Critical: nspr and nss security and bug fix update

Updated nspr and nss packages that fix security issues and a bug are now
available for Red Hat Enterprise Linux 4.

This update has been rated as having critical security impact by the Red
Hat Security Response Team.

Netscape Portable Runtime (NSPR) provides platform independence for non-GUI
operating system facilities. These facilities include threads, thread
synchronization, normal file and network I/O, interval timing, calendar
time, basic memory management (malloc and free), and shared library linking.

Network Security Services (NSS) is a set of libraries designed to support
the cross-platform development of security-enabled client and server
applications. Applications built with NSS can support SSLv2, SSLv3, TLS,
and other security standards.

These updated packages upgrade NSS from the previous version, 3.12.2, to a
prerelease of version 3.12.4. The version of NSPR has also been upgraded
from 4.7.3 to 4.7.4.

Moxie Marlinspike reported a heap overflow flaw in a regular expression
parser in the NSS library used by browsers such as Mozilla Firefox to match
common names in certificates. A malicious website could present a
carefully-crafted certificate in such a way as to trigger the heap
overflow, leading to a crash or, possibly, arbitrary code execution with
the permissions of the user running the browser. (CVE-2009-2404)

Note: in order to exploit this issue without further user interaction in
Firefox, the carefully-crafted certificate would need to be signed by a
Certificate Authority trusted by Firefox, otherwise Firefox presents the
victim with a warning that the certificate is untrusted. Only if the user
then accepts the certificate will the overflow take place.

Dan Kaminsky discovered flaws in the way browsers such as Firefox handle
NULL characters in a certificate. If an attacker is able to get a
carefully-crafted certificate signed by a Certificate Authority trusted by
Firefox, the attacker could use the certificate during a man-in-the-middle
attack and potentially confuse Firefox into accepting it by mistake.
(CVE-2009-2408)

Dan Kaminsky found that browsers still accept certificates with MD2 hash
signatures, even though MD2 is no longer considered a cryptographically
strong algorithm. This could make it easier for an attacker to create a
malicious certificate that would be treated as trusted by a browser. NSS
now disables the use of MD2 and MD4 algorithms inside signatures by
default. (CVE-2009-2409)

These version upgrades also provide a fix for the following bug:

* SSL client authentication failed against an Apache server when it was
using the mod_nss module and configured for NSSOCSP. On the client side,
the user agent received an error message that referenced "Error Code:
-12271" and stated that establishing an encrypted connection had failed
because the certificate had been rejected by the host.

On the server side, the nss_error_log under /var/log/httpd/ contained the
following message:

[error] Re-negotiation handshake failed: Not accepted by client!?

Also, /var/log/httpd/error_log contained this error:

SSL Library Error: -8071 The OCSP server experienced an internal error

With these updated packages, the dependency problem which caused this
failure has been resolved so that SSL client authentication with an
Apache web server using mod_nss which is configured for NSSOCSP succeeds
as expected. Note that if the presented client certificate is expired,
then access is denied, the user agent is presented with an error message
about the invalid certificate, and the OCSP queries are seen in the OCSP
responder. Also, similar OCSP status verification happens for SSL server
certificates used in Apache upon instance start or restart. (BZ#508027)

All users of nspr and nss are advised to upgrade to these updated packages,
which resolve these issues.

Before applying this update, make sure that all previously-released
errata relevant to your system have been applied.

This update is available via Red Hat Network. Details on how to use
the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259

508027 - rhcs80beta TPS and mod_nss with NSSOCSP has ssl errors and unable to use agent service
510197 - CVE-2009-2409 deprecate MD2 in SSL cert validation (Kaminsky)
510251 - CVE-2009-2408 firefox/nss: doesn't handle NULL in Common Name properly
512912 - CVE-2009-2404 nss regexp heap overflow

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2404
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2408
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2409
http://www.redhat.com/security/updates/classification/#critical