fix: allow underscores in FQDNs/subdomains

Author: SpraxDev

src/minecraft/server/blocklist/FqdnValidator.ts

@@ -3,7 +3,7 @@ import { singleton } from 'tsyringe';
 @singleton()
 export default class FqdnValidator {
   // A very simple pattern to not risk false-positives (based on RFC 1034)
-  private readonly FQDN_PATTERN = /^(?:[a-z0-9-]{1,63}\.)+[a-z][a-z0-9-]{0,63}\.?$/i;
+  private readonly FQDN_PATTERN = /^(?:[a-z0-9_-]{1,63}\.)+[a-z][a-z0-9-]{0,63}\.?$/i;
 
   validateFqdn(input: string): boolean {
     return input.length <= 255 && this.FQDN_PATTERN.test(input);

tests/unit/minecraft/server/FqdnValidator.test.ts

@@ -7,7 +7,8 @@ describe('valid FQDNs', () => {
     ['foobar.example.com'],
     ['foobar.example.com.'],
     ['foo.bar'],
-    ['a.b']
+    ['a.b'],
+    ['foo_bar.example.com']
   ])('%s', (input) => {
     expect(new FqdnValidator().validateFqdn(input)).toBe(true);
   });