(RHSA-2015:1457) Moderate: gnutls security and bug fix update

The GnuTLS library provides support for cryptographic algorithms and for
protocols such as Transport Layer Security (TLS).

It was found that GnuTLS did not check activation and expiration dates of
CA certificates. This could cause an application using GnuTLS to
incorrectly accept a certificate as valid when its issuing CA is already
expired. (CVE-2014-8155)

It was found that GnuTLS did not verify whether a hashing algorithm listed
in a signature matched the hashing algorithm listed in the certificate.
An attacker could create a certificate that used a different hashing
algorithm than it claimed, possibly causing GnuTLS to use an insecure,
disallowed hashing algorithm during certificate verification.
(CVE-2015-0282)

It was discovered that GnuTLS did not check if all sections of X.509
certificates indicate the same signature algorithm. This flaw, in
combination with a different flaw, could possibly lead to a bypass of the
certificate signature check. (CVE-2015-0294)

The CVE-2014-8155 issue was discovered by Marcel Kolaja of Red Hat.
The CVE-2015-0282 and CVE-2015-0294 issues were discovered by Nikos
Mavrogiannopoulos of the Red Hat Security Technologies Team.

This update also fixes the following bug:

• Previously, under certain circumstances, the certtool utility could
  generate X.509 certificates which contained a negative modulus.
  Consequently, such certificates could have interoperation problems with the
  software using them. The bug has been fixed, and certtool no longer
  generates X.509 certificates containing a negative modulus. (BZ#1036385)

Users of gnutls are advised to upgrade to these updated packages, which
contain backported patches to correct these issues.