Preparation, Enforcement, and Comparison of Internationalized Strings Representing Usernames and Passwords
RFC 8265

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Internet Engineering Task Force (IETF)                    P. Saint-Andre
Request for Comments: 8265                                    Jabber.org
Obsoletes: 7613                                              A. Melnikov
Category: Standards Track                                      Isode Ltd
ISSN: 2070-1721                                             October 2017

 Preparation, Enforcement, and Comparison of Internationalized Strings
                  Representing Usernames and Passwords

Abstract

   This document describes updated methods for handling Unicode strings
   representing usernames and passwords.  The previous approach was
   known as SASLprep (RFC 4013) and was based on Stringprep (RFC 3454).
   The methods specified in this document provide a more sustainable
   approach to the handling of internationalized usernames and
   passwords.  This document obsoletes RFC 7613.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8265.

Copyright Notice

   Copyright (c) 2017 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
   (https://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 & Melnikov       Standards Track                    [Page 1]
RFC 8265             PRECIS: Usernames and Passwords        October 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Usernames . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Definition  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Case Mapping vs. Case Preservation  . . . . . . . . . . .   6
     3.3.  UsernameCaseMapped Profile  . . . . . . . . . . . . . . .   7
       3.3.1.  Rules . . . . . . . . . . . . . . . . . . . . . . . .   7
       3.3.2.  Preparation . . . . . . . . . . . . . . . . . . . . .   8
       3.3.3.  Enforcement . . . . . . . . . . . . . . . . . . . . .   8
       3.3.4.  Comparison  . . . . . . . . . . . . . . . . . . . . .   9
     3.4.  UsernameCasePreserved Profile . . . . . . . . . . . . . .   9
       3.4.1.  Rules . . . . . . . . . . . . . . . . . . . . . . . .   9
       3.4.2.  Preparation . . . . . . . . . . . . . . . . . . . . .   9
       3.4.3.  Enforcement . . . . . . . . . . . . . . . . . . . . .  10
       3.4.4.  Comparison  . . . . . . . . . . . . . . . . . . . . .  10
     3.5.  Application-Layer Constructs  . . . . . . . . . . . . . .  11
     3.6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  11
   4.  Passwords . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     4.1.  Definition  . . . . . . . . . . . . . . . . . . . . . . .  13
     4.2.  OpaqueString Profile  . . . . . . . . . . . . . . . . . .  14
       4.2.1.  Preparation . . . . . . . . . . . . . . . . . . . . .  14
       4.2.2.  Enforcement . . . . . . . . . . . . . . . . . . . . .  14
       4.2.3.  Comparison  . . . . . . . . . . . . . . . . . . . . .  15
     4.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  15
   5.  Use in Application Protocols  . . . . . . . . . . . . . . . .  16
   6.  Migration . . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.1.  Usernames . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.2.  Passwords . . . . . . . . . . . . . . . . . . . . . . . .  19
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  UsernameCaseMapped Profile  . . . . . . . . . . . . . . .  20
     7.2.  UsernameCasePreserved Profile . . . . . . . . . . . . . .  20
     7.3.  OpaqueString Profile  . . . . . . . . . . . . . . . . . .  21
     7.4.  Stringprep Profile  . . . . . . . . . . . . . . . . . . .  22
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
     8.1.  Password/Passphrase Strength  . . . . . . . . . . . . . .  22
     8.2.  Password/Passphrase Comparison  . . . . . . . . . . . . .  22
     8.3.  Identifier Comparison . . . . . . . . . . . . . . . . . .  22