Digital Armaments Security Advisory 01.09.2006: Apache auth_ldap module Multiple Format Strings Vulnerability

[info () digitalarmaments com]

Digital Armaments advisory is 12.22.2005
http://www.digitalarmaments.com/2006090173928420.html

I. Background

auth_ldap is an LDAP authentication module for Apache, the world's most popular web server. auth_ldap has excellent 
performance, and supports Apache on both Unix and Windows NT. It also has support for LDAP over SSL, and a mode that 
lets Microsoft Frontpage clients manage their web permissions while still using LDAP for authentication. 
For many information or detail about the software you can refer to the vendor's homepage:

http://www.rudedog.org/auth_ldap/

II. Problem Description

Due to an insecure usage of the function apache logging function (ap_log_rerror) in auth_ldap_log_reason function it's 
possible to run abitrary code on the server running the module. For example this can generate a custom format string 
that can be supplied by the attacker throught the username given during the apache authentication process but several 
parts of the module are affected. 

III. Detection

This problem has been detected on latest version of auth_ldap 1.6.0 and on prior version from 1.2.x. It persist on all 
platforms where auth_ldap can be compiled.

IV. Impact analisys

Successful exploitation allow an attacker to gain access to the system. Exploit code is required.

V. Solution

First notification 12.22.2005.
Second notification 01.09.2006.
The vendor answered second notification.
A new patched version will be available.

VI. Credit

Seregorn - seregon () bughunter net is credited with this discovery.

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