Internet-Draft Use of EAI in EPP July 2021
Belyavskiy & Gould Expires 26 January 2022 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-regext-epp-eai-01
Published:
Intended Status:
Standards Track
Expires:
Authors:
D. Belyavskiy
J. Gould
VeriSign, Inc.

Use of Internationalized Email Addresses in EPP protocol

Abstract

This document describes an EPP extension that permits usage of Internationalized Email Addresses in the EPP protocol and specifies the terms when it can be used by EPP clients and servers. The Extensible Provisioning Protocol (EPP), being developed before appearing the standards for Internationalized Email Addresses (EAI), does not support such email addresses.

TO BE REMOVED on turning to RFC: The document is edited in the dedicated github repo. Please send your submissions via GitHub.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on 26 January 2022.

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Table of Contents

1. Introduction

[RFC6530] introduced the framework for Internationalized Email Addresses. To make such addresses more widely accepted, the changes to various protocols need to be introduced.

This document describes an Extensible Provisioning Protocol (EPP) extension that permits usage of Internationalized Email Addresses in the EPP protocol and specifies the terms when it can be used by EPP clients and servers. A new form of EPP extension, referred to as a Functional Extension, is defined and used to apply the rules for the handling of email address elements in all of the [RFC5730] extensions negotiated in the EPP session, which include the object and command-responses extensions. The described mechanism can be applied to any object or command-response extension that uses an email address.

The Extensible Provisioning Protocol (EPP) specified in [RFC5730] is a base document for object management operations and an extensible framework that maps protocol operations to objects. The specifics of various objects managed via EPP is described in separate documents. This document is only referring to an email address as a property of a managed object, such as the <contact:email> element in the EPP contact mapping [RFC5733] or the <org:email> element in the EPP organization mapping [RFC8543], and command-response extensions applied to a managed object.

1.1. 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.

2. Migrating to Newer Versions of This Extension

Servers that implement this extension SHOULD provide a way for clients to progressively update their implementations when a new version of the extension is deployed. A newer version of the extension is expected to use an XML namespace with a higher version number than the prior versions.

3. Email Address Specification

Support of non-ASCII email address syntax is defined in RFC 6530 [RFC6530]. This mapping does not prescribe minimum or maximum lengths for character strings used to represent email addresses. The exact syntax of such addresses is described in Section 3.3 of [RFC6531]. The validation rules introduced in RFC 6531 are considered to be followed.

The definition of email address in the EPP RFCs, including Section 2.6 of [RFC5733] and Section 4.1.2, 4.2.1, and 4.2.5 of [RFC8543], references [RFC5322] for the email address syntax. The XML schema definition in Section 4 of [RFC5733] and Section 5 of [RFC8543] defines the "email" element using the type "eppcom:minTokenType", which is defined in Section 4.2 of [RFC5730] as an XML schema "token" type with minimal length of one. The XML schema "token" type will fully support the use of EAI addresses, so the primary application of the EAI extension is to apply the use of [RFC6531] instead of [RFC5322] for the email address syntax. Other EPP extensions may follow the formal syntax definition using the XML schema type "eppcom:minTokenType" and the [RFC5322] format specification, where this extension applies to all EPP extensions with the same or similar definitions.

The email address format is formally defined in Section 3.4.1 of [RFC5322], which only consists of printable US-ASCII characters for both the local-part and the domain ABNF rules. In [RFC6531], the extends the Mailbox, Local-part and Domain ABNF rules in [RFC5321] to support "UTF8-non-ascii", defined in Section 3.1 of [RFC6532], for the local-part and U-label, defined in Section 2.3.2.1 of [RFC5890], for the domain. By applying the syntax rules of [RFC5322], the EPP extensions will change from supporting only ASCII characters to supporting Internationailzed characters both in the email address local-part and domain-part.

4. Functional Extension

[RFC5730] defines three types of extensions at the protocol, object, and command-response level, which impact the structure of the EPP messages. A Functional Extension applies a functional capability to an existing set of EPP extensions and properties. The scope of the applicable EPP extensions and applicable extension properties are defined in the Functional Extension along with the requirements for the servers and clients that support it. The Functional Extension needs to cover the expected behavior of the supporting client or server when interacting with an unsupporting client or server. Negotiating support for a Functional Extension is handled using the EPP Greeting and EPP Login services.

5. Internationalized Email Addresses (EAI) Functional Extension

5.1. Scope of Functional Extension

The functional extension applies to all object extensions and command-response extensions negotiated in the EPP session that include email address properties. Examples include the <contact:email> element in the EPP contact mapping [RFC5733] or the <org:email> element in the EPP organization mapping [RFC8543]. All registry zones (e.g., top-level domains) authorized for the client in the EPP session apply. There is no concept of a per-client, per-zone, per-extension, or per-field setting that is used to indicate support for EAI, but instead it's a global setting that applies to the EPP session.

5.2. Signaling Client and Server Support

The client and the server can signal support for the functional extension using a namespace URI in the login and greeting extension services respectively. The namespace URI "urn:ietf:params:xml:ns:epp:eai-0.2" is used to signal support for the functional extension. The client includes the namespace URI in an <svcExtension> <extURI> element of the [RFC5730] <login> Command. The server includes the namespace URI in an <svcExtension> <extURI> element of the [RFC5730] Greeting.

5.3. Functional Extension Behavior

5.3.1. EAI Functional Extension Negotiated

If both client and server have indicated the support of the EAI addresses during the session establishment, it implies possibility to process the EAI address in any message having an email property during the established EPP session. Below are the server and client obligations when the EAI extension has been successfuly negotiated in the EPP session.

The server MUST satisfy the following obligations when the EAI extension has been negotiated:

  • Accept EAI compatible addresses for all email properties in the EPP session negotiated object extensions and command-response extensions. For example the <contact:email> element in [RFC5733] and the <org:email> element in [RFC8543].
  • Accept EAI compatible addresses for all registry zones (e.g., top-level domains) authorized for the client in the EPP session.
  • Email address validation based on EAI validation rules defined in Section 3
  • Storage of email properties that supports internationalized characters.
  • Return EAI compatible addresses for all email properties in the EPP responses.

The client MUST satisfy the following obligations when THE EAI extension has been negotiated:

  • Provide EAI compatible addresses for all e-mail properties in the EPP session negotiated object extensions and command-response extensions. For example the <contact:email> element in [RFC5733] and the <org:email> element in [RFC8543].
  • Provide EAI compatible addresses for all registry zones (e.g., top-level domains) authorized for the client in the EPP session.
  • Accept EAI compatible addresses in the EPP responses for all email properties in the EPP session negotiated object extensions and command-response extensions.

5.3.2. EAI Functional Extension Not Negotiated

The lack of EAI support can cause data and functional issues, so an EAI supporting client or server needs to handle cases where the opposite party doesn't support EAI. Below are the server and client obligations when the EAI extension is not negotiated due to the lack of support by the peer.

The EAI supporting server MUST satisfy the following obligations when the client does not support the EAI extension:

  • When the email property is required in the EPP extension command, the server SHOULD validate the email property sent by the client using the ASCII email validation rules.
  • When the email property is optional according the EPP extension command, if the client supplies the email property the server SHOULD validate the email property using the ASCII email validation rules.
  • When the email property is required in the EPP extension response, the server MUST validate whether the email property is an EAI address and if so return the predefined placeholder email (see below) and otherwise return the email property that has been set.
  • When the email property is optional in the EPP extension response, the server MUST validate whether the email property is an EAI address and if so don't return the email property in the response and otherwise return the email property that has been set based on server policy.

The EAI supporting client MUST satisfy the following obligations when the server does not support the EAI extension:

  • When the email property is required in the EPP extension command and the email property is an EAI address with no alternative ASCII address, the client MUST provide the predefined placeholder email address (see below).
  • When the email property is optional in the EPP extension command and the email property is an EAI address with no alternative ASCII address, the client SHOULD omit the email property.

5.3.3. EAI Placeholder Email Address

A valid email value needs to be provided to a non-EAI supporting client or server to satisfy a required email property when all that is available is an EAI value. To satisfy this requirement, a predefined placeholder email needs to be selected that meets the requirements:

  • A syntactically valid email address to pass client or server validation logic.
  • A non-EAI email address since the client or server doesn't support EAI email addresses.
  • A single value that can indicate the lack of EAI support to the client or server.
  • An email address that is blackholed and never delivered.
  • Use of the email address will not cause operational issues.

RFC 7535 [RFC7535] defines a blackholed domain name with EMPTY.AS112.ARPA, which can be leveraged for the EAI predefined placeholder email. The proposal is to define the predefined placeholder email value as EAI@EMPTY.AS112.ARPA.

6. Security Considerations

Registries SHOULD validate the domain names in the provided email addresses. This can be done by validating all code points according to IDNA2008 [RFC5892].

7. IANA Considerations

7.1. XML Namespace

This document uses URNs to describe XML namespaces and XML schemas conforming to a registry mechanism described in RFC 3688 [RFC3688]. The following URI assignment should be made by IANA:

Registration request for the eai namespace:

   URI:  urn:ietf:params:xml:ns:epp:eai-0.2
   Registrant Contact:  IESG
   XML:  None.  Namespace URIs do not represent an XML specification.

   Registration request for the eai XML Schema:

   URI:  urn:ietf:params:xml:schema:epp:eai-0.2
   Registrant Contact:  IESG
   XML:  See the "Formal Syntax" section of this document.

7.2. EPP Extension Registry

The EPP extension described in this document should be registered by IANA in the "Extensions for the Extensible Provisioning Protocol (EPP)" registry described in RFC 7451 [RFC7451]. The details of the registration are as follows:

   Name of Extension: Use of Internationalized Email Addresses
                      in EPP protocol
   Document status:  Standards Track
   Reference:  TBA
   Registrant Name and Email Address:  IESG, <iesg@ietf.org>
   Top-Level Domains(TLDs):  Any
   IPR Disclosure:  None
   Status:  Active
   Notes:  None

8. Implementation Considerations

Registries MAY apply extra limitation to the email address syntax (e.g. the addresses can be limited to Left-to-Right scripts). These limitations are out of scope of this document.

9. References

9.1. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.27487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.27487/RFC3688, , <https://www.rfc-editor.org/info/rfc3688>.
[RFC5321]
Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, DOI 10.17487/RFC5321, , <https://www.rfc-editor.org/info/rfc5321>.
[RFC5322]
Resnick, P., Ed., "Internet Message Format", RFC 5322, DOI 10.17487/RFC5322, , <https://www.rfc-editor.org/info/rfc5322>.
[RFC5730]
Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", STD 69, RFC 5730, DOI 10.27487/RFC5730, , <https://www.rfc-editor.org/info/rfc5730>.
[RFC5733]
Hollenbeck, S., "Extensible Provisioning Protocol (EPP) Contact Mapping", STD 69, RFC 5733, DOI 10.27487/RFC5733, , <https://www.rfc-editor.org/info/rfc5733>.
[RFC5890]
Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, , <https://www.rfc-editor.org/info/rfc5890>.
[RFC6530]
Klensin, J. and Y. Ko, "Overview and Framework for Internationalized Email", RFC 6530, DOI 10.27487/RFC6530, , <https://www.rfc-editor.org/info/rfc6530>.
[RFC6531]
Yao, J. and W. Mao, "SMTP Extension for Internationalized Email", RFC 6531, DOI 10.17487/RFC6531, , <https://www.rfc-editor.org/info/rfc6531>.
[RFC6532]
Yang, A., Steele, S., and N. Freed, "Internationalized Email Headers", RFC 6532, DOI 10.17487/RFC6532, , <https://www.rfc-editor.org/info/rfc6532>.
[RFC7451]
Hollenbeck, S., "Extension Registry for the Extensible Provisioning Protocol", RFC 7451, DOI 10.27487/RFC7451, , <https://www.rfc-editor.org/info/rfc7451>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.27487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.

9.2. Informative References

[RFC5892]
Faltstrom, P., Ed., "The Unicode Code Points and Internationalized Domain Names for Applications (IDNA)", RFC 5892, DOI 10.27487/RFC5892, , <https://www.rfc-editor.org/info/rfc5892>.
[RFC7535]
Abley, J., Dickson, B., Kumari, W., and G. Michaelson, "AS112 Redirection Using DNAME", RFC 7535, DOI 10.17487/RFC7535, , <https://www.rfc-editor.org/info/rfc7535>.
[RFC8543]
Zhou, L., Kong, N., Yao, J., Gould, J., and G. Zhou, "Extensible Provisioning Protocol (EPP) Organization Mapping", RFC 8543, DOI 10.27487/RFC8543, , <https://www.rfc-editor.org/info/rfc8543>.

Appendix A. Change History

A.1. Change from 00 to 01

  1. Changed from update of RFC 5733 to use the "Placeholder Text and a New Email Element" EPP Extension approach.

A.2. Change from 01 to 02

  1. Fixed the XML schema and the XML examples based on validating them.
  2. Added James Gould as co-author.
  3. Updated the language to apply to any EPP object mapping and to use the EPP contact mapping as an example.
  4. Updated the structure of document to be consistent with the other Command-Response Extensions.
  5. Replaced the use of "eppEAI" in the XML namespace and the XML namespace prefix with "eai".
  6. Changed to use a pointed XML namespace with "0.2" instead of "1.0".

A.3. Change from 02 to 03

  1. The approach has changed to use the concept of Functional EPP Extension.
  2. The examples are removed

A.4. Change from 03 to 04

  1. More detailed reference to email syntax is provided
  2. The shortened eai namespace reference is removed

Authors' Addresses

Dmitry Belyavskiy
8 marta st.
Moscow
127083
Russian Federation
Phone: +7 916 262 5593
James Gould
VeriSign, Inc.
12061 Bluemont Way
Reston, VA 20190
United States of America
URI: http://www.verisigninc.com