1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
|
<pre>Network Working Group N. Williams
Request for Comments: 5178 Sun
Category: Standards Track A. Melnikov
Isode Ltd.
May 2008
<span class="h1">Generic Security Service Application Program Interface (GSS-API)</span>
<span class="h1">Internationalization and Domain-Based Service Names and Name Type</span>
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.
<span class="grey">Williams & Melnikov Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
Table of Contents
<a href="#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-2">2</a>. Conventions Used in This Document . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-3">3</a>. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-3.1">3.1</a>. Name Type OID . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-3.2">3.2</a>. Name Type OID and Symbolic Name . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-4">4</a>. Query and Display Syntaxes . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-4.1">4.1</a>. Examples of Domain-Based Names . . . . . . . . . . . . . . <a href="#page-5">5</a>
<a href="#section-5">5</a>. Internationalization (I18N) Considerations . . . . . . . . . . <a href="#page-5">5</a>
<a href="#section-5.1">5.1</a>. Importing Internationalized Names . . . . . . . . . . . . . <a href="#page-5">5</a>
<a href="#section-5.2">5.2</a>. Displaying Internationalized Names . . . . . . . . . . . . <a href="#page-5">5</a>
<a href="#section-6">6</a>. Application Protocol Examples . . . . . . . . . . . . . . . . . <a href="#page-6">6</a>
<a href="#section-6.1">6.1</a>. NFSv4 Domain-Wide Namespace Root Server Discovery . . . . . <a href="#page-6">6</a>
<a href="#section-6.2">6.2</a>. LDAP Server Discovery . . . . . . . . . . . . . . . . . . . <a href="#page-6">6</a>
<a href="#section-7">7</a>. Security Considerations . . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-8">8</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-8.1">8.1</a>. Normative References . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-8.2">8.2</a>. Informative References . . . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<span class="grey">Williams & Melnikov Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
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 [<a href="./rfc1035" title=""Domain names - implementation and specification"">RFC1035</a>] SRV resource records
[<a href="./rfc2782" title=""A DNS RR for specifying the location of services (DNS SRV)"">RFC2782</a>] without using DNSSEC [<a href="./rfc4033" title=""DNS Security Introduction and Requirements"">RFC4033</a>], 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 [<a href="./rfc2743" title=""Generic Security Service Application Program Interface Version 2, Update 1"">RFC2743</a>] 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
[<a href="./rfc2831" title=""Using Digest Authentication as a SASL Mechanism"">RFC2831</a>] describes a similar notion. (See <a href="./rfc2831#section-2.1.2">section 2.1.2 of
[RFC2831]</a> for a description of the "serv-name" field of the digest-
response.)
<span class="grey">Williams & Melnikov Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Conventions Used in This Document</span>
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 [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. IANA Considerations</span>
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Name Type OID</span>
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 [<a href="./rfc5178">RFC5178</a>]
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. Name Type OID and Symbolic Name</span>
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)}
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Query and Display Syntaxes</span>
There is a single name syntax for domain-based names. It is
expressed using the ABNF [<a href="./rfc5234" title=""Augmented BNF for Syntax Specifications: ABNF"">RFC5234</a>].
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 <a href="./rfc2743#section-4.1">Section 4.1 of [RFC2743]</a>. Other rules
not defined above are defined in <a href="./rfc5234#appendix-B.1">Appendix B.1 of [RFC5234]</a>.
<span class="grey">Williams & Melnikov Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>. Examples of Domain-Based Names</span>
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
[<a href="./rfc2606" title=""Reserved Top Level DNS Names"">RFC2606</a>].
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Internationalization (I18N) Considerations</span>
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 [<a href="./rfc3490" title=""Internationalizing Domain Names in Applications (IDNA)"">RFC3490</a>].
<span class="h3"><a class="selflink" id="section-5.1" href="#section-5.1">5.1</a>. Importing Internationalized Names</span>
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.
<span class="h3"><a class="selflink" id="section-5.2" href="#section-5.2">5.2</a>. Displaying Internationalized Names</span>
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.
<span class="grey">Williams & Melnikov Standards Track [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Application Protocol Examples</span>
The following examples are not normative. They describe how the
authors envision two applications' use of domain-based names.
<span class="h3"><a class="selflink" id="section-6.1" href="#section-6.1">6.1</a>. NFSv4 Domain-Wide Namespace Root Server Discovery</span>
Work is ongoing to provide a method for constructing domain-wide
NFSv4 [<a href="./rfc3530" title=""Network File System (NFS) version 4 Protocol"">RFC3530</a>] 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 [<a href="./rfc2203" title=""RPCSEC_GSS Protocol Specification"">RFC2203</a>] 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.
<span class="h3"><a class="selflink" id="section-6.2" href="#section-6.2">6.2</a>. LDAP Server Discovery</span>
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 [<a href="./rfc4422" title=""Simple Authentication and Security Layer (SASL)"">RFC4422</a>] or its GSS-API bridges [<a href="./rfc4752" title=""The Kerberos V5 ("">RFC4752</a>] [<a href="#ref-GS2" title=""Using GSS-API Mechanisms in SASL: The GS2 Mechanism Family"">GS2</a>]
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.
<span class="grey">Williams & Melnikov Standards Track [Page 6]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-7" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Security Considerations</span>
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.
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. References</span>
<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>. Normative References</span>
[<a id="ref-RFC1035">RFC1035</a>] Mockapetris, P., "Domain names - implementation and
specification", STD 13, <a href="./rfc1035">RFC 1035</a>, November 1987.
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.
[<a id="ref-RFC2743">RFC2743</a>] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", <a href="./rfc2743">RFC 2743</a>, January 2000.
[<a id="ref-RFC2782">RFC2782</a>] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", <a href="./rfc2782">RFC 2782</a>,
February 2000.
[<a id="ref-RFC2831">RFC2831</a>] Leach, P. and C. Newman, "Using Digest Authentication as a
SASL Mechanism", <a href="./rfc2831">RFC 2831</a>, May 2000.
[<a id="ref-RFC3490">RFC3490</a>] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
<a href="./rfc3490">RFC 3490</a>, March 2003.
[<a id="ref-RFC5234">RFC5234</a>] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, <a href="./rfc5234">RFC 5234</a>, January 2008.
<span class="grey">Williams & Melnikov Standards Track [Page 7]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-8" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>. Informative References</span>
[<a id="ref-GS2">GS2</a>] Josefsson, S., "Using GSS-API Mechanisms in SASL: The GS2
Mechanism Family", Work in Progress, October 2007.
[<a id="ref-RFC2203">RFC2203</a>] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
Specification", <a href="./rfc2203">RFC 2203</a>, September 1997.
[<a id="ref-RFC2606">RFC2606</a>] Eastlake, D. and A. Panitz, "Reserved Top Level DNS
Names", <a href="https://www.rfc-editor.org/bcp/bcp32">BCP 32</a>, <a href="./rfc2606">RFC 2606</a>, June 1999.
[<a id="ref-RFC3530">RFC3530</a>] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
Beame, C., Eisler, M., and D. Noveck, "Network File System
(NFS) version 4 Protocol", <a href="./rfc3530">RFC 3530</a>, April 2003.
[<a id="ref-RFC4033">RFC4033</a>] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
<a href="./rfc4033">RFC 4033</a>, March 2005.
[<a id="ref-RFC4422">RFC4422</a>] Melnikov, A. and K. Zeilenga, "Simple Authentication and
Security Layer (SASL)", <a href="./rfc4422">RFC 4422</a>, June 2006.
[<a id="ref-RFC4752">RFC4752</a>] Melnikov, A., "The Kerberos V5 ("GSSAPI") Simple
Authentication and Security Layer (SASL) Mechanism",
<a href="./rfc4752">RFC 4752</a>, 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
<span class="grey">Williams & Melnikov Standards Track [Page 8]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-9" ></span>
<span class="grey"><a href="./rfc5178">RFC 5178</a> GSS Domain-Based Names May 2008</span>
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a>, 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 <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and <a href="https://www.rfc-editor.org/bcp/bcp79">BCP 79</a>.
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
<a href="http://www.ietf.org/ipr">http://www.ietf.org/ipr</a>.
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]
</pre>
|
