Subversion Repositories php_clientchallenge

<?php

/*

 * php_clientchallenge

 * Copyright 2021-2022 Daniel Marschall, ViaThinkSoft

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

namespace ViaThinkSoft\RateLimitingChallenge;

class ClientChallenge {

        private static function tryDownloadPhpSha3() {

                // Download file if required (usually composer should do it)

                if (file_exists(__DIR__.'/Sha3.php')) include_once __DIR__.'/Sha3.php';

                if (!class_exists('\bb\Sha3\Sha3')) {

                        $sha3_lib = file_get_contents('https://raw.githubusercontent.com/danielmarschall/php-sha3/master/src/Sha3.php');

                        if (@file_put_contents(__DIR__.'/Sha3.php', $sha3_lib)) {

                                include_once __DIR__.'/Sha3.php';

                        } else {

                                eval('?>'.$sha3_lib);

                        }

                }

        }

        private static function sha3_512($message, $raw_output=false) {

                if (version_compare(PHP_VERSION, '7.1.0') >= 0) {

                        return hash('sha3-512', $message, $raw_output);

                } else {

                        self::tryDownloadPhpSha3();

                        return \bb\Sha3\Sha3::hash($message, 512, $raw_output);

                }

        }

        private static function sha3_512_hmac($message, $key, $raw_output=false) {

                // RFC 2104 HMAC

                if (version_compare(PHP_VERSION, '7.1.0') >= 0) {

                        return hash_hmac('sha3-512', $message, $key, $raw_output);

                } else {

                        self::tryDownloadPhpSha3();

                        return \bb\Sha3\Sha3::hash_hmac($message, $key, 512, $raw_output);

                }

        }

        private static function getOpenTransFileName($ip_target, $random, $server_secret) {

                $dir = defined('VTS_CS_OPEN_TRANS_DIR') ? VTS_CS_OPEN_TRANS_DIR : __DIR__.'/cache';

                if ($dir == '') $dir = '.'; /** @phpstan-ignore-line */

                // First, delete challenges which were never completed

                $files = glob($dir.'/vts_client_challenge_*.tmp');

                $expire = strtotime('-3 DAYS');

                foreach ($files as $file) {

                        if (!is_file($file)) continue;

                        if (filemtime($file) > $expire) continue;

                        @unlink($file);

                }

                return $dir.'/vts_client_challenge_'.self::sha3_512_hmac($ip_target.'/'.$random, $server_secret).'.tmp';

        }

        public static function checkValidation($client_response, $max_time=10, $server_secret) {

                if (!is_array($client_response)) throw new \Exception('Challenge response is invalid');

                if (count($client_response) != 5) throw new \Exception('Challenge response is invalid');

                list($starttime, $ip_target, $challenge, $answer, $challenge_integrity) = $client_response;

                if (!is_numeric($starttime)) throw new \Exception('Challenge response is invalid');

                if (!is_string($ip_target)) throw new \Exception('Challenge response is invalid');

                if (!is_string($challenge)) throw new \Exception('Challenge response is invalid');

                if (!is_numeric($answer)) throw new \Exception('Challenge response is invalid');

                if (!is_string($challenge_integrity)) throw new \Exception('Challenge response is invalid');

                $open_trans_file = self::getOpenTransFileName($ip_target, $answer, $server_secret);

                $current_ip = (isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : 'unknown');

                if ($ip_target != $current_ip) {

                        throw new \Exception("IP address has changed. Please try again. (current IP $current_ip, expected $ip_target)");

                } else if (time()-$starttime > $max_time) {

                        throw new \Exception('Challenge expired. Please try again.');

                } else if ($challenge_integrity != self::sha3_512_hmac($challenge,$server_secret)) {

                        throw new \Exception('Challenge integrity failed');

                } else if ($challenge !== self::sha3_512($starttime.'/'.$ip_target.'/'.$answer)) {

                        throw new \Exception('Wrong answer');

                } else if (!file_exists($open_trans_file)) {

                        throw new \Exception('Challenge submitted twice or transaction missing');

                } else {

                        @unlink($open_trans_file);

                        return true;

                }

        }

        public static function createChallenge($complexity=50000, $server_secret) {

                $offset = 0; // doesn't matter

                $min = $offset;

                $max = $offset + $complexity;

                $starttime = time();

                $random = rand($min,$max); // TODO: cryptographic rand

                $ip_target = $_SERVER['REMOTE_ADDR'];

                $challenge = self::sha3_512($starttime.'/'.$ip_target.'/'.$random);

                $challenge_integrity = self::sha3_512_hmac($challenge,$server_secret);

                $send_to_client = array($starttime, $ip_target, $challenge, $min, $max, $challenge_integrity);

                $open_trans_file = self::getOpenTransFileName($ip_target, $random, $server_secret);

                if (@file_put_contents($open_trans_file, '') === false) {

                        throw new \Exception("Cannot write $open_trans_file");

                }

                return $send_to_client;

        }

}