federalist.18f.gov vulnerable to Sweet32 attack

Summary

The researcher noted that federalist.18f.gov allows use of the TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher, which is now marked as "weak" in SSL labs because of risks of MitM attacks given this vulnerability: https://sweet32.info/, which requires monitoring of a long lived HTTPS connection.

We inherit this cipher from the cloud.gov PaaS (its required to serve specific browser/OS combinations) and have been working to migrate away from it since May 2017: https://github.com/18F/cg-provision/issues/244

Because we were already aware of the concern with this cipher, but there was no existing H1 ticket open on this matter, we closed the ticket as informative.