Issues and Requirements for SNI Encryption in TLS
draft-ietf-tls-sni-encryption-03
Network Working Group C. Huitema
Internet-Draft Private Octopus Inc.
Intended status: Informational E. Rescorla
Expires: November 21, 2018 RTFM, Inc.
May 20, 2018
Issues and Requirements for SNI Encryption in TLS
draft-ietf-tls-sni-encryption-03
Abstract
This draft describes the general problem of encryption of the Server
Name Identification (SNI) parameter. The proposed solutions hide a
Hidden Service behind a Fronting Service, only disclosing the SNI of
the Fronting Service to external observers. The draft lists known
attacks against SNI encryption, discusses the current "co-tenancy
fronting" solution, and presents requirements for future TLS layer
solutions.
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This Internet-Draft will expire on November 21, 2018.
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Internet-Draft TLS-SNI Encryption Requirements May 2018
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. History of the TLS SNI extension . . . . . . . . . . . . . . 3
2.1. Unanticipated usage of SNI information . . . . . . . . . 3
2.2. SNI encryption timeliness . . . . . . . . . . . . . . . . 4
2.3. End-to-end alternatives . . . . . . . . . . . . . . . . . 4
3. Security and Privacy Requirements for SNI Encryption . . . . 5
3.1. Mitigate Replay Attacks . . . . . . . . . . . . . . . . . 5
3.2. Avoid Widely Shared Secrets . . . . . . . . . . . . . . . 5
3.3. Prevent SNI-based Denial of Service Attacks . . . . . . . 6
3.4. Do not stick out . . . . . . . . . . . . . . . . . . . . 6
3.5. Forward Secrecy . . . . . . . . . . . . . . . . . . . . . 6
3.6. Proper Security Context . . . . . . . . . . . . . . . . . 6
3.7. Fronting Server Spoofing . . . . . . . . . . . . . . . . 7
3.8. Supporting multiple protocols . . . . . . . . . . . . . . 7
3.8.1. Hiding the Application Layer Protocol Negotiation . . 8
3.8.2. Support other transports than HTTP . . . . . . . . . 8
3.9. Fail to fronting . . . . . . . . . . . . . . . . . . . . 8
4. HTTP Co-Tenancy Fronting . . . . . . . . . . . . . . . . . . 9
4.1. HTTPS Tunnels . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Delegation Control . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
Historically, adversaries have been able to monitor the use of web
services through three channels: looking at DNS requests, looking at
IP addresses in packet headers, and looking at the data stream
between user and services. These channels are getting progressively
closed. A growing fraction of Internet communication is encrypted,
mostly using Transport Layer Security (TLS) [RFC5246]. Progressive
deployment of solutions like DNS in TLS [RFC7858] mitigates the
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