fix(validation): add IP validation for custom DNS servers input

Author: ShadowArcanist

app/Livewire/Settings/Advanced.php

@@ -3,6 +3,7 @@
 namespace App\Livewire\Settings;
 
 use App\Models\InstanceSettings;
+use App\Rules\ValidDnsServers;
 use App\Rules\ValidIpOrCidr;
 use Livewire\Attributes\Validate;
 use Livewire\Component;
@@ -20,7 +21,6 @@ class Advanced extends Component
     #[Validate('boolean')]
     public bool $is_dns_validation_enabled;
 
-    #[Validate('nullable|string')]
     public ?string $custom_dns_servers = null;
 
     #[Validate('boolean')]
@@ -43,7 +43,7 @@ public function rules()
             'is_registration_enabled' => 'boolean',
             'do_not_track' => 'boolean',
             'is_dns_validation_enabled' => 'boolean',
-            'custom_dns_servers' => 'nullable|string',
+            'custom_dns_servers' => ['nullable', 'string', new ValidDnsServers],
             'is_api_enabled' => 'boolean',
             'allowed_ips' => ['nullable', 'string', new ValidIpOrCidr],
             'is_sponsorship_popup_enabled' => 'boolean',

app/Rules/ValidDnsServers.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace App\Rules;
+
+use Closure;
+use Illuminate\Contracts\Validation\ValidationRule;
+
+class ValidDnsServers implements ValidationRule
+{
+    public function validate(string $attribute, mixed $value, Closure $fail): void
+    {
+        if (empty($value)) {
+            return;
+        }
+
+        $entries = explode(',', $value);
+        $invalidEntries = [];
+
+        foreach ($entries as $entry) {
+            $entry = trim($entry);
+
+            if (empty($entry)) {
+                continue;
+            }
+
+            if (! filter_var($entry, FILTER_VALIDATE_IP)) {
+                $invalidEntries[] = $entry;
+            }
+        }
+
+        if (! empty($invalidEntries)) {
+            $fail('The following entries are not valid DNS server IP addresses: '.implode(', ', $invalidEntries));
+        }
+    }
+}