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random_bytes_dev_urandom.php (5440B)

---

 <?php
 /**
  * Random_* Compatibility Library 
  * for using the new PHP 7 random_* API in PHP 5 projects
  * 
  * The MIT License (MIT)
  *
  * Copyright (c) 2015 - 2017 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 http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers
      *
      * @param int $bytes
      *
      * @throws Exception
      *
      * @return string
      */
     function random_bytes($bytes)
     {
         static $fp = null;
         /**
          * This block should only be run once
          */
         if (empty($fp)) {
             /**
              * We use /dev/urandom if it is a char device.
              * We never fall back to /dev/random
              */
             $fp = fopen('/dev/urandom', 'rb');
             if (!empty($fp)) {
                 $st = fstat($fp);
                 if (($st['mode'] & 0170000) !== 020000) {
                     fclose($fp);
                     $fp = false;
                 }
             }
 
             if (!empty($fp)) {
                 /**
                  * stream_set_read_buffer() does not exist in HHVM
                  *
                  * If we don't set the stream's read buffer to 0, PHP will
                  * internally buffer 8192 bytes, which can waste entropy
                  *
                  * stream_set_read_buffer returns 0 on success
                  */
                 if (is_callable('stream_set_read_buffer')) {
                     stream_set_read_buffer($fp, RANDOM_COMPAT_READ_BUFFER);
                 }
                 if (is_callable('stream_set_chunk_size')) {
                     stream_set_chunk_size($fp, RANDOM_COMPAT_READ_BUFFER);
                 }
             }
         }
 
         try {
             $bytes = RandomCompat_intval($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($fp)) line is logic that should only be run once per
          * page load.
          */
         if (!empty($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)) {
                     if ($read === false) {
                         /**
                          * 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|bool
                  */
                 $buf = $buf . $read;
             } while ($remaining > 0);
 
             /**
              * Is our result valid?
              */
             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'
         );
     }
 }