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

.env

@@ -5,6 +5,14 @@
 # Share that value with nobody and keep it secret
 APP_SECRET=a03498528f5a5fc089273ec9ae5b2849
 
+# Change this and uncomment the following line to set the trusted hosts for your Part-DB installation, aka under which
+# domain names it is reachable. This is makes things more secure, because it can prevent certain header attacks.
+# You have to escape dots in the domain name with a backslash
+#TRUSTED_HOSTS='^(your-domain\.invalid)$'
+
+# You can also allow multiple domain names, e.g. for testing or development purposes, with an | between the domain names.
+#TRUSTED_HOSTS='^(localhost|your-domain\.invalid)$'
+
 ###################################################################################
 # Database settings
 ###################################################################################

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) === '';
+    }
+}

templates/homepage.html.twig

@@ -95,6 +95,16 @@
         </div>
     {% endif %}
 
+    {% if trusted_hosts_unconfigured and is_granted('@system.server_infos') %}
+        <div class="alert alert-warning" role="alert">
+            <h5><i class="fa-solid fa-triangle-exclamation fa-fw"></i> {% trans %}system.trusted_hosts.unconfigured.title{% endtrans %}</h5>
+            <p class="mb-1">{% trans %}system.trusted_hosts.unconfigured.message{% endtrans %}</p>
+            <p class="mb-0">{% trans %}system.trusted_hosts.unconfigured.suggestion{% endtrans %}
+                <br><code>TRUSTED_HOSTS='^({{ app.request.host|replace({'.': '\\.'}) }})$'</code></p>
+            <small>{% trans %}update_manager.new_version_available.only_administrators_can_see{% endtrans %}</small>
+        </div>
+    {% endif %}
+
     {% if is_granted('@system.show_updates') %}
         {{ nv.new_version_alert(new_version_available, new_version, new_version_url) }}
     {% endif %}

translations/messages.en.xlf

@@ -13697,6 +13697,24 @@ Buerklin-API Authentication server:
         <target>You can use this randomly generated value (share it with nobody):</target>
       </segment>
     </unit>
+    <unit id="OP7MacF" name="system.trusted_hosts.unconfigured.title">
+      <segment state="translated">
+        <source>system.trusted_hosts.unconfigured.title</source>
+        <target>TRUSTED_HOSTS not configured</target>
+      </segment>
+    </unit>
+    <unit id="88NkHLV" name="system.trusted_hosts.unconfigured.message">
+      <segment state="translated">
+        <source>system.trusted_hosts.unconfigured.message</source>
+        <target>The &lt;code&gt;TRUSTED_HOSTS&lt;/code&gt; environment variable is not set. This means Part-DB will accept requests for any host name, which can be a security risk (e.g. HTTP Host header injection). It is recommended to restrict this to the host names Part-DB is actually reachable under.</target>
+      </segment>
+    </unit>
+    <unit id="qZ_kgWT" name="system.trusted_hosts.unconfigured.suggestion">
+      <segment state="translated">
+        <source>system.trusted_hosts.unconfigured.suggestion</source>
+        <target>Set it to a regular expression matching all host names Part-DB should be reachable under in your &lt;code&gt;.env.local&lt;/code&gt; or &lt;code&gt;docker-compose.yaml&lt;/code&gt; file, e.g. based on the host name you used to access this page:</target>
+      </segment>
+    </unit>
     <unit id="cEwxoSj" name="info_providers.provider_key">
       <segment state="translated">
         <source>info_providers.provider_key</source>