Special Pub 800-52 revision 1 was published at the end of April (April 28th) and is a pretty good document to enhance the readers understanding of the Transport Layer Security (TLS) protocol, the various steps involved in TLS tunnel establishment, the cipher suites supported and best practices for certificate validation. I would highly recommend readers of this blog read also through the document to gain an understanding of TLS or to get a refresher.

The reason to write this blog post though is to point out a requirement in the document that can have a pretty significant impact on current and future FIPS 140-2 validations (and potentially Common Criteria evaluations within the US scheme).

Section 3.1 states that TLS 1.1 is the minimum TLS version that can be configured on servers deployed in Federal government networks (with some caveats). TLS 1.0 (which is the most prevalent version and allowed by FIPS 140-2, currently) is not allowed. Moreover starting January 1, 2015, TLS 1.2 is the only version that will be allowed. Below is the relevant snippet from the special pub:

Servers that support government-only applications shall be configured to support TLS 1.1, and should be configured to support TLS 1.2. These servers shall not support TLS 1.0, SSL 2.0, or SSL 3.0. TLS versions 1.1 and 1.2 are represented by major and minor number tuples (3, 2) and (3, 3), respectively7. Agencies shall develop migration plans to support TLS 1.2 by January 1, 2015.
Servers that support citizen or business-facing applications shall be configured to support version 1.1 and should be configured to support version 1.2. These servers may also be configured to support TLS version 1.0 in order to enable interaction with citizens and businesses. These servers shall not support SSL version 3.0 or earlier. If TLS 1.0 is supported, the use of TLS 1.1 and 1.2 shall be preferred over TLS 1.0.

This is a significant requirement should CMVP start enforcing this restriction as part of FIPS 140-2 validations. TLS 1.1 support is not very prevalent. The support for TLS 1.2 is even less and Jan 1st is not very far away.

Acumen is contacting CMVP to receive clarification on their stance regarding TLS versions allowed in FIPS mode of operation going forward. We will update this post once we receive any information from the CMVP. In the meantime our strong recommendation would be to put support of TLS 1.2 into your development plan. It will not only head off any sudden change in requirements from CMVP but also help in Common Criteria evaluation (TLS 1.2 is the only version that supports the Suite B class of crypto algorithms and something that NIAP also wants to move to ASAP).
Bottom Line: Don’t change any plans for in-flight evaluations however put TLS 1.2 on the immediate product roadmap as an insurance policy and for future proofing.

Update 6/18/14: We heard back from NIST and all is good. They have indicated that SP 800-52r1 is a recommendation for TLS deployment for Federal agencies however FIPS 140-2 will continue allowing TLS v1.0 as long as the implementation uses FIPS approved cryptographic algorithms/primitives. The reasoning given is that FIPS validation is for approved algorithms and not necessarily the protocols.

The above update not withstanding, Acumen’s recommendation in the original post still stands. Given where the security industry is going, and requirement for Suite B crypto in a number of national security accounts it would make imminent sense to start implementing TLS 1.2 in future product releases. Please feel free to leave a comment or send email to info(at)acumensecurity(dot)net if you have any questions.