Show a warning if using the default APP_SECRET value

src/Services/System/AppSecretChecker.php

@@ -0,0 +1,62 @@
+<?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 APP_SECRET has been changed from the default value shipped with Part-DB.
+ */
+final readonly class AppSecretChecker
+{
+    /** Known default/example secrets that must not be used in production. */
+    public const INSECURE_SECRETS = [
+        'a03498528f5a5fc089273ec9ae5b2849', // default in .env
+        '318b5d659e07a0b3f96d9b3a83b254ca', // default in .env.dev
+    ];
+
+    public function __construct(
+        #[Autowire('%kernel.secret%')]
+        private string $appSecret,
+    ) {
+    }
+
+    /**
+     * @return bool True if the app secret is one of the known insecure default secrets, false otherwise.
+     */
+    public function isInsecureSecret(): bool
+    {
+        return in_array($this->appSecret, self::INSECURE_SECRETS, true);
+    }
+
+    /**
+     * Generates a new random app secret that can be used to replace the default insecure one.
+     * @return string
+     * @throws \Random\RandomException
+     */
+    public function generateSecret(): string
+    {
+        //Symfony docs recommend 32 characters for the app secret, which are 16 random bytes when hex-encoded.
+        return bin2hex(random_bytes(16));
+    }
+}