On Mon, Sep 9, 2019 at 3:20 PM Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>
> On Sun, 8 Sep 2019 at 09:04, Uri Shir <uri.shir@xxxxxxx> wrote:
> >
> > In XTS encryption/decryption the plaintext byte size
> > can be >= AES_BLOCK_SIZE. This patch enable the AES-XTS ciphertext
> > stealing implementation in ccree driver.
> >
> > Signed-off-by: Uri Shir <uri.shir@xxxxxxx>
> > ---
> > drivers/crypto/ccree/cc_cipher.c | 16 ++++++----------
> > 1 file changed, 6 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/crypto/ccree/cc_cipher.c b/drivers/crypto/ccree/cc_cipher.c
> > index 5b58226..a95d3bd 100644
> > --- a/drivers/crypto/ccree/cc_cipher.c
> > +++ b/drivers/crypto/ccree/cc_cipher.c
> > @@ -116,10 +116,6 @@ static int validate_data_size(struct cc_cipher_ctx *ctx_p,
> > case S_DIN_to_AES:
> > switch (ctx_p->cipher_mode) {
> > case DRV_CIPHER_XTS:
> > - if (size >= AES_BLOCK_SIZE &&
> > - IS_ALIGNED(size, AES_BLOCK_SIZE))
> > - return 0;
> > - break;
>
> You should still check for size < block size.
Look again - he does via the fall through aspect of the case.
>
> > case DRV_CIPHER_CBC_CTS:
> > if (size >= AES_BLOCK_SIZE)
> > return 0;
> > @@ -945,7 +941,7 @@ static const struct cc_alg_template skcipher_algs[] = {
> > {
> > .name = "xts(paes)",
> > .driver_name = "xts-paes-ccree",
> > - .blocksize = AES_BLOCK_SIZE,
> > + .blocksize = 1,
>
> No need for these blocksize changes - just keep them as they are.
hm... I'm a little confused about this.
Why do we have, say CTR template, announce a block size of 1 (which
makes sense since it effectively turns a block cipher to a stream
cipher) but here stick to the underlying block size?
I mean, you can request processing for any granularity (subject to the
bigger than 1 block), just like CTR so I'm not sure what information
is supposed to be conveyed here.
Thanks,
Gilad
