M1: key management, backup locations and occ commands

- migration: ngb_targets, ngb_runs, ngb_snapshots - KeyService: master key stored encrypted with the instance secret (unattended backups), passphrase-wrapped copy in every repository and in the recovery kit, recorded admin confirmation per key fingerprint - TargetService: locations built from files_external backends without a mount; files_external is loaded through IAppManager::loadApp() and its enabled state is left alone; credentials encrypted with ICrypto; existing repositories are adopted only if made with this key, and a repository cannot be registered twice - Repository: initWithKey/openWithKey with an encrypted key check - occ: backup:key:init|kit|confirm, backup:target:backends|add|list|remove
2026-10-02 00:37:18 +02:00
parent 4a13f8e791
commit b42acb41c5
16 changed files with 818 additions and 4 deletions
@@ -0,0 +1,110 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\AppInfo\Application;
+use OCA\NgBackup\Crypto\KeyRing;
+use OCP\IAppConfig;
+use OCP\Security\ICrypto;
+
+/**
+ * The installation's backup master key.
+ *
+ * - The server keeps the master key encrypted with Nextcloud's own secret (ICrypto), so
+ *   scheduled backups run without anyone typing a passphrase. Whoever fully controls the server
+ *   can therefore read the backups; whoever only gets the backup location cannot.
+ * - A copy wrapped with the admin's passphrase (Argon2id) goes into every repository config and
+ *   into the recovery kit, so backups can be restored on a fresh server with the passphrase.
+ * - The admin must confirm having stored the recovery kit before the first backup runs.
+ */
+class KeyService {
+	private const KEY_MASTER = 'master_key';
+	private const KEY_WRAPPED = 'master_key_wrapped';
+	private const KEY_CONFIRMED = 'recovery_kit_confirmed';
+	private const KEY_FINGERPRINT = 'master_key_fingerprint';
+
+	private ?KeyRing $cached = null;
+
+	public function __construct(
+		private IAppConfig $appConfig,
+		private ICrypto $crypto,
+	) {
+	}
+
+	public function isInitialized(): bool {
+		return $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true) !== '';
+	}
+
+	public function initialize(#[\SensitiveParameter] string $passphrase): void {
+		if ($this->isInitialized()) {
+			throw new \RuntimeException('A backup key already exists');
+		}
+		if (strlen($passphrase) < 12) {
+			throw new \InvalidArgumentException('The passphrase must be at least 12 characters');
+		}
+		$keys = KeyRing::generate();
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_MASTER,
+			$this->crypto->encrypt(base64_encode($keys->exportMasterKey())), true, true);
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_WRAPPED,
+			json_encode($keys->wrap($passphrase), JSON_THROW_ON_ERROR), true, true);
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_FINGERPRINT, $this->fingerprintOf($keys), true);
+		$this->appConfig->deleteKey(Application::APP_ID, self::KEY_CONFIRMED);
+		$this->cached = $keys;
+	}
+
+	public function keyRing(): KeyRing {
+		if ($this->cached === null) {
+			$enc = $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true);
+			if ($enc === '') {
+				throw new \RuntimeException('No backup key yet: run occ backup:key:init');
+			}
+			$this->cached = new KeyRing(base64_decode($this->crypto->decrypt($enc), true));
+		}
+		return $this->cached;
+	}
+
+	/** Passphrase-wrapped copy of the master key (for repository configs and the recovery kit). */
+	public function wrappedKey(): array {
+		return json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_WRAPPED, '{}', true), true, 512, JSON_THROW_ON_ERROR);
+	}
+
+	/** Short identifier of the key, shown in the UI and the kit (not secret). */
+	public function fingerprint(): string {
+		return $this->appConfig->getValueString(Application::APP_ID, self::KEY_FINGERPRINT, '', true);
+	}
+
+	/** @return array{version:int, app:string, fingerprint:string, created:string, wrapped_key:array, instructions:string} */
+	public function recoveryKit(): array {
+		return [
+			'version' => 1,
+			'app' => 'NG Backup',
+			'fingerprint' => $this->fingerprint(),
+			'created' => gmdate('c'),
+			'wrapped_key' => $this->wrappedKey(),
+			'instructions' => 'Keep this file and your passphrase safe, outside this server. To restore on a new server: install NG Backup, '
+				. 'add the backup location, and enter this kit with your passphrase. Without both, the backups cannot be decrypted.',
+		];
+	}
+
+	public function confirmRecoveryKit(string $uid): void {
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_CONFIRMED,
+			json_encode(['uid' => $uid, 'time' => time(), 'fingerprint' => $this->fingerprint()], JSON_THROW_ON_ERROR), true);
+	}
+
+	/** Confirmation for the current key, or null. */
+	public function recoveryKitConfirmation(): ?array {
+		$raw = $this->appConfig->getValueString(Application::APP_ID, self::KEY_CONFIRMED, '', true);
+		$data = $raw === '' ? null : json_decode($raw, true);
+		return ($data !== null && ($data['fingerprint'] ?? '') === $this->fingerprint()) ? $data : null;
+	}
+
+	private function fingerprintOf(KeyRing $keys): string {
+		$id = $keys->blobId('ng_backup key fingerprint');
+		return implode('-', str_split(substr($id, 0, 16), 4));
+	}
+}