This commit adds a new wrapper, random_get_bytes(), that is currently
defined to use os_get_random() as is. The places using
random_get_bytes() depend on the returned value being strong random
number, i.e., something that is infeasible for external device to
figure out. These values are used either directly as a key or as
nonces/challenges that are used as input for key derivation or
authentication.
The remaining direct uses of os_get_random() do not need as strong
random numbers to function correctly.
This attribute is not supposed to be used in the response frame (i.e.,
it is only in the EAP-Request/SIM-Notification frame) per RFC 4186
chapters 10.1 and 9.9. This is a minor bug since the server is required
to ignore the contents of the EAP-Response/SIM-Notification during
protected result indication per chapter 6.2.
EAP-AKA peer was already following the similar specification in RFC 4187,
but this was somehow missed in the EAP-SIM peer implementation.
