SSL_load_client_CA_file() reads certificates from file and returns
a STACK_OF(X509_NAME) with the subject names found.
NOTES
SSL_load_client_CA_file() reads a file of PEM formatted certificates and
extracts the X509_NAMES of the certificates found. While the name suggests
the specific usage as support function for
SSL_CTX_set_client_CA_list(3),
it is not limited to CA certificates.
EXAMPLES
Load names of CAs from file and use it as a client CA list: