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

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UTA Working Group                                             Y. Sheffer
Internet-Draft                                                    Intuit
Obsoletes: 7525 (if approved)                                    R. Holz
Intended status: Best Current Practice                             NICTA
Expires: October 26, 2020                                 P. Saint-Andre
                                                                 Mozilla
                                                          April 24, 2020

  Recommendations for Secure Use of Transport Layer Security (TLS) and
                Datagram Transport Layer Security (DTLS)
                    draft-sheffer-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.

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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   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 26, 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
   Provisions Relating to IETF Documents

Sheffer, et al.         Expires October 26, 2020                [Page 1]
Internet-Draft             TLS Recommendations                April 2020

   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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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  . . . . . . . . . . . . . . .   5
       3.1.3.  Fallback to Lower Versions  . . . . . . . . . . . . .   5
     3.2.  Strict TLS  . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Compression . . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  TLS Session Resumption  . . . . . . . . . . . . . . . . .   7
     3.5.  TLS Renegotiation . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Server Name Indication  . . . . . . . . . . . . . . . . .   8
   4.  Recommendations: Cipher Suites  . . . . . . . . . . . . . . .   8
     4.1.  General Guidelines  . . . . . . . . . . . . . . . . . . .   8
     4.2.  Recommended Cipher Suites . . . . . . . . . . . . . . . .  10
       4.2.1.  Implementation Details  . . . . . . . . . . . . . . .  10
     4.3.  Public Key Length . . . . . . . . . . . . . . . . . . . .  11
     4.4.  Modular Exponential vs. Elliptic Curve DH Cipher Suites .  12
     4.5.  Truncated HMAC  . . . . . . . . . . . . . . . . . . . . .  13
   5.  Applicability Statement . . . . . . . . . . . . . . . . . . .  13
     5.1.  Security Services . . . . . . . . . . . . . . . . . . . .  14
     5.2.  Opportunistic Security  . . . . . . . . . . . . . . . . .  15
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
     6.1.  AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.2.  Forward Secrecy . . . . . . . . . . . . . . . . . . . . .  16
     6.3.  Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . .  17
     6.4.  Certificate Revocation  . . . . . . . . . . . . . . . . .  17
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  19