RADIUS authentication is retried at secondary server even if first server returned Auth Failure

We have configured two RADIUS servers for failover. Recently, I noticed that failed authentications from the primary are immediately re-asked at the secondary server (which still generates and Auth failure, so the end result is consistent and no harm done).

But there's really no point in asking the failover server if the primary is sure that the auth failed.

Looking at the code, I found a logic error here:

https://github.com/simplesamlphp/simplesamlphp-module-radius/blob/27d7591603dd2665a147857a4f8adcd33eb6d6cf/src/Auth/Source/Radius.php#L167

The code considers the RADIUS query successful only if it returns not-false.

The underlying library returns sth not-false only in case the authentication succeeded. Notably, a failed authentication is as "false" as a protocol error. See the return paths of its function: they are either outright "false" or compare whether the authentication was a success:

https://github.com/dapphp/radius/blob/master/src/Radius.php#L1752

I.e. error conditions and a negative outcome both have the same result; and the calling module in SSP will loop over all configured servers in both cases. Only a positive result breaks out of the loop.

Ideally, a confirmed negative result from the primary authentication server should be taken as-is.

Inizia da src/Auth/Source/Radius.php intorno alla riga 167 e analizza i percorsi di ritorno a cui si fa riferimento in src/Radius.php di dapphp/radius intorno alla riga 1752. Verifica come vengono rappresentati i fallimenti di autenticazione e gli errori di protocollo, quindi aggiungi una copertura che dimostri che un rifiuto primario confermato non viene ritentato, mentre un errore può ancora attivare un failover.