Internationalized Email Addresses in X.509 Certificates
RFC 8398

Document Type RFC - Proposed Standard (May 2018; Errata)
Updates RFC 5280
Last updated 2018-07-11
Replaces draft-melnikov-spasm-eai-addresses
Stream IETF
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Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Russ Housley
Shepherd write-up Show (last changed 2016-12-27)
IESG IESG state RFC 8398 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Eric Rescorla
Send notices to "Russ Housley" <housley@vigilsec.com>
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack
Internet Engineering Task Force (IETF)                  A. Melnikov, Ed.
Request for Comments: 8398                                     Isode Ltd
Updates: 5280                                             W. Chuang, Ed.
Category: Standards Track                                   Google, Inc.
ISSN: 2070-1721                                                 May 2018

        Internationalized Email Addresses in X.509 Certificates

Abstract

   This document defines a new name form for inclusion in the otherName
   field of an X.509 Subject Alternative Name and Issuer Alternative
   Name extension that allows a certificate subject to be associated
   with an internationalized email address.

   This document updates RFC 5280.

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/rfc8398.

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
   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.

Melnikov & Chuang            Standards Track                    [Page 1]
RFC 8398        I18N Mail Addresses in X.509 Certificates       May 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   3.  Name Definitions  . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IDNA2008  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Matching of Internationalized Email Addresses in X.509
       Certificates  . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Name Constraints in Path Validation . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  ASN.1 Module . . . . . . . . . . . . . . . . . . . .  10
   Appendix B.  Example of SmtpUTF8Mailbox . . . . . . . . . . . . .  11
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   [RFC5280] defines the rfc822Name subjectAltName name type for
   representing email addresses as described in [RFC5321].  The syntax
   of rfc822Name is restricted to a subset of US-ASCII characters and
   thus can't be used to represent internationalized email addresses
   [RFC6531].  This document defines a new otherName variant to
   represent internationalized email addresses.  In addition this
   document requires all email address domains in X.509 certificates to
   conform to IDNA2008 [RFC5890].

2.  Conventions Used in This Document

   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.

   The formal syntax uses the Augmented Backus-Naur Form (ABNF)
   [RFC5234] notation.

Melnikov & Chuang            Standards Track                    [Page 2]
RFC 8398        I18N Mail Addresses in X.509 Certificates       May 2018

3.  Name Definitions

   The GeneralName structure is defined in [RFC5280] and supports many
   different name forms including otherName for extensibility.  This
   section specifies the SmtpUTF8Mailbox name form of otherName so that
   internationalized email addresses can appear in the subjectAltName of
   a certificate, the issuerAltName of a certificate, or anywhere else
   that GeneralName is used.

   id-on-SmtpUTF8Mailbox OBJECT IDENTIFIER ::= { id-on 9 }

   SmtpUTF8Mailbox ::= UTF8String (SIZE (1..MAX))
   -- SmtpUTF8Mailbox conforms to Mailbox as specified
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