dillard
ac82b38e37
- one locking protocol per location: backup steps and restores hold a shared lock, prune and untrash an exclusive one and refuse while any run (backup, restore, export) exists; starting a backup checks and creates the run under the exclusive lock, closing the race with prune - snapshot entries are validated when read (relative path without '.', '..', NUL, backslash or control characters); raw restore also checks that the resolved directory stays below the target; the restore API and service accept canonical paths only - recovery kit confirmation requires a recent password confirmation and the confirmation code printed in the current kit file (new code per kit version), proving the kit was actually downloaded - prune decides on the authenticated index files on the location and refreshes the local index cache from them - restore job marks the run failed on any error; restore runs without progress for 6 hours are failed so they cannot block cleanup forever - tests for safe paths and a malicious snapshot path
260 lines
11 KiB
PHP
260 lines
11 KiB
PHP
<?php
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declare(strict_types=1);
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// SPDX-FileCopyrightText: 2026 Dillard Blom
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// SPDX-License-Identifier: AGPL-3.0-or-later
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namespace OCA\NgBackup\Service;
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use OCA\NgBackup\AppInfo\Application;
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use OCA\NgBackup\Crypto\KeyRing;
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use OCP\IAppConfig;
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use OCP\Security\ICrypto;
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/**
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* The installation's backup master key.
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*
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* - The server keeps the master key encrypted with Nextcloud's own secret (ICrypto), so
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* scheduled backups run without anyone typing a passphrase. Whoever fully controls the server
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* can therefore read the backups; whoever only gets the backup location cannot.
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* - A copy wrapped with the admin's passphrase (Argon2id) goes into every repository config and
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* into the recovery kit, so backups can be restored on a fresh server with the passphrase.
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* - The admin must confirm having stored the recovery kit before the first backup runs.
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*/
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class KeyService {
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private const KEY_MASTER = 'master_key';
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private const KEY_WRAPPED = 'master_key_wrapped';
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private const KEY_CONFIRMED = 'recovery_kit_confirmed';
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private const KEY_FINGERPRINT = 'master_key_fingerprint';
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private const KEY_DELETE_DELAY = 'delete_delay_days';
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private const KEY_KIT_VERSION = 'recovery_kit_version';
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private const KEY_KIT_CODE = 'recovery_kit_code';
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public const DEFAULT_DELETE_DELAY = 7;
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private ?KeyRing $cached = null;
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public function __construct(
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private IAppConfig $appConfig,
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private ICrypto $crypto,
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) {
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}
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public function isInitialized(): bool {
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return $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true) !== '';
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}
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/**
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* @param int $deleteDelayDays how long forgotten snapshots stay in the trash on the location
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* before their data is really deleted. Fixed here, at installation:
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* there is deliberately no way to change it later from NG Backup.
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*/
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public function initialize(#[\SensitiveParameter] string $passphrase, int $deleteDelayDays = self::DEFAULT_DELETE_DELAY, string $label = 'Slot 1'): void {
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if ($deleteDelayDays < 1 || $deleteDelayDays > 365) {
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throw new \InvalidArgumentException('The deletion delay must be between 1 and 365 days');
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}
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if ($this->isInitialized()) {
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throw new \RuntimeException('A backup key already exists');
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}
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if (strlen($passphrase) < 12) {
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throw new \InvalidArgumentException('The passphrase must be at least 12 characters');
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}
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$keys = KeyRing::generate();
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$this->appConfig->setValueString(Application::APP_ID, self::KEY_MASTER,
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$this->crypto->encrypt(base64_encode($keys->exportMasterKey())), true, true);
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$this->cached = $keys;
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$this->saveSlots([['slot' => 1, 'label' => self::cleanLabel($label), 'created' => time(), 'key' => $keys->wrap($passphrase)]]);
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$this->appConfig->setValueString(Application::APP_ID, self::KEY_FINGERPRINT, $this->fingerprintOf($keys), true);
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$this->appConfig->setValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, $deleteDelayDays, true);
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$this->appConfig->setValueInt(Application::APP_ID, self::KEY_KIT_VERSION, 1, true);
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$this->appConfig->deleteKey(Application::APP_ID, self::KEY_CONFIRMED);
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$this->cached = $keys;
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}
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public function keyRing(): KeyRing {
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if ($this->cached === null) {
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$enc = $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true);
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if ($enc === '') {
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throw new \RuntimeException('No backup key yet: run occ backup:key:init');
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}
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$this->cached = new KeyRing(base64_decode($this->crypto->decrypt($enc), true));
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}
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return $this->cached;
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}
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/** Deletion delay in days, fixed at installation (installations from before this setting get the default once). */
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public function deleteDelayDays(): int {
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$days = $this->appConfig->getValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, 0, true);
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if ($days === 0 && $this->isInitialized()) {
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$days = self::DEFAULT_DELETE_DELAY;
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$this->appConfig->setValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, $days, true);
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}
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return $days;
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}
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public const MAX_SLOTS = 3;
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/** @return list<array{slot:int, label:string, created:int}> passphrase slots, without key material */
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public function slots(): array {
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return array_map(fn ($s) => ['slot' => $s['slot'], 'label' => $s['label'], 'created' => $s['created']], $this->wrappedKey()['slots']);
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}
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/** Add a passphrase slot (e.g. one per person who must be able to restore). Returns the slot number. */
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public function addSlot(#[\SensitiveParameter] string $passphrase, string $label): int {
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self::checkPassphrase($passphrase);
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$slots = $this->wrappedKey()['slots'];
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if (count($slots) >= self::MAX_SLOTS) {
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throw new \InvalidArgumentException('At most ' . self::MAX_SLOTS . ' passphrase slots');
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}
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$used = array_column($slots, 'slot');
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$n = min(array_diff(range(1, self::MAX_SLOTS), $used));
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$slots[] = ['slot' => $n, 'label' => self::cleanLabel($label), 'created' => time(), 'key' => $this->keyRing()->wrap($passphrase)];
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usort($slots, fn ($a, $b) => $a['slot'] <=> $b['slot']);
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$this->saveSlots($slots);
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return $n;
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}
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/** New passphrase for a slot (e.g. its holder left). The master key and all backups stay the same. */
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public function replaceSlot(int $slot, #[\SensitiveParameter] string $passphrase, ?string $label = null): void {
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self::checkPassphrase($passphrase);
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$slots = $this->wrappedKey()['slots'];
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$found = false;
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foreach ($slots as &$s) {
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if ($s['slot'] === $slot) {
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$s['key'] = $this->keyRing()->wrap($passphrase);
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$s['created'] = time();
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if ($label !== null) {
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$s['label'] = self::cleanLabel($label);
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}
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$found = true;
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}
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}
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unset($s);
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if (!$found) {
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throw new \InvalidArgumentException("There is no slot $slot");
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}
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$this->saveSlots($slots);
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}
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public function removeSlot(int $slot): void {
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$slots = array_values(array_filter($this->wrappedKey()['slots'], fn ($s) => $s['slot'] !== $slot));
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if (count($slots) === count($this->wrappedKey()['slots'])) {
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throw new \InvalidArgumentException("There is no slot $slot");
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}
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if ($slots === []) {
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throw new \InvalidArgumentException('The last passphrase slot cannot be removed');
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}
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$this->saveSlots($slots);
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}
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/** Every change to the slots asks for a new recovery kit (and its confirmation). */
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private function saveSlots(array $slots): void {
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$this->appConfig->setValueString(Application::APP_ID, self::KEY_WRAPPED, json_encode(['slots' => $slots], JSON_THROW_ON_ERROR), true, true);
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$this->appConfig->setValueInt(Application::APP_ID, self::KEY_KIT_VERSION, $this->kitVersion() + 1, true);
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}
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private static function checkPassphrase(string $passphrase): void {
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if (strlen($passphrase) < 12) {
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throw new \InvalidArgumentException('The passphrase must be at least 12 characters');
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}
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}
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private static function cleanLabel(string $label): string {
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$label = trim(preg_replace('/[\x00-\x1f]/', '', $label) ?? '');
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return mb_substr($label === '' ? 'Slot' : $label, 0, 64);
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}
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public function kitVersion(): int {
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return $this->appConfig->getValueInt(Application::APP_ID, self::KEY_KIT_VERSION, 1, true);
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}
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/** Passphrase-wrapped copy of the master key (for repository configs and the recovery kit). */
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public function wrappedKey(): array {
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$data = json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_WRAPPED, '{}', true), true, 512, JSON_THROW_ON_ERROR);
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if (!isset($data['slots'])) {
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$data = ['slots' => $data === [] ? [] : [['slot' => 1, 'label' => 'Slot 1', 'created' => 0, 'key' => $data]]];
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}
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return $data;
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}
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/** Short identifier of the key, shown in the UI and the kit (not secret). */
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public function fingerprint(): string {
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return $this->appConfig->getValueString(Application::APP_ID, self::KEY_FINGERPRINT, '', true);
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}
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/** @return array{version:int, app:string, fingerprint:string, created:string, wrapped_key:array, instructions:string} */
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public function recoveryKit(): array {
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return [
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'version' => 1,
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'app' => 'NG Backup',
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'fingerprint' => $this->fingerprint(),
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'kit_version' => $this->kitVersion(),
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'confirmation_code' => $this->kitCode(),
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'created' => gmdate('c'),
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'wrapped_key' => $this->wrappedKey(),
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'slots' => $this->slots(),
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'instructions' => 'Keep this file safe, outside this server. Any one of the passphrases of the slots listed here opens it. '
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. 'To restore on a new server: install NG Backup, add the backup location and enter this kit with one passphrase. '
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. 'Without the kit (or the location) and a passphrase, the backups cannot be decrypted.',
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];
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}
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/**
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* Short code printed in the current kit file. Typing it back when confirming proves the
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* admin actually has the downloaded kit. A new code per kit version; the server only keeps
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* its own copy encrypted with the instance secret.
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*/
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private function kitCode(): string {
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$stored = json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_KIT_CODE, '{}', true), true) ?: [];
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if (($stored['version'] ?? 0) === $this->kitVersion() && isset($stored['code'])) {
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return $this->crypto->decrypt($stored['code']);
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}
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$alphabet = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'; // no 0/O, 1/I
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$code = '';
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for ($i = 0; $i < 8; $i++) {
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$code .= $alphabet[random_int(0, strlen($alphabet) - 1)];
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}
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$code = substr($code, 0, 4) . '-' . substr($code, 4);
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$this->appConfig->setValueString(Application::APP_ID, self::KEY_KIT_CODE,
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json_encode(['version' => $this->kitVersion(), 'code' => $this->crypto->encrypt($code)], JSON_THROW_ON_ERROR), true, true);
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return $code;
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}
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public function checkKitCode(string $code): bool {
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$stored = json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_KIT_CODE, '{}', true), true) ?: [];
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if (($stored['version'] ?? 0) !== $this->kitVersion() || !isset($stored['code'])) {
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return false; // no kit downloaded for this version yet
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}
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$normalise = static fn (string $c) => strtoupper(preg_replace('/[^A-Za-z0-9]/', '', $c) ?? '');
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return hash_equals($normalise($this->crypto->decrypt($stored['code'])), $normalise($code));
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}
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public function confirmRecoveryKit(string $uid): void {
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$this->appConfig->setValueString(Application::APP_ID, self::KEY_CONFIRMED,
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json_encode(['uid' => $uid, 'time' => time(), 'fingerprint' => $this->fingerprint(), 'kit_version' => $this->kitVersion()], JSON_THROW_ON_ERROR), true);
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}
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/**
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* Whether a recovery kit for this key was ever confirmed (any passphrase version). Backups
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* keep running after a passphrase change, so changing it cannot be used to stop backups; the
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* missing re-confirmation is reported as an error in the admin overview instead.
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*/
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public function everConfirmed(): bool {
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$raw = $this->appConfig->getValueString(Application::APP_ID, self::KEY_CONFIRMED, '', true);
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$data = $raw === '' ? null : json_decode($raw, true);
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return $data !== null && ($data['fingerprint'] ?? '') === $this->fingerprint();
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}
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/** Confirmation for the current key and kit version, or null. */
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public function recoveryKitConfirmation(): ?array {
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$raw = $this->appConfig->getValueString(Application::APP_ID, self::KEY_CONFIRMED, '', true);
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$data = $raw === '' ? null : json_decode($raw, true);
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return ($data !== null && ($data['fingerprint'] ?? '') === $this->fingerprint() && ($data['kit_version'] ?? 1) === $this->kitVersion()) ? $data : null;
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}
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private function fingerprintOf(KeyRing $keys): string {
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$id = $keys->blobId('ng_backup key fingerprint');
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return implode('-', str_split(substr($id, 0, 16), 4));
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}
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}
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