1<?php
2
3namespace dokuwiki\plugin\twofactor;
4
5/**
6 * PHP Class for handling Google Authenticator 2-factor authentication.
7 *
8 * Namespaced for twofactor DokuWiki Plugin
9 *
10 * @author Michael Kliewe
11 * @copyright 2012 Michael Kliewe
12 * @license http://www.opensource.org/licenses/bsd-license.php BSD License
13 *
14 * @link http://www.phpgangsta.de/
15 * @link https://github.com/PHPGangsta/GoogleAuthenticator
16 */
17class GoogleAuthenticator
18{
19    protected $_codeLength = 6;
20
21    /**
22     * Create new secret.
23     * 16 characters, randomly chosen from the allowed base32 characters.
24     *
25     * @param int $secretLength
26     *
27     * @return string
28     * @throws \Exception
29     */
30    public function createSecret($secretLength = 16)
31    {
32        $validChars = $this->_getBase32LookupTable();
33
34        // Valid secret lengths are 80 to 640 bits
35        if ($secretLength < 16 || $secretLength > 128) {
36            throw new \Exception('Bad secret length');
37        }
38        $secret = '';
39        $rnd = false;
40        if (function_exists('random_bytes')) {
41            $rnd = random_bytes($secretLength);
42        } elseif (function_exists('mcrypt_create_iv')) {
43            $rnd = mcrypt_create_iv($secretLength, MCRYPT_DEV_URANDOM);
44        } elseif (function_exists('openssl_random_pseudo_bytes')) {
45            $rnd = openssl_random_pseudo_bytes($secretLength, $cryptoStrong);
46            if (!$cryptoStrong) {
47                $rnd = false;
48            }
49        }
50        if ($rnd !== false) {
51            for ($i = 0; $i < $secretLength; ++$i) {
52                $secret .= $validChars[ord($rnd[$i]) & 31];
53            }
54        } else {
55            throw new \Exception('No source of secure random');
56        }
57
58        return $secret;
59    }
60
61    /**
62     * Calculate the code, with given secret and point in time.
63     *
64     * @param string   $secret
65     * @param int|null $timeSlice
66     *
67     * @return string
68     */
69    public function getCode($secret, $timeSlice = null)
70    {
71        if ($timeSlice === null) {
72            $timeSlice = floor(time() / 30);
73        }
74
75        $secretkey = $this->_base32Decode($secret);
76
77        // Pack time into binary string
78        $time = chr(0).chr(0).chr(0).chr(0).pack('N*', $timeSlice);
79        // Hash it with users secret key
80        $hm = hash_hmac('SHA1', $time, $secretkey, true);
81        // Use last nipple of result as index/offset
82        $offset = ord(substr($hm, -1)) & 0x0F;
83        // grab 4 bytes of the result
84        $hashpart = substr($hm, $offset, 4);
85
86        // Unpak binary value
87        $value = unpack('N', $hashpart);
88        $value = $value[1];
89        // Only 32 bits
90        $value = $value & 0x7FFFFFFF;
91
92        $modulo = pow(10, $this->_codeLength);
93
94        return str_pad($value % $modulo, $this->_codeLength, '0', STR_PAD_LEFT);
95    }
96
97    /**
98     * Get QR-Code URL for image, from google charts.
99     *
100     * @param string $name
101     * @param string $secret
102     * @param string $title
103     * @param array  $params
104     *
105     * @return string
106     */
107    public function getQRCodeGoogleUrl($name, $secret, $title = null, $params = array())
108    {
109        $width = !empty($params['width']) && (int) $params['width'] > 0 ? (int) $params['width'] : 200;
110        $height = !empty($params['height']) && (int) $params['height'] > 0 ? (int) $params['height'] : 200;
111        $level = !empty($params['level']) && array_search($params['level'], array('L', 'M', 'Q', 'H')) !== false ? $params['level'] : 'M';
112
113        $urlencoded = urlencode('otpauth://totp/'.$name.'?secret='.$secret.'');
114        if (isset($title)) {
115            $urlencoded .= urlencode('&issuer='.urlencode($title));
116        }
117
118        return "https://api.qrserver.com/v1/create-qr-code/?data=$urlencoded&size=${width}x${height}&ecc=$level";
119    }
120
121    /**
122     * Check if the code is correct. This will accept codes starting from $discrepancy*30sec ago to $discrepancy*30sec from now.
123     *
124     * @param string   $secret
125     * @param string   $code
126     * @param int      $discrepancy      This is the allowed time drift in 30 second units (8 means 4 minutes before or after)
127     * @param int|null $currentTimeSlice time slice if we want use other that time()
128     *
129     * @return bool
130     */
131    public function verifyCode($secret, $code, $discrepancy = 1, $currentTimeSlice = null)
132    {
133        if ($currentTimeSlice === null) {
134            $currentTimeSlice = floor(time() / 30);
135        }
136
137        if (strlen($code) != 6) {
138            return false;
139        }
140
141        for ($i = -$discrepancy; $i <= $discrepancy; ++$i) {
142            $calculatedCode = $this->getCode($secret, $currentTimeSlice + $i);
143            if ($this->timingSafeEquals($calculatedCode, $code)) {
144                return true;
145            }
146        }
147
148        return false;
149    }
150
151    /**
152     * Set the code length, should be >=6.
153     *
154     * @param int $length
155     *
156     * @return GoogleAuthenticator
157     */
158    public function setCodeLength($length)
159    {
160        $this->_codeLength = $length;
161
162        return $this;
163    }
164
165    /**
166     * Helper class to decode base32.
167     *
168     * @param $secret
169     *
170     * @return bool|string
171     */
172    protected function _base32Decode($secret)
173    {
174        if (empty($secret)) {
175            return '';
176        }
177
178        $base32chars = $this->_getBase32LookupTable();
179        $base32charsFlipped = array_flip($base32chars);
180
181        $paddingCharCount = substr_count($secret, $base32chars[32]);
182        $allowedValues = array(6, 4, 3, 1, 0);
183        if (!in_array($paddingCharCount, $allowedValues)) {
184            return false;
185        }
186        for ($i = 0; $i < 4; ++$i) {
187            if ($paddingCharCount == $allowedValues[$i] &&
188                substr($secret, -($allowedValues[$i])) != str_repeat($base32chars[32], $allowedValues[$i])) {
189                return false;
190            }
191        }
192        $secret = str_replace('=', '', $secret);
193        $secret = str_split($secret);
194        $binaryString = '';
195        for ($i = 0; $i < count($secret); $i = $i + 8) {
196            $x = '';
197            if (!in_array($secret[$i], $base32chars)) {
198                return false;
199            }
200            for ($j = 0; $j < 8; ++$j) {
201                $x .= str_pad(base_convert(@$base32charsFlipped[@$secret[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
202            }
203            $eightBits = str_split($x, 8);
204            for ($z = 0; $z < count($eightBits); ++$z) {
205                $binaryString .= (($y = chr(base_convert($eightBits[$z], 2, 10))) || ord($y) == 48) ? $y : '';
206            }
207        }
208
209        return $binaryString;
210    }
211
212    /**
213     * Get array with all 32 characters for decoding from/encoding to base32.
214     *
215     * @return array
216     */
217    protected function _getBase32LookupTable()
218    {
219        return array(
220            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', //  7
221            'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 15
222            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 23
223            'Y', 'Z', '2', '3', '4', '5', '6', '7', // 31
224            '=',  // padding char
225        );
226    }
227
228    /**
229     * A timing safe equals comparison
230     * more info here: http://blog.ircmaxell.com/2014/11/its-all-about-time.html.
231     *
232     * @param string $safeString The internal (safe) value to be checked
233     * @param string $userString The user submitted (unsafe) value
234     *
235     * @return bool True if the two strings are identical
236     */
237    private function timingSafeEquals($safeString, $userString)
238    {
239        if (function_exists('hash_equals')) {
240            return hash_equals($safeString, $userString);
241        }
242        $safeLen = strlen($safeString);
243        $userLen = strlen($userString);
244
245        if ($userLen != $safeLen) {
246            return false;
247        }
248
249        $result = 0;
250
251        for ($i = 0; $i < $userLen; ++$i) {
252            $result |= (ord($safeString[$i]) ^ ord($userString[$i]));
253        }
254
255        // They are only identical strings if $result is exactly 0...
256        return $result === 0;
257    }
258}
259