Hi @asmecher,
Yes, we get infinite redirects when enabling force_ssl in config.inc.php.
Any kind of protocol detection would not help in our case. The only solution we came upon is to add $_SERVER['HTTPS'] = 'on' as a first line in the index.php.
So if there is no other way, we would rather welcome some option like Behind HTTPS proxy in config.inc.php, which would work in the same manner.
Thank you!