For anyone having an issue with proxy setup here is a solution for instance where apache isn't detecting that nginx received the request over ssl. It's happening because nginx isn't forwarding the protocol header so apache always things that the request is coming over http.
This affects both (nginx > apache) or (nginx > varnish > apache)
Add following line to /etc/nginx/proxy.inc
proxy_set_header X-Forwarded-Proto $scheme;