@Override
    public X509CRL fetch(final String crl) throws Exception {
        if (LdapUtils.isLdapConnectionUrl(crl)) {
            return fetchCRLFromLdap(crl);
        }
        return super.fetch(crl);
    }
Search operation that looks for the attribute.
support/cas-server-support-x509-core/src/main/java/org/apereo/cas/adaptors/x509/authentication/ldap/LdaptiveResourceCRLFetcher.java