protected boolean isMemberAttributeBaseDn(String memberAttributeValue) {
    LdapServerProperties ldapServerProperties = getLdapProperties();
    Pattern pattern = Pattern.compile(String.format(IS_MEMBER_DN_REGEXP,
        ldapServerProperties.getUsernameAttribute(), ldapServerProperties.getGroupNamingAttr()));
    return pattern.matcher(memberAttributeValue).find();
  }
Determines that the member attribute can be used as a 'dn'
ambari-server/src/main/java/org/apache/ambari/server/security/ldap/AmbariLdapDataPopulator.java