Internet DRAFT - draft-saintandre-precis-nickname
draft-saintandre-precis-nickname
PRECIS P. Saint-Andre
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track March 5, 2012
Expires: September 6, 2012
Preparation and Comparison of Nicknames
draft-saintandre-precis-nickname-00
Abstract
This document describes how to prepare and compare Unicode strings
representing nicknames, primarily as used within textual chatrooms.
This profile is intended to be used by chatroom technologies based on
both the Extensible Messaging and Presence Protocol (XMPP) and the
Message Session Relay Protocol (MSRP).
Status of this Memo
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This Internet-Draft will expire on September 6, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
3.1. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 4
3.3. Visually Similar Characters . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
1.1. Overview
Technologies for textual chatrooms customarily enable participants to
specify a nickname for use in the room; e.g., this is true of
Internet Relay Chat [RFC2811], Multi-User Chat (MUC) based on the
Extensible Messaging and Presence Protocol (XMPP) [XEP-0045], and
multi-party chat based on the Message Session Relay Protocol (MSRP)
[I-D.ietf-simple-chat]. Recent chatroom technologies also allow
internationalized nicknames because they support characters from the
outside the ASCII range, typically by means of the Unicode character
set [UNICODE]. Although such nicknames are often used primarily for
display purposes, they are sometimes used for programmatic purposes
as well (e.g., kicking users or avoiding nickname conflicts).
To increase the likelihood that nickname input and comparison will
work in ways that make sense for typical users throughout the world,
this document defines rules for preparing and comparing
internationalized nicknames.
1.2. Terminology
Many important terms used in this document are defined in
[I-D.ietf-precis-framework], [RFC6365], and [UNICODE]. Relevant XMPP
terms are defined in [RFC6120] and [XEP-0045], and relevant MSRP
terms in [RFC4975] and [I-D.ietf-simple-chat].
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 RFC
2119 [RFC2119].
2. Rules
A nickname MUST NOT be zero bytes in length and MUST NOT be more than
1023 bytes in length (the latter restriction is derived from the
length restriction on XMPP resourceparts, see [RFC6122]). This rule
is to be enforced after any mapping or normalization of code points.
A nickname MUST consist only of Unicode code points that conform to
the "FreeClass" base string class defined in
[I-D.ietf-precis-framework].
For preparation purposes (e.g., when a chatroom client generates a
nickname from user input for inclusion as a nickname protocol
element), an application MUST only ensure that the string conforms to
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the "FreeClass" base string class defined in
[I-D.ietf-precis-framework]; however, it MAY also perform the mapping
and normalization operations specified below for comparison.
For comparison purposes (e.g., when a chatroom server determines if
two nicknames match during the authorization process), an application
MUST treat a nickname as follows, where the operations specified MUST
be completed in the order shown:
1. Non-ASCII space characters from the "N" category defined under
Section 6.14 of [I-D.ietf-precis-framework] MUST be mapped to
SPACE [U+0020].
2. Uppercase and titlecase characters MUST be mapped to their
lowercase equivalents. In applications that prohibit matching
nicknames, this rule helps to reduce the possibility of confusion
by ensuring that nicknames differing only by case (e.g.,
"stpeter" vs. "StPeter") would not be allowed in a room at the
same time.
3. All characters MUST be mapped using Unicode Normalization Form KC
(NFKC). Because NFKC is more "aggressive" in finding matches
than other normalization forms (in the language of Unicode, it
performs both canonical and compatibility decomposition before
recomposing code points), this rule helps to reduce the
possibility of confusion by increasing the number of characters
that would match (e.g., ROMAN NUMERAL FOUR [U+2163] would match
the combination of LATIN CAPITAL LETTER I [U+0049] and LATIN
CAPITAL LETTER V [U+0056]).
For both preparation and comparision, the "Bidi Rule" provided in
[RFC5893] applies to the directionality of a nickname.
3. Security Considerations
3.1. Reuse of PRECIS
The security considerations described in [I-D.ietf-precis-framework]
apply to the "FreeClass" base string class used in this document for
nicknames, respectively.
3.2. Reuse of Unicode
The security considerations described in [UTR39] apply to the use of
Unicode characters in nicknames.
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3.3. Visually Similar Characters
[I-D.ietf-precis-framework] describes some of the security
considerations related to visually similar characters, also called
"confusable characters" or "confusables".
Although the mapping rules under Section 2 are designed in part to
reduce the possibility of confusion about nicknames, this document
does not yet provide more detailed recommendations regarding the
handling of visually similar characters, such as those in [UTR39].
However, a future version of this document might provide such
recommendations.
4. IANA Considerations
The IANA shall add an entry to the PRECIS Usage Registry for reuse of
the PRECIS FreeClass for preparation and comparision of nicknames, as
follows:
Application Protocol: MSRP and XMPP.
Base Class: FreeClass
Subclassing: No.
Directionality: The "Bidi Rule" defined in RFC 5893 applies.
Casemapping: None.
Normalization: NFC.
Specification: RFC XXXX.
5. References
5.1. Normative References
[I-D.ietf-precis-framework]
Blanchet, M. and P. Saint-Andre, "Precis Framework:
Handling Internationalized Strings in Protocols",
draft-ietf-precis-framework-01 (work in progress),
October 2011.
[I-D.ietf-simple-chat]
Niemi, A., Garcia, M., and G. Sandbakken, "Multi-party
Chat Using the Message Session Relay Protocol (MSRP)",
draft-ietf-simple-chat-14 (work in progress), March 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5893] Alvestrand, H. and C. Karp, "Right-to-Left Scripts for
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Internationalized Domain Names for Applications (IDNA)",
RFC 5893, August 2010.
[RFC6122] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Address Format", RFC 6122, March 2011.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
6.1", 2012,
<http://www.unicode.org/versions/Unicode6.1.0/>.
[UTR39] The Unicode Consortium, "Unicode Technical Report #39:
Unicode Security Mechanisms", August 2010,
<http://unicode.org/reports/tr39/>.
[XEP-0045]
Saint-Andre, P., "Multi-User Chat", XSF XEP 0045,
February 2012.
5.2. Informative References
[RFC2811] Kalt, C., "Internet Relay Chat: Channel Management",
RFC 2811, April 2000.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
Session Relay Protocol (MSRP)", RFC 4975, September 2007.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
September 2011.
Author's Address
Peter Saint-Andre
Cisco Systems, Inc.
1899 Wynkoop Street, Suite 600
Denver, CO 80202
USA
Phone: +1-303-308-3282
Email: psaintan@cisco.com
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