enabling cors on a nginx server in ElasticBeanstalk?

Question

Im deploying my Nodejs app to AWS Elastic Beanstalk running nginx.

The app is essentially an api, which i can make calls to and retrieve back JSON data i.e. myapi.awselasticbeanstalk.com/api/get_stuff etc.

Im trying to enable CORS so i can access the server from my javascript application (the client).

As per amazon documentation I can edit or extend the nginx configuration adding a config file to the .ebextensions folder.

cors.config

files:
  /etc/nginx/conf.d/cors.conf:
    mode: "000644"
    owner: root
    group: root
    content: |
        location / {
             if ($request_method = 'OPTIONS') {
                add_header 'Access-Control-Allow-Origin' '*';
                add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
                #
                # Custom headers and headers various browsers *should* be OK with but aren't
                #
                add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range';
                #
                # Tell client that this pre-flight info is valid for 20 days
                #
                add_header 'Access-Control-Max-Age' 1728000;
                add_header 'Content-Type' 'text/plain; charset=utf-8';
                add_header 'Content-Length' 0;
                return 204;
             }
             if ($request_method = 'POST') {
                add_header 'Access-Control-Allow-Origin' '*';
                add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
                add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range';
                add_header 'Access-Control-Expose-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range';
             }
             if ($request_method = 'GET') {
                add_header 'Access-Control-Allow-Origin' '*';
                add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
                add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range';
                add_header 'Access-Control-Expose-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range';
             }
        }

but this is still not working for me.

Answer 1

If you set CORS headers in the response that goes out of your node/express application, you don't need to add anything to Nginx configuration.

Below is the configuration that worked for me, also running node.js on Beanstalk, and a cloudfront-hosted client application calling the API.

Modify as needed:

server.use(function(req, res, next) {
  res.header('Access-Control-Allow-Origin', '*')
  res.header('Access-Control-Allow-Credentials', true)
  res.header('Access-Control-Allow-Methods', 'POST, GET, OPTIONS')
  res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept')
  next()
})