• Eric Biggers's avatar
    crypto: ofb - fix handling partial blocks and make thread-safe · b3e3e2db
    Eric Biggers authored
    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: e497c518 ("crypto: ofb - add output feedback mode")
    Cc: <stable@vger.kernel.org> # v4.20+
    Cc: Gilad Ben-Yossef <gilad@benyossef.com>
    Signed-off-by: 's avatarEric Biggers <ebiggers@google.com>
    Reviewed-by: 's avatarGilad Ben-Yossef <gilad@benyossef.com>
    Signed-off-by: 's avatarHerbert Xu <herbert@gondor.apana.org.au>
    b3e3e2db
testmgr.h 1.24 MB
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