see: KallitheaAuthPluginBase.auth_func_attrs

        This is later validated for correctness

        """

        if not username or not password:

            log.debug('Empty username or password skipping...')

            return None

        kwargs = {

            'server': settings.get('host', ''),

            'base_dn': settings.get('base_dn', ''),

            'port': settings.get('port'),

            'bind_dn': settings.get('dn_user'),

            'bind_pass': settings.get('dn_pass'),

            'tls_kind': settings.get('tls_kind'),

            'tls_reqcert': settings.get('tls_reqcert'),

            'ldap_filter': settings.get('filter'),

            'search_scope': settings.get('search_scope'),

            'attr_login': settings.get('attr_login'),

            'ldap_version': 3,

        }

        if kwargs['bind_dn'] and not kwargs['bind_pass']:

            log.debug('Using dynamic binding.')

            kwargs['bind_dn'] = kwargs['bind_dn'].replace('$login', username)

            kwargs['bind_pass'] = password

        log.debug('Checking for ldap authentication')

        try:

            aldap = AuthLdap(**kwargs)

            (user_dn, ldap_attrs) = aldap.authenticate_ldap(username, password)

            log.debug('Got ldap DN response %s' % user_dn)

            get_ldap_attr = lambda k: ldap_attrs.get(settings.get(k), [''])[0]

            # old attrs fetched from Kallithea database

            admin = getattr(userobj, 'admin', False)

            active = getattr(userobj, 'active', self.user_activation_state())

            email = getattr(userobj, 'email', '')

            firstname = getattr(userobj, 'firstname', '')

            lastname = getattr(userobj, 'lastname', '')

            extern_type = getattr(userobj, 'extern_type', '')

            user_attrs = {

                'username': username,

                'firstname': safe_unicode(get_ldap_attr('attr_firstname') or firstname),

                'lastname': safe_unicode(get_ldap_attr('attr_lastname') or lastname),

                'groups': [],

                'admin': admin,

                'active': active,

                "active_from_extern": None,

                'extern_name': user_dn,

                'extern_type': extern_type,

            }

            log.info('user %s authenticated correctly' % user_attrs['username'])

            return user_attrs

        except (LdapUsernameError, LdapPasswordError, LdapImportError):

            log.error(traceback.format_exc())

            return None

        except (Exception,):

            log.error(traceback.format_exc())

            return None