The Jabber-ID Header Field
draft-saintandre-jabberid-04

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Copyright Notice

Copyright © The IETF Trust (2006).

Abstract

This document defines a header field that enables a sender to include a Jabber Identifier in the header block of an email message for the purpose of associating the email message or sender with a particular Extensible Messaging and Presence Protocol (XMPP) address.

Table of Contents

1.  Introduction
2.  Jabber-ID Syntax
3.  Examples
4.  IANA Considerations
5.  Security Considerations
6.  References
    6.1.  Normative References
    6.2.  Informative References
§  Author's Address
§  Intellectual Property and Copyright Statements

1.  Introduction

The Extensible Messaging and Presence Protocol (XMPP), documented in [RFC3920] (Saint-Andre, P., “Extensible Messaging and Presence Protocol (XMPP): Core,” October 2004.), is a streaming XML technology that enables any two entities on a network to exchange well-defined but extensible XML elements (called "XML stanzas") in close to real time. Given XMPP's heritage in the Jabber open-source community, one of the primary uses for XMPP is instant messaging and presence as documented in [RFC3921] (Saint-Andre, P., “Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence,” October 2004.), and XMPP addresses are still referred to as Jabber Identifiers or Jabber IDs.

Because almost all users of Jabber instant messaging and presence systems are users of email systems, it can be helpful for such users to specify their Jabber Identifiers in the email messages they send. The Jabber-ID header defined in this document provides a standard location for that information.

2.  Jabber-ID Syntax

The syntax of the Jabber-ID header is defined below using Augmented Backus-Naur Form (as specified by [RFC4234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” October 2005.)), where the "pathxmpp" rule is defined in [RFC4622] (Saint-Andre, P., “Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP),” July 2006.) and the remaining rules are defined in [RFC2822] (Resnick, P., “Internet Message Format,” April 2001.):

"Jabber-ID:" [FWS] pathxmpp (*WSP / obs-FWS) CRLF

Note: Although a native XMPP address may contain virtually any [UNICODE] (The Unicode Consortium, “The Unicode Standard, Version 3.2.0,” 2000.) character, an electronic mail header may contain only printable [US‑ASCII] (American National Standards Institute, “Coded Character Set - 7-bit American Standard Code for Information Interchange,” 1986.) characters (see Section 2 of [RFC2822] (Resnick, P., “Internet Message Format,” April 2001.)). Therefore, any non-US-ASCII characters in an XMPP address must be converted to US-ASCII before inclusion in a Jabber-ID header, in accordance with the rules specified in [RFC4622] (Saint-Andre, P., “Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP),” July 2006.).

3.  Examples

For a user whose XMPP address is "juliet@example.com", the corresponding Jabber-ID header would be:

Jabber-ID: juliet@example.com

As noted, non-US-ASCII characters in XMPP addresses must be converted into US-ASCII before inclusion in a Jabber-ID header. Consider the following XMPP address:

jiři@čechy.example

Note: The string "ř" stands for the Unicode character LATIN SMALL LETTER R WITH CARON and the string "č" stands for the Unicode character LATIN SMALL LETTER C WITH CARON, following the "XML Notation" used in [RFC3987] (Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs),” January 2005.) to represent characters that cannot be rendered in ASCII-only documents (note also that these characters are represented in their stringprep canonical form; see [RFC3454] (Hoffman, P. and M. Blanchet, “Preparation of Internationalized Strings ("stringprep"),” December 2002.)). For those who do not read Czech, this example could be Anglicized as "george@czech-lands.example".

Following the rules in [RFC4622] (Saint-Andre, P., “Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP),” July 2006.) and the Jabber-ID header syntax, the resulting header would be:

Jabber-ID: ji%C5%99i@%C4%8Dechy.example

4.  IANA Considerations

In accordance with [RFC3864] (Klyne, G., Nottingham, M., and J. Mogul, “Registration Procedures for Message Header Fields,” September 2004.), the IANA registers the "Jabber-ID" header field in the Permanent Message Header Field Registry. The registration template is as follows:

Header field name:

Jabber-ID

Applicable protocol:

mail

Status:

standard

Author/Change controller:

IETF

Specification document(s):

XXXX

Related information:

For details regarding the native usage and format of Jabber Identifiers, see Extensible Messaging and Presence Protocol (RFC 3920).

5.  Security Considerations

Message headers are an existing standard and are designed to easily accommodate new types. Although the Jabber-ID header may be forged, this problem is inherent in Internet email; however, because a forged Jabber-ID header may break automated processing, applications should not depend on the Jabber-ID header to indicate the authenticity of an email message or the identity of its sender.

Advertising XMPP addresses in email headers may make it easier for malicious users to harvest XMPP addresses and therefore to send unsolicited bulk communications to the users or applications represented by those addresses. Care should be taken in balancing the benefits of open information exchange against the potential costs of unwanted communications. An email user agent that is capable of including the Jabber-ID header field in outgoing email messages should provide an option for its user to disable inclusion of the Jabber-ID header field generally, on a per-recipient basis, or on a per-message basis.

6.  References

6.1. Normative References

6.2. Informative References

Author's Address

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