add CORS headers with Nginx
Old note from 2020-10-31. May be outdated.
Sometimes, you cannot change an app to support CORS, so in order to support CORS, we can put a small reverse proxy behind the app that will add the headers.
Create a app.conf with the following:
upstream app {
server localhost:1935;
}
map $http_origin $allow_origin {
default "*";
"~^https?://(somedomain\.xyz|localhost:8080)$" "$http_origin";
}
map $request_method $cors_method {
default "allowed";
"OPTIONS" "preflight";
}
map $cors_method $cors_max_age {
default "";
"preflight" 3600;
}
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";
}
server {
listen 80;
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;
}
location / {
proxy_pass http://app;
}
}
Add the file to the /etc/nginx/conf.d folder.
With docker:
docker run -it --rm --network host -v ${PWD}/nginx.conf:/etc/nginx/conf.d/default.conf nginx