<?php
/**
 * Random_* Compatibility Library
 * for using the new PHP 7 random_* API in PHP 5 projects
 *
 * @version 2.0.4
 * @released 2016-11-07
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 - 2016 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('PHP_VERSION_ID')) {
    // This constant was introduced in PHP 5.2.7
    $RandomCompatversion = array_map('intval', explode('.', PHP_VERSION));
    define(
        'PHP_VERSION_ID',
        $RandomCompatversion[0] * 10000
        + $RandomCompatversion[1] * 100
        + $RandomCompatversion[2]
    );
    $RandomCompatversion = null;
}

/**
 * PHP 7.0.0 and newer have these functions natively.
 */
if (PHP_VERSION_ID < 70000) {
    if (!defined('RANDOM_COMPAT_READ_BUFFER')) {
        define('RANDOM_COMPAT_READ_BUFFER', 8);
    }

    $RandomCompatDIR = dirname(__FILE__);

    require_once $RandomCompatDIR.'/byte_safe_strings.php';
    require_once $RandomCompatDIR.'/cast_to_int.php';
    require_once $RandomCompatDIR.'/error_polyfill.php';

    if (!is_callable('random_bytes')) {
        /**
         * PHP 5.2.0 - 5.6.x way to implement random_bytes()
         *
         * We use conditional statements here to define the function in accordance
         * to the operating environment. It's a micro-optimization.
         *
         * In order of preference:
         *   1. Use libsodium if available.
         *   2. fread() /dev/urandom if available (never on Windows)
         *   3. mcrypt_create_iv($bytes, MCRYPT_DEV_URANDOM)
         *   4. COM('CAPICOM.Utilities.1')->GetRandom()
         *   5. openssl_random_pseudo_bytes() (absolute last resort)
         *
         * See RATIONALE.md for our reasoning behind this particular order
         */
        if (extension_loaded('libsodium')) {
            // See random_bytes_libsodium.php
            if (PHP_VERSION_ID >= 50300 && is_callable('\\Sodium\\randombytes_buf')) {
                require_once $RandomCompatDIR.'/random_bytes_libsodium.php';
            } elseif (method_exists('Sodium', 'randombytes_buf')) {
                require_once $RandomCompatDIR.'/random_bytes_libsodium_legacy.php';
            }
        }

        /**
         * Reading directly from /dev/urandom:
         */
        if (DIRECTORY_SEPARATOR === '/') {
            // DIRECTORY_SEPARATOR === '/' on Unix-like OSes -- this is a fast
            // way to exclude Windows.
            $RandomCompatUrandom = true;
            $RandomCompat_basedir = ini_get('open_basedir');

            if (!empty($RandomCompat_basedir)) {
                $RandomCompat_open_basedir = explode(
                    PATH_SEPARATOR,
                    strtolower($RandomCompat_basedir)
                );
                $RandomCompatUrandom = (array() !== array_intersect(
                    array('/dev', '/dev/', '/dev/urandom'),
                    $RandomCompat_open_basedir
                ));
                $RandomCompat_open_basedir = null;
            }

            if (
                !is_callable('random_bytes')
                &&
                $RandomCompatUrandom
                &&
                @is_readable('/dev/urandom')
            ) {
                // Error suppression on is_readable() in case of an open_basedir
                // or safe_mode failure. All we care about is whether or not we
                // can read it at this point. If the PHP environment is going to
                // panic over trying to see if the file can be read in the first
                // place, that is not helpful to us here.

                // See random_bytes_dev_urandom.php
                require_once $RandomCompatDIR.'/random_bytes_dev_urandom.php';
            }
            // Unset variables after use
            $RandomCompat_basedir = null;
        } else {
            $RandomCompatUrandom = false;
        }

        /**
         * mcrypt_create_iv()
         *
         * We only want to use mcypt_create_iv() if:
         *
         * - random_bytes() hasn't already been defined
         * - PHP >= 5.3.7
         * - the mcrypt extensions is loaded
         * - One of these two conditions is true:
         *   - We're on Windows (DIRECTORY_SEPARATOR !== '/')
         *   - We're not on Windows and /dev/urandom is readabale
         *     (i.e. we're not in a chroot jail)
         * - Special case:
         *   - If we're not on Windows, but the PHP version is between
         *     5.6.10 and 5.6.12, we don't want to use mcrypt. It will
         *     hang indefinitely. This is bad.
         */
        if (
            !is_callable('random_bytes')
            &&
            PHP_VERSION_ID >= 50307
            &&
            extension_loaded('mcrypt')
        ) {
            // Prevent this code from hanging indefinitely on non-Windows;
            // see https://bugs.php.net/bug.php?id=69833
            if (
                DIRECTORY_SEPARATOR !== '/' || 
                (PHP_VERSION_ID <= 50609 || PHP_VERSION_ID >= 50613)
            ) {
                // See random_bytes_mcrypt.php
                require_once $RandomCompatDIR.'/random_bytes_mcrypt.php';
            }
        }
        $RandomCompatUrandom = null;

        /**
         * This is a Windows-specific fallback, for when the mcrypt extension
         * isn't loaded.
         */
        if (
            !is_callable('random_bytes')
            &&
            extension_loaded('com_dotnet')
            &&
            class_exists('COM')
        ) {
            $RandomCompat_disabled_classes = preg_split(
                '#\s*,\s*#',
                strtolower(ini_get('disable_classes'))
            );

            if (!in_array('com', $RandomCompat_disabled_classes)) {
                try {
                    $RandomCompatCOMtest = new COM('CAPICOM.Utilities.1');
                    if (method_exists($RandomCompatCOMtest, 'GetRandom')) {
                        // See random_bytes_com_dotnet.php
                        require_once $RandomCompatDIR.'/random_bytes_com_dotnet.php';
                    }
                } catch (com_exception $e) {
                    // Don't try to use it.
                }
            }
            $RandomCompat_disabled_classes = null;
            $RandomCompatCOMtest = null;
        }

        /**
         * throw new Exception
         */
        if (!is_callable('random_bytes')) {
            /**
             * We don't have any more options, so let's throw an exception right now
             * and hope the developer won't let it fail silently.
             */
            function random_bytes($length)
            {
                throw new Exception(
                    'There is no suitable CSPRNG installed on your system'
                );
            }
        }
    }

    if (!is_callable('random_int')) {
        require_once $RandomCompatDIR.'/random_int.php';
    }

    $RandomCompatDIR = null;
}