One document matched: draft-blanchet-precis-problem-statement-00.txt

Network Working Group                                        M. Blanchet
Internet-Draft                                                  Viagenie
Intended status: Informational                              July 5, 2010
Expires: January 6, 2011


                 Stringprep Revision Problem Statement
             draft-blanchet-precis-problem-statement-00.txt

Abstract

   Using Unicode codepoints in protocol strings requires preparation of
   the string.  Internationalized Domain Names(idn) initial work defined
   and used Stringprep and Nameprep.  Other protocols have defined
   Stringprep profiles.  A new approach different from Stringprep/
   Nameprep is used for a revision of IDN.  The Stringprep profiles need
   to be updated or a replacement of Stringprep need to be designed.
   This document summarizes the findings of the current usage of
   Stringprep and identifies directions for a new Stringprep replacement
   protocol.

Status of this Memo

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  Usage and Issues of Stringprep  . . . . . . . . . . . . . . . . 4
   3.  Considerations for Stringprep replacement . . . . . . . . . . . 5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   6.  Discussion home for this draft  . . . . . . . . . . . . . . . . 6
   7.  Informative References  . . . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7









































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1.  Introduction

   As part of the Internationalized Domain Names(idn) initial work
   [RFC3490][RFC3491][RFC3492], the Unicode-based strings needed to be
   prepared and normalized to enable their use in the DNS with exact
   match mechanism.  The method, called Nameprep [RFC3491], is specific
   to idn, but is generalized as Stringprep [RFC3454], to help other
   protocols with similar needs, but with different constraints than
   idn.

   Strinprep defines a framework where protocols defines their
   Stringprep profiles.  Known IETF specifications using Strinprep are:
   o  The Nameprep profile[RFC3490] for use in Internationalized Domain
      Names (IDNs)
   o  The iSCSI profile [RFC3722] for use in Internet Small Computer
      Systems Interface (iSCSI) Names
   o  The Nodeprep and Resourceprep profiles [RFC3920] for use in the
      Extensible Messaging and Presence Protocol (XMPP)
   o  The Policy MIB profile [RFC4011] for use in the Simple Network
      Management Protocol (SNMP)
   o  The SASLprep profile [RFC4013] for use in the Simple
      Authentication and Security Layer (SASL)
   o  The trace profile [RFC4505] for use with the SASL ANONYMOUS
      mechanism
   o  The LDAP profile [RFC4518] for use with LDAP

   Based on findings [RFC4690] on early deployments of idn, IDNs
   specifications have been updated /* note to add ref to idnabis RFCs*/
   and do not use stringprep/nameprep anymore.  Instead, an algorithm
   based on Unicode properties of codepoints is defined.  That algorithm
   generates a stable and complete table of the supported Unicode
   codepoints.  This algorithm is based on an inclusion-based approach,
   instead of the exclusion-based approach of Stringprep/Nameprep.

   This document lists the shortcomings and issues found by protocols
   listed above that defined Stringprep profiles.  It also lists some
   early conclusions and requirements for a potential replacement of
   Stringprep.


2.  Usage and Issues of Stringprep

   During IETF 77, a BOF discussed the current state of the protocols
   that have defined Stringprep profiles.  The main conclusions are /*
   ref meeting notes */:
   o  Stringprep is bound to a specific version of Unicode: 3.2.
      Stringprep has not been updated to new versions of Unicode.
      Therefore, the protocols using Stringprep are stuck to Unicode



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      3.2.
   o  The protocols need to be updated to support new versions of
      Unicode.  The protocols would like to not be bound to a specific
      version of Unicode, but rather have better Unicode agility as
      IDNAbis.
   o  The protocols require better bidirectional support (bidi) than
      currently offered by Stringprep.
   o  If the protocols are updated to use a new version of Stringprep or
      another framework, then backward compatibility is an important
      requirement.  For example, Stringprep uses NFKC[UAX15], while
      IDNAbis uses NFC[UAX15].
   o  protocols are using each other, for example, a protocol can use
      user identifiers that are later passed to SASL, LDAP or another
      authentication mechanism.  Therefore, common set of rules or
      classes of strings are preferred over specific rules for each
      protocol.

   Stringprep profiles protocols use strings for different purposes:
   o  XMPP uses a different Stringprep profiles for each part of the
      XMPP address (JID): a localpart which is similar to a username and
      used for authentication, a domainpart which is a domain name and a
      resource part which is less restrictive than the localpart.
   o  iSCSI uses a Stringprep profile for the IQN which is essentially a
      domain name.
   o  SASL and LDAP uses a Stringprep profile for usernames.
   o  LDAP uses a set of Stringprep profiles.

   During the newprep BOF, it was the concensus of the attendees that
   the Stringprep profiles protocols would highly prefer to have a
   replacement of Stringprep, with similar characteristics as the
   IDNA2008.  That replacement should be defined so that the protocols
   would not have to "deal" with i18n strings in too much details since
   i18n expertise is not available in the respective protocols or
   working groups.


3.  Considerations for Stringprep replacement

   From the findings about, the following directions are proposed:
   o  A stringprep replacement should be defined.
   o  The replacement should take an approach similar to IDNA2008,
      enabling Unicode agility.
   o  Protocols share similar characteristics of strings.  Therefore,
      defining i18n preparation algorithms for a small set of string
      classes may be sufficient for most cases and provides the
      coherence among a set of protocol friends.





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4.  Security Considerations

   TBD


5.  IANA Considerations

   This document has no actions for IANA.


6.  Discussion home for this draft

   This document is intended to define the problem space discussed in
   the precis@ietf.org mailing list.


7.  Informative References

   [RFC3454]  Hoffman, P. and M. Blanchet, "Preparation of
              Internationalized Strings ("stringprep")", RFC 3454,
              December 2002.

   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC3491]  Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
              Profile for Internationalized Domain Names (IDN)",
              RFC 3491, March 2003.

   [RFC3492]  Costello, A., "Punycode: A Bootstring encoding of Unicode
              for Internationalized Domain Names in Applications
              (IDNA)", RFC 3492, March 2003.

   [RFC3722]  Bakke, M., "String Profile for Internet Small Computer
              Systems Interface (iSCSI) Names", RFC 3722, April 2004.

   [RFC3920]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

   [RFC4011]  Waldbusser, S., Saperia, J., and T. Hongal, "Policy Based
              Management MIB", RFC 4011, March 2005.

   [RFC4013]  Zeilenga, K., "SASLprep: Stringprep Profile for User Names
              and Passwords", RFC 4013, February 2005.

   [RFC4505]  Zeilenga, K., "Anonymous Simple Authentication and
              Security Layer (SASL) Mechanism", RFC 4505, June 2006.



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   [RFC4518]  Zeilenga, K., "Lightweight Directory Access Protocol
              (LDAP): Internationalized String Preparation", RFC 4518,
              June 2006.

   [RFC4690]  Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
              Recommendations for Internationalized Domain Names
              (IDNs)", RFC 4690, September 2006.


Author's Address

   Marc Blanchet
   Viagenie
   2600 boul. Laurier, suite 625
   Quebec, QC  G1V 4W1
   Canada

   Email: Marc.Blanchet@viagenie.ca
   URI:   http://viagenie.ca
































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