When using a combination of NginX and Apache2 web services, simply enabling SSL in Joomla/WordPress can be non-trivial. This is due to the fact that with this architecture, NginX acts as a Reverse SSL Proxy, and the scripts themselves are processed in the context of environment variables Apache2, which does not initialize the HTTPS=on variable, which is necessary for PHP scripts to “understanding” that they work using the HTTPS protocol.

To fix this, you need to add the following line under root to the <VirtualHost> section of the Apache2 config:

SetEnvIfNoCase X-Forwarded-Proto https HTTPS=on