Re: [dmarc-ietf] [Gen-art] [Last-Call] Genart last call review of draft-ietf-dmarc-psd-08

Fri, 22 Jan 2021 12:35:25 -0800 

On Tue, Jan 19, 2021 at 1:43 AM Murray S. Kucherawy <[email protected]>
wrote:

> In the interests of getting this document on its way, I'd like to suggest
> the following edits in response to Dale's most recent message.  If the
> working group concurs, we can finally get this out to Last Call.
>
> My goal as an AD here is just to get the GenART feedback addressed, but
> the text is being submitted as a WG contribution for discussion and
> consensus consideration, not as a demand.   Please process accordingly; I
> believe the agreement is to do another WGLC on the document before it goes
> on its way, so the sooner consensus is reached on all of this, the sooner
> it goes.
>
> First, a suggestion of my own that I think I saw elsewhere, but it's not
> in Dale's reply: In several places there's a reference to "DMARC
> [RFC7489]".  That's appropriate the first time the reference is made, but I
> think after that you can just say "DMARC" when referring to the protocol
> generally, or to "RFC 7489" when you need to make a specific section or
> text reference.  They don't need to appear together everywhere.
>
> I think Dave's original feedback has been addressed -- good stuff -- so
> here are my suggestions around what's left:
>
> On Mon, Nov 16, 2020 at 7:16 PM Dale R. Worley <[email protected]> wrote:
>
>> My apologies for not tending to this promptly.
>>
>> In regard to the description of the experiments, the result criteria are
>> rather subjective, but I don't see that as a problem.  It does seem to
>> me that the title "PSD DMARC Privacy Concern Mitigation Experiment" is
>> too narrow, as only the 3rd experiment seems to be about privacy
>> issues.  A title as generic as "PSD DMARC Experiments" would be fine.
>>
>
> That's OK with me, or "DMARC PSD Experiments" or "DMARC PSD Experiment" if
> we want to treat it all as one common thing.
>
>
>> Although I note that even the -09 does not define "PSD", only "longest
>> PSD", even though "PSD" is used in section 2.5.  I suspect that PSD is
>> equal to "PSO Controlled Domain Name", though, or rather to some related
>> set of them.  That needs to be cleaned up in some way.
>>
>
> PSD appears to be well defined in Section 2.2.
>
> In section 3.5 and later there is the phrase "[this document] longest
>> PSD".  I'm not sure, but I think this is supposed to be "longest PSD
>> ([this document] section NN.NN)".
>>
>
> Agreed.
>
> I believe that my strongest critique was that section 1 is difficult to
>> understand if one does not already understand DMARC, and it does not
>> seem that the section has been revised.  Re-reading it, I notice that it
>> says "DMARC leverages public suffix lists to determine which domains are
>> organizational domains."  Ignoring that I dislike this use of
>> "leverage", a critical point is that it takes the existence of public
>> suffix lists a priori -- indeed, this use of "leverage" generally means
>> that the leveraged thing already exists and one is now extracting
>> additional benefit from that.  Whereas I've never heard of public suffix
>> lists and would naively expect that they are difficult to create and
>> maintain.  It might be better to say "DMARC uses public suffix lists to
>> determine which domains are organizational domains.  Public suffix lists
>> are obtained/maintained/distributed by ..."
>>
>
> Replace all of Section 1 with this (ignore funny line wrapping):
>
>    DMARC [RFC7489 <https://tools.ietf.org/html/rfc7489>] provides a mechanism 
> for publishing organizational
>    policy information to email receivers.  DMARC allows policy to be
>    specified for both individual domains and for organizational domains
>    and their sub-domains within a single organization.
>
>    To determine the organizational domain for a message under evaluation,
>    and thus where to look for a policy statement, DMARC makes use of a Public 
> Suffix List.
>    The process for doing this can be found in Section 3.2 of the DMARC 
> specification.
>
>    DMARC as specified presumes that domain names present in a PSL are not
>    organizational domains and thus not subject to DMARC processing; domains
>    are either organizational domains, sub-domains of organizational
>    domains, or listed on a PSL.  For domains listed in a
>    PSL, i.e., TLDs and domains that exist between TLDs and
>    organization level domains, policy can only be published for the
>    exact domain.  No method is available for these domains to express
>    policy or receive feedback reporting for sub-domains.  This missing
>    method allows for the abuse of non-existent organizational-level
>    domains and prevents identification of domain abuse in email.
>
>    This document specifies experimental updates to the DMARC and PSL 
> algorithm cited
>    above, in an attempt to mitigate this abuse.
>
>
Done

>
> Looking at the second paragraph of section 1, I notice that despite all
>> the special terms for classifying domain names in section 2, the example
>> in this section does not describe which of the domain names that it
>> mentions fall into which of these classes.  E.g. "tax.gov.example" is
>> said to be registered, but it looks like it is also the organizational
>> domain, and "gov.example" is its longest PSD.  It would also help to
>> mention that "tax.gov.example" is "registered at" "gov.example" to
>> introduce the details of the usage "registered at".
>>
>>     Suppose there exists a domain "tax.gov.example" (registered at
>>     "gov.example") ...
>>
>
> Introduce a new Section 1.1: "Example" with this:
>
>    As an example, imagine a country code TLD (ccTLD) which has public
>    subdomains for government and commercial use (".gov.example" and
>    ".com.example").  A PSL whose maintainer is aware of this country's domain 
> structure
>    would include entries for both of these in the PSL, indicating that they 
> are
>    PSDs below which registrations can occur.  Suppose further that there 
> exists a domain
>    "tax.gov.example", registered within ".gov.example", that is
>    responsible for taxation in this imagined
>    country.
>
>    However, by exploiting the typically unauthenticated nature
>    of email, there are regular malicious campaigns to impersonate this
>    organization that use similar-looking ("cousin") domains such as
>    "t4x.gov.example".  Such domains are not registered.
>
>    Within the
>    ".gov.example" public suffix, use of DMARC has been mandated, so
>    "gov.example" publishes the following DMARC DNS record:
>
>    [remainder of -09's page 3, the example, unchanged]
>
>
done

> Introduce a new Section 1.2: "Discussion" comprising the remainder of -09's 
> Section 1.  In the first paragraph, between "simple" and "extension", add 
> "experimental".
>
> A suggestion for 2.4:
>
> NEW:
>
> The longest PSD is the Organizational Domain with one label removed.  It 
> names the immediate parent node of the Organizational Domain in the DNS 
> namespace tree.
>
>
Done

I also changed the title to "Experimental DMARC Extension for Public Suffix
Domains"

I need to go over the next batch.

I have the XML in my repo:
https://github.com/moonshiner/draft-ietf-dmarc-psd/
and will send a pull request when i've gone back over things.

I do attach the rfcdiff I created locally for folks.  that may help

big thanks Murray
Title: Diff: f.out - draft-ietf-dmarc-psd-09.txt
 f.out   draft-ietf-dmarc-psd-09.txt 
Network Working Group S. Kitterman Network Working Group S. Kitterman
Internet-Draft fTLD Registry Services Internet-Draft fTLD Registry Services
Intended status: Experimental September 1, 2020 Intended status: Experimental September 22, 2020
Expires: March 5, 2021 Expires: March 26, 2021
Experimental DMARC Extension For Public Suffix Domains DMARC (Domain-based Message Authentication, Reporting, and Conformance)
Extension For PSDs (Public Suffix Domains)
draft-ietf-dmarc-psd-09 draft-ietf-dmarc-psd-09
Abstract Abstract
DMARC (Domain-based Message Authentication, Reporting, and DMARC (Domain-based Message Authentication, Reporting, and
Conformance) is a scalable mechanism by which a mail-originating Conformance) is a scalable mechanism by which a mail-originating
organization can express domain-level policies and preferences for organization can express domain-level policies and preferences for
message validation, disposition, and reporting, that a mail-receiving message validation, disposition, and reporting, that a mail-receiving
organization can use to improve mail handling. The design of DMARC organization can use to improve mail handling. The design of DMARC
presumes that domain names represent either nodes in the tree below presumes that domain names represent either nodes in the tree below
skipping to change at page 1, line 48 skipping to change at page 1, line 49
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 5, 2021. This Internet-Draft will expire on March 26, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Discussion . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Definitions . . . . . . . . . . . . . . . . . 5 2. Terminology and Definitions . . . . . . . . . . . . . . . . . 5
2.1. Conventions Used in This Document . . . . . . . . . . . . 5 2.1. Conventions Used in This Document . . . . . . . . . . . . 5
2.2. Public Suffix Domain (PSD) . . . . . . . . . . . . . . . 5 2.2. Public Suffix Domain (PSD) . . . . . . . . . . . . . . . 5
2.3. Organizational Domain . . . . . . . . . . . . . . . . . . 6 2.3. Organizational Domain . . . . . . . . . . . . . . . . . . 5
2.4. Longest PSD . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Longest PSD . . . . . . . . . . . . . . . . . . . . . . . 5
2.5. Public Suffix Operator (PSO) . . . . . . . . . . . . . . 6 2.5. Public Suffix Operator (PSO) . . . . . . . . . . . . . . 6
2.6. PSO Controlled Domain Names . . . . . . . . . . . . . . . 6 2.6. PSO Controlled Domain Names . . . . . . . . . . . . . . . 6
2.7. Non-existent Domains . . . . . . . . . . . . . . . . . . 6 2.7. Non-existent Domains . . . . . . . . . . . . . . . . . . 6
3. PSD DMARC Updates to DMARC Requirements . . . . . . . . . . . 6 3. PSD DMARC Updates to DMARC Requirements . . . . . . . . . . . 6
3.1. General Updates . . . . . . . . . . . . . . . . . . . . . 7 3.1. General Updates . . . . . . . . . . . . . . . . . . . . . 6
3.2. Changes in Section 6.3 "General Record Format" . . . . . 7 3.2. Changes in Section 6.3 "General Record Format" . . . . . 6
3.3. Changes in Section 6.5 "Domain Owner Actions" . . . . . . 7 3.3. Changes in Section 6.5 "Domain Owner Actions" . . . . . . 7
3.4. Changes in Section 6.6.1 "Extract Author Domain" . . . . 7 3.4. Changes in Section 6.6.1 "Extract Author Domain" . . . . 7
3.5. Changes in Section 6.6.3 "Policy Discovery" . . . . . . . 8 3.5. Changes in Section 6.6.3 "Policy Discovery" . . . . . . . 7
3.6. Changes in Section 7 "DMARC Feedback" . . . . . . . . . . 8 3.6. Changes in Section 7 "DMARC Feedback" . . . . . . . . . . 8
4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 8 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 8
4.1. Feedback leakage . . . . . . . . . . . . . . . . . . . . 9 4.1. Feedback leakage . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. Subdomain Policy Tag . . . . . . . . . . . . . . . . . . 10 6.1. Subdomain Policy Tag . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. PSD DMARC Privacy Concern Mitigation Experiment . . 12 Appendix A. PSD DMARC Privacy Concern Mitigation Experiment . . 11
Appendix B. DMARC PSD Registry Examples . . . . . . . . . . . . 12 Appendix B. DMARC PSD Registry Examples . . . . . . . . . . . . 12
B.1. DMARC PSD DNS Query Service . . . . . . . . . . . . . . . 12 B.1. DMARC PSD DNS Query Service . . . . . . . . . . . . . . . 12
B.2. DMARC Public Suffix Domain (PSD) Registry . . . . . . . . 12 B.2. DMARC Public Suffix Domain (PSD) Registry . . . . . . . . 12
B.3. DMARC PSD PSL Extension . . . . . . . . . . . . . . . . . 13 B.3. DMARC PSD PSL Extension . . . . . . . . . . . . . . . . . 13
Appendix C. Implementations . . . . . . . . . . . . . . . . . . 13 Appendix C. Implementations . . . . . . . . . . . . . . . . . . 13
C.1. Authheaders Module . . . . . . . . . . . . . . . . . . . 13 C.1. Authheaders Module . . . . . . . . . . . . . . . . . . . 13
C.2. Zdkimfilter Module . . . . . . . . . . . . . . . . . . . 14 C.2. Zdkimfilter Module . . . . . . . . . . . . . . . . . . . 13
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
DMARC [RFC7489] provides a mechanism for publishing organizational DMARC [RFC7489] provides a mechanism for publishing organizational
policy information to email receivers. DMARC allows policy to be policy information to email receivers. DMARC allows policy to be
specified for both individual domains and for organizational domains specified for both individual domains and for organizational domains
and their sub-domains within a single organization. and their sub-domains within a single organization. DMARC leverages
public suffix lists to determine which domains are organizational
To determine the organizational domain for a message under domains. It presumes that public suffix list listed domains are not
evaluation, and thus where to look for a policy statement, DMARC organizational domains and not subject to DMARC processing; domains
makes use of a Public Suffix List. The process for doing this can be are either organizational domains, sub-domains of organizational
found in Section 3.2 of the DMARC specification. domains, or listed on a public suffix list. For domains listed in a
public suffix list, i.e. TLDs and domains that exist between TLDs and
DMARC as specified presumes that domain names present in a PSL are organization level domains, policy can only be published for the
not organizational domains and thus not subject to DMARC processing; exact domain. No method is available for these domains to express
domains are either organizational domains, sub-domains of policy or receive feedback reporting for sub-domains. This missing
organizational domains, or listed on a PSL. For domains listed in a method allows for the abuse of non-existent organizational-level
PSL, i.e., TLDs and domains that exist between TLDs and organization domains and prevents identification of domain abuse in email.
level domains, policy can only be published for the exact domain. No
method is available for these domains to express policy or receive
feedback reporting for sub-domains. This missing method allows for
the abuse of non-existent organizational-level domains and prevents
identification of domain abuse in email.
This document specifies experimental updates to the DMARC and PSL
algorithm cited above, in an attempt to mitigate this abuse.
1.1. Example
As an example, imagine a country code TLD (ccTLD) which has public As an example, imagine a country code TLD (ccTLD) which has public
subdomains for government and commercial use (".gov.example" and subdomains for government and commercial use (.gov.example and
".com.example"). A PSL whose maintainer is aware of this country's .com.example). Suppose there exists a registered domain
domain structurewould include entries for both of these in the PSL, "tax.gov.example" that is responsible for taxation in this imagined
indicating that they are PSDs below which registrations can occur. country. However, by exploiting the typically unauthenticated nature
Suppose further that there exists a domain "tax.gov.example", of email, there are regular malicious campaigns to impersonate this
registered within ".gov.example", that is responsible for taxation in
this imagined country.
However, by exploiting the typically unauthenticated nature of email,
there are regular malicious campaigns to impersonate this
organization that use similar-looking ("cousin") domains such as organization that use similar-looking ("cousin") domains such as
"t4x.gov.example". Such domains are not registered. "t4x.gov.example". These domains are not registered. Within the
".gov.example" public suffix, use of DMARC has been mandated, so
Within the ".gov.example" public suffix, use of DMARC has been "gov.example" publishes the following DMARC DNS record:
mandated, so "gov.example" publishes the following DMARC DNS record:
_dmarc.gov.example. IN TXT ( "v=DMARC1; p=reject; " _dmarc.gov.example. IN TXT ( "v=DMARC1; p=reject; "
"rua=mailto:[email protected]" ) "rua=mailto:[email protected]" )
This DMARC record provides policy and a reporting destination for This DMARC record provides policy and a reporting destination for
mail sent from @gov.example. However, due to DMARC's current method mail sent from @gov.example. However, due to DMARC's current method
of discovering and applying policy at the organizational domain of discovering and applying policy at the organizational domain
level, the non-existent organizational domain of @t4x.gov.example level, the non-existent organizational domain of @t4x.gov.example
does not and cannot fall under a DMARC policy. does not and cannot fall under a DMARC policy.
Defensively registering all variants of "tax" is obviously not a Defensively registering all variants of "tax" is obviously not a
scalable strategy. The intent of this specification, therefore, is scalable strategy. The intent of this specification, therefore, is
to enhance the DMARC algorithm by enabling an agent receiving such a to enhance the DMARC algorithm by enabling an agent receiving such a
message to be able to determine that a relevant policy is present at message to be able to determine that a relevant policy is present at
"gov.example", which is precluded by the current DMARC algorithm. "gov.example", which is precluded by the current DMARC algorithm.
1.2. Discussion
This document provides a simple extension to DMARC [RFC7489] to allow This document provides a simple extension to DMARC [RFC7489] to allow
operators of Public Suffix Domains (PSDs) to: operators of Public Suffix Domains (PSDs) to:
o Express policy at the level of the PSD that covers all o Express policy at the level of the PSD that covers all
organizational domains that do not explicitly publish DMARC organizational domains that do not explicitly publish DMARC
records records
o Extends the DMARC policy query functionality to detect and process o Extends the DMARC policy query functionality to detect and process
such a policy such a policy
o Describes receiver feedback for such policies o Describes receiver feedback for such policies
o Provides controls to mitigate potential privacy considerations o Provides controls to mitigate potential privacy considerations
associated with this extension associated with this extension
This document also provides a new DMARC tag to indicate requested This document also provides a new DMARC [RFC7489] tag to indicate
handling policy for non-existent subdommains. This is provided requested handling policy for non-existent subdommains. This is
specifically to support phased deployment of PSD DMARC, but is provided specifically to support phased deployment of PSD DMARC, but
expected to be useful more generally. Undesired rejection risks for is expected to be useful more generally. Undesired rejection risks
mail purporting to be from domains that do not exist are for mail purporting to be from domains that do not exist are
substantially lower than for those that do, so the operational risk substantially lower than for those that do, so the operational risk
of requesting harsh policy treatment (e.g. reject) is lower. of requesting harsh policy treatment (e.g. reject) is lower.
As an additional benefit, the PSD DMARC extension clarifies existing As an additional benefit, the PSD DMARC extension clarifies existing
requirements. Based on the requirements of DMARC [RFC7489], DMARC requirements. Based on the requirements of DMARC [RFC7489], DMARC
should function above the organizational level for exact domain should function above the organizational level for exact domain
matches (i.e. if a DMARC record were published for 'example', then matches (i.e. if a DMARC record were published for 'example', then
mail from example@example should be subject to DMARC processing). mail from example@example should be subject to DMARC processing).
Testing had revealed that this is not consistently applied in Testing had revealed that this is not consistently applied in
different implementations. different implementations.
There are two types of Public Suffix Operators (PSOs) for which this There are two types of Public Suffix Operators (PSOs) for which this
extension would be useful and appropriate: extension would be useful and appropriate:
o Branded PSDs (e.g., ".google"): These domains are effectively o Branded PSDs (e.g., ".google"): These domains are effectively
Organizational Domains as discussed in DMARC [RFC7489]. They Organizational Domains as discussed in DMARC [RFC7489]. They
control all subdomains of the tree. These are effectively private control all subdomains of the tree. These are effectively private
domains, but listed in the Public Suffix List. They are treated domains, but listed in the Public Suffix List. They are treated
skipping to change at page 5, line 26 skipping to change at page 5, line 5
as DMARC Organizational Domains, but are currently unable to as DMARC Organizational Domains, but are currently unable to
benefit from DMARC. benefit from DMARC.
o Multi-organization PSDs that require DMARC usage (e.g., ".bank"): o Multi-organization PSDs that require DMARC usage (e.g., ".bank"):
Because existing Organizational Domains using this PSD have their Because existing Organizational Domains using this PSD have their
own DMARC policy, the applicability of this extension is for non- own DMARC policy, the applicability of this extension is for non-
existent domains. The extension allows the brand protection existent domains. The extension allows the brand protection
benefits of DMARC to extend to the entire PSD, including cousin benefits of DMARC to extend to the entire PSD, including cousin
domains of registered organizations. domains of registered organizations.
Due to the design of DMARC and the nature of the Internet email Due to the design of DMARC [RFC7489] and the nature of the Internet
architecture [RFC5598], there are interoperability issues associated email architecture [RFC5598], there are interoperability issues
with DMARC [RFC7489] deployment. These are discussed in associated with DMARC [RFC7489] deployment. These are discussed in
Interoperability Issues between DMARC and Indirect Email Flows Interoperability Issues between DMARC and Indirect Email Flows
[RFC7960]. These issues are not typically applicable to PSDs, since [RFC7960]. These issues are not typically applicable to PSDs, since
they (e.g., the ".gov.example" used above) do not typically send they (e.g., the ".gov.example" used above) do not typically send
mail. mail.
2. Terminology and Definitions 2. Terminology and Definitions
This section defines terms used in the rest of the document. This section defines terms used in the rest of the document.
2.1. Conventions Used in This Document 2.1. Conventions Used in This Document
skipping to change at page 6, line 23 skipping to change at page 6, line 4
PSD. PSD.
2.3. Organizational Domain 2.3. Organizational Domain
The term Organizational Domains is defined in DMARC [RFC7489] The term Organizational Domains is defined in DMARC [RFC7489]
Section 3.2. Section 3.2.
2.4. Longest PSD 2.4. Longest PSD
The longest PSD is the Organizational Domain with one label removed. The longest PSD is the Organizational Domain with one label removed.
It names the immediate parent node of the Organizational Domain in
the DNS namespace tree.
2.5. Public Suffix Operator (PSO) 2.5. Public Suffix Operator (PSO)
A Public Suffix Operator is an organization which manages operations A Public Suffix Operator is an organization which manages operations
within a PSD, particularly the DNS records published for names at and within a PSD, particularly the DNS records published for names at and
under that domain name. under that domain name.
2.6. PSO Controlled Domain Names 2.6. PSO Controlled Domain Names
PSO Controlled Domain Names are names in the DNS that are managed by PSO Controlled Domain Names are names in the DNS that are managed by
skipping to change at page 6, line 47 skipping to change at page 6, line 26
".co.uk") name components, depending on PSD policy. ".co.uk") name components, depending on PSD policy.
2.7. Non-existent Domains 2.7. Non-existent Domains
For DMARC purposes, a non-existent domain is a domain for which there For DMARC purposes, a non-existent domain is a domain for which there
is an NXDOMAIN or NODATA response for A, AAAA, and MX records. This is an NXDOMAIN or NODATA response for A, AAAA, and MX records. This
is a broader definition than that in NXDOMAIN [RFC8020]. is a broader definition than that in NXDOMAIN [RFC8020].
3. PSD DMARC Updates to DMARC Requirements 3. PSD DMARC Updates to DMARC Requirements
This document updates DMARC as follows: This document updates DMARC [RFC7489] as follows:
3.1. General Updates 3.1. General Updates
References to "Domain Owners" also apply to PSOs. References to "Domain Owners" also apply to PSOs.
3.2. Changes in Section 6.3 "General Record Format" 3.2. Changes in Section 6.3 "General Record Format"
A new tag is added after "fo": A new tag is added after "fo":
np: Requested Mail Receiver policy for non-existent subdomains np: Requested Mail Receiver policy for non-existent subdomains
(plain-text; OPTIONAL). Indicates the policy to be enacted by the (plain-text; OPTIONAL). Indicates the policy to be enacted by the
Receiver at the request of the Domain Owner. It applies only to Receiver at the request of the Domain Owner. It applies only to
non-existent subdomains of the domain queried and not to either non-existent subdomains of the domain queried and not to either
existing subdomains or the domain itself. Its syntax is identical existing subdomains or the domain itself. Its syntax is identical
to that of the "p" tag defined below. If the 'np' tag is absent, to that of the "p" tag defined below. If the 'np' tag is absent,
the policy specified by the "sp" tag (if the 'sp' tag is present) the policy specified by the "sp" tag (if the 'sp' tag is present)
or the policy specified by the "p" tag, if the 'sp' tag is not or the policy specified by the "p" tag, if the 'sp' tag is not
present, MUST be applied for non-existent subdomains. Note that present, MUST be applied for non-existent subdomains. Note that
"np" will be ignored for DMARC records published on subdomains of "np" will be ignored for DMARC records published on subdomains of
Organizational Domains and PSDs due to the effect of the DMARC Organizational Domains and PSDs due to the effect of the DMARC
policy discovery mechanism described in DMARC Section 6.6.3. policy discovery mechanism described in DMARC [RFC7489]
Section 6.6.3.
The following tag definitions from DMARC are updated: The following tag definitions from DMARC [RFC7489] are updated:
p: The sentence 'Policy applies to the domain queried and to p: The sentence 'Policy applies to the domain queried and to
subdomains, unless subdomain policy is explicitly described using subdomains, unless subdomain policy is explicitly described using
the "sp" tag' is updated to read 'Policy applies to the domain the "sp" tag' is updated to read 'Policy applies to the domain
queried and to subdomains, unless subdomain policy is explicitly queried and to subdomains, unless subdomain policy is explicitly
described using the "sp" or "np" tags.' described using the "sp" or "np" tags.'
sp: The sentence 'If absent, the policy specified by the "p" tag sp: The sentence 'If absent, the policy specified by the "p" tag
MUST be applied for subdomains' is updated to read 'If both the MUST be applied for subdomains' is updated to read 'If both the
'sp' tag is absent and the 'np' tag is either absent or not 'sp' tag is absent and the 'np' tag is either absent or not
skipping to change at page 8, line 6 skipping to change at page 7, line 32
for doing so. See the [this document] experiment description for doing so. See the [this document] experiment description
(Appendix A). (Appendix A).
3.4. Changes in Section 6.6.1 "Extract Author Domain" 3.4. Changes in Section 6.6.1 "Extract Author Domain"
Experience with DMARC has shown that some implementations short- Experience with DMARC has shown that some implementations short-
circuit messages, bypassing DMARC policy application, when the domain circuit messages, bypassing DMARC policy application, when the domain
name extracted by the receiver (from the RFC5322.From) is on the name extracted by the receiver (from the RFC5322.From) is on the
public suffix list used by the receiver. This negates the capability public suffix list used by the receiver. This negates the capability
being created by this specification. Therefore, the following being created by this specification. Therefore, the following
paragraph is appended to Section 6.6.1 of DMARC: paragraph is appended to Section 6.6.1 of DMARC [RFC7489]:
Note that domain names that appear on a public suffix list are not Note that domain names that appear on a public suffix list are not
exempt from DMARC policy application and reporting. exempt from DMARC policy application and reporting.
3.5. Changes in Section 6.6.3 "Policy Discovery" 3.5. Changes in Section 6.6.3 "Policy Discovery"
A new step between step 3 and 4 is added: A new step between step 3 and 4 is added:
3A. If the set is now empty and the longest PSD (Section 2.4) of the 3A. If the set is now empty and the longest PSD (Section 2.4) of the
Organizational Domain is one that the receiver has determined is Organizational Domain is one that the receiver has determined is
 End of changes. 22 change blocks. 
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