RFC 7525 - Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)

Internet Engineering Task Force (IETF)
Request for Comments: 7525
BCP: 195
Category: Best Current Practice
ISSN: 2070-1721

Authors:

• Y. Sheffer (Intuit)
• R. Holz (NICTA)
• P. Saint-Andre (&yet)

Date: May 2015

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 memo documents an Internet Best Current Practice.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7525.

Copyright Notice

Copyright (c) 2015 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Contents

• 1. Introduction
• 2. Terminology
• 3. General Recommendations
  • 3.1. Protocol Versions
  • 3.2. Strict TLS
  • 3.3. Compression
  • 3.4. TLS Session Resumption
  • 3.5. TLS Renegotiation
  • 3.6. Server Name Indication
• 4. Recommendations: Cipher Suites
  • 4.1. General Guidelines
  • 4.2. Recommended Cipher Suites
  • 4.3. Public Key Length
  • 4.4. Modular Exponential vs. Elliptic Curve DH Cipher Suites
  • 4.5. Truncated HMAC
• 5. Applicability Statement
  • 5.1. Security Services
  • 5.2. Opportunistic Security
• 6. Security Considerations
  • 6.1. Host Name Validation
  • 6.2. AES-GCM
  • 6.3. Forward Secrecy
  • 6.4. Diffie-Hellman Exponent Reuse
  • 6.5. Certificate Revocation
• 7. References
  • 7.1. Normative References
  • 7.2. Informative References
• Acknowledgments
• Authors' Addresses