session.php

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	* @param  string 	$namespace 	Namespace to use, default to 'default'
	* @return mixed $value the value from session or NULL if not set
	*/
	function clear( $name, $namespace = 'default' )
	{
		$namespace = '__'.$namespace; //add prefix to namespace to avoid collisions

		if( $this->_state !== 'active' ) {
			// @TODO :: generated error here
			return null;
		}

		$value	=	null;
		if( isset( $_SESSION[$namespace][$name] ) ) {
			$value	=	$_SESSION[$namespace][$name];
			unset( $_SESSION[$namespace][$name] );
		}

		return $value;
	}

	/**
	* Start a session
	*
	* Creates a session (or resumes the current one based on the state of the session)
 	*
	* @access private
	* @return boolean $result true on success
	*/
	function _start()
	{
		//  start session if not startet
		if( $this->_state == 'restart' ) {
			session_id( $this->_createId() );
		}

		session_cache_limiter('none');
		session_start();

		// Send modified header for IE 6.0 Security Policy
		header('P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"');

		return true;
	}


	/**
	 * Frees all session variables and destroys all data registered to a session
	 *
	 * This method resets the $_SESSION variable and destroys all of the data associated
	 * with the current session in its storage (file or DB). It forces new session to be
	 * started after this method is called. It does not unset the session cookie.
	 *
	 * @static
	 * @access public
	 * @return void
	 * @see	session_unset()
	 * @see	session_destroy()
	 */
	function destroy()
	{
		// session was already destroyed
		if( $this->_state === 'destroyed' ) {
			return true;
		}

		// In order to kill the session altogether, like to log the user out, the session id
		// must also be unset. If a cookie is used to propagate the session id (default behavior),
		// then the session cookie must be deleted.
		if (isset($_COOKIE[session_name()])) {
			setcookie(session_name(), '', time()-42000, '/');
		}

		session_unset();
		session_destroy();

		$this->_state = 'destroyed';
		return true;
	}

	/**
    * restart an expired or locked session
	*
	* @access public
	* @return boolean $result true on success
	* @see destroy
	*/
	function restart()
	{
		$this->destroy();
		if( $this->_state !==  'destroyed' ) {
			// @TODO :: generated error here
			return false;
		}

		// Re-register the session handler after a session has been destroyed, to avoid PHP bug
		$this->_store->register();

		$this->_state	=   'restart';
		$this->_start();
		$this->_state	=	'active';

		$this->_validate();
		$this->_setCounter();

		return true;
	}

	/**
	* Create a new session and copy variables from the old one
	*
	* @abstract
	* @access public
	* @return boolean $result true on success
	*/
	function fork()
	{
		if( $this->_state !== 'active' ) {
			// @TODO :: generated error here
			return false;
		}

		// save values
		$values	= $_SESSION;

		// keep session config
		$trans	=	ini_get( 'session.use_trans_sid' );
		if( $trans ) {
			ini_set( 'session.use_trans_sid', 0 );
		}
		$cookie	=	session_get_cookie_params();

		// create new session id
		$id	=	$this->_createId( strlen( $this->getId() ) );

		// kill session
		session_destroy();

		// re-register the session store after a session has been destroyed, to avoid PHP bug
		$this->_store->register();

		// restore config
		ini_set( 'session.use_trans_sid', $trans );
		session_set_cookie_params( $cookie['lifetime'], $cookie['path'], $cookie['domain'], $cookie['secure'] );

		// restart session with new id
		session_id( $id );
		session_start();

		return true;
	}

	 /**
	 * Writes session data and ends session
	 *
	 * Session data is usually stored after your script terminated without the need
	 * to call JSession::close(),but as session data is locked to prevent concurrent
	 * writes only one script may operate on a session at any time. When using
	 * framesets together with sessions you will experience the frames loading one
	 * by one due to this locking. You can reduce the time needed to load all the
	 * frames by ending the session as soon as all changes to session variables are
	 * done.
	 *
	 * @access public
	 * @see	session_write_close()
	 */
	function close() {
		session_write_close();
	}

	 /**
	 * Create a session id
	 *
	 * @static
	 * @access private
	 * @return string Session ID
	 */
	function _createId( )
	{
		$id = 0;
		while (strlen($id) < 32)  {
			$id .= mt_rand(0, mt_getrandmax());
		}

		$id	= md5( uniqid($id, true));
		return $id;
	}

	/**
	* Create a token-string
	*
	* @access protected
	* @param int $length lenght of string
	* @return string $id generated token
	*/
	function _createToken( $length = 32 )
	{
		static $chars	=	'0123456789abcdef';
		$max			=	strlen( $chars ) - 1;
		$token			=	'';
		$name 			=  session_name();
		for( $i = 0; $i < $length; ++$i ) {
			$token .=	$chars[ (rand( 0, $max )) ];
		}

		return md5($token.$name);
	}

	/**
	* Set counter of session usage
	*
	* @access protected
	* @return boolean $result true on success
	*/
	function _setCounter()
	{
		$counter = $this->get( 'session.counter', 0 );
		++$counter;

		$this->set( 'session.counter', $counter );
		return true;
	}

	/**
	* Set the session timers
	*
	* @access protected
	* @return boolean $result true on success
	*/
	function _setTimers()
	{
		if( !$this->has( 'session.timer.start' ) )
		{
			$start	=	time();

			$this->set( 'session.timer.start' , $start );
			$this->set( 'session.timer.last'  , $start );
			$this->set( 'session.timer.now'   , $start );
		}

		$this->set( 'session.timer.last', $this->get( 'session.timer.now' ) );
		$this->set( 'session.timer.now', time() );

		return true;
	}

	/**
	* set additional session options
	*
	* @access protected
	* @param array $options list of parameter
	* @return boolean $result true on success
	*/
	function _setOptions( &$options )
	{
		// set name
		if( isset( $options['name'] ) ) {
			session_name( md5($options['name']) );
		}

		// set id
		if( isset( $options['id'] ) ) {
			session_id( $options['id'] );
		}

		// set expire time
		if( isset( $options['expire'] ) ) {
			$this->_expire	=	$options['expire'];
		}

		// get security options
		if( isset( $options['security'] ) ) {
			$this->_security	=	explode( ',', $options['security'] );
		}

		//sync the session maxlifetime
		ini_set('session.gc_maxlifetime', $this->_expire);

		return true;
	}

	/**
	* Do some checks for security reason
	*
	* - timeout check (expire)
	* - ip-fixiation
	* - browser-fixiation
	*
	* If one check failed, session data has to be cleaned.
	*
	* @access protected
	* @param boolean $restart reactivate session
	* @return boolean $result true on success
	* @see http://shiflett.org/articles/the-truth-about-sessions
	*/
	function _validate( $restart = false )
	{
		// allow to restart a session
		if( $restart )
		{
			$this->_state	=	'active';

			$this->set( 'session.client.address'	, null );
			$this->set( 'session.client.forwarded'	, null );
			$this->set( 'session.client.browser'	, null );
			$this->set( 'session.token'				, null );
		}

		// check if session has expired
		if( $this->_expire )
		{
			$curTime =	$this->get( 'session.timer.now' , 0  );
			$maxTime =	$this->get( 'session.timer.last', 0 ) + (60 * $this->_expire);

			// empty session variables
			if( $maxTime < $curTime ) {
				$this->_state	=	'expired';
				return false;
			}
		}

		// record proxy forwarded for in the session in case we need it later
		if( isset( $_SERVER['HTTP_X_FORWARDED_FOR'] ) ) {
			$this->set( 'session.client.forwarded', $_SERVER['HTTP_X_FORWARDED_FOR']);
		}

		// check for client adress
		if( in_array( 'fix_adress', $this->_security ) && isset( $_SERVER['REMOTE_ADDR'] ) )
		{
			$ip	= $this->get( 'session.client.address' );

			if( $ip === null ) {
				$this->set( 'session.client.address', $_SERVER['REMOTE_ADDR'] );
			}
			else if( $_SERVER['REMOTE_ADDR'] !== $ip )
			{
				$this->_state	=	'error';
				return false;
			}
		}

		// check for clients browser
		if( in_array( 'fix_browser', $this->_security ) && isset( $_SERVER['HTTP_USER_AGENT'] ) )
		{
			$browser = $this->get( 'session.client.browser' );

			if( $browser === null ) {
				$this->set( 'session.client.browser', $_SERVER['HTTP_USER_AGENT']);
			}
			else if( $_SERVER['HTTP_USER_AGENT'] !== $browser )
			{
//				$this->_state	=	'error';
//				return false;
			}
		}

		return true;
	}
}