[PATCH] Add XTS cipher mode

[Stephan Müller]

Am Mittwoch, 4. Januar 2017, 17:15:06 CET schrieb Jussi Kivilinna:

Hi Jussi,

> +	case GCRY_CIPHER_MODE_XTS:
> +	  /* Setup tweak cipher with second part of XTS key. */
> +	  rc = c->spec->setkey (c->u_mode.xts.tweak_context, key + keylen,
> +				keylen);
> +	  if (!rc)
> +	    {
> +	      /* Duplicate initial tweak context.  */
> +	      memcpy (c->u_mode.xts.tweak_context + c->spec->contextsize,
> +		      c->u_mode.xts.tweak_context, c->spec->contextsize);
> +	    }
> +	  else
> +	    c->marks.key = 0;
> +	  break;
> +

As libgcrypt is intended to be used in FIPS 140-2 context, can you please add 
a check that the key and tweak key are not identical? If they are, setkey 
should fail.

See https://git.kernel.org/cgit/linux/kernel/git/herbert/cryptodev-2.6.git/
tree/include/crypto/xts.h#n43 for an example code.

Thanks
Stephan