ACME TLS ALPN Challenge Extension
draft-ietf-acme-tls-alpn-00

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Last updated 2018-03-02
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ACME Working Group                                          R. Shoemaker
Internet-Draft                                                      ISRG
Intended status: Standards Track                          March 02, 2018
Expires: September 3, 2018

                   ACME TLS ALPN Challenge Extension
                      draft-ietf-acme-tls-alpn-00

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
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   This Internet-Draft will expire on September 3, 2018.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

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

1.  Introduction

   The Automatic Certificate Management Environment (ACME)
   [I-D.ietf-acme-acme] specification doesn't specify a TLS layer
   validation method which limits the points at which validation can be
   performed.  This document extends the ACME specification to include a
   TLS based validation method that uses the Application Level Protocol
   Negotiation extension.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119].

3.  TLS with Application Level Protocol Negotiation (TLS ALPN) Challenge

   The TLS with Application Level Protocol Negotiation (TLS ALPN)
   validation method proves control over a domain name by requiring the
   client to configure a TLS server referenced by the DNS A and/or AAAA
   Resource Records for the domain name to respond to specific
   connection attempts utilizing the ALPN extension [RFC7301].  The
   server validates control of the domain name by connecting to the TLS
   server and verifying a certificate with specific content is
   presented.

   type (required, string):  The string "tls-alpn-01"

   token (required, string):  A random value that uniquely identifies
      the challenge.  This value MUST have at least 128 bits of entropy.

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      It MUST NOT contain any characters outside the base64url alphabet,
      including padding characters ("=").

   GET /acme/authz/1234/1 HTTP/1.1
   Host: example.com

   HTTP/1.1 200 OK
   {
     "type": "tls-alpn-01",
     "url": "https://example.com/acme/authz/1234/1",
     "status": "pending",
     "token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA"
   }

   The client prepares for validation by constructing a self-signed
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