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

["Stephan Müller" <smueller@chronox.de>]

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