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Versions: 00 01 02 03 04 05 06 07 draft-ietf-marf-dkim-reporting

Individual submission                                       M. Kucherawy
Internet-Draft                                                 Cloudmark
Intended status: Standards Track                          April 15, 2010
Expires: October 17, 2010


                Reporting of DKIM Verification Failures
                   draft-kucherawy-dkim-reporting-07

Abstract

   This memo presents an extension to the DomainKeys Identified Mail
   (DKIM) specifications to allow public keys for verification to
   include a reporting address to be used to report message verification
   issues, and extends an Internet Message reporting format to be
   followed when generating such reports.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
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   This Internet-Draft will expire on October 17, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   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 BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Keywords . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Imported Definitions . . . . . . . . . . . . . . . . . . .  4
   3.  Optional Key Reporting Address for DKIM  . . . . . . . . . . .  5
   4.  Optional Key Reporting Address for DKIM-ADSP . . . . . . . . .  7
   5.  Requested Reports  . . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  Requested Reports for DKIM Failures  . . . . . . . . . . .  9
     5.2.  Requested Reports for DKIM ADSP Failures . . . . . . . . .  9
   6.  Reporting Formats  . . . . . . . . . . . . . . . . . . . . . . 10
   7.  Extension ARF Fields for DKIM Reporting  . . . . . . . . . . . 11
     7.1.  New ARF Feedback Type  . . . . . . . . . . . . . . . . . . 11
     7.2.  New ARF Header Names . . . . . . . . . . . . . . . . . . . 11
     7.3.  DKIM Failure Types . . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  DKIM Key Tag Registration  . . . . . . . . . . . . . . . . 13
     8.2.  DKIM ADSP Tag Registration . . . . . . . . . . . . . . . . 13
     8.3.  Updates to ARF Feedback Types  . . . . . . . . . . . . . . 13
     8.4.  Updates to ARF Header Names  . . . . . . . . . . . . . . . 14
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
     9.1.  Inherited Considerations . . . . . . . . . . . . . . . . . 16
     9.2.  Forgeries  . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.3.  Automatic Generation . . . . . . . . . . . . . . . . . . . 16
     9.4.  Envelope Sender Selection  . . . . . . . . . . . . . . . . 16
     9.5.  Reporting Multiple Incidents . . . . . . . . . . . . . . . 17
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 18
     10.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 19
   Appendix B.  Examples  . . . . . . . . . . . . . . . . . . . . . . 20
     B.1.  Example Use of DKIM Key Extension Tags . . . . . . . . . . 20
     B.2.  Example Use of DKIM ADSP Extension Tags  . . . . . . . . . 20
     B.3.  Example Use of ARF Extension Headers . . . . . . . . . . . 21
   Appendix C.  Public Discussion . . . . . . . . . . . . . . . . . . 23
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 24






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1.  Introduction

   [DKIM] introduced a standard for digital signing of messages for the
   purposes of sender authentication.  There exist cases in which a
   domain name owner might want to receive reports from verifiers that
   determine DKIM-signed mail apparently from its domain is failing to
   verify according to [DKIM] or fails to conform to the domain's
   published signing practices according to [ADSP].

   This document extends [DKIM] and [ADSP] to add an optional reporting
   address to selector records, an optional means of specifying a
   desired report format, and furthermore extends
   [I-D.DRAFT-IETF-MARF-BASE] to add features required for DKIM
   reporting.

   This memo presumes those specifications thus modified will issue as
   RFCs without these modifications.  If the modifications are adopted
   prior to their publicatons, clearly those sections of this memo can
   be removed.
































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2.  Definitions

2.1.  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].

2.2.  Imported Definitions

   The ABNF token "qp-section" is imported from [MIME].

   base64 is defined in [MIME].






































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3.  Optional Key Reporting Address for DKIM

   There exist cases in which a domain name owner employing [DKIM] for
   e-mail signing and authentication may want to know when signatures in
   use by specific keys are not successfully verifying.  Currently there
   is no such mechanism defined.

   This document adds the following two optional "tags" (as defined in
   [DKIM]) to the DKIM key records, using the form defined in that
   specification:

   r= Reporting Address (plain-text; OPTIONAL; no default).  The value
      MUST be a dkim-quoted-printable string containing the local-part
      of an e-mail address to which a report SHOULD be sent when mail
      signed with this key fails verification because either (a) the
      signature verification itself failed, or (b) the body hash test
      failed.  The format of this reply is selected by the value of the
      "rf=" tag, defined below.  To generate a complete address to which
      the report is sent, the verifier simply appends to this value an
      "@" followed by the domain found in the "d=" tag of the signature
      whose validation failed.

      ABNF:

      key-r-tag = %x72 *WSP "=" *WSP qp-section

   rf=  Reporting Format (plain-text; OPTIONAL; default is "arf").  The
      value MUST be a colon-separated list of tokens representing
      desired reporting formats in order of preference.  Each element of
      the list MUST be a token that is taken from the registered list of
      DKIM report formats.  See Section 8 for a description of the
      registry and Section 6 for a description of recognized formats.
      The verifier generating reports MUST generate a report using the
      first token in the list that represents a report format it is
      capable of generating.

      ABNF:

      rep-format = ( "arf" / "smtp" )

      key-rf-tag = %x72 %x66 *WSP "=" *WSP rep-format *WSP 0*( ":" *WSP
      rep-format )

   ri=  Requested Report Interval (plain-text; OPTIONAL; default is
      "0").  The value is an integer that specifies an interval during
      which no more than one report about a given type of incident
      should be generated.  A value of "0" requests a report for every
      incident.  Where the requested interval is not zero, the agent



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      generating a report SHOULD include an "Incidents:" field in the
      generated report so the receiving agent has some indication of how
      many reports were suppressed.

      ABNF:

      key-ri-tag = %x72 %x69 *WSP "=" *WSP 1*DIGIT

   ro=  Requested Reports (plain-text; OPTIONAL; default is "all").  The
      value MUST be a colon-separated list of tokens representing those
      conditions under which a report is desired.  See Section 5.1 for a
      list of valid tags.

      ABNF:

      key-ro-type = ( "all" / "s" / "v" / "x" )

      key-ro-tag = %x72 %x6f *WSP "=" *WSP key-ro-type *WSP 0* ( ":"
      *WSP key-ro-type )

   rs=  Requested SMTP Error String (plain-text; OPTIONAL; no default).
      The value is a string the signing domain requests be included in
      SMTP error strings when messages are rejected.

      ABNF:

      key-rs-tag = %x72 %x73 *WSP "=" qp-section
























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4.  Optional Key Reporting Address for DKIM-ADSP

   There also exist cases in which a domain name owner employing [ADSP]
   for announcing signing practises with DKIM may want to know when
   messages are received without valid author domain signatures.
   Currently there is no such mechanism defined.

   This document adds the following two optional "tags" (as defined in
   [ADSP]) to the DKIM ADSP records, using the form defined in that
   specification:

   r= Reporting Address (plain-text; OPTIONAL; no default).  The value
      MUST be a dkim-quoted-printable string containing the local-part
      of an e-mail address to which a report SHOULD be sent when mail
      claiming to be from this domain failed the verification algorithm
      described in [ADSP], in particular because a message arrived
      without a signature that validates, which contradicts what the
      ADSP record claims, The format of this reply MUST be in the format
      specified by the "rf=" tag defined below.  To generate a complete
      address to which the report is sent, the verifier simply appends
      to this value an "@" followed by the domain whose policy was
      queried in order to evaluate the sender's ADSP.

      ABNF:

      adsp-r-tag = %x72 *WSP "=" qp-section

      ABNF:

      key-r-tag = %x72 *WSP "=" qp-section

   rf=  Reporting Format (plain-text; OPTIONAL; default is "arf").  The
      value MUST be a colon-separated list of tokens representing
      desired reporting formats in decreasing order of preference.  Each
      element of the list MUST be a token that is taken from the
      registered list of DKIM report formats.  See Section 8 for a
      description of the registry and Section 6 for a description of
      recognized formats.  The verifier generating reports MUST generate
      a report using the first token in the list that represents a
      report format it is capable of generating.

      ABNF:

      adsp-rf-tag = %x72 %x66 *WSP "=" *WSP rep-format *WSP 0*( ":" *WSP
      rep-format )






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   ri=  Requested Report Interval (plain-text; OPTIONAL; default is
      "0").  The value is an integer that specifies an interval during
      which no more than one report about a given type of incident
      should be generated.  A value of "0" requests a report for every
      incident.  Where the requested interval is not zero, the agent
      generating a report SHOULD include an "Incidents:" field in the
      generated report so the receiving agent has some indication of how
      many reports were suppressed.

      ABNF:

      adsp-ri-tag = %x72 %x69 *WSP "=" *WSP 1*DIGIT

   ro=  Requested Reports (plain-text; OPTIONAL; default is "all").  The
      value MUST be a colon-separated list of tokens representing those
      conditions under which a report is desired.  See Section 5.2 for a
      list of valid tags.

      ABNF:

      adsp-ro-type = ( "all" / "s" / "u" )

      adsp-ro-tag = %x72 %x6f *WSP "=" *WSP adsp-ro-type *WSP 0* ( ":"
      *WSP adsp-ro-type )

   rs=  Requested SMTP Error String (plain-text; OPTIONAL; no default).
      The value is a string the signing domain requests be included in
      SMTP error strings when messages are rejected.

      ABNF:

      adsp-rs-tag = %x72 %x73 *WSP "=" qp-section



















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5.  Requested Reports

   This memo also includes, as the "ro" tags defined above, the means by
   which the sender can request reports for specific circumstances of
   interest.  Verifiers MUST NOT generate reports for incidents that do
   not match a requested report, and MUST ignore requests for reports
   not included in this these lists.

5.1.  Requested Reports for DKIM Failures

   The following report requests are defined for DKIM keys:

   all  All reports are requested.

   s  Reports are requested for signature or key syntax errors.

   v  Reports are requested for signature verification failures or body
      hash mismatches.

   x  Reports are requested for signatures rejected by the verifier
      because the expiration time has passed.

5.2.  Requested Reports for DKIM ADSP Failures

   The following report requests are defined for DKIM keys:

   all  All reports are requested.

   s  Reports are requested for messages that have a valid [DKIM]
      signature but do not match the published [ADSP] policy.

   u  Reports are requested for messages that have no valid [DKIM]
      signature but do not match the published [ADSP] policy.


















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6.  Reporting Formats

   This section lists reporting formats supported by this DKIM reporting
   mechanism.  Currently only two formats are supported:

   arf:  Abuse Reporting Format, as defined in
      [I-D.DRAFT-IETF-MARF-BASE], and as extended in Section 7.

   smtp:  An SMTP error with a string descriptive of the problem that
      caused the DKIM verification to fail.  This explicitly requests
      evaluation of DKIM concurrent with the SMTP session, and rejection
      (if appropriate) whenever possible rather than acceptance of the
      message and later generation of a feedback report of some kind
      (e.g. "arf" above) when verification fails.  The presence of an
      "rs" tag (see Section 3 and Section 4) further requests a specific
      substring be included in the reply to ease automatic handling of
      such errors by sending or relaying MTAs.


































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7.  Extension ARF Fields for DKIM Reporting

   The current ARF format defined in [I-D.DRAFT-IETF-MARF-BASE] lacks
   some specific features required to do effective DKIM reporting.  This
   section describes the extensions required to do so and thus required
   to conform to this specification.

7.1.  New ARF Feedback Type

   A new feedback type of "dkim" is defined as an extension to Section
   8.2 of [I-D.DRAFT-IETF-MARF-BASE].  See Section 8.3 for details.

   The field names listed in that draft which may appear for this new
   feedback type include all shown in the draft except "Reported-URI"
   and "Removal-Recipient" as they have no semantics relating to DKIM.

7.2.  New ARF Header Names

   The following new ARF header names are defined as extensions to
   Section 6.2 of [I-D.DRAFT-IETF-MARF-BASE]:

   DKIM-ADSP-DNS:  The contents of the DNS TXT record retrieved when
      trying to determine the author domain's signing practices via the
      protocol defined in [ADSP].

   DKIM-Canonicalized-Body:  A base64 encoding of the canonicalized body
      of the message as generated by the verifier.  This header and
      value MUST be present for reports using feedback type "dkim" when
      reporting a "bodyhash" failure.

   DKIM-Canonicalized-Headers:  A base64 encoding of the canonicalized
      header of the message as generated by the verifier.  This header
      and value MUST be present for reports using feedback type "dkim".

   DKIM-Domain:  The domain that signed the message, taken from the "d="
      tag of the signature.  This field value SHOULD be included to ease
      processing in those cases where reports for multiple domains may
      be funneled into a single tool.

   DKIM-Failure:  Indicates the type of DKIM failure that is being
      reported.  The list of valid values is enumerated below.  This
      header and value MUST be present for reports using feedback type
      "dkim".

   DKIM-Identity:  The identity of the signature that failed
      verification, taken from the "i=" tag of the signature.  This
      header and value MUST be present for reports using feedback type
      "dkim" when reporting anything other than an "asp" failure.



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   DKIM-Selector:  The selector of the signature that failed
      verification, taken from the "s=" tag of the signature.  This
      header and value MUST be present for reports using feedback type
      "dkim" when reporting anything other than an "asp" failure.

   DKIM-Selector-DNS:  The contents of the DNS TXT record retrieved when
      trying to evaluate the DKIM signature (i.e. a TXT record whose
      name is assembled from the signature's "s=" and "d=" tags).

   The values that are base64 encodings may contain FWS for formatting
   purposes as per the usual header field wrapping defined in [MAIL].
   During decoding, any characters not in the base64 alphabet are
   ignored so that such line wrapping does not harm the value.  The ABNF
   token "FWS" is defined in [DKIM].

7.3.  DKIM Failure Types

   The list of defined DKIM failure types, used in the "DKIM-Failure:"
   header (defined above), is as follows:

   adsp:  The message did not conform to the sender's published [ADSP]
      signing practises.

   bodyhash:  The body hash in the signature and the body hash computed
      by the verifier did not match.

   granularity:  The key referenced by the signature on the message was
      not authorized for use by the sender.

   revoked:  The key referenced by the signature on the message has been
      revoked.

   signature:  The signature on the message did not successfully verify
      against the header hash and public key.

   Supplementary data may be included in the form of [MAIL]-compliant
   comments.  For example, "Failure: asp" could be augmented by a
   comment to indicate that the failed message was rejected because it
   was not signed when it should have been.  See Appendix B for
   examples.











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8.  IANA Considerations

   As required by [IANA-CONSIDERATIONS], this section contains registry
   information for the new [DKIM] key tags, the new [ADSP] tags, and the
   extensions to [I-D.DRAFT-IETF-MARF-BASE].

8.1.  DKIM Key Tag Registration

   IANA is requested to update the DKIM Key Tag Specification Registry
   to include the following new items:

                           +------+-----------------+
                           | TYPE | REFERENCE       |
                           +------+-----------------+
                           | r    | (this document) |
                           | rf   | (this document) |
                           | ri   | (this document) |
                           | ro   | (this document) |
                           | rs   | (this document) |
                           +------+-----------------+

8.2.  DKIM ADSP Tag Registration

   IANA is requested to update the DKIM ADSP Tag Specification Registry
   to include the following new items:

                           +------+-----------------+
                           | TYPE | REFERENCE       |
                           +------+-----------------+
                           | r    | (this document) |
                           | rf   | (this document) |
                           | ri   | (this document) |
                           | ro   | (this document) |
                           | rs   | (this document) |
                           +------+-----------------+

8.3.  Updates to ARF Feedback Types

   The following feedback type is added to the Feedback Report Feedback
   Type Registry:

       Feedback Type: dkim
       Description: DKIM failure report
       Registration: (this document)







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8.4.  Updates to ARF Header Names

   The following headers are added to the Feedback Report Header Names
   Registry:

       Field Name: DKIM-ADSP-DNS
       Description: Retrieved DKIM ADSP record
       Multiple Appearances: No
       Related "Feedback-Type": dkim


       Field Name: DKIM-Canonicalized-Body
       Description: Canonicalized body, per DKIM
       Multiple Appearances: No
       Related "Feedback-Type": dkim


       Field Name: DKIM-Canonicalized-Headers
       Description: Canonicalized headers, per DKIM
       Multiple Appearances: No
       Related "Feedback-Type": dkim


       Field Name: DKIM-Domain
       Description: DKIM signing domain from "d=" tag
       Multiple Appearances: No
       Related "Feedback-Type": dkim


       Field Name: DKIM-Failure
       Description: Type of DKIM failure
       Multiple Appearances: No
       Related "Feedback-Type": dkim


       Field Name: DKIM-Identity
       Description: Identity from DKIM signature
       Multiple Appearances: No
       Related "Feedback-Type": dkim


       Field Name: DKIM-Selector
       Description: Selector from DKIM signature
       Multiple Appearances: No
       Related "Feedback-Type": dkim






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       Field Name: DKIM-Selector-DNS
       Description: Retrieved DKIM key record
       Multiple Appearances: No
       Related "Feedback-Type": dkim















































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9.  Security Considerations

   Security issues with respect to these DKIM reports are similar to
   those found in [DSN].

9.1.  Inherited Considerations

   Implementors are advised to consider the Security Considerations
   sections of [DKIM], [ADSP] and [I-D.DRAFT-IETF-MARF-BASE].

9.2.  Forgeries

   These reports may be forged as easily as ordinary Internet electronic
   mail.  User agents and automatic mail handling facilities (such as
   mail distribution list exploders) that wish to make automatic use of
   DSNs of any kind should take appropriate precautions to minimize the
   potential damage from denial-of-service attacks.

   Security threats related to forged DSNs include the sending of:

   a.  A falsified DKIM failure notification when the message was in
       fact delivered to the indicated recipient;

   b.  Falsified signature information, such as selector, domain, etc.

   Perhaps the simplest means of mitigating this threat is to assert
   that DKIM reports should themselves be signed.  On the other hand, if
   there's a problem with the DKIM infrastructure at the verifier,
   signing DKIM failure reports may produce reports that aren't trusted
   or even accepted by their intended recipients.

9.3.  Automatic Generation

   Automatic generation of these reports by verifying agents can cause a
   denial-of-service attack when a large volume of e-mail is sent that
   causes DKIM verification failures for whatever reason.

   It is unclear what a good solution for this issue is.  Limiting the
   rate of generation of these messages may be apropos but threatens to
   inhibit the distribution of important and possibly time-sensitive
   information.

9.4.  Envelope Sender Selection

   In the case of transmitted DKIM reports in the form of a new message,
   it is necessary to construct the message so as to avoid amplification
   attacks, deliberate or otherwise.  Thus, per Section 2 of [DSN], the
   envelope sender address of the DKIM report SHOULD be chosen to ensure



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   that no delivery status reports will be issued in response to the
   DKIM report itself, and MUST be chosen so that these reports will not
   generate mail loops.  Whenever an SMTP transaction is used to send a
   DKIM report, the MAIL FROM command MUST use a NULL return address,
   i.e.  "MAIL FROM:<>".

9.5.  Reporting Multiple Incidents

   If it is known that a particular host generates abuse reports upon
   certain incidents, an attacker could forge a high volume of messages
   that will trigger such a report.  The recipient of the report could
   then be innundated with reports.  This could easily be extended to a
   distributed denial-of-service attack by finding a number of report-
   generating servers.

   The incident count referenced in [I-D.DRAFT-IETF-MARF-BASE] provides
   a limited form of mitigation.  The host generating reports may elect
   to send reports only periodically, with each report representing a
   number of identical or near-identical incidents.  One might even do
   something inverse-exponentially, sending reports for each of the
   first ten incidents, then every tenth incident up to 100, then every
   100th incident up to 1000, etc. until some period of relative quiet
   after which the limitation resets.

   The use of this for "near-identical" incidents in particular causes a
   degradation in reporting quality, however.  If for example a large
   number of pieces of spam arrive from one attacker, a reporting agent
   may decide only to send a report about a fraction of those messages.
   While this averts a flood of reports to a system administrator, the
   precise details of each incident are similarly not sent.





















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10.  References

10.1.  Normative References

   [ADSP]     Allman, E., Delany, M., Fenton, J., and J. Levine, "DKIM
              Sender Signing Practises", RFC 5617, August 2009.

   [DKIM]     Allman, E., Callas, J., Delany, M., Libbey, M., Fenton,
              J., and M. Thomas, "DomainKeys Identified Mail (DKIM)
              Signatures", RFC 4871, May 2007.

   [I-D.DRAFT-IETF-MARF-BASE]
              Shafranovich, Y., Levine, J., Hoffman, P., and M.
              Kucherawy, "An Extensible Format for Email Feedback
              Reports", I-D DRAFT-IETF-MARF-BASE, April 2010.

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

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

   [MAIL]     Resnick, P., "Internet Message Format", RFC 2822,
              April 2001.

   [MIME]     Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

10.2.  Informative References

   [DSN]      Moore, K. and G. Vaudreuil, "An Extensible Message Format
              for Delivery Status Notifications", RFC 3464,
              January 2003.















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Appendix A.  Acknowledgements

   The author wishes to acknowledge the following for their review and
   constructive criticism of this proposal: JD Falk















































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Appendix B.  Examples

   This section contains examples of the use of each of the extensions
   defined by this memo.

B.1.  Example Use of DKIM Key Extension Tags

   A DKIM key record including use of the extensions defined by this
   memo:

       v=DKIM1; k=rsa; t=y; r=dkim-errors; rf=arf; ro=v:x; p=MIGfMA0GCS
       qGSIb3DQEBAQUAA4GNADCBiQKBgQDh2vbhJTijCs2qbyJcwRCa8WqDTxI+PisFJo
       faPtoDJy0Qn41uNayCajfKADVcLqc87sXQS6GxfchPfzx7Vh9crYdxRbN/o/URCu
       ZsKmym1i1IPTwRLcXSnuKS0XDs1eRW2WQHGYlXksUDqSHWOS3ZO1W5t/FLcZHpIl
       l/80xs4QIDAQAB

   Example 1: DKIM key record using these extensions

   This example DKIM key record contains the following data in addition
   to the basic DKIM key data:

   o  Reports about signature evaluation failures should be send to the
      address "dkim-errors" at the sender's domain;

   o  The sender's domain requests reports in the "arf" format;

   o  Only reports about signature verification failures and expired
      signatures should be generated.

B.2.  Example Use of DKIM ADSP Extension Tags

   A DKIM ADSP record including use of the extensions defined by this
   memo:

       dkim=all; r=dkim-adsp-errors; rf=arf; ro=u

   Example 2: DKIM ADSP record using these extensions

   This example ADSP record makes the following assertions:

   o  The sending domain (i.e. the one that is advertising this policy)
      signs all mail it sends;

   o  Reports about ADSP evaluation failures should be send to the
      address "dkim-adsp-errors" at the sender's domain;

   o  The sender's domain requests reports in the "arf" format;




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   o  Only reports about unsigned messages should be generated.

B.3.  Example Use of ARF Extension Headers

   An ARF-formatted report using some of the proposed ARF extension
   fields:

       From: arf-daemon@example.com
       To: recipient@example.net
       Subject: This is a test
       Date: Wed, 14 Apr 2010 12:17:45 -0700 (PDT)
       MIME-Version: 1.0
       Content-Type: multipart/report; report-type=feedback-report;
           boundary="part1_13d.2e68ed54_boundary"

       --part1_13d.2e68ed54_boundary
       Content-Type: text/plain; charset="US-ASCII"
       Content-Transfer-Encoding: 7bit

       This is an email abuse report for an email message received
       from IP 192.0.2.1 on Wed, 14 Apr 2010 12:15:31 PDT. For more
       information about this format please see
       http://www.mipassoc.org/arf/.

       --part1_13d.2e68ed54_boundary
       Content-Type: message/feedback-report

       Feedback-Type: dkim
       User-Agent: SomeDKIMFilter/1.0
       Version: 1.0
       Original-Mail-From: <randomuser@example.net>
       Original-Rcpt-To: <user@example.com>
       Received-Date: Wed, 14 Apr 2010 12:15:31 -0700 (PDT)
       Source-IP: 192.0.2.1
       Authentication-Results: mail.example.com; dkim=fail
           header.d=example.net
       Reported-Domain: example.net
       DKIM-Domain: example.net
       DKIM-Failure: bodyhash

       --part1_13d.2e68ed54_boundary
       Content-Type: message/rfc822

       DKIM-Signature: v=1; c=relaxed/simple; a=rsa-sha256;
           s=testkey; d=example.net; h=From:To:Subject:Date;
           bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;
           b=AuUoFEfDxTDkHlLXSZEpZj79LICEps6eda7W3deTVFOk4yAUoqOB
            4nujc7YopdG5dWLSdNg6xNAZpOPr+kHxt1IrE+NahM6L/LbvaHut



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            KVdkLLkpVaVVQPzeRDI009SO2Il5Lu7rDNH6mZckBdrIx0orEtZV
            4bmp/YzhwvcubU4=
       Received: from smtp-out.example.net by mail.example.com
           with SMTP id o3F52gxO029144;
           Wed, 14 Apr 2010 12:15:31 -0700 (PDT)
       Received: from internal-client-001.example.com
           by mail.example.com
           with SMTP id o3F3BwdY028431;
           Wed, 14 Apr 2010 12:12:09 -0700 (PDT)
       From: randomuser@example.net
       To: user@example.com
       Date: Wed, 14 Apr 2010 12:12:09 -0700 (PDT)
       Subject: This is a test

       Hi, just making sure DKIM is working!

       --part1_13d.2e68ed54_boundary--

   Example 3: Example ARF report using these extensions

   This example ARF message is making the following assertion:

   o  DKIM verification of the signature added within "example.net"
      failed when it was processed on arrival at "mail.example.com".

   o  The cause for the verification failure was a mismatch between the
      body contents observed at the verifier and the body hash contained
      in the signature.























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Appendix C.  Public Discussion

   [REMOVE BEFORE PUBLICATION]

   Public discussion of this proposed specification is handled via the
   mail-vet-discuss@mipassoc.org mailing list.  The list is open.
   Access to subscription forms and to list archives can be found at
   http://mipassoc.org/mailman/listinfo/mail-vet-discuss.











































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Author's Address

   Murray S. Kucherawy
   Cloudmark
   128 King St., 2nd Floor
   San Francisco, CA  94107
   US

   Phone: +1 415 946 3800
   Email: msk@cloudmark.com









































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