[Fixed]-FastCGI application behind NGINX is unable to detect that HTTPS secure connection is used

Thanks to Yuji for the answer. I’ve updated my server block to conditionally inject HTTPS on or HTTPS off, depending on $server_port:

{

server {
    listen       80;
    listen       443 default ssl;

    if ($server_port = 443) { set $https on; }
    if ($server_port = 80) { set $https off; }

    ssl_certificate   /home/webapp/ssl.crt
    ssl_certificate_key /home/webapp/ssl.key

    server_name  myapp.com;
    access_log /home/webapp/access.log
    error_log  /home/webapp/error.log

    root   /home/mywebapp;

    location / {
           # host and port to fastcgi server                      
       fastcgi_pass 127.0.0.1:8801;
       fastcgi_param PATH_INFO $fastcgi_script_name;
       fastcgi_param REQUEST_METHOD $request_method;
       fastcgi_param QUERY_STRING $query_string;
       fastcgi_param SERVER_NAME $server_name;
       fastcgi_param SERVER_PORT $server_port;
       fastcgi_param SERVER_PROTOCOL $server_protocol;
       fastcgi_param CONTENT_TYPE $content_type;
       fastcgi_param CONTENT_LENGTH $content_length;
       fastcgi_pass_header Authorization;
       fastcgi_intercept_errors off;

       fastcgi_param HTTPS $https;
    }
}

}