< draft-zeilenga-ldap-authpasswd-04.txt		draft-zeilenga-ldap-authpasswd-05.txt >
			A new Request for Comments is now available in online RFC libraries.
	INTERNET-DRAFT Kurt D. Zeilenga		RFC 3112
	Intended Category: Standard Track OpenLDAP Foundation
	Expires: 20 July 2001 20 January 2001
	LDAP Authentication Password Attribute
	<draft-zeilenga-ldap-authpasswd-04.txt>
	1. Status of this Memo
	This document is an Internet-Draft and is in full conformance with all
	provisions of Section 10 of RFC2026.
	This document is intended to be, after appropriate review and
	revision, submitted to the RFC Editor as an Standard Track document.
	Distribution of this memo is unlimited. Technical discussion of this
	document will take place on the IETF LDAP Extension Working Group
	mailing list <ietf-ldapext@netscape.com>. Please send editorial
	comments directly to the author <Kurt@OpenLDAP.org>.
	Internet-Drafts are working documents of the Internet Engineering Task
	Force (IETF), its areas, and its working groups. Note that other
	groups may also distribute working documents as Internet-Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as ``work in progress.''
	The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft
	Shadow Directories can be accessed at http://www.ietf.org/shadow.html.
	Copyright 2001, The Internet Society. All Rights Reserved.
	Please see the Copyright section near the end of this document for
	more information.
	2. Abstract
	This document describes schema in support of user/password
	authentication in a LDAP directory including the authPassword
	attribute type. This attribute type holds values derived from the
	user's password(s) (commonly using cryptographic strength one-way
	hash). authPassword is intended to used instead of userPassword.
	The key words ``MUST'', ``MUST NOT'', ``REQUIRED'', ``SHALL'', ``SHALL
	NOT'', ``SHOULD'', ``SHOULD NOT'', ``RECOMMENDED'', and ``MAY'' in
	this document are to be interpreted as described in RFC 2119
	[RFC2119].
	3. Background and Intended Use
	The userPassword attribute type [RFC 2256] is intended be used to used
	to support the LDAP [RFC2251] "simple" bind operation. However,
	values of userPassword must be clear text passwords. It is often
	desirable to store values derived from the user's password(s) instead
	of actual passwords.
	The authPassword attribute type is intended to be used to store
	information used to implement simple password based authentication.
	The attribute type may be used by LDAP servers to implement the LDAP
	Bind operation's "simple" authentication method.
	The attribute type supports multiple storage schemes. A matching rule
	is provided for use with extensible search filters to allow clients to
	assert that a clear text password "matches" one of the attribute's
	values.
	Storage schemes often use of cryptographic strength one-way hashing.
	Though the use of one-way hashing reduces the potential that exposed
	values will allow unauthorized access to the Directory (unless the
	hash algorithm/implementation is flawed), the hashing of passwords is
	intended to be as an additional layer of protection. It is
	RECOMMENDED that hashed values be protected as if they were clear text
	passwords.
	This attribute may be used in conjunction with server side password
	generation mechanisms (such as [PW-EXOP]).
	Access to this attribute may governed by administrative controls such
	as those which implement password change policies.
	4. Schema Definitions
	The following schema definitions are described in terms of LDAPv3
	Attribute Syntax Definitions [RFC2252] with specific syntax detailed
	using Augmented BNF [RFC2234].
	Editor's Note: object identifiers (OIDs) will be assigned before this
	document is published as an RFC.
	4.1. authPasswordSyntax
	( authPasswordSyntaxOID
	DESC 'authentication password syntax' )
	Values of this syntax are encoded according to:
	authPasswordValue = w scheme s [authInfo] s authValue w
	scheme = %x30-39 / %x41-5A / %x2D-2F / %x5F
	; 0-9, A-Z, "-", ".", "/", or "_"
	authInfo = schemeSpecificValue
	authValue = schemeSpecificValue
	schemeSpecificValue = *( %x21-23 / %25-7E )
	; printable ascii less "$" and " "
	s = w sep w
	w = *sp
	sep = %x24 ; dollar sign
	sp = %x20 ; space
	where scheme describes the mechanism and authInfo and authValue are a
	scheme specific. The authInfo field is often a base64 encoded salt.
	The authValue field is often a base64 encoded value derived from a
	user's password(s). Values of this attribute are case sensitive.
	This document describes a number of schemes, as well as requirements
	for the scheme naming, in section 5.
	4.2. authPasswordMatch
	( authPasswordMatchOID
	NAME 'authPasswordMatch'
	DESC 'authentication password matching rule'
	SYNTAX 1.3.6.1.4.1.1466.115.121.1.40{128} )
	This matching rule allows a client to assert that a password matches
	values of authPasswordSyntax using an extensibleMatch filter
	component. Each value is matched per its scheme. The assertion is
	TRUE if one or more attribute values matches the asserted value, FALSE
	if all values do not matches, and Undefined otherwise.
	Servers which support use of this matching rule SHOULD publish
	appropriate matchingRuleUse values per [RFC2252], 4.4.
	Transfer of authPasswordMatch assertion values is strongly discouraged
	where the underlying transport service cannot guarantee
	confidentiality and may result in disclosure of the values to
	unauthorized parties.
	4.3. supportedAuthPasswordSchemes
	( supportedAuthPasswordSchemesOID
	NAME 'supportedAuthPasswordSchemes'
	DESC 'supported password storage schemes'
	EQUALITY caseExactIA5Match
	SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{32}
	USAGE dSAOperation )
	The values of this attribute are names of supported authentication
	password schemes which the server supports. The syntax of a scheme
	name is described in section 4.1. This attribute may only be present
	in the root DSE. If the server does not support any password schemes,
	this attribute will not be present.
	4.4. authPassword
	( authPasswordOID NAME 'authPassword'
	SYNTAX authPasswordSyntaxOID )
	The values of this attribute are representative of the user's
	password(s) and conform to the authPasswordSyntax described in 4.1.
	The values of this attribute may be used for authentication purposes.
	This attribute type is defined without any built-in matching rules.
	The absence of an EQUALITY matching rules disallows modification of
	individual values.
	Transfer of authPassword values is strongly discouraged where the
	underlying transport service cannot guarantee confidentiality and may
	result in disclosure of the values to unauthorized parties.
	4.5. authPasswordObject
	( authPasswordObjectOID NAME 'authPasswordObject'
	DESC 'authentication password mix in class'
	MAY 'authPassword' AUXILIARY )
	Entries of this object class may contain authPassword attribute types.
	5. Schemes
	This section describes the "MD5" and "SHA1". Other schemes may be
	defined by other documents. Schemes which are not described by
	standard track documents SHOULD be named with a leading "X-" to
	indicate they are a private or implementation specific scheme, or may
	be named using the dotted-decimal representation [RFC2252] of an OID
	assigned to the scheme.
	5.1. MD5 scheme
	The MD5 [RFC1321] scheme name is "MD5".
	The authValue is the base64 encoding of an MD5 digest of the
	concatenation the user password and salt. The base64 encoding of the
	salt is provided in the authInfo field. The salt MUST be at least
	64-bits long. Implementations of this scheme MUST support salts up to
	128-bit in length.
	Example:
	Given a user "joe" who's password is "mary" and a salt of "salt",
	the authInfo field would be the base64 encoding of "salt" and the
	authValue field would be the base64 encoding of the MD5 digest of
	"marysalt".
	A match against an asserted password and an attribute value of this
	scheme SHALL be true if and only if the MD5 digest of concatenation of
	the asserted value and the salt is equal to the MD5 digest contained
	in AuthValue. The match SHALL be undefined if the server is unable to
	complete the equality test for any reason. Otherwise the match SHALL
	be false.
	Values of this scheme SHOULD only be used to implement simple
	user/password authentication.
	5.2. SHA1 scheme
	The SHA1 [SHA1] scheme name is "SHA1".
	The authValue is the base64 encoding of an SHA1 digest of the
	concatenation the user password and the salt. The base64 encoding of
	the salt is provided in the authInfo field. The salt MUST be at least
	64-bits long. Implementations of this scheme MUST support salts up to
	128-bit in length.
	Example:
	Given a user "joe" who's password is "mary" and a salt of "salt",
	the authInfo field would be the base64 encoding of "salt" and the
	authValue field would be the base64 encoding of the SHA1 digest of
	"marysalt".
	A match against an asserted password and an attribute value of this
	scheme SHALL be true if and only if the SHA1 digest of concatenation
	of the asserted value and the salt is equal to the SHA1 digest
	contained in AuthValue. The match SHALL be undefined if the server is
	unable to complete the equality test for any reason. Otherwise the
	match SHALL be false.
	Values of this scheme SHOULD only be used to implement simple
	user/password authentication.
	6. Implementation Issues
	For implementations of this specification:
	Servers MAY restrict which schemes are used in conjunction with a
	particular authentication process but SHOULD use all values of
	selected schemes. If the asserted password matches any of the
	stored values, the asserted password SHOULD be considered valid.
	Servers MAY use other authentication storage mechanisms, such as
	userPassword or an external password store, in conjunction with
	authPassword to support the authentication process.
	Servers that support simple bind MUST support the SHA1 scheme and
	SHOULD support the MD5 scheme.
	Servers SHOULD not publish values of authPassword nor allow
	operations which expose authPassword or AuthPasswordMatch values to
	unless confidentiality protection is in place.
	Clients SHOULD not initiate operations which provide or request
	values of authPassword or make authPasswordMatch assertions unless
	confidentiality protection is in place.
	Clients SHOULD not assume that a successful AuthPasswordMatch,
	whether by compare or search, is sufficient to gain directory
	access. The bind operation MUST be used to authentication to the
	directory.
	7. Security Considerations
	This document describes how authentication information may be stored
	in a directory. Authentication information MUST be adequately
	protected as unintended disclosure will allow attackers to gain
	immediate access to the directory as described by [RFC2829].
	As flaws may be discovered in the hashing algorithm or with a
	particular implementation of the algorithm or may be subjected to
	dictionary or other attacks if exposed, values of AuthPassword SHOULD
	be protected as if they were clear text passwords. When values are
	transferred, privacy protections, such as IPSEC or TLS, SHOULD be in
	place.
	Clients SHOULD use strong authentication mechanisms [RFC2829].
	AuthPasswordMatch matching rule allows applications to test the
	validity of a user password and, hence, may be used to mount an
	attack. Servers SHOULD take appropriate measures to protect the
	directory from such attacks.
	Some password schemes may require CPU intensive operations. Servers
	SHOULD take appropriate measures to protect against Denial of Service
	attacks.
	AuthPassword does not restrict an authentication identity to a single
	password. An attacker who gains write access to this attribute may
	store additional values without disabling the user's true password(s).
	Use of policy aware clients and servers is RECOMMENDED.
	The level of protection offered against various attacks differ from
	scheme to scheme. It is RECOMMENDED that servers support scheme
	selection as a configuration item. This allows for a scheme to be
	easily disabled if a significant security flaw is discovered.
	8. Copyright
	Copyright 2001, The Internet Society. All Rights Reserved.
	This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain it
	or assist in its implementation may be prepared, copied, published and
	distributed, in whole or in part, without restriction of any kind,
	provided that the above copyright notice and this paragraph are
	included on all such copies and derivative works. However, this
	document itself may not be modified in any way, such as by removing
	the copyright notice or references to the Internet Society or other
	Internet organizations, except as needed for the purpose of
	developing Internet standards in which case the 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 be
	revoked by the Internet Society or its successors or assigns.
	This document and the information contained herein is provided on an
	"AS IS" basis and THE AUTHORS, 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.
	9. Acknowledgment
	This document borrows from a number of IETF documents and is based
	upon input from the IETF LDAPext working group.
	10. Bibliography
	[RFC1321] R. Rivest, "The MD5 Message-Digest Algorithm", RFC 1321,
	April 1992
	[RFC2219] S. Bradner, "Key words for use in RFCs to Indicate
	Requirement Levels", RFC 2119, March 1997.
	[RFC2222] J. Myers, "Simple Authentication and Security Layer (SASL)",
	RFC 2222, October 1997.
	[RFC2234] D. Crocker (editor), P. Overell, "Augmented BNF for Syntax		Title: LDAP Authentication Password Schema
	Specifications: ABNF", RFC 2234, November 1997.		Author(s): K. Zeilenga
			Status: Informational
			Date: May 2001
			Mailbox: Kurt@OpenLDAP.org
			Pages: 9
			Characters: 17116
			Updates/Obsoletes/SeeAlso: None
	[RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access		I-D Tag: draft-zeilenga-ldap-authpasswd-05.txt
	Protocol (v3)", RFC 2251, December 1997.
	[RFC2252] M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight		URL: ftp://ftp.rfc-editor.org/in-notes/rfc3112.txt
	Directory Access Protocol (v3): Attribute Syntax
	Definitions", RFC 2252, December 1997.
	[RFC2256] M. Wahl, "A Summary of the X.500(96) User Schema for use		This document describes schema in support of user/password
	with LDAPv3", RFC 2256, December 1997.		authentication in a LDAP (Lightweight Directory Access Protocol)
			directory including the authPassword attribute type. This attribute
			type holds values derived from the user's password(s) (commonly using
			cryptographic strength one-way hash). authPassword is intended to
			used instead of userPassword.
	[RFC2307] L. Howard, "An Approach for Using LDAP as a Network		This memo provides information for the Internet community. It does
	Information Service", RFC 2307, March 1998. (not normative)		not specify an Internet standard of any kind. Distribution of this
			memo is unlimited.
	[RFC2829] M. Wahl, H. Alvestrand, J. Hodges, RL "Bob" Morgan,		This announcement is sent to the IETF list and the RFC-DIST list.
	"Authentication Methods for LDAP", RFC 2829, June 2000.		Requests to be added to or deleted from the IETF distribution list
			should be sent to IETF-REQUEST@IETF.ORG. Requests to be
			added to or deleted from the RFC-DIST distribution list should
			be sent to RFC-DIST-REQUEST@RFC-EDITOR.ORG.
	[PW-EXOP] K. Zeilenga, "LDAP Password Modify Extended Operation"		Details on obtaining RFCs via FTP or EMAIL may be obtained by sending
	draft-zeilenga-ldap-passwd-exop-xx.txt, a work in progress.		an EMAIL message to rfc-info@RFC-EDITOR.ORG with the message body
			help: ways_to_get_rfcs. For example:
	[SHA1] NIST, FIPS PUB 180-1: Secure Hash Standard, April 1995.		To: rfc-info@RFC-EDITOR.ORG
			Subject: getting rfcs
	11. Author's Address		help: ways_to_get_rfcs
	Kurt D. Zeilenga		Requests for special distribution should be addressed to either the
	OpenLDAP Foundation		author of the RFC in question, or to RFC-Manager@RFC-EDITOR.ORG. Unless
	<Kurt@OpenLDAP.org>		specifically noted otherwise on the RFC itself, all RFCs are for
			unlimited distribution.echo
			Submissions for Requests for Comments should be sent to
			RFC-EDITOR@RFC-EDITOR.ORG. Please consult RFC 2223, Instructions to RFC
			Authors, for further information.
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