lib/sessionlib.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * @package    core
  19  * @subpackage session
  20  * @copyright  1999 onwards Martin Dougiamas  {@link http://moodle.com}
  21  * @copyright  2008, 2009 Petr Skoda  {@link http://skodak.org}
  22  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23  */
  24
  25 defined('MOODLE_INTERNAL') || die();
  26
  27
  28 /**
  29  * Makes sure that $USER->sesskey exists, if $USER itself exists. It sets a new sesskey
  30  * if one does not already exist, but does not overwrite existing sesskeys. Returns the
  31  * sesskey string if $USER exists, or boolean false if not.
  32  *
  33  * @uses $USER
  34  * @return string
  35  */
  36 function sesskey() {
  37     // note: do not use $USER because it may not be initialised yet
  38     if (empty($_SESSION['USER']->sesskey)) {
  39         if (!isset($_SESSION['USER'])) {
  40             // This should never happen,
  41             // do not mess with session and globals here,
  42             // let any checks fail instead!
  43             return false;
  44         }
  45         $_SESSION['USER']->sesskey = random_string(10);
  46     }
  47
  48     return $_SESSION['USER']->sesskey;
  49 }
  50
  51
  52 /**
  53  * Check the sesskey and return true of false for whether it is valid.
  54  * (You might like to imagine this function is called sesskey_is_valid().)
  55  *
  56  * Every script that lets the user perform a significant action (that is,
  57  * changes data in the database) should check the sesskey before doing the action.
  58  * Depending on your code flow, you may want to use the {@link require_sesskey()}
  59  * helper function.
  60  *
  61  * @param string $sesskey The sesskey value to check (optional). Normally leave this blank
  62  *      and this function will do required_param('sesskey', ...).
  63  * @return bool whether the sesskey sent in the request matches the one stored in the session.
  64  */
  65 function confirm_sesskey($sesskey=NULL) {
  66     global $USER;
  67
  68     if (!empty($USER->ignoresesskey)) {
  69         return true;
  70     }
  71
  72     if (empty($sesskey)) {
  73         $sesskey = required_param('sesskey', PARAM_RAW);  // Check script parameters
  74     }
  75
  76     return (sesskey() === $sesskey);
  77 }
  78
  79 /**
  80  * Check the session key using {@link confirm_sesskey()},
  81  * and cause a fatal error if it does not match.
  82  */
  83 function require_sesskey() {
  84     if (!confirm_sesskey()) {
  85         throw new \moodle_exception('invalidsesskey');
  86     }
  87 }
  88
  89 /**
  90  * Determine wether the secure flag should be set on cookies
  91  * @return bool
  92  */
  93 function is_moodle_cookie_secure() {
  94     global $CFG;
  95
  96     if (!isset($CFG->cookiesecure)) {
  97         return false;
  98     }
  99     if (!is_https() and empty($CFG->sslproxy)) {
 100         return false;
 101     }
 102     return !empty($CFG->cookiesecure);
 103 }
 104
 105 /**
 106  * Sets a moodle cookie with a weakly encrypted username
 107  *
 108  * @param string $username to encrypt and place in a cookie, '' means delete current cookie
 109  * @return void
 110  */
 111 function set_moodle_cookie($username) {
 112     global $CFG;
 113
 114     if (NO_MOODLE_COOKIES) {
 115         return;
 116     }
 117
 118     if (empty($CFG->rememberusername)) {
 119         // erase current and do not store permanent cookies
 120         $username = '';
 121     }
 122
 123     if ($username === 'guest') {
 124         // keep previous cookie in case of guest account login
 125         return;
 126     }
 127
 128     $cookiename = 'MOODLEID1_'.$CFG->sessioncookie;
 129
 130     $cookiesecure = is_moodle_cookie_secure();
 131
 132     // Delete old cookie.
 133     setcookie($cookiename, '', time() - HOURSECS, $CFG->sessioncookiepath, $CFG->sessioncookiedomain, $cookiesecure, $CFG->cookiehttponly);
 134
 135     if ($username !== '') {
 136         // Set username cookie for 60 days.
 137         setcookie($cookiename, rc4encrypt($username), time() + (DAYSECS * 60), $CFG->sessioncookiepath, $CFG->sessioncookiedomain, $cookiesecure, $CFG->cookiehttponly);
 138     }
 139 }
 140
 141 /**
 142  * Gets a moodle cookie with a weakly encrypted username
 143  *
 144  * @return string username
 145  */
 146 function get_moodle_cookie() {
 147     global $CFG;
 148
 149     if (NO_MOODLE_COOKIES) {
 150         return '';
 151     }
 152
 153     if (empty($CFG->rememberusername)) {
 154         return '';
 155     }
 156
 157     $cookiename = 'MOODLEID1_'.$CFG->sessioncookie;
 158
 159     if (empty($_COOKIE[$cookiename])) {
 160         return '';
 161     } else {
 162         $username = rc4decrypt($_COOKIE[$cookiename]);
 163         if ($username === 'guest' or $username === 'nobody') {
 164             // backwards compatibility - we do not set these cookies any more
 165             $username = '';
 166         }
 167         return $username;
 168     }
 169 }