Last Call Review of draft-ietf-tls-sni-encryption-05

Request Review of draft-ietf-tls-sni-encryption
Requested rev. no specific revision (document currently at 09)
Type Last Call Review
Team Ops Directorate (opsdir)
Deadline 2019-09-02
Requested 2019-08-19
Authors Christian Huitema, Eric Rescorla
Draft last updated 2019-08-20
Completed reviews Opsdir Last Call review of -05 by Dan Romascanu (diff)
Genart Last Call review of -05 by Meral Shirazipour (diff)
Tsvart Telechat review of -05 by Bernard Aboba (diff)
Assignment Reviewer Dan Romascanu 
State Completed
Review review-ietf-tls-sni-encryption-05-opsdir-lc-romascanu-2019-08-20
Posted at
Reviewed rev. 05 (document currently at 09)
Review result Ready
Review completed: 2019-08-20


This document targets Informational status. It is Ready from an OPS-DIR perspective and it offers valuable information for operators deploying TLS. It does not define a new protocol, thus a full RFC 5706 OPS-DIR review does not apply. It does however raise a number of operational issues in the deployment of multiplexed servers that rely on the Service Name Information (SNI) TLS extension which is a protocol element transmitted in clear text. Section 3 details the different type of attacks and lists encryption requirements for SNI that would prevent these, but notes that not all can be simultaneously met by implementations and deployments. Section 4 describes the HTTP Co-Tenancy Fronting as a solution that could be deployed in the absence of TLS-level SNI encryption. The HTTP fronting solution can be deployed without modification to the TLS protocol, and does not require using any specific version of TLS.  There are however a few issues regarding discovery, client implementations, trust, and applicability which are further discussed. Operators should note that Section 5 states that 'The current HTTP based solutions described in Section 4 only meet some of these requirements.  In practice, it may well be that no solution can meet every requirement, and that practical solutions will have to make some compromises.'