maTLS: How to Make TLS middlebox-aware?

Hyunwoo Lee (Seoul National University), Zach Smith (University of Luxembourg), Junghwan Lim (Seoul National University), Gyeongjae Choi (Seoul National University), Selin Chun (Seoul National University), Taejoong Chung (Rochester Institute of Technology), Ted "Taekyoung" Kwon (Seoul National University)

Middleboxes (MBs) are widely deployed in order to enhance security and performance in networking.
However, as the communications over the TLS become increasingly common, the end-to-end channel model of the TLS undermines the efficacy of MBs.
Existing solutions, such as `split TLS' that intercepts TLS sessions, often introduce significant security risks by installing a custom root certificate or sharing a private key.
Many studies have confirmed the vulnerabilities of combining the TLS with MBs, which include certificate validation failures, unwanted content modification, and using obsolete ciphersuites.
To address the above issues, we introduce an MB-aware TLS protocol, dubbed maTLS, that allows MBs to participate in the TLS in a visible and accountable fashion.
Every participating MB now splits a session into two segments with its own security parameters in collaboration with the two endpoints.
However, the session is still secure as the maTLS protocol is designed to achieve the authentication of MBs, the audit of MBs' operations, and the verification of security parameters of segments.
We carry out testbed-based experiments to show that maTLS achieves the above security goals with marginal overhead.
We also prove the security model of maTLS by using Tamarin, a security verification tool.