Nginx configuration for CORS-enabled HTTPS proxy with origin white-list defined by a simple regex

cors.nginxconf

#
# Acts as a nginx HTTPS proxy server
# enabling CORS only to domains matched by regex 
# /https?://.*\.mckinsey\.com(:[0-9]+)?)/
#
# Based on: 
# * http://blog.themillhousegroup.com/2013/05/nginx-as-cors-enabled-https-proxy.html
# * http://enable-cors.org/server_nginx.html
#
server {
  listen 443 default_server ssl;
  server_name localhost;

  # Fake certs - fine for development purposes :-)
  ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem;
  ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;

  ssl_session_timeout 5m;

  location / {
    proxy_redirect off;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  
    # Nginx doesn't support nested If statements, so we
    # concatenate compound conditions on the $cors variable
    # and process later

    # If request comes from allowed subdomain
    # (*.mckinsey.com) then we enable CORS
    if ($http_origin ~* (https?://.*\.mckinsey\.com(:[0-9]+)?$)) {
       set $cors "1";
    }
  
    # OPTIONS indicates a CORS pre-flight request
    if ($request_method = 'OPTIONS') {
       set $cors "${cors}o";
    }
  
    # Append CORS headers to any request from 
    # allowed CORS domain, except OPTIONS
    if ($cors = "1") {
       more_set_headers 'Access-Control-Allow-Origin: $http_origin';
       more_set_headers 'Access-Control-Allow-Credentials: true';
       proxy_pass      http://serverIP:serverPort;
    }
  
    # OPTIONS (pre-flight) request from allowed 
    # CORS domain. return response directly
    if ($cors = "1o") {
       more_set_headers 'Access-Control-Allow-Origin: $http_origin';
       more_set_headers 'Access-Control-Allow-Methods: GET, POST, OPTIONS, PUT, DELETE';
       more_set_headers 'Access-Control-Allow-Credentials: true';
       more_set_headers 'Access-Control-Allow-Headers: Origin,Content-Type,Accept';
       add_header Content-Length 0;
       add_header Content-Type text/plain;
       return 204;
    }
  
    # Requests from non-allowed CORS domains
       proxy_pass      http://serverIP:serverPort;
  }
}