<?php

/**

 * Random_* Compatibility Library 

 * for using the new PHP 7 random_* API in PHP 5 projects

 * 

 * The MIT License (MIT)

 * 

 * Copyright (c) 2015 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 (function_exists('stream_set_read_buffer')) {

                stream_set_read_buffer($fp, RANDOM_COMPAT_READ_BUFFER);

            }

            if (function_exists('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)) {

        $remaining = $bytes;

        $buf = '';

        /**

         * We use fread() in a loop to protect against partial reads

         */

        do {

            $read = fread($fp, $remaining); 

            if ($read === false) {

                /**

                 * We cannot safely read from the file. Exit the

                 * do-while loop and trigger the exception condition

                 */

                $buf = false;

                break;

            }

            /**

             * Decrease the number of bytes returned from remaining

             */

            $remaining -= RandomCompat_strlen($read);

            $buf .= $read;

        } while ($remaining > 0);

        /**

         * Is our result valid?

         */

        if ($buf !== false) {

            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'

    );

}

endif;