<?php



class Session_cache extends CI_Driver {



	protected $CI;

	protected $sess_id;



	protected $sess_cache_driver;

	protected $sess_encrypt_cookie;

	protected $sess_cookie_name;

	protected $cookie_prefix;

	protected $cookie_path;

	protected $cookie_domain;

	protected $cookie_secure;



	public function __construct()

	{

		$this->CI = get_instance();

		

		foreach (array('sess_cache_driver','sess_encrypt_cookie','sess_cookie_name','cookie_prefix','cookie_path','cookie_domain','cookie_secure') as $key)

		{

			$this->$key = $this->CI->config->item($key);

		}



		// Load cache library, assign it to the object

		$this->CI->load->driver('cache', array('adapter' => $this->sess_cache_driver));

	}



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



	/**

	 * Fetch the current session data if it exists

	 *

	 * @access	public

	 * @return	bool

	 */

	public function sess_read()

	{

		// Fetch the cookie

		$session = $this->CI->input->cookie($this->sess_cookie_name);



		// No cookie?  Goodbye cruel world!...

		if ($session === FALSE)

		{

			log_message('debug', 'A session cookie was not found.');

			return FALSE;

		}



		// Decrypt the cookie data

		if ($this->sess_encrypt_cookie == TRUE)

		{

			$session = $this->CI->encrypt->decode($session);

		}

		else

		{

			// encryption was not used, so we need to check the md5 hash

			$hash		= substr($session, strlen($session)-32); // get last 32 chars

			$session	= substr($session, 0, strlen($session)-32);



			// Does the md5 hash match?  This is to prevent manipulation of session data in userspace

			if ($hash !==  md5($session.$this->parent->encryption_key))

			{

				log_message('error', 'The session cookie data did not match what was expected. This could be a possible hacking attempt.');

				$this->sess_destroy();

				return FALSE;

			}

		}



		// Unserialize the session array

		$session = $this->parent->_unserialize($session);



		if( ! is_array($session) OR ! isset($session['session_id']))

		{

			$this->sess_destroy();

			return FALSE;

		}



		$this->sess_id = $session['session_id'];



		// Is there a corresponding session in the cache?

		$cache = $this->CI->cache->get($this->sess_id);



		if($cache === FALSE)

		{

			log_message('debug', 'Session not found in cache.');

			return FALSE;

		}



		$cache = $this->parent->_unserialize($cache);



		// Is the session data we unserialized an array with the correct format?

		if ( ! isset($session['ip_address']) OR ! isset($session['user_agent']) OR ! isset($session['last_activity']) OR ! is_array($cache) OR ! isset($cache['session_id']) OR ! isset($cache['ip_address']) OR ! isset($cache['user_agent']) OR ! isset($cache['last_activity']))

		{

			$this->sess_destroy();

			return FALSE;

		}



		// Is the session current?

		if (($session['last_activity'] + $this->parent->sess_expiration) < $this->parent->now)

		{

			$this->sess_destroy();

			return FALSE;

		}



		// Does the IP Match?

		if ($this->parent->sess_match_ip == TRUE AND ($session['ip_address'] != $this->CI->input->ip_address() OR $cache['ip_address'] != $this->CI->input->ip_address()))

		{

			$this->sess_destroy();

			return FALSE;

		}



		// Does the User Agent Match?

		if ($this->parent->sess_match_useragent == TRUE AND (trim($session['user_agent']) != trim(substr($this->CI->input->user_agent(), 0, 120)) OR trim($cache['user_agent']) != trim(substr($this->CI->input->user_agent(), 0, 120))))

		{

			$this->sess_destroy();

			return FALSE;

		}

		

		// Session is valid!

		$this->parent->userdata = $cache;

		unset($session, $cache);



		return TRUE;

	}



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



	/**

	 * Write the session data

	 *

	 * @access	public

	 * @return	void

	 */

	public function sess_write()

	{

		if( ! $this->parent->check_write())

		{

			$this->CI->cache->save($this->sess_id, $this->parent->_serialize($this->parent->userdata), $this->parent->sess_expiration);



			$this->parent->track_write();



			$this->_set_cookie();

		}

	}



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



	/**

	 * Create a new session

	 *

	 * @access	public

	 * @return	void

	 */

	public function sess_create()

	{

		$sessid = '';

		while (strlen($sessid) < 32)

		{

			$sessid .= mt_rand(0, mt_getrandmax());

		}



		$this->sess_id = md5(uniqid($sessid.$this->CI->input->ip_address(), TRUE));



		$this->parent->userdata = array(

			'session_id'	=> $this->sess_id,

			'ip_address'	=> $this->CI->input->ip_address(),

			'user_agent'	=> substr($this->CI->input->user_agent(), 0, 120),

			'last_activity'	=> $this->parent->now

		);



		$custom_userdata = array('user_data' => '');



		// Save session to cache

		$this->CI->cache->save($this->sess_id, $this->parent->userdata+$custom_userdata);



		// Write the cookie

		$this->_set_cookie();

	}



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



	/**

	 * Update an existing session

	 *

	 * @access	public

	 * @return	void

	 */

	public function sess_update()

	{

		// We only update the session every five minutes by default

		if (($this->parent->userdata['last_activity'] + $this->parent->sess_time_to_update) >= $this->parent->now)

		{

			return;

		}



		// Save the old session id so we know which record to

		// update in the database if we need it

		$old_sessid = $this->sess_id;

		$new_sessid = '';

		while (strlen($new_sessid) < 32)

		{

			$new_sessid .= mt_rand(0, mt_getrandmax());

		}



		// To make the session ID even more secure we'll combine it with the user's IP, then hash

		$this->sess_id = md5(uniqid($new_sessid.$this->CI->input->ip_address(), TRUE));



		// Update the session data in the session data array

		$this->parent->userdata['session_id'] = $this->sess_id;

		$this->parent->userdata['last_activity'] = $this->now;



		// Save new cache, delete old cache

		$this->CI->cache->save($this->sess_id, $this->parent->_serialize($this->parent->userdata), $this->parent->sess_expiration);

		$this->CI->cache->delete($old_sessid);



		// Write the cookie

		$this->_set_cookie();

	}



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



	/**

	 * Destroy the current session

	 *

	 * @access	public

	 * @return	void

	 */

	public function sess_destroy()

	{

		if( ! empty($this->sess_id))

		{

			$this->CI->cache->delete($this->sess_id);

		}



		$this->parent->userdata = array();

		$this->sess_id = '';



		// Kill the cookie

		setcookie(

			$this->sess_cookie_name,

			addslashes(serialize(array())),

			($this->parent->now - 31500000),

			$this->cookie_path,

			$this->cookie_domain,

			0

		);

	}



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

	

	/**

	 * Does nothing for cache sessions

	 *

	 * @access private

	 * @return void

	 */

	public function _sess_gc(){}



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



	/**

	 * Write the session cookie

	 *

	 * @access	private

	 * @return	void

	 */

	protected function _set_cookie()

	{

		$cookie_data = array(

			'session_id'	=> $this->parent->userdata['session_id'],

			'ip_address'	=> $this->parent->userdata['ip_address'],

			'user_agent'	=> $this->parent->userdata['user_agent'],

			'last_activity'	=> $this->parent->userdata['last_activity']

		);



		// Serialize the userdata for the cookie

		$cookie_data = $this->parent->_serialize($cookie_data);



		if ($this->sess_encrypt_cookie == TRUE)

		{

			$cookie_data = $this->CI->encrypt->encode($cookie_data);

		}

		else

		{

			// if encryption is not used, we provide an md5 hash to prevent userside tampering

			$cookie_data = $cookie_data.md5($cookie_data.$this->parent->encryption_key);

		}



		$expire = $this->parent->sess_expiration + time();



		// Set the cookie

		setcookie(

			$this->sess_cookie_name,

			$cookie_data,

			$expire,

			$this->cookie_path,

			$this->cookie_domain,

			$this->cookie_secure

		);

	}



}