/lib/classes/session/database.php
PHP | 303 lines | 144 code | 32 blank | 127 comment | 22 complexity | 17c9b339c37f82da298557cfeb7b2d44 MD5 | raw file
- <?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/>.
- /**
- * Database based session handler.
- *
- * @package core
- * @copyright 2013 Petr Skoda {@link http://skodak.org}
- * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
- namespace core\session;
- defined('MOODLE_INTERNAL') || die();
- /**
- * Database based session handler.
- *
- * @package core
- * @copyright 2013 Petr Skoda {@link http://skodak.org}
- * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
- class database extends handler {
- /** @var \stdClass $record session record */
- protected $recordid = null;
- /** @var \moodle_database $database session database */
- protected $database = null;
- /** @var bool $failed session read/init failed, do not write back to DB */
- protected $failed = false;
- /** @var string $lasthash hash of the session data content */
- protected $lasthash = null;
- /** @var int $acquiretimeout how long to wait for session lock */
- protected $acquiretimeout = 120;
- /**
- * Create new instance of handler.
- */
- public function __construct() {
- global $DB, $CFG;
- // Note: we store the reference here because we need to modify database in shutdown handler.
- $this->database = $DB;
- if (!empty($CFG->session_database_acquire_lock_timeout)) {
- $this->acquiretimeout = (int)$CFG->session_database_acquire_lock_timeout;
- }
- }
- /**
- * Init session handler.
- */
- public function init() {
- if (!$this->database->session_lock_supported()) {
- throw new exception('sessionhandlerproblem', 'error', '', null, 'Database does not support session locking');
- }
- $result = session_set_save_handler(array($this, 'handler_open'),
- array($this, 'handler_close'),
- array($this, 'handler_read'),
- array($this, 'handler_write'),
- array($this, 'handler_destroy'),
- array($this, 'handler_gc'));
- if (!$result) {
- throw new exception('dbsessionhandlerproblem', 'error');
- }
- }
- /**
- * Check the backend contains data for this session id.
- *
- * Note: this is intended to be called from manager::session_exists() only.
- *
- * @param string $sid
- * @return bool true if session found.
- */
- public function session_exists($sid) {
- // It was already checked in the calling code that the record in sessions table exists.
- return true;
- }
- /**
- * Kill all active sessions, the core sessions table is
- * purged afterwards.
- */
- public function kill_all_sessions() {
- // Nothing to do, the sessions table is cleared from core.
- return;
- }
- /**
- * Kill one session, the session record is removed afterwards.
- * @param string $sid
- */
- public function kill_session($sid) {
- // Nothing to do, the sessions table is purged afterwards.
- return;
- }
- /**
- * Open session handler.
- *
- * {@see http://php.net/manual/en/function.session-set-save-handler.php}
- *
- * @param string $save_path
- * @param string $session_name
- * @return bool success
- */
- public function handler_open($save_path, $session_name) {
- // Note: we use the already open database.
- return true;
- }
- /**
- * Close session handler.
- *
- * {@see http://php.net/manual/en/function.session-set-save-handler.php}
- *
- * @return bool success
- */
- public function handler_close() {
- if ($this->recordid) {
- try {
- $this->database->release_session_lock($this->recordid);
- } catch (\Exception $ex) {
- // Ignore any problems.
- }
- }
- $this->recordid = null;
- $this->lasthash = null;
- return true;
- }
- /**
- * Read session handler.
- *
- * {@see http://php.net/manual/en/function.session-set-save-handler.php}
- *
- * @param string $sid
- * @return string
- */
- public function handler_read($sid) {
- try {
- if (!$record = $this->database->get_record('sessions', array('sid'=>$sid), 'id')) {
- // Let's cheat and skip locking if this is the first access,
- // do not create the record here, let the manager do it after session init.
- $this->failed = false;
- $this->recordid = null;
- $this->lasthash = sha1('');
- return '';
- }
- if ($this->recordid and $this->recordid != $record->id) {
- error_log('Second session read with different record id detected, cannot read session');
- $this->failed = true;
- $this->recordid = null;
- return '';
- }
- if (!$this->recordid) {
- // Lock session if exists and not already locked.
- $this->database->get_session_lock($record->id, $this->acquiretimeout);
- $this->recordid = $record->id;
- }
- } catch (\dml_sessionwait_exception $ex) {
- // This is a fatal error, better inform users.
- // It should not happen very often - all pages that need long time to execute
- // should close session immediately after access control checks.
- error_log('Cannot obtain session lock for sid: '.$sid);
- $this->failed = true;
- throw $ex;
- } catch (\Exception $ex) {
- // Do not rethrow exceptions here, this should not happen.
- error_log('Unknown exception when starting database session : '.$sid.' - '.$ex->getMessage());
- $this->failed = true;
- $this->recordid = null;
- return '';
- }
- // Finally read the full session data because we know we have the lock now.
- if (!$record = $this->database->get_record('sessions', array('id'=>$record->id), 'id, sessdata')) {
- // Ignore - something else just deleted the session record.
- $this->failed = true;
- $this->recordid = null;
- return '';
- }
- $this->failed = false;
- if (is_null($record->sessdata)) {
- $data = '';
- $this->lasthash = sha1('');
- } else {
- $data = base64_decode($record->sessdata);
- $this->lasthash = sha1($record->sessdata);
- }
- return $data;
- }
- /**
- * Write session handler.
- *
- * {@see http://php.net/manual/en/function.session-set-save-handler.php}
- *
- * NOTE: Do not write to output or throw any exceptions!
- * Hopefully the next page is going to display nice error or it recovers...
- *
- * @param string $sid
- * @param string $session_data
- * @return bool success
- */
- public function handler_write($sid, $session_data) {
- if ($this->failed) {
- // Do not write anything back - we failed to start the session properly.
- return false;
- }
- $sessdata = base64_encode($session_data); // There might be some binary mess :-(
- $hash = sha1($sessdata);
- if ($hash === $this->lasthash) {
- return true;
- }
- try {
- if ($this->recordid) {
- $this->database->set_field('sessions', 'sessdata', $sessdata, array('id'=>$this->recordid));
- } else {
- // This happens in the first request when session record was just created in manager.
- $this->database->set_field('sessions', 'sessdata', $sessdata, array('sid'=>$sid));
- }
- } catch (\Exception $ex) {
- // Do not rethrow exceptions here, this should not happen.
- error_log('Unknown exception when writing database session data : '.$sid.' - '.$ex->getMessage());
- }
- return true;
- }
- /**
- * Destroy session handler.
- *
- * {@see http://php.net/manual/en/function.session-set-save-handler.php}
- *
- * @param string $sid
- * @return bool success
- */
- public function handler_destroy($sid) {
- if (!$session = $this->database->get_record('sessions', array('sid'=>$sid), 'id, sid')) {
- if ($sid == session_id()) {
- $this->recordid = null;
- $this->lasthash = null;
- }
- return true;
- }
- if ($this->recordid and $session->id == $this->recordid) {
- try {
- $this->database->release_session_lock($this->recordid);
- } catch (\Exception $ex) {
- // Ignore problems.
- }
- $this->recordid = null;
- $this->lasthash = null;
- }
- $this->database->delete_records('sessions', array('id'=>$session->id));
- return true;
- }
- /**
- * GC session handler.
- *
- * {@see http://php.net/manual/en/function.session-set-save-handler.php}
- *
- * @param int $ignored_maxlifetime moodle uses special timeout rules
- * @return bool success
- */
- public function handler_gc($ignored_maxlifetime) {
- // This should do something only if cron is not running properly...
- if (!$stalelifetime = ini_get('session.gc_maxlifetime')) {
- return true;
- }
- $params = array('purgebefore' => (time() - $stalelifetime));
- $this->database->delete_records_select('sessions', 'userid = 0 AND timemodified < :purgebefore', $params);
- return true;
- }
- }