Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle is free software: you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

//

// Moodle is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

//

// You should have received a copy of the GNU General Public License

// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

use mod_quiz\local\access_rule_base;

use mod_quiz\quiz_attempt;

use quizaccess_seb\seb_access_manager;

use quizaccess_seb\seb_quiz_settings;

use quizaccess_seb\settings_provider;

use quizaccess_seb\event\access_prevented;

/**

 * Implementation of the quizaccess_seb plugin.

 *

 * @package    quizaccess_seb

 * @author     Andrew Madden <andrewmadden@catalyst-au.net>

 * @author     Dmitrii Metelkin <dmitriim@catalyst-au.net>

 * @copyright  2019 Catalyst IT

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class quizaccess_seb extends access_rule_base {

    /** @var seb_access_manager $accessmanager Instance to manage the access to the quiz for this plugin. */

    private $accessmanager;

    /**

     * Create an instance of this rule for a particular quiz.

     *

     * @param \mod_quiz\quiz_settings $quizobj information about the quiz in question.

     * @param int $timenow the time that should be considered as 'now'.

     * @param seb_access_manager $accessmanager the quiz accessmanager.

     */

    public function __construct(\mod_quiz\quiz_settings $quizobj, int $timenow, seb_access_manager $accessmanager) {

        parent::__construct($quizobj, $timenow);

        $this->accessmanager = $accessmanager;

    }

    /**

     * Return an appropriately configured instance of this rule, if it is applicable

     * to the given quiz, otherwise return null.

     *

     * @param \mod_quiz\quiz_settings $quizobj information about the quiz in question.

     * @param int $timenow the time that should be considered as 'now'.

     * @param bool $canignoretimelimits whether the current user is exempt from

     *      time limits by the mod/quiz:ignoretimelimits capability.

     * @return access_rule_base|null the rule, if applicable, else null.

     */

    public static function make(\mod_quiz\quiz_settings $quizobj, $timenow, $canignoretimelimits) {

        $accessmanager = new seb_access_manager($quizobj);

        // If Safe Exam Browser is not required, this access rule is not applicable.

        if (!$accessmanager->seb_required()) {

            return null;

        }

        return new self($quizobj, $timenow, $accessmanager);

    }

    /**

     * Add any fields that this rule requires to the quiz settings form. This

     * method is called from {@link mod_quiz_mod_form::definition()}, while the

     * security section is being built.

     *

     * @param mod_quiz_mod_form $quizform the quiz settings form that is being built.

     * @param MoodleQuickForm $mform the wrapped MoodleQuickForm.

     */

    public static function add_settings_form_fields(mod_quiz_mod_form $quizform, MoodleQuickForm $mform) {

        settings_provider::add_seb_settings_fields($quizform, $mform);

    }

    /**

     * Validate the data from any form fields added using {@link add_settings_form_fields()}.

     *

     * @param array $errors the errors found so far.

     * @param array $data the submitted form data.

     * @param array $files information about any uploaded files.

     * @param mod_quiz_mod_form $quizform the quiz form object.

     * @return array $errors the updated $errors array.

     */

    public static function validate_settings_form_fields(array $errors,

                                                         array $data, $files, mod_quiz_mod_form $quizform): array {

        $quizid = $data['instance'];

        $cmid = $data['coursemodule'];

        $context = $quizform->get_context();

        if (!settings_provider::can_configure_seb($context)) {

            return $errors;

        }

        if (settings_provider::is_seb_settings_locked($quizid)) {

            return $errors;

        }

        if (settings_provider::is_conflicting_permissions($context)) {

            return $errors;

        }

        $settings = settings_provider::filter_plugin_settings((object) $data);

        // Validate basic settings using persistent class.

        $quizsettings = (new seb_quiz_settings())->from_record($settings);

        // Set non-form fields.

        $quizsettings->set('quizid', $quizid);

        $quizsettings->set('cmid', $cmid);

        $quizsettings->validate();

        // Add any errors to list.

        foreach ($quizsettings->get_errors() as $name => $error) {

            $name = settings_provider::add_prefix($name); // Re-add prefix to match form element.

            $errors[$name] = $error->out();

        }

        // Edge case for filemanager_sebconfig.

        if ($quizsettings->get('requiresafeexambrowser') == settings_provider::USE_SEB_UPLOAD_CONFIG) {

            $errorvalidatefile = settings_provider::validate_draftarea_configfile($data['filemanager_sebconfigfile']);

            if (!empty($errorvalidatefile)) {

                $errors['filemanager_sebconfigfile'] = $errorvalidatefile;

            }

        }

        // Edge case to force user to select a template.

        if ($quizsettings->get('requiresafeexambrowser') == settings_provider::USE_SEB_TEMPLATE) {

            if (empty($data['seb_templateid'])) {

                $errors['seb_templateid'] = get_string('invalidtemplate', 'quizaccess_seb');

            }

        }

        if ($quizsettings->get('requiresafeexambrowser') != settings_provider::USE_SEB_NO) {

            // Global settings may be active which require a quiz password to be set if using SEB.

            if (!empty(get_config('quizaccess_seb', 'quizpasswordrequired')) && empty($data['quizpassword'])) {

                $errors['quizpassword'] = get_string('passwordnotset', 'quizaccess_seb');

            }

        }

        return $errors;

    }

    /**

     * Save any submitted settings when the quiz settings form is submitted. This

     * is called from {@link quiz_after_add_or_update()} in lib.php.

     *

     * @param stdClass $quiz the data from the quiz form, including $quiz->id

     *      which is the id of the quiz being saved.

     */

    public static function save_settings($quiz) {

        $context = context_module::instance($quiz->coursemodule);

        if (!settings_provider::can_configure_seb($context)) {

            return;

        }

        if (settings_provider::is_seb_settings_locked($quiz->id)) {

            return;

        }

        if (settings_provider::is_conflicting_permissions($context)) {

            return;

        }

        $cm = get_coursemodule_from_instance('quiz', $quiz->id, $quiz->course, false, MUST_EXIST);

        $settings = settings_provider::filter_plugin_settings($quiz);

        $settings->quizid = $quiz->id;

        $settings->cmid = $cm->id;

        // Get existing settings or create new settings if none exist.

        $quizsettings = seb_quiz_settings::get_by_quiz_id($quiz->id);

        if (empty($quizsettings)) {

            $quizsettings = new seb_quiz_settings(0, $settings);

        } else {

            $settings->id = $quizsettings->get('id');

            $quizsettings->from_record($settings);

        }

        // Process uploaded files if required.

        if ($quizsettings->get('requiresafeexambrowser') == settings_provider::USE_SEB_UPLOAD_CONFIG) {

            $draftitemid = file_get_submitted_draft_itemid('filemanager_sebconfigfile');

            settings_provider::save_filemanager_sebconfigfile_draftarea($draftitemid, $cm->id);

        } else {

            settings_provider::delete_uploaded_config_file($cm->id);

        }

        // Save or delete settings.

        if ($quizsettings->get('requiresafeexambrowser') != settings_provider::USE_SEB_NO) {

            $quizsettings->save();

        } else if ($quizsettings->get('id')) {

            $quizsettings->delete();

        }

    }

    /**

     * Delete any rule-specific settings when the quiz is deleted. This is called

     * from {@link quiz_delete_instance()} in lib.php.

     *

     * @param stdClass $quiz the data from the database, including $quiz->id

     *      which is the id of the quiz being deleted.

     */

    public static function delete_settings($quiz) {

        $quizsettings = seb_quiz_settings::get_by_quiz_id($quiz->id);

        // Check that there are existing settings.

        if ($quizsettings !== false) {

            $quizsettings->delete();

        }

    }

    /**

     * Return the bits of SQL needed to load all the settings from all the access

     * plugins in one DB query. The easiest way to understand what you need to do

     * here is probably to read the code of {@see \mod_quiz\access_manager::load_settings()}.

     *

     * If you have some settings that cannot be loaded in this way, then you can

     * use the {@link get_extra_settings()} method instead, but that has

     * performance implications.

     *

     * @param int $quizid the id of the quiz we are loading settings for. This

     *     can also be accessed as quiz.id in the SQL. (quiz is a table alisas for {quiz}.)

     * @return array with three elements:

     *     1. fields: any fields to add to the select list. These should be alised

     *        if neccessary so that the field name starts the name of the plugin.

     *     2. joins: any joins (should probably be LEFT JOINS) with other tables that

     *        are needed.

     *     3. params: array of placeholder values that are needed by the SQL. You must

     *        used named placeholders, and the placeholder names should start with the

     *        plugin name, to avoid collisions.

     */

    public static function get_settings_sql($quizid): array {

        return [

                'seb.requiresafeexambrowser AS seb_requiresafeexambrowser, '

                . 'seb.showsebtaskbar AS seb_showsebtaskbar, '

                . 'seb.showwificontrol AS seb_showwificontrol, '

                . 'seb.showreloadbutton AS seb_showreloadbutton, '

                . 'seb.showtime AS seb_showtime, '

                . 'seb.showkeyboardlayout AS seb_showkeyboardlayout, '

                . 'seb.allowuserquitseb AS seb_allowuserquitseb, '

                . 'seb.quitpassword AS seb_quitpassword, '

                . 'seb.linkquitseb AS seb_linkquitseb, '

                . 'seb.userconfirmquit AS seb_userconfirmquit, '

                . 'seb.enableaudiocontrol AS seb_enableaudiocontrol, '

                . 'seb.muteonstartup AS seb_muteonstartup, '

                . 'seb.allowspellchecking AS seb_allowspellchecking, '

                . 'seb.allowreloadinexam AS seb_allowreloadinexam, '

                . 'seb.activateurlfiltering AS seb_activateurlfiltering, '

                . 'seb.filterembeddedcontent AS seb_filterembeddedcontent, '

                . 'seb.expressionsallowed AS seb_expressionsallowed, '

                . 'seb.regexallowed AS seb_regexallowed, '

                . 'seb.expressionsblocked AS seb_expressionsblocked, '

                . 'seb.regexblocked AS seb_regexblocked, '

                . 'seb.allowedbrowserexamkeys AS seb_allowedbrowserexamkeys, '

                . 'seb.showsebdownloadlink AS seb_showsebdownloadlink, '

                . 'sebtemplate.id AS seb_templateid '

                , 'LEFT JOIN {quizaccess_seb_quizsettings} seb ON seb.quizid = quiz.id '

                . 'LEFT JOIN {quizaccess_seb_template} sebtemplate ON seb.templateid = sebtemplate.id '

                , []

        ];

    }

    /**

     * Whether the user should be blocked from starting a new attempt or continuing

     * an attempt now.

     *

     * @return string false if access should be allowed, a message explaining the

     *      reason if access should be prevented.

     */

    public function prevent_access() {

        global $PAGE;

        if (!$this->accessmanager->seb_required()) {

            return false;

        }

        if ($this->accessmanager->can_bypass_seb()) {

            return false;

        }

        // If the rule is active, enforce a secure view whilst taking the quiz.

        $PAGE->set_pagelayout('secure');

        $this->prevent_display_blocks();

        // Access has previously been validated for this session and quiz.

        if ($this->accessmanager->validate_session_access()) {

            return false;

        }

        if (!$this->accessmanager->validate_basic_header()) {

            access_prevented::create_strict($this->accessmanager, $this->get_reason_text('not_seb'))->trigger();

            return $this->get_require_seb_error_message();

        }

        if (!$this->accessmanager->validate_config_key()) {

            if ($this->accessmanager->should_redirect_to_seb_config_link()) {

                $this->accessmanager->redirect_to_seb_config_link();

            }

            access_prevented::create_strict($this->accessmanager, $this->get_reason_text('invalid_config_key'))->trigger();

            return $this->get_invalid_key_error_message();

        }

        if (!$this->accessmanager->validate_browser_exam_key()) {

            access_prevented::create_strict($this->accessmanager, $this->get_reason_text('invalid_browser_key'))->trigger();

            return $this->get_invalid_key_error_message();

        }

        // Set the state of the access for this Moodle session.

        $this->accessmanager->set_session_access(true);

        return false;

    }

    /**

     * Returns a list of finished attempts for the current user.

     *

     * @return array

     */

    private function get_user_finished_attempts(): array {

        global $USER;

        return quiz_get_user_attempts(

            $this->quizobj->get_quizid(),

            $USER->id,

            quiz_attempt::FINISHED,

            false

        );

    }

    /**

     * Prevent block displaying as configured.

     */

    private function prevent_display_blocks() {

        global $PAGE;

        if ($PAGE->has_set_url() && $PAGE->url == $this->quizobj->view_url()) {

            $attempts = $this->get_user_finished_attempts();

            // Don't display blocks before starting an attempt.

            if (empty($attempts) && !get_config('quizaccess_seb', 'displayblocksbeforestart')) {

                $PAGE->blocks->show_only_fake_blocks();

            }

            // Don't display blocks after finishing an attempt.

            if (!empty($attempts) && !get_config('quizaccess_seb', 'displayblockswhenfinished')) {

                $PAGE->blocks->show_only_fake_blocks();

            }

        }

    }

    /**

     * Returns reason for access prevention as a text.

     *

     * @param string $identifier Reason string identifier.

     * @return string

     */

    private function get_reason_text(string $identifier): string {

        if (in_array($identifier, ['not_seb', 'invalid_config_key', 'invalid_browser_key'])) {

            return get_string($identifier, 'quizaccess_seb');

        }

        return get_string('unknown_reason', 'quizaccess_seb');

    }

    /**

     * Return error message when a SEB key is not valid.

     *

     * @return string

     */

    private function get_invalid_key_error_message(): string {

        // Return error message with download link and links to get the seb config.

        return get_string('invalidkeys', 'quizaccess_seb')

            . $this->display_buttons($this->get_action_buttons());

    }

    /**

     * Return error message when a SEB browser is not used.

     *

     * @return string

     */

    private function get_require_seb_error_message(): string {

        $message = get_string('clientrequiresseb', 'quizaccess_seb');

        if ($this->should_display_download_seb_link()) {

            $message .= $this->display_buttons($this->get_download_seb_button());

        }

        // Return error message with download link.

        return $message;

    }

    /**

     * Helper function to display an Exit Safe Exam Browser button if configured to do so and attempts are > 0.

     *

     * @return string empty or a button which has the configured seb quit link.

     */

    private function get_quit_button(): string {

        $quitbutton = '';

        if (empty($this->get_user_finished_attempts())) {

            return $quitbutton;

        }

        // Only display if the link has been configured and attempts are greater than 0.

        if (!empty($this->quiz->seb_linkquitseb)) {

            $quitbutton = html_writer::link(

                $this->quiz->seb_linkquitseb,

                get_string('exitsebbutton', 'quizaccess_seb'),

                ['class' => 'btn btn-secondary']

            );

        }

        return $quitbutton;

    }

    /**

     * Information, such as might be shown on the quiz view page, relating to this restriction.

     * There is no obligation to return anything. If it is not appropriate to tell students

     * about this rule, then just return ''.

     *

     * @return mixed a message, or array of messages, explaining the restriction

     *         (may be '' if no message is appropriate).

     */

    public function description(): array {

        global $PAGE;

        $messages = [get_string('sebrequired', 'quizaccess_seb')];

        // Display download SEB config link for those who can bypass using SEB.

        if ($this->accessmanager->can_bypass_seb() && $this->accessmanager->should_validate_config_key()) {

            $messages[] = $this->display_buttons($this->get_download_config_button());

        }

        // Those with higher level access will be able to see the button if they've made an attempt.

        if (!$this->prevent_access()) {

            $messages[] = $this->display_buttons($this->get_quit_button());

        } else {

            $PAGE->requires->js_call_amd('quizaccess_seb/validate_quiz_access', 'init',

                [$this->quiz->cmid, (bool)get_config('quizaccess_seb', 'autoreconfigureseb')]);

        }

        return $messages;

    }

    /**

     * Sets up the attempt (review or summary) page with any special extra

     * properties required by this rule.

     *

     * @param moodle_page $page the page object to initialise.

     */

    public function setup_attempt_page($page) {

        $page->set_title($this->quizobj->get_course()->shortname . ': ' . $page->title);

        $page->set_popup_notification_allowed(false); // Prevent message notifications.

        $page->set_heading($page->title);

        $page->set_pagelayout('secure');

    }

    /**

     * This is called when the current attempt at the quiz is finished.

     */

    public function current_attempt_finished() {

        $this->accessmanager->clear_session_access();

    }

    /**

     * Prepare buttons HTML code for being displayed on the screen.

     *

     * @param string $buttonshtml Html string of the buttons.

     * @param string $class Optional CSS class (or classes as space-separated list)

     * @param array $attributes Optional other attributes as array

     *

     * @return string HTML code of the provided buttons.

     */

    private function display_buttons(string $buttonshtml, $class = '', array $attributes = null): string {

        $html = '';

        if (!empty($buttonshtml)) {

            $html = html_writer::div($buttonshtml, $class, $attributes);

        }

        return $html;

    }

    /**

     * Get buttons to prompt user to download SEB or config file or launch SEB.

     *

     * @return string Html block of all action buttons.

     */

    private function get_action_buttons(): string {

        $buttons = '';

        if ($this->should_display_download_seb_link()) {

            $buttons .= $this->get_download_seb_button();

        }

        // Get config for displaying links.

        $linkconfig = explode(',', get_config('quizaccess_seb', 'showseblinks'));

        // Display links to download config/launch SEB only if required.

        if ($this->accessmanager->should_validate_config_key()) {

            if (in_array('seb', $linkconfig)) {

                $buttons .= $this->get_launch_seb_button();

            }

            if (in_array('http', $linkconfig)) {

                $buttons .= $this->get_download_config_button();

            }

        }

        return $buttons;

    }

    /**

     * Get a button to download SEB.

     *

     * @return string A link to download SafeExam Browser.

     */

    private function get_download_seb_button(): string {

        global $OUTPUT;

        $button = '';

        if (!empty($this->get_seb_download_url())) {

            $button = $OUTPUT->single_button($this->get_seb_download_url(), get_string('sebdownloadbutton', 'quizaccess_seb'));

        }

        return $button;

    }

    /**

     * Get a button to launch Safe Exam Browser.

     *

     * @return string A link to launch Safe Exam Browser.

     */

    private function get_launch_seb_button(): string {

        // Rendering as a href and not as button in a form to circumvent browser warnings for sending to URL with unknown protocol.

        $seblink = \quizaccess_seb\link_generator::get_link($this->quiz->cmid, true, is_https());

        $buttonlink = html_writer::start_tag('div', ['class' => 'singlebutton']);

        $buttonlink .= html_writer::link($seblink, get_string('seblinkbutton', 'quizaccess_seb'),

            ['class' => 'btn btn-secondary', 'title' => get_string('seblinkbutton', 'quizaccess_seb')]);

        $buttonlink .= html_writer::end_tag('div');

        return $buttonlink;

    }

    /**

     * Get a button to download Safe Exam Browser config.

     *

     * @return string A link to launch Safe Exam Browser.

     */

    private function get_download_config_button(): string {

        // Rendering as a href and not as button in a form to circumvent browser warnings for sending to URL with unknown protocol.

        $httplink = \quizaccess_seb\link_generator::get_link($this->quiz->cmid, false, is_https());

        $buttonlink = html_writer::start_tag('div', ['class' => 'singlebutton']);

        $buttonlink .= html_writer::link($httplink, get_string('httplinkbutton', 'quizaccess_seb'),

            ['class' => 'btn btn-secondary', 'title' => get_string('httplinkbutton', 'quizaccess_seb')]);

        $buttonlink .= html_writer::end_tag('div');

        return $buttonlink;

    }

    /**

     * Returns SEB download URL.

     *

     * @return string

     */

    private function get_seb_download_url(): string {

        return get_config('quizaccess_seb', 'downloadlink');

    }

    /**

     * Check if we should display a link to download Safe Exam Browser.

     *

     * @return bool

     */

    private function should_display_download_seb_link(): bool {

        return !empty($this->quiz->seb_showsebdownloadlink);

    }

}