nextcloud/apps/encryption/lib/crypto/encryption.php

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<?php
/**
* @author Clark Tomlinson <fallen013@gmail.com>
* @since 3/6/15, 2:28 PM
* @link http:/www.clarkt.com
* @copyright Clark Tomlinson © 2015
*
*/
namespace OCA\Encryption\Crypto;
use OCP\Encryption\IEncryptionModule;
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use OCA\Encryption\KeyManager;
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class Encryption implements IEncryptionModule {
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const ID = '42';
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/**
* @var Crypt
*/
private $crypt;
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/** @var string */
private $cipher;
/** @var string */
private $path;
/** @var string */
private $user;
/** @var string */
private $fileKey;
/** @var string */
private $writeCache;
/** @var KeyManager */
private $keymanager;
/** @var array */
private $accessList;
/** @var boolean */
private $isWriteOperation;
public function __construct(Crypt $crypt, KeyManager $keymanager) {
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$this->crypt = $crypt;
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$this->keymanager = $keymanager;
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}
/**
* @return string defining the technical unique id
*/
public function getId() {
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return self::ID;
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}
/**
* In comparison to getKey() this function returns a human readable (maybe translated) name
*
* @return string
*/
public function getDisplayName() {
return 'ownCloud Default Encryption';
}
/**
* 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
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* @param string $user who read/write the file
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* @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 $header contain data as key-value pairs which should be
* written to the header, in case of a write operation
* or if no additional data is needed return a empty array
*/
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public function begin($path, $user, $header, $accessList) {
if (isset($header['cipher'])) {
$this->cipher = $header['cipher'];
} else {
$this->cipher = $this->crypt->getCipher();
}
$this->path = $path;
$this->accessList = $accessList;
$this->user = $user;
$this->writeCache = '';
$this->isWriteOperation = false;
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$this->fileKey = $this->keymanager->getFileKey($path);
return array('cipher' => $this->cipher);
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}
/**
* 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 $path to the file
* @return string remained data which should be written to the file in case
* of a write operation
*/
public function end($path) {
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$result = '';
if ($this->isWriteOperation) {
if (!empty($this->writeCache)) {
$result = $this->crypt->symmetricEncryptFileContent($this->writeCache, $this->fileKey);
$this->writeCache = '';
}
$publicKeys = array();
foreach ($this->accessList['users'] as $user) {
$publicKeys[] = $this->keymanager->getPublicKey($user);
}
$result = $this->crypt->multiKeyEncrypt($this->fileKey, $publicKeys);
}
return $result;
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}
/**
* encrypt data
*
* @param string $data you want to encrypt
* @return mixed encrypted data
*/
public function encrypt($data) {
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$this->isWriteOperation = true;
if (empty($this->fileKey)) {
$this->fileKey = $this->crypt->generateFileKey();
}
// If extra data is left over from the last round, make sure it
// is integrated into the next 6126 / 8192 block
if ($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 < 6126) {
// 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, 6126);
$encrypted .= $this->crypt->symmetricEncryptFileContent($chunk, $this->fileKey);
// Remove the chunk we just processed from
// $data, leaving only unprocessed data in $data
// var, for handling on the next round
$data = substr($data, 6126);
}
}
return $encrypted;
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}
/**
* decrypt data
*
* @param string $data you want to decrypt
* @return mixed decrypted data
*/
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public function decrypt($data) {
$result = '';
if (!empty($data)) {
$result = $this->crypt->symmetricDecryptFileContent($data, $this->fileKey);
}
return $result;
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}
/**
* update encrypted file, e.g. give additional users access to the file
*
* @param string $path path to the file which should be updated
* @param array $accessList who has access to the file contains the key 'users' and 'public'
* @return boolean
*/
public function update($path, $accessList) {
// TODO: Implement update() method.
}
/**
* should the file be encrypted or not
*
* @param string $path
* @return boolean
*/
public function shouldEncrypt($path) {
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return true;
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}
/**
* calculate unencrypted size
*
* @param string $path to file
* @return integer unencrypted size
*/
public function calculateUnencryptedSize($path) {
// TODO: Implement calculateUnencryptedSize() method.
}
/**
* get size of the unencrypted payload per block.
* ownCloud read/write files with a block size of 8192 byte
*
* @return integer
*/
public function getUnencryptedBlockSize() {
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return 6126;
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}
}