nextcloud / server

apps/encryption/lib/Crypto/Encryption.php

Indentation +554 added lines, -554 removed lines

@@ -43,558 +43,558 @@
 
 class Encryption implements IEncryptionModule {
 
-	const ID = 'OC_DEFAULT_MODULE';
-	const DISPLAY_NAME = 'Default encryption module';
-
-	/**
-	 * @var Crypt
-	 */
-	private $crypt;
-
-	/** @var string */
-	private $cipher;
-
-	/** @var string */
-	private $path;
-
-	/** @var string */
-	private $user;
-
-	/** @var  string */
-	private $owner;
-
-	/** @var string */
-	private $fileKey;
-
-	/** @var string */
-	private $writeCache;
-
-	/** @var KeyManager */
-	private $keyManager;
-
-	/** @var array */
-	private $accessList;
-
-	/** @var boolean */
-	private $isWriteOperation;
-
-	/** @var Util */
-	private $util;
-
-	/** @var  Session */
-	private $session;
-
-	/** @var  ILogger */
-	private $logger;
-
-	/** @var IL10N */
-	private $l;
-
-	/** @var EncryptAll */
-	private $encryptAll;
-
-	/** @var  bool */
-	private $useMasterPassword;
-
-	/** @var DecryptAll  */
-	private $decryptAll;
-
-	/** @var int unencrypted block size if block contains signature */
-	private $unencryptedBlockSizeSigned = 6072;
-
-	/** @var int unencrypted block size */
-	private $unencryptedBlockSize = 6126;
-
-	/** @var int Current version of the file */
-	private $version = 0;
-
-	/** @var array remember encryption signature version */
-	private static $rememberVersion = [];
-
-
-	/**
-	 *
-	 * @param Crypt $crypt
-	 * @param KeyManager $keyManager
-	 * @param Util $util
-	 * @param Session $session
-	 * @param EncryptAll $encryptAll
-	 * @param DecryptAll $decryptAll
-	 * @param ILogger $logger
-	 * @param IL10N $il10n
-	 */
-	public function __construct(Crypt $crypt,
-								KeyManager $keyManager,
-								Util $util,
-								Session $session,
-								EncryptAll $encryptAll,
-								DecryptAll $decryptAll,
-								ILogger $logger,
-								IL10N $il10n) {
-		$this->crypt = $crypt;
-		$this->keyManager = $keyManager;
-		$this->util = $util;
-		$this->session = $session;
-		$this->encryptAll = $encryptAll;
-		$this->decryptAll = $decryptAll;
-		$this->logger = $logger;
-		$this->l = $il10n;
-		$this->owner = null;
-		$this->useMasterPassword = $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;
-		$this->writeCache = '';
-
-		if($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()) {
-				$this->keyManager->init('', '');
-			}
-		}
-
-		if ($this->session->decryptAllModeActivated()) {
-			$encryptedFileKey = $this->keyManager->getEncryptedFileKey($this->path);
-			$shareKey = $this->keyManager->getShareKey($this->path, $this->session->getDecryptAllUid());
-			$this->fileKey = $this->crypt->multiKeyDecrypt($encryptedFileKey,
-				$shareKey,
-				$this->session->getDecryptAllKey());
-		} else {
-			$this->fileKey = $this->keyManager->getFileKey($this->path, $this->user);
-		}
-
-		// 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 = $this->crypt->getCipher();
-		} elseif (isset($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();
-		}
-
-		return array('cipher' => $this->cipher, 'signed' => 'true');
-	}
-
-	/**
-	 * 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 int $position
-	 * @return string remained data which should be written to the file in case
-	 *                of a write operation
-	 * @throws PublicKeyMissingException
-	 * @throws \Exception
-	 * @throws \OCA\Encryption\Exceptions\MultiKeyEncryptException
-	 */
-	public function end($path, $position = 0) {
-		$result = '';
-		if ($this->isWriteOperation) {
-			$this->keyManager->setVersion($path, $this->version + 1, new View());
-			// in case of a part file we remember the new signature versions
-			// the version will be set later on update.
-			// This way we make sure that other apps listening to the pre-hooks
-			// still get the old version which should be the correct value for them
-			if (Scanner::isPartialFile($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 = '';
-			}
-			$publicKeys = array();
-			if ($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));
-			$encryptedKeyfiles = $this->crypt->multiKeyEncrypt($this->fileKey, $publicKeys);
-			$this->keyManager->setAllFileKeys($this->path, $encryptedKeyfiles);
-		}
-		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 6126 byte block
-			if ($remainingLength < $this->unencryptedBlockSizeSigned) {
-
-				// 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->unencryptedBlockSizeSigned);
-
-				$encrypted .= $this->crypt->symmetricEncryptFileContent($chunk, $this->fileKey, $this->version + 1, $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->unencryptedBlockSizeSigned);
-
-			}
-
-		}
-
-		return $encrypted;
-	}
-
-	/**
-	 * decrypt data
-	 *
-	 * @param string $data you want to decrypt
-	 * @param int $position
-	 * @return string decrypted data
-	 * @throws DecryptionFailedException
-	 */
-	public function decrypt($data, $position = 0) {
-		if (empty($this->fileKey)) {
-			$msg = 'Can not decrypt this file, probably this is a shared file. Please ask the file owner to reshare the file with you.';
-			$hint = $this->l->t('Can not 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);
-	}
-
-	/**
-	 * 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 $accessList who has access to the file contains the key 'users' and 'public'
-	 * @return boolean
-	 */
-	public function update($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;
-		}
-
-		$fileKey = $this->keyManager->getFileKey($path, $uid);
-
-		if (!empty($fileKey)) {
-
-			$publicKeys = array();
-			if ($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));
-
-			$encryptedFileKey = $this->crypt->multiKeyEncrypt($fileKey, $publicKeys);
-
-			$this->keyManager->deleteAllFileKeys($path);
-
-			$this->keyManager->setAllFileKeys($path, $encryptedFileKey);
-
-		} else {
-			$this->logger->debug('no file key found, we assume that the file "{file}" is not encrypted',
-				array('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->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
-	 *
-	 * @param bool $signed
-	 * @return int
-	 */
-	public function getUnencryptedBlockSize($signed = false) {
-		if ($signed === false) {
-			return $this->unencryptedBlockSize;
-		}
-
-		return $this->unencryptedBlockSizeSigned;
-	}
-
-	/**
-	 * check if the encryption module is able to read the file,
-	 * e.g. if all encryption keys exists
-	 *
-	 * @param string $path
-	 * @param string $uid user for whom we want to check if he can read the file
-	 * @return bool
-	 * @throws DecryptionFailedException
-	 */
-	public function isReadable($path, $uid) {
-		$fileKey = $this->keyManager->getFileKey($path, $uid);
-		if (empty($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('Can not 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 ($this->owner === null) {
-			$this->owner = $this->util->getOwner($path);
-		}
-		return $this->owner;
-	}
-
-	/**
-	 * 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) {
-		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();
-	}
+    const ID = 'OC_DEFAULT_MODULE';
+    const DISPLAY_NAME = 'Default encryption module';
+
+    /**
+     * @var Crypt
+     */
+    private $crypt;
+
+    /** @var string */
+    private $cipher;
+
+    /** @var string */
+    private $path;
+
+    /** @var string */
+    private $user;
+
+    /** @var  string */
+    private $owner;
+
+    /** @var string */
+    private $fileKey;
+
+    /** @var string */
+    private $writeCache;
+
+    /** @var KeyManager */
+    private $keyManager;
+
+    /** @var array */
+    private $accessList;
+
+    /** @var boolean */
+    private $isWriteOperation;
+
+    /** @var Util */
+    private $util;
+
+    /** @var  Session */
+    private $session;
+
+    /** @var  ILogger */
+    private $logger;
+
+    /** @var IL10N */
+    private $l;
+
+    /** @var EncryptAll */
+    private $encryptAll;
+
+    /** @var  bool */
+    private $useMasterPassword;
+
+    /** @var DecryptAll  */
+    private $decryptAll;
+
+    /** @var int unencrypted block size if block contains signature */
+    private $unencryptedBlockSizeSigned = 6072;
+
+    /** @var int unencrypted block size */
+    private $unencryptedBlockSize = 6126;
+
+    /** @var int Current version of the file */
+    private $version = 0;
+
+    /** @var array remember encryption signature version */
+    private static $rememberVersion = [];
+
+
+    /**
+     *
+     * @param Crypt $crypt
+     * @param KeyManager $keyManager
+     * @param Util $util
+     * @param Session $session
+     * @param EncryptAll $encryptAll
+     * @param DecryptAll $decryptAll
+     * @param ILogger $logger
+     * @param IL10N $il10n
+     */
+    public function __construct(Crypt $crypt,
+                                KeyManager $keyManager,
+                                Util $util,
+                                Session $session,
+                                EncryptAll $encryptAll,
+                                DecryptAll $decryptAll,
+                                ILogger $logger,
+                                IL10N $il10n) {
+        $this->crypt = $crypt;
+        $this->keyManager = $keyManager;
+        $this->util = $util;
+        $this->session = $session;
+        $this->encryptAll = $encryptAll;
+        $this->decryptAll = $decryptAll;
+        $this->logger = $logger;
+        $this->l = $il10n;
+        $this->owner = null;
+        $this->useMasterPassword = $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;
+        $this->writeCache = '';
+
+        if($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()) {
+                $this->keyManager->init('', '');
+            }
+        }
+
+        if ($this->session->decryptAllModeActivated()) {
+            $encryptedFileKey = $this->keyManager->getEncryptedFileKey($this->path);
+            $shareKey = $this->keyManager->getShareKey($this->path, $this->session->getDecryptAllUid());
+            $this->fileKey = $this->crypt->multiKeyDecrypt($encryptedFileKey,
+                $shareKey,
+                $this->session->getDecryptAllKey());
+        } else {
+            $this->fileKey = $this->keyManager->getFileKey($this->path, $this->user);
+        }
+
+        // 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 = $this->crypt->getCipher();
+        } elseif (isset($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();
+        }
+
+        return array('cipher' => $this->cipher, 'signed' => 'true');
+    }
+
+    /**
+     * 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 int $position
+     * @return string remained data which should be written to the file in case
+     *                of a write operation
+     * @throws PublicKeyMissingException
+     * @throws \Exception
+     * @throws \OCA\Encryption\Exceptions\MultiKeyEncryptException
+     */
+    public function end($path, $position = 0) {
+        $result = '';
+        if ($this->isWriteOperation) {
+            $this->keyManager->setVersion($path, $this->version + 1, new View());
+            // in case of a part file we remember the new signature versions
+            // the version will be set later on update.
+            // This way we make sure that other apps listening to the pre-hooks
+            // still get the old version which should be the correct value for them
+            if (Scanner::isPartialFile($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 = '';
+            }
+            $publicKeys = array();
+            if ($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));
+            $encryptedKeyfiles = $this->crypt->multiKeyEncrypt($this->fileKey, $publicKeys);
+            $this->keyManager->setAllFileKeys($this->path, $encryptedKeyfiles);
+        }
+        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 6126 byte block
+            if ($remainingLength < $this->unencryptedBlockSizeSigned) {
+
+                // 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->unencryptedBlockSizeSigned);
+
+                $encrypted .= $this->crypt->symmetricEncryptFileContent($chunk, $this->fileKey, $this->version + 1, $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->unencryptedBlockSizeSigned);
+
+            }
+
+        }
+
+        return $encrypted;
+    }
+
+    /**
+     * decrypt data
+     *
+     * @param string $data you want to decrypt
+     * @param int $position
+     * @return string decrypted data
+     * @throws DecryptionFailedException
+     */
+    public function decrypt($data, $position = 0) {
+        if (empty($this->fileKey)) {
+            $msg = 'Can not decrypt this file, probably this is a shared file. Please ask the file owner to reshare the file with you.';
+            $hint = $this->l->t('Can not 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);
+    }
+
+    /**
+     * 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 $accessList who has access to the file contains the key 'users' and 'public'
+     * @return boolean
+     */
+    public function update($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;
+        }
+
+        $fileKey = $this->keyManager->getFileKey($path, $uid);
+
+        if (!empty($fileKey)) {
+
+            $publicKeys = array();
+            if ($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));
+
+            $encryptedFileKey = $this->crypt->multiKeyEncrypt($fileKey, $publicKeys);
+
+            $this->keyManager->deleteAllFileKeys($path);
+
+            $this->keyManager->setAllFileKeys($path, $encryptedFileKey);
+
+        } else {
+            $this->logger->debug('no file key found, we assume that the file "{file}" is not encrypted',
+                array('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->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
+     *
+     * @param bool $signed
+     * @return int
+     */
+    public function getUnencryptedBlockSize($signed = false) {
+        if ($signed === false) {
+            return $this->unencryptedBlockSize;
+        }
+
+        return $this->unencryptedBlockSizeSigned;
+    }
+
+    /**
+     * check if the encryption module is able to read the file,
+     * e.g. if all encryption keys exists
+     *
+     * @param string $path
+     * @param string $uid user for whom we want to check if he can read the file
+     * @return bool
+     * @throws DecryptionFailedException
+     */
+    public function isReadable($path, $uid) {
+        $fileKey = $this->keyManager->getFileKey($path, $uid);
+        if (empty($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('Can not 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 ($this->owner === null) {
+            $this->owner = $this->util->getOwner($path);
+        }
+        return $this->owner;
+    }
+
+    /**
+     * 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) {
+        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();
+    }
 }