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<?php
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/**
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 * Random_* Compatibility Library 
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 * for using the new PHP 7 random_* API in PHP 5 projects
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 * 
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 * The MIT License (MIT)
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 *
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 * Copyright (c) 2015 - 2017 Paragon Initiative Enterprises
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 * 
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 * Permission is hereby granted, free of charge, to any person obtaining a copy
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 * of this software and associated documentation files (the "Software"), to deal
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 * in the Software without restriction, including without limitation the rights
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 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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 * copies of the Software, and to permit persons to whom the Software is
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 * furnished to do so, subject to the following conditions:
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 * 
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 * The above copyright notice and this permission notice shall be included in
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 * all copies or substantial portions of the Software.
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 * 
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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 * SOFTWARE.
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 */
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if (!is_callable('random_bytes')) {
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    /**
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     * If the libsodium PHP extension is loaded, we'll use it above any other
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     * solution.
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     *
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     * libsodium-php project:
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     * @ref https://github.com/jedisct1/libsodium-php
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     *
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     * @param int $bytes
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     *
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     * @throws Exception
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     *
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     * @return string
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     */
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    function random_bytes($bytes)
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    {
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        try {
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            $bytes = RandomCompat_intval($bytes);
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        } catch (TypeError $ex) {
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            throw new TypeError(
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                'random_bytes(): $bytes must be an integer'
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            );
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        }
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        if ($bytes < 1) {
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            throw new Error(
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                'Length must be greater than 0'
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            );
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        }
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        /**
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         * @var string
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         */
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        $buf = '';
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        /**
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         * \Sodium\randombytes_buf() doesn't allow more than 2147483647 bytes to be
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         * generated in one invocation.
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         */
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        if ($bytes > 2147483647) {
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            for ($i = 0; $i < $bytes; $i += 1073741824) {
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                $n = ($bytes - $i) > 1073741824
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                    ? 1073741824
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                    : $bytes - $i;
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                $buf .= Sodium::randombytes_buf((int) $n);
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            }
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        } else {
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            $buf .= Sodium::randombytes_buf((int) $bytes);
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        }
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        if (is_string($buf)) {
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            if (RandomCompat_strlen($buf) === $bytes) {
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                return $buf;
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            }
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        }
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        /**
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         * If we reach here, PHP has failed us.
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         */
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        throw new Exception(
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            'Could not gather sufficient random data'
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        );
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    }
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}
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