Network Working Group Tim Howes
INTERNET DRAFT Mark Smith
University of Michigan
18 December, 1995
An LDAP URL Format
<draft-ietf-asid-ldap-format-03.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
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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 [1] and
[2]. This document describes a format for an LDAP Uniform Resource
Locator which will allow Internet clients to have direct access to the
LDAP protocol. While LDAP currently is used only as a front end to the
X.500 directory, the URL format described here is general enough to han-
dle the case of stand-alone LDAP servers (i.e., LDAP servers not back-
ended by X.500).
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3. URL Definition
An LDAP URL begins with the protocol prefix "ldap" and is defined by the
following grammar.
<ldapurl> ::= "ldap://" [ <hostport> ] "/" <dn> [ "?" <attributes>
[ "?" <scope> "?" <filter> ] ]
<hostport> ::= <hostname> [ ":" <portnumber> ]
<dn> ::= a string as defined in RFC 1485
<attributes> ::= NULL | <attributelist>
<attributelist> ::= <attributetype>
| <attributetype> [ "," <attributelist> ]
<attributetype> ::= a string as defined in RFC 1777
<scope> ::= "base" | "one" | "sub"
<filter> ::= a string as defined in RFC 1558
The ldap prefix indicates an entry or entries residing in the LDAP
server running on the given <hostname> at the given <portnumber>. The
default port is TCP port 389. The <dn> is an LDAP Distinguished Name
using the string format described in [1], with any URL-illegal charac-
ters (e.g., spaces) escaped using the % method described in RFC 1738.
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 speci-
fied in [4], with any URL-illegal characters escaped using the % method
described in RFC 1738. If <filter> is omitted, a filter of
"(objectClass=*)" is assumed.
Note that if the entry resides in the X.500 namespace, it 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
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can be resolved by contacting any X.500-back-ended LDAP server.
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:
ldap:///o=University%20of%20Michigan,c=US??sub?(cn=Babs%20Jensen)
An LDAP URL referring to all children of the c=GB entry:
ldap://ldap.itd.umich.edu/c=GB?objectClass?one
The objectClass attribute is requested to be returned along with the
entries.
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. The security implications of resolving an LDAP
URL are the same as those of resolving any LDAP query. See the RFC 1777
for more details.
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6. Prototype Implementation Availability
There is a prototype implementation of the specification defined in this
document available. It is an extension to the libwww client library,
provided in both source and binary forms. Also included are binary ver-
sions of the Mosaic WWW client for various platforms. See the following
URL for more details:
ftp://terminator.rs.itd.umich.edu/ldap/url/
7. Bibliography
[1] A String Representation of Distinguished Names. S. Kille, Request
for Comment (RFC) 1779, March 1995.
[2] Lightweight Directory Access Protocol. Wengyik Yeong, Tim Howes,
Steve Kille, Request for Comment (RFC) 1777, March 1995.
[3] The String Representation of Standard Attribute Syntaxes. T.
Howes, S. Kille, W. Yeong, C.J. Robbins; Request for Comment (RFC)
1778, March 1995
[4] A String Representation of LDAP Search Filters. T. Howes; Request
for Comment (RFC) 1558, December 1993
[5] Uniform Resource Locators (URL). T. Berners-Lee, L. Masinter, M.
McCahill; Request for Comment (RFC) 1738, December 1994.
8. Acknowledgements
This material is based upon work supported by the National Science Foun-
dation under Grant No. NCR-9416667.
9. Author's Address
Tim Howes
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.
Howes & Smith [Page 4]
RFC DRAFT December 1995
Ann Arbor, MI 48103-4943
USA
+1 313 764-2277
mcs@umich.edu
This Internet Draft expires June 18, 1996.
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