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

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<?php
/**
* @author Björn Schießle <schiessle@owncloud.com>
* @author Clark Tomlinson <fallen013@gmail.com>
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* @author Joas Schilling <nickvergessen@owncloud.com>
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* @author Lukas Reschke <lukas@owncloud.com>
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* @author Scrutinizer Auto-Fixer <auto-fixer@scrutinizer-ci.com>
* @author Thomas Müller <thomas.mueller@tmit.eu>
*
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* @copyright Copyright (c) 2016, ownCloud, Inc.
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* @license AGPL-3.0
*
* This code is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program 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, version 3,
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
namespace OCA\Encryption\Crypto;
use OC\Encryption\Exceptions\DecryptionFailedException;
use OC\Encryption\Exceptions\EncryptionFailedException;
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use OCA\Encryption\Exceptions\MultiKeyDecryptException;
use OCA\Encryption\Exceptions\MultiKeyEncryptException;
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use OCP\Encryption\Exceptions\GenericEncryptionException;
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use OCP\IConfig;
use OCP\ILogger;
use OCP\IUserSession;
class Crypt {
const DEFAULT_CIPHER = 'AES-256-CFB';
// default cipher from old ownCloud versions
const LEGACY_CIPHER = 'AES-128-CFB';
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// default key format, old ownCloud version encrypted the private key directly
// with the user password
const LEGACY_KEY_FORMAT = 'password';
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const HEADER_START = 'HBEGIN';
const HEADER_END = 'HEND';
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/**
* @var ILogger
*/
private $logger;
/**
* @var string
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*/
private $user;
/**
* @var IConfig
*/
private $config;
/**
* @var array
*/
private $supportedKeyFormats;
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/**
* @param ILogger $logger
* @param IUserSession $userSession
* @param IConfig $config
*/
public function __construct(ILogger $logger, IUserSession $userSession, IConfig $config) {
$this->logger = $logger;
$this->user = $userSession && $userSession->isLoggedIn() ? $userSession->getUser()->getUID() : '"no user given"';
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$this->config = $config;
$this->supportedKeyFormats = ['hash', 'password'];
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}
/**
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* create new private/public key-pair for user
*
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* @return array|bool
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*/
public function createKeyPair() {
$log = $this->logger;
$res = $this->getOpenSSLPKey();
if (!$res) {
$log->error("Encryption Library couldn't generate users key-pair for {$this->user}",
['app' => 'encryption']);
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if (openssl_error_string()) {
$log->error('Encryption library openssl_pkey_new() fails: ' . openssl_error_string(),
['app' => 'encryption']);
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}
} elseif (openssl_pkey_export($res,
$privateKey,
null,
$this->getOpenSSLConfig())) {
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$keyDetails = openssl_pkey_get_details($res);
$publicKey = $keyDetails['key'];
return [
'publicKey' => $publicKey,
'privateKey' => $privateKey
];
}
$log->error('Encryption library couldn\'t export users private key, please check your servers OpenSSL configuration.' . $this->user,
['app' => 'encryption']);
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if (openssl_error_string()) {
$log->error('Encryption Library:' . openssl_error_string(),
['app' => 'encryption']);
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}
return false;
}
/**
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* Generates a new private key
*
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* @return resource
*/
public function getOpenSSLPKey() {
$config = $this->getOpenSSLConfig();
return openssl_pkey_new($config);
}
/**
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* get openSSL Config
*
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* @return array
*/
private function getOpenSSLConfig() {
$config = ['private_key_bits' => 4096];
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$config = array_merge(
$config,
$this->config->getSystemValue('openssl', [])
);
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return $config;
}
/**
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* @param string $plainContent
* @param string $passPhrase
* @return false|string
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* @throws GenericEncryptionException
*/
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public function symmetricEncryptFileContent($plainContent, $passPhrase) {
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if (!$plainContent) {
$this->logger->error('Encryption Library, symmetrical encryption failed no content given',
['app' => 'encryption']);
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return false;
}
$iv = $this->generateIv();
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$encryptedContent = $this->encrypt($plainContent,
$iv,
$passPhrase,
$this->getCipher());
// combine content to encrypt the IV identifier and actual IV
$catFile = $this->concatIV($encryptedContent, $iv);
$padded = $this->addPadding($catFile);
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return $padded;
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}
/**
* generate header for encrypted file
*
* @param string $keyFormat (can be 'hash' or 'password')
* @return string
* @throws \InvalidArgumentException
*/
public function generateHeader($keyFormat = 'hash') {
if (in_array($keyFormat, $this->supportedKeyFormats, true) === false) {
throw new \InvalidArgumentException('key format "' . $keyFormat . '" is not supported');
}
$cipher = $this->getCipher();
$header = self::HEADER_START
. ':cipher:' . $cipher
. ':keyFormat:' . $keyFormat
. ':' . self::HEADER_END;
return $header;
}
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/**
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* @param string $plainContent
* @param string $iv
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* @param string $passPhrase
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* @param string $cipher
* @return string
* @throws EncryptionFailedException
*/
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private function encrypt($plainContent, $iv, $passPhrase = '', $cipher = self::DEFAULT_CIPHER) {
$encryptedContent = openssl_encrypt($plainContent,
$cipher,
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$passPhrase,
false,
$iv);
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if (!$encryptedContent) {
$error = 'Encryption (symmetric) of content failed';
$this->logger->error($error . openssl_error_string(),
['app' => 'encryption']);
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throw new EncryptionFailedException($error);
}
return $encryptedContent;
}
/**
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* return Cipher either from config.php or the default cipher defined in
* this class
*
* @return string
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*/
public function getCipher() {
$cipher = $this->config->getSystemValue('cipher', self::DEFAULT_CIPHER);
if ($cipher !== 'AES-256-CFB' && $cipher !== 'AES-128-CFB') {
$this->logger->warning('Wrong cipher defined in config.php only AES-128-CFB and AES-256-CFB are supported. Fall back' . self::DEFAULT_CIPHER,
['app' => 'encryption']);
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$cipher = self::DEFAULT_CIPHER;
}
return $cipher;
}
/**
* get key size depending on the cipher
*
* @param string $cipher supported ('AES-256-CFB' and 'AES-128-CFB')
* @return int
* @throws \InvalidArgumentException
*/
protected function getKeySize($cipher) {
if ($cipher === 'AES-256-CFB') {
return 32;
} else if ($cipher === 'AES-128-CFB') {
return 16;
}
throw new \InvalidArgumentException(
'Wrong cipher defined only AES-128-CFB and AES-256-CFB are supported.'
);
}
/**
* get legacy cipher
*
* @return string
*/
public function getLegacyCipher() {
return self::LEGACY_CIPHER;
}
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/**
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* @param string $encryptedContent
* @param string $iv
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* @return string
*/
private function concatIV($encryptedContent, $iv) {
return $encryptedContent . '00iv00' . $iv;
}
/**
* @param string $data
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* @return string
*/
private function addPadding($data) {
return $data . 'xx';
}
/**
* generate password hash used to encrypt the users private key
*
* @param string $password
* @param string $cipher
* @param string $uid only used for user keys
* @return string
*/
protected function generatePasswordHash($password, $cipher, $uid = '') {
$instanceId = $this->config->getSystemValue('instanceid');
$instanceSecret = $this->config->getSystemValue('secret');
$salt = hash('sha256', $uid . $instanceId . $instanceSecret, true);
$keySize = $this->getKeySize($cipher);
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$hash = hash_pbkdf2(
'sha256',
$password,
$salt,
100000,
$keySize,
true
);
return $hash;
}
/**
* encrypt private key
*
* @param string $privateKey
* @param string $password
* @param string $uid for regular users, empty for system keys
* @return false|string
*/
public function encryptPrivateKey($privateKey, $password, $uid = '') {
$cipher = $this->getCipher();
$hash = $this->generatePasswordHash($password, $cipher, $uid);
$encryptedKey = $this->symmetricEncryptFileContent(
$privateKey,
$hash
);
return $encryptedKey;
}
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/**
* @param string $privateKey
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* @param string $password
* @param string $uid for regular users, empty for system keys
* @return false|string
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*/
public function decryptPrivateKey($privateKey, $password = '', $uid = '') {
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$header = $this->parseHeader($privateKey);
if (isset($header['cipher'])) {
$cipher = $header['cipher'];
} else {
$cipher = self::LEGACY_CIPHER;
}
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if (isset($header['keyFormat'])) {
$keyFormat = $header['keyFormat'];
} else {
$keyFormat = self::LEGACY_KEY_FORMAT;
}
if ($keyFormat === 'hash') {
$password = $this->generatePasswordHash($password, $cipher, $uid);
}
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// If we found a header we need to remove it from the key we want to decrypt
if (!empty($header)) {
$privateKey = substr($privateKey,
strpos($privateKey,
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self::HEADER_END) + strlen(self::HEADER_END));
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}
$plainKey = $this->symmetricDecryptFileContent($privateKey,
$password,
$cipher);
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if ($this->isValidPrivateKey($plainKey) === false) {
return false;
}
return $plainKey;
}
/**
* check if it is a valid private key
*
* @param string $plainKey
* @return bool
*/
protected function isValidPrivateKey($plainKey) {
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$res = openssl_get_privatekey($plainKey);
if (is_resource($res)) {
$sslInfo = openssl_pkey_get_details($res);
if (isset($sslInfo['key'])) {
return true;
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}
}
return false;
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}
/**
* @param string $keyFileContents
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* @param string $passPhrase
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* @param string $cipher
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* @return string
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* @throws DecryptionFailedException
*/
public function symmetricDecryptFileContent($keyFileContents, $passPhrase, $cipher = self::DEFAULT_CIPHER) {
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// Remove Padding
$noPadding = $this->removePadding($keyFileContents);
$catFile = $this->splitIv($noPadding);
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return $this->decrypt($catFile['encrypted'],
$catFile['iv'],
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$passPhrase,
$cipher);
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}
/**
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* remove padding
*
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* @param $padded
* @return string|false
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*/
private function removePadding($padded) {
if (substr($padded, -2) === 'xx') {
return substr($padded, 0, -2);
}
return false;
}
/**
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* split iv from encrypted content
*
* @param string|false $catFile
* @return string
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*/
private function splitIv($catFile) {
// Fetch encryption metadata from end of file
$meta = substr($catFile, -22);
// Fetch IV from end of file
$iv = substr($meta, -16);
// Remove IV and IV Identifier text to expose encrypted content
$encrypted = substr($catFile, 0, -22);
return [
'encrypted' => $encrypted,
'iv' => $iv
];
}
/**
* @param string $encryptedContent
* @param string $iv
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* @param string $passPhrase
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* @param string $cipher
* @return string
* @throws DecryptionFailedException
*/
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private function decrypt($encryptedContent, $iv, $passPhrase = '', $cipher = self::DEFAULT_CIPHER) {
$plainContent = openssl_decrypt($encryptedContent,
$cipher,
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$passPhrase,
false,
$iv);
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if ($plainContent) {
return $plainContent;
} else {
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throw new DecryptionFailedException('Encryption library: Decryption (symmetric) of content failed: ' . openssl_error_string());
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}
}
/**
* @param string $data
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* @return array
*/
protected function parseHeader($data) {
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$result = [];
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if (substr($data, 0, strlen(self::HEADER_START)) === self::HEADER_START) {
$endAt = strpos($data, self::HEADER_END);
$header = substr($data, 0, $endAt + strlen(self::HEADER_END));
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// +1 not to start with an ':' which would result in empty element at the beginning
$exploded = explode(':',
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substr($header, strlen(self::HEADER_START) + 1));
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$element = array_shift($exploded);
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while ($element != self::HEADER_END) {
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$result[$element] = array_shift($exploded);
$element = array_shift($exploded);
}
}
return $result;
}
/**
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* generate initialization vector
*
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* @return string
* @throws GenericEncryptionException
*/
private function generateIv() {
$random = openssl_random_pseudo_bytes(12, $strong);
if ($random) {
if (!$strong) {
// If OpenSSL indicates randomness is insecure log error
$this->logger->error('Encryption Library: Insecure symmetric key was generated using openssl_random_psudo_bytes()',
['app' => 'encryption']);
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}
/*
* We encode the iv purely for string manipulation
* purposes -it gets decoded before use
*/
return base64_encode($random);
}
// If we ever get here we've failed anyway no need for an else
throw new GenericEncryptionException('Generating IV Failed');
}
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/**
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* Generate a cryptographically secure pseudo-random base64 encoded 256-bit
* ASCII key, used as file key
*
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* @return string
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* @throws \Exception
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*/
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public function generateFileKey() {
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// Generate key
$key = base64_encode(openssl_random_pseudo_bytes(32, $strong));
if (!$key || !$strong) {
// If OpenSSL indicates randomness is insecure, log error
throw new \Exception('Encryption library, Insecure symmetric key was generated using openssl_random_pseudo_bytes()');
}
return $key;
}
/**
* @param $encKeyFile
* @param $shareKey
* @param $privateKey
* @return string
* @throws MultiKeyDecryptException
*/
public function multiKeyDecrypt($encKeyFile, $shareKey, $privateKey) {
if (!$encKeyFile) {
throw new MultiKeyDecryptException('Cannot multikey decrypt empty plain content');
}
if (openssl_open($encKeyFile, $plainContent, $shareKey, $privateKey)) {
return $plainContent;
} else {
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throw new MultiKeyDecryptException('multikeydecrypt with share key failed:' . openssl_error_string());
}
}
/**
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* @param string $plainContent
* @param array $keyFiles
* @return array
* @throws MultiKeyEncryptException
*/
public function multiKeyEncrypt($plainContent, array $keyFiles) {
// openssl_seal returns false without errors if plaincontent is empty
// so trigger our own error
if (empty($plainContent)) {
throw new MultiKeyEncryptException('Cannot multikeyencrypt empty plain content');
}
// Set empty vars to be set by openssl by reference
$sealed = '';
$shareKeys = [];
$mappedShareKeys = [];
if (openssl_seal($plainContent, $sealed, $shareKeys, $keyFiles)) {
$i = 0;
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// Ensure each shareKey is labelled with its corresponding key id
foreach ($keyFiles as $userId => $publicKey) {
$mappedShareKeys[$userId] = $shareKeys[$i];
$i++;
}
return [
'keys' => $mappedShareKeys,
'data' => $sealed
];
} else {
throw new MultiKeyEncryptException('multikeyencryption failed ' . openssl_error_string());
}
}
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}