Accepting requests only from a specific domain on nginx?

Question

Nginx

Hello. There is a main site sitename.ru and an API server located at api.sitename.ru. Both are powered by Nginx.
Is it possible to configure Nginx so that api.sitename.ru only accepts requests from sitename.ru?

Answer 1

if ($http_host != "sitename.ru")  {
  return 403;
}

if ($remote_addr != 127.0.0.1) {
  return 403;
}

But if there will be no requests from outside at all, it is better to hang the api site host on a different port and close this port from outside.

Answer 2

If the site has a static address, the easiest way is to simply limit it by IP.