func Lookup(s config.Config, rootCAs *x509.CertPool) (l Config, err error) {
	l = Config{}

	// Purge all removed keys first
	kvs := s[config.IdentityLDAPSubSys][config.Default]
	if len(kvs) > 0 {
		for _, k := range removedKeys {
			kvs.Delete(k)
		}
		s[config.IdentityLDAPSubSys][config.Default] = kvs
	}

	if err := s.CheckValidKeys(config.IdentityLDAPSubSys, removedKeys); err != nil {
		return l, err
	}