[SECURITY-L] CAIS-Alerta: Duas vulnerabilidades no OpenSSL

Sex Mar 19 09:06:59 -03 2004

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From: Centro de Atendimento a Incidentes de Seguranca <cais em cais.rnp.br>
Subject:  CAIS-Alerta: Duas vulnerabilidades no OpenSSL
To: rnp-alerta em cais.rnp.br, rnp-seg em cais.rnp.br
Date: Thu, 18 Mar 2004 16:34:42 -0300 (BRST)

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Prezados,

O CAIS esta' repassando os alertas divulgados pelo OpenSSL, intitulados
"Null-pointer assignment during SSL handshake" e "Out-of-bounds read
affects Kerberos ciphersuites", tratando de duas vulnerabilidades nas
versoes atuais da biblioteca OpenSSL que podem causar negacao de servico
(DoS - Denial of Service) em programas que a utilizam.

A primeira vulnerabilidade afeta uma funcao do protocolo TLS, e pode
permitir a um atacante remoto ocasionar a negacao de servico em
aplicativos que utilizam a biblioteca OpenSSL, apenas enviando um pacote
especialmente construido que causa um erro de null-pointer.

A segunda vulnerabilidade afeta o processo de handshake do protocolo
SSL/TLS quando se utiliza criptografia Kerberos. Um atacante remoto pode
criar um pacote de handshake especialmente construido de forma a resultar
na negacao de servico em aplicativos que utilizam a biblioteca OpenSSL.

Sistemas afetados:

. Qualquer programa que utilize as versoes entre 0.9.6c até 0.9.6l e
  0.9.7a até 0.9.7c da bibliotecas OpenSSL pode ser afetado por essa
  vulnerabilidade.

Correcoes disponiveis:

Recomenda-se fazer a atualizacao para as versoes mais recentes disponiveis
em:

. OpenSSL 0.9.7d
ftp://ftp.openssl.org/source/openssl-0.9.7d.tar.gz

. OpenSSL 0.9.6m
ftp://ftp.openssl.org/source/openssl-0.9.6m.tar.gz

Alem disso, recomenda-se recompilar todos os aplicativos que foram
compilados estaticamente com a biblioteca OpenSSL.

Maiores informacoes:

. OpenSSL Security Advisory
http://www.openssl.org/news/secadv_20040317.txt

. Cisco Security Advisory: Cisco OpenSSL Implementation Vulnerability
http://www.cisco.com/warp/public/707/cisco-sa-20040317-openssl.shtml

Identificadores do CVE (http://cve.mitre.org):

. Null-pointer assignment during SSL handshake: CAN-2004-0079
. Out-of-bounds read affects Kerberos ciphersuites: CAN-2004-0112

O CAIS recomenda aos administradores manterem seus sistemas e aplicativos
sempre atualizados, de acordo com as ultimas versoes e correcoes
disponibilizadas pelos fabricantes.

Atenciosamente,

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OpenSSL Security Advisory [17 March 2004]

Updated versions of OpenSSL are now available which correct two
security issues:

1. Null-pointer assignment during SSL handshake
===============================================

Testing performed by the OpenSSL group using the Codenomicon TLS Test
Tool uncovered a null-pointer assignment in the
do_change_cipher_spec() function.  A remote attacker could perform a
carefully crafted SSL/TLS handshake against a server that used the
OpenSSL library in such a way as to cause OpenSSL to crash.  Depending
on the application this could lead to a denial of service.

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2004-0079 to this issue.

All versions of OpenSSL from 0.9.6c to 0.9.6l inclusive and from
0.9.7a to 0.9.7c inclusive are affected by this issue.  Any
application that makes use of OpenSSL's SSL/TLS library may be
affected.  Please contact your application vendor for details.

2. Out-of-bounds read affects Kerberos ciphersuites
===================================================

Stephen Henson discovered a flaw in SSL/TLS handshaking code when
using Kerberos ciphersuites.  A remote attacker could perform a
carefully crafted SSL/TLS handshake against a server configured to use
Kerberos ciphersuites in such a way as to cause OpenSSL to crash.
Most applications have no ability to use Kerberos ciphersuites and
will therefore be unaffected.

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2004-0112 to this issue.

Versions 0.9.7a, 0.9.7b, and 0.9.7c of OpenSSL are affected by this
issue.  Any application that makes use of OpenSSL's SSL/TLS library
may be affected.  Please contact your application vendor for details.

Recommendations
- ---------------

Upgrade to OpenSSL 0.9.7d or 0.9.6m.  Recompile any OpenSSL applications
statically linked to OpenSSL libraries.

OpenSSL 0.9.7d and OpenSSL 0.9.6m are available for download via HTTP and
FTP from the following master locations (you can find the various FTP
mirrors under http://www.openssl.org/source/mirror.html):

    ftp://ftp.openssl.org/source/

The distribution file names are:

    o openssl-0.9.7d.tar.gz
      MD5 checksum: 1b49e90fc8a75c3a507c0a624529aca5

    o openssl-0.9.6m.tar.gz [normal]
      MD5 checksum: 1b63bfdca1c37837dddde9f1623498f9
    o openssl-engine-0.9.6m.tar.gz [engine]
      MD5 checksum: 4c39d2524bd466180f9077f8efddac8c

The checksums were calculated using the following command:

    openssl md5 openssl-0.9*.tar.gz

Credits
- -------

Patches for these issues were created by Dr Stephen Henson
(steve em openssl.org) of the OpenSSL core team.  The OpenSSL team would
like to thank Codenomicon for supplying the TLS Test Tool which was
used to discover these vulnerabilities, and Joe Orton of Red Hat for
performing the majority of the testing.

References
- ----------

http://www.codenomicon.com/testtools/tls/
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0079
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0112

URL for this Security Advisory:
http://www.openssl.org/news/secadv_20040317.txt

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