Re: [PATCH 03/16] crypto: ofb - fix handling partial blocks and make thread-safe

On Fri, Jan 4, 2019 at 6:20 AM Eric Biggers [off-list ref] wrote:

From: Eric Biggers <redacted>

Fix multiple bugs in the OFB implementation:

1. It stored the per-request state 'cnt' in the tfm context, which can be
   used by multiple threads concurrently (e.g. via AF_ALG).
2. It didn't support messages not a multiple of the block cipher size,
   despite being a stream cipher.
3. It didn't set cra_blocksize to 1 to indicate it is a stream cipher.

To fix these, set the 'chunksize' property to the cipher block size to
guarantee that when walking through the scatterlist, a partial block can
only occur at the end.  Then change the implementation to XOR a block at
a time at first, then XOR the partial block at the end if needed.  This
is the same way CTR and CFB are implemented.  As a bonus, this also
improves performance in most cases over the current approach.

Well, it certainly looks like my implementation had a lot of room for
improvement :-)
Thank you for doing this, Eric

Reviewed-by: Gilad Ben-Yossef <gilad@benyossef.com>

Gilad

-- 
Gilad Ben-Yossef
Chief Coffee Drinker

values of β will give rise to dom!