WDIFF

draft-ietf-idn-nameprep-11.txt-8047.txt --> rfc3491.txt

Network Working Group P. Hoffman
draft-ietf-idn-nameprep-11.txt
Request for Comments: 3491 IMC & VPNC
June 24, 2002 Marc
Category: Standards Track M. Blanchet
Expires in six months ViaGenie
Viagenie
March 2003

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

Status of this memo Memo

This document is specifies an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of Internet standards track protocol for the
Internet Engineering Task
Force (IETF), its areas, community, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid requests discussion and suggestions for a maximum
improvements. Please refer to the current edition of six months the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and may be updated, replaced, or obsoleted by other documents at any
time. It status of this protocol. Distribution of this memo is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."

To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. unlimited.

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 DNS. Domain Name System (DNS).

1. Introduction

This document specifies processing rules that will allow users to
enter internationalized domain names in (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] [STRINGPREP].

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

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

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RFC 3491 IDN Nameprep March 2003

- The mappings used: specified in section 3 3.

- The Unicode normalization used: specified in section 4 4.

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

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.1. A.

3. Mapping

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

Table B.1
Table B.2

4. Normalization

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

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RFC 3491 IDN Nameprep March 2003

5. Prohibited Output

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

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.

6. Bidirectional characters

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

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.

8. References

8.1 Normative references 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] Patrik Faltstrom, Paul P., Hoffman, P. and Adam M. A. Costello,
"Internationalizing Domain Names in Applications
(IDNA)",
draft-ietf-idn-idna, work-in-progress.

[STRINGPREP] Paul RFC 3490, March 2003.

Hoffman and Marc Blanchet, "Preparation of
Internationalized Strings ("stringprep")", draft-hoffman-stringprep,
work in progress. & Blanchet Standards Track [Page 3]

RFC 3491 IDN Nameprep March 2003

8.2 Informative references

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

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

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RFC 3491 IDN Nameprep March 2003

10. IANA Considerations

This is a profile of stringprep. When it becomes an RFC, it should be It has been registered by the IANA
in the stringprep profile registry. registry
(www.iana.org/assignments/stringprep-profiles).

Name of this profile:
Nameprep

RFC in which the profile is defined:
This document 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 the first draft of this document.

The IDN namprep Nameprep design team made many useful changes to the first
draft.
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

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RFC 3491 IDN Nameprep March 2003

12. Author Contact Information 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

A. Changes from -10 to -11

[[ To be removed when published as an

Hoffman & Blanchet Standards Track [Page 6]

RFC ]]

Change Unicode 3.1 3491 IDN Nameprep March 2003

13. Full Copyright Statement

This document and translations of it may be copied and furnished to Unicode 3.2 in sections 1
others, and 2.

In the list in section 1, add:
- Bidirectional character handling: specified in section 6.

In the list derivative works that comment on or otherwise explain it
or assist in section 5, change to Table C.1.2 its implementation may be prepared, copied, published
and Table C.2.2 distributed, in stringprep to just get whole or in part, without restriction of any
kind, provided that the non-ASCII characters.

Remove section 5.1 above copyright notice and the this paragraph preceding it about the
additional prohibitions.

Add section 6 are
included on all such copies and renumber current sections 6 through 11.

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6. Bidirectional characters

This profile specifies checking bidirectional strings as described derivative works. However, this
document itself may not be modified in [STRINGPREP] section 6.
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Add any way, such as by removing
the copyright notice or references to the text of section 9 with:

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Name Internet Society or other
Internet organizations, except as needed for the purpose of this profile:
Nameprep

RFC
developing Internet standards in which case the profile is defined:
This document

Indicator whether procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not this is the most current version of be
revoked by the
profile: Internet Society or its successors or assigns.

This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the first version of Nameprep.
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Add Matitiahu Allouche to acknowledgements. RFC Editor function is currently provided by the
Internet Society.

Hoffman & Blanchet Standards Track [Page 7]

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