GnuPG: Incorrect signature verification

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200602-10 / gnupg
Release Date	February 18, 2006
Latest Revision	February 18, 2006: 01
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
app-crypt/gnupg	< 1.4.2.1	>= 1.4.2.1	All supported architectures

Related bugreports: #122721

Synopsis

Applications relying on GnuPG to authenticate digital signatures may incorrectly believe a signature has been verified.

2. Impact Information

Background

GnuPG (The GNU Privacy Guard) is a free replacement for PGP (Pretty Good Privacy). As GnuPG does not rely on any patented algorithms, it can be used without any restrictions. gpgv is the OpenPGP signature verification tool provided by the GnuPG system.

Description

Tavis Ormandy of the Gentoo Linux Security Auditing Team discovered that automated systems relying on the return code of GnuPG or gpgv to authenticate digital signatures may be misled by malformed signatures. GnuPG documentation states that a return code of zero (0) indicates success, however gpg and gpgv may also return zero if no signature data was found in a detached signature file.

Impact

An attacker may be able to bypass authentication in automated systems relying on the return code of gpg or gpgv to authenticate digital signatures.

3. Resolution Information

Workaround

There is no known workaround at this time.

Resolution

All GnuPG users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=app-crypt/gnupg-1.4.2.1"

4. References

Page updated February 18, 2006

Summary: This is a Gentoo Linux Security Advisory

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