1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
<?php
declare(strict_types=1);
/**
* @copyright Copyright (c) 2016, ownCloud, Inc.
*
* @author Andreas Fischer <bantu@owncloud.com>
* @author Christoph Wurst <christoph@winzerhof-wurst.at>
* @author Lukas Reschke <lukas@statuscode.ch>
* @author lynn-stephenson <lynn.stephenson@protonmail.com>
* @author Morris Jobke <hey@morrisjobke.de>
* @author Roeland Jago Douma <roeland@famdouma.nl>
*
* @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 OC\Security;
use Exception;
use OCP\IConfig;
use OCP\Security\ICrypto;
use phpseclib\Crypt\AES;
use phpseclib\Crypt\Hash;
/**
* Class Crypto provides a high-level encryption layer using AES-CBC. If no key has been provided
* it will use the secret defined in config.php as key. Additionally the message will be HMAC'd.
*
* Usage:
* $encryptWithDefaultPassword = \OC::$server->getCrypto()->encrypt('EncryptedText');
* $encryptWithCustompassword = \OC::$server->getCrypto()->encrypt('EncryptedText', 'password');
*
* @package OC\Security
*/
class Crypto implements ICrypto {
private AES $cipher;
private int $ivLength = 16;
public function __construct(
private IConfig $config,
) {
$this->cipher = new AES();
}
/**
* @param string $message The message to authenticate
* @param string $password Password to use (defaults to `secret` in config.php)
* @return string Calculated HMAC
*/
public function calculateHMAC(string $message, string $password = ''): string {
if ($password === '') {
$password = $this->config->getSystemValueString('secret');
}
// Append an "a" behind the password and hash it to prevent reusing the same password as for encryption
$password = hash('sha512', $password . 'a');
$hash = new Hash('sha512');
$hash->setKey($password);
return $hash->hash($message);
}
/**
* Encrypts a value and adds an HMAC (Encrypt-Then-MAC)
*
* @param string $password Password to encrypt, if not specified the secret from config.php will be taken
* @return string Authenticated ciphertext
* @throws Exception if it was not possible to gather sufficient entropy
* @throws Exception if encrypting the data failed
*/
public function encrypt(string $plaintext, string $password = ''): string {
if ($password === '') {
$password = $this->config->getSystemValueString('secret');
}
$keyMaterial = hash_hkdf('sha512', $password);
$this->cipher->setPassword(substr($keyMaterial, 0, 32));
$iv = \random_bytes($this->ivLength);
$this->cipher->setIV($iv);
/** @var string|false $encrypted */
$encrypted = $this->cipher->encrypt($plaintext);
if ($encrypted === false) {
throw new Exception('Encrypting failed.');
}
$ciphertext = bin2hex($encrypted);
$iv = bin2hex($iv);
$hmac = bin2hex($this->calculateHMAC($ciphertext.$iv, substr($keyMaterial, 32)));
return $ciphertext.'|'.$iv.'|'.$hmac.'|3';
}
/**
* Decrypts a value and verifies the HMAC (Encrypt-Then-Mac)
* @param string $password Password to encrypt, if not specified the secret from config.php will be taken
* @throws Exception If the HMAC does not match
* @throws Exception If the decryption failed
*/
public function decrypt(string $authenticatedCiphertext, string $password = ''): string {
$secret = $this->config->getSystemValue('secret');
try {
if ($password === '') {
return $this->decryptWithoutSecret($authenticatedCiphertext, $secret);
}
return $this->decryptWithoutSecret($authenticatedCiphertext, $password);
} catch (Exception $e) {
if ($password === '') {
// Retry with empty secret as a fallback for instances where the secret might not have been set by accident
return $this->decryptWithoutSecret($authenticatedCiphertext, '');
}
throw $e;
}
}
private function decryptWithoutSecret(string $authenticatedCiphertext, string $password = ''): string {
$hmacKey = $encryptionKey = $password;
$parts = explode('|', $authenticatedCiphertext);
$partCount = \count($parts);
if ($partCount < 3 || $partCount > 4) {
throw new Exception('Authenticated ciphertext could not be decoded.');
}
$ciphertext = $this->hex2bin($parts[0]);
$iv = $parts[1];
$hmac = $this->hex2bin($parts[2]);
if ($partCount === 4) {
$version = $parts[3];
if ($version >= '2') {
$iv = $this->hex2bin($iv);
}
if ($version === '3') {
$keyMaterial = hash_hkdf('sha512', $password);
$encryptionKey = substr($keyMaterial, 0, 32);
$hmacKey = substr($keyMaterial, 32);
}
}
$this->cipher->setPassword($encryptionKey);
$this->cipher->setIV($iv);
if (!hash_equals($this->calculateHMAC($parts[0] . $parts[1], $hmacKey), $hmac)) {
throw new Exception('HMAC does not match.');
}
$result = $this->cipher->decrypt($ciphertext);
if ($result === false) {
throw new Exception('Decryption failed');
}
return $result;
}
private function hex2bin(string $hex): string {
if (!ctype_xdigit($hex)) {
throw new \RuntimeException('String contains non hex chars: ' . $hex);
}
if (strlen($hex) % 2 !== 0) {
throw new \RuntimeException('Hex string is not of even length: ' . $hex);
}
$result = hex2bin($hex);
if ($result === false) {
throw new \RuntimeException('Hex to bin conversion failed: ' . $hex);
}
return $result;
}
}
|
