RFC 3491

Network Working Group P. Hoffman Request for Comments: 3491 IMC & VPNC Category: Standards Track M. Blanchet

                                                                Viagenie
                                                              March 2003

                   Nameprep: A Stringprep Profile for
                  Internationalized Domain Names (IDN)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

This document describes how to prepare internationalized domain name (IDN) labels in order to increase the likelihood that name input and name comparison work in ways that make sense for typical users throughout the world. This profile of the stringprep protocol is used as part of a suite of on-the-wire protocols for internationalizing the Domain Name System (DNS).

この文書は、名前の入力と名前の比較が、通常の世界中の利用者に意味のある形で行われる確からしさを増加させるため、どう国際化ドメイン名 (IDN) 名札を準備するかを説明します。この stringprep プロトコルのプロファイルは、ドメイン名システム (DNS) を国際化するために用いるプロトコル一式の一部として使われます。

1. Introduction

   This document specifies processing rules that will allow users to
   enter internationalized domain names (IDNs) into applications and
   have the highest chance of getting the content of the strings
   correct.  It is a profile of stringprep [STRINGPREP].  These
   processing rules are only intended for internationalized domain
   names, not for arbitrary text.

   This profile defines the following, as required by [STRINGPREP].

   -  The intended applicability of the profile: internationalized
      domain names processed by IDNA.

   -  The character repertoire that is the input and output to
      stringprep:  Unicode 3.2, specified in section 2.

   -  The mappings used: specified in section 3.

   -  The Unicode normalization used: specified in section 4.

   -  The characters that are prohibited as output: specified in section
      5.

   -  Bidirectional character handling: specified in section 6.

1.1 Interaction of protocol parts

Nameprep is used by the IDNA [IDNA] protocol for preparing domain names; it is not designed for any other purpose. It is explicitly not designed for processing arbitrary free text and SHOULD NOT be used for that purpose. Nameprep is a profile of Stringprep [STRINGPREP]. Implementations of Nameprep MUST fully implement Stringprep.

Nameprep は、 IDNA プロトコルがドメイン名を準備するために使います。 Nameprep は他の目的は考慮していません。特に、任意の文章を処理する目的で設計してはおらず、そのような目的で使うべきではありません。 Nameprep は Stringprep のプロファイルです。 Nameprep の実装者は Stringprep を完全に実装しなければなりません。

Nameprep is used to process domain name labels, not domain names. IDNA calls nameprep for each label in a domain name, not for the whole domain name.

Nameprep はドメイン名ではなく、ドメイン名札を処理するために使います。 IDNA はドメイン名全体ではなく、ドメイン名中の名札それぞれについて Nameprep を呼びます。

1.2 Terminology

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
   in this document are to be interpreted as described in BCP 14, RFC
   2119 [RFC2119].

2. Character Repertoire

This profile uses Unicode 3.2, as defined in [STRINGPREP] Appendix A.

このプロファイルは、 Stringprep 附属書 A で定義されている通り、 Unicode 3.2 を使います。

3. Mapping

This profile specifies mapping using the following tables from [STRINGPREP]:

このプロファイルは、 Stringprep の次の表を使って写像を指定します。

   Table B.1
   Table B.2

4. Normalization

This profile specifies using Unicode normalization form KC, as described in [STRINGPREP].

このプロファイルは、 Stringprep で説明されている通り、 Unicode 正規化形 KC を使うと指定します。

5. Prohibited Output

This profile specifies prohibiting using the following tables from [STRINGPREP]:

このプロファイルは、 Stringprep の次の表を使って禁止を指定します。

   Table C.1.2
   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

IMPORTANT NOTE: This profile MUST be used with the IDNA protocol. The IDNA protocol has additional prohibitions that are checked outside of this profile.

重要な注意: このプロファイルは IDNA プロトコルと共に使わなければなりません。 IDNA プロファイルにはこのプロファイルの他に更に検査する禁止事項があります。

6. Bidirectional characters

This profile specifies checking bidirectional strings as described in [STRINGPREP] section 6.

このプロファイルは Stringprep 6章に説明されている双方向的文字列の検査を指定します。

7. Unassigned Code Points in Internationalized Domain Names

If the processing in [IDNA] specifies that a list of unassigned code points be used, the system uses table A.1 from [STRINGPREP] as its list of unassigned code points.

IDNA の処理で未割当て符号位置の一覧を使うと指定されている場合、システムは未割当て符号位置の一覧として Stringprep の表 A.1 を使います。

8. References

8.1 Normative References

   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

   [STRINGPREP] Hoffman, P. and M. Blanchet, "Preparation of
                Internationalized Strings ("stringprep")", RFC 3454,
                December 2002.

   [IDNA]       Faltstrom, P., Hoffman, P. and A. Costello,
                "Internationalizing Domain Names in Applications
                (IDNA)", RFC 3490, March 2003.

8.2 Informative references

   [STD13]      Mockapetris, P., "Domain names - concepts and
                facilities", STD 13, RFC 1034, and "Domain names -
                implementation and specification", STD 13, RFC 1035,
                November 1987.

9. Security Considerations

   The Unicode and ISO/IEC 10646 repertoires have many characters that
   look similar.  In many cases, users of security protocols might do
   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.

   Security on the Internet partly relies on the DNS.  Thus, any change
   to the characteristics of the DNS can change the security of much of
   the Internet.

   Domain names are used by users to connect to Internet servers.  The
   security of the Internet would be compromised if a user entering a
   single internationalized name could be connected to different servers
   based on different interpretations of the internationalized domain
   name.

   Current applications might assume that the characters allowed in
   domain names will always be the same as they are in [STD13].  This
   document vastly increases the number of characters available in
   domain names.  Every program that uses "special" characters in
   conjunction with domain names may be vulnerable to attack based on
   the new characters allowed by this specification.

10. IANA Considerations

   This is a profile of stringprep.  It has been registered by the IANA
   in the stringprep profile registry
   (www.iana.org/assignments/stringprep-profiles).

      Name of this profile:
         Nameprep

      RFC in which the profile is defined:
         This document.

      Indicator whether or not this is the newest version of the
      profile:
         This is the first version of Nameprep.

11. Acknowledgements

   Many people from the IETF IDN Working Group and the Unicode Technical
   Committee contributed ideas that went into this document.

   The IDN Nameprep design team made many useful changes to the
   document.  That team and its advisors include:

      Asmus Freytag
      Cathy Wissink
      Francois Yergeau
      James Seng
      Marc Blanchet
      Mark Davis
      Martin Duerst
      Patrik Faltstrom
      Paul Hoffman

   Additional significant improvements were proposed by:

      Jonathan Rosenne
      Kent Karlsson
      Scott Hollenbeck
      Dave Crocker
      Erik Nordmark
      Matitiahu Allouche

12. Authors' Addresses

   Paul Hoffman
   Internet Mail Consortium and VPN Consortium
   127 Segre Place
   Santa Cruz, CA  95060 USA

   EMail: paul.hoffman@imc.org and paul.hoffman@vpnc.org

   Marc Blanchet
   Viagenie inc.
   2875 boul. Laurier, bur. 300
   Ste-Foy, Quebec, Canada, G1V 2M2

   EMail: Marc.Blanchet@viagenie.qc.ca

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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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