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crypto: ofb - fix handling partial blocks and make thread-safe
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. Fixes: e497c51 ("crypto: ofb - add output feedback mode") Cc: <[email protected]> # v4.20+ Cc: Gilad Ben-Yossef <[email protected]> Signed-off-by: Eric Biggers <[email protected]> Reviewed-by: Gilad Ben-Yossef <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
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