patchstack / includes / 2fa / polyfill / lib / random_bytes_dev_urandom.php

random_bytes_dev_urandom.php in Patchstack – WordPress & Plugins Security trunk, at includes/2fa/polyfill/lib/random_bytes_dev_urandom.php

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1	<?php
2	/**
3	* Random_* Compatibility Library
4	* for using the new PHP 7 random_* API in PHP 5 projects
5	*
6	* The MIT License (MIT)
7	*
8	* Copyright (c) 2015 - 2018 Paragon Initiative Enterprises
9	*
10	* Permission is hereby granted, free of charge, to any person obtaining a copy
11	* of this software and associated documentation files (the "Software"), to deal
12	* in the Software without restriction, including without limitation the rights
13	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
14	* copies of the Software, and to permit persons to whom the Software is
15	* furnished to do so, subject to the following conditions:
16	*
17	* The above copyright notice and this permission notice shall be included in
18	* all copies or substantial portions of the Software.
19	*
20	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
23	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
24	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
25	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
26	* SOFTWARE.
27	*/
28
29	if (!defined('RANDOM_COMPAT_READ_BUFFER')) {
30	define('RANDOM_COMPAT_READ_BUFFER', 8);
31	}
32
33	if (!is_callable('random_bytes')) {
34	/**
35	* Unless open_basedir is enabled, use /dev/urandom for
36	* random numbers in accordance with best practices
37	*
38	* Why we use /dev/urandom and not /dev/random
39	* @ref https://www.2uo.de/myths-about-urandom
40	* @ref http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers
41	*
42	* @param int $bytes
43	*
44	* @throws Exception
45	*
46	* @return string
47	*/
48	function random_bytes($bytes)
49	{
50	/** @var resource $fp */
51	static $fp = null;
52
53	/**
54	* This block should only be run once
55	*/
56	if (empty($fp)) {
57	/**
58	* We don't want to ever read C:\dev\random, only /dev/urandom on
59	* Unix-like operating systems. While we guard against this
60	* condition in random.php, it doesn't hurt to be defensive in depth
61	* here.
62	*
63	* To that end, we only try to open /dev/urandom if we're on a Unix-
64	* like operating system (which means the directory separator is set
65	* to "/" not "\".
66	*/
67	if (DIRECTORY_SEPARATOR === '/') {
68	if (!is_readable('/dev/urandom')) {
69	throw new Exception(
70	'Environment misconfiguration: ' .
71	'/dev/urandom cannot be read.'
72	);
73	}
74	/**
75	* We use /dev/urandom if it is a char device.
76	* We never fall back to /dev/random
77	*/
78	/** @var resource\|bool $fp */
79	$fp = fopen('/dev/urandom', 'rb');
80	if (is_resource($fp)) {
81	/** @var array<string, int> $st */
82	$st = fstat($fp);
83	if (($st['mode'] & 0170000) !== 020000) {
84	fclose($fp);
85	$fp = false;
86	}
87	}
88	}
89
90	if (is_resource($fp)) {
91	/**
92	* stream_set_read_buffer() does not exist in HHVM
93	*
94	* If we don't set the stream's read buffer to 0, PHP will
95	* internally buffer 8192 bytes, which can waste entropy
96	*
97	* stream_set_read_buffer returns 0 on success
98	*/
99	if (is_callable('stream_set_read_buffer')) {
100	stream_set_read_buffer($fp, RANDOM_COMPAT_READ_BUFFER);
101	}
102	if (is_callable('stream_set_chunk_size')) {
103	stream_set_chunk_size($fp, RANDOM_COMPAT_READ_BUFFER);
104	}
105	}
106	}
107
108	try {
109	/** @var int $bytes */
110	$bytes = RandomCompat_intval($bytes);
111	} catch (TypeError $ex) {
112	throw new TypeError(
113	'random_bytes(): $bytes must be an integer'
114	);
115	}
116
117	if ($bytes < 1) {
118	throw new Error(
119	'Length must be greater than 0'
120	);
121	}
122
123	/**
124	* This if() block only runs if we managed to open a file handle
125	*
126	* It does not belong in an else {} block, because the above
127	* if (empty($fp)) line is logic that should only be run once per
128	* page load.
129	*/
130	if (is_resource($fp)) {
131	/**
132	* @var int
133	*/
134	$remaining = $bytes;
135
136	/**
137	* @var string\|bool
138	*/
139	$buf = '';
140
141	/**
142	* We use fread() in a loop to protect against partial reads
143	*/
144	do {
145	/**
146	* @var string\|bool
147	*/
148	$read = fread($fp, $remaining);
149	if (!is_string($read)) {
150	/**
151	* We cannot safely read from the file. Exit the
152	* do-while loop and trigger the exception condition
153	*
154	* @var string\|bool
155	*/
156	$buf = false;
157	break;
158	}
159	/**
160	* Decrease the number of bytes returned from remaining
161	*/
162	$remaining -= RandomCompat_strlen($read);
163	/**
164	* @var string $buf
165	*/
166	$buf .= $read;
167	} while ($remaining > 0);
168
169	/**
170	* Is our result valid?
171	* @var string\|bool $buf
172	*/
173	if (is_string($buf)) {
174	if (RandomCompat_strlen($buf) === $bytes) {
175	/**
176	* Return our random entropy buffer here:
177	*/
178	return $buf;
179	}
180	}
181	}
182
183	/**
184	* If we reach here, PHP has failed us.
185	*/
186	throw new Exception(
187	'Error reading from source device'
188	);
189	}
190	}
191