Nginx CORS maps

nginx-cors.conf

map $http_origin $allow_origin {
  default "$http_origin";
}

map $request_method $cors_method {
  default "allowed";
  "OPTIONS" "preflight";
}

map $cors_method $cors_max_age {
  default "";
  "preflight" 1728000;
}

map $cors_method $cors_allow_methods {
  default "";
  "preflight" "GET, POST, OPTIONS";
}

map $cors_method $cors_allow_headers {
  default "";
  "preflight" "Authorization,Content-Type,Accept,Origin,User-Agent,DNT,Cache-Control,X-Mx-ReqToken,Keep-Alive,X-Requested-With,If-Modified-Since";
}

map $cors_method $cors_content_length {
  default $initial_content_length;
  "preflight" 0;
}

map $cors_method $cors_content_type {
  default $initial_content_type;
  "preflight" "text/plain charset=UTF-8";
}

add_header Access-Control-Allow-Origin $allow_origin;
add_header Access-Control-Allow-Credentials 'true';
add_header Access-Control-Max-Age $cors_max_age;
add_header Access-Control-Allow-Methods $cors_allow_methods;
add_header Access-Control-Allow-Headers $cors_allow_headers;

set $initial_content_length $sent_http_content_length;
add_header 'Content-Length' "";
add_header 'Content-Length' $cors_content_length;

set $initial_content_type $sent_http_content_type;
add_header Content-Type "";
add_header Content-Type $cors_content_type;

if ($request_method = 'OPTIONS') {
  return 204;
}