Citrix Metaframe Presentation Server bypassing policies

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Date: Fri, 30 Sep 2005 14:58:53 -0300 (ART)
To: bugtraq@securityfocus.com, vuln-dev@securityfocus.com, pen-test@securityfocus.com

DESCRIPTION:
============

Vulnerability in Presentation Server allow to user bypass citrix policy
which is applied to client name.

SOFTWARE: Citrix Metaframe Presentation Server 3.0 / 4.0
=========

INFO:
=====

Citrix Presentation Server policy is used for admins to restrict the user
environment
and these allow applying to: IP client, servers, Users, o Client Name.

When user used the Web Interface to access to application in citrix
environment
the CLIENT NAME used is WI_*, where (*) is a random value like
asdfserw34vc342dk
this extension allow admins to use citrix policy based in client name "WI_*"
This policy can be used to restrict "printing Mapping, Disk Mapping,
Control bandwidth, manage printer driver environment so..."

VULNERABILITY:
==============

When user uses the application in Web interface, he download and execute
automatic file "launch.ica"

If the user "save as" launch.ica in his pc, and edit with notepad
He can change the value in ClientName that another "WI_" and execute

When user connects to citrix with ica file modified to Presentation
Server, the value in clientname is different to the original one and
bypasses the citrix policies.

POC:
====

Here is an example extracted from launch.ica:

[Encoding]

InputEncoding=ISO8859_1

[WFClient]

Version=2

ClientName=WI_XXXX -> change this extension with other name to bypass the
citrix policies

TransportReconnectEnabled=On

RemoveICAFile=yes

ProxyType=None

ProxyTimeout=30000

VENDOR STATUS:
==============

http://support.citrix.com/kb/entry!default.jspa?categoryID=275&externalID=CTX107705

FIX:
====

No Hotfix released

CREDITS:
========

This vulnerability was discovered and researched by
Gustavo Gurmandi of GrupoITPro Security Research Community.

mail : gustavog@grupoiptro.com.ar

web : http://www.grupoitpro.com.ar

ORIGINAL ADVISORY:
==================

http://www.grupoitpro.com.ar/ctxpoliciesbypass.txt

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