Current File : /home/vacivi36/ava/lib/classes/session/database.php
<?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.
if ($this->requires_write_lock()) {
$this->database->get_session_lock($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;
}
}
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