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Internet drafts associated with LDAP alias change changelog implementation.

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Internet-Draft D. Byrne, IBM
LDAP Extensions WG L. Poitou, Sun
Intended Category: Standards Track E. Stokes, IBM
Expires: 20 October 1998
20 April 1998
Use of Aliases within LDAP
<draft-byrne-ldap-alias-00.txt>
STATUS OF THIS MEMO
This document is an Internet Draft. 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. Internet Drafts may be updated, replaced, or obsoleted
by other documents at any time. It is not appropriate to use
Internet Drafts as reference material or to cite them other
than as a "working draft" or "work in progress."
To view the entire list of current Internet-Drafts, please
check the "1id-abstracts.txt" listing contained in the
Internet-Drafts Shadow Directories on ftp.is.co.za (Africa),
ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern
Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East
Coast), or ftp.isi.edu (US West Coast).
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
ABSTRACT
This document describes the suggested behavior for aliases for
LDAPv3 and above to improve LDAP server interoperability .
The key words "MUST", "SHOULD", and "MAY" used in this
document are to be interpreted as described in [Bradner97].
1. Objectives
Aliases may be used within LDAP to reference entries anywhere
within the directory tree. Conceptually, an alias is simply a
pointer to the DIT entry it represents. It does not contain
additional information about that entry; only the location of
the entry.
The behavior of the alias object within LDAP is not well-
defined, both in creation of the alias object and the behavior
when dereferencing the alias.
For successful interoperability, the expected behavior of
servers when encountering alias objects SHOULD be consistent.
Additionally, it MUST be possible to use aliases without
changing the LDAPv3 schema as defined in [Wahl] and without
adding server-dependent data.
2. Schema Definition
2.1 Schema Expansion
The alias objectclass definitions presented in the LDAPv3
Schema [Wahl] are the basis for aliasing within ldap. The
alias objectclass is a Structural objectclass with a single
required attribute; the single valued aliasObjectName.
This definition of the alias objectclass does not allow for
any attribute other than 'aliasedObjectName' to be used as the
naming attribute within the RDN. The resulting dn for the
alias object must therefore be of the form
"aliasedObjectName=<dn>, <rdn>, <rdn>..." This is not a
user-friendly name for a directory entry, and quite possibly
corrupts the naming hierarchy within the directory tree.
In order to remain true the concept of an alias; that it is
merely a pointer to another entry, an entry of objectclass
alias SHOULD NOT be combined with any other objectclass. If
multiple objectclasses are combined, it becomes possible to
add information to the alias entry without violating the
schema rules.
While not explicitly specified as either a 'required' or
'may', any naming attribute MUST be allowed to form the RDN of
the alias. Restricting the possible naming attributes would
potentially corrupt the hierarchy. For example, it would be
impossible to distinguish between a person alias and an
organisation alias.
2.2 AliasObject Objectclass
In order to create an alias object which can be appropriately
named to that which it represents, the definition of the alias
object MUST be expanded. A new objectclass must be defined
which inherits from the current definition of alias but
extends the attributes allowed within the RDN.
( 1.3.6.1.4.1.42.2.27.1.2.1
NAME 'aliasObject'
DESC objectclass for all alias objects
SUP 'ALIAS'
MAY *
)
The '*' allows any naming attribute to be used in forming the
RDN of the object.
For example, the following is a correct LDIF:
dn: cn=John Doe, ou=myOrg, c=US
objectclass: alias
objectclass: aliasObject
aliasedObjectName: cn=President, ou=myOrg, c=US
cn: John Doe
To prevent the alias from containing extra information about
the object, the naming attribute SHOULD contain only a single
value.
For example, the following is not a correct LDIF:
dn: cn=John Doe, ou=myOrg, c=US
objectclass: alias
objectclass: aliasObject
aliasedObjectName: cn=President, ou=myOrg, c=US
cn: John Doe
cn: Doe
Similarly, the following would not be a correct LDIF file
because it adds extra information to the alias object.
dn: cn=John Doe, ou=myOrg, c=US
objectclass: alias
objectclass: aliasObject
aliasedObjectName: cn=President, ou=myOrg, c=US
cn: John Doe
title: President
The naming attribute used to form the RDN of the object SHOULD
reflect the naming attribute of the referenced object.
However, there are some cases where the naming attribute MAY
be different.
Within the X.501 [ITU-T], the attribute used to described the
aliased object is 'aliasedEntryName'. Since the OID for
'aliasedEntryName' and 'aliasedObjectName' are the same for
both X.500 and LDAP, LDAP servers SHOULD treat the
'aliasedEntryName' as a synonym for 'aliasedObjectName'.
3. Alias Behavior
In general alias objects SHOULD NOT be dereferenced during any
operation other than search unless requested to do so by the
client.
Since an alias points to another section of the tree, it MUST
NOT be possible to add an object under an alias object; alias
objects MUST always be leaf nodes.
During the dereferencing of aliases, a loop is detected if the
server visits the same alias entry more than once. In this
case a data integrity error has occurred and the server MUST
return an error of 'aliasProblem'
If an alias is dereferenced, and the resulting directory entry
does not exists, a data integrity problem has occurred, and
the server MUST return an error code of
'aliasDereferencingProblem'
If the base entry for an ldapsearch is an alias, and alias
dereferencing is set to either derefFindBaseObj, or
derefAlways, the base entry MUST be dereferenced before the
search is performed. The new base for the search will become
the entry to which the alias resolves. The search is then
performed.
If multiple aliases are chained, the alias for the first
object MUST resolve to the last entry in the chain. For
example, A, B, and C are alias objects. If A points to B which
points to C which points to D, A resolves to D when
dereferencing the alias.
If an alias is dereferenced as part of a search, the alias
entry itself SHOULD NOT be returned as part of the search.
If an alias matches the search filter, and dereferencing is
set to 'searching' or 'always', the dereferenced object SHOULD
be returned, even if it does not match the filter.
If the alias is not dereferenced during the search, and it
matches the filter, then it SHOULD be returned within the
search result.
Each directory object matching a filter SHOULD be returned
only once during a search. If an entry is found twice because
of aliases pointing to a part of the tree already searched,
the entry SHOULD NOT be returned to the client a second time.
4. Scenarios
Using the following LDIF, the scenarios would return the
expected information as follows:
dn: c=myCountry
c: myCountry
objectclass: country
dn: ou=Area1, c=myCountry
ou: Area1
aliasedObjectName: o=myCorporation, c=myCountry
objectclass: alias
objectclass:aliasObject
dn: o=myCorporation, c=myCountry
ou: myCorporation
objectclass:organization
dn: cn=President, o=myCorporation, c=myCountry
cn: President
aliasObjectName: cn=John Doe, o=myCorporation, c=myCountry
objectclass: alias
objectclass: aliasObject
dn: cn=John Doe, o=myCorporation, c=myCountry
cn: John Doe
objectclass: person
c = myCountry
/ |
ou = Area1 -----> o = myCorporation
| \
cn=President ---> cn = John Doe
Performing a base search of 'ou = Area1, c=myCountry' with a
filter of 'objectclass=aliasObject'
NeverDerefAlias would return 'ou=Area1, c=myCountry'
DerefFinding would return 'cn=President, o=myCorporation,
c=myCountry'
DerefSearching would return 'o=myCorporation,
c=myCountry'
DerefAlways would return 'cn=John Doe, o=myCorporation,
c=myCountry'
Performing a one level search of 'c=myCountry' with a filter
of 'ou = * '
NeverDerefAlias would return 'ou=Area1, c=myCountry'
DerefFinding would return 'ou=Area1, c=myCountry'
DerefSearching would return 'o=myCorporation,
c=myCountry'
DerefAlways would return ' o=myCorporation, c=myCountry'
Performing a full tree search of 'c=myCountry' with a filter
of ' cn = President '
NeverDerefAlias would return 'cn=President, o=myCorporation,
c=myCountry'
DerefFinding would return 'cn=President, o=myCorporation,
c=myCountry'
DerefSearching would return 'cn=John Doe, o=myCorporation,
c=myCountry'
DerefAlways would return 'cn=John Doe, o=myCorporation,
c=myCountry'
6. Security Considerations
Permissions to dereferencing an alias, adding, deleting or
returning alias entries are decided by the directory server's
ACL administration policy.
7. References
[LDAPv3] M. Wahl, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
[Whal] M.Wahl, A, Coulbeck, T. Howes, S. Kille, "Lightweight
Directory Access Protocol (v3)": Attribute Syntax Definitions,
RFC 2252, December 1997.
[Bradner97] Bradner, Scott, "Key Words for use in RFCs to
Indicate Requirement Levels", RFC 2119.
[ITU-T] ITU-T Rec. X.501, "The Directory: Models", 1993
AUTHOR(S) ADDRESS
Debbie Byrne
IBM
11400 Burnet Rd
Austin, TX 78758
USA
mail-to: djbyrne@us.ibm.com
phone: +1 512 838 1930
Ludovic Poitou
Sun Microsystems
32, Chemin du vieux Chene
38240 Meylan
France
Phone: +33.(0)4.76.41.42.12
email: ludovic.poitou@france.sun.com
Ellen Stokes
IBM
11400 Burnet Rd
Austin, TX 78758
USA
mail-to: stokes@austin.ibm.com
phone: +1 512 838 3725

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Change Record Object Class Definition Gordon Good
INTERNET-DRAFT Netscape Communications
11 March 1998
Definition of an Object Class to Hold LDAP Change Records
Filename: draft-good-ldap-changelog-00.txt
Status of this Memo
This document is an Internet-Draft. 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.''
To learn the current status of any Internet-Draft, please check
the ``1id-abstracts.txt'' listing contained in the Internet-
Drafts Shadow Directories on ds.internic.net (US East Coast),
nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or
munnari.oz.au (Pacific Rim).
This Internet Draft expires October 1st, 1998.
Abstract
In order to support more flexible replication methods, it is
desirable to specify some manner in which an LDAP client may retrieve
a set of changes which have been applied to an LDAP server's
database. The client, which may be another LDAP server, may then
choose to update its own replicated copy of the data. This document
specifies an object class which may be used to represent changes
applied to an LDAP server. It also specifies a method for
discovering the location of the container object which holds these
change records, so that clients and servers have a common rendezvous
point for this information.
Background and Intended Usage
This document describes an objectclass which can be used to represent
Good March 11, 1998 [Page 1]
INTERNET-DRAFT Change Record Object Class 11 March 1998
changes which have been applied to a directory server. It also
suggests a common location for a container which holds these objects.
A client may update its local copy of directory information by
reading the entries within this container, and applying the changes
to its local database.
The key words "MUST", "MAY", and "SHOULD" used in this document are
to be interpreted as described in [3].
New Attribute Types Used in the changeLogEntry Object Class
( 2.16.840.1.113730.3.1.5
NAME 'changeNumber'
DESC 'a number which uniquely identifies a change made to a
directory entry'
SYNTAX 'INTEGER'
EQUALITY 'integerMatch'
ORDERING 'integerOrderingMatch' )
( 2.16.840.1.113730.3.1.6
NAME 'targetDN'
DESC 'the DN of the entry which was modified'
EQUALITY distinguishedNameMatch
SYNTAX 'DN' )
( 2.16.840.1.113730.3.1.7
NAME 'changeType'
DESC 'the type of change made to an entry'
EQUALITY caseIgnoreMatch
SYNTAX 'DirectoryString' )
( 2.16.840.1.113730.3.1.8
NAME 'changes'
DESC 'a set of changes to apply to an entry'
SYNTAX 'OctetString' )
( 2.16.840.1.113730.3.1.9
NAME 'newRDN'
DESC 'the new RDN of an entry which is the target of a
modrdn operation'
EQUALITY distinguishedNameMatch
SYNTAX 'DN' )
( 2.16.840.1.113730.3.1.10
NAME 'deleteOldRDN'
DESC 'a flag which indicates if the old RDN should be retained
as an attribute of the entry'
EQUALITY booleanMatch
Good March 11, 1998 [Page 2]
INTERNET-DRAFT Change Record Object Class 11 March 1998
SYNTAX 'BOOLEAN' )
( 2.16.840.1.113730.3.1.11
NAME 'newSuperior'
DESC 'the new parent of an entry which is the target of a
moddn operation'
EQUALITY distinguishedNameMatch
SYNTAX 'DN' )
Schema Definition of the changeLogEntry Object Class
( 2.16.840.1.113730.3.2.1
NAME 'changeLogEntry'
SUP top
STRUCTURAL
MUST (
changeNumber $ targetDN $ changeType
)
MAY (
changes $ newRDN $ deleteOldRDN $ newSuperior
)
)
Discussion of changeLogEntry Attributes:
changeNumber: the change number, as assigned by the supplier. This
integer MUST strictly increase as new entries are added, and must
always be unique within a given server. Syntax: INTEGER
targetdn: the distinguished name of the entry which was added,
modified or deleted. In the case of a modrdn operation, the targetdn
gives the DN of the entry before it was modified. Syntax: DN
changeType: the type of change. One of: "add", "delete", "modify",
"modrdn". Later RFCs may define additional values for changeType.
Syntax: DirectoryString
changes: the changes which were made to the directory server. These
changes are in LDIF format, which is described in [1].
Syntax: OctetString
newRDN: the new RDN (Relative Distinguished Name) of the entry, if the
changeType is "modrdn". If the changeType attribute does not have the
value "modrdn", then there should be no values contained in the newRDN
attribute.
Good March 11, 1998 [Page 3]
INTERNET-DRAFT Change Record Object Class 11 March 1998
Syntax: DN
deleteOldRDN: a flag which tells whether the old RDN of the entry
should be retained as a distinguished attribute of the entry, or
should be deleted. A value of "FALSE" indicates that the RDN should be
retained as a distinguished attribute, and a value of "TRUE" indicates
that it should not be retained as a distinguished attribute of the
entry. If any value other than "TRUE" or "FALSE" is contained in the
deleteOldRDN attribute, or if the deleteOldRDN contains multiple
values, the RDN should be retained as a distinguished attribute (that
is, "FALSE" is the default if no values are present, or if illegal
values are present).
Syntax: BOOLEAN
newSuperior: if present, gives the name of the entry which
becomes the immediate superior of the existing entry. This optional
attribute reflects LDAPv3 functionality, and MUST NOT be generated
by LDAPv2 servers [2].
Syntax: DN
Discussion of the changeLogEntry object class
The changeLogEntry object class is used to represent changes made to a
directory server. The set of changes made to a directory server, then,
is given by the ordered set of all entries within the changelog
container, ordered by changeNumber.
A client may synchronize its local copy of a remote directory server's
contents by searching the remote server's changelog container for any
entries where the changenumber is greater than or equal to the last
change previously retrieved from that server. If the entry with the
changenumber matching the last change retrieved is not returned in the
search results, then the server's changelog has been trimmed. The
client must then fall back to reading the entire directory to bring its
copy in sync with the server's.
Assuming that the client has successfully retrieved one or more changelog
entries from the server, it can then use the information contained in each
entry to update the corresponding entry (named by the targetDN attribute)
in its local copy of the database.
Note that, due to access control restrictions, the client is not guaranteed
read access to the "changes" attribute. If the client discovers that the
"changes" attribute has no values, then it must read the entry given by
the targetDN attribute, possibly only retrieving attributes it deems
"interesting". However, in the case of delete and modrdn operations, there
Good March 11, 1998 [Page 4]
INTERNET-DRAFT Change Record Object Class 11 March 1998
is never a "changes" attribute, so it is never necessary to read the target
entry in these cases.
Examples of the changeLogEntry object class
In each example below, the "changes" attribute is shown in plain text,
with embedded newlines. This is done for clarity. It is intended that
newlines be stored in the entry literally, not encoded in any way.
If a "changes" attribute value is stored in an LDIF file, it must
base-64 encoded.
Example 1: A changeLogEntry representing the addition of a
new entry to the directory
dn: changenumber=1923, cn=changelog
changenumber: 1923
targetdn: cn=Barbara Jensen, ou=Accounting, o=Ace Industry, c=US
changetype: add
changes: cn: Barbara Jensen\ncn: Babs Jensen\nsn: Jensen\n
givenname: Barbara\ntelephonenumber: +1 212 555-1212\nmail: babs@ace.com\n
objectclass: top\nobjectclass: person\nobjectclass: organizationalPerson\n
objectclass: inetOrgPerson
Example 2: A changeLogEntry representing the deletion of an entry
from the directory
dn: changenumber=2933, cn=changelog
changenumber: 2933
targetdn: cn=Gern Jensen, ou=Product Testing, o=Ace Industry, c=US
changetype: delete
Example 3: A changeLogEntry representing the modification of an entry
in the directory
dn: changenumber=5883, cn=changelog
changenumber: 5883
targetdn: cn=Bjorn Jensen, ou=Product Development, o=Ace Industry, c=US
changetype: modify
changes: delete: telephonenumber\ntelephonenumber: 1212\n-\n
add: telephonenumber\ntelephonenumber: +1 212 555 1212\n-
Example 4: A changeLogEntry representing a modrdn operation performed
on an entry in the directory
dn: changenumber=10042, cn=changelog
changenumber: 10042
Good March 11, 1998 [Page 5]
INTERNET-DRAFT Change Record Object Class 11 March 1998
targetdn: cn=Bjorn Jensen, ou=Product Development, o=Ace Industry, c=US
changetype: modrdn
newrdn: cn=Bjorn J Jensen
deleteoldrdn: FALSE
Location of the container containing changeLogEntry objects
For LDAPv3 servers, the location of the container which holds
changeLogEntry objects is obtained by reading the "changeLog" attribute
of a server's root DSE. For example, if the container's root is
"cn=changelog", then the root DSE must have an attribute named
"changeLog" with the value "cn=changelog".
The "changelog" attribute is defined as follows:
( 2.16.840.1.113730.3.1.35
NAME 'changelog'
DESC 'the distinguished name of the entry which contains
the set of entries comprising this server's changelog'
EQUALITY distinguishedNameMatch
SYNTAX 'DN'
)
For LDAPv2 servers, the name of the changelog container must be
"cn=changelog".
Differences from previous versions of this document
Differences between draft-ietf-asid-changelog-00.txt and
draft-ietf-asid-changelog-01.txt
1) Fixed a deficiency in the syntax of the changeNumber attribute. The
attribute now has INTEGER syntax, with appropriate matching and
ordering rules defined.
2) Removed unneeded substring matching rules from the changeType and
deleteOldRDN attribute definitions.
3) Made use of MAY, SHOULD, etc. consistent with RFC 2119.
4) Renamed document (now an individual submission).
5) Changed syntax of "changes" attribute from "Binary" to "OctetString".
6) Removed references to X.500 supplier and consumer-initiated
replication.
Good March 11, 1998 [Page 6]
INTERNET-DRAFT Change Record Object Class 11 March 1998
7) Updated references to current drafts/proposed standards documents.
Security Considerations
Servers implementing this scheme MUST NOT allow the "changes"
attribute to be generally readable. The "changes" attribute contains
all modifications made to an entry, and some changes may contain
sensitive data, e.g. passwords.
If a server does allow read access on the "changes: attribute to a
particular bound DN, then that DN should be trusted. For example, two
cooperating servers may exchange the password for some DN which is
granted read access to the "changes" attribute of the changeLog. This
would allow one server to retrieve changes and apply them directly to
its database.
In situations where the "changes" attribute is not readable by a client,
that client may still use the entries in the changeLog to construct a
list of entry DNs which are known to have changed since the last time
the client synchronized. The client may then read each of those entries,
subject to whatever access control is in effect on the server,
and update its local copy of each entry.
Servers implementing this scheme should disallow write access to the
changelog container object and all entries contained within.
Acknowledgements
This material is based in part upon work supported by the National
Science Foundation under Grant No. NCR-9416667.
References
[1] Good, G., "The LDAP Data Interchange Format", INTERNET-DRAFT
draft-good-ldap-ldif-03.txt, Netscape Communications Corp., March 1997,
<URL:ftp://ftp.ietf.org/internet-drafts/draft-good-ldap-ldif-03.txt>
[2] Wahl, M., Howes, T., Kille, S., "Lightweight Directory Access
Protocol (v3)", RFC 2251 Critical Angle, Inc., Netscape Communications Corp.,
ISODE Consortium, July, 1997,
<URL:ftp://ftp.isi.edu/in-notes/rfc2251.txt>
[3] S. Bradner, "Key Words for use in RFCs to Indicate Requirement
Levels", Harvard University, RFC 2119, March 1997,
Good March 11, 1998 [Page 7]
INTERNET-DRAFT Change Record Object Class 11 March 1998
<URL:http://ds.internic.net/rfc/rfc2119.txt>
Author's Address
Gordon Good
Netscape Communications Corp.
501 E. Middlefield Rd.
Mailstop MV068
Mountain View, CA 94043, USA
Phone: +1 415 937-3825
EMail: ggood@netscape.com
This Internet Draft expires October 1st, 1998.
Good March 11, 1998 [Page 8]