Cleanup FQDN validation logic, fallback to old hostname check (#4409)

Co-authored-by: DaneEveritt <dane@daneeveritt.com>

app/Rules/Fqdn.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace Pterodactyl\Rules;
+
+use Illuminate\Support\Arr;
+use Illuminate\Contracts\Validation\Rule;
+use Illuminate\Contracts\Validation\DataAwareRule;
+
+class Fqdn implements Rule, DataAwareRule
+{
+    protected array $data = [];
+    protected string $message = '';
+    protected ?string $schemeField = null;
+
+    /**
+     * @param array $data
+     */
+    public function setData($data): self
+    {
+        $this->data = $data;
+
+        return $this;
+    }
+
+    /**
+     * Validates that the value provided resolves to an IP address. If a scheme is
+     * specified when this rule is created additional checks will be applied.
+     *
+     * @param string $attribute
+     * @param mixed $value
+     * @return bool
+     */
+    public function passes($attribute, $value)
+    {
+        if (filter_var($value, FILTER_VALIDATE_IP)) {
+            // Check if the scheme is set to HTTPS.
+            //
+            // Unless someone owns their IP blocks and decides to pay who knows how much for a
+            // custom SSL cert, IPs will not be able to use HTTPS.  This should prevent most
+            // home users from making this mistake and wondering why their node is not working.
+            if ($this->schemeField && Arr::get($this->data, $this->schemeField) === 'https') {
+                $this->message = 'The :attribute must not be an IP address when HTTPS is enabled.';
+
+                return false;
+            }
+
+            return true;
+        }
+
+        // Lookup A and AAAA DNS records for the FQDN. Note, this function will also resolve CNAMEs
+        // for us automatically, there is no need to manually resolve them here.
+        //
+        // The error suppression is intentional, see https://bugs.php.net/bug.php?id=73149
+        $records = @dns_get_record($value, DNS_A + DNS_AAAA);
+        // If no records were returned fall back to trying to resolve the value using the hosts DNS
+        // resolution. This will not work for IPv6 which is why we prefer to use `dns_get_record`
+        // first.
+        if (!empty($records) || filter_var(gethostbyname($value), FILTER_VALIDATE_IP)) {
+            return true;
+        }
+
+        $this->message = 'The :attribute could not be resolved to a valid IP address.';
+
+        return false;
+    }
+
+    public function message(): string
+    {
+        return $this->message;
+    }
+
+    /**
+     * Returns a new instance of the rule with a defined scheme set.
+     */
+    public static function make(string $schemeField = null): self
+    {
+        return tap(new static(), function ($fqdn) use ($schemeField) {
+            $fqdn->schemeField = $schemeField;
+        });
+    }
+}