Independent Submission P. Saint-Andre
Request for Comments: 7259 &yet
Category: Informational May 2014
ISSN: 2070-1721
The Jabber-ID Header Field
Abstract
This document defines a header field that enables the author of an
email or netnews message to include a Jabber ID in the message header
block for the purpose of associating the author with a particular
Extensible Messaging and Presence Protocol (XMPP) address.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 7259.
Copyright Notice
Copyright (c) 2014 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
(http://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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Inclusion . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Generation . . . . . . . . . . . . . . . . . . . . . . . 3
3.3. Processing . . . . . . . . . . . . . . . . . . . . . . . 4
3.4. Disposition . . . . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security and Privacy Considerations . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 7
1. Introduction
The Extensible Messaging and Presence Protocol (XMPP), documented in
[RFC 6120], 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
[RFC 6121], and XMPP addresses are still referred to as Jabber IDs.
Because almost all human users of Jabber/XMPP instant messaging and
presence systems also use email systems [RFC 5322] and because many
also use netnews systems [RFC 5536], it can be helpful for them to
associate their Jabber IDs with the messages they author. The
Jabber-ID header field provides a standard location for that
information.
Members of the XMPP instant messaging and presence community have
been experimenting with the Jabber-ID header field for many years.
This document defines the syntax and usage of the Jabber-ID header
field, including the information necessary to register the field in
the Provisional Message Header Field Names registry maintained by the
IANA.
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2. Syntax
The syntax of the Jabber-ID header field is defined below using
Augmented Backus-Naur Form [RFC 5234], where the "pathxmpp" rule is
defined in the XMPP URI specification [RFC 5122] and the remaining
rules are defined in the Internet Message Format specification
[RFC 5322]:
Jabber-ID = SP *WSP pathxmpp *WSP CRLF
Although a native XMPP address can contain virtually any Unicode
character [UNICODE], the header of an email or netnews message is
allowed to contain only printable ASCII characters (see Section 2 of
[RFC 5322]). Therefore, any characters outside the ASCII range
[RFC 20] in an XMPP address need to be converted to ASCII before
inclusion in a Jabber-ID header field, in accordance with the rules
defined in the XMPP URI specification [RFC 5122]. In addition,
characters allowed in XMPP localparts and XMPP resourceparts but
disallowed by the relevant URI rules need to be percent-encoded in
accordance with the rules defined in the URI specification [RFC 3986].
3. Usage
3.1. Inclusion
The Jabber-ID header field is associated with the author of the
message; see [RFC 5322]. If the "From:" header field of an email
message contains more than one mailbox, it is best not to add the
Jabber-ID header field to the message. To reduce the possibility of
confusion, it is best to include only one instance of the Jabber-ID
header field in a given message.
3.2. Generation
For a user whose XMPP address is "juliet@example.com", the
corresponding Jabber-ID header field would be:
Jabber-ID: juliet@example.com
As noted, non-ASCII characters in XMPP addresses need to be converted
into ASCII before inclusion in a Jabber-ID header field. Consider
the following XMPP address:
jiři@čechy.example
In the foregoing example, 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,
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following the "XML Notation" used in [RFC 3987] to represent
characters that cannot be rendered in ASCII-only documents. For
those who do not read Czech, this example could be anglicized as
"george@czech-lands.example".
Following the rules in [RFC 5122] and the Jabber-ID header field
syntax, the resulting header field might be as shown below (note that
this representation includes folding white space, which is allowed in
accordance with the ABNF):
Jabber-ID:
ji%C5%99i@%C4%8Dechy.example
3.3. Processing
Upon receiving an email message or netnews message containing a
Jabber-ID header field, a user agent that supports the field ought to
process the field by converting any escaped characters to characters
outside the ASCII range in accordance with the rules defined in
[RFC 5122], thus yielding a Jabber ID that can be used for native
communication on the XMPP network.
3.4. Disposition
A user agent that has processed a Jabber-ID header field can provide
appropriate interface elements if it has independent information
linking the author of the email or netnews message with the specified
Jabber ID (e.g., via a user-controlled address book or automated
directory lookup). Such interface elements might include an
indicator of "presence" (i.e., that the author is online and
available for communication via XMPP) if the user is subscribed to
the presence of the author, and an element that enables the user to
send an instant message or initiate a text chat session with the
author.
4. IANA Considerations
The IANA has added "Jabber-ID" to the Provisional Message Header
Field Names registry. The completed registration template follows.
Header field name: Jabber-ID
Applicable protocol: mail, netnews
Status: provisional
Author/Change controller Peter Saint-Andre <stpeter@jabber.org>
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Specification document: RFC 7259
Related information: See RFC 6120
5. Security and Privacy Considerations
Message headers are an existing standard and are designed to easily
accommodate new types. Although the Jabber-ID header field could be
forged, this problem is inherent in Internet email and netnews.
However, because a forged Jabber-ID header field might break
automated processing, applications are discouraged from depending on
the Jabber-ID header field to indicate the authenticity of an email
or netnews message, or the identity of its author or sender.
Including the Jabber-ID header field among the signer header fields
in DomainKeys Identified Mail (DKIM) can help to mitigate against
forging of the header (see [RFC 6376]).
Advertising XMPP addresses in email or netnews headers might 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. Providing such a binding between an
email address and a Jabber ID can also increase the possibility of
drawing a connection between different kinds of communications
traffic for purposes of surveillance and other breaches of privacy.
Care ought to be taken in balancing the benefits of open information
exchange against the potential costs of security and privacy
weaknesses. An email or netnews user agent that is capable of
including the Jabber-ID header field in outgoing email or netnews
messages needs to provide an option for its user to disable inclusion
of the Jabber-ID header field generally, on a per-recipient basis,
and on a per-message basis.
The security and privacy considerations discussed in [RFC 3986],
[RFC 3987], [RFC 5122], [RFC 6120], and [RFC 6121] also apply to the
Jabber-ID message header.
6. References
6.1. Normative References
[RFC 3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005.
[RFC 3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
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[RFC 5122] Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)", RFC
5122, February 2008.
[RFC 5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC 5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008.
[RFC 6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
6.3", (Mountain View, CA: The Unicode Consortium, 2013.
ISBN 978-1-936213-08-5),
<http://www.unicode.org/versions/Unicode6.3.0/>.
6.2. Informative References
[RFC 20] Cerf, V., "ASCII format for network interchange", RFC 20,
October 1969.
[RFC 5536] Murchison, K., Lindsey, C., and D. Kohn, "Netnews Article
Format", RFC 5536, November 2009.
[RFC 6121] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", RFC
6121, March 2011.
[RFC 6376] Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys
Identified Mail (DKIM) Signatures", RFC 6376, September
2011.
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Appendix A. Acknowledgements
Thanks to Dave Cridland, Stephen Farrell, Russ Housley, and Alexey
Melnikov for their feedback.
Author's Address
Peter Saint-Andre
&yet
EMail: ietf@stpeter.im
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