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fix(session): Make session encryption more robust #47396

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4 changes: 4 additions & 0 deletions lib/base.php
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
* SPDX-License-Identifier: AGPL-3.0-only
*/
use OC\Encryption\HookManager;
use OC\Session\CryptoSessionHandler;
use OC\Share20\Hooks;
use OCP\EventDispatcher\IEventDispatcher;
use OCP\Group\Events\UserRemovedEvent;
Expand Down Expand Up @@ -363,6 +364,9 @@ private static function printUpgradePage(\OC\SystemConfig $systemConfig): void {
public static function initSession(): void {
$request = Server::get(IRequest::class);

$cryptoHandler = Server::get(CryptoSessionHandler::class);
session_set_save_handler($cryptoHandler, true);

// Do not initialize sessions for 'status.php' requests
// Monitoring endpoints can quickly flood session handlers
// and 'status.php' doesn't require sessions anyway
Expand Down
3 changes: 2 additions & 1 deletion lib/composer/composer/autoload_classmap.php
Original file line number Diff line number Diff line change
Expand Up @@ -1946,9 +1946,10 @@
'OC\\ServerContainer' => $baseDir . '/lib/private/ServerContainer.php',
'OC\\ServerNotAvailableException' => $baseDir . '/lib/private/ServerNotAvailableException.php',
'OC\\ServiceUnavailableException' => $baseDir . '/lib/private/ServiceUnavailableException.php',
'OC\\Session\\CryptoSessionData' => $baseDir . '/lib/private/Session/CryptoSessionData.php',
'OC\\Session\\CryptoSessionHandler' => $baseDir . '/lib/private/Session/CryptoSessionHandler.php',
'OC\\Session\\CryptoWrapper' => $baseDir . '/lib/private/Session/CryptoWrapper.php',
'OC\\Session\\Internal' => $baseDir . '/lib/private/Session/Internal.php',
'OC\\Session\\LegacyCryptoSessionData' => $baseDir . '/lib/private/Session/LegacyCryptoSessionData.php',
'OC\\Session\\Memory' => $baseDir . '/lib/private/Session/Memory.php',
'OC\\Session\\Session' => $baseDir . '/lib/private/Session/Session.php',
'OC\\Settings\\AuthorizedGroup' => $baseDir . '/lib/private/Settings/AuthorizedGroup.php',
Expand Down
3 changes: 2 additions & 1 deletion lib/composer/composer/autoload_static.php
Original file line number Diff line number Diff line change
Expand Up @@ -1987,9 +1987,10 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
'OC\\ServerContainer' => __DIR__ . '/../../..' . '/lib/private/ServerContainer.php',
'OC\\ServerNotAvailableException' => __DIR__ . '/../../..' . '/lib/private/ServerNotAvailableException.php',
'OC\\ServiceUnavailableException' => __DIR__ . '/../../..' . '/lib/private/ServiceUnavailableException.php',
'OC\\Session\\CryptoSessionData' => __DIR__ . '/../../..' . '/lib/private/Session/CryptoSessionData.php',
'OC\\Session\\CryptoSessionHandler' => __DIR__ . '/../../..' . '/lib/private/Session/CryptoSessionHandler.php',
'OC\\Session\\CryptoWrapper' => __DIR__ . '/../../..' . '/lib/private/Session/CryptoWrapper.php',
'OC\\Session\\Internal' => __DIR__ . '/../../..' . '/lib/private/Session/Internal.php',
'OC\\Session\\LegacyCryptoSessionData' => __DIR__ . '/../../..' . '/lib/private/Session/LegacyCryptoSessionData.php',
'OC\\Session\\Memory' => __DIR__ . '/../../..' . '/lib/private/Session/Memory.php',
'OC\\Session\\Session' => __DIR__ . '/../../..' . '/lib/private/Session/Session.php',
'OC\\Settings\\AuthorizedGroup' => __DIR__ . '/../../..' . '/lib/private/Settings/AuthorizedGroup.php',
Expand Down
124 changes: 124 additions & 0 deletions lib/private/Session/CryptoSessionHandler.php
Original file line number Diff line number Diff line change
@@ -0,0 +1,124 @@
<?php

declare(strict_types=1);

/**
* SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
* SPDX-License-Identifier: AGPL-3.0-only
*/

namespace OC\Session;

use Exception;
use OCP\IRequest;
use OCP\Security\ICrypto;
use OCP\Security\ISecureRandom;
use Psr\Log\LoggerInterface;
use SessionHandler;
use function explode;
use function implode;
use function strlen;

class CryptoSessionHandler extends SessionHandler {
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Unfortunately writing unit tests is not an option for a session handler because PHP sessions have so many side effects. E.g. an actual session has to be opened to test read/write, but you can't close and re-open the session because opening a session sets a header, and setting headers is not possible once any kind of output was written 🫠


public function __construct(private ISecureRandom $secureRandom,
private ICrypto $crypto,
private LoggerInterface $logger,
private IRequest $request) {
}

public function create_sid(): string {
$id = parent::create_sid();
$passphrase = $this->secureRandom->generate(128);
return implode('|', [$id, $passphrase]);
}

/**
* Read and decrypt session data
*
* @param string $id
*
* @return false|string
*
* @codeCoverageIgnore
*/
public function read(string $id): false|string {
[$sessionId, $passphrase] = self::parseId($id);
if ($passphrase === null) {
$passphrase = $this->request->getCookie(CryptoWrapper::COOKIE_NAME);
if ($passphrase === null) {
$this->logger->debug('Reading unencrypted session data', [
'sessionId' => $id,
]);
return parent::read($sessionId);
}
}

$possiblyEncryptedData = parent::read($sessionId);
if ($possiblyEncryptedData === '') {
return '';
}
if (str_contains($possiblyEncryptedData, 'encrypted_session_data')) {
// This data is not encrypted
return $possiblyEncryptedData;
}
try {
return $this->crypto->decrypt($possiblyEncryptedData, $passphrase);
} catch (Exception $e) {
$this->logger->error('Failed to decrypt session data', [
'exception' => $e,
'sessionId' => $sessionId,
]);
return '';
}
}

/**
* Encrypt and write session data
*
* @param string $id
* @param string $data
*
* @return bool
*
* @codeCoverageIgnore
*/
public function write(string $id, string $data): bool {
[$sessionId, $passphrase] = self::parseId($id);

if ($passphrase === null) {
$passphrase = $this->request->getCookie(CryptoWrapper::COOKIE_NAME);
if ($passphrase === null) {
$this->logger->warning('Can not write session because there is no passphrase', [
'sessionId' => $id,
'dataLength' => strlen($data),
]);
return false;
}
}

$encryptedData = $this->crypto->encrypt($data, $passphrase);

return parent::write($sessionId, $encryptedData);
}

/**
* @return bool
*
* @codeCoverageIgnore
*/
public function close(): bool {
Fixed Show fixed Hide fixed
return parent::close();
}

/**
* @param string $id
*
* @return array{0: string, 1: ?string}
*/
public static function parseId(string $id): array {
$parts = explode('|', $id, 2);
return [$parts[0], $parts[1] ?? null];
}

}
31 changes: 8 additions & 23 deletions lib/private/Session/CryptoWrapper.php
Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
<?php

declare(strict_types=1);

/**
* SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
* SPDX-FileCopyrightText: 2016 ownCloud, Inc.
Expand Down Expand Up @@ -28,8 +30,10 @@
* https://github.com/owncloud/core/pull/17866
*
* @package OC\Session
* @deprecated
*/
class CryptoWrapper {
/** @deprecated 31.0.0 */
public const COOKIE_NAME = 'oc_sessionPassphrase';

/** @var IConfig */
Expand All @@ -48,6 +52,7 @@ class CryptoWrapper {
* @param ICrypto $crypto
* @param ISecureRandom $random
* @param IRequest $request
* @depreacted 31.0.0
*/
public function __construct(IConfig $config,
ICrypto $crypto,
Expand All @@ -61,37 +66,17 @@ public function __construct(IConfig $config,
$this->passphrase = $request->getCookie(self::COOKIE_NAME);
} else {
$this->passphrase = $this->random->generate(128);
$secureCookie = $request->getServerProtocol() === 'https';
// FIXME: Required for CI
if (!defined('PHPUNIT_RUN')) {
$webRoot = \OC::$WEBROOT;
if ($webRoot === '') {
$webRoot = '/';
}

setcookie(
self::COOKIE_NAME,
$this->passphrase,
[
'expires' => 0,
'path' => $webRoot,
'domain' => '',
'secure' => $secureCookie,
'httponly' => true,
'samesite' => 'Lax',
]
);
}
}
}

/**
* @param ISession $session
* @return ISession
* @deprecated 31.0.0
*/
public function wrapSession(ISession $session) {
if (!($session instanceof CryptoSessionData)) {
return new CryptoSessionData($session, $this->crypto, $this->passphrase);
if (!($session instanceof LegacyCryptoSessionData)) {
return new LegacyCryptoSessionData($session, $this->crypto, $this->passphrase);
}

return $session;
Expand Down
15 changes: 11 additions & 4 deletions lib/private/Session/Internal.php
Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@

use OC\Authentication\Token\IProvider;
use OCP\Authentication\Exceptions\InvalidTokenException;
use OCP\IConfig;
use OCP\ILogger;
use OCP\Session\Exceptions\SessionNotAvailableException;
use Psr\Log\LoggerInterface;
Expand Down Expand Up @@ -82,18 +83,23 @@ public function exists(string $key): bool {
* @param string $key
*/
public function remove(string $key) {
if (isset($_SESSION[$key])) {
unset($_SESSION[$key]);
$reopened = $this->reopen();
unset($_SESSION[$key]);
if ($reopened) {
$this->close();
}
}

public function clear() {
$this->reopen();
$reopened = $this->reopen();
$this->invoke('session_unset');
$this->regenerateId();
$this->invoke('session_write_close');
$this->startSession(true);
$_SESSION = [];
if ($reopened) {
$this->close();
}
}

public function close() {
Expand Down Expand Up @@ -155,7 +161,8 @@ public function getId(): string {
if ($id === '') {
throw new SessionNotAvailableException();
}
return $id;
// Only return the ID part, not the passphrase
return CryptoSessionHandler::parseId($id)[0];
}

/**
Expand Down
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