draft-ietf-dmarc-arc-usage-06.txt   draft-ietf-dmarc-arc-usage-07.txt 
DMARC Working Group S. Jones, Ed. DMARC Working Group S. Jones, Ed.
Internet-Draft DMARC.org Internet-Draft DMARC.org
Intended status: Informational K. Andersen Intended status: Informational K. Andersen
Expires: April 25, 2019 LinkedIn Expires: October 25, 2019 LinkedIn
J. Rae-Grant April 23, 2019
Google
T. Adams
Paypal
October 22, 2018
Recommended Usage of the Authenticated Received Chain (ARC) Recommended Usage of the Authenticated Received Chain (ARC)
draft-ietf-dmarc-arc-usage-06 draft-ietf-dmarc-arc-usage-07
Abstract Abstract
The Authentication Received Chain (ARC) provides an authenticated The Authentication Received Chain (ARC) provides an authenticated
"chain of custody" for a message, allowing each entity that handles "chain of custody" for a message, allowing each entity that handles
the message to see what entities handled it before, and to see what the message to see what entities handled it before, and to see what
the message's authentication assessment was at each step in the the message's authentication assessment was at each step in the
handling. But the specification does not indicate how the entities handling. But the specification does not indicate how the entities
handling these messages should interpret or utilize ARC results in handling these messages should interpret or utilize ARC results in
making decisions about message disposition. This document will making decisions about message disposition. This document will
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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 April 25, 2019. This Internet-Draft will expire on October 25, 2019.
Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. How does ARC work? . . . . . . . . . . . . . . . . . . . . . 3 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. How does ARC work? . . . . . . . . . . . . . . . . . . . 3
2.2. What new headers are introduced by ARC? . . . . . . . . . 5
2.3. Does ARC support Internationalized Email (EAI)? . . . . . 5
2.4. Does ARC support multiple digital signature algorithms? . 5
3. Guidance for Receivers/Validators . . . . . . . . . . . . . . 5 3. Guidance for Receivers/Validators . . . . . . . . . . . . . . 5
3.1. What is the significance of an intact ARC chain? . . . . 5 3.1. What is the significance of an intact ARC chain? . . . . 5
3.2. What exactly is an "intact" ARC chain? . . . . . . . . . 5 3.2. What exactly is an "intact" ARC chain? . . . . . . . . . 6
3.3. What is the significance of an invalid ("broken") ARC 3.3. What is the significance of an invalid ("broken") ARC
chain? . . . . . . . . . . . . . . . . . . . . . . . . . 6 chain? . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.4. What does the absence of an ARC chain in a message mean? 6 3.4. What error code(s) should be returned if an invalid ARC
3.5. What reasonable conclusions can you draw based upon chain is detected during an SMTP transaction? . . . . . . 7
seeing lots of mail with ARC chains? . . . . . . . . . . 6 3.5. What does the absence of an ARC chain in a message mean? 7
3.6. What if none of the intermediaries have been seen 3.6. What reasonable conclusions can you draw based upon
previously? . . . . . . . . . . . . . . . . . . . . . . . 7 seeing lots of mail with ARC chains? . . . . . . . . . . 7
3.7. What about ARC chains where some intermediaries are known 3.7. What if none of the intermediaries have been seen
and others are not? . . . . . . . . . . . . . . . . . . . 7 previously? . . . . . . . . . . . . . . . . . . . . . . . 8
3.8. What should message handlers do when they detect 3.8. What about ARC chains where some intermediaries are known
malicious content in messages where ARC is present? . . . 7 and others are not? . . . . . . . . . . . . . . . . . . . 8
3.9. What feedback does a sender or domain owner get about ARC 3.9. What should message handlers do when they detect
when it is applied to their messages? . . . . . . . . . . 8 malicious content in messages where ARC is present? . . . 8
3.10. What prevents a malicious actor from removing the ARC 3.10. What feedback does a sender or domain owner get about ARC
when it is applied to their messages? . . . . . . . . . . 9
3.11. What prevents a malicious actor from removing the ARC
header fields, altering the content, and creating a new header fields, altering the content, and creating a new
ARC chain? . . . . . . . . . . . . . . . . . . . . . . . 8 ARC chain? . . . . . . . . . . . . . . . . . . . . . . . 9
4. Guidance for Intermediaries . . . . . . . . . . . . . . . . . 8 4. Guidance for Intermediaries . . . . . . . . . . . . . . . . . 9
4.1. What is an Intermediary under ARC? . . . . . . . . . . . 8 4.1. What is an Intermediary under ARC? . . . . . . . . . . . 9
4.2. What are the minimum requirements for an ARC 4.2. What are the minimum requirements for an ARC
Intermediary? . . . . . . . . . . . . . . . . . . . . . . 9 Intermediary? . . . . . . . . . . . . . . . . . . . . . . 10
4.2.1. More specifically a participating ARC intermediary 4.2.1. More specifically a participating ARC intermediary
must do the following: . . . . . . . . . . . . . . . 9 must do the following: . . . . . . . . . . . . . . . 10
4.3. Should every MTA be an ARC participant? . . . . . . . . . 9 4.3. Should every MTA be an ARC participant? . . . . . . . . . 10
4.4. What should an intermediary do in the case of an invalid 4.4. What should an intermediary do in the case of an invalid
or "broken" ARC chain? . . . . . . . . . . . . . . . . . 9 or "broken" ARC chain? . . . . . . . . . . . . . . . . . 10
4.5. What should I do in the case where there is no ARC chain 4.5. What should I do in the case where there is no ARC chain
present in a message? . . . . . . . . . . . . . . . . . . 10 present in a message? . . . . . . . . . . . . . . . . . . 11
4.6. How could ARC affect my reputation as an intermediary? . 10 4.6. How could ARC affect my reputation as an intermediary? . 11
4.7. What can I do to influence my reputation as an 4.7. What can I do to influence my reputation as an
intermediary? . . . . . . . . . . . . . . . . . . . . . . 10 intermediary? . . . . . . . . . . . . . . . . . . . . . . 11
5. Guidance for Originators . . . . . . . . . . . . . . . . . . 10
5.1. Where can I find out more information? . . . . . . . . . 10 5. Guidance for Originators . . . . . . . . . . . . . . . . . . 11
5.1. Where can I find out more information? . . . . . . . . . 11
5.2. How/where can I test interoperabililty for my 5.2. How/where can I test interoperabililty for my
implementation? . . . . . . . . . . . . . . . . . . . . . 11 implementation? . . . . . . . . . . . . . . . . . . . . . 12
5.3. How can ARC impact my email? . . . . . . . . . . . . . . 11 5.3. How can ARC impact my email? . . . . . . . . . . . . . . 12
5.4. How can ARC impact my reputation as a message sender? . . 11 5.4. How can ARC impact my reputation as a message sender? . . 12
5.5. Can I tell intermediaries not to use ARC? . . . . . . . . 11 5.5. Can I tell intermediaries not to use ARC? . . . . . . . . 13
6. Considerations . . . . . . . . . . . . . . . . . . . . . . . 12 6. Considerations . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. IANA Considerations . . . . . . . . . . . . . . . . . . . 12 6.1. IANA Considerations . . . . . . . . . . . . . . . . . . . 13
6.2. Security Considerations . . . . . . . . . . . . . . . . . 12 6.2. Security Considerations . . . . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. GLOSSARY . . . . . . . . . . . . . . . . . . . . . . 13 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Appendix B. References . . . . . . . . . . . . . . . . . . . . . 16 Appendix A. Glossary . . . . . . . . . . . . . . . . . . . . . . 15
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 16 Appendix B. References . . . . . . . . . . . . . . . . . . . . . 18
Appendix D. Comments and Feedback . . . . . . . . . . . . . . . 16 Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Appendix D. Comments and Feedback . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
[ARC] is intended to be used by Internet Mail Handlers who forward or [ARC] is intended to be used by Internet Mail Handlers who forward or
resend messages, with or without alterations, such that they will no resend messages, with or without alterations, such that they will no
longer pass the SPF [RFC7208], DKIM [RFC6376], and/or DMARC [RFC7489] longer pass the SPF [RFC7208], DKIM [RFC6376], and/or DMARC [RFC7489]
mechanisms when evaluated by subsequent message handlers or the final mechanisms when evaluated by subsequent message handlers or the final
recipient. In such cases ARC may provide useful information about recipient. In such cases ARC may provide useful information about
the message before the forwarding and/or alterations took place, and the message before the forwarding and/or alterations took place, and
recipients may choose to use this information to influence delivery recipients may choose to use this information to influence delivery
decisions. decisions.
2. How does ARC work? 2. Overview
2.1. How does ARC work?
Consider a message sent to a mailing list. Assume that the message Consider a message sent to a mailing list. Assume that the message
author's domain publishes an SPF record, signs messages with a DKIM author's domain publishes an SPF record, signs messages with a DKIM
signature that includes the RFC5322.Subject header and the message signature that includes the RFC5322.Subject header and the message
body, and publishes a DMARC policy of "p=reject". Finally, assume body, and publishes a DMARC policy of "p=reject". Finally, assume
that the final recipient(s) of the message implement SPF, DKIM and that the final recipient(s) of the message implement SPF, DKIM and
DMARC authentication checks on incoming messages. DMARC authentication checks on incoming messages.
This message is received by the ADMD hosting the Mailing List Manager This message is received by the ADMD hosting the Mailing List Manager
(MLM) software. Upon receipt from the message author's ADMD, the (MLM) software. Upon receipt from the message author's ADMD, the
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When the message reaches a list member's ADMD, the SPF and DKIM When the message reaches a list member's ADMD, the SPF and DKIM
results will still not pass the DMARC check. However if the results will still not pass the DMARC check. However if the
receiving ADMD implements ARC, it can check for and validate the ARC receiving ADMD implements ARC, it can check for and validate the ARC
chain in the message, and verify that the contents of the ARC- chain in the message, and verify that the contents of the ARC-
Authentication-Results header were conveyed intact from the MLM's Authentication-Results header were conveyed intact from the MLM's
ADMD. At that point the final recipient's ADMD might choose to use ADMD. At that point the final recipient's ADMD might choose to use
those authentication results in the decision whether or not to those authentication results in the decision whether or not to
deliver the message, even though it failed to pass conventional SPF, deliver the message, even though it failed to pass conventional SPF,
DKIM, and DMARC checks. DKIM, and DMARC checks.
2.2. What new headers are introduced by ARC?
The following new headers are defined in [ARC] Section 4.1, "ARC
Header Fields":
o ARC-Seal
o ARC-Message-Signature
o ARC-Athentication-Results
Each time a message passes through an ARC Intermediary, an ARC Set
consisting of these three headers will be attached to the message.
More information about ARC Sets can be found in [ARC] Section 4.2,
"ARC Set." The entire collection of ARC Sets in a message is
commonly referred to as the ARC Chain.
2.3. Does ARC support Internationalized Email (EAI)?
Changes to support EAI are inherited from DKIM [RFC6376] as updated
by [draft-levine-eaiauth], and Authentication-Results as updated in
[I-D-7601bis]. For more details, please refer to [ARC]
Section 4.1.4, "Internationalized Email (EAI)."
2.4. Does ARC support multiple digital signature algorithms?
Originally ARC only supported a single signing algorithm, but the
DCRUP working group https://datatracker.ietf.org/wg/dcrup/about [1]
is expanding the set of supported algorithms available to DKIM
[RFC6376] and derived protocols. [ARC-MULTI] is adapting this work
to extend [ARC] to support multiple algorithms.
3. Guidance for Receivers/Validators 3. Guidance for Receivers/Validators
3.1. What is the significance of an intact ARC chain? 3.1. What is the significance of an intact ARC chain?
An intact ARC chain conveys authentication results like SPF and DKIM An intact ARC chain conveys authentication results like SPF and DKIM
as observed by the first ARC participant. In cases where the message as observed by the first ARC participant. In cases where the message
no longer produces passing results for DKIM, SPF, or DMARC but an no longer produces passing results for DKIM, SPF, or DMARC but an
intact ARC chain is present, the message receiver may choose to use intact ARC chain is present, the message receiver may choose to use
the contents of the first ARC-Authentication-Results header field in the contents of the first ARC-Authentication-Results header field in
determining how to handle the message. determining how to handle the message.
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as if there was no ARC chain at all. For example, a message that as if there was no ARC chain at all. For example, a message that
fails under DMARC and has an invalid ARC chain would be subject to fails under DMARC and has an invalid ARC chain would be subject to
that DMARC policy, which may cause it to be quarantined or rejected. that DMARC policy, which may cause it to be quarantined or rejected.
Email transit can produce broken signatures for a wide variety of Email transit can produce broken signatures for a wide variety of
benign reasons. This includes possibly breaking one or more ARC benign reasons. This includes possibly breaking one or more ARC
signatures. Therefore, receivers need to be wary of ascribing motive signatures. Therefore, receivers need to be wary of ascribing motive
to such breakage, although patterns of common behaviour may provide to such breakage, although patterns of common behaviour may provide
some basis for adjusting local policy decisions. some basis for adjusting local policy decisions.
3.4. What does the absence of an ARC chain in a message mean? 3.4. What error code(s) should be returned if an invalid ARC chain is
detected during an SMTP transaction?
According to [ARC] Section 5.2.2, a Validator MAY signal the breakage
during the SMTP transaction by returning the extended SMTP response
code 5.7.29 "ARC validation failure" and corresponding SMTP basic
response code. Since ARC failures are likely the be detected due to
other, underlying authentication failures, Validators may also choose
to return the more general 5.7.26 "Multiple authentication checks
failed instead of the ARC-specific code.
3.5. What does the absence of an ARC chain in a message mean?
The absence of an ARC chain means nothing. ARC is intended to allow The absence of an ARC chain means nothing. ARC is intended to allow
a participating message handler to preserve certain authentication a participating message handler to preserve certain authentication
results when a message is being forwarded and/or modified such that results when a message is being forwarded and/or modified such that
the final recipient can evaluate this information. If they are the final recipient can evaluate this information. If they are
absent, there is nothing extra that ARC requires the final recipient absent, there is nothing extra that ARC requires the final recipient
to do. to do.
3.5. What reasonable conclusions can you draw based upon seeing lots of 3.6. What reasonable conclusions can you draw based upon seeing lots of
mail with ARC chains? mail with ARC chains?
With sufficient history, ARC can be used to augment DMARC With sufficient history, ARC can be used to augment DMARC
authentication policy (i.e. a message could fail DMARC, but validated authentication policy (i.e. a message could fail DMARC, but validated
ARC information and therefore could be considered as validly ARC information and therefore could be considered as validly
authenticated as reported by the first ARC participant). authenticated as reported by the first ARC participant).
If the validator does content analysis and reputation tracking, the If the validator does content analysis and reputation tracking, the
ARC participants in a message can be credited or discredited for good ARC participants in a message can be credited or discredited for good
or bad content. By analyzing different ARC chains involved in "bad" or bad content. By analyzing different ARC chains involved in "bad"
messages, a validator might identify malicious participating messages, a validator might identify malicious participating
intermediaries. intermediaries.
With a valid chain and good reputations for all ARC participants, With a valid chain and good reputations for all ARC participants,
receivers may choose to apply a "local policy override" to the DMARC receivers may choose to apply a "local policy override" to the DMARC
policy assertion for the domain authentication evaluation, depending policy assertion for the domain authentication evaluation, depending
on the ARC-Authentication-Results header field value. Normal content on the ARC-Authentication-Results header field value. Normal content
analysis should never be skipped. analysis should never be skipped.
3.6. What if none of the intermediaries have been seen previously? 3.7. What if none of the intermediaries have been seen previously?
This has no impact on the operation of ARC, as ARC is not a This has no impact on the operation of ARC, as ARC is not a
reputation system. ARC conveys the results of other authentication reputation system. ARC conveys the results of other authentication
mechanisms such that the participating message handlers can be mechanisms such that the participating message handlers can be
positively identified. Final message recipients may or may not positively identified. Final message recipients may or may not
choose to examine these results when messages fail other choose to examine these results when messages fail other
authentication checks. They are more likely to override, say, a authentication checks. They are more likely to override, say, a
failing DMARC result in the presence of an intact ARC chain where the failing DMARC result in the presence of an intact ARC chain where the
participating ARC message handlers have been observed to not convey participating ARC message handlers have been observed to not convey
"bad" content in the past, and the initial ARC participant indicates "bad" content in the past, and the initial ARC participant indicates
the message they received had passed authentication checks. the message they received had passed authentication checks.
3.7. What about ARC chains where some intermediaries are known and 3.8. What about ARC chains where some intermediaries are known and
others are not? others are not?
Validators may choose to build reputation models for ARC message Validators may choose to build reputation models for ARC message
handlers they have observed. Generally speaking it is more feasible handlers they have observed. Generally speaking it is more feasible
to accrue positive reputation to intermediaries when they to accrue positive reputation to intermediaries when they
consistently send messages that are evaluated positively in terms of consistently send messages that are evaluated positively in terms of
content and ARC chains. When messages are received with ARC chains content and ARC chains. When messages are received with ARC chains
that are not intact, it is very difficult identify which that are not intact, it is very difficult identify which
intermediaries may have manipulated the message or injected bad intermediaries may have manipulated the message or injected bad
content. content.
3.8. What should message handlers do when they detect malicious content 3.9. What should message handlers do when they detect malicious content
in messages where ARC is present? in messages where ARC is present?
Message handlers should do what they normally do when they detect Message handlers should do what they normally do when they detect
malicious content in a message - hopefully that means quarantining or malicious content in a message - hopefully that means quarantining or
discarding the message. ARC information should never make malicious discarding the message. ARC information should never make malicious
content acceptable. content acceptable.
In such cases it is difficult to determine where the malicious In such cases it is difficult to determine where the malicious
content may have been injected. What ARC can do in such cases is content may have been injected. What ARC can do in such cases is
verify that a given intermediary or message handler did in fact verify that a given intermediary or message handler did in fact
handle the message as indicated in the header fields. In such cases handle the message as indicated in the header fields. In such cases
a message recipient who maintains a reputation system about email a message recipient who maintains a reputation system about email
senders may wish to incorporate this information as an additional senders may wish to incorporate this information as an additional
factor in the score for the intermediaries and sender in question. factor in the score for the intermediaries and sender in question.
However reputation systems are very complex, and usually unique to However reputation systems are very complex, and usually unique to
those organizations operating them, and therefore beyond the scope of those organizations operating them, and therefore beyond the scope of
this document. this document.
3.9. What feedback does a sender or domain owner get about ARC when it 3.10. What feedback does a sender or domain owner get about ARC when it
is applied to their messages? is applied to their messages?
ARC itself does not include any mechanism for feedback or reporting. ARC itself does not include any mechanism for feedback or reporting.
It does however recommend that message receiving systems that use ARC It does however recommend that message receiving systems that use ARC
to augment their delivery decisions, who use DMARC and decide to to augment their delivery decisions, who use DMARC and decide to
deliver a message because of ARC information, should include a deliver a message because of ARC information, should include a
notation to that effect in their normal DMARC reports. These notation to that effect in their normal DMARC reports. These
notations would be easily identifiable by report processors, so that notations would be easily identifiable by report processors, so that
senders and domain owners can see where ARC is being used to augment senders and domain owners can see where ARC is being used to augment
the deliverability of their messages. the deliverability of their messages.
3.10. What prevents a malicious actor from removing the ARC header 3.11. What prevents a malicious actor from removing the ARC header
fields, altering the content, and creating a new ARC chain? fields, altering the content, and creating a new ARC chain?
ARC does not prevent a malicious actor from doing this. Nor does it ARC does not prevent a malicious actor from doing this. Nor does it
prevent a malicious actor from removing all but the first ADMD's ARC prevent a malicious actor from removing all but the first ADMD's ARC
header fields and altering the message, eliminating intervening header fields and altering the message, eliminating intervening
participants from the ARC chain. Or similar variations. participants from the ARC chain. Or similar variations.
A valid ARC chain does not provide any automatic benefit. With an A valid ARC chain does not provide any automatic benefit. With an
intact ARC chain, the final message recipient may choose to use the intact ARC chain, the final message recipient may choose to use the
contents of the ARC-Authentication-Results header field in contents of the ARC-Authentication-Results header field in
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A participating ARC intermediary must validate the ARC chain on a A participating ARC intermediary must validate the ARC chain on a
message it receives, if one is present. It then attaches its own ARC message it receives, if one is present. It then attaches its own ARC
seal and signature, including an indication if the chain failed to seal and signature, including an indication if the chain failed to
validate upon receipt. validate upon receipt.
4.2.1. More specifically a participating ARC intermediary must do the 4.2.1. More specifically a participating ARC intermediary must do the
following: following:
1. Validate that the ARC chain, if one is already present in the 1. Validate that the ARC chain, if one is already present in the
message, is intact and well-formed. ([ARC] Section 5.2) message, is intact and well-formed. ([ARC] Section 5.2,
"Validator Actions")
2. Record the ARC status in an Authentication-Results header 2. Record the ARC status in an Authentication-Results header
([RFC7601]) ([RFC7601])
3. Generate a new ARC set and add it to the message. ([ARC] 3. Generate a new ARC set and add it to the message. ([ARC]
Section 5.1) Section 5.1, "Sealer Actions")
4.3. Should every MTA be an ARC participant? 4.3. Should every MTA be an ARC participant?
Generally speaking, ARC is designed to operate at the ADMD level. Generally speaking, ARC is designed to operate at the ADMD level.
When a message is first received by an ADMD, the traditional When a message is first received by an ADMD, the traditional
authentication results should be captured and preserved - this could authentication results should be captured and preserved - this could
be the common case of creating an Authentication-Results header be the common case of creating an Authentication-Results header
field. But when it is determined that the message is being sent on field. But when it is determined that the message is being sent on
outside of that ADMD, that is when the ADMD should add itself to the outside of that ADMD, that is when the ADMD should add itself to the
ARC chain - before sending the message outside of the ADMD. ARC chain - before sending the message outside of the ADMD.
Some organizations may operate multiple ADMDs, with more or less Some organizations may operate multiple ADMDs, with more or less
independence between them. While they should make a determination independence between them. While they should make a determination
based on their specific circumstances, it may be useful and based on their specific circumstances, it may be useful and
appropriate to have one or both ADMDs be ARC participants. appropriate to have multiple ADMDs be ARC participants.
4.4. What should an intermediary do in the case of an invalid or 4.4. What should an intermediary do in the case of an invalid or
"broken" ARC chain? "broken" ARC chain?
In general terms, a participating ARC intermediary will note that an In general terms, a participating ARC intermediary will note that an
ARC chain was present and invalid, or broken, when it attaches its ARC chain was present and invalid, or broken, when it attaches its
own ARC seal and signature. However the fact that the ARC chain was own ARC seal and signature. However the fact that the ARC chain was
invalid should have no impact on whether and how the message is invalid should have no impact on whether and how the message is
delivered. delivered.
skipping to change at page 10, line 49 skipping to change at page 11, line 49
As mentioned previously reputation systems are very complex and As mentioned previously reputation systems are very complex and
usually specific to a given message receiver, and a meaningful usually specific to a given message receiver, and a meaningful
discussion of such a broad topic is beyond the scope of this discussion of such a broad topic is beyond the scope of this
document. document.
5. Guidance for Originators 5. Guidance for Originators
5.1. Where can I find out more information? 5.1. Where can I find out more information?
Please join the arc-discuss list at arc-discuss@dmarc.org. Please visit the http://arc-spec.org [2] web site, or join the arc-
discuss mailing list at http://lists.dmarc.org/mailman/listinfo/arc-
discuss [3].
To discuss the IETF spec itself, please join the dmarc working group To discuss the [ARC] specification itself, please join the DMARC
at [https://datatracker.ietf.org/wg/dmarc]. working group at https://datatracker.ietf.org/wg/dmarc [4].
5.2. How/where can I test interoperabililty for my implementation? 5.2. How/where can I test interoperabililty for my implementation?
The arc-discuss list is the best place to stay in touch with work in There have been numerous interoperability tests during the
progress. development of the [ARC] specification. These tests are usually
announced on both the arc-discuss mailing list at
http://lists.dmarc.org/mailman/listinfo/arc-discuss [5], and the
DMARC working group at https://datatracker/ietf.org/wg/dmarc [6].
Join whichever body is most appropriate for you and/or your
organization to receive future announcements.
5.3. How can ARC impact my email? 5.3. How can ARC impact my email?
Prior to ARC, certain DMARC policies on a domain would cause messages Prior to ARC, certain DMARC policies on a domain would cause messages
using those domains in the RFC5322.From field, and which pass through using those domains in the RFC5322.From field, and which pass through
certain kinds of intermediaries (mailing lists, forwarding services), certain kinds of intermediaries (mailing lists, forwarding services),
to fail authentication checks at the message receiver. As a result to fail authentication checks at the message receiver. As a result
these messages might not be delivered to the intended recipient. these messages might not be delivered to the intended recipient.
ARC seeks to provide these so-called "indirect mailflows" with a ARC seeks to provide these so-called "indirect mailflows" with a
skipping to change at page 12, line 43 skipping to change at page 14, line 7
Mailing Lists", BCP 167, RFC 6377, DOI 10.17487/RFC6377, Mailing Lists", BCP 167, RFC 6377, DOI 10.17487/RFC6377,
September 2011, <https://www.rfc-editor.org/info/rfc6377>. September 2011, <https://www.rfc-editor.org/info/rfc6377>.
[RFC7601] Kucherawy, M., "Message Header Field for Indicating [RFC7601] Kucherawy, M., "Message Header Field for Indicating
Message Authentication Status", RFC 7601, Message Authentication Status", RFC 7601,
DOI 10.17487/RFC7601, August 2015, DOI 10.17487/RFC7601, August 2015,
<https://www.rfc-editor.org/info/rfc7601>. <https://www.rfc-editor.org/info/rfc7601>.
7.2. Informative References 7.2. Informative References
[ARC] Andersen, K., Long, B., Blank, S., Kucherawy, M., and T. [ARC] Andersen, K., Long, B., Blank, S., and M. Kucherawy,
Draegen, "Authenticated Received Chain (ARC) Protocol", "Authenticated Received Chain (ARC) Protocol", December
October 2018, <https://tools.ietf.org/html/ 2018, <https://tools.ietf.org/html/
draft-ietf-dmarc-arc-protocol-18>. draft-ietf-dmarc-arc-protocol-23>.
[ARC-MULTI]
Andersen, K., Blank, S., and J. Levine, "Using Multiple
Signing Algorithms with ARC", June 2018,
<https://tools.ietf.org/html/
draft-ietf-dmarc-arc-multi-02>.
[draft-levine-eaiauth]
Levine, J., "E-mail Authentication for Internationalized
Mail", August 2018, <https://tools.ietf.org/html/
draft-levine-appsarea-eaiauth-03>.
[ENHANCED-STATUS] [ENHANCED-STATUS]
"IANA SMTP Enhanced Status Codes", n.d., "IANA SMTP Enhanced Status Codes", n.d.,
<http://www.iana.org/assignments/smtp-enhanced-status- <http://www.iana.org/assignments/smtp-enhanced-status-
codes/smtp-enhanced-status-codes.xhtml>. codes/smtp-enhanced-status-codes.xhtml>.
[I-D-7601bis]
Kucherawy, M., "Message Header Field for Indicating
Message Authentication Status", February 2018,
<https://datatracker.ietf.org/doc/
draft-ietf-dmarc-rfc7601bis/>.
[OAR] Chew, M. and M. Kucherawy, "Original-Authentication- [OAR] Chew, M. and M. Kucherawy, "Original-Authentication-
Results Header Field", February 2012, Results Header Field", February 2012,
<https://tools.ietf.org/html/ <https://tools.ietf.org/html/
draft-kucherawy-original-authres-00>. draft-kucherawy-original-authres-00>.
[RFC6376] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed., [RFC6376] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
"DomainKeys Identified Mail (DKIM) Signatures", STD 76, "DomainKeys Identified Mail (DKIM) Signatures", STD 76,
RFC 6376, DOI 10.17487/RFC6376, September 2011, RFC 6376, DOI 10.17487/RFC6376, September 2011,
<https://www.rfc-editor.org/info/rfc6376>. <https://www.rfc-editor.org/info/rfc6376>.
skipping to change at page 13, line 32 skipping to change at page 15, line 12
(DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015, (DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015,
<https://www.rfc-editor.org/info/rfc7489>. <https://www.rfc-editor.org/info/rfc7489>.
[RFC7960] Martin, F., Ed., Lear, E., Ed., Draegen. Ed., T., Zwicky, [RFC7960] Martin, F., Ed., Lear, E., Ed., Draegen. Ed., T., Zwicky,
E., Ed., and K. Andersen, Ed., "Interoperability Issues E., Ed., and K. Andersen, Ed., "Interoperability Issues
between Domain-based Message Authentication, Reporting, between Domain-based Message Authentication, Reporting,
and Conformance (DMARC) and Indirect Email Flows", and Conformance (DMARC) and Indirect Email Flows",
RFC 7960, DOI 10.17487/RFC7960, September 2016, RFC 7960, DOI 10.17487/RFC7960, September 2016,
<https://www.rfc-editor.org/info/rfc7960>. <https://www.rfc-editor.org/info/rfc7960>.
Appendix A. GLOSSARY 7.3. URIs
[1] https://datatracker.ietf.org/wg/dcrup/about
[2] http://arc-spec.org
[3] http://lists.dmarc.org/mailman/listinfo/arc-discuss
[4] https://datatracker.ietf.org/wg/dmarc
[5] http://lists.dmarc.org/mailman/listinfo/arc-discuss
[6] https://datatracker/ietf.org/wg/dmarc
[7] mailto:arc-discuss@dmarc.org
[8] https://datatracker.ietf.org/wg/dmarc
[9] https://arc-spec.org
[10] mailto:arc-discuss@dmarc.org
[11] http://lists.dmarc.org/mailman/listinfo/arc-discuss
Appendix A. Glossary
ADMD Administrative Management Domain as used in [RFC5598] and ADMD Administrative Management Domain as used in [RFC5598] and
similar references refers to a single entity operating one or more similar references refers to a single entity operating one or more
computers within one or more domain names under said entity's computers within one or more domain names under said entity's
control. One example might be a small company with a single control. One example might be a small company with a single
server, handling email for that company's domain. Another example server, handling email for that company's domain. Another example
might be a large university, operating many servers that fulfill might be a large university, operating many servers that fulfill
different roles, all handling email for several different domains different roles, all handling email for several different domains
representing parts of the university. representing parts of the university.
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Appendix C. Acknowledgements Appendix C. Acknowledgements
This draft is based on the work of OAR-Dev Group. This draft is based on the work of OAR-Dev Group.
The authors thank the entire OAR-Dev group for the ongoing help, The authors thank the entire OAR-Dev group for the ongoing help,
innumerable diagrams and discussions from all the participants, innumerable diagrams and discussions from all the participants,
especially: Alex Brotman, Brandon Long, Dave Crocker, Elizabeth especially: Alex Brotman, Brandon Long, Dave Crocker, Elizabeth
Zwicky, Franck Martin, Greg Colburn, J. Trent Adams, John Rae-Grant, Zwicky, Franck Martin, Greg Colburn, J. Trent Adams, John Rae-Grant,
Mike Hammer, Mike Jones, Steve Jones, Terry Zink, Tim Draegen. Mike Hammer, Mike Jones, Steve Jones, Terry Zink, Tim Draegen.
This document was influenced by questions posed in the arc-
discuss@dmarc.org [7] mailing list, and the authors thank all the
list participants for their input.
Appendix D. Comments and Feedback Appendix D. Comments and Feedback
Please address all comments, discussions, and questions to the dmarc Please address all comments, discussions, and questions about this
working group at [https://datatracker.ietf.org/wg/dmarc]. document, or about [ARC] itself, to the dmarc working group at
https://datatracker.ietf.org/wg/dmarc [8].
Authors' Addresses Readers looking for general information about ARC may refer to the
website https://arc-spec.org [9], or to the arc-discuss@dmarc.org
[10] mailing list at http://lists.dmarc.org/mailman/listinfo/arc-
discuss [11].
Steven Jones (editor) Authors' Addresses
Steven M Jones (editor)
DMARC.org DMARC.org
2419 McGee Avenue
Berkeley, California 94703
USA
Email: smj@crash.com Email: smj@crash.com
Kurt Andersen Kurt Andersen
LinkedIn LinkedIn
2029 Stierlin Ct. 2029 Stierlin Ct.
Mountain View, California 94043 Mountain View, California 94043
USA USA
Email: kurta@linkedin.com Email: kurta@linkedin.com
John Rae-Grant
Google
Email: johnrg@google.com
J. Trent Adams
Paypal
Email: trent.adams@paypal.com
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