draft-ietf-appsawg-email-auth-codes-03.txt   draft-ietf-appsawg-email-auth-codes-04.txt 
Network Working Group M. Kucherawy Network Working Group M. Kucherawy
Internet-Draft June 26, 2014 Internet-Draft July 8, 2014
Updates: 7208 (if approved) Updates: 7208 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: December 28, 2014 Expires: January 9, 2015
Email Authentication Status Codes Email Authentication Status Codes
draft-ietf-appsawg-email-auth-codes-03 draft-ietf-appsawg-email-auth-codes-04
Abstract Abstract
There is at present no way to return a status code to an email client There is at present no way to return a status code to an email client
that indicates a message is being rejected or deferred specifically that indicates a message is being rejected or deferred specifically
because of email authentication failures. This document registers because of email authentication failures. This document registers
codes for this purpose. codes for this purpose.
Status of This Memo Status of This Memo
skipping to change at page 1, line 34 skipping to change at page 1, line 34
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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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 December 28, 2014. This Internet-Draft will expire on January 9, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. New Status Codes . . . . . . . . . . . . . . . . . . . . . . . 3 3. New Enhanced Status Codes . . . . . . . . . . . . . . . . . . . 3
3.1. DKIM Failure Codes . . . . . . . . . . . . . . . . . . . . 3 3.1. DKIM Failure Codes . . . . . . . . . . . . . . . . . . . . 3
3.2. SPF Failure Codes . . . . . . . . . . . . . . . . . . . . . 4 3.2. SPF Failure Codes . . . . . . . . . . . . . . . . . . . . . 4
3.3. Reverse DNS Failure Code . . . . . . . . . . . . . . . . . 4 3.3. Reverse DNS Failure Code . . . . . . . . . . . . . . . . . 4
3.4. Multiple Authentication Failures Code . . . . . . . . . . . 5 3.4. Multiple Authentication Failures Code . . . . . . . . . . . 5
4. General Considerations . . . . . . . . . . . . . . . . . . . . 5 4. General Considerations . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . . 6 7. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
[RFC3463] introduced Enhanced Mail System Status Codes, and [RFC5248] [RFC3463] introduced Enhanced Mail System Status Codes, and [RFC5248]
created an IANA registry for these. created an IANA registry for these.
[RFC6376] and [RFC7208] introduced, respectively, DomainKeys [RFC6376] and [RFC7208] introduced, respectively, DomainKeys
Identified Mail and Sender Policy Framework, two protocols for Identified Mail (DKIM) and Sender Policy Framework (SPF), two
conducting email authentication. Another common email acceptance protocols for conducting message authentication. Another common
test is the reverse Domain Name System check on an email client's IP email acceptance test is the reverse Domain Name System (DNS) check
address, as described in Section 3 of [RFC7001]. on an email client's IP address, as described in Section 3 of
[RFC7001].
The current set of enhanced status codes does not include any code The current set of enhanced status codes does not include any code
for indicating that a message is being rejected or deferred due to for indicating that a message is being rejected or deferred due to
local policy reasons related to any of these mechanisms. This is local policy reasons related to any of these mechanisms. This is
potentially useful information to agents that need more than potentially useful information to agents that need more than
rudimentary handling information about the reason a message was rudimentary handling information about the reason a message was
rejected on receipt. This document introduces enhanced status codes rejected on receipt. This document introduces enhanced status codes
for reporting those cases to clients. for reporting those cases to clients.
This document updates [RFC7208] as new enhanced status codes relevant
to that specification are being registered.
2. Key Words 2. Key Words
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
[RFC2119]. [RFC2119].
3. New Status Codes 3. New Enhanced Status Codes
The following new status codes are defined: The following new enhanced status codes are defined:
3.1. DKIM Failure Codes 3.1. DKIM Failure Codes
Code: X.7.20 Code: X.7.20
Sample Text: No valid DKIM signature found Sample Text: No valid DKIM signature found
Associated basic status code: 5 Associated basic status code: 550
Description: This status code is returned when a message Description: This status code is returned when a message
did not contain a valid DKIM signature, did not contain a valid DKIM signature,
contrary to local policy requirements. contrary to local policy requirements.
(Note that this violates the advice of (Note that this violates the advice of
Section 6.1 of RFC6376.) Section 6.1 of RFC6376.)
Reference: [this document]; RFC6376 Reference: [this document]; RFC6376
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
Code: X.7.21 Code: X.7.21
Sample Text: No valid author-aligned DKIM signature found Sample Text: No valid author-aligned DKIM signature found
Associated basic status code: 5 Associated basic status code: 550
Description: This status code is returned when a message Description: This status code is returned when a message
did not contain a valid DKIM signature did not contain a valid DKIM signature
matching the domain(s) found in the From whose identifier(s) match the address(es)
header field, contrary to local policy found in the From header field, contrary to
requirements. (Note that this violates the local policy requirements. (Note that this
advice of Section 6.1 of RFC6376.) violates the advice of Section 6.1 of
RFC6376.)
Reference: [this document]; RFC6376 Reference: [this document]; RFC6376
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
3.2. SPF Failure Codes 3.2. SPF Failure Codes
Code: X.7.22 Code: X.7.22
Sample Text: SPF validation failed Sample Text: SPF validation failed
Associated basic status code: 5 Associated basic status code: 550
Description: This status code is returned when a message Description: This status code is returned when a message
completed an SPF check that produced a completed an SPF check that produced a
"fail" result, contrary to local policy "fail" result, contrary to local policy
requirements. Used in place of 5.7.1 as requirements. Used in place of 5.7.1 as
described in Section 8.4 of RFC7208. described in Section 8.4 of RFC7208.
Reference: [this document]; RFC7208 Reference: [this document]; RFC7208
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
Code: X.7.23 Code: X.7.23
Sample Text: SPF validation error Sample Text: SPF validation error
Associated basic status code: 4/5 Associated basic status code: 451/550
Description: This status code is returned when evaluation Description: This status code is returned when evaluation
of SPF relative to an arriving message of SPF relative to an arriving message
resulted in an error. Used in place of resulted in an error. Used in place of
4.4.3 or 5.5.2 as described in Sections 4.4.3 or 5.5.2 as described in Sections
8.6 and 8.6 of RFC7208. 8.6 and 8.7 of RFC7208.
Reference: [this document]; RFC7208 Reference: [this document]; RFC7208
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
3.3. Reverse DNS Failure Code 3.3. Reverse DNS Failure Code
Code: X.7.24 Code: X.7.24
Sample Text: Reverse DNS validation failed Sample Text: Reverse DNS validation failed
Associated basic status code: 5 Associated basic status code: 550
Description: This status code is returned when an SMTP Description: This status code is returned when an SMTP
client's IP address failed a reverse DNS client's IP address failed a reverse DNS
validation check, contrary to local policy validation check, contrary to local policy
requirements. requirements.
Reference: [this document]; Section 3 of RFC7001 Reference: [this document]; Section 3 of RFC7001
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
3.4. Multiple Authentication Failures Code 3.4. Multiple Authentication Failures Code
Code: X.7.25 Code: X.7.25
Sample Text: Multiple authentication checks failed Sample Text: Multiple authentication checks failed
Associated basic status code: 5 Associated basic status code: 550
Description: This status code is returned when a message Description: This status code is returned when a message
failed more than one message authentication failed more than one message authentication
check, contrary to local policy requirements. check, contrary to local policy requirements.
The specific mechanisms that failed are not The specific mechanisms that failed are not
specified. specified.
Reference: [this document] Reference: [this document]
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
4. General Considerations 4. General Considerations
By the nature of the Simple Mail Transfer Protocol (SMTP), only one By the nature of the Simple Mail Transfer Protocol (SMTP), only one
enhanced status code can be returned for a given exchange between enhanced status code can be returned for a given exchange between
client and server. However, an operator might decide to defer or client and server. However, an operator might decide to defer or
reject a message for a plurality of reasons. Clients receiving these reject a message for a plurality of reasons. Clients receiving these
codes need to consider that the failure reflected by one of these codes need to consider that the failure reflected by one of these
status codes might not reflect the only reason, or the most important status codes might not reflect the only reason, or the most important
reason, for non-acceptance of the message or command. reason, for non-acceptance of the message or command.
It is important to note that Section 6.1 of [RFC6376] discourages It is important to note that Section 6.1 of [RFC6376] discourages
special treatment of messages bearing no valid signature. There are special treatment of messages bearing no valid DKIM signature. There
some operators that disregard this advice, a few of which go so far are some operators that disregard this advice, a few of which go so
as to require a valid Author Domain signature (that is, one matching far as to require a valid Author Domain signature (that is, one
the domain(s) in the From header field) in order to accept the matching the domain(s) in the From header field) in order to accept
message. Moreover, some nascent technologies built atop SPF and DKIM the message. Moreover, some nascent technologies built atop SPF and
depend on such authentications. This work does not endorse DKIM depend on such authentications. This work does not endorse
configurations that violate DKIM's recommendations, but rather configurations that violate DKIM's recommendations, but rather
acknowledges that they do exist and merely seeks to provide for acknowledges that they do exist and merely seeks to provide for
improved interoperability with such operators. improved interoperability with such operators.
A specific use case is mailing list software, which processes A specific use case for these codes is mailing list software, which
rejections in order to remove from the subscriber set those addresses processes rejections in order to remove from the subscriber set those
that are no longer valid. There is a need in that case to addresses that are no longer valid. There is a need in that case to
distinguish authentication failures versus indications that the distinguish authentication failures versus indications that the
recipient address is no longer valid. recipient address is no longer valid.
When multiple authentication methods fail, the SMTP server SHOULD use When multiple authentication methods fail, the SMTP server SHOULD use
the code that indicates multiple methods failed rather than only the the code that indicates multiple methods failed rather than only the
first one that failed. It may be the case that one method is always first one that failed. It may be the case that one method is always
expected to fail, and thus returning that method's specific code is expected to fail, and thus returning that method's specific code is
not information useful to the sending agent. not information useful to the sending agent.
The reverse IP DNS check is defined in Section 2.6.3 of [RFC7001]. The reverse IP DNS check is defined in Section 2.6.3 of [RFC7001].
skipping to change at page 7, line 8 skipping to change at page 7, line 8
[RFC7001] Kucherawy, M., "Message Header Field for Indicating [RFC7001] Kucherawy, M., "Message Header Field for Indicating
Message Authentication Status", RFC 7001, September 2013. Message Authentication Status", RFC 7001, September 2013.
[RFC7208] Kitterman, S., "Sender Policy Framework (SPF) for [RFC7208] Kitterman, S., "Sender Policy Framework (SPF) for
Authorizing Use of Domains in Email, Version 1", RFC 7208, Authorizing Use of Domains in Email, Version 1", RFC 7208,
April 2014. April 2014.
Appendix A. Acknowledgments Appendix A. Acknowledgments
Claudio Allocchio, Dave Crocker, Ned Freed, Arnt Gulbrandsen, Scott Claudio Allocchio, Dave Crocker, Ned Freed, Arnt Gulbrandsen, Scott
Kitterman, Barry Leiba, Alexey Melnikov, and Hector Santos Kitterman, Barry Leiba, Alexey Melnikov, S. Moonesamy, and Hector
contributed to this work. Santos contributed to this work.
Author's Address Author's Address
Murray S. Kucherawy Murray S. Kucherawy
270 Upland Drive 270 Upland Drive
San Francisco, CA 94127 San Francisco, CA 94127
USA USA
EMail: superuser@gmail.com EMail: superuser@gmail.com
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