Show a warning banner on the homepage recommending to configure the trusted headers env

src/Controller/HomepageController.php

@@ -27,6 +27,7 @@ use App\Entity\Parts\Part;
 use App\Services\System\AppSecretChecker;
 use App\Services\System\BannerHelper;
 use App\Services\System\GitVersionInfoProvider;
+use App\Services\System\TrustedHostsChecker;
 use App\Services\System\UpdateAvailableFacade;
 use Doctrine\ORM\EntityManagerInterface;
 use Omines\DataTablesBundle\DataTableFactory;
@@ -41,6 +42,7 @@ class HomepageController extends AbstractController
         private readonly DataTableFactory $dataTable,
         private readonly BannerHelper $bannerHelper,
         private readonly AppSecretChecker $appSecretChecker,
+        private readonly TrustedHostsChecker $trustedHostsChecker,
     ) {
     }
 
@@ -90,6 +92,7 @@ class HomepageController extends AbstractController
             'new_version_url' => $updateAvailableManager->getLatestVersionUrl(),
             'insecure_app_secret' => $this->appSecretChecker->isInsecureSecret(),
             'suggested_app_secret' => $this->appSecretChecker->isInsecureSecret() ? $this->appSecretChecker->generateSecret() : null,
+            'trusted_hosts_unconfigured' => $this->trustedHostsChecker->isTrustedHostsUnconfigured(),
         ]);
     }
 }

src/Services/System/TrustedHostsChecker.php

@@ -0,0 +1,45 @@
+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2024 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+namespace App\Services\System;
+
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
+
+/**
+ * Checks whether the TRUSTED_HOSTS environment variable has been configured.
+ */
+final readonly class TrustedHostsChecker
+{
+    public function __construct(
+        #[Autowire('%env(TRUSTED_HOSTS)%')]
+        private string $trustedHosts,
+    ) {
+    }
+
+    /**
+     * @return bool True if TRUSTED_HOSTS is not configured (meaning Part-DB accepts requests with any Host header), false otherwise.
+     */
+    public function isTrustedHostsUnconfigured(): bool
+    {
+        return trim($this->trustedHosts) === '';
+    }
+}