Auth has changed a little bit:

radius_www_authorize has been replaced by radius_www_authenticate. www_challenge has been removed and now you should use append_to_reply with a "variable" called $digest_challenge that is created id the radius_ww_authenticate fails (user not auth).

So replace your code:

                    if (!radius_www_authorize("")) {
                         www_challenge("", "1");         // parse error
                         break;
                       };

For the next lines:

if (!radius_www_authenticate("$fd.digest_realm")) { if ($digest_challenge) { append_to_reply("%$digest_challenge"); } sl_send_reply("401", "Unauthorized"); drop; }

Depending on where the auth is placed you should use 401 or 407 response code.

Hope it helps,

Samuel.