...and I just forgot to add that test to dm-crypt after that suggestion.) Milan Hmm, there is salsa20 that has block size 1, larger initialization

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-01-25 Thread Milan Broz
On 01/25/2010 07:29 PM, Mikulas Patocka wrote: Hi When using arc4 to encrypt a block device, the resulting device is unreliable. It reads garbage. That's because arc4 is a stream cipher, if you write something, it advances its state and if you attempt to decrypt the same sector, it uses

Re: [PATCH] dm-crypt: disable block encryption with arc4

2010-01-25 Thread Mikulas Patocka
BTW. I created a script that tests all possible ciphers, keysizes, chaining modes and iv modes for dm-crypt. arc4 is the only one that fails. You can add it your regression testsuite if you want. Mikulas#!/bin/sh dmsetup remove cr0 set -e cipher=$@ cryptsetup -d key $cipher create cr0 /dev/ram0