Application Working Group L. Howard
INTERNET-DRAFT PADL Software
Expires June 2001 M. Ansari
Sun Microsystems
1 March 2001
Intended Category: Informational
Obsoletes: RFC 2307
An Approach for Using LDAP as a Network Information Service
<draft-howard-rfc2307bis-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
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 docu-
ments as Internet-Drafts.
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Distribution of this document is unlimited.
Abstract
This document describes an experimental mechanism for mapping entities
related to TCP/IP and the UNIX system into X.500 [X500] entries so that
they may be resolved with the Lightweight Directory Access Protocol
[RFC2251]. A set of attribute types and object classes are proposed,
along with specific guidelines for interpreting them.
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The intention is to assist the deployment of LDAP as an organizational
nameservice. No proposed solutions are intended as standards for the
Internet. Rather, it is hoped that a general consensus will emerge as to
the appropriate solution to such problems, leading eventually to the
adoption of standards. The proposed mechanism has already been imple-
mented with some success.
1. Background and Motivation
The UNIX (R) operating system, and its derivatives (specifically, those
which support TCP/IP and conform to the X/Open Single UNIX specification
[XOPEN]) require a means of looking up entities, by matching them
against search criteria or by enumeration. (Other operating systems that
support TCP/IP may provide some means of resolving some of these enti-
ties. This schema is applicable to those environments also.)
These entities include users, groups, IP services (which map names to IP
ports and protocols, and vice versa), IP protocols (which map names to
IP protocol numbers and vice versa), RPCs (which map names to ONC Remote
Procedure Call [RFC1057] numbers and vice versa), NIS netgroups, booting
information (boot parameters and MAC address mappings), filesystem
mounts, IP hosts and networks.
Resolution requests are made through a set of C functions, provided in
the UNIX system's C library. For example, the UNIX system utility "ls",
which enumerates the contents of a filesystem directory, uses the C
library function getpwuid() in order to map user IDs to login names.
Once the request is made, it is resolved using a "nameservice" which is
supported by the client library. The nameservice may be, at its sim-
plest, a collection of files in the local filesystem which are opened
and searched by the C library. Other common nameservices include the
Network Information Service (NIS) and the Domain Name System (DNS). (The
latter is typically used for resolving hosts, services and networks.)
Both these nameservices have the advantage of being distributed and thus
permitting a common set of entities to be shared amongst many clients.
LDAP is a distributed, hierarchical directory service access protocol
which is used to access repositories of users and other network-related
entities. Because LDAP is often not tightly integrated with the host
operating system, information such as users may need to be kept both in
LDAP and in an operating system supported nameservice such as NIS. By
using LDAP as the the primary means of resolving these entities, these
redundancy issues are minimized and the scalability of LDAP can be
exploited. (By comparison, NIS services based on flat files do not have
the scalability or extensibility of LDAP or X.500.)
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The object classes and attributes defined below are suitable for repre-
senting the aforementioned entities in a form compatible with LDAP and
X.500 directory services.
2. General Issues
2.1. Terminology
The key words "MUST", "SHOULD", and "MAY" used in this document are to
be interpreted as described in [RFC2119].
For the purposes of this document, the term "nameservice" refers to a
service, such as NIS or flat files, that is used by the operating system
to resolve entities within a single, local naming context. Contrast this
with a "directory service" such as LDAP, which supports extensible
schema and multiple naming contexts.
The term "NIS-related entities" broadly refers to entities which are
typically resolved using the Network Information Service. (NIS was pre-
viously known as YP.) Deploying LDAP for resolving these entities does
not imply that NIS be used, as a gateway or otherwise. In particular,
the host and network classes are generically applicable, and may be
implemented on any system that wishes to use LDAP or X.500 for host and
network resolution.
The "DUA" (directory user agent) refers to the LDAP client querying
these entities, such as an LDAP to NIS gateway or the C library. The
"client" refers to the application which ultimately makes use of the
information returned by the resolution. It is irrelevant whether the DUA
and the client reside within the same address space. The act of the DUA
making this information to the client is termed "republishing".
To avoid confusion, the term "login name" refers to the user's login
name (being the value of the uid attribute) and the term "user ID"
refers to he user's integer identification number (being the value of
the uidNumber attribute).
The phrases "resolving an entity" and "resolution of entities" refer
respectively to enumerating NIS-related entities of a given type, and
matching them against a given search criterion. One or more entities are
returned as a result of successful "resolutions" (a "match" operation
will only return one entity).
The use of the term UNIX does not confer upon this schema the endorse-
ment of owners of the UNIX trademark. Where necessary, the term "TCP/IP
entity" is used to refer to protocols, services, hosts, and networks,
and the term "UNIX entity" to its complement. (The former category does
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not mandate the host operating system supporting the interfaces required
for resolving UNIX entities.)
The OIDs defined below are derived from iso(1) org(3) dod(6) internet(1)
directory(1) nisSchema(1).
2.2. Attributes
The attributes and classes defined in this document are summarized
below.
The following attributes are defined in this document:
uidNumber
gidNumber
gecos
homeDirectory
loginShell
shadowLastChange
shadowMin
shadowMax
shadowWarning
shadowInactive
shadowExpire
shadowFlag
memberUid
memberNisNetgroup
nisNetgroupTriple
ipServicePort
ipServiceProtocol
ipProtocolNumber
oncRpcNumber
ipHostNumber
ipNetworkNumber
ipNetmaskNumber
macAddress
bootParameter
bootFile
nisMapName
nisMapEntry
nisPublicKey
nisSecretKey
nisDomain
Additionally, some of the attributes defined in [RFC2256] are required.
2.3. Object classes
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The following object classes are defined in this document:
posixAccount
shadowAccount
posixGroup
ipService
ipProtocol
oncRpc
ipHost
ipNetwork
nisNetgroup
nisMap
nisObject
ieee802Device
bootableDevice
nisKeyObject
nisDomainObject
Additionally, some of the classes defined in [RFC2256] are required.
3. Attribute definitions
This section contains attribute definitions to be implemented by DUAs
supporting this schema.
( nisSchema.1.0 NAME 'uidNumber'
DESC 'An integer uniquely identifying a user in an
administrative domain'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.1 NAME 'gidNumber'
DESC 'An integer uniquely identifying a group in an
administrative domain'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.2 NAME 'gecos'
DESC 'The GECOS field; the common name'
EQUALITY caseIgnoreIA5Match
SUBSTRINGS caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( nisSchema.1.3 NAME 'homeDirectory'
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DESC 'The absolute path to the home directory'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( nisSchema.1.4 NAME 'loginShell'
DESC 'The path to the login shell'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( nisSchema.1.5 NAME 'shadowLastChange'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.6 NAME 'shadowMin'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.7 NAME 'shadowMax'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.8 NAME 'shadowWarning'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.9 NAME 'shadowInactive'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.10 NAME 'shadowExpire'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.11 NAME 'shadowFlag'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.12 NAME 'memberUid'
EQUALITY caseExactIA5Match
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SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( nisSchema.1.13 NAME 'memberNisNetgroup'
EQUALITY caseExactIA5Match
SUBSTRINGS caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( nisSchema.1.14 NAME 'nisNetgroupTriple'
DESC 'Netgroup triple'
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( nisSchema.1.15 NAME 'ipServicePort'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.16 NAME 'ipServiceProtocol'
SUP name )
( nisSchema.1.17 NAME 'ipProtocolNumber'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.18 NAME 'oncRpcNumber'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( nisSchema.1.19 NAME 'ipHostNumber'
DESC 'IP address as a dotted decimal, eg. 192.168.1.1,
omitting leading zeros'
SUP name )
( nisSchema.1.20 NAME 'ipNetworkNumber'
DESC 'IP network as a dotted decimal, eg. 192.168,
omitting leading zeros'
SUP name
SINGLE-VALUE )
( nisSchema.1.21 NAME 'ipNetmaskNumber'
DESC 'IP netmask as a dotted decimal, eg. 255.255.255.0,
omitting leading zeros'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( nisSchema.1.22 NAME 'macAddress'
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DESC 'MAC address in maximal, colon separated hex
notation, eg. 00:00:92:90:ee:e2'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( nisSchema.1.23 NAME 'bootParameter'
DESC 'rpc.bootparamd parameter'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( nisSchema.1.24 NAME 'bootFile'
DESC 'Boot image name'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( nisSchema.1.26 NAME 'nisMapName'
SUP name )
( nisSchema.1.27 NAME 'nisMapEntry'
EQUALITY caseExactIA5Match
SUBSTRINGS caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( nisSchema.1.28 NAME 'nisPublicKey'
DESC 'NIS public key'
EQUALITY octetStringMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 )
( nisSchema.1.29 NAME 'nisSecretKey'
DESC 'NIS secret key'
EQUALITY octetStringMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 )
( nisSchema.1.30 NAME 'nisDomain'
DESC 'NIS domain'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26)
4. Class definitions
This section contains class definitions to be implemented by DUAs
supporting the schema.
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Various schema for mail routing and delivery using LDAP directories have
been proposed, and as such this document does not consider schema for
representing mail aliases or distirbution lists.
( nisSchema.2.0 NAME 'posixAccount' SUP top AUXILIARY
DESC 'Abstraction of an account with POSIX attributes'
MUST ( cn $ uid $ uidNumber $ gidNumber $ homeDirectory )
MAY ( authPassword $ userPassword $ loginShell $ gecos $
description ) )
( nisSchema.2.1 NAME 'shadowAccount' SUP top AUXILIARY
DESC 'Additional attributes for shadow passwords'
MUST uid
MAY ( authPassword $ userPassword $ description $
shadowLastChange $ shadowMin $ shadowMax $
shadowWarning $ shadowInactive $
shadowExpire $ shadowFlag ) )
( nisSchema.2.2 NAME 'posixGroup' SUP top AUXILIARY
DESC 'Abstraction of a group of accounts'
MUST gidNumber
MAY ( authPassword $ userPassword $ memberUid $
description ) )
( nisSchema.2.3 NAME 'ipService' SUP top STRUCTURAL
DESC 'Abstraction an Internet Protocol service.
Maps an IP port and protocol (such as tcp or udp)
to one or more names; the distinguished value of
the cn attribute denotes the service's canonical
name'
MUST ( cn $ ipServicePort $ ipServiceProtocol )
MAY description )
( nisSchema.2.4 NAME 'ipProtocol' SUP top STRUCTURAL
DESC 'Abstraction of an IP protocol. Maps a protocol number
to one or more names. The distinguished value of the cn
attribute denotes the protocol's canonical name'
MUST ( cn $ ipProtocolNumber )
MAY description )
( nisSchema.2.5 NAME 'oncRpc' SUP top STRUCTURAL
DESC 'Abstraction of an Open Network Computing (ONC)
[RFC1057] Remote Procedure Call (RPC) binding.
This class maps an ONC RPC number to a name.
The distinguished value of the cn attribute denotes
the RPC service's canonical name'
MUST ( cn $ oncRpcNumber )
MAY description )
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( nisSchema.2.6 NAME 'ipHost' SUP top AUXILIARY
DESC 'Abstraction of a host, an IP device. The distinguished
value of the cn attribute denotes the host's canonical
name. Device SHOULD be used as a structural class'
MUST ( cn $ ipHostNumber )
MAY ( authPassword $ userPassword $ l $ description $ manager ) )
( nisSchema.2.7 NAME 'ipNetwork' SUP top STRUCTURAL
DESC 'Abstraction of a network. The distinguished value of
the cn attribute denotes the network's canonical name'
MUST ipNetworkNumber
MAY ( cn $ ipNetmaskNumber $ l $ description $ manager ) )
( nisSchema.2.8 NAME 'nisNetgroup' SUP top STRUCTURAL
DESC 'Abstraction of a netgroup. May refer to other netgroups'
MUST cn
MAY ( nisNetgroupTriple $ memberNisNetgroup $ description ) )
( nisSchema.2.9 NAME 'nisMap' SUP top STRUCTURAL
DESC 'A generic abstraction of a NIS map'
MUST nisMapName
MAY description )
( nisSchema.2.10 NAME 'nisObject' SUP top STRUCTURAL
DESC 'An entry in a NIS map'
MUST ( cn $ nisMapEntry $ nisMapName )
MAY description )
( nisSchema.2.11 NAME 'ieee802Device' SUP top AUXILIARY
DESC 'A device with a MAC address; device SHOULD be
used as a structural class'
MAY macAddress )
( nisSchema.2.12 NAME 'bootableDevice' SUP top AUXILIARY
DESC 'A device with boot parameters; device SHOULD be
used as a structural class'
MAY ( bootFile $ bootParameter ) )
( nisSchema.2.14 NAME 'nisKeyObject' SUP top AUXILIARY
DESC 'An object with a public and secret key'
MUST ( cn $ nisPublicKey $ nisSecretKey )
MAY ( uidNumber $ description ) )
( nisSchema.2.15 NAME 'nisDomainObject' SUP top AUXILIARY
DESC 'Associates a NIS domain with a naming context'
MUST nisDomain )
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5. Implementation details
5.1. Suggested resolution methods
The preferred means of directing a client application (one using the
shared services of the C library) to use LDAP as its information
source for the functions listed in Appendix B is to modify the source
code to directly query LDAP. As the source to commercial C libraries
and applications is rarely available to the end-user, one could emu-
late a supported nameservice (such as NIS). (This is also an appro-
priate opportunity to perform caching of entries across process
address spaces.) In the case of NIS, reference implementations are
widely available and the RPC interface is well known.
The means by which the operating system is directed to use LDAP is
implementation dependent. For example, some operating systems and C
libraries support end-user extensible resolvers using dynamically load-
able libraries and a nameservice "switch". The means in which the DUA
locates LDAP servers is also implementation dependent.
5.2. Interpreting user and group entries
User and group resolution is initiated by the functions prefixed by
getpw and getgr respectively. The uid attribute contains the user's
login name. The cn attribute, in posixGroup entries, contains the
group's name. This document preserves the use of the uid attribute even
though, being a naming attribute, its syntax is case insensitive. This
may cause a problem with existing deployments where there exist login
names differing only in case. If DUAs support attribute mapping, a dif-
ferent (non-naming) attribute may be used to represent users' login
names.
The account object class provides a convenient structural class for
posixAccount, and SHOULD be used where additional attributes are not
required. For groups with one of more distinguished names, the groupOfU-
niqueNames object class MUST be used as a structural object class. For
groups whose members are only login names, the namedObject [namedObject]
object class MAY be used as a structural object class.
It is suggested that uid and cn are used as the naming attribute for
posixAccount and posixGroup entries, respectively. Group members may
either be login names (values of memberUid) or distinguished names (val-
ues of uniqueMember). In the latter case, the distinguished name must be
mapped to one or more login names by examining the name's RDN or, if it
is not distinguished by uid, performing a base search on the DN with a
filter of "(objectclass=*)". DUAs may wish to cache DN to login name
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mappings. The DUA MAY traverse nested groups.
An account's GECOS field is preferably determined by a value of the
gecos attribute. If no gecos attribute exists, the value of the cn
attribute MUST be used. (The existence of the gecos attribute allows
information embedded in the GECOS field, such as a user's telephone num-
ber, to be returned to the client without overloading the cn attribute.
It also accommodates directories where the common name does not contain
the user's full name.)
An entry of class posixAccount, posixGroup, or shadowAccount without an
authPassword or userPassword attribute MUST NOT be used for authentica-
tion. In this case the client SHOULD be returned a non-matchable pass-
word such as "x". Use of the userPassword attribute to store crypted
passwords is deprecated and may be used only for backwards compatibility
with RFC 2307. New deployments MUST use the authPassword attribute,
defined in [authPassword], instead.
The DUA MUST iterate the values of the authPassword attribute until a
value whose schema is CRYPT is found. The DUA MAY iterate through the
values of the userPassword attribute, using the syntax defined in RFC
2307, until a value whose schema is CRYPT is found. If no conforming
value is found, the client MUST be returned a non-matchable password
such as "x". Authentication using schemes other than CRYPT is, although
advisable, beyond the scope of this document.
Below is an example of an authPassword attribute:
authPassword: CRYPT$X5/DBrWPOQQaI
Below is an example of a (deprecated) userPassword attribute:
userPassword: {CRYPT}X5/DBrWPOQQaI
A DUA MAY utilise the attributes in the shadowAccount class to provide
shadow password service (getspnam() and getspent()). In such cases, the
DUA MUST NOT make use of the userPassword attribute for getpwnam() et
al, and MUST return a non-matchable password (such as "x") to the client
instead.
5.4. Interpreting hosts and networks
The ipHostNumber and ipNetworkNumber attributes are defined in prefer-
ence to dNSRecord (defined in [RFC1279]), in order to simplify the DUA's
role in interpreting entries in the directory. A dNSRecord expresses a
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complete resource record, including time to live and class data, which
is extraneous to this schema.
Additionally, the ipHost and ipNetwork classes permit a host or network
(respectively) and all its aliases to be represented by a single entry
in the directory. This is not necessarily possible if a DNS resource
record is mapped directly to an LDAP entry. Implementations that wish
to use LDAP to master DNS zone information are not precluded from doing
so, and may simply avoid the ipHost and ipNetwork classes.
This document redefines, although not exclusively, the ipNetwork class
defined in [RFC1279], in order to achieve consistent naming with ipHost.
The ipNetworkNumber attribute is also used in the siteContact object
class [ROSE].
The authPassword attribute is included in ipHost such that hosts may be
treated as authentication principals. The treatment of this attribute
and inherent caveats considered in section 5.2 apply here also.
The trailing zeros in a network address MUST be omitted. CIDR-style net-
work addresses (eg. 192.168.1/24) MAY be used.
Hosts with IPv6 addresses MUST be written in their "preferred" form as
defined in section 2.2.1 of [RFC1884], such that all components of the
address are indicated and leading zeros are omitted. This provides a
consistent means of resolving ipHosts by address.
5.5. Interpreting other entities
In general, a one-to-one mapping between entities and LDAP entries is
proposed, in that each entity has exactly one representation in the DIT.
In some cases this is not feasible; for example, a service which is rep-
resented in more than one protocol domain. Consider the following entry:
dn: cn=domain,ou=services,dc=aja,dc=com
objectClass: top
objectClass: ipService
cn: domain
cn: nameserver
ipServicePort: 53
ipServiceProtocol: tcp
ipServiceProtocol: udp
This entry MUST map to the following two (2) services entities:
domain 53/tcp nameserver
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domain 53/udp nameserver
While the above two entities may be represented as separate LDAP enti-
ties, with different distinguished names (such as cn=domain+ipService-
Protocol=tcp, ... and cn=domain+ipServiceProtocol=udp, ...) it is conve-
nient to represent them as a single entry. (If a service is represented
in multiple protocol domains with different ports, then multiple entries
are required; multivalued RDNs may be used to distinguish them.)
With the exception of authPassword and userPassword values, empty values
(consisting of a zero length string) are returned by the DUA to the
client. The DUA MUST reject any entries which do not conform to the
schema (missing mandatory attributes). Non-conforming entries SHOULD be
ignored while enumerating entries.
The nisDomainObject object class is provided to associate a NIS domain
with a naming context. A DUA would retrieve the NIS domain name from a
configuration file and enumerate the naming contexts served by an LDAP
server, searching each naming context for (nisDomain=%s). The first
matching entry that is found may be used as a search base for configura-
tion profile information or for entries themselves. For example, the
following example shows an association between the NIS domain
"nis.aja.com" and the naming context "dc=aja,dc=com":
dn: dc=aja,dc=com
objectClass: top
objectClass: domain
objectClass: nisDomainObject
dc: aja
nisDomain: nis.aja.com
The nisObject object class MAY be used as a generic means of represent-
ing NIS entities. Its use is not encouraged; where support for entities
not described in this schema is desired, an appropriate schema should be
devised. Implementors are strongly advised to support end-user extensi-
ble mappings between NIS entities and object classes. (Where the nisOb-
ject class is used, the nisMapName attribute may be used as a RDN.) The
nisObject class might be used to represent automount information.
5.6. Canonicalizing entries with multi-valued naming attributes
For entities such as hosts, services, networks, protocols, and RPCs,
where there may be one or more aliases, the respective entry's relative
distinguished name SHOULD be used to determine the canonical name. Any
other values for the same attribute are used as aliases. For example,
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the service described in section 5.5 has the canonical name "domain" and
exactly one alias, "nameserver".
The schema in this document generally only defines one attribute per
class which is suitable for distinguishing an entity (excluding any
attributes with integer syntax; it is assumed that entries will be dis-
tinguished on name). Usually, this is the common name (cn) attribute.
This aids the DUA in determining the canonical name of an entity, as it
can examine the value of the relative distinguished name. Aliases are
thus any values of the distinguishing attribute (such as cn) which do
not match the canonical name of the entity.
In the event that a different attribute is used to distinguish the
entry, as may be the case where these object classes are used as auxil-
iary classes, the entry's canonical name may not be present in the RDN.
In this case, the DUA MUST choose one of the non-distinguished values to
represent the entity's canonical name. As the directory server guaran-
tees no ordering of attribute values, it may not be possible to distin-
guish an entry deterministically. This ambiguity SHOULD NOT be resolved
by mapping one directory entry into multiple entities.
6. Implementation focus
Gateways between NIS and LDAP have been developed by PADL Software and
Sun Microsystems. They both support this schema.
An open source implementation of the C library resolution code has been
written and is available from PADL Software. It supports C libraries on
GNU, BSD, AIX, and Solaris operating systems. PADL have also made avail-
able a set of scripts for migrating flat files into a form suitable for
loading into an LDAP server.
7. Security considerations
The entirety of related security considerations are outside the scope of
this document. It is noted that making passwords encrypted with a
widely understood hash function (such as crypt()) available to non-priv-
ileged users is dangerous because it exposes them to dictionary and
brute-force attacks. This is proposed only for compatibility with
existing UNIX system implementations. Sites where security is critical
SHOULD consider using a strong authentication service for user authenti-
cation.
Alternatively, the encrypted password could be made available only to a
subset of privileged DUAs, which would provide "shadow" password service
to client applications. This may be difficult to enforce.
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Internet Draft NIS X.500 schema 1 March 2001
Because the schema represents operating system-level entities, access to
these entities SHOULD be granted on a discretionary basis. (There is
little point in restricting access to data which will be republished
without restriction, however.) It is particularly important that only
administrators can modify entries defined in this schema, with the
exception of allowing a principal to change their password (which may be
done on behalf of the user by a client bound as a superior principal,
such that password restrictions may be enforced). For example, if a user
were allowed to change the value of their uidNumber attribute, they
could subvert security by equivalencing their account with the superuser
account.
A subtree of the DIT which is to be republished by a DUA (such as a NIS
gateway) SHOULD be within the same administrative domain that the repub-
lishing DUA represents. (For example, principals outside an organiza-
tion, while conceivably part of the DIT, should not be considered with
the same degree of authority as those within the organization.)
Finally, care should be exercised with integer attributes of a sensitive
nature (particularly the uidNumber and gidNumber attributes) which con-
tain zero-length values. DUAs MAY treat such values as corresponding to
the "nobody" or "nogroup" user and group, respectively.
8. Acknowledgements
Thanks to Bob Joslin of the Hewlett Packard Company, and to all those
that helped with this document's predecessor, RFC 2307.
UNIX is a registered trademark of The Open Group.
9. References
[RFC1057]
Sun Microsystems, Inc., "RPC: Remote Procedure Call: Protocol Spec-
ification Version 2", RFC 1057, June 1988.
[RFC1279]
S. Kille, "X.500 and Domains", RFC 1279, November 1991.
[RFC1884]
R. Hinden, S. Deering, "IP Version 6 Addressing Architecture", RFC
1884, December 1995.
[RFC2119]
S. Bradner, "Key Words for use in RFCs to Indicate Requirement Lev-
els", RFC 2119, March 1997.
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Internet Draft NIS X.500 schema 1 March 2001
[RFC2251]
M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol
(v3)", RFC 2251, December 1997.
[RFC2252]
M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3): Attribute Syntax Definitions", RFC 2252,
December 1997.
[RFC2254]
T. Howes, "The String Representation of LDAP Search Filters", RFC
2254, December 1997.
[RFC2256]
M. Wahl, "A Summary of the X.500(96) User Schema for use with
LDAPv3", RFC 2256, December 1997.
[ROSE]
M. T. Rose, "The Little Black Book: Mail Bonding with OSI Directory
Services", ISBN 0-13-683210-5, Prentice-Hall, Inc., 1992.
[X500]
"Information Processing Systems - Open Systems Interconnection -
The Directory: Overview of Concepts, Models and Service", ISO/IEC
JTC 1/SC21, International Standard 9594-1, 1988.
[XOPEN]
ISO/IEC 9945-1:1990, Information Technology - Portable Operating
Systems Interface (POSIX) - Part 1: Systems Application Programming
Interface (API) [C Language]
[namedObject]
L. Howard, "A Structural Object Class for Arbitrary Auxiliary
Object Classes", INTERNET-DRAFT <draft-howard-namedObject-00.txt>,
March 2001.
[authPassword]
K. Zeilenga, "LDAP Authentication Password Attribute", INTERNET-
DRAFT <draft-zeilenga-ldap-authpasswd-04.txt>, July 2000.
10. Authors' Address
Luke Howard
PADL Software Pty. Ltd.
PO Box 59
Central Park Vic 3145
Australia
EMail: lukeh@padl.com
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Morteza Ansari
Sun Microsystems, Inc.
901 San Antonio RD MS MPK17-203
Palo Alto, CA 94303
USA
Phone: +1 650 786-6178
EMail: morteza.ansari@sun.com
11. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished to oth-
ers, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and dis-
tributed, in whole or in part, without restriction of any kind, provided
that the above copyright notice and this paragraph are included on all
such copies and derivative works. However, this document itself may not
be modified in any way, such as by removing the copyright notice or ref-
erences to the Internet Society or other Internet organizations, except
as needed for the purpose of developing Internet standards in which case
the procedures for copyrights defined in the Internet Standards process
must be followed, or as required to translate it into languages other
than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FIT-
NESS FOR A PARTICULAR PURPOSE.
A. Example entries
The examples described in this section are provided to illustrate the
schema described in this draft. They are not meant to be exhaustive.
The following entry is an example of the posixAccount class:
dn: uid=lester,ou=people,dc=aja,dc=com
objectClass: top
objectClass: account
objectClass: posixAccount
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uid: lester
cn: Lester the Nightfly
gecos: Lester
uidNumber: 10
gidNumber: 10
loginShell: /bin/csh
authPassword: CRYPT$X5/DBrWPOQQaI
homeDirectory: /home/lester
This corresponds the UNIX system password file entry:
lester:X5/DBrWPOQQaI:10:10:Lester:/home/lester:/bin/sh
The following entry is an example of the ipHost class:
dn: cn=josie.aja.com,ou=hosts,dc=aja,dc=com
objectClass: top
objectClass: device
objectClass: ipHost
objectClass: bootableDevice
objectClass: ieee802Device
cn: josie.aja.com
cn: www.aja.com
ipHostNumber: 10.0.0.1
macAddress: 00:00:92:90:ee:e2
bootFile: mach
bootParameter: root=dan.aja.com:/nfsroot/peg
bootParameter: swap=dan.aja.com:/nfsswap/peg
bootParameter: dump=dan.aja.com:/nfsdump/peg
This entry represents the host canonically josie.aja.com, also known as
www.aja.com. The Ethernet address and four boot parameters are also
specified.
An example of the nisNetgroup class:
dn: cn=nightfly,ou=netgroup,dc=aja,dc=com
objectClass: top
objectClass: nisNetgroup
cn: nightfly
nisNetgroupTriple: (charlemagne,peg,dunes.aja.com)
nisNetgroupTriple: (lester,-,)
memberNisNetgroup: kamakiriad
This entry represents the netgroup nightfly, which contains two triples
(the user charlemagne, the host peg, and the domain dunes.aja.com; and,
the user lester, no host, and any domain) and one netgroup (kamakiriad).
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Finally, an example of the nisObject class:
dn: nisMapName=tracks,dc=dunes,dc=aja,dc=com
objectClass: top
objectClass: nisMap
nisMapName: tracks
dn: cn=Maxine,nisMapName=tracks,dc=dunes,dc=aja,dc=com
objectClass: top
objectClass: nisObject
cn: Maxine
nisMapName: tracks
nisMapEntry: Nightfly$4
This entry represents the NIS map tracks, and a single map entry.
B. Affected library functions
The following functions are typically found in the C libraries of most
UNIX and POSIX compliant systems. An LDAP search filter [RFC2254] which
may be used to satisfy the function call is included alongside each
function name. Parameters are denoted by %s and %d for string and inte-
ger arguments, respectively. Long lines are broken.
getpwnam() (&(objectClass=posixAccount)(uid=%s))
getpwuid() (&(objectClass=posixAccount)(uidNumber=%d))
getpwent() (objectClass=posixAccount)
getspnam() (&(objectClass=shadowAccount)(uid=%s))
getspent() (objectClass=shadowAccount)
getgrnam() (&(objectClass=posixGroup)(cn=%s))
getgrgid() (&(objectClass=posixGroup)(gidNumber=%d))
getgrent() (objectClass=posixGroup)
getservbyname() (&(objectClass=ipService)(cn=%s)
(ipServiceProtocol=%s))
getservbyport() (&(objectClass=ipService)(ipServicePort=%d)
(ipServiceProtocol=%s))
getservent() (objectClass=ipService)
getrpcbyname() (&(objectClass=oncRpc)(cn=%s))
getrpcbynumber() (&(objectClass=oncRpc)(oncRpcNumber=%d))
getrpcent() (objectClass=oncRpc)
getprotobyname() (&(objectClass=ipProtocol)(cn=%s))
getprotobynumber() (&(objectClass=ipProtocol)(ipProtocolNumber=%d))
getprotoent() (objectClass=ipProtocol)
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gethostbyname() (&(objectClass=ipHost)(cn=%s))
gethostbyaddr() (&(objectClass=ipHost)(ipHostNumber=%s))
gethostent() (objectClass=ipHost)
getnetbyname() (&(objectClass=ipNetwork)(cn=%s))
getnetbyaddr() (&(objectClass=ipNetwork)(ipNetworkNumber=%s))
getnetent() (objectClass=ipNetwork)
setnetgrent() (&(objectClass=nisNetgroup)(cn=%s))
getpublickey() (&(objectClass=nisKeyObject)(...))
C. Suggested DIT structure
The cn attribute is typically used to name entities. The ipHostNumber,
ipNetworkNumber, and ipServiceProtocol attributes are also naming
attributes, such that multi-valued RDNs may be used to distinguish
between, for example, different interfaces of a multi-homed host.
The following DIT structure MAY be used for deploying this schema. It
is not required that DC-naming be used, but it is encouraged.
Naming context ObjectClass
============================================================
ou=people,dc=... posixAccount
shadowAcount
ou=group,dc=... posixGroup
ou=services,dc=... ipService
ou=protocols,dc=... ipProtocol
ou=rpc,dc=... oncRpc
ou=hosts,dc=... ipHost
ou=ethers,dc=... ieee802Device
bootableDevice
ou=networks,dc=... ipNetwork
ou=netgroup,dc=... nisNetgroup
nisMapName=...,dc=... nisObject
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