GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5178

Network Working Group N. Williams Request for Comments: 5178 Sun Category: Standards Track A. Melnikov

                                                            Isode Ltd.
                                                              May 2008
  Generic Security Service Application Program Interface (GSS-API)
 Internationalization and Domain-Based Service Names and Name Type

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 This document describes domain-name-based service principal names and
 the corresponding name type for the Generic Security Service
 Application Programming Interface (GSS-API).  Internationalization of
 the GSS-API is also covered.
 Domain-based service names are similar to host-based service names,
 but using a domain name (not necessarily an Internet domain name) in
 addition to a hostname.  The primary purpose of domain-based names is
 to provide a measure of protection to applications that utilize
 insecure service discovery protocols.  This is achieved by providing
 a way to name clustered services after the "domain" which they
 service, thereby allowing their clients to authorize the service's
 servers based on authentication of their service names.

Williams & Melnikov Standards Track [Page 1] RFC 5178 GSS Domain-Based Names May 2008

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
 2.  Conventions Used in This Document . . . . . . . . . . . . . . . 4
 3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   3.1.  Name Type OID . . . . . . . . . . . . . . . . . . . . . . . 4
   3.2.  Name Type OID and Symbolic Name . . . . . . . . . . . . . . 4
 4.  Query and Display Syntaxes  . . . . . . . . . . . . . . . . . . 4
   4.1.  Examples of Domain-Based Names  . . . . . . . . . . . . . . 5
 5.  Internationalization (I18N) Considerations  . . . . . . . . . . 5
   5.1.  Importing Internationalized Names . . . . . . . . . . . . . 5
   5.2.  Displaying Internationalized Names  . . . . . . . . . . . . 5
 6.  Application Protocol Examples . . . . . . . . . . . . . . . . . 6
   6.1.  NFSv4 Domain-Wide Namespace Root Server Discovery . . . . . 6
   6.2.  LDAP Server Discovery . . . . . . . . . . . . . . . . . . . 6
 7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
 8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
   8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
   8.2.  Informative References  . . . . . . . . . . . . . . . . . . 8

Williams & Melnikov Standards Track [Page 2] RFC 5178 GSS Domain-Based Names May 2008

1. Introduction

 Some applications need to discover the names of servers for a
 specific resource.  Some common methods for server discovery are
 insecure, e.g., queries for DNS [RFC1035] SRV resource records
 [RFC2782] without using DNSSEC [RFC4033], and are subject to attacks
 whereby a client can be re-directed to incorrect and possibly
 malicious servers.  A client may even be re-directed to a server that
 has credentials for itself and thus may authenticate itself to the
 client, and yet it could be incorrect or malicious (because it has
 been compromised, say).
 Domain-based names allow for GSS-API [RFC2743] initiator applications
 (clients) to authorize acceptor principals (servers) to serve the
 resource for which the client used insecure server discovery without
 either securing the server discovery method or requiring an
 additional protocol for server authorization.  That is, either a
 discovered server has credentials for authenticating the domain-based
 service names that it is intended to respond to, or it does not.
 Availability of valid credentials for authenticating domain-based
 names embodies the authorization of a given server to a domain-wide
 service.
 A domain-based name consists of three required elements:
 o  a service name
 o  a domain name
 o  a hostname
 The domain name and the hostname should be Domain Name System (DNS)
 names, though domain-based names could be used in non-DNS
 environments.  Because of the use of DNS names we must also provide
 for internationalization of the GSS-API.
 Note that domain-based naming isn't new.  According to a report to
 the KITTEN WG mailing list, there exists at least one implementation
 of LDAP which uses domain-based service naming, and the DIGEST-MD5
 HTTP / Simple Authentication and Security Layer (SASL) mechanism
 [RFC2831] describes a similar notion.  (See section 2.1.2 of
 [RFC2831] for a description of the "serv-name" field of the digest-
 response.)

Williams & Melnikov Standards Track [Page 3] RFC 5178 GSS Domain-Based Names May 2008

2. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

3. IANA Considerations

3.1. Name Type OID

 The IANA has recorded the following new name-type OID in IANA's "SMI
 Security for Name System Designators Codes (nametypes)" registry:
 5 gss-domain-based-services [RFC5178]

3.2. Name Type OID and Symbolic Name

 This document creates a new GSS-API name-type, with a symbolic name
 of "GSS_C_NT_DOMAINBASED_SERVICE" and this OID:
 {iso(1) org(3) dod(6) internet(1) security(5) nametypes(6) gss-
 domain-based(5)}

4. Query and Display Syntaxes

 There is a single name syntax for domain-based names.  It is
 expressed using the ABNF [RFC5234].
 The syntax is:
       domain-based-name = service "@" domain "@" hostname
       hostname          = domain
       domain            = sub-domain 1*("." sub-domain)
       sub-domain        = Let-dig [Ldh-str]
       Let-dig           = ALPHA / DIGIT
       Ldh-str           = *( ALPHA / DIGIT / "-" ) Let-dig
 Where <service> is defined in Section 4.1 of [RFC2743].  Other rules
 not defined above are defined in Appendix B.1 of [RFC5234].

Williams & Melnikov Standards Track [Page 4] RFC 5178 GSS Domain-Based Names May 2008

4.1. Examples of Domain-Based Names

 These examples are not normative:
 o  ldap@somecompany.example@ds1.somecompany.example
 o  nfs@somecompany.example@nfsroot1.somecompany.example
 The .example top-level domain is used here in accordance with
 [RFC2606].

5. Internationalization (I18N) Considerations

 We introduce new versions of GSS_Import_name() and GSS_Display_name()
 to better support Unicode.  Additionally, we provide for the use of
 ASCII Compatible Encoding (ACE)-encoded DNS in the non-
 internationalized interfaces [RFC3490].

5.1. Importing Internationalized Names

 When the input_name_type parameter is the
 GSS_C_NT_DOMAINBASED_SERVICE OID, then GSS_Import_name()
 implementations and GSS-API mechanisms MUST accept ACE-encoded
 internationalized domain names in the hostname and domain name slots
 of the given domain-based name string.
 Support for non-ASCII internationalized domain names SHOULD also be
 provided through a new function, GSS_Import_name_utf8(), that
 operates exactly like GSS_Import_name() (with the same input and
 output parameters and behavior), except that it MUST accept
 internationalized domain names both as UTF-8 strings and as ACE-
 encoded strings via its input_name_string argument.

5.2. Displaying Internationalized Names

 Implementations of GSS_Display_name() MUST only output US-ASCII or
 ACE-encoded internationalized domain names in the hostname and domain
 name slots of domain-based names (or mechanism names (MN) that
 conform to the mechanism's form for domain-based names).
 Support for non-ASCII internationalized domain names SHOULD also be
 provided through a new function, GSS_Display_name_utf8(), that
 operates exactly like GSS_Display_name() (with the same input and
 output parameters and behavior), except that it outputs UTF-8 strings
 via its name_string output argument.  GSS_Display_name_utf8() MUST
 NOT output ACE-encoded internationalized domain names.

Williams & Melnikov Standards Track [Page 5] RFC 5178 GSS Domain-Based Names May 2008

6. Application Protocol Examples

 The following examples are not normative.  They describe how the
 authors envision two applications' use of domain-based names.

6.1. NFSv4 Domain-Wide Namespace Root Server Discovery

 Work is ongoing to provide a method for constructing domain-wide
 NFSv4 [RFC3530] filesystem namespaces where there is a single "root"
 with one or more servers (replicas) and multiple filesystems glued
 into the namespace through use of "referrals".  Clients could then
 construct a "global" namespace through use of the DNS domain
 hierarchy.
 Here, clients would always know, from context, when they need to find
 the root servers for a given DNS domain.  Root server discovery would
 be performed using DNS SRV RR lookups, without using DNSSEC where
 DNSSEC has not been deployed.
 When using RPCSEC_GSS [RFC2203] for security, NFSv4 clients would use
 domain-based names to ensure that the servers named in the SRV RRs
 are in fact authorized to be the NFSv4 root servers for the target
 domain.

6.2. LDAP Server Discovery

 LDAP clients using the GSS-API through SASL would also benefit from
 use of domain-based names to protect server discovery through
 insecure DNS SRV RR lookups, much as described above.
 Unlike NFSv4 clients, not all LDAP clients always know from context
 when they should use domain-based names.  That's because existing
 clients may use host-based naming to authenticate servers discovered
 through SRV RR lookups.  Changing such clients to use domain-based
 naming when domain-based acceptor credentials have not been deployed
 to LDAP servers, or when LDAP servers have not been modified to allow
 use of domain-based naming, would break interoperability.  That is,
 there is a legacy server interoperability issue here.  Therefore,
 LDAP clients may require additional configuration at deployment time
 to enable (or disable) use of domain-based naming.
 Note: whether SASL [RFC4422] or its GSS-API bridges [RFC4752] [GS2]
 require updates in order allow use of domain-based names is not
 relevant to the theory of how domain-based naming would protect LDAP
 clients' server discovery.

Williams & Melnikov Standards Track [Page 6] RFC 5178 GSS Domain-Based Names May 2008

7. Security Considerations

 Use of GSS-API domain-based names may not be negotiable by some GSS-
 API mechanisms, and some acceptors may not support GSS-API domain-
 based names.  In such cases, the initiators are left to fall back on
 the use of host-based names, so the initiators MUST also verify that
 the acceptor's host-based name is authorized to provide the given
 service for the domain that the initiator had wanted.
 The above security consideration also applies to all GSS-API
 initiators who lack support for domain-based service names.
 Note that, as with all service names, the mere existence of a domain-
 based service name conveys meaningful information that may be used by
 initiators for making authorization decisions; therefore,
 administrators of distributed authentication services should be aware
 of the significance of the service names for which they create
 acceptor credentials.

8. References

8.1. Normative References

 [RFC1035]  Mockapetris, P., "Domain names - implementation and
            specification", STD 13, RFC 1035, November 1987.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2743]  Linn, J., "Generic Security Service Application Program
            Interface Version 2, Update 1", RFC 2743, January 2000.
 [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
            specifying the location of services (DNS SRV)", RFC 2782,
            February 2000.
 [RFC2831]  Leach, P. and C. Newman, "Using Digest Authentication as a
            SASL Mechanism", RFC 2831, May 2000.
 [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
            "Internationalizing Domain Names in Applications (IDNA)",
            RFC 3490, March 2003.
 [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
            Specifications: ABNF", STD 68, RFC 5234, January 2008.

Williams & Melnikov Standards Track [Page 7] RFC 5178 GSS Domain-Based Names May 2008

8.2. Informative References

 [GS2]      Josefsson, S., "Using GSS-API Mechanisms in SASL: The GS2
            Mechanism Family", Work in Progress, October 2007.
 [RFC2203]  Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
            Specification", RFC 2203, September 1997.
 [RFC2606]  Eastlake, D. and A. Panitz, "Reserved Top Level DNS
            Names", BCP 32, RFC 2606, June 1999.
 [RFC3530]  Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
            Beame, C., Eisler, M., and D. Noveck, "Network File System
            (NFS) version 4 Protocol", RFC 3530, April 2003.
 [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
            Rose, "DNS Security Introduction and Requirements",
            RFC 4033, March 2005.
 [RFC4422]  Melnikov, A. and K. Zeilenga, "Simple Authentication and
            Security Layer (SASL)", RFC 4422, June 2006.
 [RFC4752]  Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple
            Authentication and Security Layer (SASL) Mechanism",
            RFC 4752, November 2006.

Authors' Addresses

 Nicolas Williams
 Sun Microsystems
 5300 Riata Trace Ct.
 Austin, TX  78727
 US
 EMail: Nicolas.Williams@sun.com
 Alexey Melnikov
 Isode Ltd.
 5 Castle Business Village,
 36 Station Road
 Hampton, Middlesex  TW12 2BX
 United Kingdom
 EMail: Alexey.Melnikov@isode.com

Williams & Melnikov Standards Track [Page 8] RFC 5178 GSS Domain-Based Names May 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Williams & Melnikov Standards Track [Page 9]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5178.txt · Last modified: 2008/05/12 20:51 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki