Network Working Group Tim Howes
INTERNET DRAFT Mark Smith
OBSOLETES: RFC 1959 Netscape Communications Corp.
March 1997
The LDAP URL Format
<draft-ietf-asid-ldapv3-url-00.txt>
1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working docu-
ments 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).
2. Abstract
LDAP is the Lightweight Directory Access Protocol, defined in [2] and
[3]. This document describes a format for an LDAP Uniform Resource
Locator. The format describes an LDAP search operation to perform to
retrieve information from an LDAP directory. This document replaces RFC
1959. It updates the LDAP URL format for version 3 of LDAP and defines a
way to indicate whether the URL references a master or slave server.
This document also defines a second URL scheme prefix for LDAP running
over the secure sockets layer protocol.
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3. URL Definition
An LDAP URL begins with the protocol prefix "ldap" (or the prefix
"ldaps" for LDAP over SSL) and is defined by the following grammar.
<ldapurl> ::= <scheme> "://" [ <hostport> ] "/"
[ <dn> [ "?" [ <attributes> ] [ "?" [ <scope> ]
[ "?" [ <filter> ] [ "?" <masterorslave> ] ] ] ] ]
<scheme> ::= "ldap" | "ldaps"
<hostport> ::= <hostname> [ ":" <portnumber> ]
<dn> ::= a distinguished name string as defined in [1]
<attributes> ::= NULL
| <attributedesc>
| <attributedesc> [ "," <attributes> ]
<attributedesc> ::= an AttributeDescription string as defined in [3]
<scope> ::= "base" | "one" | "sub"
<filter> ::= a filter string as defined in [4]
<masterorslave> ::= "master" | "slave"
The "ldap" and "ldaps" prefixes indicate an entry or entries residing in
the LDAP server running on the given <hostname> at the given <port-
number>. For regular LDAP servers, the default port is TCP port 389.
For LDAP servers running over secure sockets layer transport [6], the
default port is 636.
The <dn> is an LDAP Distinguished Name using the string format described
in [1]. It identifies the base object of the LDAP search.
The <attributes> construct is used to indicate which attributes should
be returned from the entry or entries. Individual <attributetype> names
are as defined for AttributeType in RFC 1777. If the <attributes> part
is omitted, all attributes of the entry or entries should be returned.
The <scope> construct is used to specify the scope of the search to per-
form in the given LDAP server. The allowable scopes are "base" for a
base object search, "one" for a one-level search, or "sub" for a subtree
search. If <scope> is omitted, a scope of "base" is assumed.
The <filter> is used to specify the search filter to apply to entries
within the specified scope during the search. It has the format
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specified in [4]. If <filter> is omitted, a filter of "(objectClass=*)"
is assumed.
The <masterorslave> construct is optionally used to indicate whether the
LDAP URL refers to a master LDAP server (i.e., one able to update the
data referenced) or a slave LDAP server (i.e., one unable to update the
data referenced).
Note that if the entry or entries reside in the X.500 namespace, they
should be reachable from any LDAP server that is providing front-end
access to the X.500 directory. If the <hostport> part of the URL is
missing, the URL can be resolved by contacting any X.500-back-ended LDAP
server.
Note that any any URL-illegal characters (e.g., spaces) occurring inside
a <dn>, <filter>, or other element of an LDAP URL must be escaped using
the % method described in RFC 1738.
4. Examples
The following are some example LDAP URLs using the format defined above.
An LDAP URL referring to the University of Michigan entry, available
from any X.500-capable LDAP server:
ldap:///o=University%20of%20Michigan,c=US
An LDAP URL referring to the University of Michigan entry in a particu-
lar ldap server:
ldap://ldap.itd.umich.edu/o=University%20of%20Michigan,c=US
This URL corresponds to a base object search of the "o=University of
Michigan, c=US" entry using a filter of (objectclass=*), requesting all
attributes.
An LDAP URL referring to only the postalAddress attribute of the Univer-
sity of Michigan entry:
ldap://ldap.itd.umich.edu/o=University%20of%20Michigan,c=US?postalAddress
The corresponding LDAP search operation is the same as in the previous
example, except that only the postalAddress attribute is requested.
An LDAP URL referring to the set of entries found by querying any
X.500-capable LDAP server and doing a subtree search of the University
of Michigan for any entry with a common name of "Babs Jensen", retriev-
ing all attributes:
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ldap:///o=University%20of%20Michigan,c=US??sub?(cn=Babs%20Jensen)
A secure LDAP URL referring to the master server containing all children
of the c=GB entry:
ldaps://ldap.itd.umich.edu/c=GB?objectClass?one??master
The objectClass attribute is requested to be returned along with the
entries, and the default filter of "(objectclass=*)" is used.
5. Security Considerations
The LDAP URL format does not provide a way to specify credentials to use
when resolving the URL. Therefore, it is expected that such requests
will be unauthenticated, unless some out-of-band mechanism is used.
The LDAP URL format allows the specification of an arbitrary LDAP search
operation to be performed when evaluating the LDAP URL. Following an
LDAP URL may cause unexpected results, for example, the retrieval of
large amounts of data, the initiation of a long-lived search, etc. The
security implications of resolving an LDAP URL are the same as those of
resolving an LDAP search query.
6. Bibliography
[1] Lightweight Directory Access Protocol (v3): UTF-8 String Represen-
tation of Distinguished Names. M. Wahl, S. Kille, draft-ietf-
asid-ldapv3-dn-02.txt, March 1997.
[2] Lightweight Directory Access Protocol (v3). M. Wahl, T. Howes, S.
Kille, draft-ietf-asid-ldapv3-protocol-04.txt, March 1997.
[3] Lightweight Directory Access Protocol (v3): Attribute Syntax Defin-
itions. M. Wahl, A. Coulbeck, T. Howes, S. Kille, draft-ietf-
asid-ldapv3-attributes-04.txt, March 1997.
[4] A String Representation of LDAP Search Filters. T. Howes, draft-
ietf-asid-ldapv3-filter.00.txt, March 1997.
[5] Uniform Resource Locators (URL). T. Berners-Lee, L. Masinter, M.
McCahill, Request for Comment (RFC) 1738, December 1994.
[6] The SSL Protocol Version 3.0. A. Freier, P. Karlton, P. Kocher,
draft-ietf-tls-ssl-version3-00.txt, November 1996.
7. Author's Address
Tim Howes
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University of Michigan
ITD Research Systems
535 W William St.
Ann Arbor, MI 48103-4943
USA
+1 313 747-4454
tim@umich.edu
Mark Smith
University of Michigan
ITD Research Systems
535 W William St.
Ann Arbor, MI 48103-4943
USA
+1 313 764-2277
mcs@umich.edu
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