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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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/**
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* Class for generating and representing a Safe Exam Browser config key.
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*
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* @package quizaccess_seb
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* @author Andrew Madden <andrewmadden@catalyst-au.net>
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* @copyright 2019 Catalyst IT
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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namespace quizaccess_seb;
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defined('MOODLE_INTERNAL') || die();
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/**
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* Class for generating and representing a Safe Exam Browser config key.
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*
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* @copyright 2020 Catalyst IT
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class config_key {
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/** @var string $hash The Config Key hash. */
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private $hash;
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/**
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* The config_key constructor.
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*
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* @param string $hash The Config Key hash.
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*/
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public function __construct(string $hash) {
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$this->hash = $hash;
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}
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/**
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* Generate the Config Key hash from an SEB Config XML string.
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*
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* See https://safeexambrowser.org/developer/seb-config-key.html for more information about the process.
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*
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* @param string $xml A PList XML string, representing SEB config.
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* @return config_key This config key instance.
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*/
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public static function generate(string $xml): config_key {
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if (!empty($xml) && !helper::is_valid_seb_config($xml)) {
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throw new \invalid_parameter_exception('Invalid a PList XML string, representing SEB config');
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}
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$plist = new property_list($xml);
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// Remove the key "originatorVersion" first. This key is exempted from the SEB-JSON hash (it's a special key
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// which doesn't have any functionality, it's just meta data indicating which SEB version saved the config file).
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$plist->delete_element('originatorVersion');
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// Convert the plist XML of a decrypted/unencrypted SEB config file to a ordered JSON-like "SEB-JSON" object.
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$hash = $plist->to_json();
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// Hash the JSON with SHA256. Defaults to required Base16 encoding.
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$hash = hash('SHA256', $hash);
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return new self($hash);
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}
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/**
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* Get the Config Key hash.
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*
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* @return string The Config Key hash
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*/
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public function get_hash(): string {
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return $this->hash;
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}
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}
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