Qualcomm QCE driver: XTS setkey only allows 128 bit AES

Qualcomm QCE driver: XTS setkey only allows 128 bit AES

[Stephan Müller]

Hi,

The Qualcomm QCE driver implementation defines:

                .flags          = QCE_ALG_AES | QCE_MODE_XTS,
                .name           = "xts(aes)",
                .drv_name       = "xts-aes-qce",
                .blocksize      = AES_BLOCK_SIZE,
                .ivsize         = AES_BLOCK_SIZE,
                .min_keysize    = AES_MIN_KEY_SIZE,
                .max_keysize    = AES_MAX_KEY_SIZE,

and

        alg->cra_ablkcipher.min_keysize = def->min_keysize;
        alg->cra_ablkcipher.max_keysize = def->max_keysize;
        alg->cra_ablkcipher.setkey = qce_ablkcipher_setkey;

Thus, this driver has the limits of 128 to 256 bits for the key. Furthermore, 
the common setkey function is used.

May I ask how the key for AES XTS is supposed to be handled here considering 
that the kernel crypto API expects that the AES key and the tweak key is set 
via one setkey call. I.e. the setkey should expect 256 through 512 bits.

Thanks.

Ciao
Stephan

Re: Qualcomm QCE driver: XTS setkey only allows 128 bit AES

[Herbert Xu]

Stephan Müller <smueller@chronox.de> wrote:
> Hi,
> 
> The Qualcomm QCE driver implementation defines:
> 
>                .flags          = QCE_ALG_AES | QCE_MODE_XTS,
>                .name           = "xts(aes)",
>                .drv_name       = "xts-aes-qce",
>                .blocksize      = AES_BLOCK_SIZE,
>                .ivsize         = AES_BLOCK_SIZE,
>                .min_keysize    = AES_MIN_KEY_SIZE,
>                .max_keysize    = AES_MAX_KEY_SIZE,
> 
> and
> 
>        alg->cra_ablkcipher.min_keysize = def->min_keysize;
>        alg->cra_ablkcipher.max_keysize = def->max_keysize;
>        alg->cra_ablkcipher.setkey = qce_ablkcipher_setkey;
> 
> Thus, this driver has the limits of 128 to 256 bits for the key. Furthermore, 
> the common setkey function is used.
> 
> May I ask how the key for AES XTS is supposed to be handled here considering 
> that the kernel crypto API expects that the AES key and the tweak key is set 
> via one setkey call. I.e. the setkey should expect 256 through 512 bits.

If the hardware doesn't support it then it needs to be handled with
a fallback.  Shouldn't testmgr catch this though?

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: Qualcomm QCE driver: XTS setkey only allows 128 bit AES

[Stephan Müller]

Am Mittwoch, 15. Februar 2017, 12:02:43 CET schrieb Herbert Xu:

Hi Herbert,

> Stephan Müller <smueller@chronox.de> wrote:
> > Hi,
> > 
> > The Qualcomm QCE driver implementation defines:
> >                .flags          = QCE_ALG_AES | QCE_MODE_XTS,
> >                .name           = "xts(aes)",
> >                .drv_name       = "xts-aes-qce",
> >                .blocksize      = AES_BLOCK_SIZE,
> >                .ivsize         = AES_BLOCK_SIZE,
> >                .min_keysize    = AES_MIN_KEY_SIZE,
> >                .max_keysize    = AES_MAX_KEY_SIZE,
> > 
> > and
> > 
> >        alg->cra_ablkcipher.min_keysize = def->min_keysize;
> >        alg->cra_ablkcipher.max_keysize = def->max_keysize;
> >        alg->cra_ablkcipher.setkey = qce_ablkcipher_setkey;
> > 
> > Thus, this driver has the limits of 128 to 256 bits for the key.
> > Furthermore, the common setkey function is used.
> > 
> > May I ask how the key for AES XTS is supposed to be handled here
> > considering that the kernel crypto API expects that the AES key and the
> > tweak key is set via one setkey call. I.e. the setkey should expect 256
> > through 512 bits.
> If the hardware doesn't support it then it needs to be handled with
> a fallback.  Shouldn't testmgr catch this though?

It should be caught there because there are test vectors with a klen of 64 
bytes. Thus, the setkey should fail.

Ciao
Stephan