Subject: New ID on LDAPv3

From: "David Chadwick" <[email-masked]>
Date: Tue, 15 Jun 1999 18:35:59 +0100

Folks,

A new ID has just been (or is just about to be) published

<draft-chadwick-pkixldap-v3-00.txt>

This gives a profile for the use of LDAPv3 to retrieve X.509 
certificates and CRLs.

I append a copy to this message. I believe there will be a brief 
discussion of this on the Wednesday morning in Oslo

David

***************************************************

David Chadwick
IT Institute, University of Salford, Salford M5 4WT
Tel +44 161 295 5351  Fax +44 161 745 8169
*NEW* Mobile +44 790 167 0359 *NEW*
Email [email-masked]
Home Page  http://www.salford.ac.uk/its024/chadwick.htm
Understanding X.500  http://www.salford.ac.uk/its024/X500.htm
X.500/LDAP Seminars http://www.salford.ac.uk/its024/seminars.htm
Entrust key validation string MLJ9-DU5T-HV8J

***************************************************

Internet-Draft                                       D.W.Chadwick
PKIX WG                       		   University of Salford      
Intended Category: Standards Track             
Expires: 12 December 1999                            12 June, 1999

                 Internet X.509 Public Key Infrastructure
                      Operational Protocols – LDAPv3
                 <draft-chadwick-pkixldap-v3-00.txt>

STATUS OF THIS MEMO

This document is an Internet-Draft and is in full conformance with 
all the provisions of Section 10 of RFC2026.

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.

This Internet-Draft expires on December 12, 1999. Comments and 
suggestions on this document are encouraged. Comments on this 
document should be sent to the PKIX working group discussion list:
                <[email-masked]>
or directly to the author.

ABSTRACT

This document describes the features of the Lightweight Directory 
Access Protocol v3 that are needed in order to support a public key 
infrastructure based on X.509 certificates and CRLs.

1. Introduction

RFC 2559 [1] specifies the subset of LDAPv2 [2] that is necessary to 
retrieve X.509 [9] certificates and CRLs from LDAP servers. However 
LDAPv2 has a number of deficiencies that may limit its usefulness in 
certain circumstances. The most notable of these are:

      - LDAPv2 distinguished names must be composed from the IA5 
character set and cannot contain accented or non-latin characters,

      - LDAPv2 only has a limited number of supported authentication 
schemes for binding to the server, in particular the use of hashed 
passwords or TLS [3] are not supported,

       - LDAPv2 only supports a single directory server. It is the 
responsibility of the user to pre-configure his client with the 
required set of LDAP servers, and to choose the correct one for each 
certificate and CRL retrieval.

It is for these reasons (and others not listed here) that the IETF 
have stopped the standardisation of the LDAPv2 protocol and have 
replaced it with the LDAPv3 protocol [4]. However the LDAPv3 protocol 
is much more complex than the LDAPv2 protocol and many of its 
features are not essential for simple PKIX use. This document 
describes the features of LDAPv3 that are essential, or not required, 
or are optional for servers to support a PKI based on X.509.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",  
"SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this 
document are to be interpreted as described in RFC 2119 [5].

2. Features Of Ldapv3 That MUST Be Supported

Attribute descriptions are a superset of attribute type definitions. 
They allow attribute subtyping to be specified in the LDAPv3 
protocol. The ;binary option is exception to this. This option allows 
certificates and CRLs to be asked for and returned as binary values 
encoded using the Basic Encoding Rules [11]. The mechanism described 
in PKIX LDAPv2 [1] is fully compliant with the ;binary option of 
LDAPv3. The ;binary option of attribute descriptions MUST be 
supported by all implementations.  Other attribute description 
options SHOULD NOT be supported by clients. Servers MAY choose to 
support them at their discretion.

UTF8 encoding [12] allows the full ISO 10646 character set to be used 
in the creation of distinguished names. UTF8 encoding of 
distinguished names MUST be supported as specified in RFC2253 [6].

The altServer attribute is used by servers to point to alternative 
servers that may be contacted if this server is temporarily 
unavailable. This attribute MUST be stored in the root DSE of the 
server and MUST be available to clients for retrieval. If no 
alternative servers exist this attribute MUST point to the current 
server. Clients MAY make use of this feature but do not need to. 
Servers MAY store any other operational attributes in the root DSE, 
but do not need to.

3. Features Of Ldapv3 That SHOULD Be Supported

In a distributed directory with multiple servers, LDAPv3 supports 
referrals as the mechanism to allow one server that cannot fulfil a 
client’s request, to refer the client to another server that might be 
better able to fulfil the request. Servers SHOULD be able to return 
referrals to clients. Clients SHOULD be able to receive referrals, 
although they are not required to automatically process them and 
support multiple asynchronous outgoing connections. As a minimum, 
clients SHOULD be able to ask the user if the referrals are be cached 
locally and added to the set of servers known to the client. 

Partial Search results are returned when a server only has a subset 
of the certificates requested by the client. Referrals to other 
servers are embedded in the SearchResultReference field. Clients and 
servers SHOULD be able to handle SearchResultReferences in the same 
way as they handle referrals.

4. Features Of Ldapv3 That SHOULD NOT Be Supported

The client SHOULD NOT support the ModifyDN, Compare and Abandon 
operations. The server MAY choose to support these operations at its 
discretion.

The LDAPv3 protocol is infinitely extensible via two mechanisms: 
extended operations and controls on existing operations. The client 
SHOULD NOT generate any LDAPv3 protocol extensions (extended 
operations or controls).  The server SHOULD NOT return any LDAPv3 
protocol extensions (extended operations or controls).

LDAPv3 has the concept of unsolicited notifications that can be sent 
from the server to the client. The server SHOULD NOT generate any 
unsolicited notifications.

LDAPv3 allows the subschema supported by the server to be published 
in a subschema subentry. Subschema publishing is not needed for 
normal PKI use, therefore the client SHOULD NOT try to retrieve 
either the contents of the subschema subentry or the pointer to it 
(held in the subschemaSubentry attribute of the root DSE) from the 
server. The server MAY publish its subschema at its discretion.

Operational attributes are attributes stored by the server that hold 
administrative information. Clients SHOULD NOT request any 
operational attributes from the server other than the altServer 
attribute, and the server need not store any operational attributes 
other than altServer.

5. Features Of Ldapv3 That MAY Be Supported

If the CPS allows unauthenticated anonymous access to the server, 
then the server MUST allow a client to perform a Search operation 
(for a "read" or "search" type request) without issuing a prior Bind 
operation. The server MUST also allow the client to present a Bind 
request with the simple authentication choice and a zero-length OCTET 
STRING.

If the CPS allows weak password based authentication for "read" or 
"search" access to the server, the client and the server SHOULD 
support the DIGEST-MD5 mechanism [7] as specified in [8], and may 
support a simple password Bind sequence following the negotiation of 
a TLS ciphersuite to provide connection confidentiality, as specified 
in [10].

If the CPS requires strong authentication for access to the server 
then the client and the server SHOULD support certificate based 
authentication as specified in [10].

The parameters of the Search operation for "read" or "search" type 
queries will usually be set as specified in RFC 2559. However, 
X.509(1997) [9] supports flexible certificate matching by the server, 
via the certificateMatch MATCHING-RULE. For example, a client may 
search for certificates with a particular validity time, key usage, 
policy or other field. If the server supports flexible matching, then 
the extensibleMatch filter item MUST be supported. Clients MAY 
support the extensibleMatch filter item.

6. Security Considerations

The PKI information to be retrieved from LDAPv3 servers (certificates 
and CRLs) is digitally signed and therefore additional integrity 
services are NOT REQUIRED. The CPS will specify whether the 
information should be publicly available or not. If publicly 
available, privacy services will NOT be REQUIRED for retrieval 
requests. If not publicly available, privacy services MAY be REQUIRED 
and these can be provided by a TLS ciphersuite as specified in clause 
5.

For update of the information by CAs either strong authentication or 
weaker password based authentication MUST be supported as specified 
in clause 5. Additional access controls SHOULD be provided.

Organizations are NOT REQUIRED to provide external CAs or users with 
access to their directories.

7 Copyright

Copyright (C) The Internet Society (date). 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 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.

8. References

[1] S.Boeyen, T. Howes, P. Richard "Internet X.509 Public Key 
Infrastructure Operational Protocols - LDAPv2", RFC 2559, April 1999
[2] Yeong, W., Howes, T., and Kille, S. "Lightweight Directory Access 
Protocol", RFC 1777, March 1995.
[3] T. Dierks, C. Allen. "The TLS Protocol Version 1.0", RFC 2246, 
January 1999.
[4] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access  
Protocol (v3)", Dec. 1997, RFC 2251
[5] S.Bradner. "Key words for use in RFCs to Indicate Requirement 
Levels", RFC 2119, March 1997.
[6] M. Wahl, S. Kille, T. Howes. "Lightweight Directory Access 
Protocol (v3): UTF-8 String Representation of Distinguished Names", 
RFC2253, December 1997.
[7] Digest md5
[8] P. Leach, C. Newman, "Using Digest Authentication as a SASL 
Mechanism", INTERNET DRAFT <draft-leach-digest-sasl-01.txt>, November 
1998.
[9] X.509(97)
[10] M. Wahl, H. Alvestrand, J. Hodges, RL "Bob" Morgan. 
"Authentication Methods for LDAP" <draft-ietf-ldapext-authmeth-
03.txt>, November 1998
[11] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules: Basic, 
Canonical, and Distinguished Encoding Rules", 1994.
[12] F. Yergeau. "UTF-8, a transformation format of ISO 10646", RFC 
2279, January 1998.

10 Authors Address

David Chadwick
IS Institute
University of Salford
Salford
England
M5 4WT 

Email: [email-masked]

Internet-Draft   PKIX Operational Protocols – LDAPv3     12 June 1999

---

From: "David Chadwick" <[email-masked]>
Date: Thu, 17 Jun 1999 19:43:35 +0100

From:           	"John Hughes" <[email-masked]>
To:             	<[email-masked]>
Subject:        	RE: New ID on LDAPv3
Date sent:      	Thu, 17 Jun 1999 13:53:04 +0100

> David,
> 
> the one thing missing from LDAPv3 is the ability to retrieve a given value
> in a multi-value attribute.
> 
> Some PKI products need this!

Good point, I will add this to the next version.

David

> 
> John
> 
> 
> 
> > -----Original Message-----
> > From: David Chadwick [mailto:[email-masked]]
> > Sent: 15 June 1999 18:36
> > To: [email-masked]
> > Subject: New ID on LDAPv3
> >
> >
> > Folks,
> >
> > discussion of this on the Wednesday morning in Oslo> > 

David Chadwick