Application Working Group L. Howard
INTERNET-DRAFT PADL Software
Expires April 2003 M. Ansari
Sun Microsystems
27 October 2002
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 subject to all provisions
of Section 10 of RFC2026.
This document is an Internet-Draft. Internet-Drafts are working
documents 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 working documents 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 docu-
ments at any time. It is inappropriate to use Internet- Drafts as
reference material or to cite them other than as "work in pro-
gress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Abstract
This document describes a mechanism for mapping entities related to
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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 pro-
posed, along with specific guidelines for interpreting them.
The intention is to assist the deployment of LDAP as an organiza-
tional 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, lead-
ing eventually to the adoption of standards. The proposed mechanism
has already been implemented 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 entities. 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 util-
ity "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 simplest, 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 per-
mitting a common set of entities to be shared amongst many clients.
LDAP is a distributed, hierarchical directory service access proto-
col 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
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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 com-
parison, NIS services based on flat files do not have the scalabil-
ity or extensibility of LDAP or X.500.)
The object classes and attributes defined below are suitable for
representing 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 sup-
ports 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 previously known as YP.) Deploying LDAP for resolving these
entities does not imply that NIS be used, as a gateway or other-
wise. 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
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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
endorsement 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 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) inter-
net(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
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nisPublicKey
nisSecretKey
nisDomain
automountMapName
automountKey
automountInformation
Additionally, some of the attributes defined in [RFC2256] and
[RFC3112] are required.
2.3 Object classes
The following object classes are defined in this document:
posixAccount
shadowAccount
posixGroup
ipService
ipProtocol
oncRpc
ipHost
ipNetwork
nisNetgroup
nisMap
nisObject
ieee802Device
bootableDevice
nisKeyObject
nisDomainObject
automountMap
automount
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.
( 1.3.6.1.1.1.1.0 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 )
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( 1.3.6.1.1.1.1.1 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 )
( 1.3.6.1.1.1.1.2 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 )
( 1.3.6.1.1.1.1.3 NAME 'homeDirectory'
DESC 'The absolute path to the home directory'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( 1.3.6.1.1.1.1.4 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 )
( 1.3.6.1.1.1.1.5 NAME 'shadowLastChange'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.6 NAME 'shadowMin'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.7 NAME 'shadowMax'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.8 NAME 'shadowWarning'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.9 NAME 'shadowInactive'
EQUALITY integerMatch
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SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.10 NAME 'shadowExpire'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.11 NAME 'shadowFlag'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.12 NAME 'memberUid'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( 1.3.6.1.1.1.1.13 NAME 'memberNisNetgroup'
EQUALITY caseExactIA5Match
SUBSTRINGS caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( 1.3.6.1.1.1.1.14 NAME 'nisNetgroupTriple'
DESC 'Netgroup triple'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( 1.3.6.1.1.1.1.15 NAME 'ipServicePort'
DESC 'Service port number'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.16 NAME 'ipServiceProtocol'
DESC 'Service protocol name'
SUP name )
( 1.3.6.1.1.1.1.17 NAME 'ipProtocolNumber'
DESC 'IP protocol number'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( 1.3.6.1.1.1.1.18 NAME 'oncRpcNumber'
DESC 'ONC RPC number'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
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( 1.3.6.1.1.1.1.19 NAME 'ipHostNumber'
DESC 'IPv4 addresses as a dotted decimal omitting leading
zeros or IPv6 addresses as defined in RFC2373'
SUP name )
( 1.3.6.1.1.1.1.20 NAME 'ipNetworkNumber'
DESC 'IP network as a dotted decimal, eg. 192.168,
omitting leading zeros'
SUP name
SINGLE-VALUE )
( 1.3.6.1.1.1.1.21 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 )
( 1.3.6.1.1.1.1.22 NAME 'macAddress'
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 )
( 1.3.6.1.1.1.1.23 NAME 'bootParameter'
DESC 'rpc.bootparamd parameter'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( 1.3.6.1.1.1.1.24 NAME 'bootFile'
DESC 'Boot image name'
EQUALITY caseExactIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( 1.3.6.1.1.1.1.26 NAME 'nisMapName'
DESC 'Name of a A generic NIS map'
SUP name )
( 1.3.6.1.1.1.1.27 NAME 'nisMapEntry'
DESC 'A generic NIS entry'
EQUALITY caseExactIA5Match
SUBSTRINGS caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( 1.3.6.1.1.1.1.28 NAME 'nisPublicKey'
DESC 'NIS public key'
EQUALITY octetStringMatch
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SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 SINGLE-VALUE )
( 1.3.6.1.1.1.1.29 NAME 'nisSecretKey'
DESC 'NIS secret key'
EQUALITY octetStringMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 SINGLE-VALUE )
( 1.3.6.1.1.1.1.30 NAME 'nisDomain'
DESC 'NIS domain'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26)
( 1.3.6.1.1.1.1.31 NAME 'automountMapName'
DESC 'automount Map Name'
EQUALITY caseExactIA5Match
SUBSTR caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )
( 1.3.6.1.1.1.1.32 NAME 'automountKey'
DESC 'Automount Key value'
EQUALITY caseExactIA5Match
SUBSTR caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )
( 1.3.6.1.1.1.1.33 NAME 'automountInformation'
DESC 'Automount information'
EQUALITY caseExactIA5Match
SUBSTR caseExactIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )
4. Class definitions
This section contains class definitions to be implemented by DUAs
supporting the schema.
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 distribution lists.
( 1.3.6.1.1.1.2.0 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 ) )
( 1.3.6.1.1.1.2.1 NAME 'shadowAccount' SUP top AUXILIARY
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DESC 'Additional attributes for shadow passwords'
MUST uid
MAY ( authPassword $ userPassword $ description $
shadowLastChange $ shadowMin $ shadowMax $
shadowWarning $ shadowInactive $
shadowExpire $ shadowFlag ) )
( 1.3.6.1.1.1.2.2 NAME 'posixGroup' SUP top AUXILIARY
DESC 'Abstraction of a group of accounts'
MUST gidNumber
MAY ( authPassword $ userPassword $ memberUid $
description ) )
( 1.3.6.1.1.1.2.3 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 )
( 1.3.6.1.1.1.2.4 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 )
( 1.3.6.1.1.1.2.5 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 )
( 1.3.6.1.1.1.2.6 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 ) )
( 1.3.6.1.1.1.2.7 NAME 'ipNetwork' SUP top STRUCTURAL
DESC 'Abstraction of a network. The distinguished value of
the cn attribute denotes the network's canonical name'
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MUST ipNetworkNumber
MAY ( cn $ ipNetmaskNumber $ l $ description $ manager ) )
( 1.3.6.1.1.1.2.8 NAME 'nisNetgroup' SUP top STRUCTURAL
DESC 'Abstraction of a netgroup. May refer to other netgroups'
MUST cn
MAY ( nisNetgroupTriple $ memberNisNetgroup $ description ) )
( 1.3.6.1.1.1.2.9 NAME 'nisMap' SUP top STRUCTURAL
DESC 'A generic abstraction of a NIS map'
MUST nisMapName
MAY description )
( 1.3.6.1.1.1.2.10 NAME 'nisObject' SUP top STRUCTURAL
DESC 'An entry in a NIS map'
MUST ( cn $ nisMapEntry $ nisMapName )
MAY description )
( 1.3.6.1.1.1.2.11 NAME 'ieee802Device' SUP top AUXILIARY
DESC 'A device with a MAC address; device SHOULD be
used as a structural class'
MAY macAddress )
( 1.3.6.1.1.1.2.12 NAME 'bootableDevice' SUP top AUXILIARY
DESC 'A device with boot parameters; device SHOULD be
used as a structural class'
MAY ( bootFile $ bootParameter ) )
( 1.3.6.1.1.1.2.14 NAME 'nisKeyObject' SUP top AUXILIARY
DESC 'An object with a public and secret key'
MUST ( cn $ nisPublicKey $ nisSecretKey )
MAY ( uidNumber $ description ) )
( 1.3.6.1.1.1.2.15 NAME 'nisDomainObject' SUP top AUXILIARY
DESC 'Associates a NIS domain with a naming context'
MUST nisDomain )
( 1.3.6.1.1.1.2.16 NAME 'automountMap' SUP top STRUCTURAL
MUST ( automountMapName )
MAY description )
( 1.3.6.1.1.1.2.17 NAME 'automount' SUP top STRUCTURAL
DESC 'Automount information'
MUST ( automountKey $ automountInformation )
MAY description )
5. Implementation details
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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 informa-
tion 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 emulate a supported nameservice (such as NIS). (This is also
an appropriate opportunity to perform caching of entries across
process address spaces.) In the case of NIS, reference implementa-
tions 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
loadable 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 insensi-
tive. This may cause a problem with existing deployments where
there exist login names differing only in case. If DUAs support
attribute mapping, a different (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
groupOfUniqueNames object class MUST be used as a structural object
class. For groups whose members are only login names, the namedOb-
ject [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 dis-
tinguished names (values 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 map-
pings. The DUA MAY traverse nested groups.
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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 number, 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 authentication. In this case the client SHOULD be returned a
non-matchable password such as "x".
If userPassword is used, its values MUST be represented by follow-
ing syntax:
passwordvalue = schemeprefix encryptedpasswd
schemeprefix = "{" scheme "}"
scheme = "crypt" / "md5" / "sha" / "ssha" / altscheme
altscheme = "x-" keystring
encryptedpasswd = encrypted password
The encrypted password contains of a plaintext key hashed using the
algorithm scheme. If the schema is "sha", the encrypted password
is the base64 encoding of the SHA-1 digest of the plaintext pass-
word.
userPassword values which do not adhere to this syntax MUST NOT be
used for authentication. The DUA MUST iterate through the values of
the attribute until a value matching the above syntax is found.
Only if encryptedpassword is an empty string does the user have no
password. DUAs are not required to consider encryption schemes
which the client will not recognize; in most cases, it may be suf-
ficient to consider only "crypt".
DUA MAY use the authPassword attribute instead of userPassword,
defined in [RFC3112]. The DUA MUST iterate the values of the auth-
Password attribute until a value whose scheme is CRYPT is found.
The DUA MAY iterate through the values of the userPassword attri-
bute, using the syntax defined in RFC 2307, until a value whose
scheme 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 advis-
able, beyond the scope of this document.
Below is an example of an authPassword attribute:
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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 pro-
vide 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
preference to dNSRecord (defined in [RFC1279]), in order to sim-
plify the DUA's role in interpreting entries in the directory. A
dNSRecord expresses a 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. Imple-
mentations 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 and userPassword attributes are included in ipHost
such that hosts may be treated as authentication principals. The
treatment of these attribute and inherent caveats considered in
section 5.2 apply here also.
The trailing zeros in a network address MUST be omitted. CIDR-style
network addresses (eg. 192.168.1/24) MAY be used.
Leading zeros MUST be removed from all components of an IPv6
address string as defined by [RFC2373], section 2.2, item 1. The
IPv6 address string MUST be further normalized by following the
"::" syntax as defined in section 2.2, item 2. In addition, "::"
MUST be used to replace the longest string of zero bits. If there
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are two or more longest strings of zero bits, then the first string
MUST be replaced. In addition, the syntax defined by [RFC2373],
section 2.2, item 3 MUST NOT be used. IPv4 addresses MUST be
represented by the IPv4 dotted decimal string syntax.
For example the following address:
1080:0000:0:0:08:800:200C:417A
FF01:0:0:0:0:0:0:0101
0:0:0:0:0:0:0:0001
0:0:0:0:0:0:0:0
MUST be normalized as:
1080::8:800:200C:417A
FF01::101
0::1
::
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 represented 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
domain 53/udp nameserver
While the above two entities may be represented as separate LDAP
entities, with different distinguished names (such as
cn=domain+ipServiceProtocol=tcp, ... and
cn=domain+ipServiceProtocol=udp, ...) it is convenient 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.)
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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 configuration 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
representing NIS entities. Its use is not encouraged; where support
for entities not described in this schema is desired, an appropri-
ate schema should be devised. Implementors are strongly advised to
support end-user extensible mappings between NIS entities and
object classes. (Where the nisObject 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, 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 distinguished 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
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distinguished name. Aliases are thus any values of the distinguish-
ing 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
auxiliary 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 guarantees no ordering of attribute values, it
may not be possible to distinguish 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 available 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-privileged users is dangerous because it exposes them to
dictionary and brute-force attacks. This is proposed only for com-
patibility with existing UNIX system implementations. Sites where
security is critical SHOULD consider using a strong authentication
service for user authentication.
Alternatively, the encrypted password could be made available only
to a subset of privileged DUAs, which would provide "shadow" pass-
word service to client applications. This may be difficult to
enforce.
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 particu-
larly important that only administrators can modify entries defined
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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 restric-
tions 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 republishing DUA represents. (For example, principals outside
an organization, 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 sen-
sitive nature (particularly the uidNumber and gidNumber attributes)
which contain zero-length values. DUAs MAY treat such values as
corresponding to the "nobody" or "nogroup" user and group, respec-
tively.
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
Specification Version 2", RFC 1057, June 1988.
[RFC1279]
S. Kille, "X.500 and Domains", RFC 1279, November 1991.
[RFC2373]
R. Hinden, S. Deering, "IP Version 6 Addressing Architecture",
RFC 2373, July 1998.
[RFC2119]
S. Bradner, "Key Words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[RFC2251]
M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
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Protocol (v3)", RFC 2251, December 1997.
[RFC2252]
M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Direc-
tory 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.
[RFC3112]
K. Zeilenga, "LDAP Authentication Password Schema", RFC 3112,
May 2001.
[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 Operat-
ing 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-
01.txt>, July 2002.
10. Authors' Address
Luke Howard
PADL Software Pty. Ltd.
PO Box 59
Central Park, Vic 3145
Australia
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EMail: lukeh@padl.com
Morteza Ansari
Sun Microsystems, Inc.
17 Network Circle, UMPK17-203
Menlo Park, CA 94205
USA
Phone: +1 650 786-6178
EMail: morteza.ansari@sun.com
11. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain
it or assist in its implementation may be prepared, copied, pub-
lished and distributed, in whole or in part, without restriction of
any kind, provided that the above copyright notice and this para-
graph are included on all such copies and derivative works. How-
ever, this document itself may not be modified in any way, such as
by removing the copyright notice or references to the Internet
Society or other Internet organizations, except as needed for the
purpose of developing Internet standards in which case the pro-
cedures 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 FITNESS 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:
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dn: uid=lester,ou=people,dc=aja,dc=com
objectClass: top
objectClass: account
objectClass: posixAccount
uid: lester
cn: Lester the Nightfly
gecos: Lester
uidNumber: 10
gidNumber: 10
loginShell: /bin/csh
userPassword: {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
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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).
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 integer 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))
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getrpcbynumber() (&(objectClass=oncRpc)(oncRpcNumber=%d))
getrpcent() (objectClass=oncRpc)
getprotobyname() (&(objectClass=ipProtocol)(cn=%s))
getprotobynumber() (&(objectClass=ipProtocol)(ipProtocolNumber=%d))
getprotoent() (objectClass=ipProtocol)
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 ipHost-
Number, ipNetworkNumber, and ipServiceProtocol attributes are also
naming attributes, such that multi-valued RDNs may be used to dis-
tinguish 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
automountMapName=...,dc=... automountMap
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