Conectiva Linux Advisory: gnupg

CONECTIVA LINUX SECURITY ANNOUNCEMENT

DESCRIPTION
GnuPG[1] is an OpenPGP-compliant tool for secure communication used
to, for example, sign emails, encrypt, decrypt and verify (signed)
data.

Phong Nguyen discovered[2] a vulnerability (CAN-2003-0971[3]) in
the way GnuPG deals with type 20 ElGamal sign+encrypt keys which
allows an attacker to recover the corresponding private key from a
signature. Other keys, such as ElGamal type 16 used only for
encryption, are not affected.

This is a serious vulnerability with immediate impact: all
ElGamal type 20 keys should be revoked and considered to be
compromised, as well as data signed or encrypted with such a
key.

Please note that:

• by default, GnuPG does not generate this type of key;
• in order to create an ElGamal type 20 key, one must (in recent
  versions of GnuPG) add the –expert command line option, and even
  then a warning is given saying that this key should not be used. In
  older versions, only the warning is given.

To identify the vulnerable type 20 ElGamal keys, look for the
“G” identifier in a key listing such as the example below:

pub 2048G/xxxxxxxx 2001-01-05 John Doe <John@doe.net>

Other keys (including the ones identified by “g”, lower case)
are not affected.

The packages provided with this update have a patch[4] created
by David Shaw which disables the creation of these keys and no
longer allows them to be used to create signatures.

SOLUTION
It is recommended that all GnuPG users upgrade their packages.
Additionally, users who have ever created ElGamal type 20
sign+encrypt keys should revoke them and consider them to be
compromised, as well as data signed or encrypted with such a
key.

REFERENCES
1.http://www.gnupg.org/
2.http://lists.gnupg.org/pipermail/gnupg-announce/2003q4/000276.html

3.http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0971

4.http://lists.gnupg.org/pipermail/gnupg-announce/2003q4/000277.html

UPDATED PACKAGES

ftp://atualizacoes.conectiva.com.br/8/SRPMS/gnupg-1.0.7-1U80_3cl.src.rpm

ftp://atualizacoes.conectiva.com.br/8/RPMS/gnupg-1.0.7-1U80_3cl.i386.rpm

ftp://atualizacoes.conectiva.com.br/8/RPMS/gnupg-doc-1.0.7-1U80_3cl.i386.rpm

ftp://atualizacoes.conectiva.com.br/9/SRPMS/gnupg-1.2.3-19780U90_1cl.src.rpm

ftp://atualizacoes.conectiva.com.br/9/RPMS/gnupg-1.2.3-19780U90_1cl.i386.rpm

ftp://atualizacoes.conectiva.com.br/9/RPMS/gnupg-doc-1.2.3-19780U90_1cl.i386.rpm

ftp://atualizacoes.conectiva.com.br/9/RPMS/gnupg-keyserver-plugins-1.2.3-19780U90_1cl.i386.rpm

ADDITIONAL INSTRUCTIONS
The apt tool can be used to perform RPM packages upgrades:

• run: apt-get update
• after that, execute: apt-get upgrade

Detailed instructions reagarding the use of apt and upgrade
examples can be found at http://distro.conectiva.com.br/atualizacoes/#apt?idioma=en

All packages are signed with Conectiva’s GPG key. The key and
instructions on how to import it can be found at
http://distro.conectiva.com.br/seguranca/chave/?idioma=en
Instructions on how to check the signatures of the RPM packages can
be found at http://distro.conectiva.com.br/seguranca/politica/?idioma=en

All our advisories and generic update instructions can be viewed at
http://distro.conectiva.com.br/atualizacoes/?idioma=en

Copyright (c) 2003 Conectiva Inc.
http://www.conectiva.com