configure nginx to use a proxy when connecting to upstream

it's very hard to find something on google - you get too many results from nginx and proxy alone.

so we have a nginx-docker-container which delivers some static files and should talk to a backend-server on specific locations. we gave http_proxy and https_proxy per docker-compose into the environment of the container

trying the connection with curl results in success - its because of the http_proxy/https_proxy env

we tried without env and gave curl the proxy as param to reproduce the behaviour - so its important to use this proxy to talk to the upstream

here a part of the nginx-config

server {
    listen test.virtual:443 ssl http2;
    ...
    location /up {
        proxy_pass https://backend:12345
    }

when requesting https://test.virtual/up we get an error in nginx Log: connection refused

but curl can connect:

curl -k https://backend:12345

so how can i configure nginx to use this proxy too?

I had the same issue running with nginx on Centos, this is because you are trying to set a proxy-pass with a port different from custom ports 80 and 443. To solve this, you have to enable SElinux flag httpd_can_network_connect (diasbled by default) as described in nginx documentation => https://www.nginx.com/blog/using-nginx-plus-with-selinux/

setsebool -P httpd_can_network_connect 1

enabling this flag (httpd_can_network_connect) allows processes labeled with the httpd_t context (such as NGINX) to connect to all TCP socket types that have the port_type attribute