rfc3088.txt

来自「RFC 的详细文档！」· 文本 代码 · 共 620 行 · 第 1/2 页

Network Working Group                                        K. Zeilenga
Request for Comments: 3088                           OpenLDAP Foundation
Category: Experimental                                        April 2001


                         OpenLDAP Root Service
                 An experimental LDAP referral service

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   The OpenLDAP Project is operating an experimental LDAP (Lightweight
   Directory Access Protocol) referral service known as the "OpenLDAP
   Root Service".  The automated system generates referrals based upon
   service location information published in DNS SRV RRs (Domain Name
   System location of services resource records).  This document
   describes this service.

1. Background

   LDAP [RFC2251] directories use a hierarchical naming scheme inherited
   from X.500 [X500].  Traditionally, X.500 deployments have used a
   geo-political naming scheme (e.g., CN=Jane
   Doe,OU=Engineering,O=Example,ST=CA,C=US).  However, registration
   infrastructure and location services in many portions of the naming
   hierarchical are inadequate or nonexistent.

   The construction of a global directory requires a robust registration
   infrastructure and location service.  Use of Internet domain-based
   naming [RFC2247] (e.g., UID=jdoe,DC=eng,DC=example,DC=net) allows
   LDAP directory services to leverage the existing DNS [RFC1034]
   registration infrastructure and DNS SRV [RFC2782] resource records
   can be used to locate services [LOCATE].








Zeilenga                      Experimental                      [Page 1]

RFC 3088                 OpenLDAP Root Service                April 2001


1.1.  The Glue

   Most existing LDAP implementations do not support location of
   directory services using DNS SRV resource records.  However, most
   servers support generation of referrals to "superior" server(s).
   This service provides a "root" LDAP service which servers may use as
   their superior referral service.

   Client may also use the service directly to locate services
   associated with an arbitrary Distinguished Name [RFC2253] within the
   domain based hierarchy.

   Notice:
     The mechanisms used by service are experimental.  The descriptions
     provided by this document are not definitive.  Definitive
     mechanisms shall be published in a Standard Track document(s).

2. Generating Referrals based upon DNS SRV RRs

   This service returns referrals generated from DNS SRV resource
   records [RFC2782].

2.1. DN to Domain Name Mapping

   The service maps a DN [RFC2253] to a fully qualified domain name
   using the following algorithm:

       domain = null;
       foreach RDN left-to-right        // [1]

       {
           if not multi-valued RDN and
               RDN.type == domainComponent
           {
               if ( domain == null || domain == "." )
               {   // start
                   domain = "";
               }
               else
               {   // append separator
                   domain .= ".";
               }

               if ( RDN.value == "."  )
               {   // root
                   domain = ".";
               }
               else



Zeilenga                      Experimental                      [Page 2]

RFC 3088                 OpenLDAP Root Service                April 2001


               {   // append domainComponent
                   domain .= RDN.value;
               }
               continue;
           }
           domain = null;
       }

   Examples:

       Distinguished Name              Domain
       -----------------------------   ------------
       DC=example,DC=net               example.net
       UID=jdoe,DC=example,DC=net      example.net
       DC=.                            .            [2]
       DC=example,DC=net,DC=.          .            [3]
       DC=example,DC=.,DC=net          net          [4]
       DC=example.net                  example.net  [5]
       CN=Jane Doe,O=example,C=US      null
       UID=jdoe,DC=example,C=US        null
       DC=example,O=example,DC=net     net
       DC=example+O=example,DC=net     net
       DC=example,C=US+DC=net          null

   Notes:

   0) A later incarnation will use a Standard Track mechanism.

   1) A later incarnation of this service may use a right-to-left
      algorithm.

   2) RFC 2247 does not state how one can map the domain representing
      the root of the domain tree to a DN.  We suggest the root of the
      domain tree be mapped to "DC=." and that this be reversable.

   3) RFC 2247 states that domain "example.net" should be mapped to the
      DN "DC=example,DC=net", not to "DC=example,DC=net,DC=.".  As it is
      not our intent to introduce or support an alternative domain to DN
      mapping, the algorithm ignores domainComponents to the left of
      "DC=.".

   4) RFC 2247 states that domain "example.net" should be mapped to the
      DN "DC=example,DC=net", not to "DC=example,DC=.,DC=net".  As it is
      not our intent to introduce or support an alternative domain to DN
      mapping, the algorithm ignores domainComponents to the left of
      "DC=." and "DC=." itself if further domainComponents are found to
      the right.




Zeilenga                      Experimental                      [Page 3]

RFC 3088                 OpenLDAP Root Service                April 2001


   5) RFC 2247 states that value of an DC attribute type is a domain
      component.  It should not contain multiple domain components.  A
      later incarnation of this service may map this domain to null or
      be coded to return invalid DN error.

   If the domain is null or ".", the service aborts further processing
   and returns noSuchObject.  Later incarnation of this service may
   abort processing if the resulting domain is a top-level domain.

2.2. Locating LDAP services

   The root service locates services associated with a given fully
   qualified domain name by querying the Domain Name System for LDAP SRV
   resource records.  For the domain example.net, the service would do a
   issue a SRV query for the domain "_ldap._tcp.example.net".  A
   successful query will return one or more resource records of the
   form:

     _ldap._tcp.example.net. IN SRV 0 0 389 ldap.example.net.

   If no LDAP SRV resource records are returned or any DNS error occurs,
   the service aborts further processing and returns noSuchObject.
   Later incarnations of this service will better handle transient
   errors.

2.3. Constructing an LDAP Referrals

   For each DNS SRV resource record returned for the domain, a LDAP URL
   [RFC2255] is constructed.  For the above resource record, the URL
   would be:

     ldap://ldap.example.net:389/

   These URLs are then returned in the referral.  The URLs are currently
   returned in resolver order.  That is, the server itself does not make
   use of priority or weight information in the SRV resource records.  A
   later incarnation of this service may.

3. Protocol Operations

   This section describes how the service performs basic LDAP
   operations.  The service supports operations extended through certain
   controls as described in a later section.








Zeilenga                      Experimental                      [Page 4]

RFC 3088                 OpenLDAP Root Service                April 2001


3.1. Basic Operations

   Basic (add, compare, delete, modify, rename, search) operations
   return a referral result if the target (or base) DN can be mapped to
   a set of LDAP URLs as described above.  Otherwise a noSuchObject
   response or other appropriate response is returned.

3.2. Bind Operation

   The service accepts "anonymous" bind specifying version 2 or version
   3 of the protocol.  All other bind requests will return a non-
   successful resultCode.  In particular, clients which submit clear
   text credentials will be sent an unwillingToPerform resultCode with a
   cautionary text regarding providing passwords to strangers.

   As this service is read-only, LDAPv3 authentication [RFC2829] is not
   supported.

3.3. Unbind Operations

   Upon receipt of an unbind request, the server abandons all
   outstanding requests made by client and disconnects.

3.4. Extended Operations

   The service currently does recognize any extended operation.  Later
   incarnations of the service may support Start TLS [RFC2830] and other
   operations.

3.5. Update Operations

   A later incarnation of this service may return unwillingToPerform for
   all update operations as this is an unauthenticated service.

4. Controls

   The service supports the ManageDSAit control.  Unsupported controls
   are serviced per RFC 2251.

4.1. ManageDSAit Control

   The server recognizes and honors the ManageDSAit control [NAMEDREF]
   provided with operations.

   If DNS location information is available for the base DN itself, the
   service will return unwillingToPerform for non-search operations.
   For search operations, an entry will be returned if within scope and
   matches the provided filter.  For example:



Zeilenga                      Experimental                      [Page 5]

RFC 3088                 OpenLDAP Root Service                April 2001


       c: searchRequest {
           base="DC=example,DC=net"
           scope=base
           filter=(objectClass=*)
           ManageDSAit
       }

       s: searchEntry {
           dn: DC=example,DC=net
           objectClass: referral
           objectClass: extensibleObject
           dc: example
           ref: ldap://ldap.example.net:389/
           associatedDomain: example.net
       }
       s: searchResult {
           success
       }

   If DNS location information is available for the DC portion of a
   subordinate entry, the service will return noSuchObject with the
   matchedDN set to the DC portion of the base for search and update
   operations.