Automated Certificate Management Environment (ACME) Extension for Single Sign On Challenges
draft-biggs-acme-sso-00

Document Type Active Internet-Draft (individual)
Authors Andrew Biggs  , Richard Barnes 
Last updated 2020-12-08
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ACME WG                                                         A. Biggs
Internet-Draft                                               R.L. Barnes
Intended status: Informational                                     Cisco
Expires: 11 June 2021                                    8 December 2020

Automated Certificate Management Environment (ACME) Extension for Single
                           Sign On Challenges
                        draft-biggs-acme-sso-00

Abstract

   This document specifies an extension to the ACME protocol [RFC8555]
   to enable ACME servers to validate a client's control of an email
   identifier using single sign-on (SSO) technologies.  An extension to
   the CAA [RFC8659] resource record specification is also defined to
   provide domain owners a means to declare a set of SSO providers that
   ACME servers may rely upon when employing SSO for identifier
   validation on their domain.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/bifurcation/acme-sso.

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-
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 11 June 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   4
   4.  ACME email Identifier Type  . . . . . . . . . . . . . . . . .   6
   5.  ACME sso-01 Challenge Type  . . . . . . . . . . . . . . . . .   6
   6.  CAA for Email Address Certificates  . . . . . . . . . . . . .   7
     6.1.  CAA issueemail property . . . . . . . . . . . . . . . . .   8
     6.2.  Usage of the CAA validationmethods Parameter  . . . . . .   8
     6.3.  CAA ssoproviders Parameter  . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Collaboration applications are increasingly using end-to-end
   encryption to protect user content.  These applications frequently
   use email addresses to identify users.  In such contexts, the use of
   X.509 certificates binding email addresses to public keys is a
   natural authentication mechanism.  If the issuer of the certificate
   is separate from the application provider, and validates control of
   the email address independently of the application provider, then the
   resulting certificate can be used to provide end-to-end
   authentication, in the sense that the application provider is unable
   to impersonate the authenticated user.

   Historically, certificates for email addresses have been difficult to
   obtain.  Current end-to-end encrypted communications applications
   typically rely on laborious, error-prone manual authentication
   processes, often based on comparing opaque "security codes" or
   "safety numbers".  Thus, in practice, end-to-end encrypted
   communications are usually vulnerable to impersonation attacks by the
   application provider.

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