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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: June 23, 2008 A. Melnikov 5 Isode Ltd. 6 December 21, 2007 8 GSS-API Internationalization and Domain-Based Service Names and Name 9 Type 10 draft-ietf-kitten-gssapi-domain-based-names-05.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 June 23, 2008. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). 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 IANA is requested to assign a new OID for the new GSS-API name type 131 defined in this document. This OID should have the following prefix: 133 {iso(1) org(3) dod(6) internet(1) security(5) nametypes(6) gss- 134 domain-based(5)} 136 The recommended symbolic name for this GSS-API name type is 137 "GSS_C_NT_DOMAINBASED_SERVICE". 139 4. Query and Display Syntaxes 141 There is a single name syntax for domain-based names. It is 142 expressed using the ABNF [RFC4234]. 144 The syntax is: 146 domain-based-name = 148 service "@" domain "@" hostname 150 hostname = 152 domain 154 domain 156 sub-domain 1*("." sub-domain) 158 sub-domain 160 Let-dig [Ldh-str] 162 Let-dig 164 ALPHA / DIGIT 166 Ldh-str 168 *( ALPHA / DIGIT / "-" ) Let-dig 170 Where is defined in Section 4.1 of [RFC2743]. Other rules 171 not defined above are defined in Appendix B.1 of [RFC4234]. 173 4.1. Examples of domain-based names 175 These examples are not normative: 177 o ldap@somecompany.example@ds1.somecompany.example 179 o nfs@somecompany.example@nfsroot1.somecompany.example 181 The .example top-level domain is used here in accordance with 182 [RFC2606]. 184 5. Internationalization (I18N) considerations 186 We introduce new versions of GSS_Import_name() and GSS_Display_name() 187 to better support Unicode. Additionally we provide for the use of 188 ACE-encoded DNS in the non-internationalized interfaces [RFC3490]. 190 5.1. Importing internationalized names 192 When the input_name_type parameter is the 193 GSS_C_NT_DOMAINBASED_SERVICE OID then GSS_Import_name() 194 implementations and GSS-API mechanisms MUST accept ACE-encoded 195 internationalized domain names in the hostname and domain name slots 196 of the given domain-based name string. 198 Support for non-ASCII internationalized domain names SHOULD be 199 provided through a new function, GSS_Import_name_utf8(), that 200 operates exactly like GSS_Import_name(), except that it MUST accept 201 internationalized domain names both, as UTF-8 strings and as ACE- 202 encoded strings via its input_name_string argument. 204 5.2. Displaying internationalized names 206 Implementations of GSS_Display_name() MUST only output US-ASCII or 207 ACE-encoded internationalized domain names in the hostname and domain 208 name slots of domain-based names (or mechanism names (MN) that 209 conform to the mechanism's form for domain-based names). 211 Support for non-ASCII internationalized domain names SHOULD be 212 provided through a new function, GSS_Display_name_utf8(), that 213 operates exactly like GSS_Display_name(), except that it outputs 214 UTF-8 strings via its name_string output argument. 215 GSS_Display_name_utf8() MUST NOT output ACE-encoded internationalized 216 domain names. 218 6. Application protocol examples 220 The following examples are not normative. They describe how the 221 author envisions two applications' use of domain-based names. 223 6.1. NFSv4 domain-wide namespace root server discovery 225 Work is ongoing to provide a method for constructing domain-wide 226 NFSv4 [RFC3530] filesystem namespaces where there is a single "root" 227 with one or more servers (replicas) and multiple filesystems glued 228 into the namespace through use of "referrals." Clients could then 229 construct a "global" namespace through use of the DNS domain 230 hierarchy. 232 Here clients would always know, from context, when they need to find 233 the root servers for a given DNS domain. Root server discovery would 234 be performed using DNS SRV RR lookups, without using DNSSEC where 235 DNSSEC has not been deployed. 237 When using RPCSEC_GSS [RFC2203] for security NFSv4 clients would then 238 use domain-based names to ensure that that the servers named in the 239 SRV RRs are in fact authorized to be the NFSv4 root servers for the 240 target domain. 242 6.2. LDAP server discovery 244 LDAP clients using the GSS-API through SASL too would benefit from 245 use of domain-based names to protect server discovery through 246 insecure DNS SRV RR lookups, much as described above. 248 Unlike NFSv4 clients, not all LDAP clients may always know from 249 context when they should use domain-based names. That's because 250 existing clients may use host-based naming to authenticate servers 251 discovered through SRV RR lookups. Changing such clients to use 252 domain-based naming when domain-based acceptor credentials have not 253 been deployed to LDAP servers, or when LDAP servers have not been 254 modified to allow use of domain-based naming, would break 255 interoperability. That is, there is a legacy server interoperability 256 issue here. Therefore LDAP clients may require additional 257 configuration at deployment time to enable (or disable) use of 258 domain-based naming. 260 Note: whether SASL [RFC4422] or its GSS-API bridges [RFC4752] 261 [I-D.josefsson-sasl-gs2] require updates in order allow use of 262 domain-based names is not relevant to the theory of how domain-based 263 naming would protect LDAP clients' server discovery. 265 7. Security Considerations 267 Use of GSS-API domain-based names may not be negotiable by some GSS- 268 API mechanisms, and some acceptors may not support GSS-API domain- 269 based names. In such cases initiators are left to fallback on the 270 use of hostbased names, in which case the initiators MUST also verify 271 that the acceptor's hostbased name is authorized to provide the given 272 service for the domain that the initiator had wanted. 274 The above security consideration also applies to all GSS-API 275 initiators who lack support for domain-based service names. 277 8. References 279 8.1. Normative References 281 [RFC1035] Mockapetris, P., "Domain names - implementation and 282 specification", STD 13, RFC 1035, November 1987. 284 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 285 Requirement Levels", BCP 14, RFC 2119, March 1997. 287 [RFC2743] Linn, J., "Generic Security Service Application Program 288 Interface Version 2, Update 1", RFC 2743, January 2000. 290 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for 291 specifying the location of services (DNS SRV)", RFC 2782, 292 February 2000. 294 [RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a 295 SASL Mechanism", RFC 2831, May 2000. 297 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, 298 "Internationalizing Domain Names in Applications (IDNA)", 299 RFC 3490, March 2003. 301 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 302 Specifications: ABNF", RFC 4234, October 2005. 304 8.2. Informative References 306 [I-D.josefsson-sasl-gs2] 307 Josefsson, S., "Using GSS-API Mechanisms in SASL: The GS2 308 Mechanism Family", draft-josefsson-sasl-gs2-00 (work in 309 progress), November 2005. 311 [RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol 312 Specification", RFC 2203, September 1997. 314 [RFC2606] Eastlake, D. and A. Panitz, "Reserved Top Level DNS 315 Names", BCP 32, RFC 2606, June 1999. 317 [RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., 318 Beame, C., Eisler, M., and D. Noveck, "Network File System 319 (NFS) version 4 Protocol", RFC 3530, April 2003. 321 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 322 Rose, "DNS Security Introduction and Requirements", 323 RFC 4033, March 2005. 325 [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and 326 Security Layer (SASL)", RFC 4422, June 2006. 328 [RFC4752] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple 329 Authentication and Security Layer (SASL) Mechanism", 330 RFC 4752, November 2006. 332 Authors' Addresses 334 Nicolas Williams 335 Sun Microsystems 336 5300 Riata Trace Ct 337 Austin, TX 78727 338 US 340 Email: Nicolas.Williams@sun.com 342 Alexey Melnikov 343 Isode Ltd. 344 5 Castle Business Village, 345 36 Station Road 346 Hampton, Middlesex TW12 2BX 347 United Kingdom 349 Email: Alexey.Melnikov@isode.com 351 Full Copyright Statement 353 Copyright (C) The IETF Trust (2007). 355 This document is subject to the rights, licenses and restrictions 356 contained in BCP 78, and except as set forth therein, the authors 357 retain all their rights. 359 This document and the information contained herein are provided on an 360 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 361 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 362 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 363 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 364 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 365 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 367 Intellectual Property 369 The IETF takes no position regarding the validity or scope of any 370 Intellectual Property Rights or other rights that might be claimed to 371 pertain to the implementation or use of the technology described in 372 this document or the extent to which any license under such rights 373 might or might not be available; nor does it represent that it has 374 made any independent effort to identify any such rights. 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