By Tommy Armendariz
Antivirus Expert, about.com
In the process of its ongoing research, the Intel Security Advanced Threat Research Team (ATR) has discovered a critical signature forgery vulnerability in the Mozilla Network Security Services (NSS) crypto library that could allow malicious parties to set up fraudulent sites impersonating as legitimate businesses and other organizations.
The
Mozilla NSS library is a set of libraries designed to support
cross-platform development of security-enabled client and server
applications. Applications built with NSS can support SSL v2 and v3,
TLS, PKCS #5, PKCS #7, PKCS #11, PKCS #12, S/MIME, X.509 v3
certificates, and other security standards. NSS provides open source
implementation of the crypto libraries used by AOL, Red Hat, Google, and
other companies in a variety of products, including the following:
- AOL Instant Messenger (AIM)
- Open source client applications, such as Evolution, Pidgin, and Apache OpenOffice
- Server products such as Red Hat: Red Hat Directory Server, Red Hat Certificate System, and the mod_nss SSL module for the Apache web
- Server products from the Sun Java Enterprise System
In addition, NSS is commonly used in the Firefox web browser and is can also be found in Thunderbird, Seamonkey, and other Mozilla products. The critical signature vulnerably, dubbed “BERserk”, allows attackers to forge RSA signatures, thereby allowing for the bypass of authentication to websites utilizing SSL/TLS.
Given that certificates can be forged for any domain, this issue raises
serious concerns around integrity and confidentiality as we navigate
what we perceive to be secure websites.
Why it’s called BERserk
This attack exploits a vulnerability in the parsing of ASN.1 encoded messages during signature verification. ASN.1 messages are made up of various parts that are encoded using BER (Basic Encoding Rules) and/or DER (Distinguished Encoding Rules).
This attack exploits the length of a field in BER encoding can be made
to use many bytes of data. In vulnerable implementations, these bytes
are then skipped during parsing. This condition enables the attack.
This is a variation on the Bleichenbacher PKCS#1 RSA Signature Verification vulnerability of 2006.
How is it Being Addressed?
“Upon
discovery of this issue, the Intel Security ATR team notified Mozilla
to facilitate the mitigation and resolution of the vulnerability. We
also engaged CERT/CC to ensure that all affected parties are responsibly
and effectively notified and given mitigation guidance on this issue,
and to review other commonly used cryptographic libraries for similar
issues,” stated James Walter, director of advanced threat research of
Intel Security.
The Intel Security Advanced Threat Research team
is continuing to work with CERT/CC in addition to reviewing other
commonly used cryptographic libraries for this issue. They will
continue to update users and affected parties as new details emerge.
The team will also be releasing a paper with full technical details on
this potential exploit.
McAfee Product Coverage & Countermeasures
McAfee
Vulnerability Manager (MVM) will release an update to check for
vulnerable systems and report their exposure. McAfee will continue to
review other potential mitigation methods and technologies and will keep
customers up to date.
What Users can do Immediately
If you’re a Firefox browser user, you can take immediate action by updating your browser with the latest patches from Mozilla. Google has also released updates for Google Chrome and ChromeOS, as these products also utilize the vulnerable library.
As
this issue unfolds, Intel Security will continue to provide updates on
effective countermeasures and proper mitigation strategies.
