Add help for hidden SSL termination

Author: dbu

deployment/proxies.rst

@@ -175,8 +175,31 @@ handling the request::
     // ...
     $response = $kernel->handle($request);
 
+Overriding configuration behind hidden SSL termination
+------------------------------------------------------
+
+Some cloud setups (like running a Docker container with the "Web App for Containers"
+in `Microsoft Azure`_) do SSL termination and contact your web server over http, but
+do not change the remote address nor set the ``X-Forwarded-*`` headers. This means
+the trusted proxy funcationality of Symfony can't help you.
+
+Once you made sure your server is only reachable through the cloud proxy over HTTPS
+and not through HTTP, you can override the information your web server sends to PHP.
+For Nginx, this could look like this:
+
+.. code-block:: nginx
+
+    location ~ ^/index\.php$ {
+        fastcgi_pass 127.0.0.1:9000;
+        include fastcgi.conf;
+        # Lie to symfony about the protocol and port so that it generates the correct https URLs
+        fastcgi_param SERVER_PORT "443";
+        fastcgi_param HTTPS "on";
+    }
+
 .. _`security groups`: https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-security-groups.html
 .. _`CloudFront`: https://en.wikipedia.org/wiki/Amazon_CloudFront
 .. _`CloudFront IP ranges`: https://ip-ranges.amazonaws.com/ip-ranges.json
 .. _`HTTP Host header attacks`: https://www.skeletonscribe.net/2013/05/practical-http-host-header-attacks.html
 .. _`nginx realip module`: https://nginx.org/en/docs/http/ngx_http_realip_module.html
+.. _`Microsoft Azure`: https://en.wikipedia.org/wiki/Microsoft_Azure