GnuTLS: RSA Signature Forgery

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200609-15 / gnutls
Release Date	September 26, 2006
Latest Revision	September 26, 2006: 01
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
net-libs/gnutls	< 1.4.4	>= 1.4.4	All supported architectures

Related bugreports: #147682

Synopsis

GnuTLS fails to handle excess data which could allow an attacker to forge a PKCS #1 v1.5 signature.

2. Impact Information

Background

GnuTLS is an implementation of SSL 3.0 and TLS 1.0.

Description

verify.c fails to properly handle excess data in digestAlgorithm.parameters field while generating a hash when using an RSA key with exponent 3. RSA keys that use exponent 3 are commonplace.

Impact

Remote attackers could forge PKCS #1 v1.5 signatures that are signed with an RSA key, preventing GnuTLS from correctly verifying X.509 and other certificates that use PKCS.

3. Resolution Information

Workaround

There is no known workaround at this time.

Resolution

All GnuTLS users should update both packages:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --update --ask --verbose ">=net-libs/gnutls-1.4.4"

4. References

CVE-2006-4790

Page updated September 26, 2006

Summary: This is a Gentoo Linux Security Advisory

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