GnuPG: ElGamal signing keys compromised and format string vulnerability

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200312-05 / GnuPG
Release Date	December 12, 2003
Latest Revision	December 12, 2003: 01
Impact	minimal
Exploitable	unknown

Package	Vulnerable versions	Unaffected versions	Architecture(s)
app-crypt/gnupg	<= 1.2.3-r4	>= 1.2.3-r5	All supported architectures

Related bugreports: #34504

Synopsis

A bug in GnuPG allows ElGamal signing keys to be compromised, and a format string bug in the gpgkeys_hkp utility may allow arbitrary code execution.

2. Impact Information

Background

GnuPG is a popular open source signing and encryption tool.

Description

Two flaws have been found in GnuPG 1.2.3.

First, ElGamal signing keys can be compromised. These keys are not commonly used, but this is "a significant security failure which can lead to a compromise of almost all ElGamal keys used for signing. Note that this is a real world vulnerability which will reveal your private key within a few seconds".

Second, there is a format string flaw in the 'gpgkeys_hkp' utility which "would allow a malicious keyserver in the worst case to execute an arbitrary code on the user's machine."

Impact

If you have used ElGamal keys for signing your private key can be compromised, and a malicious keyserver could remotely execute arbitrary code with the permissions of the user running gpgkeys_hkp.

3. Resolution Information

Workaround

There is no known workaround at this time.

Resolution

All users who have created ElGamal signing keys should immediately revoke them. In addition, all Gentoo Linux machines with gnupg installed should be updated to use gnupg-1.2.3-r5 or higher:

Code Listing 3.1: Resolution

# emerge sync
# emerge -pv '>=app-crypt/gnupg-1.2.3-r5'
# emerge '>=app-crypt/gnupg-1.2.3-r5'
# emerge clean

4. References

Page updated December 12, 2003

Summary: This is a Gentoo Linux Security Advisory

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