Automated Certificate Management Environment (ACME) Server Capability Advertisements
draft-tweedale-acme-server-capabilities-00

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Network Working Group                                        F. Tweedale
Internet-Draft                                                   Red Hat
Intended status: Standards Track                        16 November 2020
Expires: 20 May 2021

 Automated Certificate Management Environment (ACME) Server Capability
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               draft-tweedale-acme-server-capabilities-00

Abstract

   Automated Certificate Management Environment (ACME) servers typically
   support only a subset of the ACME identifier types and validation
   types that have been defined.  This document defines new fields for
   the the ACME directory object to allow servers to advertise their
   capabilities, assisting clients to select a suitable server.

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
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   This Internet-Draft will expire on 20 May 2021.

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 (https://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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  ACME Directory Metadata Fields  . . . . . . . . . . . . . . .   3
     3.1.  "supportedIdentifierTypes" Field  . . . . . . . . . . . .   3
     3.2.  "supportedValidationMethods" Field  . . . . . . . . . . .   3
   4.  Example Directory Object  . . . . . . . . . . . . . . . . . .   3
   5.  Server Policy is Distinct From Server Capabilities  . . . . .   4
     5.1.  Server Policy Advertisements (Possible Future Work) . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  ACME Directory Metadata Fields  . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Automatic Certificate Management Environment [ACME] specifies a
   protocol by which a client may, in an automatable way, prove control
   of identifiers and obtain a certificate from an Certificate Authority
   (the ACME server).  The ACME protocol can be (and has been) extended
   to support different identifier types and validation methods.
   Identifier types include "dns" [ACME], "ip" [RFC8738], and "email"
   [I-D.ietf-acme-email-smime].  Validation methods include "http-01"
   and "dns-01" [ACME], "tls-alpn-01" [RFC8737], and "email-reply-00"
   [I-D.ietf-acme-email-smime].

   An ACME client could have awareness of and access to multiple ACME
   servers, and the servers could differ in which identifier types and
   validation methods they support.  This document specifies a mechanism
   to assist ACME clients to select a server that supports the
   identifier type(s) it needs and the validation method(s) it can
   perform.  It does so by defining new fields in the "meta" field of
   the ACME directory object, in which a server can advertise its
   capabilities.  Clients can check these fields to see whether the
   server capabilities satisfy their requirements.

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
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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