Messages in this thread | | | Date | Sun, 10 Aug 2003 23:03:06 +0200 | Subject | Re: [PATCH] loop: fixing cryptoloop troubles. | From | Fruhwirth Clemens <> |
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On Sun, Aug 10, 2003 at 04:27:47PM +0200, Christophe Saout wrote: > Am So, 2003-08-10 um 16.10 schrieb Pascal Brisset: > > > > In loop_transfer_bio the initial vector has been computed only once. For any > > > situation where more than one bio_vec is present the initial vector will be > > > wrong. Here is the trivial but important fix. > > > > Looks good, but: > > - I doubt this could explain the alteration pattern (1 byte every 512). > > - Corruption also occured with cipher_null (which ignores the IV).
I could not find a way to explain that strange pattern either. With CBC it would have to result in total mess if just one bit is flipped. Probably read/writing is handled with different sized bio_vec.. no idea.
cipher_null does not ignore the IV. The CBC processing takes place no matter what mapping function (aka electronic codebook) is used. The fact that cipher_null is an identity mapping does not stop CBC.
> I personally think that the only way to get things right is to do > encryption sector by sector (not bvec by bvec) since every sector can > have its own iv.
That's done anyway. Per convention the transformation module is allowed to increase the IV every 512 bytes. The IV parameter is only the initial initial vector ;).
> I've implemented a crypto target for device-mapper that does this and it > doesn't seem to suffer from these corruption problems: > http://marc.theaimsgroup.com/?l=linux-kernel&m=105967481007242&w=2 and a > slightly updated patch: http://www.saout.de/misc/dm-crypt.diff
Nice! It's definitely a feature worth merging. loop.c used to be the place where to put this stuff, but why not replace it by newer in-kernel techniques?
> Should I repost the patch (inline this time) with an additional [PATCH] > or am I being annoying? Joe Thornber (the dm maintainer) would like to > see this patch merged.
If you can't get attention for your patch, try to convince someone "more important". DM maintainer is a good place to start :)
Regards, Clemens [unhandled content-type:application/pgp-signature] | |