ASN1_TYPE_unpack_sequence
void *ASN1_TYPE_unpack_sequence(const ASN1_ITEM *it, const ASN1_TYPE *t);
oaep = ASN1_TYPE_unpack_sequence(&RSA_OAEP_PARAMS_it, alg->parameter);
return ASN1_TYPE_unpack_sequence(&X509_ALGOR_it, alg->parameter);
pss = ASN1_TYPE_unpack_sequence(&RSA_PSS_PARAMS_it, alg->parameter);
return ASN1_TYPE_unpack_sequence(&X509_EXTENSIONS_it, ext);