public String getGroupLDAPAttribute() throws GuacamoleException {
        return environment.getProperty(CASGuacamoleProperties.CAS_GROUP_LDAP_ATTRIBUTE);
    }
Returns the LDAP attribute that should be required for all LDAP-formatted
CAS groups. Any groups that do not use this attribute as the last
(leftmost) attribute of their DN should be ignored. If no such LDAP
attribute is provided, the last (leftmost) attribute should still be
used to determine the group name, but the specific attribute involved
should not be considered.

@return
    The LDAP attribute that should be required for all LDAP-formatted
    CAS groups, or null if any attribute should be allowed.

@throws GuacamoleException
    If guacamole.properties cannot be parsed.
extensions/guacamole-auth-sso/modules/guacamole-auth-sso-cas/src/main/java/org/apache/guacamole/auth/cas/conf/ConfigurationService.java