Re: Problems with cbc(aes) and do_alg0test()

[Stephan Mueller <smueller@chronox.de>]

Am Dienstag, 23. August 2016, 22:44:39 CEST schrieb Michael McKay:

Hi Michael,

> We are writing a device driver with kernel v3.14, and trying to encrypt some
> data using the Linux kernel algorithm “cbc(aes)”. Our /proc/crypto shows
> the following is loaded: driver “cbc-aes-aesni”, module “aesni_intel”, and
> type “ablkcipher”. But crypto_has_alg() gives us an error indicating the
> algo is not loaded. So knowing we have the algo string correct, most likely
> the problem is with the two other input variables: mask or type.
 
> Since AESNI is in use, we have a decent guess at the types by looking at the
> .cra_flags field in aensi-Intel_glue.c (which has
> “CRYPTO_ALG_TYPE_ABLKCIPHER | CRYPTO_ALG_ASYNC”). That leaves just a few
> mask fields to guess at, but CRYPTO_ALG_TYPE_BLKCIPHER_MASK and
> CRYPTO_ALG_TYPE_MASK don’t work (not does OR’ing them together). 
 
> What are the correct mask and type values for AESNI, and can you point me to
> any documentation? What else might we be doing wrong? Is /proc/crypto
> giving us relevant information? Thanks,

You can only use the cbc-aes-aesni code with the ablkcipher API. Using it with 
the blkcipher API will not work.

So, a simple crypto_alloc_ablkcipher("cbc-aes-aesni", 0, 0) should work. If 
not, what is the return code?

Ciao
Stephan