nginx CORS header for Django media (and django-filer) resources

django-media-filer-nginx.conf

# Explicitly set Access-Control-Allow-Origin header for certain 
# responses and domains that ask for files. This helps e.g. with test
# setups on the development machine and an accompanying smartphone 
# (assuming we point it to the machine's IP in local network, 10.33.1.XX 
# here), as well as production setups that involve several domains.
#
server {
  ...
  
  # django-filer has unchanging canonical URLs for any uploaded files,
  # but to allow fetching them from a different domain we need to setup
  # CORS headers explicitly, so the browser won't discard the request.
  location /filer/canonical {
    if ($http_origin ~ '^http://localhost|^http://10\.33\.1\.\d+|^https://sub\.company\.com$') {
      add_header Access-Control-Allow-Origin "$http_origin";
    }
    
    # Proxy to the Django app running at :8000.
    proxy_pass http://127.0.0.1:8000;
  }

  location /media {
    if ($http_origin ~ '^http://localhost|^http://10\.33\.1\.\d+|^https://sub\.company\.com$') {
      add_header Access-Control-Allow-Origin "$http_origin";
    }
    
    alias /var/www/media/;
  }
}