TYPO3 Core

When you're website is served on port 80 (http) but is accessed through a reverse-proxy that allows both http (80) and https (443), thus acts as an SSL end-point, there is no way to check if SSL is on.

A reverse-proxy already sets an additional header X-Forwarded-For for the real remote IP. In addition, SSL end-point reverse-proxy typically set one of those header for the actual protocol:

1. X-Forwarded-Proto (either "http" or "https"), typically used by Nginx
2. X-Forwarded-Ssl (either "on" or "off"), typically used by Apache
3. Front-End-Https (either "on" or "off"), typically used by ISA server (http://support.microsoft.com/kb/307347)

This additional header, when present, should be taken into account by t3lib_div::getIndpEnv() with parameter 'TYPO3_SSL' to properly allow testing it in TS conditions for instance.