draft-ietf-dmarc-psd-12.txt   draft-ietf-dmarc-psd-13.txt 
Network Working Group S. Kitterman Network Working Group S. Kitterman
Internet-Draft fTLD Registry Services Internet-Draft fTLD Registry Services
Intended status: Experimental T. Wicinski, Ed. Intended status: Experimental T. Wicinski, Ed.
Expires: October 14, 2021 April 12, 2021 Expires: October 3, 2021 April 1, 2021
Experimental DMARC Extension For Public Suffix Domains Experimental DMARC Extension For Public Suffix Domains
draft-ietf-dmarc-psd-12 draft-ietf-dmarc-psd-13
Abstract Abstract
Domain-based Message Authentication, Reporting, and Conformance Domain-based Message Authentication, Reporting, and Conformance
(DMARC) permits a domain-controlling organization to express domain- (DMARC) permits a domain-controlling organization to express domain-
level policies and preferences for message validation, disposition, level policies and preferences for message validation, disposition,
and reporting, which a mail-receiving organization can use to improve and reporting, which a mail-receiving organization can use to improve
mail handling. mail handling.
DMARC distinguishes the portion of a name that is a Public Suffix DMARC distinguishes the portion of a name that is a Public Suffix
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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 October 14, 2021. This Internet-Draft will expire on October 3, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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
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2.2. Public Suffix Domain (PSD) . . . . . . . . . . . . . . . 5 2.2. Public Suffix Domain (PSD) . . . . . . . . . . . . . . . 5
2.3. Organizational Domain . . . . . . . . . . . . . . . . . . 6 2.3. Organizational Domain . . . . . . . . . . . . . . . . . . 6
2.4. Longest PSD . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Longest PSD . . . . . . . . . . . . . . . . . . . . . . . 6
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 . . . . . . . . . . . . . . . . . . . . . 7
3.2. Changes in Section 6.3 "General Record Format" . . . . . 7 3.2. Changes in Section 6.3 "General Record Format" . . . . . 7
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" . . . . 8
3.5. Changes in Section 6.6.3 "Policy Discovery" . . . . . . . 8 3.5. Changes in Section 6.6.3 "Policy Discovery" . . . . . . . 8
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 . . . . . . . . . . . . . . . . . . . 9
4.1. Feedback leakage . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6.1. Subdomain Policy Tag . . . . . . . . . . . . . . . . . . 10 6.1. Subdomain Policy Tag . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . 11
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Appendix A. PSD DMARC Privacy Concern Mitigation Experiment . . 12 Appendix A. PSD DMARC Privacy Concern Mitigation Experiment . . 12
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 . . . . . . . . . . . . . . . 13
B.2. DMARC Public Suffix Domain (PSD) Registry . . . . . . . . 13 B.2. DMARC Public Suffix Domain (PSD) Registry . . . . . . . . 13
B.3. DMARC PSD PSL Extension . . . . . . . . . . . . . . . . . 13 B.3. DMARC PSD PSL Extension . . . . . . . . . . . . . . . . . 13
Appendix C. Implementations . . . . . . . . . . . . . . . . . . 13
Appendix C. Implementations . . . . . . . . . . . . . . . . . . 14
C.1. Authheaders Module . . . . . . . . . . . . . . . . . . . 14 C.1. Authheaders Module . . . . . . . . . . . . . . . . . . . 14
C.2. Zdkimfilter Module . . . . . . . . . . . . . . . . . . . 14 C.2. Zdkimfilter Module . . . . . . . . . . . . . . . . . . . 14
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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.
To determine the organizational domain for a message under To determine the organizational domain for a message under
evaluation, and thus where to look for a policy statement, DMARC 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 makes use of a public suffix list. The process for doing this can be
found in Section 3.2 of the DMARC specification. Currently the found in Section 3.2 of the DMARC specification. Currently, the
public suffix list being used is the most common one that is public suffix list being used is the most common one that is
maintained by the Mozilla Foundation and made public at maintained by the Mozilla Foundation and made public at
http://publicsuffix.org [1]. http://publicsuffix.org [1].
In the basic DMARC model, PSDs are not organizational domains and are In the basic DMARC model, Public Suffix Domains (PSDs) are not
thus not subject to DMARC processing. In DMARC, domains fall into organizational domains and are thus not subject to DMARC processing.
one of three categories: organizational domains, sub-domains of In DMARC, domains fall into one of three categories: organizational
organizational domains, or PSDs. A PSD can only publish DMARC policy domains, sub-domains of organizational domains, or PSDs. A PSD can
for itself, and not for any sub-domains under it. In some cases, only publish DMARC policy for itself, and not for any sub-domains
this limitation allows for the abuse of non-existent organizational- under it. In some cases, this limitation allows for the abuse of
level domains and hampers identification of domain abuse in email. non-existent organizational-level domains and hampers identification
of domain abuse in email.
This document specifies experimental updates to the DMARC This document specifies experimental updates to the DMARC
specification cited above, in an attempt to mitigate this abuse. specification cited above, in an attempt to mitigate this abuse.
1.1. Example 1.1. Example
As an example, imagine a Top-Level Domain (TLD), ".example", that has As an example, imagine a Top-Level Domain (TLD), ".example", that has
public subdomains for government and commercial use (".gov.example" public subdomains for government and commercial use (".gov.example"
and ".com.example"). The maintainer of a list of such a PSD and ".com.example"). The maintainer of a list of such a PSD
structure would include entries for both of these sub-domains, structure would include entries for both of these sub-domains,
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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 tag to indicate requested
handling policy for non-existent subdommains. This is provided handling policy for non-existent subdomains. This is provided
specifically to support phased deployment of PSD DMARC, but is specifically to support phased deployment of PSD DMARC, but is
expected to be useful more generally. Undesired rejection risks for expected to be useful more generally. Undesired rejection risks for
mail purporting to be from domains that do not exist are 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 [RFC7489], DMARC should requirements. Based on the requirements of [RFC7489], DMARC should
function above the organizational level for exact domain matches function above the organizational level for exact domain matches
(i.e. if a DMARC record were published for 'example', then mail from (i.e., if a DMARC record were published for "example", then mail from
example@example should be subject to DMARC processing). Testing had example@example should be subject to DMARC processing). Testing had
revealed that this is not consistently applied in different revealed that this is not consistently applied in different
implementations. 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 [RFC7489]. They control Organizational Domains as discussed in [RFC7489]. They control
all subdomains of the tree. These are effectively private all subdomains of the tree. These are effectively private
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2.2. Public Suffix Domain (PSD) 2.2. Public Suffix Domain (PSD)
The global Internet Domain Name System (DNS) is documented in The global Internet Domain Name System (DNS) is documented in
numerous Requests for Comment (RFC). It defines a tree of names numerous RFCs. It defines a tree of names starting with root, ".",
starting with root, ".", immediately below which are Top Level Domain immediately below which are Top Level Domain names such as ".com" and
names such as ".com" and ".us". The domain name structure consists ".us". The domain name structure consists of a tree of names, each
of a tree of names, each of which is made of a sequence of words of which is made of a sequence of words ("labels") separated by
("labels") separated by period characters. The root of the tree is period characters. The root of the tree is simply called ".". The
simply called ".". The Internet community at large, through Internet community at large, through processes and policies external
processes and policies external to this work, selects points in this to this work, selects points in this tree at which to register domain
tree at which to register domain names "owned" by independent names "owned" by independent organizations. Real-world examples are
organizations. Real-world examples are ".com", ".org", ".us", and ".com", ".org", ".us", and ".gov.uk". Names at which such
".gov.uk". Names at which such registrations occur are called Public registrations occur are called Public Suffix Domains (PSDs), and a
Suffix Domains (PSDs), and a registration consists of a label registration consists of a label selected by the registrant to which
selected by the registrant to which a desirable PSD is appended. For a desirable PSD is appended. For example, "ietf.org" is a registered
example, "ietf.org" is a registered domain name, and ".org" is its domain name, and ".org" is its PSD.
PSD.
2.3. Organizational Domain 2.3. Organizational Domain
The term Organizational Domains is defined in [RFC7489] Section 3.2. The term Organizational Domains is defined in [RFC7489] 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 It names the immediate parent node of the Organizational Domain in
the DNS namespace tree. the DNS namespace tree.
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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
a PSO and are not available for use as Organizational Domains. PSO a PSO and are not available for use as Organizational Domains. PSO
Controlled Domain Names may have one (e.g., ".com") or more (e.g., Controlled Domain Names may have one (e.g., ".com") or more (e.g.,
".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 [RFC8020].
3. PSD DMARC Updates to DMARC Requirements 3. PSD DMARC Updates to DMARC Requirements
This document updates DMARC as follows: To participate in this experiment, implementations should interept
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": If this experiment is successful, this paragraph is added to this
setion. 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 Section 6.6.3.
The following tag definitions from DMARC are updated: The following tag definitions from DMARC 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
applicable, the policy specified by the "p" tag MUST be applied applicable, the policy specified by the "p" tag MUST be applied
for subdomains. for subdomains.
3.3. Changes in Section 6.5 "Domain Owner Actions" 3.3. Changes in Section 6.5 "Domain Owner Actions"
In addition to the DMARC domain owner actions, PSOs that require use In addition to the DMARC domain owner actions, PSOs that require use
of DMARC and participate in PSD DMARC ought to make that information of DMARC and participate in PSD DMARC ought to make that information
available to receivers. This document is an experimental mechanism available to receivers. This document is an experimental mechanism
for doing so. See the [this document] experiment description for doing so. See the [this document] experiment description
(Appendix A). (Appendix A).
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policy lookup at "_dmarc.compute.cloudcompany.com.example". policy lookup at "_dmarc.compute.cloudcompany.com.example".
Note: Because the PSD policy query comes after the Organizational Note: Because the PSD policy query comes after the Organizational
Domain policy query, PSD policy is not used for Organizational Domain policy query, PSD policy is not used for Organizational
domains that have published a DMARC policy. Specifically, this is domains that have published a DMARC policy. Specifically, this is
not a mechanism to provide feedback addresses (RUA/RUF) when an not a mechanism to provide feedback addresses (RUA/RUF) when an
Organizational Domain has declined to do so. Organizational Domain has declined to do so.
3.6. Changes in Section 7 "DMARC Feedback" 3.6. Changes in Section 7 "DMARC Feedback"
If this experiment is successful, this paragraph is added to this
setion.
Operational note for PSD DMARC: For PSOs, feedback for non-existent Operational note for PSD DMARC: For PSOs, feedback for non-existent
domains is desirable and useful, just as it is for org-level DMARC domains is desirable and useful, just as it is for org-level DMARC
operators. See Section 4 of [this document] for discussion of operators. See Section 4 of [this document] for discussion of
Privacy Considerations for PSD DMARC. Privacy Considerations for PSD DMARC.
4. Privacy Considerations 4. Privacy Considerations
These privacy considerations are developed based on the requirements These privacy considerations are developed based on the requirements
of [RFC6973]. Additionally, the Privacy Considerations of [RFC7489] of [RFC6973]. Additionally, the Privacy Considerations of [RFC7489]
apply to the mechanisms described by this document. apply to the mechanisms described by this document. If this
experiment is successful, this section should be incorporated into
4.1. Feedback leakage the Privacy Considerations section as "Feedback leakage".
Providing feedback reporting to PSOs can, in some cases, cause Providing feedback reporting to PSOs can, in some cases, cause
information to leak out of an organization to the PSO. This leakage information to leak out of an organization to the PSO. This leakage
could potentially be utilized as part of a program of pervasive could potentially be utilized as part of a program of pervasive
surveillance (See [RFC7624]). There are roughly three cases to surveillance (See [RFC7624]). There are roughly three cases to
consider: consider:
o Single Organization PSDs (e.g., ".google"), RUA and RUF reports o Single Organization PSDs (e.g., ".google"), RUA and RUF reports
based on PSD DMARC have the potential to contain information about based on PSD DMARC have the potential to contain information about
emails related to entities managed by the organization. Since emails related to entities managed by the organization. Since
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hosts) will be used. The only direct feedback leakage risk for hosts) will be used. The only direct feedback leakage risk for
these PSDs are for Organizational Domains that are out of these PSDs are for Organizational Domains that are out of
compliance with PSD policy. Data on non-existent cousin domains compliance with PSD policy. Data on non-existent cousin domains
would be sent to the PSO. would be sent to the PSO.
o Multi-organization PSDs (e.g., ".com") that do not mandate DMARC o Multi-organization PSDs (e.g., ".com") that do not mandate DMARC
usage: Privacy risks for Organizational Domains that have not usage: Privacy risks for Organizational Domains that have not
deployed DMARC within such PSDs are significant. For non-DMARC deployed DMARC within such PSDs are significant. For non-DMARC
Organizational Domains, all DMARC feedback will be directed to the Organizational Domains, all DMARC feedback will be directed to the
PSO. PSD DMARC is opt-out (by publishing a DMARC record at the PSO. PSD DMARC is opt-out (by publishing a DMARC record at the
Organizational Domain level) vice opt-in, which would be the more Organizational Domain level) instead of opt-in, which would be the
desirable characteristic. This means that any non-DMARC more desirable characteristic. This means that any non-DMARC
organizational domain would have its feedback reports redirected organizational domain would have its feedback reports redirected
to the PSO. The content of such reports, particularly for to the PSO. The content of such reports, particularly for
existing domains, is privacy sensitive. existing domains, is privacy sensitive.
PSOs will receive feedback on non-existent domains, which may be PSOs will receive feedback on non-existent domains, which may be
similar to existing Organizational Domains. Feedback related to such similar to existing Organizational Domains. Feedback related to such
cousin domains have a small risk of carrying information related to cousin domains have a small risk of carrying information related to
an actual Organizational Domain. To minimize this potential concern, an actual Organizational Domain. To minimize this potential concern,
PSD DMARC feedback MUST be limited to Aggregate Reports. Feedback PSD DMARC feedback MUST be limited to Aggregate Reports. Feedback
Reports carry more detailed information and present a greater risk. Reports carry more detailed information and present a greater risk.
Due to the inherent Privacy and Security risks associated with PSD Due to the inherent Privacy and Security risks associated with PSD
DMARC for Organizational Domains in multi-organization PSDs that do DMARC for Organizational Domains in multi-organization PSDs that do
not particpate in DMARC, any Feedback Reporting related to multi- not participate in DMARC, any Feedback Reporting related to multi-
organizational PSDs MUST be limited to non-existent domains except in organizational PSDs MUST be limited to non-existent domains except in
cases where the reporter knows that PSO requires use of DMARC. cases where the reporter knows that PSO requires use of DMARC (by
checking the DMARC PSD Registry).
5. Security Considerations 5. Security Considerations
This document does not change the Security Considerations of This document does not change the Security Considerations of
[RFC7489] and [RFC7960]. [RFC7489] and [RFC7960].
The risks of the issues identified in [RFC7489], Section 12.3, DNS The risks of the issues identified in [RFC7489], Section 12.3, DNS
Security, are amplified by PSD DMARC. In particular, DNS cache Security, are amplified by PSD DMARC. In particular, DNS cache
poisoning (or Name Chaining), see [RFC3833] for details, consequences poisoning (or Name Chaining), see [RFC3833] for details, consequences
are increased because a successful attack would potentially have a are increased because a successful attack would potentially have a
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detail in Section 4. detail in Section 4.
6. IANA Considerations 6. IANA Considerations
This section describes actions requested to be completed by IANA. This section describes actions requested to be completed by IANA.
6.1. Subdomain Policy Tag 6.1. Subdomain Policy Tag
IANA is requested to add a new tag to DMARC Tag Registry in the IANA is requested to add a new tag to DMARC Tag Registry in the
Domain-based Message Authentication, Reporting, and Conformance Domain-based Message Authentication, Reporting, and Conformance
(DMARC) Parameters Registry. (DMARC) Parameters Registry. The "Status" column is defined in
[RFC7489]Section 11.4.
The entry is as follows: The entry is as follows:
+----------+-----------+---------+-------------------------------+ +----------+-----------+---------+-------------------------------+
| Tag Name | Reference | Status | Description | | Tag Name | Reference | Status | Description |
+----------+-----------+---------+-------------------------------+ +----------+-----------+---------+-------------------------------+
| np | this | current | Requested handling policy for | | np | this | current | Requested handling policy for |
| | document | | non-existent subdomains | | | document | | non-existent subdomains |
+----------+-----------+---------+-------------------------------+ +----------+-----------+---------+-------------------------------+
[RFC EDITOR: Please replace "This document" with the RFC number of
this document.]
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based [RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based
skipping to change at page 13, line 13 skipping to change at page 13, line 20
service is described on the web site. service is described on the web site.
B.2. DMARC Public Suffix Domain (PSD) Registry B.2. DMARC Public Suffix Domain (PSD) Registry
[psddmarc.org] provides an IANA like DMARC Public Suffix Domain (PSD) [psddmarc.org] provides an IANA like DMARC Public Suffix Domain (PSD)
Registry as a stand-alone DNS query service. It follows the contents Registry as a stand-alone DNS query service. It follows the contents
and structure described below. There is a Comma Separated Value and structure described below. There is a Comma Separated Value
(CSV) version of the listed PSD domains which is suitable for use in (CSV) version of the listed PSD domains which is suitable for use in
build updates for PSD DMARC capable software. build updates for PSD DMARC capable software.
Names of PSDs participating in PSD DMARC must be registered this new PSDs that are deploying DMARC and are participating in PSD DMARC must
registry. New entries are assigned only for PSDs that require use of be register their public suffix domain in this new registry. The
DMARC. The requirement has to be documented in a manner that requirement has to be documented in a manner that satisfies the terms
satisfies the terms of Expert Review, per [RFC8126]. The Designated of Expert Review, per [RFC8126]. The Designated Expert needs to
Expert needs to confirm that provided documentation adequately confirm that provided documentation adequately describes PSD policy
describes PSD policy to require domain owners to use DMARC or that to require domain owners to use DMARC or that all domain owners are
all domain owners are part of a single organization with the PSO. part of a single organization with the PSO.
The initial set of entries in this registry is as follows: The initial set of entries in this registry is as follows:
+-------------+---------------+ +-------------+---------------+
| PSD | Status | | PSD | Status |
+-------------+---------------+ +-------------+---------------+
| .bank | current | | .bank | current |
+-------------+---------------+ +-------------+---------------+
| .insurance | current | | .insurance | current |
+-------------+---------------+ +-------------+---------------+
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+-------------+---------------+ +-------------+---------------+
B.3. DMARC PSD PSL Extension B.3. DMARC PSD PSL Extension
[psddmarc.org] provides a file formatted like the Public Suffix List [psddmarc.org] provides a file formatted like the Public Suffix List
(PSL) in order to facilitate identification of PSD DMARC (PSL) in order to facilitate identification of PSD DMARC
participants. Contents are functionally identical to the IANA like participants. Contents are functionally identical to the IANA like
registry, but presented in a different format. registry, but presented in a different format.
When using this approach, the input domain of the extension lookup is When using this approach, the input domain of the extension lookup is
supposed to be the output domain of the regular PSL lookup, i.e. the supposed to be the output domain of the regular PSL lookup, i.e., the
organizational domain. This alternative data approach is potentially organizational domain. This alternative data approach is potentially
useful since DMARC implementations already need to be able to parse useful since DMARC implementations already need to be able to parse
the data format, so it should be easier to implement. the data format, so it should be easier to implement.
Appendix C. Implementations Appendix C. Implementations
There are two known implementations of PSD DMARC available for There are two known implementations of PSD DMARC available for
testing. testing.
C.1. Authheaders Module C.1. Authheaders Module
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