Bulletproof TLS Newsletter #33
Why TLS 1.3 isn’t there yet
31 October 2017
Author: Hanno Böck

This issue was distributed to 40,900 email subscribers.

Bulletproof TLS Newsletter is a free periodic newsletter bringing you commentary and news surrounding SSL/TLS and Internet PKI, designed to keep you informed about the latest developments in this space.

In this issue:

  1. Why TLS 1.3 isn’t there yet
  2. Short news

Why TLS 1.3 isn’t there yet

Deployment of TLS 1.3 is currently blocked by faulty middlebox devices. In theory, the protocol has been deemed ready; the latest draft 21 of TLS 1.3 was published in July, and it’s been in “Last Call” state for a while.

As Eric Rescorla reports in the TLS working group, a significant number of connection failures have been observed in experiments carried out by Google and Firefox. The source of the failures seems to be middleboxes that try to analyze traffic and block packets that don’t look like known protocol messages.

Details are scarce at this point, and no vendors have been named. The only known case of a vendor failing at TLS 1.3 was due to a bug in Blue Coat devices, as mentioned in our January newsletter.

However, it seems that changing TLS 1.3 in slight ways that make it look more like TLS 1.2 may make it possible to bring the failure rate down to an acceptable level. How these changes look is unclear, as it hasn’t been discussed in public.

Once again, it seems faulty devices make deploying a new protocol harder. This isn’t new. The deployment of previous TLS versions was seriously hampered by so-called version intolerance. Fallbacks implemented by browsers in the past have subsequently led to security vulnerabilities like POODLE. In TLS 1.3, a new version negotiation mechanism was implemented, and the GREASE mechanism was introduced to prevent such issues in the future.

Short news