< draft-ietf-precis-saslprepbis-03.txt		draft-ietf-precis-saslprepbis-04.txt >
	PRECIS P. Saint-Andre		PRECIS P. Saint-Andre
	Internet-Draft Cisco Systems, Inc.		Internet-Draft Cisco Systems, Inc.
	Obsoletes: 4013 (if approved) A. Melnikov		Obsoletes: 4013 (if approved) A. Melnikov
	Intended status: Standards Track Isode Ltd		Intended status: Standards Track Isode Ltd
	Expires: January 13, 2014 July 12, 2013		Expires: February 5, 2014 August 4, 2013
	Preparation and Comparison of Internationalized Strings Representing		Preparation and Comparison of Internationalized Strings Representing
	Simple User Names and Passwords		Usernames and Passwords
	draft-ietf-precis-saslprepbis-03		draft-ietf-precis-saslprepbis-04
	Abstract		Abstract
	This document describes how to handle Unicode strings representing		This document describes how to handle Unicode strings representing
	simple user names and passwords, primarily for purposes of		usernames and passwords. This profile is intended to be used by
	comparison. This profile is intended to be used by Simple		protocols that exchange or otherwise make use of usernames and
	Authentication and Security Layer (SASL) mechanisms (such as PLAIN		passwords. This document obsoletes RFC 4013.
	and SCRAM-SHA-1), as well as other protocols that exchange simple
	user names or passwords. This document obsoletes RFC 4013.
	Status of this Memo		Status of this Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
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	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on January 13, 2014.		This Internet-Draft will expire on February 5, 2014.
	Copyright Notice		Copyright Notice
	Copyright (c) 2013 IETF Trust and the persons identified as the		Copyright (c) 2013 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. What the Username and Password Profiles Provide . . . . . . . 3
	1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3		3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Simple User Names . . . . . . . . . . . . . . . . . . . . . . 4		4. Usernames . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4		4.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 5		4.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 5
	3. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 6		5. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 6		5.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 7
	3.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 7		5.2. Preparation . . . . . . . . . . . . . . . . . . . . . . . 7
	4. Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 7		6. Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	4.1. User Names . . . . . . . . . . . . . . . . . . . . . . . . 7		6.1. Usernames . . . . . . . . . . . . . . . . . . . . . . . . 8
	4.2. Passwords . . . . . . . . . . . . . . . . . . . . . . . . 9		6.2. Passwords . . . . . . . . . . . . . . . . . . . . . . . . 9
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 9		7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	5.1. Password/Passphrase Strength . . . . . . . . . . . . . . . 10		7.1. Password/Passphrase Strength . . . . . . . . . . . . . . . 10
	5.2. Identifier Comparison . . . . . . . . . . . . . . . . . . 10		7.2. Identifier Comparison . . . . . . . . . . . . . . . . . . 10
	5.3. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 10		7.3. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 10
	5.4. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 10		7.4. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 11
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	6.1. Use of IdentifierClass . . . . . . . . . . . . . . . . . . 10		8.1. Use of IdentifierClass . . . . . . . . . . . . . . . . . . 11
	6.2. Use of FreeformClass . . . . . . . . . . . . . . . . . . . 11		8.2. Use of FreeformClass . . . . . . . . . . . . . . . . . . . 11
	7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 11		9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11		9.1. Normative References . . . . . . . . . . . . . . . . . . . 12
	8.1. Normative References . . . . . . . . . . . . . . . . . . . 11		9.2. Informative References . . . . . . . . . . . . . . . . . . 12
	8.2. Informative References . . . . . . . . . . . . . . . . . . 12
	Appendix A. Differences from RFC 4013 . . . . . . . . . . . . . . 13		Appendix A. Differences from RFC 4013 . . . . . . . . . . . . . . 13
	Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 13		Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 14
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
	1. Introduction		1. Introduction
	1.1. Overview		Usernames and passwords are widely used for authentication and
			authorization on the Internet, either directly when provided in
			plaintext (as in the SASL PLAIN mechanism [RFC4616] or the HTTP Basic
			scheme [RFC2617]) or indirectly when provided as the input to a
			cryptographic algorithm such as a hash function (as in the SASL SCRAM
			mechanism [RFC5802] or the HTTP Digest scheme [RFC2617]). To
			increase the likelihood that the input and comparison of usernames
			and passwords will work in ways that make sense for typical users
			throughout the world, this document defines rules for preparing and
			comparing internationalized strings that represent usernames and
			passwords.
	User names and passwords are used pervasively in authentication and		The methods specified in this document define a PRECIS profile as
	authorization on the Internet. To increase the likelihood that the		explained in the PRECIS framework specification
	input and comparison of user names and passwords will work in ways		[I-D.ietf-precis-framework]. This document assumes that all strings
	that make sense for typical users throughout the world, this document		are comprised of characters from the Unicode character set [UNICODE],
	defines rules for preparing and comparing internationalized strings		with special attention to characters outside the ASCII range [RFC20].
	that represent simple user names and passwords. (In many		The methods defined here might be applicable wherever usernames or
	authentication technologies passwords are not directly compared		passwords are used. However, the methods are not intended for use in
	because the actual password is used as input to an algorithm such as		preparing strings that are not usernames (e.g., email addresses and
	a hash function; however, non-ASCII code points in the input string		LDAP distinguished names), nor in cases where identifiers or secrets
	still need to be handled correctly.)		are not strings (e.g., keys and certificates) or require specialized
			handling.
	The algorithms defined in this document assume that all strings are		This document obsoletes RFC 4013 (the "SASLprep" profile of
	comprised of characters from the Unicode character set [UNICODE].		stringprep [RFC3454]) but can be used by technologies other than the
			Simple Authentication and Security Layer (SASL) [RFC4422], such as
			HTTP authentication [RFC2617].
	The algorithms are designed for use in Simple Authentication and		2. What the Username and Password Profiles Provide
	Security Layer (SASL) [RFC4422] mechanisms, such as PLAIN [RFC4616]
	and SCRAM-SHA-1 [RFC5802]. However, they might be applicable
	wherever simple user names or passwords are used. This profile is
	not intended for use in preparing strings that are not simple user
	names (e.g., email addresses, DNS domain names, LDAP distinguished
	names), nor in cases where identifiers or secrets are not strings
	(e.g., keys or certificates) or require specialized handling (e.g.,
	case folding).
	This document builds upon the PRECIS framework defined in		Profiles of the PRECIS framework enable software to handle Unicode
	[I-D.ietf-precis-framework], which differs fundamentally from the		characters outside the ASCII range in an automated way, so that such
	stringprep technology [RFC3454] used in SASLprep [RFC4013]. The		characters are treated carefully and consistently in application
	primary difference is that stringprep profiles allowed all characters		protocols. In large measure, these profiles are designed to protect
	except those which were explicitly disallowed, whereas PRECIS		application developers from the potentially negative consequences of
	profiles disallow all characters except those which are explicitly		supporting the full range of Unicode characters. For instance, in
	allowed (this "inclusion model" was originally used for		almost all application protocols it would be dangerous to treat the
	internationalized domain names in [RFC5891]; see [RFC5894] for		Unicode character SUPERSCRIPT ONE (U+0089) as equivalent to DIGIT ONE
	further discussion). It is important to keep this distinction in		(U+0031), since that would result in false positives during
	mind when comparing the technology defined in this document to		comparison, authentication, and authorization (e.g., an attacker
	SASLprep [RFC4013].		could easy spoof an account "user1@example.com").
	This document obsoletes RFC 4013.		Whereas a naive use of Unicode would make such attacks trivially
			easy, the Username PRECIS profile defined in this document generally
			protects applications from inadvertently causing such problems.
			(Similar considerations apply to passwords, although here it is
			desirable to support a wider range of characters so as to maximize
			entropy during authentication.)
	1.2. Terminology		3. Terminology
	Many important terms used in this document are defined in		Many important terms used in this document are defined in
	[I-D.ietf-precis-framework], [RFC4422], [RFC5890], [RFC6365], and		[I-D.ietf-precis-framework], [RFC5890], [RFC6365], and [UNICODE].
	[UNICODE]. The term "non-ASCII space" refers to any Unicode code		The term "non-ASCII space" refers to any Unicode code point having a
	point with a general category of "Zs", with the exception of U+0020		general category of "Zs", with the exception of U+0020 (here called
	(here called "ASCII space").		"ASCII space").
	As used here, the term "password" is not literally limited to a word;		As used here, the term "password" is not literally limited to a word;
	i.e., a password could be a passphrase consisting of more than one		i.e., a password could be a passphrase consisting of more than one
	word, perhaps separated by spaces or other such characters.		word, perhaps separated by spaces or other such characters.
			Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify
			that the authentication identity used in the context of such
			mechanisms is a "simple user name" (see Section 2 of [RFC4422] as
			well as [RFC4013]). Various application technologies also assume
			that the identity of a user or account takes the form of a username
			(e.g., authentication for the HyperText Transfer Protocol [RFC2617]),
			whether or not they use SASL. Note well that the exact form of a
			username in any particular SASL mechanism or application technology
			is a matter for implementation and deployment, and that a username
			does not necessarily map to any particular application identifier
			(such as the localpart of an email address).
	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].
	2. Simple User Names		4. Usernames
	2.1. Definition
	Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify
	that the authentication identity used in the context of such
	mechanisms is a "simple user name" (see Section 2 of [RFC4422] as
	well as [RFC4013]). However, the exact form of a simple user name in
	any particular mechanism or deployment thereof is a local matter, and
	a simple user name does not necessarily map to an application
	identifier such as the localpart of an email address.
	For purposes of preparation and comparison of authentication		4.1. Definition
	identities, this document specifies that a simple user name is a
	string of Unicode code points [UNICODE], encoded using UTF-8
	[RFC3629], and structured either as an ordered sequence of
	"simpleparts" (where the complete simple user name can consist of a
	single simplepart or a space-separated sequence of simpleparts) or as
	a simplepart@domainpart (where the domainpart is an IP literal, an
	IPv4 address, or a fully-qualified domain name).
	Therefore the syntax for a simple user name is defined as follows		This document specifies that a username is a string of Unicode code
	using the Augmented Backus-Naur Form (ABNF) as specified in		points [UNICODE], encoded using UTF-8 [RFC3629], and structured
	[RFC5234].		either as an ordered sequence of "userparts" (where the complete
			username can consist of a single userpart or a space-separated
			sequence of userparts) or as a userpart@domainpart (where the
			domainpart is an IP literal, an IPv4 address, or a fully-qualified
			domain name).
	simpleusername = simplepart [1*(1*SP simplepart)]		The syntax for a username is defined as follows using the Augmented
	/ simplepart '@' domainpart		Backus-Naur Form (ABNF) [RFC5234].
	simplepart = 1*(idpoint)
	;
	; an "idpoint" is a UTF-8 encoded
	; Unicode code point that conforms to
	; the PRECIS "IdentifierClass"
	;
	domainpart = IP-literal / IPv4address / ifqdn
	;
	; the "IPv4address" and "IP-literal"
	; rules are defined in RFC 3986, and
	; the first-match-wins (a.k.a. "greedy")
	; algorithm described in RFC 3986
	; applies to the matching process
	;
	; note well that reuse of the IP-literal
	; rule from RFC 3986 implies that IPv6
	; addresses are enclosed in square
	; brackets (i.e., beginning with '['
	; and ending with ']')
	;
	ifqdn = 1*1023(domainpoint)
	;
	; a "domainpoint" is a UTF-8 encoded
	; Unicode code point that conforms to
	; RFC 5890
	;
	Note well that all code points and blocks not explicitly allowed in		username = userpart [1*(1*SP userpart)]
	the PRECIS IdentifierClass are disallowed; this includes private use		/ userpart '@' domainpart
	characters, surrogate code points, and the other code points and		userpart = 1*(idpoint)
	blocks defined as "Prohibited Output" in Section 2.3 of RFC 4013.		;
			; an "idpoint" is a UTF-8 encoded Unicode code point
			; that conforms to the PRECIS "IdentifierClass"
			;
			domainpart = IP-literal / IPv4address / ifqdn
			;
			; the "IPv4address" and "IP-literal" rules are
			; defined in RFC 3986, and the first-match-wins
			; (a.k.a. "greedy") algorithm described in RFC 3986
			; applies
			;
			; reuse of the IP-literal rule from RFC 3986 implies
			; that IPv6 addresses are enclosed in square brackets
			; (i.e., beginning with '[' and ending with ']')
			;
			ifqdn = 1*1023(domainpoint)
			;
			; a "domainpoint" is a UTF-8 encoded Unicode code
			; point that conforms to RFC 5890
			;
	Note also that common constructions such as "user@example.com" are		All code points and blocks not explicitly allowed in the PRECIS
	allowed as simple user names when using software that conforms to		IdentifierClass are disallowed; this includes private use characters,
	this specification, as they were under [RFC4013].		surrogate code points, and the other code points and blocks that were
			defined as "Prohibited Output" in [RFC4013]. In addition, common
			constructions such as "user@example.com" are allowed as usernames
			under this specification, as they were under [RFC4013].
	2.2. Preparation		4.2. Preparation
	A simple user name MUST NOT be zero bytes in length. This rule is to		A username MUST NOT be zero bytes in length. This rule is to be
	be enforced after any normalization and mapping of code points.		enforced after any normalization and mapping of code points.
	Each simplepart of a simple user name MUST conform to the definition		Each userpart of a username MUST conform to the definition of the
	of the PRECIS IdentifierClass provided in		PRECIS IdentifierClass provided in [I-D.ietf-precis-framework], where
	[I-D.ietf-precis-framework], where the width mapping, additional		the width mapping, additional mapping, case mapping, normalization,
	mapping, case mapping, normalization, and directionality rules are as		and directionality rules are as follows.
	described below.
	1. Fullwidth and halfwidth characters MUST be mapped to their		1. Fullwidth and halfwidth characters MUST be mapped to their
	decomposition equivalents.		decomposition equivalents.
	2. So-called additional mappings MAY be applied, such as those		2. So-called additional mappings MAY be applied, such as those
	defined in [I-D.ietf-precis-mappings].		defined in [I-D.ietf-precis-mappings].
	3. Uppercase and titlecase characters MAY be mapped to their		3. Uppercase and titlecase characters SHOULD be mapped to their
	lowercase equivalents.		lowercase equivalents (not doing so can lead to false positives
			during authentication and authorization, as described in
			[RFC6943]).
	4. Unicode Normalization Form C (NFC) MUST be applied to all		4. Unicode Normalization Form C (NFC) MUST be applied to all
	characters.		characters.
	With regard to directionality, the "Bidi Rule" provided in [RFC5893]		With regard to directionality, the "Bidi Rule" provided in [RFC5893]
	applies.		applies.
	SASL mechanisms that directly re-use this profile MUST specify		SASL mechanisms that directly re-use this profile MUST specify
	whether case mapping is to be applied to authentication IDs, and		whether and when case mapping is to be applied to authentication
	when. SASL mechanisms SHOULD delay any case mapping to the last		identifiers. SASL mechanisms SHOULD delay any case mapping to the
	possible moment, such as when doing a lookup by username, username		last possible moment, such as when doing a lookup by username,
	comparisons, or generating a cryptographic salt from a username.		username comparisons, or generating a cryptographic salt from a
			username. In keeping with RFC4422, SASL mechanisms are not to apply
			this or any other profile to authorization identifiers.
	Application protocols that use SASL (such as IMAP [RFC4616] and XMPP		Application protocols that use SASL (such as IMAP [RFC4616] and XMPP
	[RFC6120]) and that directly re-use this profile MUST specify whether		[RFC6120]) and that directly re-use this profile MUST specify whether
	case mapping is to be applied to authorization IDs. Such "SASL		case mapping is to be applied to authorization identifiers. Such
	application protocols" SHOULD delay any case mapping of authorization		"SASL application protocols" SHOULD delay any case mapping of
	IDs to the last possible moment, which happens to necessarily be on		authorization identifiers to the last possible moment, which happens
	the server side.		to necessarily be on the server side. In keeping with RFC4422, SASL
			application protocols are not to apply this or any other profile to
			authentication identifiers.
	In keeping with RFC4422, SASL application protocols are not to apply		Application protoocls that do not use SASL (such as HTTP
	this or any other profile to authentication IDs, and SASL mechanisms		authentication with the Basic and Digest schemes [RFC2617]) MUST
	are not to apply this or any other profile to authorization IDs.		specify whether and when case mapping is to be applied to
			authentication identifiers and authorization identifiers. Such
			application protocols SHOULD delay any case mapping to the last
			possible moment, such as when doing a lookup by username, username
			comparisons, or generating a cryptographic salt from a username.
	3. Passwords		In protocols that provide usernames as input to a cryptographic
			algorithm such as a hash function, the client will need to perform
			proper preparation of the username before applying the algorithm,
			since the username is not available to the server in plaintext form.
	3.1. Definition		5. Passwords
			5.1. Definition
	For purposes of preparation and comparison of passwords, this		This document specifies that a password is a string of Unicode code
	document specifies that a password is a string of Unicode code points		points [UNICODE], encoded using UTF-8 [RFC3629], and conformant to
	[UNICODE], encoded using UTF-8 [RFC3629], and conformant to the		the PRECIS FreeformClass.
	PRECIS FreeformClass.
	Therefore the syntax for a password is defined as follows using the		The syntax for a password is defined as follows using the Augmented
	Augmented Backus-Naur Form (ABNF) as specified in [RFC5234].		Backus-Naur Form (ABNF) [RFC5234].
	password = 1*(freepoint)		password = 1*(freepoint)
	;		;
	; a "freepoint" is a UTF-8 encoded		; a "freepoint" is a UTF-8 encoded
	; Unicode code point that conforms to		; Unicode code point that conforms to
	; the PRECIS "FreeformClass"		; the PRECIS "FreeformClass"
	;		;
	Note well that all code points and blocks not explicitly allowed in		All code points and blocks not explicitly allowed in the PRECIS
	the PRECIS FreeformClass are disallowed; this includes private use		FreeformClass are disallowed; this includes private use characters,
	characters, surrogate code points, and the other code points and		surrogate code points, and the other code points and blocks defined
	blocks defined as "Prohibited Output" in Section 2.3 of RFC 4013.		as "Prohibited Output" in Section 2.3 of RFC 4013.
	3.2. Preparation		5.2. Preparation
	A password MUST NOT be zero bytes in length. This rule is to be		A password MUST NOT be zero bytes in length. This rule is to be
	enforced after any normalization and mapping of code points.		enforced after any normalization and mapping of code points.
	A password MUST be treated as follows, where the operations specified		A password MUST conform to the definition of the PRECIS FreeformClass
	MUST be completed in the order shown:		provided in [I-D.ietf-precis-framework], where the width mapping,
			additional mapping, case mapping, normalization, and directionality
			rules are as described below.
	1. Width mapping is not applied.		1. Fullwidth and halfwidth characters MUST NOT be mapped to their
	2. Map any instances of non-ASCII space to ASCII space (U+0020).		decomposition equivalents.
	3. Case mapping is not applied.		2. Any instances of non-ASCII space MUST be mapped to ASCII space
	4. Apply Unicode Normalization Form C (NFC) to all characters.		(U+0020).
	5. Ensure that the resulting string conforms to the definition of		3. So-called additional mappings MAY be applied, such as those
	the PRECIS FreeformClass.		defined in [I-D.ietf-precis-mappings].
			4. Uppercase and titlecase characters MUST NOT be mapped to their
			lowercase equivalents.
			5. Unicode Normalization Form C (NFC) MUST be applied to all
			characters.
	With regard to directionality, the "Bidi Rule" (defined in [RFC5893])		With regard to directionality, the "Bidi Rule" (defined in [RFC5893])
	and similar rules are unnecessary and inapplicable to passwords,		and similar rules are unnecessary and inapplicable to passwords,
	since they can reduce the range of characters that are allowed in a		since they can reduce the range of characters that are allowed in a
	string and therefore reduce the amount of entropy that is possible in		string and therefore reduce the amount of entropy that is possible in
	a password. Furthermore, such rules are intended to minimize the		a password. Furthermore, such rules are intended to minimize the
	possibility that the same string will be displayed differently on a		possibility that the same string will be displayed differently on a
	system set for right-to-left display and a system set for left-to-		system set for right-to-left display and a system set for left-to-
	right display; however, passwords are typically not displayed at all		right display; however, passwords are typically not displayed at all
	and are rarely meant to be interoperable across different systems in		and are rarely meant to be interoperable across different systems in
	the way that non-secret strings like domain names and user names are.		the way that non-secret strings like domain names and usernames are.
	4. Migration		In protocols that provide passwords as input to a cryptographic
			algorithm such as a hash function, the client will need to perform
			proper preparation of the password before applying the algorithm,
			since the password is not available to the server in plaintext form.
			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.
	4.1. User Names		6.1. Usernames
	Deployments that currently use SASLprep for handling user names might		Deployments that currently use SASLprep for handling usernames might
	need to scrub existing data when migrating to use of the rules		need to scrub existing data when migrating to use of the rules
	defined in this specification. In particular:		defined in this specification. In particular:
	o SASLprep specified the use of Unicode Normalization Form KC		o SASLprep specified the use of Unicode Normalization Form KC
	(NFKC), whereas this usage of the PRECIS IdentifierClass employs		(NFKC), whereas this usage of the PRECIS IdentifierClass employs
	Unicode Normalization Form C (NFC). In practice this change is		Unicode Normalization Form C (NFC). In practice this change is
	unlikely to cause significant problems, because NFKC provides		unlikely to cause significant problems, because NFKC provides
	methods for mapping Unicode code points with compatibility		methods for mapping Unicode code points with compatibility
	equivalents to those equivalents, whereas the PRECIS		equivalents to those equivalents, whereas the PRECIS
	IdentifierClass entirely disallows Unicode code points with		IdentifierClass entirely disallows Unicode code points with
	skipping to change at page 8, line 20 ¶		skipping to change at page 8, line 46 ¶
	might suffice to indicate the nature of the problem: (1) U+017F		might suffice to indicate the nature of the problem: (1) U+017F
	LATIN SMALL LETTER LONG S is compatibility equivalent to U+0073		LATIN SMALL LETTER LONG S is compatibility equivalent to U+0073
	LATIN SMALL LETTER S (2) U+2163 ROMAN NUMERAL FOUR is		LATIN SMALL LETTER S (2) U+2163 ROMAN NUMERAL FOUR is
	compatibility equivalent to U+0049 LATIN CAPITAL LETTER I and		compatibility equivalent to U+0049 LATIN CAPITAL LETTER I and
	U+0056 LATIN CAPITAL LETTER V (3) U+FB01 LATIN SMALL LIGATURE FI		U+0056 LATIN CAPITAL LETTER V (3) U+FB01 LATIN SMALL LIGATURE FI
	is compatibility equivalent to U+0066 LATIN SMALL LETTER F and		is compatibility equivalent to U+0066 LATIN SMALL LETTER F and
	U+0069 LATIN SMALL LETTER I. Under SASLprep, the use of NFKC also		U+0069 LATIN SMALL LETTER I. Under SASLprep, the use of NFKC also
	handled the mapping of fullwidth and halfwidth code points to		handled the mapping of fullwidth and halfwidth code points to
	their decomposition equivalents (see [I-D.ietf-precis-mappings]).		their decomposition equivalents (see [I-D.ietf-precis-mappings]).
	Although it is expected that code points with compatibility		Although it is expected that code points with compatibility
	equivalents are rare in existing user names, for migration		equivalents are rare in existing usernames, for migration purposes
	purposes deployments might want to search their database of user		deployments might want to search their database of usernames for
	names for Unicode code points with compatibility equivalents and		Unicode code points with compatibility equivalents and map those
	map those code points to their compatibility equivalents.		code points to their compatibility equivalents.
	o SASLprep mapped non-ASCII spaces to ASCII space (U+0020), whereas		o SASLprep mapped non-ASCII spaces to ASCII space (U+0020), whereas
	the PRECIS IdentifierClass entirely disallows non-ASCII spaces.		the PRECIS IdentifierClass entirely disallows non-ASCII spaces.
	The non-ASCII space characters are U+00A0 NO-BREAK SPACE, U+1680		The non-ASCII space characters are U+00A0 NO-BREAK SPACE, U+1680
	OGHAM SPACE MARK, U+180E MONGOLIAN VOWEL SEPARATOR, U+2000 EN QUAD		OGHAM SPACE MARK, U+180E MONGOLIAN VOWEL SEPARATOR, U+2000 EN QUAD
	through U+200A HAIR SPACE, U+202F NARROW NO-BREAK SPACE, U+205F		through U+200A HAIR SPACE, U+202F NARROW NO-BREAK SPACE, U+205F
	MEDIUM MATHEMATICAL SPACE, and U+3000 IDEOGRAPHIC SPACE. For		MEDIUM MATHEMATICAL SPACE, and U+3000 IDEOGRAPHIC SPACE. For
	migration purposes, deployments might want to convert non-ASCII		migration purposes, deployments might want to convert non-ASCII
	space characters to ASCII space in simple user names.		space characters to ASCII space in usernames.
	o SASLprep mapped the "characters commonly mapped to nothing" from		o SASLprep mapped the "characters commonly mapped to nothing" from
	Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS		Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
	IdentifierClass entirely disallows most of these characters, which		IdentifierClass entirely disallows most of these characters, which
	correspond to the code points from the "M" category defined under		correspond to the code points from the "M" category defined under
	Section 6.13 of [I-D.ietf-precis-framework] (with the exception of		Section 6.13 of [I-D.ietf-precis-framework] (with the exception of
	U+1806 MONGOLIAN TODO SOFT HYPHEN, which was "commonly mapped to		U+1806 MONGOLIAN TODO SOFT HYPHEN, which was "commonly mapped to
	nothing" in Unicode 3.2 but at the time of this writing does not		nothing" in Unicode 3.2 but at the time of this writing does not
	have a derived property of Default_Ignorable_Code_Point in Unicode		have a derived property of Default_Ignorable_Code_Point in Unicode
	6.1). For migration purposes, deployments might want to remove		6.2). For migration purposes, deployments might want to remove
	code points contained in the PRECIS "M" category from simple user		code points contained in the PRECIS "M" category from usernames.
	names.
	o SASLprep allowed uppercase and titlecase characters, whereas this		o SASLprep allowed uppercase and titlecase characters, whereas this
	usage of the PRECIS IdentifierClass maps uppercase and titlecase		usage of the PRECIS IdentifierClass maps uppercase and titlecase
	characters to their lowercase equivalents. For migration		characters to their lowercase equivalents. For migration
	purposes, deployments can either convert uppercase and titlecase		purposes, deployments can either convert uppercase and titlecase
	characters to their lowercase equivalents in simple user names		characters to their lowercase equivalents in usernames (thus
	(thus losing the case information) or preserve uppercase and		losing the case information) or preserve uppercase and titlecase
	titlecase characters and ignore the case difference when comparing		characters and ignore the case difference when comparing
	simple user names.		usernames.
	4.2. Passwords		6.2. Passwords
	Depending on local service policy, migration from RFC 4013 to this		Depending on local service policy, migration from RFC 4013 to this
	specification might not involve any scrubbing of data (since		specification might not involve any scrubbing of data (since
	passwords might not be stored in the clear anyway); however, service		passwords might not be stored in the clear anyway); however, service
	providers need to be aware of possible issues that might arise during		providers need to be aware of possible issues that might arise during
	migration. In particular:		migration. In particular:
	o SASLprep specified the use of Unicode Normalization Form KC		o SASLprep specified the use of Unicode Normalization Form KC
	(NFKC), whereas this usage of the PRECIS FreeformClass employs		(NFKC), whereas this usage of the PRECIS FreeformClass employs
	Unicode Normalization Form C (NFC). Because NFKC is more		Unicode Normalization Form C (NFC). Because NFKC is more
	skipping to change at page 9, line 43 ¶		skipping to change at page 10, line 21 ¶
	might no longer work when the rules in this specification are		might no longer work when the rules in this specification are
	applied.		applied.
	o SASLprep mapped the "characters commonly mapped to nothing" from		o SASLprep mapped the "characters commonly mapped to nothing" from
	Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS		Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
	FreeformClass entirely disallows such characters, which correspond		FreeformClass entirely disallows such characters, which correspond
	to the code points from the "M" category defined under Section		to the code points from the "M" category defined under Section
	6.13 of [I-D.ietf-precis-framework] (with the exception of U+1806		6.13 of [I-D.ietf-precis-framework] (with the exception of U+1806
	MONGOLIAN TODO SOFT HYPHEN, which was commonly mapped to nothing		MONGOLIAN TODO SOFT HYPHEN, which was commonly mapped to nothing
	in Unicode 3.2 but at the time of this writing is allowed by		in Unicode 3.2 but at the time of this writing is allowed by
	Unicode 6.1). In practice, this change will probably have no		Unicode 6.2). In practice, this change will probably have no
	effect on comparison, but user-oriented software might reject such		effect on comparison, but user-oriented software might reject such
	code points instead of ignoring them during password preparation.		code points instead of ignoring them during password preparation.
	5. Security Considerations		7. Security Considerations
	5.1. Password/Passphrase Strength
			7.1. Password/Passphrase Strength
	The ability to include a wide range of characters in passwords and		The ability to include a wide range of characters in passwords and
	passphrases can increase the potential for creating a strong password		passphrases can increase the potential for creating a strong password
	with high entropy. However, in practice, the ability to include such		with high entropy. However, in practice, the ability to include such
	characters ought to be weighed against the possible need to reproduce		characters ought to be weighed against the possible need to reproduce
	them on various devices using various input methods.		them on various devices using various input methods.
	5.2. Identifier Comparison		7.2. Identifier Comparison
	The process of comparing identifiers (such as SASL simple user names,		The process of comparing identifiers (such as SASL simple user names,
	authentication identifiers, and authorization identifiers) can lead		authentication identifiers, and authorization identifiers) can lead
	to either false negatives or false positives, both of which have		to either false negatives or false positives, both of which have
	security implications. A more detailed discussion can be found in		security implications. A more detailed discussion can be found in
	[RFC6943].		[RFC6943].
	5.3. Reuse of PRECIS		7.3. Reuse of PRECIS
	The security considerations described in [I-D.ietf-precis-framework]		The security considerations described in [I-D.ietf-precis-framework]
	apply to the "IdentifierClass" and "FreeformClass" base string		apply to the "IdentifierClass" and "FreeformClass" base string
	classes used in this document for simple user names and passwords,		classes used in this document for usernames and passwords,
	respectively.		respectively.
	5.4. Reuse of Unicode		7.4. Reuse of Unicode
	The security considerations described in [UTR39] apply to the use of		The security considerations described in [UTR39] apply to the use of
	Unicode characters in user names and passwords.		Unicode characters in usernames and passwords.
	6. IANA Considerations		8. IANA Considerations
	6.1. Use of IdentifierClass		[Note to RFC Editor: please change XXXX to the number issued for this
			specification.]
			8.1. Use of IdentifierClass
	The IANA shall add an entry to the PRECIS Usage Registry for reuse of		The IANA shall add an entry to the PRECIS Usage Registry for reuse of
	the PRECIS IdentifierClass in SASL, as follows:		the PRECIS IdentifierClass, as follows:
	Applicability: Usernames in SASL and Kerberos.		Applicability: Usernames in security and application protocols.
	Base Class: IdentifierClass.		Base Class: IdentifierClass.
	Subclass: No.		Subclass: No.
	Replaces: The SASLprep profile of Stringprep.		Replaces: The SASLprep profile of Stringprep.
	Width Mapping: Map fullwidth and halfwidth characters to their		Width Mapping: Map fullwidth and halfwidth characters to their
	decomposition equivalents.		decomposition equivalents.
	Additional Mappings: None.		Additional Mappings: None.
	Case Mapping: To be defined by application protocols that use this		Case Mapping: Not recommended, but to be defined by application
	profile.		protocols that use this profile.
	Normalization: NFC.		Normalization: NFC.
	Directionality: The "Bidi Rule" defined in RFC 5893 applies.		Directionality: The "Bidi Rule" defined in RFC 5893 applies.
	Specification: RFC XXXX. [Note to RFC Editor: please change XXXX to		Specification: RFC XXXX.
	the number issued for this specification.]
	6.2. Use of FreeformClass		8.2. Use of FreeformClass
	The IANA shall add an entry to the PRECIS Usage Registry for reuse of		The IANA shall add an entry to the PRECIS Usage Registry for reuse of
	the PRECIS FreeformClass in SASL, as follows:		the PRECIS FreeformClass, as follows:
	Applicability: Passwords in SASL and Kerberos.		Applicability: Passwords in security and application protocols.
	Base Class: FreeformClass		Base Class: FreeformClass
	Subclass: No.		Subclass: No.
	Replaces: The SASLprep profile of Stringprep.		Replaces: The SASLprep profile of Stringprep.
	Width Mapping: None.		Width Mapping: None.
	Additional Mappings: Map non-ASCII space characters to ASCII space.		Additional Mappings: Map non-ASCII space characters to ASCII space.
	Case Mapping: None.		Case Mapping: None.
	Normalization: NFC.		Normalization: NFC.
	Directionality: None.		Directionality: None.
	Specification: RFC XXXX. [Note to RFC Editor: please change XXXX to		Specification: RFC XXXX.
	the number issued for this specification.]
	7. Open Issues
	We need to compare the output obtained when applying the new rules
	with Unicode 3.2 and Unicode 6.1 data to the output obtained when
	applying the SASLprep rules with Unicode 3.2 data, then make sure
	that the PRECIS Working Group and KITTEN Working Group are
	comfortable with any changes to the Unicode characters that are
	allowed and disallowed. (See also the migration issues described
	under Section 4.)
	8. References
	8.1. Normative References		9. References
			9.1. Normative References
	[I-D.ietf-precis-framework]		[I-D.ietf-precis-framework]
	Saint-Andre, P. and M. Blanchet, "Precis Framework:		Saint-Andre, P. and M. Blanchet, "Precis Framework:
	Handling Internationalized Strings in Protocols",		Handling Internationalized Strings in Protocols",
	draft-ietf-precis-framework-09 (work in progress),		draft-ietf-precis-framework-09 (work in progress),
	July 2013.		July 2013.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO		[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
	10646", STD 63, RFC 3629, November 2003.		10646", STD 63, RFC 3629, November 2003.
	[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax		[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
	Specifications: ABNF", STD 68, RFC 5234, January 2008.		Specifications: ABNF", STD 68, RFC 5234, January 2008.
	[UNICODE] The Unicode Consortium, "The Unicode Standard, Version		[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
	6.1", 2012,		6.1", 2012,
	<http://www.unicode.org/versions/Unicode6.1.0/>.		<http://www.unicode.org/versions/Unicode6.1.0/>.
	8.2. Informative References		9.2. Informative References
	[I-D.ietf-precis-mappings]		[I-D.ietf-precis-mappings]
	YONEYA, Y. and T. NEMOTO, "Mapping characters for PRECIS		YONEYA, Y. and T. NEMOTO, "Mapping characters for PRECIS
	classes", draft-ietf-precis-mappings-02 (work in		classes", draft-ietf-precis-mappings-02 (work in
	progress), May 2013.		progress), May 2013.
			[RFC20] Cerf, V., "ASCII format for network interchange", RFC 20,
			October 1969.
			[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
			Leach, P., Luotonen, A., and L. Stewart, "HTTP
			Authentication: Basic and Digest Access Authentication",
			RFC 2617, June 1999.
	[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of		[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
	Internationalized Strings ("stringprep")", RFC 3454,		Internationalized Strings ("stringprep")", RFC 3454,
	December 2002.		December 2002.
	[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names		[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
	and Passwords", RFC 4013, February 2005.		and Passwords", RFC 4013, February 2005.
	[RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple		[RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
	Authentication and Security Layer (SASL)", RFC 4422,		Authentication and Security Layer (SASL)", RFC 4422,
	June 2006.		June 2006.
	skipping to change at page 13, line 21 ¶		skipping to change at page 13, line 41 ¶
	[RFC6943] Thaler, D., "Issues in Identifier Comparison for Security		[RFC6943] Thaler, D., "Issues in Identifier Comparison for Security
	Purposes", RFC 6943, May 2013.		Purposes", RFC 6943, May 2013.
	[UTR39] The Unicode Consortium, "Unicode Technical Report #39:		[UTR39] The Unicode Consortium, "Unicode Technical Report #39:
	Unicode Security Mechanisms", August 2010,		Unicode Security Mechanisms", August 2010,
	<http://unicode.org/reports/tr39/>.		<http://unicode.org/reports/tr39/>.
	Appendix A. Differences from RFC 4013		Appendix A. Differences from RFC 4013
			This document builds upon the PRECIS framework defined in
			[I-D.ietf-precis-framework], which differs fundamentally from the
			stringprep technology [RFC3454] used in SASLprep [RFC4013]. The
			primary difference is that stringprep profiles allowed all characters
			except those which were explicitly disallowed, whereas PRECIS
			profiles disallow all characters except those which are explicitly
			allowed (this "inclusion model" was originally used for
			internationalized domain names in [RFC5891]; see [RFC5894] for
			further discussion). It is important to keep this distinction in
			mind when comparing the technology defined in this document to
			SASLprep [RFC4013].
	The following substantive modifications were made from RFC 4013.		The following substantive modifications were made from RFC 4013.
	o A single SASLprep algorithm was replaced by two separate		o A single SASLprep algorithm was replaced by two separate
	algorithms: one for simple user names and another for passwords.		algorithms: one for usernames and another for passwords.
	o The new preparation algorithms use PRECIS instead of a stringprep		o The new preparation algorithms use PRECIS instead of a stringprep
	profile. The new algorithms work independenctly of Unicode		profile. The new algorithms work independenctly of Unicode
	versions.		versions.
	o As recommended in the PRECIS framwork, changed the Unicode		o As recommended in the PRECIS framwork, changed the Unicode
	normalization form to NFC (from NFKC).		normalization form to NFC (from NFKC).
	o Some Unicode code points that were mapped to nothing in RFC 4013		o Some Unicode code points that were mapped to nothing in RFC 4013
	are simply disallowed by PRECIS.		are simply disallowed by PRECIS.
	Appendix B. Acknowledgements		Appendix B. Acknowledgements
	The following individuals provided helpful feedback on this document:		The following individuals provided helpful feedback on this document:
	Marc Blanchet, Alan DeKok, Joe Hildebrand, Jeffrey Hutzelman, Simon		Marc Blanchet, Alan DeKok, Joe Hildebrand, Jeffrey Hutzelman, Simon
	Josefsson, Jonathan Lennox, Matt Miller, Chris Newman, Pete Resnick,		Josefsson, Jonathan Lennox, Matt Miller, Chris Newman, Yutaka OIWA,
	Andrew Sullivan, and Nico Williams (Nico in particular provided text		Pete Resnick, Andrew Sullivan, and Nico Williams (Nico in particular
	that was used in Section 2.2). Thanks also to Yoshiro YONEYA and		provided text that was used in Section 2.2). Thanks also to Yoshiro
	Takahiro NEMOTO for implementation feedback.		YONEYA and Takahiro NEMOTO for implementation feedback.
	This document borrows some text from [RFC4013] and [RFC6120].		This document borrows some text from [RFC4013] and [RFC6120].
	Authors' Addresses		Authors' Addresses
	Peter Saint-Andre		Peter Saint-Andre
	Cisco Systems, Inc.		Cisco Systems, Inc.
	1899 Wynkoop Street, Suite 600		1899 Wynkoop Street, Suite 600
	Denver, CO 80202		Denver, CO 80202
	USA		USA
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