How to configure nginx X-Forwarded-Port to be the originally request port

Question

I am using nginx in a standard reverse proxy scenario, to pass all requests to /auth to another host, however I'm trying to use non-standard ports.

My end goal is to have the X-Forwarded-Port header set to the port that the request comes in on.

Here is my location block in nginx.conf:

location /auth/ {
    proxy_pass       http://otherhost:8090;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host $host;
    proxy_set_header X-Forwarded-Port <VAR>;
}

This nginx is running in a docker container, that is configured to forward requests from 8085 into 80 in the container, such that the nginx process is listening on 80:

0.0.0.0:8085->80/tcp

When I hit the URL:

http://localhost:8085/auth/

I am correctly redirected to http://otherhost:8090, but the X-Forwarded-Port header is missing or wrong.

Where I have <VAR> in the original block, I have tried the following:

• $server_port - This is the port nginx is listening on (80), not the request port.

• $pass_port - Seems to be null in my setup, so nginx drops the header.

• $http_port - This is a random port per request.

• $remote_port - This is a random port per request.

I can change my config at deploy time to hardcode to the known port of incoming requests, but ideally I would be able to change the front port without any change to the nginx config.

I've scoured the nginx variable list but can't find anything like $request_port. Is there any way for me to achieve my intent?

Answer 1

The only workaround I've found is to use a map rule to get the port from the http_host variable e.g.

    map $http_host $port {
      default 80;
      "~^[^\:]+:(?<p>\d+)$" $p;
    }

Answer 2

This is a just rough idea to write Nginx conf, but I am sure this can help you in redirection

server {    
    listen 80;  
    server_name host.docker.internal;   

    # By default land on localhost:80 to root so in root we copied UI build to the ngnix html dir.
    # have a look to docker-compose uiapp service.
    location / {    
            root   /usr/share/nginx/html;   
            index  index.html index.htm;    
    }   

   # after location add filter, from which every endpoint starts with or comes in endpoint 
   # so that ngnix can capture the URL and reroute it.
   # like /backend/getUserInfo/<UserId> 
   # In above example /backend is that filter which will be captured by Ngnix and reroute the flow.
    location /backend { 
        proxy_set_header X-Forwarded-Host $host;    
        proxy_set_header X-Forwarded-Server $host;  
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        #proxy_pass http://<ContainerName>:<PortNumber>; 
        # In our case Container name is as we setup in docker-compose `beservice` and port 8080
        proxy_pass http://beservice:8080;   
    }   
}

For more details you can have a look at this project

https://github.com/dupinder/NgnixDockerizedDevEnv