Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
draft-ietf-uta-rfc7525bis-00

Document Type Active Internet-Draft (uta WG)
Authors Yaron Sheffer  , Ralph Holz  , Peter Saint-Andre 
Last updated 2020-10-29
Replaces draft-sheffer-uta-bcp195bis, draft-sheffer-uta-rfc7525bis
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UTA Working Group                                             Y. Sheffer
Internet-Draft                                                    Intuit
Obsoletes: 7525 (if approved)                                    R. Holz
Intended status: Best Current Practice              University of Twente
Expires: May 3, 2021                                      P. Saint-Andre
                                                                 Mozilla
                                                        October 30, 2020

  Recommendations for Secure Use of Transport Layer Security (TLS) and
                Datagram Transport Layer Security (DTLS)
                      draft-ietf-uta-rfc7525bis-00

Abstract

   Transport Layer Security (TLS) and Datagram Transport Layer Security
   (DTLS) are widely used to protect data exchanged over application
   protocols such as HTTP, SMTP, IMAP, POP, SIP, and XMPP.  Over the
   last few years, several serious attacks on TLS have emerged,
   including attacks on its most commonly used cipher suites and their
   modes of operation.  This document provides recommendations for
   improving the security of deployed services that use TLS and DTLS.
   The recommendations are applicable to the majority of use cases.

   This document was published as RFC 7525 when the industry was in the
   midst of its transition to TLS 1.2.  Years later this transition is
   largely complete and TLS 1.3 is widely available.  Given the new
   environment, we believe new guidance is needed.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 3, 2021.

Sheffer, et al.            Expires May 3, 2021                  [Page 1]
Internet-Draft             TLS Recommendations              October 2020

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  General Recommendations . . . . . . . . . . . . . . . . . . .   4
     3.1.  Protocol Versions . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  SSL/TLS Protocol Versions . . . . . . . . . . . . . .   4
       3.1.2.  DTLS Protocol Versions  . . . . . . . . . . . . . . .   6
       3.1.3.  Fallback to Lower Versions  . . . . . . . . . . . . .   6
     3.2.  Strict TLS  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Compression . . . . . . . . . . . . . . . . . . . . . . .   7
     3.4.  TLS Session Resumption  . . . . . . . . . . . . . . . . .   8
     3.5.  TLS Renegotiation . . . . . . . . . . . . . . . . . . . .   8
     3.6.  Server Name Indication  . . . . . . . . . . . . . . . . .   9
   4.  Recommendations: Cipher Suites  . . . . . . . . . . . . . . .   9
     4.1.  General Guidelines  . . . . . . . . . . . . . . . . . . .   9
     4.2.  Recommended Cipher Suites . . . . . . . . . . . . . . . .  11
       4.2.1.  Implementation Details  . . . . . . . . . . . . . . .  11
     4.3.  Public Key Length . . . . . . . . . . . . . . . . . . . .  12
     4.4.  Modular Exponential vs. Elliptic Curve DH Cipher Suites .  13
     4.5.  Truncated HMAC  . . . . . . . . . . . . . . . . . . . . .  14
   5.  Applicability Statement . . . . . . . . . . . . . . . . . . .  14
     5.1.  Security Services . . . . . . . . . . . . . . . . . . . .  15
     5.2.  Opportunistic Security  . . . . . . . . . . . . . . . . .  16
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
     6.1.  AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.2.  Forward Secrecy . . . . . . . . . . . . . . . . . . . . .  17
     6.3.  Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . .  18
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