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<?php

/**

 * CodeIgniter

 *

 * An open source application development framework for PHP

 *

 * This content is released under the MIT License (MIT)

 *

 * Copyright (c) 2014 - 2018, British Columbia Institute of Technology

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 *

 * @package	CodeIgniter

 * @author	EllisLab Dev Team

 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)

 * @copyright	Copyright (c) 2014 - 2018, British Columbia Institute of Technology (http://bcit.ca/)

 * @license	http://opensource.org/licenses/MIT	MIT License

 * @link	https://codeigniter.com

 * @since	Version 3.0.0

 * @filesource

 */

defined('BASEPATH') OR exit('No direct script access allowed');

/**

 * CodeIgniter Session Database Driver

 *

 * @package	CodeIgniter

 * @subpackage	Libraries

 * @category	Sessions

 * @author	Andrey Andreev

 * @link	https://codeigniter.com/user_guide/libraries/sessions.html

 */

class CI_Session_database_driver extends CI_Session_driver implements SessionHandlerInterface {

	/**

	 * DB object

	 *

	 * @var	object

	 */

	protected $_db;

	/**

	 * Row exists flag

	 *

	 * @var	bool

	 */

	protected $_row_exists = FALSE;

	/**

	 * Lock "driver" flag

	 *

	 * @var	string

	 */

	protected $_platform;

	// ------------------------------------------------------------------------

	/**

	 * Class constructor

	 *

	 * @param	array	$params	Configuration parameters

	 * @return	void

	 */

	public function __construct(&$params)

	{

		parent::__construct($params);

		$CI =& get_instance();

		isset($CI->db) OR $CI->load->database();

		$this->_db = $CI->db;

		if ( ! $this->_db instanceof CI_DB_query_builder)

		{

			throw new Exception('Query Builder not enabled for the configured database. Aborting.');

		}

		elseif ($this->_db->pconnect)

		{

			throw new Exception('Configured database connection is persistent. Aborting.');

		}

		elseif ($this->_db->cache_on)

		{

			throw new Exception('Configured database connection has cache enabled. Aborting.');

		}

		$db_driver = $this->_db->dbdriver.(empty($this->_db->subdriver) ? '' : '_'.$this->_db->subdriver);

		if (strpos($db_driver, 'mysql') !== FALSE)

		{

			$this->_platform = 'mysql';

		}

		elseif (in_array($db_driver, array('postgre', 'pdo_pgsql'), TRUE))

		{

			$this->_platform = 'postgre';

		}

		// Note: BC work-around for the old 'sess_table_name' setting, should be removed in the future.

		if ( ! isset($this->_config['save_path']) && ($this->_config['save_path'] = config_item('sess_table_name')))

		{

			log_message('debug', 'Session: "sess_save_path" is empty; using BC fallback to "sess_table_name".');

		}

	}

	// ------------------------------------------------------------------------

	/**

	 * Open

	 *

	 * Initializes the database connection

	 *

	 * @param	string	$save_path	Table name

	 * @param	string	$name		Session cookie name, unused

	 * @return	bool

	 */

	public function open($save_path, $name)

	{

		if (empty($this->_db->conn_id) && ! $this->_db->db_connect())

		{

			return $this->_fail();

		}

		return $this->_success;

	}

	// ------------------------------------------------------------------------

	/**

	 * Read

	 *

	 * Reads session data and acquires a lock

	 *

	 * @param	string	$session_id	Session ID

	 * @return	string	Serialized session data

	 */

	public function read($session_id)

	{

		if ($this->_get_lock($session_id) !== FALSE)

		{

			// Prevent previous QB calls from messing with our queries

			$this->_db->reset_query();

			// Needed by write() to detect session_regenerate_id() calls

			$this->_session_id = $session_id;

			$this->_db

				->select('data')

				->from($this->_config['save_path'])

				->where('id', $session_id);

			if ($this->_config['match_ip'])

			{

				$this->_db->where('ip_address', $_SERVER['REMOTE_ADDR']);

			}

			if ( ! ($result = $this->_db->get()) OR ($result = $result->row()) === NULL)

			{

				// PHP7 will reuse the same SessionHandler object after

				// ID regeneration, so we need to explicitly set this to

				// FALSE instead of relying on the default ...

				$this->_row_exists = FALSE;

				$this->_fingerprint = md5('');

				return '';

			}

			// PostgreSQL's variant of a BLOB datatype is Bytea, which is a

			// PITA to work with, so we use base64-encoded data in a TEXT

			// field instead.

			$result = ($this->_platform === 'postgre')

				? base64_decode(rtrim($result->data))

				: $result->data;

			$this->_fingerprint = md5($result);

			$this->_row_exists = TRUE;

			return $result;

		}

		$this->_fingerprint = md5('');

		return '';

	}

	// ------------------------------------------------------------------------

	/**

	 * Write

	 *

	 * Writes (create / update) session data

	 *

	 * @param	string	$session_id	Session ID

	 * @param	string	$session_data	Serialized session data

	 * @return	bool

	 */

	public function write($session_id, $session_data)

	{

		// Prevent previous QB calls from messing with our queries

		$this->_db->reset_query();

		// Was the ID regenerated?

		if (isset($this->_session_id) && $session_id !== $this->_session_id)

		{

			if ( ! $this->_release_lock() OR ! $this->_get_lock($session_id))

			{

				return $this->_fail();

			}

			$this->_row_exists = FALSE;

			$this->_session_id = $session_id;

		}

		elseif ($this->_lock === FALSE)

		{

			return $this->_fail();

		}

		if ($this->_row_exists === FALSE)

		{

			$insert_data = array(

				'id' => $session_id,

				'ip_address' => $_SERVER['REMOTE_ADDR'],

				'timestamp' => time(),

				'data' => ($this->_platform === 'postgre' ? base64_encode($session_data) : $session_data)

			);

			if ($this->_db->insert($this->_config['save_path'], $insert_data))

			{

				$this->_fingerprint = md5($session_data);

				$this->_row_exists = TRUE;

				return $this->_success;

			}

			return $this->_fail();

		}

		$this->_db->where('id', $session_id);

		if ($this->_config['match_ip'])

		{

			$this->_db->where('ip_address', $_SERVER['REMOTE_ADDR']);

		}

		$update_data = array('timestamp' => time());

		if ($this->_fingerprint !== md5($session_data))

		{

			$update_data['data'] = ($this->_platform === 'postgre')

				? base64_encode($session_data)

				: $session_data;

		}

		if ($this->_db->update($this->_config['save_path'], $update_data))

		{

			$this->_fingerprint = md5($session_data);

			return $this->_success;

		}

		return $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Close

	 *

	 * Releases locks

	 *

	 * @return	bool

	 */

	public function close()

	{

		return ($this->_lock && ! $this->_release_lock())

			? $this->_fail()

			: $this->_success;

	}

	// ------------------------------------------------------------------------

	/**

	 * Destroy

	 *

	 * Destroys the current session.

	 *

	 * @param	string	$session_id	Session ID

	 * @return	bool

	 */

	public function destroy($session_id)

	{

		if ($this->_lock)

		{

			// Prevent previous QB calls from messing with our queries

			$this->_db->reset_query();

			$this->_db->where('id', $session_id);

			if ($this->_config['match_ip'])

			{

				$this->_db->where('ip_address', $_SERVER['REMOTE_ADDR']);

			}

			if ( ! $this->_db->delete($this->_config['save_path']))

			{

				return $this->_fail();

			}

		}

		if ($this->close() === $this->_success)

		{

			$this->_cookie_destroy();

			return $this->_success;

		}

		return $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Garbage Collector

	 *

	 * Deletes expired sessions

	 *

	 * @param	int 	$maxlifetime	Maximum lifetime of sessions

	 * @return	bool

	 */

	public function gc($maxlifetime)

	{

		// Prevent previous QB calls from messing with our queries

		$this->_db->reset_query();

		return ($this->_db->delete($this->_config['save_path'], 'timestamp < '.(time() - $maxlifetime)))

			? $this->_success

			: $this->_fail();

	}

	// ------------------------------------------------------------------------

	/**

	 * Get lock

	 *

	 * Acquires a lock, depending on the underlying platform.

	 *

	 * @param	string	$session_id	Session ID

	 * @return	bool

	 */

	protected function _get_lock($session_id)

	{

		if ($this->_platform === 'mysql')

		{

			$arg = md5($session_id.($this->_config['match_ip'] ? '_'.$_SERVER['REMOTE_ADDR'] : ''));

			if ($this->_db->query("SELECT GET_LOCK('".$arg."', 300) AS ci_session_lock")->row()->ci_session_lock)

			{

				$this->_lock = $arg;

				return TRUE;

			}

			return FALSE;

		}

		elseif ($this->_platform === 'postgre')

		{

			$arg = "hashtext('".$session_id."')".($this->_config['match_ip'] ? ", hashtext('".$_SERVER['REMOTE_ADDR']."')" : '');

			if ($this->_db->simple_query('SELECT pg_advisory_lock('.$arg.')'))

			{

				$this->_lock = $arg;

				return TRUE;

			}

			return FALSE;

		}

		return parent::_get_lock($session_id);

	}

	// ------------------------------------------------------------------------

	/**

	 * Release lock

	 *

	 * Releases a previously acquired lock

	 *

	 * @return	bool

	 */

	protected function _release_lock()

	{

		if ( ! $this->_lock)

		{

			return TRUE;

		}

		if ($this->_platform === 'mysql')

		{

			if ($this->_db->query("SELECT RELEASE_LOCK('".$this->_lock."') AS ci_session_lock")->row()->ci_session_lock)

			{

				$this->_lock = FALSE;

				return TRUE;

			}

			return FALSE;

		}

		elseif ($this->_platform === 'postgre')

		{

			if ($this->_db->simple_query('SELECT pg_advisory_unlock('.$this->_lock.')'))

			{

				$this->_lock = FALSE;

				return TRUE;

			}

			return FALSE;

		}

		return parent::_release_lock();

	}

}