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