GnuPG: Incorrect signature verification

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.

Workaround

There is no known workaround at this time.

Resolution

All GnuPG users should upgrade to the latest version:

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