Hybrid Cookie or DB session driver for codeigniter - allows for API or cookie based auth

Session_hybrid.php

<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.2.4 or newer
 *
 * NOTICE OF LICENSE
 *
 * Licensed under the Open Software License version 3.0
 *
 * This source file is subject to the Open Software License (OSL 3.0) that is
 * bundled with this package in the files license.txt / license.rst.  It is
 * also available through the world wide web at this URL:
 * http://opensource.org/licenses/OSL-3.0
 * If you did not receive a copy of the license and are unable to obtain it
 * through the world wide web, please send an email to
 * licensing@ellislab.com so we can send you a copy immediately.
 *
 * @package		CodeIgniter
 * @author		EllisLab Dev Team
 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
 * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
 * @link		http://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Cookie or database based session management driver
 *
 * This is a hybridized version of the classic CI_Session functionality, as written by EllisLab, abstracted out to a driver.
 * It allows for cookie storage as well as API based requests back and forth.
 *
 * @package		CodeIgniter
 * @subpackage	Libraries
 * @category	Sessions
 * @author		EllisLab Dev Team
 * @link		http://codeigniter.com/user_guide/libraries/sessions.html
 */
class CI_Session_hybrid extends CI_Session_driver {

	/**
	 * Whether to encrypt the session cookie
	 *
	 * @var bool
	 */
	public $sess_encrypt_cookie		= FALSE;

	/**
	 * Name of the database table in which to store sessions
	 *
	 * @var string
	 */
	public $sess_table_name			= '';

	/**
	 * Length of time (in seconds) for sessions to expire
	 *
	 * @var int
	 */
	public $sess_expiration			= 7200;

	/**
	 * Whether to kill session on close of browser window
	 *
	 * @var bool
	 */
	public $sess_expire_on_close	= FALSE;

	/**
	 * Whether to match session on ip address
	 *
	 * @var bool
	 */
	public $sess_match_ip			= FALSE;

	/**
	 * Whether to match session on user-agent
	 *
	 * @var bool
	 */
	public $sess_match_useragent	= TRUE;

	/**
	 * Name of session cookie
	 *
	 * @var string
	 */
	public $sess_cookie_name		= 'ci_session';

	/**
	 * Session cookie prefix
	 *
	 * @var string
	 */
	public $cookie_prefix			= '';

	/**
	 * Session cookie path
	 *
	 * @var string
	 */
	public $cookie_path				= '';

	/**
	 * Session cookie domain
	 *
	 * @var string
	 */
	public $cookie_domain			= '';

	/**
	 * Whether to set the cookie only on HTTPS connections
	 *
	 * @var bool
	 */
	public $cookie_secure			= FALSE;

	/**
	 * Whether cookie should be allowed only to be sent by the server
	 *
	 * @var bool
	 */
	public $cookie_httponly 		= FALSE;

	/**
	 * Interval at which to update session
	 *
	 * @var int
	 */
	public $sess_time_to_update		= 300;

	/**
	 * Key with which to encrypt the session cookie
	 *
	 * @var string
	 */
	public $encryption_key			= '';

	/**
	 * Timezone to use for the current time
	 *
	 * @var string
	 */
	public $time_reference			= 'local';

	/**
	 * Session data
	 *
	 * @var array
	 */
	public $userdata				= array();

	/**
	 * Current time
	 *
	 * @var int
	 */
	public $now;
	
	//key for looking up a session, may be passed in lieu of a cookie
	public $sesslookup = NULL;
	private $sessionFromDB = false;
	private $usingAPI = false;
	private $remoteIP = '';
	
	// ------------------------------------------------------------------------

	/**
	 * Default userdata keys
	 *
	 * @var	array
	 */
	protected $defaults = array(
		'session_id' => NULL,
		'ip_address' => NULL,
		'user_agent' => NULL,
		'last_activity' => NULL
	);

	/**
	 * Data needs DB update flag
	 *
	 * @var	bool
	 */
	protected $data_dirty = FALSE;

	/**
	 * Standardize newlines flag
	 *
	 * @var	bool
	 */
	protected $_standardize_newlines;

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

	/**
	 * Ini\tialize session driver object
	 *
	 * @return	void
	 */
	protected function initialize()
	{
		// Set all the session preferences, which can either be set
		// manually via the $params array or via the config file
		$prefs = array(
			'sess_encrypt_cookie',
			'sess_table_name',
			'sess_expiration',
			'sess_expire_on_close',
			'sess_match_ip',
			'sess_match_useragent',
			'sess_cookie_name',
			'cookie_path',
			'cookie_domain',
			'cookie_secure',
			'cookie_httponly',
			'sess_time_to_update',
			'time_reference',
			'cookie_prefix',
			'encryption_key'
		);

		$this->_standardize_newlines = (bool) config_item('standardize_newlines');

		foreach ($prefs as $key)
		{
			$this->$key = isset($this->_parent->params[$key])
				? $this->_parent->params[$key]
				: $this->CI->config->item($key);
		}
		
		//if we're using an API and the session is already named
		if (!empty($this->_parent->params['usingAPI']) && $this->_parent->params['usingAPI']) {
		  $this->usingAPI = $this->_parent->params['usingAPI'];
		  
		  if (!empty($this->_parent->params['session_id'])) {
			  $this->sesslookup = $this->_parent->params['session_id'];
		  }
		  
		  if (!empty($this->_parent->params['remoteIP'])) {
			  $this->remoteIP = $this->_parent->params['remoteIP'];
		  }
		}
		
		if (empty($this->encryption_key))
		{
			show_error('In order to use the Cookie Session driver you are required to set an encryption key in your config file.');
		}

		// Do we need encryption? If so, load the encryption class
		if ($this->sess_encrypt_cookie === TRUE)
		{
			$this->CI->load->library('encryption');
		}

		// Load database driver
		$this->CI->load->database();

		// Register shutdown function
		register_shutdown_function(array($this, '_update_db'));

		// Set the "now" time. Can either be GMT or server time, based on the config prefs.
		// We use this to set the "last activity" time
		$this->now = $this->_get_time();

		// Set the session length. If the session expiration is
		// set to zero we'll set the expiration two years from now.
		if ($this->sess_expiration === 0)
		{
			$this->sess_expiration = (60*60*24*365*2);
		}

		// Set the cookie name
		if (!empty($this->sesslookup) && $this->usingAPI) {
		  $this->sess_cookie_name = $this->cookie_prefix.$this->sesslookup;
		} else {
		  $this->sess_cookie_name = $this->cookie_prefix.$this->sess_cookie_name;
		}
		
		// Run the Session routine. If a session doesn't exist we'll
		// create a new one. If it does, we'll update it.
		if ( ! $this->_sess_read())
		{
			$this->_sess_create();
		}
		else
		{
			$this->_sess_update();
		}

		// Delete expired sessions if necessary
		$this->_sess_gc();
	}

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

	/**
	 * Write the session data
	 *
	 * @return	void
	 */
	public function sess_save()
	{
		// Mark custom data as dirty so we know to update the DB
		$this->data_dirty = TRUE;

		// Write the cookie
		$this->_set_cookie();
	}

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

	/**
	 * Destroy the current session
	 *
	 * @return	void
	 */
	public function sess_destroy()
	{
		// Kill the session DB row
		if (isset($this->userdata['session_id']))
		{
			$this->CI->db->delete($this->sess_table_name, array('session_id' => $this->userdata['session_id']));
			$this->data_dirty = FALSE;
		}

		// Kill the cookie
		$this->_setcookie($this->sess_cookie_name, '', ($this->now - 31500000),
			$this->cookie_path, $this->cookie_domain, 0);

		// Kill session data
		$this->userdata = array();
	}

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

	/**
	 * Regenerate the current session
	 *
	 * Regenerate the session id
	 *
	 * @param	bool	Destroy session data flag (default: false)
	 * @return	void
	 */
	public function sess_regenerate($destroy = FALSE)
	{
		// Check destroy flag
		if ($destroy)
		{
			// Destroy old session and create new one
			$this->sess_destroy();
			$this->_sess_create();
		}
		else
		{
			// Just force an update to recreate the id
			$this->_sess_update(TRUE);
		}
	}

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

	/**
	 * Get a reference to user data array
	 *
	 * @return	array	Reference to userdata
	 */
	public function &get_userdata()
	{
		return $this->userdata;
	}

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

	/**
	 * Fetch the current session data if it exists
	 *
	 * @return	bool
	 */
	protected function _sess_read()
	{	
		//API only - is the session in the db? API ignores cookies
		if ($this->usingAPI && !empty($this->sesslookup))
		{
			$this->CI->db->where('session_id', $this->sesslookup);

			// Is caching in effect? Turn it off
			$db_cache = $this->CI->db->cache_on;
			$this->CI->db->cache_off();

			$query = $this->CI->db->limit(1)->get($this->sess_table_name);

			// Was caching in effect?
			if ($db_cache)
			{
				// Turn it back on
				$this->CI->db->cache_on();
			}
			
			$session = (array) $query->row();
			
			if (!empty($session['user_data']))
			{
				$custom_data = unserialize(trim($session['user_data']));

				if (is_array($custom_data))
				{
					$session = $session + $custom_data;
				}
			}

			unset($session['user_data']);
			unset($session['id']);
			
			if (!empty($session)) {
			  $this->userdata = $session;
			  $this->sessionFromDB = TRUE;
			  
			  $this->_sess_update(TRUE);
			} else {
			  log_message('debug', 'A db session was not found.');
			  return FALSE;
			}
		} else {
		  // Fetch the cookie
		  $session = $this->CI->input->cookie($this->sess_cookie_name);
		}
		
		// No session? Goodbye cruel world!...
		if ($session === NULL)
		{
			log_message('debug', 'A session cookie was not found.');
			return FALSE;
		}

		if (!$this->sessionFromDB) {
		  if ($this->sess_encrypt_cookie === TRUE)
		  {
			  $session = $this->CI->encryption->decrypt($session);
			  if ($session === FALSE)
			  {
				  log_message('error', 'Session: Unable to decrypt the session cookie, possibly due to a HMAC mismatch.');
				  return FALSE;
			  }
		  }
		  else
		  {
			  if ( ! $this->sesslookup && ($len = strlen($session) - 40) <= 0)
			  {
				  log_message('error', 'Session: The session cookie was not signed.');
				  return FALSE;
			  }
  
			  // Check cookie authentication
			  $hmac = substr($session, $len);
			  $session = substr($session, 0, $len);
  
			  // Time-attack-safe comparison
			  $hmac_check = hash_hmac('sha1', $session, $this->encryption_key);
			  $diff = 0;
			  for ($i = 0; $i < 40; $i++)
			  {
				  $diff |= ord($hmac[$i]) ^ ord($hmac_check[$i]);
			  }
  
			  if ($diff !== 0)
			  {
				  log_message('error', 'Session: HMAC mismatch. The session cookie data did not match what was expected.');
				  $this->sess_destroy();
				  return FALSE;
			  }
		  }
		  
		  // Unserialize the session array
		  $session = @unserialize($session);
		}

		// Is the session data we unserialized an array with the correct format?
		if ( ! is_array($session) OR ! isset($session['session_id'], $session['ip_address'], $session['user_agent'], $session['last_activity']))
		{
			log_message('debug', 'Session: Wrong cookie data format');
			$this->sess_destroy();
			return FALSE;
		}		
		
		// Is the session current?
		if (($session['last_activity'] + $this->sess_expiration) < $this->now OR $session['last_activity'] > $this->now)
		{
			log_message('debug', 'Session: Expired');
			$this->sess_destroy();
			return FALSE;
		}

		// Does the IP match?
		if ($this->sess_match_ip === TRUE && $session['ip_address'] !== $this->CI->input->ip_address())
		{
			log_message('debug', 'Session: IP address mismatch');
			$this->sess_destroy();
			return FALSE;
		}

		// Does the User Agent Match?
		if ($this->sess_match_useragent === TRUE &&
			trim($session['user_agent']) !== trim(substr($this->CI->input->user_agent(), 0, 120)))
		{
			log_message('debug', 'Session: User Agent string mismatch');
			$this->sess_destroy();
			return FALSE;
		}

		// Is there a corresponding session in the DB?
		if (!$this->sessionFromDB) //if we queried it already, no reason to do so again
		{
			$this->CI->db->where('session_id', $session['session_id']);

			if ($this->sess_match_ip === TRUE)
			{
				$this->CI->db->where('ip_address', $session['ip_address']);
			}

			if ($this->sess_match_useragent === TRUE)
			{
				$this->CI->db->where('user_agent', $session['user_agent']);
			}

			// Is caching in effect? Turn it off
			$db_cache = $this->CI->db->cache_on;
			$this->CI->db->cache_off();

			$query = $this->CI->db->limit(1)->get($this->sess_table_name);

			// Was caching in effect?
			if ($db_cache)
			{
				// Turn it back on
				$this->CI->db->cache_on();
			}

			// No result? Kill it!
			if (empty($query) OR $query->num_rows() === 0)
			{
				log_message('debug', 'Session: No match found in our database');
				$this->sess_destroy();
				return FALSE;
			}

			// Is there custom data? If so, add it to the main session array
			$row = $query->row();
			if ( ! empty($row->user_data))
			{
				$custom_data = unserialize(trim($row->user_data));

				if (is_array($custom_data))
				{
					$session = $session + $custom_data;
				}
			}
		}	
	  
		// Session is valid!
		$this->userdata = $session;
		return TRUE;
	}

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

	/**
	 * Create a new session
	 *
	 * @return	void
	 */
	protected function _sess_create()
	{
		// Initialize userdata
		$this->userdata = array(
			'session_id'	=> $this->_make_sess_id(),
			'ip_address'	=> $this->CI->input->ip_address(),
			'user_agent'	=> trim(substr($this->CI->input->user_agent(), 0, 120)),
			'last_activity'	=> $this->now,
		);
		
		if ($this->usingAPI) $this->userdata['ip_address'] = $this->remoteIP;

		log_message('debug', 'Session: Creating new session ('.$this->userdata['session_id'].')');

		// Add empty user_data field and save the data to the DB
		$this->CI->db->set('user_data', '')->insert($this->sess_table_name, $this->userdata);

		// Write the cookie
		$this->_set_cookie();
	}

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

	/**
	 * Update an existing session
	 *
	 * @param	bool	Force update flag (default: false)
	 * @return	void
	 */
	protected function _sess_update($force = FALSE)
	{
		// We only update the session every five minutes by default (unless forced)
		if (!$force || ($this->userdata['last_activity'] + $this->sess_time_to_update) >= $this->now)
		{
			return;
		}

		// Update last activity to now
		$this->userdata['last_activity'] = $this->now;
		
		// update the ip if API called
		if ($this->sessionFromDB) $this->userdata['ip_address'] = $this->usingAPI;

		// Save the old session id so we know which DB record to update
		$old_sessid = $this->userdata['session_id'];

		// Changing the session ID during an AJAX or API call causes problems
		if (!$this->CI->input->is_ajax_request() && !$this->sessionFromDB)
		{
			// Get new id
			$this->userdata['session_id'] = $this->_make_sess_id();

			log_message('debug', 'Session: Regenerate ID');
		}

		$this->CI->db->where('session_id', $old_sessid);

		if ($this->sess_match_ip === TRUE)
		{
			$this->CI->db->where('ip_address', $this->CI->input->ip_address());
		}

		if ($this->sess_match_useragent === TRUE)
		{
			$this->CI->db->where('user_agent', trim(substr($this->CI->input->user_agent(), 0, 120)));
		}

		// Update the session ID and last_activity field in the DB
		$this->CI->db->update($this->sess_table_name,
			array(
				'last_activity' => $this->now,
				'session_id' => $this->userdata['session_id']
			)
		);

		// Write the cookie
		$this->_set_cookie();
	}

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

	/**
	 * Update database with current data
	 *
	 * This gets called from the shutdown function and also
	 * registered with PHP to run at the end of the request
	 * so it's guaranteed to update even when a fatal error
	 * occurs. The first call makes the update and clears the
	 * dirty flag so it won't happen twice.
	 *
	 * @return	void
	 */
	public function _update_db()
	{
		// Check for dirty flag and unsaved
		if ($this->data_dirty === TRUE && !empty($this->userdata['session_id']))
		{
			// Set up activity and data fields to be set
			// If we don't find custom data, user_data will remain an empty string
			$set = array(
				'last_activity' => $this->userdata['last_activity'],
				'user_data' => ''
			);

			// Get the custom userdata, leaving out the defaults
			// (which get stored in the cookie)
			$userdata = array_diff_key($this->userdata, $this->defaults);

			// Did we find any custom data?
			if ( ! empty($userdata))
			{
				// Serialize the custom data array so we can store it
				$set['user_data'] = serialize($userdata);
			}

			// Reset query builder values.
			$this->CI->db->reset_query();

			// Run the update query
			// Any time we change the session id, it gets updated immediately,
			// so our where clause below is always safe
			$this->CI->db->where('session_id', $this->userdata['session_id']);

			if ($this->sess_match_ip === TRUE)
			{
				$this->CI->db->where('ip_address', $this->CI->input->ip_address());
			}

			if ($this->sess_match_useragent === TRUE)
			{
				$this->CI->db->where('user_agent', trim(substr($this->CI->input->user_agent(), 0, 120)));
			}

			$this->CI->db->update($this->sess_table_name, $set);

			// Clear dirty flag to prevent double updates
			$this->data_dirty = FALSE;

			log_message('debug', 'CI_Session Data Saved To DB');
		}
	}

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

	/**
	 * Generate a new session id
	 *
	 * @return	string	Hashed session id
	 */
	protected function _make_sess_id()
	{
		$new_sessid = '';
		do
		{
			$new_sessid .= mt_rand();
		}
		while (strlen($new_sessid) < 32);

		// To make the session ID even more secure we'll combine it with the user's IP
		$new_sessid .= $this->CI->input->ip_address();

		// Turn it into a hash and return
		return md5(uniqid($new_sessid, TRUE));
	}

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

	/**
	 * Get the "now" time
	 *
	 * @return	int	 Time
	 */
	protected function _get_time()
	{
		if ($this->time_reference === 'local' OR $this->time_reference === date_default_timezone_get())
		{
			return time();
		}

		$datetime = new DateTime('now', new DateTimeZone($this->time_reference));
		sscanf($datetime->format('j-n-Y G:i:s'), '%d-%d-%d %d:%d:%d', $day, $month, $year, $hour, $minute, $second);

		return mktime($hour, $minute, $second, $month, $day, $year);
	}

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

	/**
	 * Write the session cookie
	 *
	 * @return	void
	 */
	protected function _set_cookie()
	{
		if (!$this->sessionFromDB) {
		  // Get userdata (only defaults if database)
		  $cookie_data = ($this->sessionFromDB === TRUE)
				  ? array_intersect_key($this->userdata, $this->defaults)
				  : $this->userdata;
  
		  // The Input class will do this and since we use HMAC verification,
		  // unless we standardize here as well, the hash won't match.
		  if ($this->_standardize_newlines)
		  {
			  foreach (array_keys($this->userdata) as $key)
			  {
				  $this->userdata[$key] = preg_replace('/(?:\r\n|[\r\n])/', PHP_EOL, $this->userdata[$key]);
			  }
		  }
  
		  // Serialize the userdata for the cookie
		  $cookie_data = serialize($cookie_data);
  
		  if ($this->sess_encrypt_cookie === TRUE)
		  {
			  $cookie_data = $this->CI->encryption->encrypt($cookie_data);
		  }
		  else
		  {
			  // Require message authentication
			  $cookie_data .= hash_hmac('sha1', $cookie_data, $this->encryption_key);
		  }
  
		  $expire = ($this->sess_expire_on_close === TRUE) ? 0 : $this->sess_expiration + time();
  
		  // Set the cookie
		  $this->_setcookie($this->sess_cookie_name, $cookie_data, $expire, $this->cookie_path, $this->cookie_domain,
			  $this->cookie_secure, $this->cookie_httponly);
		}
	}

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

	/**
	 * Set a cookie with the system
	 *
	 * This abstraction of the setcookie call allows overriding for unit testing
	 *
	 * @param	string	Cookie name
	 * @param	string	Cookie value
	 * @param	int	Expiration time
	 * @param	string	Cookie path
	 * @param	string	Cookie domain
	 * @param	bool	Secure connection flag
	 * @param	bool	HTTP protocol only flag
	 * @return	void
	 */
	protected function _setcookie($name, $value = '', $expire = 0, $path = '', $domain = '', $secure = FALSE, $httponly = FALSE)
	{
		setcookie($name, $value, $expire, $path, $domain, $secure, $httponly);
	}

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

	/**
	 * Garbage collection
	 *
	 * This deletes expired session rows from database
	 * if the probability percentage is met
	 *
	 * @return	void
	 */
	protected function _sess_gc()
	{
		$probability = ini_get('session.gc_probability');
		$divisor = ini_get('session.gc_divisor');

		if (mt_rand(1, $divisor) <= $probability)
		{
			$expire = $this->now - $this->sess_expiration;
			$this->CI->db->delete($this->sess_table_name, 'last_activity < '.$expire);

			log_message('debug', 'Session garbage collection performed.');
		}
	}

}

/* End of file Session_hybrid.php */
/* Location: ./system/libraries/Session/drivers/Session_hybrid.php */