multi-context TLS (mcTLS): Enabling Secure In-Network Functionality in TLS

Transport Layer Security (TLS), is the de facto protocol supporting secure HTTP (HTTPS), and is being discussed as the default transport protocol for HTTP2.0. It has seen wide adoption and is currently carrying a significant fraction of the overall HTTP traffic (Facebook, Google and Twitter use it by default). However, TLS makes the fundamental assumption that all functionality resides solely at the endpoints, and is thus unable to utilize the many in-network services that optimize network resource usage, improve user experience, and protect clients and servers from security threats. Re-introducing such in-network functionality into secure TLS sessions today is done through hacks, in many cases weakening overall security.

In this paper we introduce multi-context TLS (mcTLS) which enhances TLS by allowing middleboxes to be fully supported participants in TLS sessions. mcTLS breaks the "all-or-nothing" security model by allowing endpoints and content providers to explicitly introduce middleboxes in secure end-to-end sessions, while deciding whether they should have read or write access, and to which specific parts of the content. mcTLS enables transparency and control for both clients and servers.

We evaluate a prototype mcTLS implementation in both controlled and "live" experiments, showing that the benefits offered have minimal overhead.More importantly, we show that mcTLS can be incrementally deployed and requires small changes to clients, servers, and middleboxes, for a large number of use cases.