<?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/>.

/**
 * auth.php - IP authentication plugin.
 *
 * This plugin allows access for only the given IPs.
 *
 * @package    auth
 * @subpackage ip
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @author     Robert Boloc <robert.boloc@urv.cat>
 * @author     Jordi Pujol-Ahulló <jordi.pujol@urv.cat>
 * @copyright 2013 onwards Servei de Recursos Educatius (http://www.sre.urv.cat)
 */

defined('MOODLE_INTERNAL') || die();

global $CFG;

require_once($CFG->dirroot.'/auth/manual/auth.php');

/**
 * Auth plugin to allow login only from restricted IPs.
 */
class auth_plugin_ip extends auth_plugin_manual {

    function __construct() {
        $this->authtype = 'ip';
        $this->config   = get_config('auth_ip');
    }

    /**
     * Tells a login success when the user is logged in correctly and from one of the given IPs.
     * Cannot login when username and password are not correct, or from other IPs than those restricted ones.
     *
     * @param string $username username
     * @param string $password password
     * @return bool
     */
    function user_login($username, $password) {
        global $DB, $CFG;
        if (($user = $DB->get_record('user', array('username'=>$username, 'mnethostid'=>$CFG->mnet_localhost_id)))) {
            // Check if IP is one of the restricted ones.
            $userIp = getremoteaddr();

            if (isset($userIp) && $this->is_ip_valid($userIp)) {
                return validate_internal_user_password($user, $password);
            } else {
                return false;
            }
        }
        // If no valid username, we do not allow to create a new user using this auth type.
        return false;
    }

    /**
     * Determine if the $ip is in the allowed list of IP or CIDR.
     *
     * @see https://secure.php.net/manual/en/ref.network.php#74656
     * @param $ip
     * @return bool
     */
    function is_ip_valid($ip) {
        // List of allowed IP addresses or CIDR ranges
        $valid_ips_or_cidrs = explode(',', str_replace(' ', '', $this->config->valid_ips));

        // Check all the allowed IP or CIDR for matches
        foreach ($valid_ips_or_cidrs as $valid_ip_or_cidr) {
            // If CIDR check if in range
            if ($this->is_cidr($valid_ip_or_cidr)) {
                list ($net, $mask) = explode('/', $valid_ip_or_cidr);

                $ip_net  = ip2long($net);
                $ip_mask = ~((1 << (32 - $mask)) - 1);

                $ip_ip = ip2long($ip);

                $ip_ip_net = $ip_ip & $ip_mask;

                if ($ip_ip_net === $ip_net) {
                    return true;
                }
            // Simple IP compare with equality
            } elseif ($valid_ip_or_cidr === $ip) {
                return true;
            }
        }

        // No match found mark as not allowed
        return false;
    }

    /**
     * Check if a string is a CIDR.
     *
     * @param string $ip_or_cidr
     * @return bool
     */
    function is_cidr($ip_or_cidr) {
        return strpos($ip_or_cidr, '/') > 0;
    }

    /**
     * Returns true if this authentication plugin is 'internal'.
     *
     * @return bool
     */
    function is_internal() {
        return false;
    }

    /**
     * Updates the list of IPs and sends a notification by email.
     *
     * @param object $config configuration settings
     * @return boolean always true.
     */
    function process_config($config) {

        global $CFG;

        // set to defaults if undefined
        if (!isset ($config->valid_ips)) {
            $config->valid_ips = '';
        }

        //saving new configuration settings
        set_config('valid_ips', str_replace(' ', '', $config->valid_ips), 'auth_ip');

        //notify administrator for the settings changed for security.
        mail($CFG->supportemail, get_string('auth_ipmailsubject', 'auth_ip'),
                get_string('auth_ipmailtext', 'auth_ip').' : '.$config->valid_ips);

        return true;
    }
}