Path Traversal on Polycom Web Management Interface

Neste post reproduzimos um advisory (nota técnica) detalhando uma vulnerabilidade que descobrimos na interface web de gerenciamento em um dos produtos de teleconferência da Polycom. A vulnerabilidade viabiliza o acesso a quaisquer arquivos no filesystem do ativo afetado.

O advisory (em inglês) contendo os detalhes completos dessa vulnerabilidade está listado a seguir:

=====[ Tempest Security Intelligence - Advisory #01 / 2012 ]==================
 
     Path Traversal on Polycom Web Management Interface
     --------------------------------------------------

Authors:
    - Heyder Andrade:
        - @heyderandrade
	- http://linkedin.com/in/heyderandrade
        - < heyder.andrade[at]tempest[dot]com[dot]br >
    - Joao Paulo Caldas Campello:
        - @jpcampello
	- http://linkedin.com/in/jpcampello
        - < joao.paulo[at]tempest[dot]com[dot]br >

    Tempest Security Intelligence - Recife, Pernambuco - Brazil 
 
=====[ Table of Contents ]====================================================

 1. Overview
 2. Detailed description
 3. Aggravating factors
 4. Affected versions & Solutions
 5. Timeline of disclosure 
 6. Thanks & Acknowledgements
 7. References

=====[ Overview ]=============================================================
 
 * System affected  : Polycom Web Management Interface
 * Model            : G3/HDX 8000 HD
                      
 * Software Version : Durango 2.6.0 Release - build #4740
 * Embedded Linux   : Polycom Linux Development Platform v2.14.g3

                      Other versions or models may also be affected.
                      
 * Impact           : Successful exploitation of this vulnerability may
                      allow an attacker to view content of any arbitrary
                      file on Polycom operating system.

The Polycom HDX 8000 series [1] is a well-known video and audio 
conference device running an embedded Linux PPC system.

This advisory is also available at:

 - http://www.tempest.com.br/advisories/tsi-adv-1201/
 
=====[ Detailed description ]=================================================

The web management interface on the Polycom device allows users to download
two log files ("system log" and "error log"). This feature is available
through the following menus:

    Diagnostics --> System Log --> Download Logs

The access to these log files is provided by the script "a_getlog.cgi", which
receives the name of the log file ("messages" or "error") to be downloaded
through URL parameter "name", as shown on the above URL:

    - http://<affected_device>/a_getlog.cgi?name=messages

The Path Traversal vulnerability occurs due to lack of proper input validation
on user supplied data.

This vulnerability allows the attacker to navigate in the directory structure,
thus enabling access to arbitrary files in Polycom's operating system.

As a proof-of-concept, it's possible to download "/etc/passwd" file accessing
the following URL:

    - http://<affected_device>/a_getlog.cgi?name=../../../etc/passwd

To fix this vulnerability, Polycom Web Management Interface should perform
proper input validation, sanitizing all user supplied data before it's used
elsewhere on the web application or in the underlying operating system.

Also, Polycom Web Management Interface should not allow itself to be accessed
without proper configuration of a strong administrative password.

=====[ Aggravating factors ]==================================================

During system lab testing the following aggravating factors were observed:

    01. The default administrative password of Polycom Web Management
        Interface was empty.

    02. The embedded web server (lighttpd) was running with superuser
        privileges, allowing access to any arbitrary files on the filesystem.

=====[ Affected versions & Solutions ]========================================

According to vendor's response, Polycom will publish Technical Bulletin 85802
to its costumers, reporting their official solution and mitigation information.

They have also informed that this vulnerability affects the following
products:

- Polycom HDX Video End Points running software version 2.6 and earlier.

Customers can download version 3.0 and newer at the link provided below:

- http://support.polycom.com/PolycomService/support/us/support/video/hdx_series/

For customers who cannot update to version 3.0, Polycom recommends sysadmins
to disable the option for web management on HDX units running versions 2.6
and older.

=====[ Timeline of disclosure  ]==============================================

 - Dec/02/2011: Vendor contacted by e-mail on < security[at]polycom[dot]com >.

 - Dec/02/2011: Vendor first response.

 - Dec/28/2011: We have sent another e-mail asking for information.

 - Feb/15/2012: As vendor did not reply to our previous message, we have
                sent another e-mail telling we were going to disclose the
                advisories.

 - Feb/15/2012: Vendor responded asking for some more time to verify
                appropriate fixes and mitigations to vulnerabilities.

                We have agreed on releasing the advisories on two weeks.

 - Feb/29/2012: Vendor sent an email reporting the technical bulletins
		which describe their official solution and mitigation
                information they were going to provide to their costumers.

 - Mar/01/2012: Tempest and Polycom have coordinated publication date on
                March 05.

 - Mar/05/2012: Public disclosure of advisories.

=====[ Thanks & Acknowledgements ]============================================
 
 - Tempest Security Intelligence / Tempest's Pentest Team [2]
 - Evandro Hora < evandro[at]tempest[dot]com[dot].br >
 - Joaquim Brasil < joaquim.brasil[at]tempest[dot]com[dot].br >
 - Ricardo Ulisses < ricardo[at]tempest[dot]com[dot].br >
 
=====[ References ]===========================================================
 
 [1] http://www.polycom.com/
 [2] http://www.tempest.com.br/
 
==============================================================================

Comentários
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Pedro Lima | 2012-03-11 22:13:10 | permalink | topo

Bons tempos que a tempest lançava Advs em iptables etc! tsc tsc tsc!

Victor Hora | 2012-03-06 16:17:44 | permalink | topo

+1.

Marco Carnut | 2012-03-05 11:02:31 | permalink | topo

Jopa,

Parabéns a você e à equipe pelos advisories. Redação irretocável.

O que eu acho de lascar foram os mais de 90 dias de estica-e-puxa pro fabricante se coçar, resolver o problema e concordar com a publicação das vulnerabilidades. Puxa, é uma vulnerabilidade simples, clássica... não tem por que a solução levar mais do que um dia... mesmo considerando um processo de software pesadíssimo, não teria por que levar mais do que uma semana. Três meses é injustificável – quem perde é o consumidor, que ficou três meses vulnerável sem saber.

É por isso que eu tenho meus sérios senões com esse modelo de "publicação retardada" que se convencionou chamar de "liberação responsável" ("responsible disclosure"). Quem é mais irresponsável?: o engenheiro de software que deixa uma vulnerabilidade dessas sair no produto final ou o pesquisador que acha, documenta e avisa?

Em todo caso, parabéns novamente. "Keep up the good work", como dizem os americanos.

-K.