mmc-utils: RPMB: add HMAC SHA256 support

RPMB requires digital signature of the message.  Take the implementation
of HMAC SHA256 from this place

Actually this is BSD license, IANAL but according to my understanding
nothing terrible will happen if we provide all the original copyrights.

Signed-off-by: Roman Pen <>
Cc: Ben Gardiner <>
Signed-off-by: Chris Ball <>
5 files changed