<?php

/**
 * Code related to the option.lib.php interface.
 *
 * PHP version 5
 *
 * @category   Library
 * @package    Sucuri
 * @subpackage SucuriScanner
 * @author     Daniel Cid <dcid@sucuri.net>
 * @copyright  2010-2018 Sucuri Inc.
 * @license    https://www.gnu.org/licenses/gpl-2.0.txt GPL2
 * @link       https://wordpress.org/plugins/sucuri-scanner
 */

if (!defined('SUCURISCAN_INIT') || SUCURISCAN_INIT !== true) {
    if (!headers_sent()) {
        /* Report invalid access if possible. */
        header('HTTP/1.1 403 Forbidden');
    }
    exit(1);
}

/**
 * Plugin options handler.
 *
 * Options are pieces of data that WordPress uses to store various preferences
 * and configuration settings. Listed below are the options, along with some of
 * the default values from the current WordPress install. By using the
 * appropriate function, options can be added, changed, removed, and retrieved,
 * from the wp_options table.
 *
 * The Options API is a simple and standardized way of storing data in the
 * database. The API makes it easy to create, access, update, and delete
 * options. All the data is stored in the wp_options table under a given custom
 * name. This page contains the technical documentation needed to use the
 * Options API. A list of default options can be found in the Option Reference.
 *
 * Note that the _site_ methods are essentially the same as their
 * counterparts. The only differences occur for WP Multisite, when the options
 * apply network-wide and the data is stored in the wp_sitemeta table under the
 * given custom name.
 *
 * @category   Library
 * @package    Sucuri
 * @subpackage SucuriScanner
 * @author     Daniel Cid <dcid@sucuri.net>
 * @copyright  2010-2018 Sucuri Inc.
 * @license    https://www.gnu.org/licenses/gpl-2.0.txt GPL2
 * @link       https://wordpress.org/plugins/sucuri-scanner
 * @see        https://codex.wordpress.org/Option_Reference
 * @see        https://codex.wordpress.org/Options_API
 */
class SucuriScanOption extends SucuriScanRequest
{
    /**
     * Default values for all the plugin's options.
     *
     * @return array Default values for all the plugin's options.
     */
    private static function getDefaultOptionValues()
    {
        $defaults = array(
            'sucuriscan_account' => '',
            'sucuriscan_addr_header' => 'HTTP_X_SUCURI_CLIENTIP',
            'sucuriscan_api_key' => false,
            'sucuriscan_api_protocol' => 'https',
            'sucuriscan_api_service' => 'disabled',
            'sucuriscan_auto_clear_cache' => 'disabled',
            'sucuriscan_checksum_api' => '',
            'sucuriscan_cloudproxy_apikey' => '',
            'sucuriscan_diff_utility' => 'disabled',
            'sucuriscan_dns_lookups' => 'enabled',
            'sucuriscan_email_subject' => '',
            'sucuriscan_emails_per_hour' => 5,
            'sucuriscan_emails_sent' => 0,
            'sucuriscan_ignored_events' => '',
            'sucuriscan_last_email_at' => time(),
            'sucuriscan_lastlogin_redirection' => 'enabled',
            'sucuriscan_maximum_failed_logins' => 30,
            'sucuriscan_notify_available_updates' => 'disabled',
            'sucuriscan_notify_bruteforce_attack' => 'disabled',
            'sucuriscan_notify_failed_login' => 'disabled',
            'sucuriscan_notify_plugin_activated' => 'enabled',
            'sucuriscan_notify_plugin_change' => 'enabled',
            'sucuriscan_notify_plugin_deactivated' => 'disabled',
            'sucuriscan_notify_plugin_deleted' => 'disabled',
            'sucuriscan_notify_plugin_installed' => 'disabled',
            'sucuriscan_notify_plugin_updated' => 'disabled',
            'sucuriscan_notify_post_publication' => 'enabled',
            'sucuriscan_notify_scan_checksums' => 'disabled',
            'sucuriscan_notify_settings_updated' => 'enabled',
            'sucuriscan_notify_success_login' => 'disabled',
            'sucuriscan_notify_theme_activated' => 'enabled',
            'sucuriscan_notify_theme_deleted' => 'disabled',
            'sucuriscan_notify_theme_editor' => 'enabled',
            'sucuriscan_notify_theme_installed' => 'disabled',
            'sucuriscan_notify_theme_updated' => 'disabled',
            'sucuriscan_notify_to' => '',
            'sucuriscan_notify_user_registration' => 'disabled',
            'sucuriscan_notify_website_updated' => 'disabled',
            'sucuriscan_notify_widget_added' => 'disabled',
            'sucuriscan_notify_widget_deleted' => 'disabled',
            'sucuriscan_plugin_version' => '0.0',
            'sucuriscan_prettify_mails' => 'disabled',
            'sucuriscan_revproxy' => 'disabled',
            'sucuriscan_runtime' => 0,
            'sucuriscan_selfhosting_fpath' => '',
            'sucuriscan_selfhosting_monitor' => 'disabled',
            'sucuriscan_site_version' => '0.0',
            'sucuriscan_sitecheck_target' => '',
            'sucuriscan_timezone' => 'UTC+00.00',
            'sucuriscan_use_wpmail' => 'enabled',

            'sucuriscan_headers_cache_control' => 'disabled',
            'sucuriscan_headers_cache_control_options' => array(
                'front_page' => array(
                    'id' => 'front_page',
                    'title' => __('Front Page', 'sucuri-scanner'),
                    'max_age' => 21600,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'posts' => array(
                    'id' => 'posts',
                    'title' => __('Posts', 'sucuri-scanner'),
                    'max_age' => 43200,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => true,
                ),

                'pages' => array(
                    'id' => 'pages',
                    'title' => __('Pages', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'main_index' => array(
                    'id' => 'main_index',
                    'title' => __('Main Index', 'sucuri-scanner'),
                    'max_age' => 21600,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 5,
                    'old_age_multiplier' => 'unavailable',
                ),

                'categories' => array(
                    'id' => 'categories',
                    'title' => __('Categories', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 8,
                    'old_age_multiplier' => 'unavailable',
                ),

                'tags' => array(
                    'id' => 'tags',
                    'title' => __('Tags', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 10,
                    'old_age_multiplier' => 'unavailable',
                ),

                'authors' => array(
                    'id' => 'authors',
                    'title' => __('Authors', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 10,
                    'old_age_multiplier' => 'unavailable',
                ),

                'archives' => array(
                    'id' => 'archives',
                    'title' => __('Archives', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'feeds' => array(
                    'id' => 'feeds',
                    'title' => __('Feeds', 'sucuri-scanner'),
                    'max_age' => 21600,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'attachment_pages' => array(
                    'id' => 'attachment_pages',
                    'title' => __('Attachment Pages', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'search_results' => array(
                    'id' => 'search_results',
                    'title' => __('Search Results', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                '404_not_found' => array(
                    'id' => '404_not_found',
                    'title' => __('404 Not Found', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'redirects' => array(
                    'id' => 'attachment',
                    'title' => __('Redirects', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'woocommerce_products' => array(
                    'id' => 'woocommerce_products',
                    'title' => __('Woocommerce Products', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),

                'woocommerce_categories' => array(
                    'id' => 'woocommerce_categories',
                    'title' => __('Woocommerce Categories', 'sucuri-scanner'),
                    'max_age' => 86400,
                    's_maxage' => 0,
                    'stale_if_error' => 0,
                    'stale_while_revalidate' => 0,
                    'pagination_factor' => 'unavailable',
                    'old_age_multiplier' => 'unavailable',
                ),
            )
        );

        return (array)apply_filters('sucuriscan_option_defaults', $defaults);
    }

    /**
     * Name of all valid plugin's options.
     *
     * @return array Name of all valid plugin's options.
     */
    public static function getDefaultOptionNames()
    {
        $options = self::getDefaultOptionValues();
        $names = array_keys($options);

        return $names;
    }

    /**
     * Retrieve the default values for some specific options.
     *
     * @param string $option List of options, or single option name.
     * @return mixed          The default values for the specified options.
     */
    private static function getDefaultOptions($option = '')
    {
        $default = self::getDefaultOptionValues();

        // Use framework built-in function.
        if (function_exists('get_option')) {
            $admin_email = get_option('admin_email');
            $default['sucuriscan_account'] = $admin_email;
            $default['sucuriscan_notify_to'] = $admin_email;
            $default['sucuriscan_email_subject'] = sprintf(__('Sucuri Alert, %s, %s, %s', 'sucuri-scanner'),
                ':domain', ':event', ':remoteaddr');
        }

        return @$default[$option];
    }

    /**
     * Returns path of the options storage.
     *
     * Returns the absolute path of the file that will store the options
     * associated to the plugin. This must be a PHP file without public access,
     * for which reason it will contain a header with an exit point to prevent
     * malicious people to read the its content. The rest of the file will
     * content a JSON encoded array.
     *
     * @return string File path of the options storage.
     */
    public static function optionsFilePath()
    {
        return self::dataStorePath('sucuri-settings.php');
    }

    /**
     * Returns an array with all the plugin options.
     *
     * NOTE: There is a maximum number of lines for this file, one is for the
     * exit point and the other one is for a single line JSON encoded string.
     * We will discard any other content that exceeds this limit.
     *
     * @return array Array with all the plugin options.
     */
    public static function getAllOptions()
    {
        $options = wp_cache_get('alloptions', SUCURISCAN);

        if ($options && is_array($options)) {
            return $options;
        }

        $options = array();
        $fpath = self::optionsFilePath();

        /* Use this over SucuriScanCache to prevent nested method calls */
        $content = SucuriScanFileInfo::fileContent($fpath);

        if ($content !== false) {
            // Refer to self::optionsFilePath to know why the number two.
            $lines = explode("\n", $content, 2);

            if (count($lines) >= 2) {
                $jsonData = json_decode($lines[1], true);

                if (is_array($jsonData) && !empty($jsonData)) {
                    $options = $jsonData;
                }
            }
        }

        wp_cache_set('alloptions', $options, SUCURISCAN);

        return $options;
    }

    /**
     * Write new options into the external options file.
     *
     * @param array $options Array with plugins options.
     * @return bool           True if the new options were saved, false otherwise.
     */
    public static function writeNewOptions($options = array())
    {
        wp_cache_delete('alloptions', SUCURISCAN);

        $fpath = self::optionsFilePath();
        $content = "<?php exit(0); ?>\n";
        $content .= @json_encode($options) . "\n";

        return (bool)@file_put_contents($fpath, $content);
    }

    /**
     * Returns data from the settings file or the database.
     *
     * To facilitate the development, you can prefix the name of the key in the
     * request (when accessing it) with a single colon, this method will automa-
     * tically replace that character with the unique identifier of the plugin.
     *
     * NOTE: The SucuriScanCache library is a better interface to read the
     * content of a configuration file following the same standard in the other
     * files associated to the plugin. However, this library makes use of this
     * method to retrieve the directory where the files are stored, if we use
     * this library for this specific task we will end up provoking a maximum
     * nesting method call warning.
     *
     * @see https://developer.wordpress.org/reference/functions/get_option/
     *
     * @param string $option Name of the option.
     * @return mixed          Value associated to the option.
     */
    public static function getOption($option = '')
    {
        $options = self::getAllOptions();
        $option = self::varPrefix($option);

        if (array_key_exists($option, $options)) {
            return $options[$option];
        }

        /**
         * Fallback to the default values.
         *
         * If the option is not set in the external options file then we must
         * search in the database for older data, this to provide backward
         * compatibility with older installations of the plugin. If the option
         * is found in the database we must insert it in the external file and
         * delete it from the database before the value is returned to the user.
         *
         * If the option is not in the external file nor in the database, and
         * the name starts with the same prefix used by the plugin then we must
         * return the default value defined by the author.
         *
         * Note that if the plain text file is not writable the method should
         * not delete the option from the database to keep backward compatibility
         * with previous installations of the plugin.
         */
        if (function_exists('get_option')) {
            $value = get_option($option);

            if ($value !== false) {
                if (strpos($option, SUCURISCAN . '_') === 0) {
                    $written = self::updateOption($option, $value);

                    if ($written === true) {
                        delete_option($option);
                    }
                }

                return $value;
            }
        }

        /**
         * Cache default value to stop querying the database.
         *
         * The option was not found in the database either, we will return the
         * data from the array of default values hardcoded in the source code,
         * then will attempt to write the default value into the flat settings
         * file to stop querying the database in subsequent requests.
         */
        if (strpos($option, SUCURISCAN . '_') === 0) {
            $value = self::getDefaultOptions($option);
            self::updateOption($option, $value);
            return $value;
        }

        return false;
    }

    /**
     * Update the value of an database' option.
     *
     * Use the method to update a named option/value pair to the options database
     * table. The option name value is escaped with a special database method before
     * the insert SQL statement but not the option value, this value should always
     * be properly sanitized.
     *
     * @see https://developer.wordpress.org/reference/functions/update_option/
     *
     * @param string $option Name of the option.
     * @param mixed $value New value for the option.
     * @return bool           True if option has been updated, false otherwise.
     */
    public static function updateOption($option = '', $value = '')
    {
        if (strpos($option, ':') === 0 || strpos($option, SUCURISCAN) === 0) {
            $options = self::getAllOptions();
            $option = self::varPrefix($option);
            $options[$option] = $value;

            return self::writeNewOptions($options);
        }

        return update_option($option, $value);
    }

    /**
     * Remove an option from the database.
     *
     * A safe way of removing a named option/value pair from the options database table.
     *
     * @see https://developer.wordpress.org/reference/functions/delete_option/
     *
     * @param string $option Name of the option to be deleted.
     * @return bool           True if option is successfully deleted, false otherwise.
     */
    public static function deleteOption($option = '')
    {
        if (strpos($option, ':') === 0 || strpos($option, SUCURISCAN) === 0) {
            $options = self::getAllOptions();
            $option = self::varPrefix($option);

            // Create/Modify option's value.
            if (array_key_exists($option, $options)) {
                unset($options[$option]);

                return self::writeNewOptions($options);
            }
        }

        return delete_option($option);
    }

    /**
     * Check whether a setting is enabled or not.
     *
     * @param string $option Name of the option to be deleted.
     * @return bool           True if the option is enabled, false otherwise.
     */
    public static function isEnabled($option = '')
    {
        return (bool)(self::getOption($option) === 'enabled');
    }

    /**
     * Check whether a setting is disabled or not.
     *
     * @param string $option Name of the option to be deleted.
     * @return bool           True if the option is disabled, false otherwise.
     */
    public static function isDisabled($option = '')
    {
        return (bool)(self::getOption($option) === 'disabled');
    }

    /**
     * Retrieve all the options stored by Wordpress in the database. The options
     * containing the word "transient" are excluded from the results, this method
     * compatible with multisite instances.
     *
     * @return array All the options stored by Wordpress in the database.
     */
    private static function getSiteOptions()
    {
        $settings = array();

        if (array_key_exists('wpdb', $GLOBALS)) {
            $results = $GLOBALS['wpdb']->get_results(
                'SELECT * FROM ' . $GLOBALS['wpdb']->options . ' WHERE opti'
                . 'on_name NOT LIKE "%_transient_%" ORDER BY option_id ASC'
            );

            foreach ($results as $row) {
                $settings[$row->option_name] = $row->option_value;
            }
        }

        $external = self::getAllOptions();

        foreach ($external as $option => $value) {
            $settings[$option] = $value;
        }

        return $settings;
    }

    /**
     * Check what Wordpress options were changed comparing the values in the database
     * with the values sent through a simple request using a GET or POST method.
     *
     * @param array $request The content of the global variable GET or POST considering SERVER[REQUEST_METHOD].
     * @return array          A list of all the options that were changes through this request.
     */
    public static function whatOptionsWereChanged($request = array())
    {
        $options_changed = array(
            'original' => array(),
            'changed' => array()
        );

        $site_options = self::getSiteOptions();

        foreach ($request as $req_name => $req_value) {
            if (array_key_exists($req_name, $site_options)
                && $site_options[$req_name] != $req_value
            ) {
                $options_changed['original'][$req_name] = $site_options[$req_name];
                $options_changed['changed'][$req_name] = $req_value;
            }
        }

        return $options_changed;
    }

    /**
     * Check the nonce comming from any of the settings pages.
     *
     * @return bool True if the nonce is valid, false otherwise.
     */
    public static function checkOptionsNonce()
    {
        // Create the option_page value if permalink submission.
        if (!isset($_POST['option_page']) && isset($_POST['permalink_structure'])) {
            $_POST['option_page'] = 'permalink';
        }

        /* check if the option_page has an allowed value */
        $option_page = SucuriScanRequest::post('option_page');

        if (!$option_page) {
            return false;
        }

        $action = '';
        $nonce = '_wpnonce';

        switch ($option_page) {
            case 'general':    /* no_break */
            case 'writing':    /* no_break */
            case 'reading':    /* no_break */
            case 'discussion': /* no_break */
            case 'media':      /* no_break */
            case 'options':    /* no_break */
                $action = $option_page . '-options';
                break;
            case 'permalink':
                $action = 'update-permalink';
                break;
        }

        /* check the nonce validity */
        return (bool)(
            !empty($action)
            && isset($_REQUEST[$nonce])
            && wp_verify_nonce($_REQUEST[$nonce], $action)
        );
    }

    /**
     * Returns a list of post-types.
     *
     * The list of post-types includes objects such as Post and Page but also
     * the transitions between each post type, for example, if there are posts
     * of type Draft and they change to Trash, this function will include a new
     * post type called "from_draft_to_trash" and so on.
     *
     * @return array List of post-types with transitions.
     */
    public static function getPostTypes()
    {
        $postTypes = get_post_types();
        $transitions = array(
            'new',
            'publish',
            'pending',
            'draft',
            'auto-draft',
            'future',
            'private',
            'inherit',
            'trash',
        );

        /* include post-type transitions */
        foreach ($transitions as $from) {
            foreach ($transitions as $to) {
                if ($from === $to) {
                    continue;
                }

                $event = sprintf('from_%s_to_%s', $from, $to);

                if (!array_key_exists($event, $postTypes)) {
                    $postTypes[$event] = $event;
                }
            }
        }

        /* include custom non-registered post-types */
        $ignoredEvents = SucuriScanOption::getIgnoredEvents();
        foreach ($ignoredEvents as $event => $time) {
            if (!array_key_exists($event, $postTypes)) {
                $postTypes[$event] = $event;
            }
        }

        return $postTypes;
    }

    /**
     * Check whether an event is being ignored to send alerts or not.
     *
     * @param string $event Unique post-type name.
     * @return bool          Whether an event is being ignored or not.
     */
    public static function isIgnoredEvent($event = '')
    {
        $event = strtolower($event);
        $ignored = self::getIgnoredEvents();

        return array_key_exists($event, $ignored);
    }

    /**
     * Get a list of the post types ignored to receive email alerts when the
     * "new site content" hook is triggered.
     *
     * @return array List of ignored posts-types to send alerts.
     */
    public static function getIgnoredEvents()
    {
        $post_types = self::getOption(':ignored_events');

        if (is_string($post_types)) {
            $post_types = @json_decode($post_types, true);
        }

        return (array)$post_types;
    }

    /**
     * Retrieve a list of basic security keys and check whether their values were
     * randomized correctly.
     *
     * @return array Array with three keys: good, missing, bad.
     */
    public static function getSecurityKeys()
    {
        $response = array(
            'good' => array(),
            'missing' => array(),
            'bad' => array(),
        );
        $key_names = array(
            'AUTH_KEY',
            'AUTH_SALT',
            'LOGGED_IN_KEY',
            'LOGGED_IN_SALT',
            'NONCE_KEY',
            'NONCE_SALT',
            'SECURE_AUTH_KEY',
            'SECURE_AUTH_SALT',
        );

        foreach ($key_names as $key_name) {
            if (defined($key_name)) {
                $key_value = constant($key_name);

                if (stripos($key_value, 'unique phrase') !== false) {
                    $response['bad'][$key_name] = $key_value;
                } else {
                    $response['good'][$key_name] = $key_value;
                }
            } else {
                $response['missing'][$key_name] = false;
            }
        }

        return $response;
    }

    /**
     * Change the reverse proxy setting.
     *
     * When enabled this option forces the plugin to override the value of the
     * global IP address variable from the HTTP header selected by the user from
     * the settings. Note that this may also be automatically enabled when the
     * firewall page is activated as it assumes that the proxy is creating a
     * custom HTTP header for the real IP.
     *
     * @param string $action Enable or disable the reverse proxy.
     * @param bool $silent Hide admin notices on success.
     * @return void
     */
    public static function setRevProxy($action = 'disable', $silent = false)
    {
        if ($action !== 'enable' && $action !== 'disable') {
            return self::deleteOption(':revproxy');
        }

        $action_d = $action . 'd';
        $message = 'Reverse proxy support was <code>' . $action_d . '</code>';

        self::updateOption(':revproxy', $action_d);

        SucuriScanEvent::reportInfoEvent($message);
        SucuriScanEvent::notifyEvent('plugin_change', $message);

        if ($silent) {
            return true;
        }

        return SucuriScanInterface::info(
            sprintf(
                'Reverse proxy support was set to <b>%s</b>',
                $action_d /* either enabled or disabled */
            )
        );
    }

    /**
     * Change the HTTP header to retrieve the real IP address.
     *
     * @param string $header Valid HTTP header name.
     * @param bool $silent Hide admin notices on success.
     * @return void
     */
    public static function setAddrHeader($header = 'REMOTE_ADDR', $silent = false)
    {
        $header = strtoupper($header);
        $allowed = SucuriScan::allowedHttpHeaders(true);

        if (!array_key_exists($header, $allowed)) {
            return SucuriScanInterface::error('HTTP header is not allowed');
        }

        $message = sprintf('HTTP header was set to %s', $header);

        self::updateOption(':addr_header', $header);

        SucuriScanEvent::reportInfoEvent($message);
        SucuriScanEvent::notifyEvent('plugin_change', $message);

        if ($silent) {
            return true;
        }

        return SucuriScanInterface::info(
            sprintf(
                'HTTP header was set to <code>%s</code>',
                $header /* one of the allowed HTTP headers */
            )
        );
    }
}
