Support for Short-Term, Automatically Renewed (STAR) Certificates in the Automated Certificate Management Environment (ACME)
RFC 8739

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Internet Engineering Task Force (IETF)                        Y. Sheffer
Request for Comments: 8739                                        Intuit
Category: Standards Track                                       D. Lopez
ISSN: 2070-1721                                      O. Gonzalez de Dios
                                                       A. Pastor Perales
                                                          Telefonica I+D
                                                              T. Fossati
                                                                     ARM
                                                              March 2020

Support for Short-Term, Automatically Renewed (STAR) Certificates in the
          Automated Certificate Management Environment (ACME)

Abstract

   Public key certificates need to be revoked when they are compromised,
   that is, when the associated private key is exposed to an
   unauthorized entity.  However, the revocation process is often
   unreliable.  An alternative to revocation is issuing a sequence of
   certificates, each with a short validity period, and terminating the
   sequence upon compromise.  This memo proposes an Automated
   Certificate Management Environment (ACME) extension to enable the
   issuance of Short-Term, Automatically Renewed (STAR) X.509
   certificates.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8739.

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.

Table of Contents

   1.  Introduction
     1.1.  Name Delegation Use Case
     1.2.  Terminology
     1.3.  Conventions Used in This Document
   2.  Protocol Flow
     2.1.  Bootstrap
     2.2.  Auto Renewal
     2.3.  Termination
   3.  Protocol Details
     3.1.  ACME Extensions
       3.1.1.  Extending the Order Resource
       3.1.2.  Canceling an Auto-renewal Order
     3.2.  Capability Discovery
     3.3.  Fetching the Certificates
     3.4.  Negotiating an Unauthenticated GET
     3.5.  Computing notBefore and notAfter of STAR Certificates
       3.5.1.  Example
   4.  Operational Considerations
     4.1.  The Meaning of "Short Term" and the Impact of Skewed Clocks
     4.2.  Impact on Certificate Transparency (CT) Logs
     4.3.  HTTP Caching and Dependability
   5.  IANA Considerations
     5.1.  New Registries
     5.2.  New Error Types
     5.3.  New Fields in Order Objects
     5.4.  Fields in the "auto-renewal" Object within an Order Object
     5.5.  New Fields in the "meta" Object within a Directory Object
     5.6.  Fields in the "auto-renewal" Object within a Directory
           Metadata Object
     5.7.  Cert-Not-Before and Cert-Not-After HTTP Headers
   6.  Security Considerations
     6.1.  No Revocation
     6.2.  Denial-of-Service Considerations
     6.3.  Privacy Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   The ACME protocol [RFC8555] automates the process of issuing a
   certificate to a named entity (an Identifier Owner or IdO).
   Typically, but not always, the identifier is a domain name.

   If the IdO wishes to obtain a string of short-term certificates
   originating from the same private key (see [TOPALOVIC] about why
   using short-lived certificates might be preferable to explicit
   revocation), she must go through the whole ACME protocol each time a
   new short-term certificate is needed, e.g., every 2-3 days.  If done
   this way, the process would involve frequent interactions between the
   registration function of the ACME Certification Authority (CA) and
   the identity provider infrastructure (e.g., DNS, web servers),
   therefore making the issuance of short-term certificates exceedingly
   dependent on the reliability of both.

   This document presents an extension of the ACME protocol that