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GnuPG: Incorrect signature verification

Content:

1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200603-08 / gnupg
Release Date March 10, 2006
Latest Revision March 10, 2006: 01
Impact normal
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
app-crypt/gnupg < 1.4.2.2 >= 1.4.2.2 All supported architectures

Related bugreports: #125217

Synopsis

GnuPG may erroneously report a modified or unsigned message has a valid digital signature.

2.  Impact Information

Background

The GNU Privacy Guard, GnuPG, is a free replacement for the PGP suite of cryptographic software that may be used without restriction, as it does not rely on any patented algorithms. GnuPG can be used to digitally sign messages, a method of ensuring the authenticity of a message using public key cryptography.

Description

OpenPGP is the standard that defines the format of digital signatures supported by GnuPG. OpenPGP signatures consist of multiple sections, in a strictly defined order. Tavis Ormandy of the Gentoo Linux Security Audit Team discovered that certain illegal signature formats could allow signed data to be modified without detection. GnuPG has previously attempted to be lenient when processing malformed or legacy signature formats, but this has now been found to be insecure.

Impact

A remote attacker may be able to construct or modify a digitally-signed message, potentially allowing them to bypass authentication systems, or impersonate another user.

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-1.4.2.2"

4.  References



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Page updated March 10, 2006

Summary: This is a Gentoo Linux Security Advisory

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