PEM_read_bio_RSAPrivateKey
privkey = PEM_read_bio_RSAPrivateKey(bio_buf, NULL, NULL, NULL);
rsa = PEM_read_bio_RSAPrivateKey(in, NULL,
rsa = PEM_read_bio_RSAPrivateKey(in, NULL,
(PEM_read_bio_of_void *)PEM_read_bio_RSAPrivateKey,
rsa = PEM_read_bio_RSAPrivateKey(infile, NULL, NULL, NULL);