<?php
/**
* Random_* Compatibility Library
* for using the new PHP 7 random_* API in PHP 5 projects
*
* The MIT License (MIT)
*
* Copyright (c) 2015 - 2018 Paragon Initiative Enterprises
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
if (!defined('RANDOM_COMPAT_READ_BUFFER')) {
define('RANDOM_COMPAT_READ_BUFFER', 8);
}
if (!is_callable('random_bytes')) {
/**
* Unless open_basedir is enabled, use /dev/urandom for
* random numbers in accordance with best practices
*
* Why we use /dev/urandom and not /dev/random
* @ref https://www.2uo.de/myths-about-urandom
* @ref http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers
*
* @param int $bytes
*
* @throws Exception
*
* @return string
*/
function random_bytes($bytes)
{
/** @var resource $fp */
static $fp = null;
/**
* This block should only be run once
*/
if (empty($fp)) {
/**
* We don't want to ever read C:\dev\random, only /dev/urandom on
* Unix-like operating systems. While we guard against this
* condition in random.php, it doesn't hurt to be defensive in depth
* here.
*
* To that end, we only try to open /dev/urandom if we're on a Unix-
* like operating system (which means the directory separator is set
* to "/" not "\".
*/
if (DIRECTORY_SEPARATOR === '/') {
if (!is_readable('/dev/urandom')) {
throw new Exception(
'Environment misconfiguration: ' .
'/dev/urandom cannot be read.'
);
}
/**
* We use /dev/urandom if it is a char device.
* We never fall back to /dev/random
*/
/** @var resource|bool $fp */
$fp = fopen('/dev/urandom', 'rb');
if (is_resource($fp)) {
/** @var array<string, int> $st */
$st = fstat($fp);
if (($st['mode'] & 0170000) !== 020000) {
fclose($fp);
$fp = false;
}
}
}
if (is_resource($fp)) {
/**
* stream_set_read_buffer() does not exist in HHVM
*
* If we don't set the stream's read buffer to 0, PHP will
* internally buffer 8192 bytes, which can waste entropy
*
* stream_set_read_buffer returns 0 on success
*/
if (is_callable('stream_set_read_buffer')) {
stream_set_read_buffer($fp, RANDOM_COMPAT_READ_BUFFER);
}
if (is_callable('stream_set_chunk_size')) {
stream_set_chunk_size($fp, RANDOM_COMPAT_READ_BUFFER);
}
}
}
try {
/** @var int $bytes */
$bytes = RandomCompat_intval($bytes);
} catch (TypeError $ex) {
throw new TypeError(
'random_bytes(): $bytes must be an integer'
);
}
if ($bytes < 1) {
throw new Error(
'Length must be greater than 0'
);
}
/**
* This if() block only runs if we managed to open a file handle
*
* It does not belong in an else {} block, because the above
* if (empty($fp)) line is logic that should only be run once per
* page load.
*/
if (is_resource($fp)) {
/**
* @var int
*/
$remaining = $bytes;
/**
* @var string|bool
*/
$buf = '';
/**
* We use fread() in a loop to protect against partial reads
*/
do {
/**
* @var string|bool
*/
$read = fread($fp, $remaining);
if (!is_string($read)) {
/**
* We cannot safely read from the file. Exit the
* do-while loop and trigger the exception condition
*
* @var string|bool
*/
$buf = false;
break;
}
/**
* Decrease the number of bytes returned from remaining
*/
$remaining -= RandomCompat_strlen($read);
/**
* @var string $buf
*/
$buf .= $read;
} while ($remaining > 0);
/**
* Is our result valid?
* @var string|bool $buf
*/
if (is_string($buf)) {
if (RandomCompat_strlen($buf) === $bytes) {
/**
* Return our random entropy buffer here:
*/
return $buf;
}
}
}
/**
* If we reach here, PHP has failed us.
*/
throw new Exception(
'Error reading from source device'
);
}
}
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