Network Working Group P. Saint-Andre Internet-Draft Cisco Intended status: Standards Track July 26, 2010 Expires: January 27, 2011 Extensible Messaging and Presence Protocol (XMPP): Address Format draft-ietf-xmpp-address-03 Abstract This document defines the format for addresses used in the Extensible Messaging and Presence Protocol (XMPP), including support for non- ASCII characters. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 27, 2011. Copyright Notice Copyright (c) 2010 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. 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. Saint-Andre Expires January 27, 2011 [Page 1]
Internet-Draft XMPP Address Format July 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 6 3. Internationalization Considerations . . . . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 4.1. Reuse of Stringprep . . . . . . . . . . . . . . . . . . . 8 4.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 8 4.3. Confusable Characters . . . . . . . . . . . . . . . . . . 8 4.4. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 9 4.4.1. Address Forging . . . . . . . . . . . . . . . . . . . 9 4.4.2. Address Mimicking . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 5.1. Nodeprep Profile of Stringprep . . . . . . . . . . . . . . 11 5.2. Resourceprep Profile of Stringprep . . . . . . . . . . . . 11 6. Conformance Requirements . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1. Normative References . . . . . . . . . . . . . . . . . . . 13 7.2. Informative References . . . . . . . . . . . . . . . . . . 14 Appendix A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . 15 A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 16 A.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 16 A.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 16 A.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 16 A.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 16 A.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 17 A.7. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Appendix B. Resourceprep . . . . . . . . . . . . . . . . . . . . 18 B.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 18 B.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 18 B.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 19 B.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 19 B.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 19 B.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 19 Appendix C. Differences From RFC 3920 . . . . . . . . . . . . . . 19 Appendix D. Copying Conditions . . . . . . . . . . . . . . . . . 20 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20 Saint-Andre Expires January 27, 2011 [Page 2]
Internet-Draft XMPP Address Format July 2010 1. Introduction The Extensible Messaging and Presence Protocol [XMPP] is an application profile of the Extensible Markup Language [XML] for streaming XML data in close to real time between any two or more network-aware entities. The address format for XMPP entities was originally developed in the Jabber open-source community in 1999, first described by [XEP-0029] in 2002, and defined canonically by [RFC3920] in 2004. As specified in RFC 3920, the XMPP address format re-uses the "stringprep" technology for preparation of non-ASCII characters [STRINGPREP], including the Nameprep profile for internationalized domain names as specified in [NAMEPREP] and [IDNA2003] along with two XMPP-specific profiles for the localpart and resourcepart. However, since the publication of RFC 3920, IDNA2003 has been superseded by IDNA2008 (see [IDNA-PROTO] and related documents). As a result, other protocols that use stringprep (including XMPP) have begun to migrate from stringprep toward more "modern" approaches. Because work on improved handling of internationalized addresses is currently in progress, specifying the XMPP address format in the specification that obsoletes RFC 3920 would unacceptably delay the revision process. Therefore, this specification provides updated documentation of the XMPP address format (essentially copied from RFC 3920), with the intent that it can be superseded once work on a new approach to internationalization is complete. 2. Addresses 2.1. Overview An XMPP entity is anything that is network-addressable and that can communicate using XMPP. For historical reasons, the native address of an XMPP entity is called a Jabber Identifier or JID. A valid JID is a string of [UNICODE] code points, encoded using [UTF-8], and structured as an ordered sequence of localpart, domainpart, and resourcepart (where the first two parts are demarcated by the '@' character used as a separator, and the last two parts are similarly demarcated by the '/' character). The syntax for a JID is defined as follows using the Augmented Backus-Naur Form as specified in [ABNF]. Saint-Andre Expires January 27, 2011 [Page 3]
Internet-Draft XMPP Address Format July 2010 jid = [ localpart "@" ] domainpart [ "/" resourcepart ] localpart = 1*(nodepoint) ; a "nodepoint" is a UTF-8 encoded Unicode code ; point that satisfies the Nodeprep profile of ; stringprep domainpart = IP-literal / IPv4address / ifqdn ; the "IPv4address" and "IP-literal" rules are ; defined in RFC 3986, and the first-match-wins ; (a.k.a. "greedy") algorithm described in RFC ; 3986 applies to the matching process ifqdn = 1*(namepoint) ; a "namepoint" is a UTF-8 encoded Unicode ; code point that satisfies the Nameprep ; profile of stringprep resourcepart = 1*(resourcepoint) ; a "resourcepoint" is a UTF-8 encoded Unicode ; code point that satisfies the Resourceprep ; profile of stringprep All JIDs are based on the foregoing structure. One common use of this structure is to identify a messaging and presence account, the server that hosts the account, and a connected resource (e.g., a specific device) in the form of <localpart@domain/resource>. However, localparts other than clients are possible; for example, a specific chat room offered by a multi-user chat service (see [XEP-0045]) is addressed as <room@service> (where "room" is the name of the chat room and "service" is the hostname of the multi-user chat service) and a specific occupant of such a room could be addressed as <room@service/nick> (where "nick" is the occupant's room nickname). Many other JID types are possible (e.g., <domain/resource> could be a server-side script or service). Each allowable portion of a JID (localpart, domainpart, and resourcepart) MUST NOT be zero bytes in length and MUST NOT be more than 1023 bytes in length, resulting in a maximum total size (including the '@' and '/' separators) of 3071 bytes. An entity's address on an XMPP network MUST be represented as a JID (without a URI scheme) and not a [URI] or [IRI] as specified in [XMPP-URI]; the latter specification is provided only for identification and interaction outside the context of XMPP itself. Implementation Note: When dividing a JID into its component parts, an implementation needs to match the separator characters '@' and '/' before applying any transformation algorithms, which might decompose certain Unicode code points to the separator characters (e.g., U+FE6B SMALL COMMERCIAL AT might decompose into U+0040 COMMERCIAL AT). Saint-Andre Expires January 27, 2011 [Page 4]
Internet-Draft XMPP Address Format July 2010 2.2. Domainpart The DOMAINPART of a JID is that portion after the '@' character (if any) and before the '/' character (if any); it is the primary identifier and is the only REQUIRED element of a JID (a mere domainpart is a valid JID). Typically a domainpart identifies the "home" server to which clients connect for XML routing and data management functionality. However, it is not necessary for an XMPP domainpart to identify an entity that provides core XMPP server functionality (e.g., a domainpart can identify an entity such as a multi-user chat service, a publish-subscribe service, or a user directory). The domainpart for every server or service that will communicate over a network SHOULD be a fully qualified domain name or "FQDN" (see [DNS]); although the domainpart is allowed to be either an Internet Protocol (IPv4 or IPv6) address or a text label that is resolvable on a local network (commonly called an "unqualified hostname"), it is possible that domainparts that are IP addresses will not be acceptable to other services for the sake of interdomain communication. Furthermore, domainparts that are unqualified hostnames MUST NOT be used on public networks but MAY be used on private networks. Note: If the domainpart includes a final character considered to be a label separator (dot) by [IDNA2003] or [DNS], this character MUST be stripped from the domainpart before the JID of which it is a part is used for the purpose of routing an XML stanza, comparing against another JID, or constructing an [XMPP-URI]; in particular, the character MUST be stripped before any other canonicalization steps are taken, such as application of the [NAMEPREP] profile of [STRINGPREP] or completion of the ToASCII operation as described in [IDNA2003]. A domainpart MUST NOT be zero bytes in length and MUST NOT be more than 1023 bytes in length. A domainpart consisting of a fully qualified domain name MUST be an "internationalized domain name" as defined in [IDNA2003], that is, it MUST be "a domain name in which every label is an internationalized label" and MUST follow the rules for construction of internationalized domain names specified in [IDNA2003]. When preparing a text label (consisting of a sequence of UTF-8 encoded Unicode code points) for representation as an internationalized label in the process of constructing an XMPP domainpart or comparing two XMPP domainparts, an application MUST ensure that for each text label it is possible to apply without failing the ToASCII operation specified in [IDNA2003] with the UseSTD3ASCIIRules flag set (thus Saint-Andre Expires January 27, 2011 [Page 5]
Internet-Draft XMPP Address Format July 2010 forbidding ASCII code points other than letters, digits, and hyphens). If the ToASCII operation can be applied without failing, then the label is an internationalized label. (Note: The ToASCII operation includes application of the [NAMEPREP] profile of [STRINGPREP] and encoding using the algorithm specified in [PUNYCODE]; for details, see [IDNA2003].) Although XMPP applications do not communicate the output of the ToASCII operation (called an "ACE label") over the wire, it MUST be possible to apply that operation without failing to each internationalized label. If an XMPP application receives as input an ACE label, it SHOULD convert that ACE label to an internationalized label using the ToUnicode operation (see [IDNA2003]) before including the label in an XMPP domainpart that will be communicated over the wire on an XMPP network (however, instead of converting the label, there are legitimate reasons why an application might instead refuse the input altogether and return an error to the entity that provided the offending data). In the terms of IDNA2008 [IDNA-DEFS], the domainpart of a JID is a "domain name slot". 2.3. Localpart The LOCALPART of a JID is an optional identifier placed before the domainpart and separated from the latter by the '@' character. Typically a localpart uniquely identifies the entity requesting and using network access provided by a server (i.e., a local account), although it can also represent other kinds of entities (e.g., a chat room associated with a multi-user chat service). The entity represented by an XMPP localpart is addressed within the context of a specific domain. A localpart MUST NOT be zero bytes in length and MUST NOT be more than 1023 bytes in length. A localpart MUST be formatted such that the Nodeprep profile of [STRINGPREP] can be applied without failing (see Appendix A). Before comparing two localparts, an application MUST first ensure that the Nodeprep profile has been applied to each identifier (the profile need not be applied each time a comparison is made, as long as it has been applied before comparison). 2.4. Resourcepart The resourcepart of a JID is an optional identifier placed after the domainpart and separated from the latter by the '/' character. A resourcepart can modify either a <localpart@domainpart> address or a mere <domainpart> address. Typically a resourcepart uniquely identifies a specific connection (e.g., a device or location) or Saint-Andre Expires January 27, 2011 [Page 6]
Internet-Draft XMPP Address Format July 2010 object (e.g., an occupant in a multi-user chat room) belonging to the entity associated with an XMPP localpart at a local domain. When an XMPP address does not include a resourcepart (i.e., when it is of the form <domainpart> or <localpart@domainpart>), it is referred to as a BARE JID. When an XMPP address includes a resourcepart (i.e., when it is of the form <domain/resource> or <localpart@domain/resource>), is referred to as a FULL JID. A resourcepart MUST NOT be zero bytes in length and MUST NOT be more than 1023 bytes in length. A resourcepart MUST be formatted such that the Resourceprep profile of [STRINGPREP] can be applied without failing (see Appendix B). Before comparing two resourceparts, an application MUST first ensure that the Resourceprep profile has been applied to each identifier (the profile need not be applied each time a comparison is made, as long as it has been applied before comparison). Note: For historical reasons, the term "resource identifier" is often used in XMPP to refer to the optional portion of an XMPP address that follows the domainpart and the "/" separator character; to help prevent confusion between an XMPP "resource identifier" and the meanings of "resource" and "identifier" provided in Section 1.1 of [URI], this specification uses the term "resourcepart" instead of "resource identifier" (as in RFC 3920). XMPP entities SHOULD consider resourceparts to be opaque strings and SHOULD NOT impute meaning to any given resourcepart. In particular: o Use of the '/' character as a separator between the domainpart and the resourcepart does not imply that XMPP addresses are hierarchical in the way that, say, HTTP addresses are hierarchical; thus for example an XMPP address of the form <localpart@domain/foo/bar> does not identify a resource "bar" that exists below a resource "foo" in a hierarchy of resources associated with the entity "localpart@domain". o The '@' character is allowed in the resourcepart, and is often used in the "nick" shown in XMPP chatrooms. For example, the JID <room@chat.example.com/user@host> describes an entity who is an occupant of the room <room@chat.example.com> with an (asserted) nick of <user@host>. However, chatroom services do not necessarily check such an asserted nick against the occupant's real JID. Saint-Andre Expires January 27, 2011 [Page 7]
Internet-Draft XMPP Address Format July 2010 3. Internationalization Considerations XMPP servers MUST, and XMPP clients SHOULD, support [IDNA2003] for domainparts (including the [NAMEPREP] profile of [STRINGPREP]), the Nodeprep (Appendix A) profile of [STRINGPREP] for localparts, and the Resourceprep (Appendix B) profile of [STRINGPREP] for resourceparts; this enables XMPP addresses to include a wide variety of characters outside the US-ASCII range. Rules for enforcement of the XMPP address format are provided in [XMPP]. 4. Security Considerations 4.1. Reuse of Stringprep The security considerations described in [STRINGPREP] apply to the Nodeprep (Appendix A) and Resourceprep (Appendix B) profiles defined in this document for XMPP localparts and resourceparts. The security considerations described in [STRINGPREP] and [NAMEPREP] apply to the Nameprep profile that is re-used here for XMPP domainparts. 4.2. Reuse of Unicode The security considerations described in [UNICODE-SEC] apply to the use of Unicode characters in XMPP addresses. 4.3. Confusable Characters The Unicode and ISO/IEC 10646 repertoires have many characters that look similar (so-called "confusable characters"). In many cases, users of security protocols might perform visual matching, such as when comparing the names of trusted third parties. Because it is impossible to map similar-looking characters without a great deal of context (such as knowing the fonts used), stringprep does nothing to map similar-looking characters together, nor to prohibit some characters because they look like others. Some specific suggestions about identification and handling of confusable characters appear in the Unicode Security Considerations [UNICODE-SEC]. A localpart can be employed as one part of an entity's address in XMPP. One common usage is as the username of an instant messaging user; another is as the name of a multi-user chat room; and many other kinds of entities could use localparts as part of their addresses. The security of such services could be compromised based on different interpretations of the internationalized localpart; for example, a user entering a single internationalized localpart could access another user's account information, or a user could gain access to a hidden or otherwise restricted chat room or service. Saint-Andre Expires January 27, 2011 [Page 8]
Internet-Draft XMPP Address Format July 2010 A resourcepart can be employed as one part of an entity's address in XMPP. One common usage is as the name for an instant messaging user's connected resource; another is as the nickname of a user in a multi-user chat room; and many other kinds of entities could use resourceparts as part of their addresses. The security of such services could be compromised based on different interpretations of the internationalized resourcepart; for example, a user could attempt to initiate multiple connections with the same name, or a user could send a message to someone other than the intended recipient in a multi-user chat room. 4.4. Address Spoofing There are two forms of address spoofing: forging and mimicking. 4.4.1. Address Forging In the context of XMPP technologies, address forging occurs when an entity is able to generate an XML stanza whose 'from' address does not correspond to the account credentials with which the entity authenticated onto the network (or an authorization identity provided during SASL negotiation). For example, address forging occurs if an entity that authenticated as "juliet@im.example.com" is able to send XML stanzas from "nurse@im.example.com" or "romeo@example.net". Address forging is difficult in XMPP systems, given the requirement for sending servers to stamp 'from' addresses and for receiving servers to verify sending domains via server-to-server authentication (see [XMPP]). However, address forging is not impossible, since a rogue server could forge JIDs at the sending domain by ignoring the stamping requirement. Therefore, an entity outside the security perimeter of a particular server cannot reliably distinguish between bare JIDs of the form <localpart@domainpart> at that server and thus can authenticate only the domainpart of such JIDs with any level of assurance. This specification does not define methods for discovering or counteracting such rogue servers. Furthermore, it is possible for an attacker to forge JIDs at other domains by means of a DNS poisoning attack if DNS security extensions [DNSSEC] are not used. 4.4.2. Address Mimicking Address mimicking occurs when an entity provides legitimate authentication credentials for and sends XML stanzas from an account whose JID appears to a human user to be the same as another JID. For example, in some XMPP clients the address "paypa1@example.org" (spelled with the number one as the final character of the localpart) Saint-Andre Expires January 27, 2011 [Page 9]
Internet-Draft XMPP Address Format July 2010 might appear to be the same as "paypal@example.org (spelled with the lower-case version of the letter "L"), especially on casual visual inspection; this phenomenon is sometimes called "typejacking". A more sophisticated example of address mimicking might involve the use of characters from outside the US-ASCII range, such as the Cherokee characters U+13DA U+13A2 U+13B5 U+13AC U+13A2 U+13AC U+13D2 instead of the US-ASCII characters "STPETER". In some examples of address mimicking, it is unlikely that the average user could tell the difference between the real JID and the fake JID. (Indeed, there is no way to distinguish with full certainty which is the fake JID and which is the real JID; in some communication contexts, the JID with Cherokee characters might be the real JID and the JID with US-ASCII characters might thus appear to be the fake JID.) Because JIDs can contain almost any Unicode character, it can be relatively easy to mimic some JIDs in XMPP systems. The possibility of address mimicking introduces security vulnerabilities of the kind that have also plagued the World Wide Web, specifically the phenomenon known as phishing. As noted in [IDNA-DEFS], "there are no comprehensive technical solutions to the problems of confusable characters". Mimicked JIDs that involve characters from only one character set or from the character set typically employed by a particular user are not easy to combat (e.g., the simple typejacking attack previously described, which relies on a surface similarity between the characters "1" and "l" in some presentations). However, mimicked addresses that involve characters from more than one character set, or from a character set not typically employed by a particular user, can be mitigated somewhat through intelligent presentation. In particular, every human user of an XMPP technology presumably has a preferred language (or, in some cases, a small set of preferred languages), which an XMPP application SHOULD gather either explicitly from the user or implicitly via the operating system of the user's device. Furthermore, every language has a range (or a small set of ranges) of characters normally used to represent that language in textual form. Therefore, an XMPP application SHOULD warn the user when presenting a JID that mixes characters from more than one character set or that uses characters outside the normal range of the user's preferred language(s). This recommendation is not intended to discourage communication across language communities; instead, it recognizes the existence of such language communities and encourages due caution when presenting unfamiliar character sets to human users. 5. IANA Considerations The following sections update the registrations provided in Saint-Andre Expires January 27, 2011 [Page 10]
Internet-Draft XMPP Address Format July 2010 [RFC3920]. 5.1. Nodeprep Profile of Stringprep The Nodeprep profile of stringprep is defined under Nodeprep (Appendix A). The IANA has registered Nodeprep in the stringprep profile registry. Name of this profile: Nodeprep RFC in which the profile is defined: XXXX Indicator whether or not this is the newest version of the profile: This is the first version of Nodeprep 5.2. Resourceprep Profile of Stringprep The Resourceprep profile of stringprep is defined under Resourceprep (Appendix B). The IANA has registered Resourceprep in the stringprep profile registry. Name of this profile: Resourceprep RFC in which the profile is defined: XXXX Indicator whether or not this is the newest version of the profile: This is the first version of Resourceprep 6. Conformance Requirements This section describes a protocol feature set that summarizes the conformance requirements of this specification. This feature set is appropriate for use in software certification, interoperability testing, and implementation reports. For each feature, this section provides the following information: Saint-Andre Expires January 27, 2011 [Page 11]
Internet-Draft XMPP Address Format July 2010 o A human-readable name o An informational description o A reference to the particular section of this document that normatively defines the feature o Whether the feature applies to the Client role, the Server role, or both (where "N/A" signifies that the feature is not applicable to the specified role) o Whether the feature MUST or SHOULD be implemented, where the capitalized terms are to be understood as described in [KEYWORDS] The feature set specified here attempts to adhere to the concepts and formats proposed by Larry Masinter within the IETF's NEWTRK Working Group in 2005, as captured in [INTEROP]. Although this feature set is more detailed than called for by [REPORTS], it provides a suitable basis for the generation of implementation reports to be submitted in support of advancing this specification from Proposed Standard to Draft Standard in accordance with [PROCESS]. Feature: address-domain-length Description: Ensure that the domainpart of an XMPP address is at least one byte in length and at most 1023 bytes in length. Section: Section 2.2 Roles: Both MUST. Feature: address-domain-prep Description: Ensure that the domainpart of an XMPP address conforms to the Nameprep profile of Stringprep. Section: Section 2.2 Roles: Client SHOULD, Server MUST. Feature: address-localpart-length Description: Ensure that the localpart of an XMPP address is at least one byte in length and at most 1023 bytes in length. Section: Section 2.3 Roles: Both MUST. Feature: address-localpart-prep Description: Ensure that the localpart of an XMPP address conforms to the Nodeprep profile of Stringprep. Section: Section 2.3 Saint-Andre Expires January 27, 2011 [Page 12]
Internet-Draft XMPP Address Format July 2010 Roles: Client SHOULD, Server MUST. Feature: address-resource-length Description: Ensure that the resourcepart of an XMPP address is at least one byte in length and at most 1023 bytes in length. Section: Section 2.4 Roles: Both MUST. Feature: address-resource-prep Description: Ensure that the resourcepart of an XMPP address conforms to the Resourceprep profile of Stringprep. Section: Section 2.2 Roles: Client SHOULD, Server MUST. 7. References 7.1. Normative References [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [IDNA2003] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003. [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [NAMEPREP] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)", RFC 3491, March 2003. [STRINGPREP] Hoffman, P. and M. Blanchet, "Preparation of Internationalized Strings ("stringprep")", RFC 3454, December 2002. [UNICODE] The Unicode Consortium, "The Unicode Standard, Version 3.2.0", 2000. The Unicode Standard, Version 3.2.0 is defined by The Unicode Standard, Version 3.0 (Reading, MA, Addison- Wesley, 2000. ISBN 0-201-61633-5), as amended by the Unicode Standard Annex #27: Unicode 3.1 Saint-Andre Expires January 27, 2011 [Page 13]
Internet-Draft XMPP Address Format July 2010 (http://www.unicode.org/reports/tr27/) and by the Unicode Standard Annex #28: Unicode 3.2 (http://www.unicode.org/reports/tr28/). [UNICODE-SEC] The Unicode Consortium, "Unicode Technical Report #36: Unicode Security Considerations", 2008. [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [XMPP] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", draft-ietf-xmpp-3920bis-10 (work in progress), July 2010. 7.2. Informative References [DNS] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [DNSSEC] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, March 2005. [IDNA-DEFS] Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", draft-ietf-idnabis-defs-13 (work in progress), January 2010. [IDNA-PROTO] Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", draft-ietf-idnabis-protocol-18 (work in progress), January 2010. [INTEROP] Masinter, L., "Formalizing IETF Interoperability Reporting", draft-ietf-newtrk-interop-reports-00 (work in progress), October 2005. [IRI] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005. [PROCESS] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [PUNYCODE] Costello, A., "Punycode: A Bootstring encoding of Unicode Saint-Andre Expires January 27, 2011 [Page 14]
Internet-Draft XMPP Address Format July 2010 for Internationalized Domain Names in Applications (IDNA)", RFC 3492, March 2003. [REPORTS] Dusseault, L. and R. Sparks, "Guidance on Interoperation and Implementation Reports for Advancement to Draft Standard", BCP 9, RFC 5657, September 2009. [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 3920, October 2004. [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [XEP-0029] Kaes, C., "Definition of Jabber Identifiers (JIDs)", XSF XEP 0029, October 2003. [XEP-0030] Hildebrand, J., Millard, P., Eatmon, R., and P. Saint- Andre, "Service Discovery", XSF XEP 0030, June 2008. [XEP-0045] Saint-Andre, P., "Multi-User Chat", XSF XEP 0045, January in progress, last updated 2010. [XEP-0060] Millard, P., Saint-Andre, P., and R. Meijer, "Publish- Subscribe", XSF XEP 0060, September 2008. [XML] Paoli, J., Maler, E., Sperberg-McQueen, C., Yergeau, F., and T. Bray, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", World Wide Web Consortium Recommendation REC- xml-20060816, August 2006, <http://www.w3.org/TR/2006/REC-xml-20060816>. [XMPP-URI] Saint-Andre, P., "Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP)", RFC 5122, February 2008. Appendix A. Nodeprep Saint-Andre Expires January 27, 2011 [Page 15]
Internet-Draft XMPP Address Format July 2010 A.1. Introduction This appendix defines the "Nodeprep" profile of stringprep. As such, it specifies processing rules that will enable users to enter internationalized localparts in the Extensible Messaging and Presence Protocol (XMPP) and have the highest chance of getting the content of the strings correct. (An XMPP localpart is the optional portion of an XMPP address that precedes an XMPP domainpart and the '@' separator; it is often but not exclusively associated with an instant messaging username.) These processing rules are intended only for XMPP localparts and are not intended for arbitrary text or any other aspect of an XMPP address. This profile defines the following, as required by [STRINGPREP]: o The intended applicability of the profile: internationalized localparts within XMPP o The character repertoire that is the input and output to stringprep: Unicode 3.2, specified in Section 2 of this Appendix o The mappings used: specified in Section 3 o The Unicode normalization used: specified in Section 4 o The characters that are prohibited as output: specified in Section 5 o Bidirectional character handling: specified in Section 6 A.2. Character Repertoire This profile uses Unicode 3.2 with the list of unassigned code points being Table A.1, both defined in Appendix A of [STRINGPREP]. A.3. Mapping This profile specifies mapping using the following tables from [STRINGPREP]: Table B.1 Table B.2 A.4. Normalization This profile specifies the use of Unicode normalization form KC, as described in [STRINGPREP]. A.5. Prohibited Output This profile specifies the prohibition of using the following tables from [STRINGPREP]. Saint-Andre Expires January 27, 2011 [Page 16]
Internet-Draft XMPP Address Format July 2010 Table C.1.1 Table C.1.2 Table C.2.1 Table C.2.2 Table C.3 Table C.4 Table C.5 Table C.6 Table C.7 Table C.8 Table C.9 In addition, the following additional Unicode characters are also prohibited: U+0022 (QUOTATION MARK), i.e., " U+0026 (AMPERSAND), i.e., & U+0027 (APOSTROPHE), i.e., ' U+002F (SOLIDUS), i.e., / U+003A (COLON), i.e., : U+003C (LESS-THAN SIGN), i.e., < U+003E (GREATER-THAN SIGN), i.e., > U+0040 (COMMERCIAL AT), i.e., @ A.6. Bidirectional Characters This profile specifies checking bidirectional strings, as described in Section 6 of [STRINGPREP]. A.7. Notes Because the additional characters prohibited by Nodeprep are prohibited after normalization, an implementation MUST NOT enable a human user to input any Unicode code point whose decomposition includes those characters; such code points include but are not necessarily limited to the following (refer to [UNICODE] for complete information). o U+2100 (ACCOUNT OF) o U+2101 (ADDRESSED TO THE SUBJECT) o U+2105 (CARE OF) o U+2106 (CADA UNA) o U+226E (NOT LESS-THAN) o U+226F (NOT GREATER-THAN) o U+2A74 (DOUBLE COLON EQUAL) o U+FE13 (SMALL COLON) Saint-Andre Expires January 27, 2011 [Page 17]
Internet-Draft XMPP Address Format July 2010 o U+FE60 (SMALL AMPERSAND) o U+FE64 (SMALL LESS-THAN SIGN) o U+FE65 (SMALL GREATER-THAN SIGN) o U+FE6B (SMALL COMMERCIAL AT) o U+FF02 (FULLWIDTH QUOTATION MARK) o U+FF06 (FULLWIDTH AMPERSAND) o U+FF07 (FULLWIDTH APOSTROPHE) o U+FF0F (FULLWIDTH SOLIDUS) o U+FF1A (FULLWIDTH COLON) o U+FF1C (FULLWIDTH LESS-THAN SIGN) o U+FF1E (FULLWIDTH GREATER-THAN SIGN) o U+FF20 (FULLWIDTH COMMERCIAL AT) Appendix B. Resourceprep B.1. Introduction This appendix defines the "Resourceprep" profile of stringprep. As such, it specifies processing rules that will enable users to enter internationalized resourceparts in the Extensible Messaging and Presence Protocol (XMPP) and have the highest chance of getting the content of the strings correct. (An XMPP resourcepart is the optional portion of an XMPP address that follows an XMPP domainpart and the '/' separator.) These processing rules are intended only for XMPP resourceparts and are not intended for arbitrary text or any other aspect of an XMPP address. This profile defines the following, as required by [STRINGPREP]: o The intended applicability of the profile: internationalized resourceparts within XMPP o The character repertoire that is the input and output to stringprep: Unicode 3.2, specified in Section 2 of this Appendix o The mappings used: specified in Section 3 o The Unicode normalization used: specified in Section 4 o The characters that are prohibited as output: specified in Section 5 o Bidirectional character handling: specified in Section 6 B.2. Character Repertoire This profile uses Unicode 3.2 with the list of unassigned code points being Table A.1, both defined in Appendix A of [STRINGPREP]. Saint-Andre Expires January 27, 2011 [Page 18]
Internet-Draft XMPP Address Format July 2010 B.3. Mapping This profile specifies mapping using the following tables from [STRINGPREP]: Table B.1 B.4. Normalization This profile specifies the use of Unicode normalization form KC, as described in [STRINGPREP]. B.5. Prohibited Output This profile specifies the prohibition of using the following tables from [STRINGPREP]. Table C.1.2 Table C.2.1 Table C.2.2 Table C.3 Table C.4 Table C.5 Table C.6 Table C.7 Table C.8 Table C.9 B.6. Bidirectional Characters This profile specifies checking bidirectional strings, as described in Section 6 of [STRINGPREP]. Appendix C. Differences From RFC 3920 Based on consensus derived from implementation and deployment experience as well as formal interoperability testing, the following substantive modifications were made from RFC 3920. o Corrected the ABNF syntax to (1) ensure consistency with [URI] and [IRI], and (2) prevent zero-length localparts, domainparts, and resourceparts. o To avoid confusion with the term "node" as used in [XEP-0030] and [XEP-0060], changed the term "node identifier" to "localpart" (but retained the name "Nodeprep" for backward compatibility). Saint-Andre Expires January 27, 2011 [Page 19]
Internet-Draft XMPP Address Format July 2010 o To avoid confusion with the terms "resource" and "identifier" as used in [URI], changed the term "resource identifier" to "resourcepart". o Corrected the nameprep processing rules to require use of the UseSTD3ASCIIRules flag. Appendix D. Copying Conditions Regarding this entire document or any portion of it, the author makes no guarantees and is not responsible for any damage resulting from its use. The author grants irrevocable permission to anyone to use, modify, and distribute it in any way that does not diminish the rights of anyone else to use, modify, and distribute it, provided that redistributed derivative works do not contain misleading author or version information. Derivative works need not be licensed under similar terms. Author's Address Peter Saint-Andre Cisco 1899 Wyknoop Street, Suite 600 Denver, CO 80202 USA Phone: +1-303-308-3282 Email: psaintan@cisco.com Saint-Andre Expires January 27, 2011 [Page 20]
