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
|
<pre>Internet Engineering Task Force (IETF) M. Kucherawy
Request for Comments: 6212 Cloudmark, Inc.
Category: Standards Track April 2011
ISSN: 2070-1721
<span class="h1">Authentication-Results Registration for Vouch by Reference Results</span>
Abstract
This memo updates the registry of properties in Authentication-
Results: message header fields to allow relaying of the results of a
Vouch By Reference query.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in <a href="./rfc5741#section-2">Section 2 of RFC 5741</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="http://www.rfc-editor.org/info/rfc6212">http://www.rfc-editor.org/info/rfc6212</a>.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
<span class="grey">Kucherawy Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc6212">RFC 6212</a> Auth-Results VBR Registration April 2011</span>
Table of Contents
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-2">2</a>
<a href="#section-2">2</a>. Keywords ........................................................<a href="#page-2">2</a>
<a href="#section-3">3</a>. Discussion ......................................................<a href="#page-2">2</a>
<a href="#section-4">4</a>. Definition ......................................................<a href="#page-3">3</a>
<a href="#section-5">5</a>. IANA Considerations .............................................<a href="#page-4">4</a>
<a href="#section-6">6</a>. Security Considerations .........................................<a href="#page-5">5</a>
<a href="#section-7">7</a>. References ......................................................<a href="#page-5">5</a>
<a href="#section-7.1">7.1</a>. Normative References .......................................<a href="#page-5">5</a>
<a href="#section-7.2">7.2</a>. Informative References .....................................<a href="#page-5">5</a>
<a href="#appendix-A">Appendix A</a>. Authentication-Results Examples .......................<a href="#page-6">6</a>
<a href="#appendix-A.1">A.1</a>. VBR Results ................................................<a href="#page-6">6</a>
<a href="#appendix-B">Appendix B</a>. Acknowledgements ......................................<a href="#page-7">7</a>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
[<a id="ref-AUTHRES">AUTHRES</a>] defined a new header field for electronic mail messages
that presents the results of a message authentication effort in a
machine-readable format. In the interim, a proposal for rudimentary
domain-level reputation assessment, called Vouch By Reference, [<a href="#ref-VBR" title=""Vouch By Reference"">VBR</a>]
was published and is now beginning to see popular use.
This memo thus registers an additional reporting property allowing a
VBR result to be relayed as an annotation in a message header.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Keywords</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="#ref-KEYWORDS" title=""Key words for use in RFCs to Indicate Requirement Levels"">KEYWORDS</a>].
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Discussion</span>
Vouch By Reference [<a href="#ref-VBR" title=""Vouch By Reference"">VBR</a>] introduced a mechanism by which a message
receiver can query a "vouching" service to determine whether or not a
trusted third party is willing to state that mail from a particular
source can be considered legitimate. When this assessment is done at
an inbound border mail gateway, it would be useful to relay the
result of that assessment to internal mail entities such as filters
or user agents.
Reactions to the information contained in an Authentication-Results
header field that contains VBR (or any) results are not specified
here, as they are entirely a matter of local policy at the receiver.
<span class="grey">Kucherawy Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc6212">RFC 6212</a> Auth-Results VBR Registration April 2011</span>
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Definition</span>
This memo adds to the "Email Authentication Methods" registry,
created by IANA upon publication of [<a href="#ref-AUTHRES" title=""Message Header Field for Indicating Message Authentication Status"">AUTHRES</a>], the following:
o The method "vbr"; and
o Associated with that method, the properties (reporting items)
"header.md" and "header.mv".
If "header.md" is present, its value MUST be the DNS domain name
about which a VBR query was made. If "header.mv" is present, its
value MUST be the DNS domain name that was queried as the potential
voucher for the "header.md" domain.
If the VBR query was made based on the content of a "VBR-Info" header
field present on an incoming message, "header.md" is typically taken
from the "md" tag of the "VBR-Info" header field, and "header.mv" is
typically one of the values of the "mv" tag in the "VBR-Info" header
field on that message. However, [<a href="#ref-VBR" title=""Vouch By Reference"">VBR</a>] permits a different mechanism
for selection of the subject domain and/or list of vouchers, ignoring
those present in any "VBR-Info" header field the message might have
included. A server could even conduct a VBR query when no "VBR-Info"
field was present, based on locally configured policy options. Where
such mechanisms are applied, the verifying server MAY generate an
Authentication-Results field to relay the results of the VBR query.
This memo also adds to the "Email Authentication Result Names"
registry the following result codes and definitions:
none: No valid VBR-Info header was found in the message, or a domain
name to be queried could not be determined.
pass: A VBR query was completed, and the vouching service queried
gave a positive response.
fail: A VBR query was completed, and the vouching service queried
did not give a positive response, or the message contained
multiple VBR-Info header fields with different "mc" values
(see [<a href="#ref-VBR" title=""Vouch By Reference"">VBR</a>]).
temperror: A VBR query was attempted but could not be completed due
to some error that is likely transient in nature, such as a
temporary DNS error. A later attempt may produce a final result.
<span class="grey">Kucherawy Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc6212">RFC 6212</a> Auth-Results VBR Registration April 2011</span>
permerror: A VBR query was attempted but could not be completed due
to some error that is likely not transient in nature, such as a
permanent DNS error. A later attempt is unlikely to produce a
final result.
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. IANA Considerations</span>
Per [<a href="#ref-IANA" title="">IANA</a>], the following items have been added to the "Email
Authentication Methods" registry:
+------------+----------+--------+----------------+-----------------+
| Method | Defined | ptype | property | value |
+------------+----------+--------+----------------+-----------------+
| vbr | <a href="./rfc6212">RFC 6212</a> | header | md | DNS domain name |
| | | | | used as the |
| | | | | subject of a |
| | | | | VBR query |
+------------+----------+--------+----------------+-----------------+
| vbr | <a href="./rfc6212">RFC 6212</a> | header | mv | DNS domain name |
| | | | | of the entity |
| | | | | acting as |
| | | | | the voucher |
+------------+----------+--------+----------------+-----------------+
Also, the following items have been added to the "Email
Authentication Result Names" registry:
+-----------+--------------+------------+---------+-----------------+
| Code | Existing/New | Defined In | Method | Meaning |
+-----------+--------------+------------+---------+-----------------+
| none | existing | <a href="./rfc5451">RFC 5451</a> | vbr | <a href="#section-4">Section 4</a> of |
| | | | (added) | <a href="./rfc6212">RFC 6212</a> |
+-----------+--------------+------------+---------+-----------------+
| pass | existing | <a href="./rfc5451">RFC 5451</a> | vbr | <a href="#section-4">Section 4</a> of |
| | | | (added) | <a href="./rfc6212">RFC 6212</a> |
+-----------+--------------+------------+---------+-----------------+
| fail | existing | <a href="./rfc5451">RFC 5451</a> | vbr | <a href="#section-4">Section 4</a> of |
| | | | (added) | <a href="./rfc6212">RFC 6212</a> |
+-----------+--------------+------------+---------+-----------------+
| temperror | existing | <a href="./rfc5451">RFC 5451</a> | vbr | <a href="#section-4">Section 4</a> of |
| | | | (added) | <a href="./rfc6212">RFC 6212</a> |
+-----------+--------------+------------+---------+-----------------+
| permerror | existing | <a href="./rfc5451">RFC 5451</a> | vbr | <a href="#section-4">Section 4</a> of |
| | | | (added) | <a href="./rfc6212">RFC 6212</a> |
+-----------+--------------+------------+---------+-----------------+
<span class="grey">Kucherawy Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc6212">RFC 6212</a> Auth-Results VBR Registration April 2011</span>
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Security Considerations</span>
This memo creates a mechanism for relaying [<a href="#ref-VBR" title=""Vouch By Reference"">VBR</a>] results using the
structure already defined by [<a href="#ref-AUTHRES" title=""Message Header Field for Indicating Message Authentication Status"">AUTHRES</a>]. The Security Considerations
sections of those documents should be consulted.
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. References</span>
<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a>. Normative References</span>
[<a id="ref-AUTHRES">AUTHRES</a>] Kucherawy, M., "Message Header Field for Indicating
Message Authentication Status", <a href="./rfc5451">RFC 5451</a>, April 2009.
[<a id="ref-KEYWORDS">KEYWORDS</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-VBR">VBR</a>] Hoffman, P., Levine, J., and A. Hathcock, "Vouch By
Reference", <a href="./rfc5518">RFC 5518</a>, April 2009.
<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a>. Informative References</span>
[<a id="ref-IANA">IANA</a>] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", <a href="https://www.rfc-editor.org/bcp/bcp26">BCP 26</a>, <a href="./rfc5226">RFC 5226</a>,
May 2008.
<span class="grey">Kucherawy Standards Track [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc6212">RFC 6212</a> Auth-Results VBR Registration April 2011</span>
<span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>. Authentication-Results Examples</span>
This section presents an example of the use of this new header field
to indicate VBR results.
<span class="h3"><a class="selflink" id="appendix-A.1" href="#appendix-A.1">A.1</a>. VBR Results</span>
A message that triggered a VBR query, returning a result:
Authentication-Results: mail-router.example.net;
dkim=pass (good signature) header.d=newyork.example.com
header.b=oINEO8hg;
vbr=pass (voucher.example.net)
header.md=newyork.example.com
header.mv=voucher.example.org
Received: from newyork.example.com
(newyork.example.com [192.0.2.250])
by mail-router.example.net (8.11.6/8.11.6)
for <recipient@example.net>
with ESMTP id i7PK0sH7021929;
Fri, Feb 15 2002 17:19:22 -0800
DKIM-Signature: v=1; a=rsa-sha256; s=rashani;
d=newyork.example.com;
t=1188964191; c=relaxed/simple;
h=From:Date:To:VBR-Info:Message-Id:Subject;
bh=sEu28nfs9fuZGD/pSr7ANysbY3jtdaQ3Xv9xPQtS0m7=;
b=oINEO8hgn/gnunsg ... 9n9ODSNFSDij3=
From: sender@newyork.example.com
Date: Fri, Feb 15 2002 16:54:30 -0800
To: meetings@example.net
VBR-Info: md=newyork.example.com; mc=list;
mv=voucher.example.org
Message-Id: <12345.abc@newyork.example.com>
Subject: here's a sample
Example 1: Header Field Reporting Results from a VBR Query
Here we see an example of a message that was signed using DomainKeys
Identified Mail (DKIM) and that also included a VBR-Info header
field. On receipt, it is found that the "md=" field in the latter
and the "d=" field in the former matched, and also that the DKIM
signature verified, so a VBR query was performed. The vouching
service, voucher.example.org, indicated that the sender can be
trusted, so a "pass" result is included in the Authentication-Results
field affixed prior to delivery.
<span class="grey">Kucherawy Standards Track [Page 6]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-7" ></span>
<span class="grey"><a href="./rfc6212">RFC 6212</a> Auth-Results VBR Registration April 2011</span>
<span class="h2"><a class="selflink" id="appendix-B" href="#appendix-B">Appendix B</a>. Acknowledgements</span>
The author wishes to acknowledge the following for their review and
constructive criticism of this proposal: JD Falk, John Levine, and
Alessandro Vesely.
Author's Address
Murray S. Kucherawy
Cloudmark, Inc.
128 King St., 2nd Floor
San Francisco, CA 94107
US
Phone: +1 415 946 3800
EMail: msk@cloudmark.com
Kucherawy Standards Track [Page 7]
</pre>
|
