fix(session): Make session encryption more robust #47396
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,107 @@ | ||
| <?php | ||
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| declare(strict_types=1); | ||
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| /** | ||
| * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors | ||
| * SPDX-License-Identifier: AGPL-3.0-only | ||
| */ | ||
|
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| namespace OC\Session; | ||
|
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| 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 json_decode; | ||
| use function OCP\Log\logger; | ||
| use function session_decode; | ||
| use function session_encode; | ||
| use function strlen; | ||
|
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| class CryptoSessionHandler extends SessionHandler { | ||
|
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| public function __construct(private ISecureRandom $secureRandom, | ||
| private ICrypto $crypto, | ||
| private LoggerInterface $logger, | ||
| private IRequest $request) { | ||
| } | ||
|
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| public function create_sid(): string { | ||
| $id = parent::create_sid(); | ||
| $passphrase = $this->secureRandom->generate(128); | ||
| return implode('|', [$id, $passphrase]); | ||
| } | ||
|
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| /** | ||
| * Read and decrypt session data | ||
| * | ||
| * @param string $id | ||
| * | ||
| * @return false|string | ||
| */ | ||
| 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); | ||
| } | ||
| } | ||
|
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| $encryptedData = parent::read($sessionId); | ||
| if ($encryptedData === '') { | ||
| return ''; | ||
| } | ||
| return $this->crypto->decrypt($encryptedData, $passphrase); | ||
|
There was a problem hiding this comment. TODO: catch decryption error, log and continue with empty session data |
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| } | ||
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| /** | ||
| * Encrypt and write session data | ||
| * | ||
| * @param string $id | ||
| * @param string $data | ||
| * | ||
| * @return bool | ||
| */ | ||
| public function write(string $id, string $data): bool { | ||
| [$sessionId, $passphrase] = self::parseId($id); | ||
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| 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; | ||
| } | ||
| } | ||
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| $encryptedData = $this->crypto->encrypt($data, $passphrase); | ||
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| return parent::write($sessionId, $encryptedData); | ||
| } | ||
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| public function close(): bool { | ||
|
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| return parent::close(); | ||
| } | ||
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| /** | ||
| * @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]; | ||
| } | ||
|
|
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| } | ||
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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 🫠