Network Working Group A. Findlay
Internet-Draft Skills 1st Ltd
Expires: March 16, 2008 September 13, 2007
The LDAP groupOfEntries object class
draft-findlay-ldap-groupofentries-00
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Copyright (C) The IETF Trust (2007).
Abstract
This memo describes the LDAP groupOfEntries object class which is a
replacement for the existing groupOfNames class. The new class
permits the creation of empty groups.
If approved as a Standards Track document, this document will update
RFC4519 [2]
Document Intent
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as a Standards Track document.
Distribution of this memo is unlimited. Technical discussion of this
document will take place on the IETF LDAP Extensions mailing list
<ldapext@ietf.org>. Please send editorial comments directly to the
author <andrew.findlay@skills-1st.co.uk>
1. Introduction
A groupOfNames object class has existed since the earliest X.521 [1]
standard. It has an identical definition in LDAP (RFC4519 [2]). The
class is used to define entries holding DN-valued member attributes,
each value pointing to an entry that represents a single member of
the group being described, or to another entry of type groupOfNames.
groupOfNames is a structural object class, so it is often the only
class used in the definition of group objects.
Experience has shown that the definition of groupOfNames causes
difficulties in practice. In particular, the fact that 'member' is a
mandatory attribute means that it is not possible to create an empty
group or to delete the last member from a group. This leads to
artificial tricks such as making every group a member of itself, or
adding a dummy member to every group when it is created. These
tricks in turn make the management of groups more complex and prone
to error. Groups are commonly used to control access to resources,
so management errors can lead to security risks.
There does not appear to be any good reason for the 'member'
attribute to be mandatory. This memo describes a new object class
called groupOfEntries that is equivalent to groupOfNames in all other
respects but which makes 'member' an optional attribute.
2. The existing groupOfNames object class
RFC4519 [2] contains this definition:
The 'groupOfNames' object class is the basis of an entry that
represents a set of named objects including information related to
the purpose or maintenance of the set. (Source: X.521 [1])
( 2.5.6.9 NAME 'groupOfNames'
SUP top
STRUCTURAL
MUST ( member $
cn )
MAY ( businessCategory $
seeAlso $
owner $
ou $
o $
description ) )
The inclusion of 'member' in the 'MUST' section of the definition
prevents empty groups from being created.
3. The groupOfEntries object class
The 'groupOfEntries' object class is the basis of an entry that
represents a set of named objects including information related to
the purpose or maintenance of the set. It should be used in
preference to the 'groupOfNames' object class.
( 1.2.826.0.1.3458854.2.1.1.1 NAME 'groupOfEntries'
SUP top
STRUCTURAL
MUST ( cn )
MAY ( member $
businessCategory $
seeAlso $
owner $
ou $
o $
description ) )
This object class allows groups to be empty. In all other respects
it behaves like the groupOfNames object class.
The OID assigned to this object class is delegated by Skills 1st Ltd.
4. Effect on other documents
This draft deprecates the use of the groupOfNames object class in
RFC4519 [2] and replaces it with the groupOfEntries class.
5. IANA considerations
It is requested that IANA register upon Standards Action the
groupOfEntries Object Identifier Descriptor and its associated OID.
6. Security considerations
Groups are commonly used to define access permissions to directory
entries and resources in other services. Allowing for empty groups
avoids the risks associated with leaving a dummy placeholder member
in group entries, so security is improved.
Appendix A. Acknowledgements
The author gratefully acknowledges the contributions of Michael
Stroeder to the first draft of this document.
7. Informative References
[1] "The Directory: Selected Object Classes", ITU-T
Recommendation X.521, March 1988.
[2] "LDAP: Schema for User Applications", RFC 4519, June 2006.
Author's Address
Andrew Findlay
Skills 1st Ltd
2 Cedar Chase
Taplow
Maidenhead SL6 0EU
GB
Phone: +44 1628 782565
Email: andrew.findlay@skills-1st.co.uk
URI: http://www.skills-1st.co.uk/
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