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Versions: 00 01

DMARC                                                    A. Brotman (ed)
Internet-Draft                                             Comcast, Inc.
Obsoletes: 7489 (if approved)                          November 11, 2020
Intended status: Standards Track
Expires: May 15, 2021


                       DMARC Aggregate Reporting
                draft-ietf-dmarc-aggregate-reporting-00

Abstract

   DMARC allows for domain holders to request aggregate reports from
   receivers.  This report is an XML document, and contains extensible
   elements that allow for other types of data to be specified later.
   The aggregate reports can be submitted to the domain holder's
   specified destination as supported by the receiver.

   This document (along with others) obsoletes RFC7489.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on May 15, 2021.

Copyright Notice

   Copyright (c) 2020 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
   (https://trustee.ietf.org/license-info) 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



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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  DMARC Feedback  . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Verifying External Destinations . . . . . . . . . . . . .   3
     2.2.  Aggregate Reports . . . . . . . . . . . . . . . . . . . .   3
       2.2.1.  Transport . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Appendix A. DMARC XML Schema  . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   A key component of DMARC is the ability for domain holders to request
   that receivers provide various types of reports.  These reports allow
   domain holders to have insight into which IP addresses are sending on
   their behalf, and some insight into whether or not the volume may be
   legitimate.  These reports expose information relating to the DMARC
   policy, as well as the outcome of SPF [RFC7208] & DKIM [RFC6376]
   validation.

1.1.  Terminology

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [RFC2119].

2.  DMARC Feedback

   Providing Domain Owners with visibility into how Mail Receivers
   implement and enforce the DMARC mechanism in the form of feedback is
   critical to establishing and maintaining accurate authentication
   deployments.  When Domain Owners can see what effect their policies
   and practices are having, they are better willing and able to use
   quarantine and reject policies.







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2.1.  Verifying External Destinations

   [<https://trac.ietf.org/trac/dmarc/ticket/76>]

2.2.  Aggregate Reports

   The DMARC aggregate feedback report is designed to provide Domain
   Owners with precise insight into:

   o  authentication results,

   o  corrective action that needs to be taken by Domain Owners, and

   o  the effect of Domain Owner DMARC policy on email streams processed
      by Mail Receivers.

   Aggregate DMARC feedback provides visibility into real-world email
   streams that Domain Owners need to make informed decisions regarding
   the publication of DMARC policy.  When Domain Owners know what
   legitimate mail they are sending, what the authentication results are
   on that mail, and what forged mail receivers are getting, they can
   make better decisions about the policies they need and the steps they
   need to take to enable those policies.  When Domain Owners set
   policies appropriately and understand their effects, Mail Receivers
   can act on them confidently.

   Visibility comes in the form of daily (or more frequent) Mail
   Receiver-originated feedback reports that contain aggregate data on
   message streams relevant to the Domain Owner.  This information
   includes data about messages that passed DMARC authentication as well
   as those that did not.

   The format for these reports is defined in Appendix C.

   The report SHOULD include the following data:

   o  The DMARC policy discovered and applied, if any

   o  The selected message disposition

   o  The identifier evaluated by SPF and the SPF result, if any

   o  The identifier evaluated by DKIM and the DKIM result, if any

   o  For both DKIM and SPF, an indication of whether the identifier was
      in alignment





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   o  Data for each Domain Owner's subdomain separately from mail from
      the sender's Organizational Domain, even if there is no explicit
      subdomain policy

   o  Sending and receiving domains

   o  The policy requested by the Domain Owner and the policy actually
      applied (if different)

   o  The number of successful authentications

   o  The counts of messages based on all messages received, even if
      their delivery is ultimately blocked by other filtering agents

   Note that Domain Owners or their agents may change the published
   DMARC policy for a domain or subdomain at any time.  From a Mail
   Receiver's perspective, this will occur during a reporting period and
   may be noticed during that period, at the end of that period when
   reports are generated, or during a subsequent reporting period, all
   depending on the Mail Receiver's implementation.  Under these
   conditions, it is possible that a Mail Receiver could do any of the
   following:

   o  generate for such a reporting period a single aggregate report
      that includes message dispositions based on the old policy, or a
      mix of the two policies, even though the report only contains a
      single "policy_published" element;

   o  generate multiple reports for the same period, one for each
      published policy occurring during the reporting period;

   o  generate a report whose end time occurs when the updated policy
      was detected, regardless of any requested report interval.

   The report SHOULD include the following data:

   o  The DMARC policy discovered and applied, if any

   o  The selected message disposition

   o  The identifier evaluated by SPF and the SPF result, if any

   o  The identifier evaluated by DKIM and the DKIM result, if any

   o  For both DKIM and SPF, an indication of whether the identifier was
      in alignment





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   o  Data for each Domain Owner's subdomain separately from mail from
      the sender's Organizational Domain, even if there is no explicit
      subdomain policy

   o  Sending and receiving domains

   o  The policy requested by the Domain Owner and the policy actually
      applied (if different)

   o  The number of successful authentications

   o  The counts of messages based on all messages received, even if
      their delivery is ultimately blocked by other filtering agents

   Note that Domain Owners or their agents may change the published
   DMARC policy for a domain or subdomain at any time.  From a Mail
   Receiver's perspective, this will occur during a reporting period and
   may be noticed during that period, at the end of that period when
   reports are generated, or during a subsequent reporting period, all
   depending on the Mail Receiver's implementation.  Under these
   conditions, it is possible that a Mail Receiver could do any of the
   following:

   o  generate for such a reporting period a single aggregate report
      that includes message dispositions based on the old policy, or a
      mix of the two policies, even though the report only contains a
      single "policy_published" element;

   o  generate multiple reports for the same period, one for each
      published policy occurring during the reporting period;

   o  generate a report whose end time occurs when the updated policy
      was detected, regardless of any requested report interval.

2.2.1.  Transport

   Where the URI specified in a "rua" tag does not specify otherwise, a
   Mail Receiver generating a feedback report SHOULD employ a secure
   transport mechanism.

   The Mail Receiver, after preparing a report, MUST evaluate the
   provided reporting URIs in the order given.  Any reporting URI that
   includes a size limitation exceeded by the generated report (after
   compression and after any encoding required by the particular
   transport mechanism) MUST NOT be used.  An attempt MUST be made to
   deliver an aggregate report to every remaining URI, up to the
   Receiver's limits on supported URIs.




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   If transport is not possible because the services advertised by the
   published URIs are not able to accept reports (e.g., the URI refers
   to a service that is unreachable, or all provided URIs specify size
   limits exceeded by the generated record), the Mail Receiver SHOULD
   send a short report (see Section 7.2.2) indicating that a report is
   available but could not be sent.  The Mail Receiver MAY cache that
   data and try again later, or MAY discard data that could not be sent.

2.2.1.1.  Email

   The message generated by the Mail Receiver MUST be a [MAIL] message
   formatted per [MIME].  The aggregate report itself MUST be included
   in one of the parts of the message.  A human-readable portion MAY be
   included as a MIME part (such as a text/plain part).

   The aggregate data MUST be an XML file that SHOULD be subjected to
   GZIP compression.  Declining to apply compression can cause the
   report to be too large for a receiver to process (a commonly observed
   receiver limit is ten megabytes); doing the compression increases the
   chances of acceptance of the report at some compute cost.  The
   aggregate data SHOULD be present using the media type "application/
   gzip" if compressed (see [GZIP]), and "text/xml" otherwise.  The
   filename is typically constructed using the following ABNF:

      filename = receiver "!" policy-domain "!" begin-timestamp
                 "!" end-timestamp [ "!" unique-id ] "." extension

      unique-id = 1*(ALPHA / DIGIT)

      receiver = domain
                 ; imported from [MAIL]

      policy-domain   = domain

      begin-timestamp = 1*DIGIT
                        ; seconds since 00:00:00 UTC January 1, 1970
                        ; indicating start of the time range contained
                        ; in the report

      end-timestamp = 1*DIGIT
                      ; seconds since 00:00:00 UTC January 1, 1970
                      ; indicating end of the time range contained
                      ; in the report

      extension = "xml" / "xml.gz"

   The extension MUST be "xml" for a plain XML file, or "xml.gz" for an
   XML file compressed using GZIP.



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   "unique-id" allows an optional unique ID generated by the Mail
   Receiver to distinguish among multiple reports generated
   simultaneously by different sources within the same Domain Owner.

   For example, this is a possible filename for the gzip file of a
   report to the Domain Owner "example.com" from the Mail Receiver
   "mail.receiver.example":

         mail.receiver.example!example.com!1013662812!1013749130.gz

   No specific MIME message structure is required.  It is presumed that
   the aggregate reporting address will be equipped to extract MIME
   parts with the prescribed media type and filename and ignore the
   rest.

   Email streams carrying DMARC feedback data MUST conform to the DMARC
   mechanism, thereby resulting in an aligned "pass" (see Section 3.1).
   This practice minimizes the risk of report consumers processing
   fraudulent reports.

   The RFC5322.Subject field for individual report submissions SHOULD
   conform to the following ABNF:

      dmarc-subject = %x52.65.70.6f.72.74 1*FWS       ; "Report"
                      %x44.6f.6d.61.69.6e.3a 1*FWS    ; "Domain:"
                      domain-name 1*FWS               ; from RFC 6376
                      %x53.75.62.6d.69.74.74.65.72.3a ; "Submitter:"
                      1*FWS domain-name 1*FWS
                      %x52.65.70.6f.72.74.2d.49.44.3a ; "Report-ID:"
                      msg-id                          ; from RFC 5322

   The first domain-name indicates the DNS domain name about which the
   report was generated.  The second domain-name indicates the DNS
   domain name representing the Mail Receiver generating the report.
   The purpose of the Report-ID: portion of the field is to enable the
   Domain Owner to identify and ignore duplicate reports that might be
   sent by a Mail Receiver.

   For instance, this is a possible Subject field for a report to the
   Domain Owner "example.com" from the Mail Receiver
   "mail.receiver.example".  It is line-wrapped as allowed by [MAIL]:

                    Subject: Report Domain: example.com
                        Submitter: mail.receiver.example
                        Report-ID: <2002.02.15.1>

   This transport mechanism potentially encounters a problem when
   feedback data size exceeds maximum allowable attachment sizes for



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   either the generator or the consumer.  See Section 7.2.2 for further
   discussion.

2.2.1.2.  Other Methods

   The specification as written allows for the addition of other
   registered URI schemes to be supported in later versions.

3.  Security Considerations

   TBD

4.  IANA Considerations

   TBD

5.  Appendix A.  DMARC XML Schema

    <?xml version="1.0"?>
    <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
      targetNamespace="http://dmarc.org/dmarc-xml/0.1">

    <!-- The time range in UTC covered by messages in this report,
         specified in seconds since epoch. -->
    <xs:complexType name="DateRangeType">
      <xs:all>
        <xs:element name="begin" type="xs:integer"/>
        <xs:element name="end" type="xs:integer"/>
      </xs:all>
    </xs:complexType>

    <!-- Report generator metadata. -->
    <xs:complexType name="ReportMetadataType">
      <xs:sequence>
        <xs:element name="org_name" type="xs:string"/>
        <xs:element name="email" type="xs:string"/>
        <xs:element name="extra_contact_info" type="xs:string"
                    minOccurs="0"/>
        <xs:element name="report_id" type="xs:string"/>
        <xs:element name="date_range" type="DateRangeType"/>
        <xs:element name="error" type="xs:string" minOccurs="0"
                    maxOccurs="unbounded"/>
      </xs:sequence>
    </xs:complexType>

    <!-- Alignment mode (relaxed or strict) for DKIM and SPF. -->
    <xs:simpleType name="AlignmentType">
      <xs:restriction base="xs:string">



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        <xs:enumeration value="r"/>
        <xs:enumeration value="s"/>
      </xs:restriction>
    </xs:simpleType>

    <!-- The policy actions specified by p and sp in the
         DMARC record. -->
    <xs:simpleType name="DispositionType">
      <xs:restriction base="xs:string">
        <xs:enumeration value="none"/>
        <xs:enumeration value="quarantine"/>
        <xs:enumeration value="reject"/>
      </xs:restriction>
    </xs:simpleType>

    <!-- The DMARC policy that applied to the messages in
         this report. -->
    <xs:complexType name="PolicyPublishedType">
      <xs:all>
        <!-- The domain at which the DMARC record was found. -->
        <xs:element name="domain" type="xs:string"/>
        <!-- The DKIM alignment mode. -->
        <xs:element name="adkim" type="AlignmentType"
                    minOccurs="0"/>
        <!-- The SPF alignment mode. -->
        <xs:element name="aspf" type="AlignmentType"
                    minOccurs="0"/>
        <!-- The policy to apply to messages from the domain. -->
        <xs:element name="p" type="DispositionType"/>
        <!-- The policy to apply to messages from subdomains. -->
        <xs:element name="sp" type="DispositionType"/>
        <!-- The percent of messages to which policy applies. -->
        <xs:element name="pct" type="xs:integer"/>
        <!-- Failure reporting options in effect. -->
        <xs:element name="fo" type="xs:string"/>
      </xs:all>
    </xs:complexType>

    <!-- The DMARC-aligned authentication result. -->
    <xs:simpleType name="DMARCResultType">
      <xs:restriction base="xs:string">
        <xs:enumeration value="pass"/>
        <xs:enumeration value="fail"/>
      </xs:restriction>
    </xs:simpleType>

    <!-- Reasons that may affect DMARC disposition or execution
         thereof. -->



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    <xs:simpleType name="PolicyOverrideType">
      <xs:restriction base="xs:string">
        <xs:enumeration value="forwarded"/>
        <xs:enumeration value="sampled_out"/>
        <xs:enumeration value="trusted_forwarder"/>
        <xs:enumeration value="mailing_list"/>
        <xs:enumeration value="local_policy"/>
        <xs:enumeration value="other"/>
      </xs:restriction>
    </xs:simpleType>

    <!-- How do we allow report generators to include new
         classes of override reasons if they want to be more
         specific than "other"? -->
    <xs:complexType name="PolicyOverrideReason">
      <xs:all>
        <xs:element name="type" type="PolicyOverrideType"/>
        <xs:element name="comment" type="xs:string"
                    minOccurs="0"/>
      </xs:all>
    </xs:complexType>

    <!-- Taking into account everything else in the record,
         the results of applying DMARC. -->
    <xs:complexType name="PolicyEvaluatedType">
      <xs:sequence>
        <xs:element name="disposition" type="DispositionType"/>
        <xs:element name="dkim" type="DMARCResultType"/>
        <xs:element name="spf" type="DMARCResultType"/>
        <xs:element name="reason" type="PolicyOverrideReason"
                    minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>
    </xs:complexType>

    <!-- Credit to Roger L. Costello for IPv4 regex
         http://mailman.ic.ac.uk/pipermail/xml-dev/1999-December/
              018018.html -->
    <!-- Credit to java2s.com for IPv6 regex
         http://www.java2s.com/Code/XML/XML-Schema/
              IPv6addressesareeasiertodescribeusingasimpleregex.htm -->
    <xs:simpleType name="IPAddress">
      <xs:restriction base="xs:string">
        <xs:pattern value="((1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5]).){3}
                    (1?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])|
                    ([A-Fa-f0-9]{1,4}:){7}[A-Fa-f0-9]{1,4}"/>
      </xs:restriction>
    </xs:simpleType>




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    <xs:complexType name="RowType">
      <xs:all>
        <!-- The connecting IP. -->
        <xs:element name="source_ip" type="IPAddress"/>
        <!-- The number of matching messages. -->
        <xs:element name="count" type="xs:integer"/>
        <!-- The DMARC disposition applying to matching
             messages. -->
        <xs:element name="policy_evaluated"
                    type="PolicyEvaluatedType"
                    minOccurs="1"/>
      </xs:all>
    </xs:complexType>

    <xs:complexType name="IdentifierType">
      <xs:all>
        <!-- The envelope recipient domain. -->
        <xs:element name="envelope_to" type="xs:string"
                    minOccurs="0"/>
        <!-- The RFC5321.MailFrom domain. -->
        <xs:element name="envelope_from" type="xs:string"
                    minOccurs="1"/>
        <!-- The RFC5322.From domain. -->
        <xs:element name="header_from" type="xs:string"
                    minOccurs="1"/>
      </xs:all>
    </xs:complexType>

    <!-- DKIM verification result, according to RFC 7001
         Section 2.6.1. -->
    <xs:simpleType name="DKIMResultType">
      <xs:restriction base="xs:string">
        <xs:enumeration value="none"/>
        <xs:enumeration value="pass"/>
        <xs:enumeration value="fail"/>
        <xs:enumeration value="policy"/>
        <xs:enumeration value="neutral"/>
        <xs:enumeration value="temperror"/>
        <xs:enumeration value="permerror"/>
      </xs:restriction>
    </xs:simpleType>

    <xs:complexType name="DKIMAuthResultType">
      <xs:all>
        <!-- The "d=" parameter in the signature. -->
        <xs:element name="domain" type="xs:string"
                    minOccurs="1"/>
        <!-- The "s=" parameter in the signature. -->



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        <xs:element name="selector" type="xs:string"
                    minOccurs="0"/>
        <!-- The DKIM verification result. -->
        <xs:element name="result" type="DKIMResultType"
                    minOccurs="1"/>
        <!-- Any extra information (e.g., from
             Authentication-Results). -->
        <xs:element name="human_result" type="xs:string"
                    minOccurs="0"/>
      </xs:all>
    </xs:complexType>

    <!-- SPF domain scope. -->
    <xs:simpleType name="SPFDomainScope">
      <xs:restriction base="xs:string">
        <xs:enumeration value="helo"/>
        <xs:enumeration value="mfrom"/>
      </xs:restriction>
    </xs:simpleType>

    <!-- SPF result. -->
    <xs:simpleType name="SPFResultType">
      <xs:restriction base="xs:string">
        <xs:enumeration value="none"/>
        <xs:enumeration value="neutral"/>
        <xs:enumeration value="pass"/>
        <xs:enumeration value="fail"/>
        <xs:enumeration value="softfail"/>
        <!-- "TempError" commonly implemented as "unknown". -->
        <xs:enumeration value="temperror"/>
        <!-- "PermError" commonly implemented as "error". -->
        <xs:enumeration value="permerror"/>
      </xs:restriction>
    </xs:simpleType>

    <xs:complexType name="SPFAuthResultType">
      <xs:all>
        <!-- The checked domain. -->
        <xs:element name="domain" type="xs:string" minOccurs="1"/>
        <!-- The scope of the checked domain. -->
        <xs:element name="scope" type="SPFDomainScope" minOccurs="1"/>
        <!-- The SPF verification result. -->
        <xs:element name="result" type="SPFResultType"
                    minOccurs="1"/>
      </xs:all>
    </xs:complexType>

    <!-- This element contains DKIM and SPF results, uninterpreted



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         with respect to DMARC. -->
    <xs:complexType name="AuthResultType">
      <xs:sequence>
        <!-- There may be no DKIM signatures, or multiple DKIM
             signatures. -->
        <xs:element name="dkim" type="DKIMAuthResultType"
          minOccurs="0" maxOccurs="unbounded"/>
        <!-- There will always be at least one SPF result. -->
        <xs:element name="spf" type="SPFAuthResultType" minOccurs="1"
                    maxOccurs="unbounded"/>
      </xs:sequence>
    </xs:complexType>

    <!-- This element contains all the authentication results that
         were evaluated by the receiving system for the given set of
         messages. -->
    <xs:complexType name="RecordType">
      <xs:sequence>
        <xs:element name="row" type="RowType"/>
        <xs:element name="identifiers" type="IdentifierType"/>
        <xs:element name="auth_results" type="AuthResultType"/>
      </xs:sequence>
    </xs:complexType>

    <!-- Parent -->
    <xs:element name="feedback">
      <xs:complexType>
        <xs:sequence>
          <xs:element name="version"
                      type="xs:decimal"/>
          <xs:element name="report_metadata"
                      type="ReportMetadataType"/>
          <xs:element name="policy_published"
                      type="PolicyPublishedType"/>
          <xs:element name="record" type="RecordType"
                      maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:complexType>
    </xs:element>
    </xs:schema>

6.  References

6.1.  Normative References







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   [RFC6376]  Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
              "DomainKeys Identified Mail (DKIM) Signatures", STD 76,
              RFC 6376, DOI 10.17487/RFC6376, September 2011,
              <https://www.rfc-editor.org/info/rfc6376>.

   [RFC7208]  Kitterman, S., "Sender Policy Framework (SPF) for
              Authorizing Use of Domains in Email, Version 1", RFC 7208,
              DOI 10.17487/RFC7208, April 2014,
              <https://www.rfc-editor.org/info/rfc7208>.

6.2.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

Author's Address

   Alex Brotman
   Comcast, Inc.

   Email: alex_brotman@comcast.com




























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