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Versions: 00 01 02 03 04 05 06 07 rfc3876                               
Internet-Draft                                      David Chadwick
LDAPExt WG                                         University of Salford
Intended Category: Standards Track                     Sean Mullan
                                                                  Sun Microsystems
Expires: 1 January 2001                             1 July 2000


Returning Matched Values with LDAPv3
<draft-ietf-ldapext-matchedval-02.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 1 January 2001. Comments and
suggestions on this document are encouraged. Comments on this
document should be sent to the LDAPExt working group discussion list:
                ietf-ldapext@netscape.com
or directly to the authors.


ABSTRACT

This document describes a control for the Lightweight Directory
Access Protocol v3 that is used to return a subset of attribute
values from an entry, specifically, only those values that match a
"values return" filter. Without support for this control, a client
must retrieve all of an attribute's values and search for specific
values locally.


1. Introduction

When reading an attribute from an entry using LDAP v2 [1] or LDAPv3
[2], it is normally only possible to read either the attribute type,
or the attribute type and all its values. It is not possible to
selectively read just a few of the attribute values. If an attribute
holds many values, for example, the userCertificate attribute, or the
subschema publishing operational attributes objectClasses and
attributeTypes [3], then it may be desirable for the user to be able
to selectively retrieve a subset of the values, specifically, those
attribute values that match some user defined selection criteria.
Without the control specified in this [ID/standard] a client must
read all of the attribute's values and filter out the unwanted
values, necessitating the client to implement the matching rules. It
also requires the client to potentially read and process many
irrelevant values, which can be inefficient if the values are large
or complex, or there are many values stored per attribute.

This Internet Draft specifies an LDAPv3 control to enable a user to
return only those values that matched (i.e. returned TRUE to) one or
more elements of a newly defined "values return" filter. This control
can be especially useful when used in conjunction with extensible
matching rules that match on one or more components of complex binary
attribute values.

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. The valuesReturnFilter Control

The valuesReturnFilter control MAY be critical or non-critical as
determined by the user. It is only applicable to the Search
operation, and SHALL be ignored by the server if it is present on any
other LDAP operation (even if marked critical on such operations).

The object identifier for this control is 1.2.826.0.1.3344810.2.3


The controlValue is

        ValuesReturnFilter ::= SEQUENCE OF SimpleFilterItem

        SimpleFilterItem ::= CHOICE {
                equalityMatch   [3] AttributeValueAssertion,
                substrings      [4] SubstringFilter,
                greaterOrEqual  [5] AttributeValueAssertion,
                lessOrEqual     [6] AttributeValueAssertion,
                present         [7] AttributeDescription,
                approxMatch     [8] AttributeValueAssertion,
                extensibleMatch [9] SimpleMatchingAssertion }

         SimpleMatchingAssertion ::= SEQUENCE {
                matchingRule    [1] MatchingRuleId OPTIONAL,
                type            [2] AttributeDescription OPTIONAL,
                matchValue      [3] AssertionValue}

All the above data types have their standard meanings as defined in
[2].

If the server supports this control, the server MUST make use of the
control as follows:

(1) The Search Filter is first executed in order to determine
which entries satisfy the Search criteria. The control has no
impact on this step.

(2) If the typesOnly parameter of the Search Request is TRUE,
the control has no effect and the Search Request SHOULD be
processed as if the control had not been specified.

(3) If the attributes parameter of the Search Request consists
of a list containing only the attribute with OID "1.1"
(specifying that no attributes are to be returned), the control
has no effect and the Search Request SHOULD be processed as if
the control had not been specified.

(4) For each attribute listed in the attributes parameter of the
Search Request, the server MUST apply the control as follows:

i) Every attribute value that evaluates TRUE against one or
more elements of the ValuesReturnFilter is placed in the
SearchResultEntry.
ii) Every attribute value that evaluates FALSE or undefined
against all elements of the ValuesReturnFilter is not
placed in the SearchResultEntry. An attribute that has no
values selected is returned with an empty set of vals.

Editor's Note. There is possibly a more efficient but slightly more
complex way of achieving the value filtering. An alternative is to
remove the 'present' SimpleFilterItem (which obviously evaluates true
for every attribute value of the 'present' attribute description),
and to say that any attribute whose type is not mentioned in the
ValuesReturnFilter is not filtered and has all its attribute values
returned. Comments please.


3. Relationship to X.500

The control is a superset of the matchedValuesOnly boolean of the
X.500 DAP [4] Search argument, as amended in the latest version [6].
Close examination of the matchedValuesOnly boolean by the LDAPExt
group revealed ambiguities and complexities in the MVO boolean that
could not easily be resolved. For example, are only those attribute
values that contributed to the overall truth of the filter governed
by the MVO boolean, or all values of attributes in the filter
governed by the MVO boolean, even if the filter item containing the
attribute evaluated to false. For this reason the LDAP group decided
to replace the MVO boolean with a simple filter that removes any
uncertainty as to whether an attribute value has been selected or
not.


4. Examples

(1) The first example simply shows how the control can be used to
selectively read a subset of attribute values.

The entry below represents a groupOfNames object class containing
several members from different organizations.

cn: Cross Organizational Standards Body
member: cn=joe,o=acme
member: cn=alice,o=acme
member: cn=bob,o=foo
member: cn=sue,o=bar

An LDAP search operation is specified with a baseObject set to the
DN of the entry, a baseObject scope, a filter set to
"member=*o=acme", and the list of attributes to be returned set to
"member". In addition, a ValuesReturnFilter control is set to
"member=*o=acme".

The search results returned by the server would consist of the
following entry:

cn: Cross Organizational Standards Body
member: cn=joe, o=acme
member: cn=alice, o=acme


(2) The second example shows how the control can be set to match on
attributes that are (mail) and are not (telephoneNumber) part of the
search filter. It also shows how a user can filter some attribute
values (mail) and not others (telephoneNumber).

The entries below represent inetOrgPerson [7] object classes located
below some distinguished name in the directory.

cn: Sean Mullan
mail: sean.mullan@sun.com
mail: mullan@east.sun.com
telephoneNumber: +1 781 442 0926
telephoneNumber: 555-9999

cn: David Chadwick
mail: d.w.chadwick@salford.ac.uk

An LDAP search operation is specified with a baseObject set to the
DN of the entry, a subtree scope, a filter set to
"(|(mail=sean.mullan@sun.com)(mail=d.w.chadwick@salford.ac.uk))", and
the list of attributes to be returned set to "mail telephoneNumber".
In addition, a ValuesReturnFilter control is set to
"mail=sean.mullan@sun.com, mail=d.w.chadwick@salford.ac.uk,
telephoneNumber=*"

The search results returned by the server would consist of the
following entries:

cn: Sean Mullan
mail: sean.mullan@sun.com
telephoneNumber: +1 781 442 0926
telephoneNumber: 555-9999

cn: David Chadwick
mail: d.w.chadwick@salford.ac.uk

Note that the control has no effect on the values returned for the
"telephoneNumber" attribute (all of the values are returned), since
the control specified that all values should be returned.

(3) The third example shows how one might retrieve a single attribute
type schema definition for the "gunk" attribute with OID 1.2.3.4.5

Assume the subschema subentry is held somewhere below the root entry
with RDN "subschema subentry", and this holds an attributeTypes
operational attribute holding the descriptions of the 35 attributes
known to this server (each description is held as a single attribute
value of the attributeTypes attribute).

cn: subschema subentry
objectClass: subschema
attributeTypes: ( 2.5.4.3 NAME 'cn' SUP name )
attributeTypes: ( 2.5.4.6 NAME 'c' SUP name SINGLE-VALUE )
attributeTypes: ( 2.5.4.0 NAME 'objectClass' EQUALITY
objectIdentifierMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.38 )
attributeTypes: ( 2.5.18.2 NAME 'modifyTimestamp' EQUALITY
generalizedTimeMatch ORDERING generalizedTimeOrderingMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.24 SINGLE-VALUE NO-USER-
MODIFICATION USAGE directoryOperation )
attributeTypes: ( 2.5.21.6 NAME 'objectClasses' EQUALITY
objectIdentifierFirstComponentMatch SYNTAX
1.3.6.1.4.1.1466.115.121.1.37 USAGE directoryOperation )
attributeTypes: ( 1.2.3.4.5 NAME 'gunk' EQUALITY caseIgnoreMatch
SUBSTR caseIgnoreSubstringsMatch SYNTAX
1.3.6.1.4.1.1466.115.121.1.44{64} )
attributeTypes: ( 2.5.21.5 NAME 'attributeTypes' EQUALITY
objectIdentifierFirstComponentMatch SYNTAX
1.3.6.1.4.1.1466.115.121.1.3 USAGE directoryOperation )

plus another 28 - you get the idea.


The user creates an LDAP search operation with a baseObject set to
root, a subtree scope, a filter set to "objectClass=subschema", the
list of attributes to be returned set to "attributeTypes", and the
ValuesReturnFilter set to "attributeTypes=1.2.3.4.5"

The search result returned by the server would consist of the
following entry:

cn: subschema subentry
attributeTypes: ( 1.2.3.4.5 NAME 'gunk' EQUALITY caseIgnoreMatch
SUBSTR caseIgnoreSubstringsMatch SYNTAX
1.3.6.1.4.1.1466.115.121.1.44{64} )

(4) The final example shows how the control can be set to match on
attributes that are not part of the search filter. For example,
searching for all entries that have an email address in the
sun.com domain, and returning the telephone number for any attribute
values that start with "555".

The entries below represent inetOrgPerson [7] object classes located
below some distinguished name in the directory.

cn: Sean Mullan
mail: sean.mullan@sun.com
mail: mullan@east.sun.com
telephoneNumber: +1 781 442 0926
telephoneNumber: 555-9999

cn: David Chadwick
mail: d.w.chadwick@salford.ac.uk

An LDAP search operation is specified with a baseObject set to the
DN of the entry, a subtree scope, a filter set to "mail=*sun.com",
and the list of attributes to be returned set to "telephoneNumber".
In addition, a ValuesReturnFilter control is set to
"telephoneNumber=555*"

The search results returned by the server would consist of the
following entry:

cn: Sean Mullan
telephoneNumber: 555-9999


5. Security Considerations

This Internet Draft does not discuss security issues at all.

Note that attribute values MUST only be returned if the access
controls applied by the LDAP server allow them to be returned, and in
this respect the effect of the ValuesReturnFilter control is of no
consequence.

Note that the ValuesReturnFilter control may have a positive effect
on the deployment of public key infrastructures. Certain PKI
operations, like searching for specific certificates, become more
practical (when combined with X.509 certificate matching rules at the
server) and more scalable, since the control avoids the downloading
of potentially large numbers of irrelevant certificates which would
have to be processed and filtered locally (which in some cases is
very difficult to perform).


6. Acknowledgements

The authors would like to thank members of the LDAPExt list for their
constructive comments on earlier versions of this draft, and in
particular to Harald Alvestrand who first suggested having an
attribute return filter and Bruce Greenblatt who first proposed a
syntax for this control.

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] Yeong, W., Howes, T., and Kille, S. "Lightweight Directory Access
Protocol", RFC 1777, March 1995.
[2] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol (v3)", Dec. 1997, RFC 2251
[3] M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3): Attribute Syntax Definitions", RFC 2252, Dec
1997
[4] ITU-T Rec. X.511, "The Directory: Abstract Service Definition",
1993.
[5] S.Bradner. "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[6] ISO/IEC 9594 / ITU-T Rec X.511 (2000) The Directory: Abstract
Service Definition.
[7] M. Smith. "Definition of the inetOrgPerson LDAP Object Class",
Internet Draft <draft-smith-ldap-inetorgperson-03.txt>, April 1999.


9. Authors Addresses

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

Email: d.w.chadwick@salford.ac.uk


Sean Mullan
Sun Microsystems
East Point Business Park
Dublin 3
Ireland
Tel: +353 1 853 0655
Email: sean.mullan@sun.com

Internet-Draft   Returning Matched Values with LDAPv3     1 July 2000


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