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 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 Howard [Page 1] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 2] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 3] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 4] Internet Draft NIS X.500 schema October 2002 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 ) Howard [Page 5] Internet Draft NIS X.500 schema October 2002 ( 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 Howard [Page 6] Internet Draft NIS X.500 schema October 2002 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 ) Howard [Page 7] Internet Draft NIS X.500 schema October 2002 ( 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 Howard [Page 8] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 9] Internet Draft NIS X.500 schema October 2002 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' Howard [Page 10] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 11] Internet Draft NIS X.500 schema October 2002 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. Howard [Page 12] Internet Draft NIS X.500 schema October 2002 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: Howard [Page 13] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 14] Internet Draft NIS X.500 schema October 2002 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.) Howard [Page 15] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 16] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 17] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 18] Internet Draft NIS X.500 schema October 2002 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 , July 2002. 10. Authors' Address Luke Howard PADL Software Pty. Ltd. PO Box 59 Central Park, Vic 3145 Australia Howard [Page 19] Internet Draft NIS X.500 schema October 2002 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: Howard [Page 20] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 21] Internet Draft NIS X.500 schema October 2002 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)) Howard [Page 22] Internet Draft NIS X.500 schema October 2002 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 Howard [Page 23] Internet Draft NIS X.500 schema October 2002 Howard [Page 24]