Add CORS to a ruby app with nginx in Elastic Beanstalk(EBS)

cors.config

#This should be in ebextensions
container_commands:
  01setup_cors:
    command: "ruby .ebextensions/cors.rb"
  02reload_nginx:
    command: "service nginx reload"

cors.rb

#!/usr/bin/env ruby
#Adds cors to Assets

CORS_config = """
if ($request_method = 'OPTIONS') {
  add_header 'Access-Control-Allow-Origin' '*';
  add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
  #
  # Custom headers and headers various browsers *should* be OK with but aren't
  #
  add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type';
  #
  # Tell client that this pre-flight info is valid for 20 days
  #
  add_header 'Access-Control-Max-Age' 1728000;
  add_header 'Content-Type' 'text/plain charset=UTF-8';
  add_header 'Content-Length' 0;
  return 204;
}
if ($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';
}
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';
}
"""

conf_path = '/opt/elasticbeanstalk/support/conf/webapp_healthd.conf'

nginx_config = File.read(conf_path)

# if its alredy there we don't do anything
unless nginx_config.include?(CORS_config)
  nginx_config.gsub!('location /assets {', "location /assets {\n#{CORS_config}")
  File.write(conf_path, nginx_config)
end