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Versions: 00 01 02 03 04 RFC 6212

Individual submission                                       M. Kucherawy
Internet-Draft                                           Cloudmark, Inc.
Intended status: Standards Track                         January 1, 2011
Expires: July 5, 2011


   Authentication-Results Registration For Vouch By Reference Results
                     draft-kucherawy-authres-vbr-02

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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on July 5, 2011.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Keywords  . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Definition  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Appendix A.  Authentication-Results Examples  . . . . . . . . . . . 6
     A.1.  VBR Results . . . . . . . . . . . . . . . . . . . . . . . . 7
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . . . 7





































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1.  Introduction

   [AUTHRES] 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 called Vouch By Reference [VBR] was published
   and is now beginning to see popular use.

   Fortunately, [AUTHRES] created IANA registries of reporting
   properties, enabling an easy remedy for this problem.  This memo thus
   registers an additional reporting property allowing a VBR result to
   be relayed as an annotation in a message header.

2.  Keywords

   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 [KEYWORDS].

3.  Discussion

   Vouch By Reference [VBR] 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.

4.  Definition

   This memo adds to the "Email Authentication Method Name Registry",
   created by IANA upon publication of [AUTHRES], 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.  This is typically taken from the
   "md" tag of the "VBR-Info" header field.  ([VBR] describes the
   methods for selecting the construction and execution of that query.)

   If "header.mv" is present, its value MUST be the DNS domain that was
   queried as the potential voucher for the "header.md" domain.  This is
   typically one of the values of the "mv" tag in the "VBR-Info" header
   field on the message being evaluated, although a local list of



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   vouchers may be used in place of that value as described in [VBR].

   Where the VBR-Info header field was not present on a message but a
   mail server decides to conduct a VBR query anyway, the server MAY
   still generate an Authentication-Results field to relay the results
   of the VBR query.  In this instance, the "header.md" value MUST be
   the domain name that was evaluated as the sending domain using VBR,
   and the "header.mv" value MUST be the domain name that was used as
   the voucher.

   This memo also adds to the "Email Authentication Results Name
   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.

   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.

   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.

5.  IANA Considerations

   Per [IANA-CONSIDERATIONS], the following item is added to the "Email
   Authentication Method Name Registry":















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   +------------+----------+--------+----------------+-----------------+
   |   Method   | Defined  | ptype  | property       | value           |
   +------------+----------+--------+----------------+-----------------+
   |    vbr     | RFC5518  | header | md             | DNS domain name |
   |            |          |        |                | used as the     |
   |            |          |        |                | subject of a    |
   |            |          |        |                | VBR query       |
   +------------+----------+--------+----------------+-----------------+
   |    vbr     | RFC5518  | header | mv             | DNS domain name |
   |            |          |        |                | of the entity   |
   |            |          |        |                | acting as       |
   |            |          |        |                | the voucher     |
   +------------+----------+--------+----------------+-----------------+

   Also, the following item is added to the "Email Authentication Method
   Results Registry":

   +-----------+--------------+------------+---------+-----------------+
   |   Code    | Existing/New | Defined In | Method  | Meaning         |
   +-----------+--------------+------------+---------+-----------------+
   | none      | existing     |  RFC5451   | vbr     | Section 4       |
   |           |              |            | (added) |                 |
   +-----------+--------------+------------+---------+-----------------+
   | pass      | existing     |  RFC5451   | vbr     | Section 4       |
   |           |              |            | (added) |                 |
   +-----------+--------------+------------+---------+-----------------+
   | fail      | existing     |  RFC5451   | vbr     | Section 4       |
   |           |              |            | (added) |                 |
   +-----------+--------------+------------+---------+-----------------+
   | temperror | existing     |  RFC5451   | vbr     | Section 4       |
   |           |              |            | (added) |                 |
   +-----------+--------------+------------+---------+-----------------+
   | permerror | existing     |  RFC5451   | vbr     | Section 4       |
   |           |              |            | (added) |                 |
   +-----------+--------------+------------+---------+-----------------+

6.  Security Considerations

   This memo creates a mechanism for relaying [VBR] results using the
   structure already defined by [AUTHRES].  The Security Considerations
   sections of those documents should be consulted.

7.  References

7.1.  Normative References

   [AUTHRES]              Kucherawy, M., "Message Header Field for
                          Indicating Message Authentication Status",



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                          RFC 5451, April 2009.

   [KEYWORDS]             Bradner, S., "Key words for use in RFCs to
                          Indicate Requirement Levels", BCP 14,
                          RFC 2119, March 1997.

   [VBR]                  Hoffman, P., Levine, J., and A. Hathcock,
                          "Vouch By Reference", RFC 5518, April 2009.

7.2.  Informative References

   [IANA-CONSIDERATIONS]  Narten, T. and H. Alvestrand, "Guidelines for
                          Writing an IANA Considerations Section in
                          RFCs", BCP 26, RFC 5226, May 2008.

Appendix A.  Authentication-Results Examples

   This section presents an example of the use of this new item header
   field to indicate VBR results.
































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A.1.  VBR Results

   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 DKIM and
   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 the
   sender can be trusted, so a "pass" result is included in the
   Authentication-Results field affixed prior to delivery.

Appendix B.  Acknowledgements

   The author wishes to acknowledge the following for their review and
   constructive criticism of this proposal: JD Falk, John Levine,
   Alessandro Vesely






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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









































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