Check cert validity

Check cert validity

In the process of checking the OCSP response there are only checks for the
correct signed OCSP answer in the function ocsp_check()
(src/modules/rlm_eap/types/rlm_eap_tls/rlm_eap_tls.c:349).

The problem is that the current code does not check the status of the certificate.
For example if a certificate is revoked. Thus, a user with a revoked certificate
is able to bypass the verification.