nextcloud/apps/files_encryption/lib/keymanager.php

<?php

/**
 * ownCloud
 *
 * @author Bjoern Schiessle
 * @copyright 2012 Bjoern Schiessle <schiessle@owncloud.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or any later version.
 *
 * This library 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 library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

namespace OCA\Encryption;

/**
 * Class to manage storage and retrieval of encryption keys
 * @note Where a method requires a view object, it's root must be '/'
 */
class Keymanager {

	/**
	 * retrieve the ENCRYPTED private key from a user
	 *
	 * @param \OC\Files\View $view
	 * @param string $user
	 * @return string private key or false (hopefully)
	 * @note the key returned by this method must be decrypted before use
	 */
	public static function getPrivateKey(\OC\Files\View $view, $user) {

		$path = '/' . $user . '/' . 'files_encryption' . '/' . $user . '.private.key';
		$key = false;

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		if ($view->file_exists($path)) {
			$key = $view->file_get_contents($path);
		}

		\OC_FileProxy::$enabled = $proxyStatus;

		return $key;
	}

	/**
	 * retrieve public key for a specified user
	 * @param \OC\Files\View $view
	 * @param string $userId
	 * @return string public key or false
	 */
	public static function getPublicKey(\OC\Files\View $view, $userId) {

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		$result = $view->file_get_contents('/public-keys/' . $userId . '.public.key');

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;

	}

	/**
	 * Retrieve a user's public and private key
	 * @param \OC\Files\View $view
	 * @param string $userId
	 * @return array keys: privateKey, publicKey
	 */
	public static function getUserKeys(\OC\Files\View $view, $userId) {

		return array(
			'publicKey' => self::getPublicKey($view, $userId),
			'privateKey' => self::getPrivateKey($view, $userId)
		);

	}

	/**
	 * Retrieve public keys for given users
	 * @param \OC\Files\View $view
	 * @param array $userIds
	 * @return array of public keys for the specified users
	 */
	public static function getPublicKeys(\OC\Files\View $view, array $userIds) {

		$keys = array();

		foreach ($userIds as $userId) {

			$keys[$userId] = self::getPublicKey($view, $userId);

		}

		return $keys;

	}

	/**
	 * store file encryption key
	 *
	 * @param \OC\Files\View $view
	 * @param \OCA\Encryption\Util $util
	 * @param string $path relative path of the file, including filename
	 * @param string $catfile keyfile content
	 * @return bool true/false
	 * @note The keyfile is not encrypted here. Client code must
	 * asymmetrically encrypt the keyfile before passing it to this method
	 */
	public static function setFileKey(\OC\Files\View $view, $util, $path, $catfile) {

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		list($owner, $filename) = $util->getUidAndFilename($path);

		// in case of system wide mount points the keys are stored directly in the data directory
		if ($util->isSystemWideMountPoint($filename)) {
			$basePath = '/files_encryption/keyfiles';
		} else {
			$basePath = '/' . $owner . '/files_encryption/keyfiles';
		}

		$targetPath = self::keySetPreparation($view, $filename, $basePath);

		// try reusing key file if part file
		if (Helper::isPartialFilePath($targetPath)) {

			$result = $view->file_put_contents(
				$basePath . '/' . Helper::stripPartialFileExtension($targetPath) . '.key', $catfile);

		} else {

			$result = $view->file_put_contents($basePath . '/' . $targetPath . '.key', $catfile);

		}

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;

	}

	/**
	 * retrieve keyfile for an encrypted file
	 * @param \OC\Files\View $view
	 * @param \OCA\Encryption\Util $util
	 * @param string|false $filePath
	 * @internal param \OCA\Encryption\file $string name
	 * @return string file key or false
	 * @note The keyfile returned is asymmetrically encrypted. Decryption
	 * of the keyfile must be performed by client code
	 */
	public static function getFileKey($view, $util, $filePath) {


		list($owner, $filename) = $util->getUidAndFilename($filePath);
		$filename = Helper::stripPartialFileExtension($filename);
		$filePath_f = ltrim($filename, '/');

		// in case of system wide mount points the keys are stored directly in the data directory
		if ($util->isSystemWideMountPoint($filename)) {
			$keyfilePath = '/files_encryption/keyfiles/' . $filePath_f . '.key';
		} else {
			$keyfilePath = '/' . $owner . '/files_encryption/keyfiles/' . $filePath_f . '.key';
		}

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		if ($view->file_exists($keyfilePath)) {

			$result = $view->file_get_contents($keyfilePath);

		} else {

			$result = false;

		}

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;

	}

	/**
	 * Delete a keyfile
	 *
	 * @param \OC\Files\View $view
	 * @param string $path path of the file the key belongs to
	 * @param string $userId the user to whom the file belongs
	 * @return bool Outcome of unlink operation
	 * @note $path must be relative to data/user/files. e.g. mydoc.txt NOT
	 *       /data/admin/files/mydoc.txt
	 */
	public static function deleteFileKey($view, $path, $userId=null) {

		$trimmed = ltrim($path, '/');

		if ($trimmed === '') {
			\OCP\Util::writeLog('Encryption library',
				'Can\'t delete file-key empty path given!', \OCP\Util::ERROR);
			return false;
		}

		if ($userId === null) {
			$userId = Helper::getUser($path);
		}
		$util = new Util($view, $userId);

		if($util->isSystemWideMountPoint($path)) {
			$keyPath = '/files_encryption/keyfiles/' . $trimmed;
		} else {
			$keyPath = '/' . $userId . '/files_encryption/keyfiles/' . $trimmed;
		}

		$result = false;
		$fileExists = $view->file_exists('/' . $userId . '/files/' . $trimmed);

		if ($view->is_dir($keyPath) && !$fileExists) {
			\OCP\Util::writeLog('files_encryption', 'deleteFileKey: delete file key: ' . $keyPath, \OCP\Util::DEBUG);
			$result = $view->unlink($keyPath);
		} elseif ($view->file_exists($keyPath . '.key') && !$fileExists) {
			\OCP\Util::writeLog('files_encryption', 'deleteFileKey: delete file key: ' . $keyPath, \OCP\Util::DEBUG);
			$result = $view->unlink($keyPath . '.key');

		}

		if ($fileExists) {
			\OCP\Util::writeLog('Encryption library',
					'Did not delete the file key, file still exists: ' . '/' . $userId . '/files/' . $trimmed, \OCP\Util::ERROR);
		} elseif (!$result) {
			\OCP\Util::writeLog('Encryption library',
					'Could not delete keyfile; does not exist: "' . $keyPath, \OCP\Util::ERROR);
		}

		return $result;

	}

	/**
	 * store private key from the user
	 * @param string $key
	 * @return bool
	 * @note Encryption of the private key must be performed by client code
	 * as no encryption takes place here
	 */
	public static function setPrivateKey($key, $user = '') {

		if ($user === '') {
			$user = \OCP\User::getUser();
		}

		$header = Crypt::generateHeader();

		$view = new \OC\Files\View('/' . $user . '/files_encryption');

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		if (!$view->file_exists('')) {
			$view->mkdir('');
		}

		$result = $view->file_put_contents($user . '.private.key', $header . $key);

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;

	}

	/**
	 * write private system key (recovery and public share key) to disk
	 *
	 * @param string $key encrypted key
	 * @param string $keyName name of the key file
	 * @return boolean
	 */
	public static function setPrivateSystemKey($key, $keyName) {

		$header = Crypt::generateHeader();

		$view = new \OC\Files\View('/owncloud_private_key');

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		if (!$view->file_exists('')) {
			$view->mkdir('');
		}

		$result = $view->file_put_contents($keyName, $header . $key);

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;
	}

	/**
	 * store share key
	 *
	 * @param \OC\Files\View $view
	 * @param string $path where the share key is stored
	 * @param string $shareKey
	 * @return bool true/false
	 * @note The keyfile is not encrypted here. Client code must
	 * asymmetrically encrypt the keyfile before passing it to this method
	 */
	private static function setShareKey(\OC\Files\View $view, $path, $shareKey) {

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		$result = $view->file_put_contents($path, $shareKey);

		\OC_FileProxy::$enabled = $proxyStatus;

		if (is_int($result) && $result > 0) {
			return true;
		} else {
			return false;
		}
	}

	/**
	 * store multiple share keys for a single file
	 * @param \OC\Files\View $view
	 * @param \OCA\Encryption\Util $util
	 * @param string $path
	 * @param array $shareKeys
	 * @return bool
	 */
	public static function setShareKeys(\OC\Files\View $view, $util, $path, array $shareKeys) {

		// $shareKeys must be  an array with the following format:
		// [userId] => [encrypted key]

		list($owner, $filename) = $util->getUidAndFilename($path);

		// in case of system wide mount points the keys are stored directly in the data directory
		if ($util->isSystemWideMountPoint($filename)) {
			$basePath = '/files_encryption/share-keys';
		} else {
			$basePath = '/' . $owner . '/files_encryption/share-keys';
		}

		$shareKeyPath = self::keySetPreparation($view, $filename, $basePath);

		$result = true;

		foreach ($shareKeys as $userId => $shareKey) {

			// try reusing key file if part file
			if (Helper::isPartialFilePath($shareKeyPath)) {
				$writePath = $basePath . '/' . Helper::stripPartialFileExtension($shareKeyPath) . '.' . $userId . '.shareKey';
			} else {
				$writePath = $basePath . '/' . $shareKeyPath . '.' . $userId . '.shareKey';
			}

			if (!self::setShareKey($view, $writePath, $shareKey)) {

				// If any of the keys are not set, flag false
				$result = false;
			}
		}

		// Returns false if any of the keys weren't set
		return $result;
	}

	/**
	 * retrieve shareKey for an encrypted file
	 * @param \OC\Files\View $view
	 * @param string $userId
	 * @param \OCA\Encryption\Util $util
	 * @param string $filePath
	 * @return string file key or false
	 * @note The sharekey returned is encrypted. Decryption
	 * of the keyfile must be performed by client code
	 */
	public static function getShareKey(\OC\Files\View $view, $userId, $util, $filePath) {

		// try reusing key file if part file
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		list($owner, $filename) = $util->getUidAndFilename($filePath);
		$filename = Helper::stripPartialFileExtension($filename);
		// in case of system wide mount points the keys are stored directly in the data directory
		if ($util->isSystemWideMountPoint($filename)) {
			$shareKeyPath = '/files_encryption/share-keys/' . $filename . '.' . $userId . '.shareKey';
		} else {
			$shareKeyPath = '/' . $owner . '/files_encryption/share-keys/' . $filename . '.' . $userId . '.shareKey';
		}

		if ($view->file_exists($shareKeyPath)) {

			$result = $view->file_get_contents($shareKeyPath);

		} else {

			$result = false;

		}

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;

	}

	/**
	 * delete all share keys of a given file
	 * @param \OC\Files\View $view
	 * @param string $userId owner of the file
	 * @param string $filePath path to the file, relative to the owners file dir
	 */
	public static function delAllShareKeys($view, $userId, $filePath) {

		$filePath = ltrim($filePath, '/');

		if ($view->file_exists('/' . $userId . '/files/' . $filePath)) {
			\OCP\Util::writeLog('Encryption library',
					'File still exists, stop deleting share keys!', \OCP\Util::ERROR);
			return false;
		}

		if ($filePath === '') {
			\OCP\Util::writeLog('Encryption library',
					'Can\'t delete share-keys empty path given!', \OCP\Util::ERROR);
			return false;
		}

		$util = new util($view, $userId);

		if ($util->isSystemWideMountPoint($filePath)) {
			$baseDir = '/files_encryption/share-keys/';
		} else {
			$baseDir = $userId . '/files_encryption/share-keys/';
		}

		$result = true;

		if ($view->is_dir($baseDir . $filePath)) {
			\OCP\Util::writeLog('files_encryption', 'delAllShareKeys: delete share keys: ' . $baseDir . $filePath, \OCP\Util::DEBUG);
			$result = $view->unlink($baseDir . $filePath);
		} else {
			$sharingEnabled = \OCP\Share::isEnabled();
			$users = $util->getSharingUsersArray($sharingEnabled, $filePath);
			foreach($users as $user) {
				$keyName = $baseDir . $filePath . '.' . $user . '.shareKey';
				if ($view->file_exists($keyName)) {
					\OCP\Util::writeLog(
						'files_encryption',
						'dellAllShareKeys: delete share keys: "' . $keyName . '"',
						\OCP\Util::DEBUG
					);
					$result &= $view->unlink($keyName);
				}
			}
		}

		return (bool)$result;
	}

	/**
	 * Delete a single user's shareKey for a single file
	 *
	 * @param \OC\Files\View $view relative to data/
	 * @param array $userIds list of users we want to remove
	 * @param string $filename the owners name of the file for which we want to remove the users relative to data/user/files
	 * @param string $owner owner of the file
	 */
	public static function delShareKey($view, $userIds, $filename, $owner) {

		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		$util = new Util($view, $owner);

		if ($util->isSystemWideMountPoint($filename)) {
			$shareKeyPath = \OC\Files\Filesystem::normalizePath('/files_encryption/share-keys/' . $filename);
		} else {
			$shareKeyPath = \OC\Files\Filesystem::normalizePath('/' . $owner . '/files_encryption/share-keys/' . $filename);
		}

		if ($view->is_dir($shareKeyPath)) {

			self::recursiveDelShareKeys($shareKeyPath, $userIds, $owner, $view);

		} else {

			foreach ($userIds as $userId) {

				if ($userId === $owner && $view->file_exists('/' . $owner . '/files/' . $filename)) {
					\OCP\Util::writeLog('files_encryption', 'Tried to delete owner key, but the file still exists!', \OCP\Util::FATAL);
					continue;
				}
				$result = $view->unlink($shareKeyPath . '.' . $userId . '.shareKey');
				\OCP\Util::writeLog('files_encryption', 'delShareKey: delete share key: ' . $shareKeyPath . '.' . $userId . '.shareKey' , \OCP\Util::DEBUG);
				if (!$result) {
					\OCP\Util::writeLog('Encryption library',
						'Could not delete shareKey; does not exist: "' . $shareKeyPath . '.' . $userId
						. '.shareKey"', \OCP\Util::ERROR);
				}
			}
		}

		\OC_FileProxy::$enabled = $proxyStatus;
	}

	/**
	 * recursively delete share keys from given users
	 *
	 * @param string $dir directory
	 * @param array $userIds user ids for which the share keys should be deleted
	 * @param string $owner owner of the file
	 * @param \OC\Files\View $view view relative to data/
	 */
	private static function recursiveDelShareKeys($dir, $userIds, $owner, $view) {

		$dirContent = $view->opendir($dir);
		$dirSlices = explode('/', ltrim($dir, '/'));
		$realFileDir = '/' . $owner . '/files/' . implode('/', array_slice($dirSlices, 3)) . '/';

		if (is_resource($dirContent)) {
			while (($file = readdir($dirContent)) !== false) {
				if (!\OC\Files\Filesystem::isIgnoredDir($file)) {
					if ($view->is_dir($dir . '/' . $file)) {
						self::recursiveDelShareKeys($dir . '/' . $file, $userIds, $owner, $view);
					} else {
						foreach ($userIds as $userId) {
							$fileNameFromShareKey = self::getFilenameFromShareKey($file, $userId);
							if (!$fileNameFromShareKey) {
								continue;
							}
							$realFile = $realFileDir . $fileNameFromShareKey;

							if ($userId === $owner &&
									$view->file_exists($realFile)) {
								\OCP\Util::writeLog('files_encryption', 'original file still exists, keep owners share key!', \OCP\Util::ERROR);
								continue;
							}
							\OCP\Util::writeLog('files_encryption', 'recursiveDelShareKey: delete share key: ' . $file, \OCP\Util::DEBUG);
							$view->unlink($dir . '/' . $file);
						}
					}
				}
			}
			closedir($dirContent);
		}
	}

	/**
	 * Make preparations to vars and filesystem for saving a keyfile
	 * @param string|boolean $path
	 * @param string $basePath
	 */
	protected static function keySetPreparation(\OC\Files\View $view, $path, $basePath) {

		$targetPath = ltrim($path, '/');

		$path_parts = pathinfo($targetPath);

		// If the file resides within a subdirectory, create it
		if (
			isset($path_parts['dirname'])
			&& !$view->file_exists($basePath . '/' . $path_parts['dirname'])
		) {
			$sub_dirs = explode('/', $basePath . '/' . $path_parts['dirname']);
			$dir = '';
			foreach ($sub_dirs as $sub_dir) {
				$dir .= '/' . $sub_dir;
				if (!$view->is_dir($dir)) {
					$view->mkdir($dir);
				}
			}
		}

		return $targetPath;

	}

	/**
	 * extract filename from share key name
	 * @param string $shareKey (filename.userid.sharekey)
	 * @param string $userId
	 * @return string|false filename or false
	 */
	protected static function getFilenameFromShareKey($shareKey, $userId) {
		$expectedSuffix = '.' . $userId . '.' . 'shareKey';
		$suffixLen = strlen($expectedSuffix);

		$suffix = substr($shareKey, -$suffixLen);

		if ($suffix !== $expectedSuffix) {
			return false;
		}

		return substr($shareKey, 0, -$suffixLen);
	}
}