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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 NETWORK WORKING GROUP N. Williams 3 Internet-Draft Sun 4 Expires: July 27, 2008 A. Melnikov 5 Isode Ltd. 6 January 24, 2008 8 GSS-API Internationalization and Domain-Based Service Names and Name 9 Type 10 draft-ietf-kitten-gssapi-domain-based-names-06.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on July 27, 2008. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2008). 41 Abstract 43 This document describes domainname-based service principal names and 44 the corresponding name type for the Generic Security Service 45 Application Programming Interface (GSS-API). Internationalization of 46 the GSS-API is also covered. 48 Domain-based service names are similar to host-based service names, 49 but using a domain name (not necessarily an Internet domain name) in 50 addition to a hostname. The primary purpose of domain-based names is 51 to provide a measure of protection to applications that utilize 52 insecure service discovery protocols. This is achieved by providing 53 a way to name clustered services after the "domain" which they 54 service, thereby allowing their clients to authorize the service's 55 servers based on authentication of their service names. 57 Table of Contents 59 1. Conventions used in this document . . . . . . . . . . . . . 3 60 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 61 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . 5 62 3.1. Name Type OID and Symbolic Name . . . . . . . . . . . . . . 5 63 4. Query and Display Syntaxes . . . . . . . . . . . . . . . . . 6 64 4.1. Examples of domain-based names . . . . . . . . . . . . . . . 6 65 5. Internationalization (I18N) considerations . . . . . . . . . 7 66 5.1. Importing internationalized names . . . . . . . . . . . . . 7 67 5.2. Displaying internationalized names . . . . . . . . . . . . . 7 68 6. Application protocol examples . . . . . . . . . . . . . . . 8 69 6.1. NFSv4 domain-wide namespace root server discovery . . . . . 8 70 6.2. LDAP server discovery . . . . . . . . . . . . . . . . . . . 8 71 7. Security Considerations . . . . . . . . . . . . . . . . . . 9 72 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 73 8.1. Normative References . . . . . . . . . . . . . . . . . . . . 10 74 8.2. Informative References . . . . . . . . . . . . . . . . . . . 10 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 12 76 Intellectual Property and Copyright Statements . . . . . . . 13 78 1. Conventions used in this document 80 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 82 document are to be interpreted as described in [RFC2119]. 84 2. Introduction 86 Some applications need to discover the names of servers for a 87 specific resource. Some common methods for server discovery are 88 insecure, e.g., queries for DNS [RFC1035] SRV resource records 89 [RFC2782] without using DNSSEC [RFC4033] and subject to attacks 90 whereby a client can be re-directed to incorrect and possibly 91 malicious servers. A client may even be re-directed to a server that 92 has credentials for itself and may thus authenticate itself to the 93 client, and yet it could be incorrect or malicious (because it has 94 been compromised, say). 96 Domain-based names allow for GSS-API [RFC2743] initiator applications 97 (clients) to authorize acceptor principals (servers) to serve the 98 resource for which the client used insecure server discovery without 99 either securing the server discovery method nor requiring an 100 additional protocol for server authorization -- either a discovered 101 server has credentials for authenticating the domain-based service 102 names that it is intended to respond to, or it does not. 103 Availability of valid credentials for authenticating domain-based 104 names embodies the authorization of a given server to a domain-wide 105 service. 107 A domain-based name consists of three required elements: 109 o a service name 111 o a domain name 113 o a hostname 115 The domain name and the hostname should be Domain Name System (DNS) 116 names, though domain-based names could be used in non-DNS 117 environments. Because of the use of DNS names we must also provide 118 for internationalization of the GSS-API. 120 Note that domain-based naming isn't new. According to a report to 121 the KITTEN WG mailing list there exists at least one implementation 122 of LDAP which uses domain-based service naming, and the DIGEST-MD5 123 HTTP/SASL mechanism [RFC2831] describes a similar notion (see section 124 2.1.2, description of the "serv-name" field of the digest-response). 126 3. IANA Considerations 128 3.1. Name Type OID and Symbolic Name 130 This document creates a new GSS-API name-type, with a symbol name of 131 "GSS_C_NT_DOMAINBASED_SERVICE" and this OID: 133 {iso(1) org(3) dod(6) internet(1) security(5) nametypes(6) gss- 134 domain-based(5)} 136 allocated manually with RFC2743 as the authoritative "registry" -- 137 there is no IANA registry for GSS-API name types at this time. 139 Therefore there are no IANA considerations in this document. 141 4. Query and Display Syntaxes 143 There is a single name syntax for domain-based names. It is 144 expressed using the ABNF [RFC4234]. 146 The syntax is: 148 domain-based-name = 150 service "@" domain "@" hostname 152 hostname = 154 domain 156 domain = 158 sub-domain 1*("." sub-domain) 160 sub-domain = 162 Let-dig [Ldh-str] 164 Let-dig = 166 ALPHA / DIGIT 168 Ldh-str = 170 *( ALPHA / DIGIT / "-" ) Let-dig 172 Where is defined in Section 4.1 of [RFC2743]. Other rules 173 not defined above are defined in Appendix B.1 of [RFC4234]. 175 4.1. Examples of domain-based names 177 These examples are not normative: 179 o ldap@somecompany.example@ds1.somecompany.example 181 o nfs@somecompany.example@nfsroot1.somecompany.example 183 The .example top-level domain is used here in accordance with 184 [RFC2606]. 186 5. Internationalization (I18N) considerations 188 We introduce new versions of GSS_Import_name() and GSS_Display_name() 189 to better support Unicode. Additionally we provide for the use of 190 ACE-encoded DNS in the non-internationalized interfaces [RFC3490]. 192 5.1. Importing internationalized names 194 When the input_name_type parameter is the 195 GSS_C_NT_DOMAINBASED_SERVICE OID then GSS_Import_name() 196 implementations and GSS-API mechanisms MUST accept ACE-encoded 197 internationalized domain names in the hostname and domain name slots 198 of the given domain-based name string. 200 Support for non-ASCII internationalized domain names SHOULD also be 201 provided through a new function, GSS_Import_name_utf8(), that 202 operates exactly like GSS_Import_name() (with the same input and 203 output parameters and behaviour), except that it MUST accept 204 internationalized domain names both, as UTF-8 strings and as ACE- 205 encoded strings via its input_name_string argument. 207 5.2. Displaying internationalized names 209 Implementations of GSS_Display_name() MUST only output US-ASCII or 210 ACE-encoded internationalized domain names in the hostname and domain 211 name slots of domain-based names (or mechanism names (MN) that 212 conform to the mechanism's form for domain-based names). 214 Support for non-ASCII internationalized domain names SHOULD also be 215 provided through a new function, GSS_Display_name_utf8(), that 216 operates exactly like GSS_Display_name() (with the same input and 217 output parameters and behaviour), except that it outputs UTF-8 218 strings via its name_string output argument. GSS_Display_name_utf8() 219 MUST NOT output ACE-encoded internationalized domain names. 221 6. Application protocol examples 223 The following examples are not normative. They describe how the 224 author envisions two applications' use of domain-based names. 226 6.1. NFSv4 domain-wide namespace root server discovery 228 Work is ongoing to provide a method for constructing domain-wide 229 NFSv4 [RFC3530] filesystem namespaces where there is a single "root" 230 with one or more servers (replicas) and multiple filesystems glued 231 into the namespace through use of "referrals." Clients could then 232 construct a "global" namespace through use of the DNS domain 233 hierarchy. 235 Here clients would always know, from context, when they need to find 236 the root servers for a given DNS domain. Root server discovery would 237 be performed using DNS SRV RR lookups, without using DNSSEC where 238 DNSSEC has not been deployed. 240 When using RPCSEC_GSS [RFC2203] for security NFSv4 clients would then 241 use domain-based names to ensure that that the servers named in the 242 SRV RRs are in fact authorized to be the NFSv4 root servers for the 243 target domain. 245 6.2. LDAP server discovery 247 LDAP clients using the GSS-API through SASL too would benefit from 248 use of domain-based names to protect server discovery through 249 insecure DNS SRV RR lookups, much as described above. 251 Unlike NFSv4 clients, not all LDAP clients may always know from 252 context when they should use domain-based names. That's because 253 existing clients may use host-based naming to authenticate servers 254 discovered through SRV RR lookups. Changing such clients to use 255 domain-based naming when domain-based acceptor credentials have not 256 been deployed to LDAP servers, or when LDAP servers have not been 257 modified to allow use of domain-based naming, would break 258 interoperability. That is, there is a legacy server interoperability 259 issue here. Therefore LDAP clients may require additional 260 configuration at deployment time to enable (or disable) use of 261 domain-based naming. 263 Note: whether SASL [RFC4422] or its GSS-API bridges [RFC4752] 264 [I-D.josefsson-sasl-gs2] require updates in order allow use of 265 domain-based names is not relevant to the theory of how domain-based 266 naming would protect LDAP clients' server discovery. 268 7. Security Considerations 270 Use of GSS-API domain-based names may not be negotiable by some GSS- 271 API mechanisms, and some acceptors may not support GSS-API domain- 272 based names. In such cases initiators are left to fallback on the 273 use of hostbased names, in which case the initiators MUST also verify 274 that the acceptor's hostbased name is authorized to provide the given 275 service for the domain that the initiator had wanted. 277 The above security consideration also applies to all GSS-API 278 initiators who lack support for domain-based service names. 280 8. References 282 8.1. Normative References 284 [RFC1035] Mockapetris, P., "Domain names - implementation and 285 specification", STD 13, RFC 1035, November 1987. 287 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 288 Requirement Levels", BCP 14, RFC 2119, March 1997. 290 [RFC2743] Linn, J., "Generic Security Service Application Program 291 Interface Version 2, Update 1", RFC 2743, January 2000. 293 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for 294 specifying the location of services (DNS SRV)", RFC 2782, 295 February 2000. 297 [RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a 298 SASL Mechanism", RFC 2831, May 2000. 300 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, 301 "Internationalizing Domain Names in Applications (IDNA)", 302 RFC 3490, March 2003. 304 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 305 Specifications: ABNF", RFC 4234, October 2005. 307 8.2. Informative References 309 [I-D.josefsson-sasl-gs2] 310 Josefsson, S., "Using GSS-API Mechanisms in SASL: The GS2 311 Mechanism Family", draft-josefsson-sasl-gs2-00 (work in 312 progress), November 2005. 314 [RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol 315 Specification", RFC 2203, September 1997. 317 [RFC2606] Eastlake, D. and A. Panitz, "Reserved Top Level DNS 318 Names", BCP 32, RFC 2606, June 1999. 320 [RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., 321 Beame, C., Eisler, M., and D. Noveck, "Network File System 322 (NFS) version 4 Protocol", RFC 3530, April 2003. 324 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 325 Rose, "DNS Security Introduction and Requirements", 326 RFC 4033, March 2005. 328 [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and 329 Security Layer (SASL)", RFC 4422, June 2006. 331 [RFC4752] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple 332 Authentication and Security Layer (SASL) Mechanism", 333 RFC 4752, November 2006. 335 Authors' Addresses 337 Nicolas Williams 338 Sun Microsystems 339 5300 Riata Trace Ct 340 Austin, TX 78727 341 US 343 Email: Nicolas.Williams@sun.com 345 Alexey Melnikov 346 Isode Ltd. 347 5 Castle Business Village, 348 36 Station Road 349 Hampton, Middlesex TW12 2BX 350 United Kingdom 352 Email: Alexey.Melnikov@isode.com 354 Full Copyright Statement 356 Copyright (C) The IETF Trust (2008). 358 This document is subject to the rights, licenses and restrictions 359 contained in BCP 78, and except as set forth therein, the authors 360 retain all their rights. 362 This document and the information contained herein are provided on an 363 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 364 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 365 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 366 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 367 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 368 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 370 Intellectual Property 372 The IETF takes no position regarding the validity or scope of any 373 Intellectual Property Rights or other rights that might be claimed to 374 pertain to the implementation or use of the technology described in 375 this document or the extent to which any license under such rights 376 might or might not be available; nor does it represent that it has 377 made any independent effort to identify any such rights. 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