PREAUTH_SEND_TO environment variable, to set a default redirection after authenticating

example.env

@@ -4,10 +4,11 @@ PREAUTH_KEY=''
 # TOTP (RFC 6238) secret/token (static random bytes) in base32
 PREAUTH_TOKEN=''
 
-# optional, change time-to-live, subdomain, text or colors
+# optional, change time-to-live, subdomain, default-redirect, text or colors
 # how long a session lasts (in minutes): 43200 is 30 days
 PREAUTH_TTL=43200
 PREAUTH_SUBDOMAIN='preauth'
+PREAUTH_SEND_TO='https://secure.example.com/'
 PREAUTH_BACKGROUND='#029386'
 PREAUTH_FOREGROUND='#ffffff'
 PREAUTH_TITLE='Pre-Authentication System'

src/Auth.php

@@ -107,6 +107,8 @@ class Auth {
         if ($this->login()) {
             if (isset($this->get['rt'])) {
                 header("Location: {$this->get['rt']}");
+            } else if (getenv('PREAUTH_SEND_TO')) {
+                header("Location: " . getenv('PREAUTH_SEND_TO'));
             }
             echo "ok $this->id";
             return;