NSA Pushes 'Labeled' Access Control for NFS

The National Security Agency (NSA) is pitching its own high-security access control technology for the next version of the Network File System (NFS) protocol.

NSA presented its so-called Labeled NFS technology, which is based on its mandatory access control (MAC) technology in the Security-Enhanced Linux (SELinux) operating system, earlier this week at the Internet Engineering Task Force meeting in Philadelphia.

Incorporating the MAC-driven technology into NFS would allow a “trusted” user or system to read and write sensitive files and run programs stored on NFS-based networked storage systems. MAC basically makes sure that users only access files for which they’re authorized, and that malicious code can’t run in NFS environments.

The IETF is now awaiting an official request for comments (RFC) from the NSA to begin the process of considering the new security feature for NFS.

“We suggested that they go ahead and [write an] Internet draft that provides some pointers to labeled mechanisms, and document what they’ve done, the design choices they’ve made… focusing on the requirements so we can [better] understand them,” says Spencer Shepler, co-chair of the IETF’s NFSv4 Working Group.

NSA was unavailable for comment at the time of this posting.

In general, a MAC approach centrally controls access policy to sensitive or restricted files and applications, and only a security policy administrator can set those policies (users can’t override them). When a user or program attempts to access a file, for instance, the system determines whether that user or object is authorized to do so.

Traditional access control methods today use an access control list (ACL), which determines access based on user identity, for example, and users and programs can make changes to access rules. The tradeoff with this “discretionary” access approach, according to the IETF presentation made by David Quigley of the NSA’s National Information Assurance Research Laboratory, is that organizations are not protected from malicious or vulnerable software -- and user privileges can be altered and expanded.

NFSv4, the current version of NFS, comes with Kerberos for strong authentication as well as an ACL specification. “You can use Kerberos to strongly authenticate users and to ensure a server is not spoofing or subverting the overall storage mechanisms. And common ACL mechanisms are defined,” says the IETF’s Shepler, who works for Sun. “I view the Labeled NFS work as a third vector of security.”

But whether Labeled NFS may be overkill for organizations that don’t have the same security concerns as a federal agency or the NSA is unclear. “My personal opinion is there’s a set of hurdles on how to use and manage it -- are [enterprises] prepared to take on that type of definition and granularity it might impose? Some organizations are just trying to deal with the basics of strong authentication and reasonable ACL usage -- fundamental things,” Shepler says.

Adding Labeled NFS would let SELinux systems expand their existing MAC security across networked storage systems. It would also benefit FreeBSD and Solaris, according to the NSA’s presentation.

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