X.509v3 Transport Layer Security (TLS) Feature Extension
RFC 7633

Document Type RFC - Proposed Standard (October 2015; Errata)
Was draft-hallambaker-tlsfeature (individual in sec area)
Last updated 2015-12-28
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Document shepherd Sean Turner
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IESG IESG state RFC 7633 (Proposed Standard)
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Internet Engineering Task Force (IETF)                   P. Hallam-Baker
Request for Comments: 7633                             Comodo Group Inc.
Category: Standards Track                                   October 2015
ISSN: 2070-1721

        X.509v3 Transport Layer Security (TLS) Feature Extension

Abstract

   The purpose of the TLS feature extension is to prevent downgrade
   attacks that are not otherwise prevented by the TLS protocol.  In
   particular, the TLS feature extension may be used to mandate support
   for revocation checking features in the TLS protocol such as Online
   Certificate Status Protocol (OCSP) stapling.  Informing clients that
   an OCSP status response will always be stapled permits an immediate
   failure in the case that the response is not stapled.  This in turn
   prevents a denial-of-service attack that might otherwise be possible.

Status of This Memo

   This is an Internet Standards Track document.

   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
   Internet Standards 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/rfc7633.

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.

Hallam-Baker                 Standards Track                    [Page 1]
RFC 7633                  TLS Feature Extension             October 2015

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
     2.2.  TLS Feature, X.509 Extension  . . . . . . . . . . . . . .   3
   3.  Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  TLS Feature . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Use . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  Certificate Signing Request . . . . . . . . . . . . .   5
       4.2.2.  Certificate Signing Certificate . . . . . . . . . . .   5
       4.2.3.  End-Entity Certificate  . . . . . . . . . . . . . . .   5
     4.3.  Processing  . . . . . . . . . . . . . . . . . . . . . . .   6
       4.3.1.  Certification Authority . . . . . . . . . . . . . . .   6
       4.3.2.  Server  . . . . . . . . . . . . . . . . . . . . . . .   7
       4.3.3.  Client  . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
     5.1.  Alternative Certificates and Certificate Issuers  . . . .   7
     5.2.  Denial of Service . . . . . . . . . . . . . . . . . . . .   8
     5.3.  Cipher Suite Downgrade Attack . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  ASN.1 Module . . . . . . . . . . . . . . . . . . . .  10
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The Transport Layer Security (TLS) feature extension provides a means
   of preventing downgrade attacks that are not otherwise prevented by
   the TLS protocol.

   Since the TLS protocol itself provides strong protection against most
   forms of downgrade attack including downgrade attacks against cipher
   suite choices offered and client credentials, the TLS feature
   extension is only relevant to the validation of TLS protocol
   credentials.

2.  Definitions

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Hallam-Baker                 Standards Track                    [Page 2]
RFC 7633                  TLS Feature Extension             October 2015

2.2.  TLS Feature, X.509 Extension
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