draft-ietf-precis-7613bis-05.txt   draft-ietf-precis-7613bis-06.txt 
Network Working Group P. Saint-Andre Network Working Group P. Saint-Andre
Internet-Draft Filament Internet-Draft Filament
Obsoletes: 7613 (if approved) A. Melnikov Obsoletes: 7613 (if approved) A. Melnikov
Intended status: Standards Track Isode Ltd Intended status: Standards Track Isode Ltd
Expires: August 16, 2017 February 12, 2017 Expires: September 28, 2017 March 27, 2017
Preparation, Enforcement, and Comparison of Internationalized Strings Preparation, Enforcement, and Comparison of Internationalized Strings
Representing Usernames and Passwords Representing Usernames and Passwords
draft-ietf-precis-7613bis-05 draft-ietf-precis-7613bis-06
Abstract Abstract
This document describes updated methods for handling Unicode strings This document describes updated methods for handling Unicode strings
representing usernames and passwords. The previous approach was representing usernames and passwords. The previous approach was
known as SASLprep (RFC 4013) and was based on stringprep (RFC 3454). known as SASLprep (RFC 4013) and was based on stringprep (RFC 3454).
The methods specified in this document provide a more sustainable The methods specified in this document provide a more sustainable
approach to the handling of internationalized usernames and approach to the handling of internationalized usernames and
passwords. The preparation, enforcement, and comparison of passwords. The preparation, enforcement, and comparison of
internationalized strings (PRECIS) framework, RFC 7564, obsoletes RFC internationalized strings (PRECIS) framework, RFC 7564, obsoletes RFC
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on August 16, 2017. This Internet-Draft will expire on September 28, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Usernames . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Usernames . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Case Mapping vs. Case Preservation . . . . . . . . . . . 6 3.2. Case Mapping vs. Case Preservation . . . . . . . . . . . 6
3.3. UsernameCaseMapped Profile . . . . . . . . . . . . . . . 7 3.3. UsernameCaseMapped Profile . . . . . . . . . . . . . . . 7
3.3.1. Rules . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3.1. Rules . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3.2. Preparation . . . . . . . . . . . . . . . . . . . . . 8 3.3.2. Preparation . . . . . . . . . . . . . . . . . . . . . 8
3.3.3. Enforcement . . . . . . . . . . . . . . . . . . . . . 8 3.3.3. Enforcement . . . . . . . . . . . . . . . . . . . . . 8
3.3.4. Comparison . . . . . . . . . . . . . . . . . . . . . 8 3.3.4. Comparison . . . . . . . . . . . . . . . . . . . . . 8
3.4. UsernameCasePreserved Profile . . . . . . . . . . . . . . 8 3.4. UsernameCasePreserved Profile . . . . . . . . . . . . . . 9
3.4.1. Rules . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4.1. Rules . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4.2. Preparation . . . . . . . . . . . . . . . . . . . . . 9 3.4.2. Preparation . . . . . . . . . . . . . . . . . . . . . 9
3.4.3. Enforcement . . . . . . . . . . . . . . . . . . . . . 9 3.4.3. Enforcement . . . . . . . . . . . . . . . . . . . . . 9
3.4.4. Comparison . . . . . . . . . . . . . . . . . . . . . 10 3.4.4. Comparison . . . . . . . . . . . . . . . . . . . . . 10
3.5. Application-Layer Constructs . . . . . . . . . . . . . . 10 3.5. Application-Layer Constructs . . . . . . . . . . . . . . 10
3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10 3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10
4. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. OpaqueString Profile . . . . . . . . . . . . . . . . . . 13 4.2. OpaqueString Profile . . . . . . . . . . . . . . . . . . 13
4.2.1. Preparation . . . . . . . . . . . . . . . . . . . . . 13 4.2.1. Preparation . . . . . . . . . . . . . . . . . . . . . 13
4.2.2. Enforcement . . . . . . . . . . . . . . . . . . . . . 14 4.2.2. Enforcement . . . . . . . . . . . . . . . . . . . . . 14
4.2.3. Comparison . . . . . . . . . . . . . . . . . . . . . 14 4.2.3. Comparison . . . . . . . . . . . . . . . . . . . . . 14
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 15 4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 15
5. Use in Application Protocols . . . . . . . . . . . . . . . . 15 5. Use in Application Protocols . . . . . . . . . . . . . . . . 15
6. Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. Usernames . . . . . . . . . . . . . . . . . . . . . . . . 16 6.1. Usernames . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2. Passwords . . . . . . . . . . . . . . . . . . . . . . . . 17 6.2. Passwords . . . . . . . . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7.1. UsernameCaseMapped Profile . . . . . . . . . . . . . . . 18 7.1. UsernameCaseMapped Profile . . . . . . . . . . . . . . . 19
7.2. UsernameCasePreserved Profile . . . . . . . . . . . . . . 19 7.2. UsernameCasePreserved Profile . . . . . . . . . . . . . . 19
7.3. OpaqueString Profile . . . . . . . . . . . . . . . . . . 20 7.3. OpaqueString Profile . . . . . . . . . . . . . . . . . . 20
7.4. Stringprep Profile . . . . . . . . . . . . . . . . . . . 20 7.4. Stringprep Profile . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8.1. Password/Passphrase Strength . . . . . . . . . . . . . . 20 8.1. Password/Passphrase Strength . . . . . . . . . . . . . . 21
8.2. Identifier Comparison . . . . . . . . . . . . . . . . . . 21 8.2. Identifier Comparison . . . . . . . . . . . . . . . . . . 21
8.3. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 21 8.3. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 21
8.4. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . 21 8.4. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . 21
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.1. Normative References . . . . . . . . . . . . . . . . . . 21 9.1. Normative References . . . . . . . . . . . . . . . . . . 21
9.2. Informative References . . . . . . . . . . . . . . . . . 22 9.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Changes from RFC 7613 . . . . . . . . . . . . . . . 24 Appendix A. Changes from RFC 7613 . . . . . . . . . . . . . . . 24
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 24 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
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application protocols that use SASLprep. If the community that uses application protocols that use SASLprep. If the community that uses
such an application protocol wishes to modernize its handling of such an application protocol wishes to modernize its handling of
internationalized strings to use PRECIS instead of stringprep, it internationalized strings to use PRECIS instead of stringprep, it
needs to explicitly update the existing application protocol needs to explicitly update the existing application protocol
definition (one example is [RFC7622]. Non-coordinated updates to definition (one example is [RFC7622]. Non-coordinated updates to
protocol implementations are discouraged because they can have a protocol implementations are discouraged because they can have a
negative impact on interoperability and security. negative impact on interoperability and security.
2. Terminology 2. Terminology
Many important terms used in this document are defined in [RFC5890], A "username" or "user identifier" is a string of characters
[RFC6365], [RFC7564], and [Unicode]. The term "non-ASCII space" designating an account on a computing device or system, often but not
refers to any Unicode code point having a Unicode general category of necessarily for use by a person. Although some devices and system
"Zs", with the exception of U+0020 (here called "ASCII space"). might allow a username to be part or all of a person's name, and a
person might want their account designator to be part or all of their
name, because of the complexities involved that outcome is not
guaranteed for all human names on all computing devices or systems
that follow the rules defined in this specification. Protocol
designers and application developers who wish to allow a wider range
of characters are encouraged to consider a separation between more
restrictive account identifiers and more expressive display names.
As used here, the term "password" is not literally limited to a word; A "password" is a string of characters that allows access to a
i.e., a password could be a passphrase consisting of more than one computing device or system, often associated with a particular
word, perhaps separated by spaces, punctuation, or other non- username. A password is not literally limited to a word, because a
alphanumeric characters. password could be a passphrase consisting of more than one word,
perhaps separated by spaces, punctuation, or other non-alphanumeric
characters.
Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify
that the authentication identity used in the context of such that the authentication identity used in the context of such
mechanisms is a "simple user name" (see Section 2 of [RFC4422] as mechanisms is a "simple user name" (see Section 2 of [RFC4422] as
well as [RFC4013]). Various application technologies also assume well as [RFC4013]). Various application technologies also assume
that the identity of a user or account takes the form of a username that the identity of a user or account takes the form of a username
(e.g., authentication for the Hypertext Transfer Protocol as (e.g., authentication for the Hypertext Transfer Protocol as
specified in [RFC7617] and [RFC7616]), whether or not they use SASL. specified in [RFC7617] and [RFC7616]), whether or not they use SASL.
Note well that the exact form of a username in any particular SASL Note well that the exact form of a username in any particular SASL
mechanism or application technology is a matter for implementation mechanism or application technology is a matter for implementation
and deployment, and that a username does not necessarily map to any and deployment, and that a username does not necessarily map to any
particular application identifier. particular application identifier.
Many important terms used in this document are defined in [RFC5890],
[RFC6365], [RFC7564], and [Unicode]. The term "non-ASCII space"
refers to any Unicode code point having a Unicode general category of
"Zs", with the exception of U+0020 (here called "ASCII space").
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
3. Usernames 3. Usernames
3.1. Definition 3.1. Definition
This document specifies that a username is a string of Unicode code This document specifies that a username is a string of Unicode code
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strings (rules regarding minimum or maximum length, further strings (rules regarding minimum or maximum length, further
restrictions on allowable code points or character ranges, safeguards restrictions on allowable code points or character ranges, safeguards
to mitigate the effects of visually similar characters, etc.), to mitigate the effects of visually similar characters, etc.),
application-layer constructs (see Section 3.5), and related matters. application-layer constructs (see Section 3.5), and related matters.
Some PRECIS profile definitions encourage entities that enforce the Some PRECIS profile definitions encourage entities that enforce the
rules to be liberal in what they accept. However, for usernames and rules to be liberal in what they accept. However, for usernames and
passwords such a policy can be problematic, because it can lead to passwords such a policy can be problematic, because it can lead to
false positives. An in-depth discussion can be found in [RFC6943]. false positives. An in-depth discussion can be found in [RFC6943].
Applying the rules for any given PRECIS profile is not necessarily an
idempotent procedure for all code points. Therefore, implementations
might need to apply the rules more than once to an internationalized
string.
6. Migration 6. Migration
The rules defined in this specification differ slightly from those The rules defined in this specification differ slightly from those
defined by the SASLprep specification [RFC4013]. The following defined by the SASLprep specification [RFC4013]. The following
sections describe these differences, along with their implications sections describe these differences, along with their implications
for migration, in more detail. for migration, in more detail.
6.1. Usernames 6.1. Usernames
Deployments that currently use SASLprep for handling usernames might Deployments that currently use SASLprep for handling usernames might
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