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Independent Submission                                    P. Saint-AndreRequest for Comments: 7259                                          &yetCategory: Informational                                         May 2014ISSN: 2070-1721The Jabber-ID Header FieldAbstract   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; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7259.Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Saint-Andre                   Informational                     [Page 1]

RFC 7259                        Jabber-ID                       May 2014Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . . . .33.  Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . .33.1.  Inclusion . . . . . . . . . . . . . . . . . . . . . . . .33.2.  Generation  . . . . . . . . . . . . . . . . . . . . . . .33.3.  Processing  . . . . . . . . . . . . . . . . . . . . . . .43.4.  Disposition . . . . . . . . . . . . . . . . . . . . . . .44.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .45.  Security and Privacy Considerations . . . . . . . . . . . . .56.  References  . . . . . . . . . . . . . . . . . . . . . . . . .56.1.  Normative References  . . . . . . . . . . . . . . . . . .56.2.  Informative References  . . . . . . . . . . . . . . . . .6Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .71.  Introduction   The Extensible Messaging and Presence Protocol (XMPP), documented in   [RFC6120], 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   [RFC6121], 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 [RFC5322] and because many   also use netnews systems [RFC5536], 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.Saint-Andre                   Informational                     [Page 2]

RFC 7259                        Jabber-ID                       May 20142.  Syntax   The syntax of the Jabber-ID header field is defined below using   Augmented Backus-Naur Form [RFC5234], where the "pathxmpp" rule is   defined in the XMPP URI specification [RFC5122] and the remaining   rules are defined in the Internet Message Format specification   [RFC5322]:      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 (seeSection 2 of   [RFC5322]).  Therefore, any characters outside the ASCII range   [RFC20] 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 [RFC5122].  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 [RFC3986].3.  Usage3.1.  Inclusion   The Jabber-ID header field is associated with the author of the   message; see [RFC5322].  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,Saint-Andre                   Informational                     [Page 3]

RFC 7259                        Jabber-ID                       May 2014   following the "XML Notation" used in [RFC3987] 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 [RFC5122] 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.example3.3.  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   [RFC5122], 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>Saint-Andre                   Informational                     [Page 4]

RFC 7259                        Jabber-ID                       May 2014   Specification document:RFC 7259   Related information:  SeeRFC 61205.  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 [RFC6376]).   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 [RFC3986],   [RFC3987], [RFC5122], [RFC6120], and [RFC6121] also apply to the   Jabber-ID message header.6.  References6.1.  Normative References   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform              Resource Identifier (URI): Generic Syntax", STD 66,RFC3986, January 2005.   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource              Identifiers (IRIs)",RFC 3987, January 2005.Saint-Andre                   Informational                     [Page 5]

RFC 7259                        Jabber-ID                       May 2014   [RFC5122]  Saint-Andre, P., "Internationalized Resource Identifiers              (IRIs) and Uniform Resource Identifiers (URIs) for the              Extensible Messaging and Presence Protocol (XMPP)",RFC5122, February 2008.   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax              Specifications: ABNF", STD 68,RFC 5234, January 2008.   [RFC5322]  Resnick, P., Ed., "Internet Message Format",RFC 5322,              October 2008.   [RFC6120]  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   [RFC20]    Cerf, V., "ASCII format for network interchange",RFC 20,              October 1969.   [RFC5536]  Murchison, K., Lindsey, C., and D. Kohn, "Netnews Article              Format",RFC 5536, November 2009.   [RFC6121]  Saint-Andre, P., "Extensible Messaging and Presence              Protocol (XMPP): Instant Messaging and Presence",RFC6121, March 2011.   [RFC6376]  Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys              Identified Mail (DKIM) Signatures",RFC 6376, September              2011.Saint-Andre                   Informational                     [Page 6]

RFC 7259                        Jabber-ID                       May 2014Appendix 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.imSaint-Andre                   Informational                     [Page 7]