Hi,

As everyone knows, php build in Session management is not really secure:

(1) storing of session in /tmp can allow other virtual hosts to access the session data
(2) intercepting the SID passed by url can allow the hacker to login in with it
(3) intercepting the cookie does the same
As a workaround, it will be nice to store the data in a mySQL table, disallow the use of
session.use_trans_sid and do a check on user IP address to see if it match the one used
on sesssion open.

As I really like the way work built in PHP4 Sessions (accessing vars throw $_SESSION) I have
decided to replace the session handler to do the staff and then I could continue to use my
scripts with only replacing session_start() by a function call and by including a file.

You can download the script from there: http://www.keasyphp.org/php/Sessions


<?
/* ------------------------------------------------------------------------
 * session_mysql.inc.php
 * ------------------------------------------------------------------------
 * PHP4 MySQL Session Handler
 * Version 1.0.0
 * Last Modified: 5 Feb 2003
 *
 * Copyright (C) 2003  Laurent DINCLAUX (root@KeasyPHP.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.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * ------------------------------------------------------------------------
 * DESCRIPTION:
 * ------------------------------------------------------------------------
 * This library tells the PHP4 session handler to write to a MySQL database
 * instead of creating individual files for each session.
 * In fact it is quite secure as it can do a check against ip. This avoid
 * hacking of the cookie containing session_id by its intercept and use
 * on an other computer. It retrives firewall ip and client ip too.
 * It also has default value to override session.use_trans_sid so it disabale
 * use it as it is not secure at all.
 *
 * ------------------------------------------------------------------------
 * INSTALLATION:
 * ------------------------------------------------------------------------
 * Create a new database in MySQL called "sessions" like so:
 *
 *CREATE TABLE $_sess_tblPrefix_sessions (
 *   session_id varchar(32) NOT NULL default '',
 *   session_created int(11) NOT NULL default '0',
 *   session_active int(11) NOT NULL default '0',
 *   session_counter int(11) NOT NULL default '0',
 *   session_remote_address varchar(128) NOT NULL default '',
 *   session_data longtext NOT NULL
 *) TYPE=MyISAM;
 *
 * Then call sess_init($DB_host, $DB_base, $DB_user, $DB_password,$_sess_tblPrefix) to open
 * session note that this function has many other arguments that are used to
 * override php.ini session_setting they have default value so check them
 * at the end of the script and the php documentation for explanations
 * http://www.php.net/manual/en/ref.session.php
 */

$_sqlLink = '';
$_sess_data_max = '';
$_sess_ip_check = '';
$_sess_tblPrefix = '';
$_sess_property= '';

/**
 *This function retrive the more detailed info possible on client IP adress
 */
function get_full_ip(){
    // get client real ip
    if ($_SERVER['HTTP_X_FORWARDED_FOR']):
        $IP_ADDR = $_SERVER['HTTP_X_FORWARDED_FOR'] ;
    elseif($_SERVER['HTTP_CLIENT_IP']):
        $IP_ADDR =  $_SERVER['HTTP_CLIENT_IP'] ;
    else:
        $IP_ADDR = $_SERVER['REMOTE_ADDR'];
    endif;

    // get server ip and resolved it
    $FIRE_IP_ADDR = $_SERVER['REMOTE_ADDR'];
    $ip_resolved = gethostbyaddr($FIRE_IP_ADDR);

    // builds server ip infos string
    if ($FIRE_IP_ADDR != $ip_resolved && $ip_resolved):
        $FIRE_IP_LITT = $FIRE_IP_ADDR." - ". $ip_resolved;
    else:
        $FIRE_IP_LITT = $FIRE_IP_ADDR;
    endif;

    // builds client ip full infos string
    if ($IP_ADDR != $FIRE_IP_ADDR  ):
        $FULL_IP_INFOS = "$IP_ADDR | $FIRE_IP_LITT" ;
    else:
        $FULL_IP_INFOS = $FIRE_IP_LITT ;
    endif;
    return $FULL_IP_INFOS;

}

/**
 *Called by session_start()
 *only opens a Mysql connection
 */
function sess_open($save_path, $_session_name) {
    global $DB_host, $DB_base, $DB_user, $DB_password, $_sqlLink;

    if (! $_sqlLink =@ mysql_connect($DB_host, $DB_user, $DB_password)) {
        trigger_error('sess_open(): Failed to connect to MySql - '. mysql_error($_sqlLink),E_USER_ERROR);
        return false;
    }
    if (! @mysql_select_db($DB_base, $_sqlLink)) {
        trigger_error("sess_open(): Unable to select database $DB_base - ". mysql_error($_sqlLink),E_USER_ERROR);
        return false;
    }
    return true;
}

function sess_close() {
    return true;
}

/**
 *Reads session data in mySql
 *also do an ip check
 */
function sess_read($session_id) {
    global $_sqlLink, $_sess_property, $_sess_tblPrefix, $_sess_ip_check;

    //session_id check
    if (strlen($session_id) != 32) {
        trigger_error("sess_read(): Invalid SessionID = " . $session_id,E_USER_ERROR);
        return '';
    }

    $session_id = addslashes($session_id);
    $result = mysql_query("SELECT * FROM {$_sess_tblPrefix}_sessions WHERE session_id = '$session_id'",$_sqlLink);
    if (@mysql_num_rows($result) == 1) {
        $_sess_property= mysql_fetch_assoc($result);
        return $_sess_property['session_data'];
        // ip check
        if(!$_sess_ip_check and $_sess_property){
            return $_sess_property['session_data'];
        }
        else if($_sess_property and $_sess_property['session_remote_address']==get_full_ip() and $_sess_ip_check){
            return $_sess_property['session_data'];
        }
        else{
           echo "<DIV align=center><font face=verdana size=1>Session Error
Your IP address has changed...
'".get_full_ip()."'
'{$_sess_property['session_remote_address']}'
Remember: hacking is not good for your health !</font></div>"; session_destroy(); exit; return ''; } } elseif (mysql_errno($_sqlLink)) { trigger_error('sess_read(): Failed to read sessions - '. mysql_error($_sqlLink),E_USER_ERROR); return ''; } else { $_sess_property = null; // For session_write() return ''; } } /** *Write session data in mySql *also do an ip check */ function sess_write($session_id, $session_data) { global $_sqlLink, $_sess_property, $_sess_tblPrefix, $_sess_data_max, $_sess_ip_check; //session_id check if (strlen($session_id) != 32) { trigger_error('sess_write(): Invalid Session ID = '.$session_id,E_USER_ERROR); return false; } //session data max size check if ($_sess_data_max > 0 and strlen($session_data) > intval($_sess_data_max)) { trigger_error('sess_write(): Session data too large. '. $session_id, E_USER_ERROR); } // ip check if($_sess_property and $_sess_property['session_remote_address']!=get_full_ip() and $_sess_ip_check){ echo get_full_ip()."<DIV align=center><font face=verdana size=1>Session Error
Your IP address has changed...
'".get_full_ip()."'
'{$_sess_property['session_remote_address']}'
Remember: hacking is not good for your health !</font></div>"; session_destroy(); exit; return ''; } // escape session_data to be insert in Mysql if(version_compare(phpversion(), "4.3.0", "<")){ $_sess_data = mysql_escape_string($session_data); } else{ $_sess_data = mysql_real_escape_string($session_data); } //UPDATE/INSERT data if ($_sess_property) { $query = "UPDATE {$_sess_tblPrefix}_sessions SET session_active = ". time() .", session_counter = ". ++$_sess_property['session_counter'] .", session_data = '$_sess_data' WHERE session_id = '$session_id';"; } else { $query = "INSERT INTO {$_sess_tblPrefix}_sessions (session_id, session_created, session_active, session_remote_address, session_data) VALUES ('$session_id', ". time() .", ". time() .", '". get_full_ip() ."', '$_sess_data');"; } mysql_query($query, $_sqlLink); if (mysql_errno($_sqlLink)) { trigger_error('sess_write(): Failed to INSERT/UPDATE session. '.mysql_error($_sqlLink). "
Query: ".$query,E_USER_ERROR); } return true; } /** *detroys the session */ function sess_destroy($session_id) { global $_sqlLink, $_sess_tblPrefix; mysql_query("DELETE FROM {$_sess_tblPrefix}_sessions WHERE session_id = '". addslashes($session_id). "'",$_sqlLink); if (mysql_errno($_sqlLink)) { trigger_error('sess_destory(): Failed to DELETE session. '.mysql_error($_sqlLink),E_USER_ERROR); return false; } else { return true; } } /** *delete old sessions */ function sess_gc($_sess_gc_maxlifetime=20) { /** *you may want to uncomment this to test if garbage *collection get called properly */ /* $fp =fopen('gc.txt',ab); fwrite ($fp,"gc\n"."DELETE FROM {$_sess_tblPrefix}_sessions WHERE session_active < ". (time() - $_sess_gc_maxlifetime)); fclose($fp); */ global $_sqlLink, $_sess_tblPrefix; mysql_query("DELETE FROM {$_sess_tblPrefix}_sessions WHERE session_active < ". (time() - $_sess_gc_maxlifetime)); mysql_query("OPTIMIZE TABLE `{$_sess_tblPrefix}_sessions` ",$_sqlLink); if (mysql_errno($_sqlLink)) { trigger_error('sess_gc(): Failed to DELETE old sessions.'. mysql_error($_sqlLink),E_USER_WARNING); return false; } else { return true; } } /** *initaializing session function *call that to open session */ function sess_init($DB_host, $DB_base, $DB_user, $DB_password, $session_tblPrefix, //vars to connect to mysql $session_ip_check = true, // do an ip check ? $session_data_max = 0, // max lenght of session data (0 for unlimited) $session_name="PHPSESSID", $session_serialize_handler = 'php', $session_gc_probability = 50, $session_gc_maxlifetime = 1440, $session_referer_check ='', $session_entropy_file = '', $session_entropy_length = 0, $session_use_cookies = 1, $session_use_only_cookies = 1, // only available from php 4.3.0 $session_cookie_lifetime = 0, $session_cookie_secure = false, // automaticly set if you use https connection but you can force it to true $session_cookie_path = '/', $session_cookie_domain = '', $session_cache_limiter = 'nocache', // none, nocache, private, private_no_expire, public $session_cache_expire = 180, $session_use_trans_sid = 0, $sesssion_url_rewriter_tags = 'a=href,area=href,frame=src,input=src,form=fakeentry') { global $DB_host, $DB_base, $DB_user, $DB_password, $_sess_tblPrefix, $_sess_ip_check, $_sess_data_max, $_sess_gc_maxlifetime; $_sess_data_max = $session_data_max; $_sess_ip_check = $session_ip_check; $_sess_tblPrefix = $session_tblPrefix; // have to or the staff won't work ini_set ( "session.save_handler", "user" ); // set the cookie secure if HTTPS is on if($_SERVER["HTTPS"] == "on" or $session_cookie_secure) $session_cookie_secure = true; session_name($session_name); ini_set ( "session.serialize_handler", $session_serialize_handler ); ini_set ( "session.gc_probability", $session_gc_probability ); ini_set ( "session.gc_maxlifetime", $session_gc_maxlifetime ); ini_set ( "session.referer_check", $session_referer_check ); ini_set ( "session.entropy_file", $session_entropy_file); ini_set ( "session.entropy_length", $session_entropy_length ); ini_set ( "session.use_cookies", $session_use_cookies ); if(version_compare(phpversion(), "4.3.0", ">=")) ini_set ( "session.use_only_cookies", $session_use_only_cookies ); session_set_cookie_params ( $session_cookie_lifetime,$session_cookie_path,$session_cookie_domain,$session_cookie_secure); session_cache_expire ($session_cache_expire); session_cache_limiter($session_cache_limiter); ini_set ( "session.use_trans_sid", $session_use_trans_sid ); ini_set ( "session.url_rewriter.tags ", $sesssion_url_rewriter_tags ); $_sess_gc_maxlifetime = ini_get("session.gc_maxlifetime"); session_start(); } session_set_save_handler( "sess_open", "sess_close", "sess_read", "sess_write", "sess_destroy", "sess_gc"); ?>