source: sandbox/workflow/branches/609/lib/security/Security.php @ 2249

<?php
/**************************************************************************\
* eGroupWare                                                               *
* http://www.egroupware.org                                                *
* --------------------------------------------                             *
*  This program is free software; you can redistribute it and/or modify it *
*  under the terms of the GNU General Public License as published by the   *
*  Free Software Foundation; either version 2 of the License, or (at your  *
*  option) any later version.                                              *
\**************************************************************************/

/**
 * Security class for Workflow module.
 * You should never forget to call 'enable'
 * public method to enable security before
 * executing process code.
 *
 * @package Security
 * @license http://www.gnu.org/copyleft/gpl.html GPL
 * @author Pedro Eugênio Rocha - pedro.eugenio.rocha@gmail.com
 */
class Security {

        /**
         * @var boolean $_protection Stores the current security mode.
         * @access private
         * @static
         */
        private static $_protection = false;


        /**
         * Disallow the instantiation of this class.
         * @access public
         * @return void
         */
        public function __construct() {
                throw new Exception("Oops! Static only class.");
        }


        /**
         * Returns the current security mode.
         * @access public
         * @return boolea
         * @static
         */
        public static function isEnabled() {
                return self::$_protection;
        }


        /**
         * Change to secured mode.
         * @access public
         * @return boolean
         * @static
         */
        public static function enable() {

                if (self::isSafeDir())
                        self::$_protection = true;
                else
                        throw new Exception('You are not allowed to change the security mode.');
                return true;
        }

        /**
         * Change to unsecured mode.
         * @access public
         * @return boolean
         * @static
         */
        public static function disable() {

                if (self::isSafeDir())
                        self::$_protection = false;
                else
                        throw new Exception('You are not allowed to change the security mode.');
                return true;
        }


        /**
         * Implements the security validation.
         * This function tell us if a fileName is on a safe directory.
         * For safe dir we mean that no process code exists under it.
         * The 'depth' parameter specifies the deepness of the file that
         * we are validate. Default value is to validate the imediate
         * previous function.
         *
         * @access public
         * @return boolean
         * @static
         */
        public static function isSafeDir($depth = 1) {

                /* our backtrace based policy */
                $backtrace = debug_backtrace();
                $originFile = $backtrace[$depth]['file'];

                if (empty($originFile))
                        return false;

                /* if $fileName is a file under our server root, then it's safe. */
                if (substr_compare($originFile, EGW_SERVER_ROOT, 0, strlen(EGW_SERVER_ROOT)) == 0)
                        return true;
                return false;
        }


        /**
         * This function do all the security stuff.
         * Here we must define in which files we are able
         * to change the security mode.
         *
         * @access private
         * @return boolean
         * @static
         */
        private static function _isAllowed() {
                $backtrace = debug_backtrace();


                /* $backtrace[1] specifies the imediate antecessor function */
                $originFile = basename($backtrace[1]['file']);


                /**
                 * TODO - TODO - TODO - TODO
                 * We all know that compare file names is a awful thing..
                 * what makes it even worse is the fact that the file name
                 * could contain double slashes (e.g. //) caused by wrong
                 * concatenations. So we cannot compare the whole file path.
                 * Moreover, if the process has a file named $allowedFile,
                 * our security will eventually fail..
                 *
                 * Anyway, we should think in a better way to validate this...
                 */
                if (basename($originFile) == basename($allowedFile))
                        return true;
                return false;
        }
}
?>