Network Working Group Tim Howes INTERNET DRAFT Mark Smith OBSOLETES: RFC 1959 Netscape Communications Corp. March 1997 The LDAP URL Format 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. Howes & Smith [Page 1] INTERNET DRAFT March 1997 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. ::= "://" [ ] "/" [ [ "?" [ ] [ "?" [ ] [ "?" [ ] [ "?" ] ] ] ] ] ::= "ldap" | "ldaps" ::= [ ":" ] ::= a distinguished name string as defined in [1] ::= NULL | | [ "," ] ::= an AttributeDescription string as defined in [3] ::= "base" | "one" | "sub" ::= a filter string as defined in [4] ::= "master" | "slave" The "ldap" and "ldaps" prefixes indicate an entry or entries residing in the LDAP server running on the given at the given . 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 is an LDAP Distinguished Name using the string format described in [1]. It identifies the base object of the LDAP search. The construct is used to indicate which attributes should be returned from the entry or entries. Individual names are as defined for AttributeType in RFC 1777. If the part is omitted, all attributes of the entry or entries should be returned. The 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 is omitted, a scope of "base" is assumed. The is used to specify the search filter to apply to entries within the specified scope during the search. It has the format Howes & Smith [Page 2] INTERNET DRAFT March 1997 specified in [4]. If is omitted, a filter of "(objectClass=*)" is assumed. The 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 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 , , 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: Howes & Smith [Page 3] INTERNET DRAFT March 1997 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 Howes & Smith [Page 4] INTERNET DRAFT March 1997 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 Howes & Smith [Page 5]