Nginx, how to disable invalid subdomains?

Question

Nginx

Recently, entries began to appear in the logs:

[Django] ERROR (EXTERNAL IP): Invalid HTTP_HOST header: '_tcp.domain.name. The domain name provided is not valid according to RFC 1034/1035

It was decided to cut such invalid domains on nginx. Google found the following regex for validation: https://stackoverflow.com/a/7933253/13084502

In the nginx config I wrote:

map $host $host_valid {                                                                                                                                                                       
    "~^(?!.{256})(?:[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+(?:[a-z]{1,63}|xn--[a-z0-9]{1,59})$" 1;                                                                                           
    default 0;                                                                                                                                                                                
}                                                                                                                                                                                             
                                                                                                                                                                                              
server {                                                                                                                                                                                      
    listen 443 ssl;                                                                                                                                                                           
                                                                                                                                                                                              
    server_name ~^(\w+)\.domain.name$;                                                                                                                                    
                                                                                                                                                                                              
    if ($host_valid = 0) {                                                                                                                                                                    
        return 444;                                                                                                                                                                           
    }                                                                                                                                                                                         
                                                                                                                                                                                              
    ...
}

It works on the test server. Because I don’t have enough experience in configuring nginx, so before pushing it to the worker I ask for advice: is this solution correct, are there any pitfalls? Confuses the presence of if. As I understand it, this is not welcome among professionals. Maybe there is a simpler and more elegant solution?

Answer 1

You don't need to cut anything on purpose, it's enough to configure default_server with a twist, which will not skip requests for hosts not listed in the settings.
upd. read your comment above - but it doesn't change anything. Add server_namewith a wildcard that will process any of your subdomains, and the rest will fight back.