Digi-news and Digi-ads v1.1 admin access without password

Overview

Digi-news and Digi-ads version 1.1 admin access without password
Discovered on 2003, March, 30th
Vendor: Digi-FX

Digi-news 1.1 is a PHP news editor. It allows you to easily add, edit, and delete news.
Digi-ad 1.1 is a PHP ad rotator. It allows you to easily add, edit, reset, and delete ads.
A vulnerability allows to access to the admin area in both script, without the administrator password.

Risk

Exploit easiness
Vulnerability spreading
Impact
Risk

Details

In Digi-news or Digi-ad, the admin web page is admin.php
Here is a sample of the admin authentification in this admin.php :

if (!isset($action)) {
   $action = '';
}
if ($action == 'auth') {
   auth();
}
if ((@$HTTP_COOKIE_VARS['user'] != $digiNews['user']) && (@$HTTP_COOKIE_VARS['pass'] != md5($digiNews['pass']))) {
   login();
   exit;
}
Continued as admin logged...

As you can see, the authentification scheme is based on a cookie. This cookie contains the user and the MD5 hashed password. But the programmer did a mistake :
if ((@$HTTP_COOKIE_VARS['user'] != $digiNews['user']) && (@$HTTP_COOKIE_VARS['pass'] != md5($digiNews['pass']))) {
It means that "Admin is authentificated" if "user = user in the cookie" OR "password = password in the cookie". In english, it means you don't need the admin password as far as you know the admin login !
The default admin login is "admin". If it doesn't work, try these :

Admin
Administrator
administrator
Root
root
the nickname of the admin (if known)
the surname of the admin (if known)
etc...

Exploit

Ok, that's quite easy. You just have to send a handwrited cookie with user=admin in. You can do that with the well-known Proxomitron. Here is a proof of concept :

Regular HTTP GET command

You get the authentification page

Personalized HTTP GET command with the "user" cookie

You get the admin page !

Solution

The solution is to replace the AND operation by a OR operation, as followed :
if ((@$HTTP_COOKIE_VARS['user'] != $digiNews['user']) || (@$HTTP_COOKIE_VARS['pass'] != md5($digiNews['pass']))) {
The vendor has been informed and solved the problems. Download Digi-News 1.2 and Digi-ads 1.2