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.

從 src/Auth/Source/Radius.php 第 167 行附近開始，檢查 dapphp/radius 的 src/Radius.php 第 1752 行附近所引用的回傳路徑。確認驗證失敗和通訊協定錯誤是如何表示的，然後新增涵蓋測試，證明已確認的主要節點拒絕不會重試，而錯誤仍然可以觸發故障轉移。