1 files changed, 554 insertions, 0 deletions
diff --git a/apps/encryption/lib/Crypto/Encryption.php b/apps/encryption/lib/Crypto/Encryption.php
new file mode 100644
index 00000000000..6d388624e48
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+++ b/apps/encryption/lib/Crypto/Encryption.php
@@ -0,0 +1,554 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+namespace OCA\Encryption\Crypto;
+
+use OC\Encryption\Exceptions\DecryptionFailedException;
+use OC\Files\Cache\Scanner;
+use OC\Files\View;
+use OCA\Encryption\Exceptions\MultiKeyEncryptException;
+use OCA\Encryption\Exceptions\PublicKeyMissingException;
+use OCA\Encryption\KeyManager;
+use OCA\Encryption\Session;
+use OCA\Encryption\Util;
+use OCP\Encryption\IEncryptionModule;
+use OCP\IL10N;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class Encryption implements IEncryptionModule {
+	public const ID = 'OC_DEFAULT_MODULE';
+	public const DISPLAY_NAME = 'Default encryption module';
+
+	/** @var string */
+	private $cipher;
+
+	/** @var string */
+	private $path;
+
+	/** @var string */
+	private $user;
+
+	private array $owner;
+
+	/** @var string */
+	private $fileKey;
+
+	/** @var string */
+	private $writeCache;
+
+	/** @var array */
+	private $accessList;
+
+	/** @var boolean */
+	private $isWriteOperation;
+
+	private bool $useMasterPassword;
+
+	private bool $useLegacyBase64Encoding = false;
+
+	/** @var int Current version of the file */
+	private int $version = 0;
+
+	/** @var array remember encryption signature version */
+	private static $rememberVersion = [];
+
+	public function __construct(
+		private Crypt $crypt,
+		private KeyManager $keyManager,
+		private Util $util,
+		private Session $session,
+		private EncryptAll $encryptAll,
+		private DecryptAll $decryptAll,
+		private LoggerInterface $logger,
+		private IL10N $l,
+	) {
+		$this->owner = [];
+		$this->useMasterPassword = $this->util->isMasterKeyEnabled();
+	}
+
+	/**
+	 * @return string defining the technical unique id
+	 */
+	public function getId() {
+		return self::ID;
+	}
+
+	/**
+	 * In comparison to getKey() this function returns a human readable (maybe translated) name
+	 *
+	 * @return string
+	 */
+	public function getDisplayName() {
+		return self::DISPLAY_NAME;
+	}
+
+	/**
+	 * start receiving chunks from a file. This is the place where you can
+	 * perform some initial step before starting encrypting/decrypting the
+	 * chunks
+	 *
+	 * @param string $path to the file
+	 * @param string $user who read/write the file
+	 * @param string $mode php stream open mode
+	 * @param array $header contains the header data read from the file
+	 * @param array $accessList who has access to the file contains the key 'users' and 'public'
+	 *
+	 * @return array $header contain data as key-value pairs which should be
+	 *               written to the header, in case of a write operation
+	 *               or if no additional data is needed return a empty array
+	 */
+	public function begin($path, $user, $mode, array $header, array $accessList) {
+		$this->path = $this->getPathToRealFile($path);
+		$this->accessList = $accessList;
+		$this->user = $user;
+		$this->isWriteOperation = false;
+		$this->writeCache = '';
+		$this->useLegacyBase64Encoding = true;
+
+
+		if (isset($header['encoding'])) {
+			$this->useLegacyBase64Encoding = $header['encoding'] !== Crypt::BINARY_ENCODING_FORMAT;
+		}
+
+		if ($this->session->isReady() === false) {
+			// if the master key is enabled we can initialize encryption
+			// with a empty password and user name
+			if ($this->util->isMasterKeyEnabled()) {
+				$this->keyManager->init('', '');
+			}
+		}
+
+		/* If useLegacyFileKey is not specified in header, auto-detect, to be safe */
+		$useLegacyFileKey = (($header['useLegacyFileKey'] ?? '') == 'false' ? false : null);
+
+		$this->fileKey = $this->keyManager->getFileKey($this->path, $this->user, $useLegacyFileKey, $this->session->decryptAllModeActivated());
+
+		// always use the version from the original file, also part files
+		// need to have a correct version number if they get moved over to the
+		// final location
+		$this->version = (int)$this->keyManager->getVersion($this->stripPartFileExtension($path), new View());
+
+		if (
+			$mode === 'w'
+			|| $mode === 'w+'
+			|| $mode === 'wb'
+			|| $mode === 'wb+'
+		) {
+			$this->isWriteOperation = true;
+			if (empty($this->fileKey)) {
+				$this->fileKey = $this->crypt->generateFileKey();
+			}
+		} else {
+			// if we read a part file we need to increase the version by 1
+			// because the version number was also increased by writing
+			// the part file
+			if (Scanner::isPartialFile($path)) {
+				$this->version = $this->version + 1;
+			}
+		}
+
+		if ($this->isWriteOperation) {
+			$this->cipher = $this->crypt->getCipher();
+			$this->useLegacyBase64Encoding = $this->crypt->useLegacyBase64Encoding();
+		} elseif (isset($header['cipher'])) {
+			$this->cipher = $header['cipher'];
+		} else {
+			// if we read a file without a header we fall-back to the legacy cipher
+			// which was used in <=oC6
+			$this->cipher = $this->crypt->getLegacyCipher();
+		}
+
+		$result = [
+			'cipher' => $this->cipher,
+			'signed' => 'true',
+			'useLegacyFileKey' => 'false',
+		];
+
+		if ($this->useLegacyBase64Encoding !== true) {
+			$result['encoding'] = Crypt::BINARY_ENCODING_FORMAT;
+		}
+
+		return $result;
+	}
+
+	/**
+	 * last chunk received. This is the place where you can perform some final
+	 * operation and return some remaining data if something is left in your
+	 * buffer.
+	 *
+	 * @param string $path to the file
+	 * @param string $position
+	 * @return string remained data which should be written to the file in case
+	 *                of a write operation
+	 * @throws PublicKeyMissingException
+	 * @throws \Exception
+	 * @throws MultiKeyEncryptException
+	 */
+	public function end($path, $position = '0') {
+		$result = '';
+		if ($this->isWriteOperation) {
+			// in case of a part file we remember the new signature versions
+			// the version will be set later on update.
+			// This way we make sure that other apps listening to the pre-hooks
+			// still get the old version which should be the correct value for them
+			if (Scanner::isPartialFile($path)) {
+				self::$rememberVersion[$this->stripPartFileExtension($path)] = $this->version + 1;
+			}
+			if (!empty($this->writeCache)) {
+				$result = $this->crypt->symmetricEncryptFileContent($this->writeCache, $this->fileKey, $this->version + 1, $position);
+				$this->writeCache = '';
+			}
+			$publicKeys = [];
+			if ($this->useMasterPassword === true) {
+				$publicKeys[$this->keyManager->getMasterKeyId()] = $this->keyManager->getPublicMasterKey();
+			} else {
+				foreach ($this->accessList['users'] as $uid) {
+					try {
+						$publicKeys[$uid] = $this->keyManager->getPublicKey($uid);
+					} catch (PublicKeyMissingException $e) {
+						$this->logger->warning(
+							'no public key found for user "{uid}", user will not be able to read the file',
+							['app' => 'encryption', 'uid' => $uid]
+						);
+						// if the public key of the owner is missing we should fail
+						if ($uid === $this->user) {
+							throw $e;
+						}
+					}
+				}
+			}
+
+			$publicKeys = $this->keyManager->addSystemKeys($this->accessList, $publicKeys, $this->getOwner($path));
+			$shareKeys = $this->crypt->multiKeyEncrypt($this->fileKey, $publicKeys);
+			if (!$this->keyManager->deleteLegacyFileKey($this->path)) {
+				$this->logger->warning(
+					'Failed to delete legacy filekey for {path}',
+					['app' => 'encryption', 'path' => $path]
+				);
+			}
+			foreach ($shareKeys as $uid => $keyFile) {
+				$this->keyManager->setShareKey($this->path, $uid, $keyFile);
+			}
+		}
+		return $result ?: '';
+	}
+
+
+
+	/**
+	 * encrypt data
+	 *
+	 * @param string $data you want to encrypt
+	 * @param int $position
+	 * @return string encrypted data
+	 */
+	public function encrypt($data, $position = 0) {
+		// If extra data is left over from the last round, make sure it
+		// is integrated into the next block
+		if ($this->writeCache) {
+			// Concat writeCache to start of $data
+			$data = $this->writeCache . $data;
+
+			// Clear the write cache, ready for reuse - it has been
+			// flushed and its old contents processed
+			$this->writeCache = '';
+		}
+
+		$encrypted = '';
+		// While there still remains some data to be processed & written
+		while (strlen($data) > 0) {
+			// Remaining length for this iteration, not of the
+			// entire file (may be greater than 8192 bytes)
+			$remainingLength = strlen($data);
+
+			// If data remaining to be written is less than the
+			// size of 1 unencrypted block
+			if ($remainingLength < $this->getUnencryptedBlockSize(true)) {
+				// Set writeCache to contents of $data
+				// The writeCache will be carried over to the
+				// next write round, and added to the start of
+				// $data to ensure that written blocks are
+				// always the correct length. If there is still
+				// data in writeCache after the writing round
+				// has finished, then the data will be written
+				// to disk by $this->flush().
+				$this->writeCache = $data;
+
+				// Clear $data ready for next round
+				$data = '';
+			} else {
+				// Read the chunk from the start of $data
+				$chunk = substr($data, 0, $this->getUnencryptedBlockSize(true));
+
+				$encrypted .= $this->crypt->symmetricEncryptFileContent($chunk, $this->fileKey, $this->version + 1, (string)$position);
+
+				// Remove the chunk we just processed from
+				// $data, leaving only unprocessed data in $data
+				// var, for handling on the next round
+				$data = substr($data, $this->getUnencryptedBlockSize(true));
+			}
+		}
+
+		return $encrypted;
+	}
+
+	/**
+	 * decrypt data
+	 *
+	 * @param string $data you want to decrypt
+	 * @param int|string $position
+	 * @return string decrypted data
+	 * @throws DecryptionFailedException
+	 */
+	public function decrypt($data, $position = 0) {
+		if (empty($this->fileKey)) {
+			$msg = 'Cannot decrypt this file, probably this is a shared file. Please ask the file owner to reshare the file with you.';
+			$hint = $this->l->t('Cannot decrypt this file, probably this is a shared file. Please ask the file owner to reshare the file with you.');
+			$this->logger->error($msg);
+
+			throw new DecryptionFailedException($msg, $hint);
+		}
+
+		return $this->crypt->symmetricDecryptFileContent($data, $this->fileKey, $this->cipher, $this->version, $position, !$this->useLegacyBase64Encoding);
+	}
+
+	/**
+	 * update encrypted file, e.g. give additional users access to the file
+	 *
+	 * @param string $path path to the file which should be updated
+	 * @param string $uid of the user who performs the operation
+	 * @param array $accessList who has access to the file contains the key 'users' and 'public'
+	 * @return bool
+	 */
+	public function update($path, $uid, array $accessList) {
+		if (empty($accessList)) {
+			if (isset(self::$rememberVersion[$path])) {
+				$this->keyManager->setVersion($path, self::$rememberVersion[$path], new View());
+				unset(self::$rememberVersion[$path]);
+			}
+			return false;
+		}
+
+		$fileKey = $this->keyManager->getFileKey($path, $uid, null);
+
+		if (!empty($fileKey)) {
+			$publicKeys = [];
+			if ($this->useMasterPassword === true) {
+				$publicKeys[$this->keyManager->getMasterKeyId()] = $this->keyManager->getPublicMasterKey();
+			} else {
+				foreach ($accessList['users'] as $user) {
+					try {
+						$publicKeys[$user] = $this->keyManager->getPublicKey($user);
+					} catch (PublicKeyMissingException $e) {
+						$this->logger->warning('Could not encrypt file for ' . $user . ': ' . $e->getMessage());
+					}
+				}
+			}
+
+			$publicKeys = $this->keyManager->addSystemKeys($accessList, $publicKeys, $this->getOwner($path));
+
+			$shareKeys = $this->crypt->multiKeyEncrypt($fileKey, $publicKeys);
+
+			$this->keyManager->deleteAllFileKeys($path);
+
+			foreach ($shareKeys as $uid => $keyFile) {
+				$this->keyManager->setShareKey($path, $uid, $keyFile);
+			}
+		} else {
+			$this->logger->debug('no file key found, we assume that the file "{file}" is not encrypted',
+				['file' => $path, 'app' => 'encryption']);
+
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * should the file be encrypted or not
+	 *
+	 * @param string $path
+	 * @return boolean
+	 */
+	public function shouldEncrypt($path) {
+		if ($this->util->shouldEncryptHomeStorage() === false) {
+			$storage = $this->util->getStorage($path);
+			if ($storage && $storage->instanceOfStorage('\OCP\Files\IHomeStorage')) {
+				return false;
+			}
+		}
+		$parts = explode('/', $path);
+		if (count($parts) < 4) {
+			return false;
+		}
+
+		if ($parts[2] === 'files') {
+			return true;
+		}
+		if ($parts[2] === 'files_versions') {
+			return true;
+		}
+		if ($parts[2] === 'files_trashbin') {
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * get size of the unencrypted payload per block.
+	 * Nextcloud read/write files with a block size of 8192 byte
+	 *
+	 * Encrypted blocks have a 22-byte IV and 2 bytes of padding, encrypted and
+	 * signed blocks have also a 71-byte signature and 1 more byte of padding,
+	 * resulting respectively in:
+	 *
+	 *  8192 - 22 - 2 = 8168 bytes in each unsigned unencrypted block
+	 *  8192 - 22 - 2 - 71 - 1 = 8096 bytes in each signed unencrypted block
+	 *
+	 * Legacy base64 encoding then reduces the available size by a 3/4 factor:
+	 *
+	 *  8168 * (3/4) = 6126 bytes in each base64-encoded unsigned unencrypted block
+	 *  8096 * (3/4) = 6072 bytes in each base64-encoded signed unencrypted block
+	 *
+	 * @param bool $signed
+	 * @return int
+	 */
+	public function getUnencryptedBlockSize($signed = false) {
+		if ($this->useLegacyBase64Encoding) {
+			return $signed ? 6072 : 6126;
+		} else {
+			return $signed ? 8096 : 8168;
+		}
+	}
+
+	/**
+	 * check if the encryption module is able to read the file,
+	 * e.g. if all encryption keys exists
+	 *
+	 * @param string $path
+	 * @param string $uid user for whom we want to check if they can read the file
+	 * @return bool
+	 * @throws DecryptionFailedException
+	 */
+	public function isReadable($path, $uid) {
+		$fileKey = $this->keyManager->getFileKey($path, $uid, null);
+		if (empty($fileKey)) {
+			$owner = $this->util->getOwner($path);
+			if ($owner !== $uid) {
+				// if it is a shared file we throw a exception with a useful
+				// error message because in this case it means that the file was
+				// shared with the user at a point where the user didn't had a
+				// valid private/public key
+				$msg = 'Encryption module "' . $this->getDisplayName()
+					. '" is not able to read ' . $path;
+				$hint = $this->l->t('Cannot read this file, probably this is a shared file. Please ask the file owner to reshare the file with you.');
+				$this->logger->warning($msg);
+				throw new DecryptionFailedException($msg, $hint);
+			}
+			return false;
+		}
+
+		return true;
+	}
+
+	/**
+	 * Initial encryption of all files
+	 *
+	 * @param InputInterface $input
+	 * @param OutputInterface $output write some status information to the terminal during encryption
+	 */
+	public function encryptAll(InputInterface $input, OutputInterface $output) {
+		$this->encryptAll->encryptAll($input, $output);
+	}
+
+	/**
+	 * prepare module to perform decrypt all operation
+	 *
+	 * @param InputInterface $input
+	 * @param OutputInterface $output
+	 * @param string $user
+	 * @return bool
+	 */
+	public function prepareDecryptAll(InputInterface $input, OutputInterface $output, $user = '') {
+		return $this->decryptAll->prepare($input, $output, $user);
+	}
+
+
+	/**
+	 * @param string $path
+	 * @return string
+	 */
+	protected function getPathToRealFile($path) {
+		$realPath = $path;
+		$parts = explode('/', $path);
+		if ($parts[2] === 'files_versions') {
+			$realPath = '/' . $parts[1] . '/files/' . implode('/', array_slice($parts, 3));
+			$length = strrpos($realPath, '.');
+			$realPath = substr($realPath, 0, $length);
+		}
+
+		return $realPath;
+	}
+
+	/**
+	 * remove .part file extension and the ocTransferId from the file to get the
+	 * original file name
+	 *
+	 * @param string $path
+	 * @return string
+	 */
+	protected function stripPartFileExtension($path) {
+		if (pathinfo($path, PATHINFO_EXTENSION) === 'part') {
+			$pos = strrpos($path, '.', -6);
+			$path = substr($path, 0, $pos);
+		}
+
+		return $path;
+	}
+
+	/**
+	 * get owner of a file
+	 *
+	 * @param string $path
+	 * @return string
+	 */
+	protected function getOwner($path) {
+		if (!isset($this->owner[$path])) {
+			$this->owner[$path] = $this->util->getOwner($path);
+		}
+		return $this->owner[$path];
+	}
+
+	/**
+	 * Check if the module is ready to be used by that specific user.
+	 * In case a module is not ready - because e.g. key pairs have not been generated
+	 * upon login this method can return false before any operation starts and might
+	 * cause issues during operations.
+	 *
+	 * @param string $user
+	 * @return boolean
+	 * @since 9.1.0
+	 */
+	public function isReadyForUser($user) {
+		if ($this->util->isMasterKeyEnabled()) {
+			return true;
+		}
+		return $this->keyManager->userHasKeys($user);
+	}
+
+	/**
+	 * We only need a detailed access list if the master key is not enabled
+	 *
+	 * @return bool
+	 */
+	public function needDetailedAccessList() {
+		return !$this->util->isMasterKeyEnabled();
+	}
+}