Am Dienstag, 18. November 2014, 22:08:23 schrieb Herbert Xu:

Hi Herbert,

On Sun, Nov 16, 2014 at 03:24:25AM +0100, Stephan Mueller wrote:

quoted

The AF_ALG interface allows normal cipher (hash, encrypt, decrypt).
However, it does not allow user space to obtain the following generic

information about the currently active cipher:
	* block size of the cipher
	
	* IV size of the cipher
	
	* for AEAD, the maximum authentication tag size

The patch adds a getsockopt interface for the symmetric ciphers to
answer such information requests from user space.

The kernel crypto API function calls are used to obtain the real data.
As all data are simple integer values, the getsockopt handler function
uses put_user() to return the integer value to user space in the
*optval parameter of getsockopt.

Signed-off-by: Stephan Mueller <redacted>

We already have crypto_user so you should be extending that to
cover what's missing.

Looking into that, I think nothing is missing -- thanks for the pointer. Thus 
I think I can withdraw that patch and just simply update libkcapi to use that 
user space netlink interface.

Though, I yet have to try using that interface ;-)

I am wondering why cryptouser.h is in include/linux -- shouldn't it be in 
include/uapi/linux? Aren't the definitions in that header file needed for 
userspace to talk to the netlink socket? I guess that is also the reason why I 
do not see the interface API details in /usr/linux on my F21 system.

PS These paramters should not vary depending on the implementation,
if they do then one of the implementations must be buggy.

Cheers,

-- 
Ciao
Stephan