Internet DRAFT - draft-hallambaker-dkim-extensions

draft-hallambaker-dkim-extensions






Internet Engineering Task Force                          P. Hallam-Baker
Internet-Draft                                              VeriSign Inc
Intended status: Informational                             July 13, 2008
Expires: January 14, 2009


                            DKIM Extensions
                  draft-hallambaker-dkim-extensions-01

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Abstract

   Optional extensions for DKIM are described.  A DKIM Policy statement
   is defined for the policy 'this zone never sends mail'.  The NULL Key
   Algorithm is defined to simplify management of large zones where most
   mail is signed but with important exceptions.  The X509 key record
   extension allows the location from which an X.509v3 certificate for
   the key specified in the record may be obtained.









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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
   2.  NoMail Policy . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  NULL Signature Algorithm  . . . . . . . . . . . . . . . . . . . 3
   4.  X509 Certificate Location Extension . . . . . . . . . . . . . . 3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   Intellectual Property and Copyright Statements  . . . . . . . . . . 5






































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1.  Introduction

1.1.  Requirements Language

   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 RFC 2119 [RFC2119].


2.  NoMail Policy

   The NOMAIL policy is declared in an SSP record using the tag
   "NOMAIL".

   No parameters are specified for the NOMAIL policy.

   If specified the NOMAIL policy states that no mail is sent from the
   domain to which it is attached.  All mail that purports to have been
   sent by that domain MUST be considered suspicious.


3.  NULL Signature Algorithm

   The NULL Signature algorithm is a DKIM signature algorithm that
   always produces the same signature value regardless of the message
   contents.

   A message signed with the NULL signature MUST be treated as if it
   were unsigned for all purposes other than verifying compliance with a
   DKIM policy.  For purposes of policy compliance, a message that
   carries a NULL signature is considered to be compliant if and only if
   it is consistent with the signing restrictions specified in the key
   record.

   A key record that specifies the NULL signature algorithm SHOULD
   specify usage restricted to specific senders.


4.  X509 Certificate Location Extension

   The x509 key record extension specifies a URL from which a
   certificate chain corresponding to the key specified in the key
   record may be obtained.

   The key chain is specified as a CMS SignedData structure with no
   data.





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5.  Acknowledgements

   The ideas in this document arose from extensive discussions with the
   DKIM working group, in particular Hector Santos and others.


6.  IANA Considerations

   This document requests allocation of a DKIM SSP tag 'NOMAIL'


7.  Security Considerations

   The NOMAIL policy MAY be employed to perform a denial of service
   attack.


8.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.


Author's Address

   Phillip Hallam-Baker
   VeriSign Inc

   Email: pbaker@verisign.com






















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Full Copyright Statement

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