ACME TLS ALPN Challenge Extension
draft-ietf-acme-tls-alpn-05

Document Type Active Internet-Draft (acme WG)
Last updated 2018-08-27 (latest revision 2018-08-17)
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ACME Working Group                                          R. Shoemaker
Internet-Draft                                                      ISRG
Intended status: Standards Track                         August 16, 2018
Expires: February 17, 2019

                   ACME TLS ALPN Challenge Extension
                      draft-ietf-acme-tls-alpn-05

Abstract

   This document specifies a new challenge for the Automated Certificate
   Management Environment (ACME) protocol which allows for domain
   control validation using TLS.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   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 February 17, 2019.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  TLS with Application Level Protocol Negotiation (TLS ALPN)
       Challenge . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  acme-tls/1 Protocol Definition  . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  SMI Security for PKIX Certificate Extension OID . . . . .   6
     5.2.  ALPN Protocol ID  . . . . . . . . . . . . . . . . . . . .   6
     5.3.  ACME Validation Method  . . . . . . . . . . . . . . . . .   6
   6.  Appendix: Design Rationale  . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The Automatic Certificate Management Environment (ACME)
   [I-D.ietf-acme-acme] standard specifies methods for validating
   control of domain names via HTTP and DNS.  Deployment experience has
   shown it is also useful to be able to validate domain control using
   the TLS layer alone.  In particular, this allows hosting providers,
   CDNs, and TLS-terminating load balancers to validate domain control
   without modifying the HTTP handling behavior of their backends.  This
   separation of layers can improve security and usability of ACME
   validation.

   Early ACME drafts specified two TLS-based challenge types: TLS-SNI-01
   and TLS-SNI-02.  These methods were removed because they relied on
   assumptions about the deployed base of HTTPS hosting providers that
   proved to be incorrect.  Those incorrect assumptions weakened the
   security of those methods and are discussed in the "Design Rationale"
   appendix.

   This document specifies a new TLS-based challenge type, TLS-ALPN-01.
   This challenge requires negotiating a new application-layer protocol
   using the TLS Application-Layer Protocol Negotiation (ALPN) Extension
   [RFC7301].  Because no existing software implements this protocol,
   the ability to fulfill TLS-ALPN-01 challenges is effectively opt-in.
   A service provider must proactively deploy new code in order to
   implement TLS-ALPN-01, so we can specify stronger controls in that
   code, resulting in a stronger validation method.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
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