Codeigniter random session logouts (Already tried override session class AND raising session_time_to_update

Question

I have tried both suggestions at: Codeigniter session bugging out with ajax calls

But even with $config[\'sess_time_to_update\'] = PHP_INT_MAX I am stil

Answer 1

I think you're suffering AJAX session race condition. I had the same problem, and I solved it overriding the CI session class. You have the article here:

https://web.archive.org/web/20181223212220/http://www.hiretheworld.com/blog/tech-blog/codeigniter-session-race-conditions

The cleanest thing would be use a MY_Session class, in your libraries folder, and then override the methods written in the link above. Sorry for the lack of indentation, :P

class MY_Session extends CI_Session
{
    public function __construct()
    {
        parent::__construct();
    }


/*********************************************************************
 * overrides to codeigniter session library
 *
 * Handle race condition during session_id updates.
 * - Keep the old session id around in case we have to handle race
 *   conditions.
 * - Changes are marked with the string "old_session_id_changes".
 *
 * session table changes:
 * ALTER TABLE `sessions` ADD COLUMN `old_session_id` VARCHAR(40)  DEFAULT NULL COMMENT 'old session id' AFTER `user_data`,
 *  ADD INDEX `old_session_id`(`old_session_id`);
 * DELETE FROM `sessions`;
 *********************************************************************/
 
/**
 * Fetch the current session data if it exists
 *
 * @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 === NULL)
  {
    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->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 = $this->_unserialize($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']))
  {
    $this->sess_destroy();
    return FALSE;
  }
 
  // Is the session current?
  if (($session['last_activity'] + $this->sess_expiration) < $this->now)
  {
    $this->sess_destroy();
    return FALSE;
  }
 
  // Does the IP match?
  if ($this->sess_match_ip === TRUE && $session['ip_address'] !== $this->CI->input->ip_address())
  {
    $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)))
  {
    $this->sess_destroy();
    return FALSE;
  }
 
  // Is there a corresponding session in the DB?
  if ($this->sess_use_database === TRUE)
  {
    /*
     * begin old_session_id_changes
     *
     * Search both session_id and old_session_id fields for the
     * incoming session id.
     *
     * used to be:
     * $this->CI->db->where('session_id', $session['session_id']);
     *
     * Manually create the OR condition because it causes the least
     * disturbance to existing code.
     *
     * Store the session id from the cookie so that we can see if we
     * came in through the old session id later.
     */
    $this->CI->db->where( '(session_id = ' . $this->CI->db->escape($session['session_id']) . ' OR old_session_id = ' . $this->CI->db->escape($session['session_id']) . ')' );
    $this->cookie_session_id = $session['session_id'];
    /*
     * end old_session_id_changes
     */
 
    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']);
    }
 
    $query = $this->CI->db->limit(1)->get($this->sess_table_name);
 
    // No result?  Kill it!
    if ($query->num_rows() === 0)
    {
      $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 = $this->_unserialize($row->user_data);
 
      if (is_array($custom_data))
      {
        foreach ($custom_data as $key => $val)
        {
          $session[$key] = $val;
        }
      }
    }
 
    /*
     * begin old_session_id_changes
     *
     * Pull the session_id from the database to populate the curent
     * session id because the old one is stale.
     *
     * Pull the old_session_id from the database so that we can
     * compare the current (cookie) session id against it later.
     */
    $session['session_id'] = $row->session_id;
    $session['old_session_id'] = $row->old_session_id;
    /*
     * end old_session_id_changes
     */
  }
 
  // Session is valid!
  $this->userdata = $session;
  unset($session);
 
  return TRUE;
}
 
// --------------------------------------------------------------------
 
/**
 * Write the session data
 *
 * @return  void
 */
public function sess_write()
{
  // Are we saving custom data to the DB?  If not, all we do is update the cookie
  if ($this->sess_use_database === FALSE)
  {
    $this->_set_cookie();
    return;
  }
 
  // set the custom userdata, the session data we will set in a second
  $custom_userdata = $this->userdata;
  $cookie_userdata = array();
 
  // Before continuing, we need to determine if there is any custom data to deal with.
  // Let's determine this by removing the default indexes to see if there's anything left in the array
  // and set the session data while we're at it
  foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
  {
    unset($custom_userdata[$val]);
    $cookie_userdata[$val] = $this->userdata[$val];
  }
 
  /*
   * begin old_session_id_changes
   *
   * old_session_id has its own field, but it doesn't need to go into
   * a cookie because we'll always retrieve it from the database.
   */
  unset($custom_userdata['old_session_id']);
  /*
   * end old_session_id_changes
   */
 
  // Did we find any custom data?  If not, we turn the empty array into a string
  // since there's no reason to serialize and store an empty array in the DB
  if (count($custom_userdata) === 0)
  {
    $custom_userdata = '';
  }
  else
  {
    // Serialize the custom data array so we can store it
    $custom_userdata = $this->_serialize($custom_userdata);
  }
 
  // Run the update query
  $this->CI->db->where('session_id', $this->userdata['session_id']);
  $this->CI->db->update($this->sess_table_name, array('last_activity' => $this->userdata['last_activity'], 'user_data' => $custom_userdata));
 
  // Write the cookie.  Notice that we manually pass the cookie data array to the
  // _set_cookie() function. Normally that function will store $this->userdata, but
  // in this case that array contains custom data, which we do not want in the cookie.
  $this->_set_cookie($cookie_userdata);
}
 
// --------------------------------------------------------------------
 
/**
 * Update an existing session
 *
 * @return  void
 */
public function sess_update()
{
  // We only update the session every five minutes by default
  if (($this->userdata['last_activity'] + $this->sess_time_to_update) >= $this->now)
  {
    return;
  }
 
  // _set_cookie() will handle this for us if we aren't using database sessions
  // by pushing all userdata to the cookie.
  $cookie_data = NULL;
 
  /*
   * begin old_session_id_changes
   *
   * Don't need to regenerate the session if we came in by indexing to
   * the old_session_id), but send out the cookie anyway to make sure
   * that the client has a copy of the new cookie.
   *
   * Do an isset check first in case we're not using the database to
   * store extra data.  The old_session_id field only exists in the
   * database.
   */
  if ((isset($this->userdata['old_session_id'])) &&
      ($this->cookie_session_id === $this->userdata['old_session_id']))
  {
    // set cookie explicitly to only have our session data
    $cookie_data = array();
    foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
    {
      $cookie_data[$val] = $this->userdata[$val];
    }
 
    $this->_set_cookie($cookie_data);
    return;
  }
  /*
   * end old_session_id_changes
   */
 
  // Save the old session id so we know which record to
  // update in the database if we need it
  $old_sessid = $this->userdata['session_id'];
  $new_sessid = '';
  do
  {
    $new_sessid .= mt_rand(0, mt_getrandmax());
  }
  while (strlen($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 update the session data array
  $this->userdata['session_id'] = $new_sessid = md5(uniqid($new_sessid, TRUE));
  $this->userdata['last_activity'] = $this->now;
 
  // Update the session ID and last_activity field in the DB if needed
  if ($this->sess_use_database === TRUE)
  {
    // set cookie explicitly to only have our session data
    $cookie_data = array();
    foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
    {
      $cookie_data[$val] = $this->userdata[$val];
    }
 
    /*
     * begin old_session_id_changes
     *
     * Save the old session id into the old_session_id field so that
     * we can reference it later.
     *
     * Rewrite the cookie's session id if there are zero affected rows
     * because that means that another request changed the database
     * under the current request.  In this case, we want to return a
     * value consistent with the previous request.  Reread immediately
     * after the update call here to minimize timing problems.  This
     * should be in a transaction for databases that support them.
     *
     * Also rewrite the userdata so that future calls to sess_write
     * will output the correct cookie data.
     *
     * used to be:
     * $this->CI->db->query($this->CI->db->update_string($this->sess_table_name, array('last_activity' => $this->now, 'session_id' => $new_sessid), array('session_id' => $old_sessid)));
     */
    $this->CI->db->query($this->CI->db->update_string($this->sess_table_name, array('last_activity' => $this->now, 'session_id' => $new_sessid, 'old_session_id' => $old_sessid), array('session_id' => $old_sessid)));
 
    if ($this->CI->db->affected_rows() === 0)
    {
      $this->CI->db->where('old_session_id', $this->cookie_session_id);
      $query = $this->CI->db->get($this->sess_table_name);
 
      // We've lost track of the session if there are no results, so
      // don't set a cookie and just return.
      if ($query->num_rows() == 0)
      {
        return;
      }
 
      $row = $query->row();
      foreach (array('session_id','ip_address','user_agent','last_activity') as $val)
      {
        $this->userdata[$val] = $row->$val;
        $cookie_data[$val] = $this->userdata[$val];
      }
 
      // Set the request session id to the old session id so that we
      // won't try to regenerate the cookie again on this request --
      // just in case sess_update is ever called again (which it
      // shouldn't be).
      $this->cookie_session_id = $this->userdata['old_session_id'];
    }
    /*
     * end old_session_id_changes
     */
  }
 
  // Write the cookie
  $this->_set_cookie($cookie_data);
}
 
/*********************************************************************
 * end overrides to codeigniter session library
 *********************************************************************/