draft-ietf-appsawg-email-auth-codes-01.txt   draft-ietf-appsawg-email-auth-codes-02.txt 
Network Working Group M. Kucherawy Network Working Group M. Kucherawy
Internet-Draft May 27, 2014 Internet-Draft June 2, 2014
Intended status: Informational Intended status: Informational
Expires: November 28, 2014 Expires: December 4, 2014
Email Authentication Status Codes Email Authentication Status Codes
draft-ietf-appsawg-email-auth-codes-01 draft-ietf-appsawg-email-auth-codes-02
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 33 skipping to change at page 1, line 33
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
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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 November 28, 2014. This Internet-Draft will expire on December 4, 2014.
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. New Status Codes . . . . . . . . . . . . . . . . . . . . . . . 3 2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. DKIM Failures Code . . . . . . . . . . . . . . . . . . . . 3 3. New Status Codes . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. SPF Failure Code . . . . . . . . . . . . . . . . . . . . . 4 3.1. DKIM Failure Codes . . . . . . . . . . . . . . . . . . . . 3
2.3. Reverse DNS Failure Code . . . . . . . . . . . . . . . . . 4 3.2. SPF Failure Codes . . . . . . . . . . . . . . . . . . . . . 4
2.4. Multiple Authentication Failures Code . . . . . . . . . . . 4 3.3. Reverse DNS Failure Code . . . . . . . . . . . . . . . . . 4
3. General Considerations . . . . . . . . . . . . . . . . . . . . 5 3.4. Multiple Authentication Failures Code . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 4. General Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 6 7. Normative References . . . . . . . . . . . . . . . . . . . . . 6
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 and Sender Policy Framework, two protocols for
conducting email authentication. Another common email acceptance conducting email authentication. Another common email acceptance
test is the reverse Domain Name System check on an email client's IP test is the reverse Domain Name System check on an email client's IP
address, as described in Section 3 of [RFC7001]. 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 either of these two mechanisms. This local policy reasons related to either of these two mechanisms. This
document introduces enhanced status codes for reporting those cases is potentially useful information to agents that need more than
to clients. rudimentary handling information about the reason a message was
rejected on receipt. This document introduces enhanced status codes
for reporting those cases to clients.
2. New Status Codes 2. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
3. New Status Codes
The following new status codes are defined: The following new status codes are defined:
2.1. DKIM Failures Code 3.1. DKIM Failure Codes
Code: X.7.19 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: 5
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.7.20
Sample Text: No valid author DKIM signature found Sample Text: No valid author DKIM signature found
Associated basic status code: 5 Associated basic status code: 5
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 matching the domain(s) found in the From
header field, contrary to local policy header field, contrary to local policy
requirements. (Note that this violates the requirements. (Note that this violates the
advice of Section 6.1 of RFC6376.) 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
2.2. SPF Failure Code 3.2. SPF Failure Codes
Code: X.7.21 Code: X.7.22
Sample Text: SPF validation failed Sample Text: SPF validation failed
Associated basic status code: 5 Associated basic status code: 5
Description: This status code is returned when a message Description: This status code is returned when a message
failed an SPF check, contrary to local failed an SPF check, contrary to local
policy requirements. policy requirements.
Reference: [this document]; RFC7208 Reference: [this document]; RFC7208
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
2.3. Reverse DNS Failure Code Code: X.7.23
Sample Text: SPF validation error
Associated basic status code: 5
Description: This status code is returned when evaluation
of SPF relative to an arriving message
resulted in an error.
Reference: [this document]; RFC7208
Submitter: M. Kucherawy
Change controller: IESG
Code: X.7.22 3.3. Reverse DNS Failure Code
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: 5
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 2.6.3 of RFC7001 Reference: [this document]; Section 3 of RFC 7001
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
2.4. Multiple Authentication Failures Code 3.4. Multiple Authentication Failures Code
Code: X.7.23 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: 5
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
3. 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 signature. There are
some operators that disregard this advice, a few of which go so far some operators that disregard this advice, a few of which go so far
as to require a valid Author Domain signature in order to accept the as to require a valid Author Domain signature in order to accept the
message. Moreover, some nascent technologies built atop SPF and DKIM message. Moreover, some nascent technologies built atop SPF and DKIM
depend on such authentications. This work does not endorse 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 provides for improved acknowledges that they do exist and provides for improved
interoperability with such operators. interoperability with such operators.
A specific use case is mailing list software, which processes
rejections in order to remove from the subscriber set those addresses
that are no longer valid. There is a need in that case to
distinguish authentication failures verus indications that the
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].
4. Security Considerations 5. Security Considerations
Use of these codes reveals local policy with respect to email Use of these codes reveals local policy with respect to email
authentication, which can be useful information to actors attempting authentication, which can be useful information to actors attempting
to deliver undesirable mail. It should be noted that there is no to deliver undesirable mail. It should be noted that there is no
specific obligation to use these codes; if an operator wishes not to specific obligation to use these codes; if an operator wishes not to
reveal this aspect of local policy, it can continue using a generic reveal this aspect of local policy, it can continue using a generic
result code such as 5.7.7 or even 5.7.0. result code such as 5.7.7, 5.7.1, or even 5.7.0.
5. IANA Considerations 6. IANA Considerations
Registration of two new enhanced status codes, for addition to the Registration of new enhanced status codes, for addition to the SMTP
SMTP Enhanced Status Codes Registry, can be found in Section 2. Enhanced Status Codes Registry, can be found in Section 3.
6. Normative References 7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes", [RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes",
RFC 3463, January 2003. RFC 3463, January 2003.
[RFC5248] Hansen, T. and J. Klensin, "A Registry for SMTP Enhanced [RFC5248] Hansen, T. and J. Klensin, "A Registry for SMTP Enhanced
Mail System Status Codes", BCP 138, RFC 5248, June 2008. Mail System Status Codes", BCP 138, RFC 5248, June 2008.
[RFC6376] Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys [RFC6376] Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys
Identified Mail (DKIM) Signatures", STD 76, RFC 6376, Identified Mail (DKIM) Signatures", STD 76, RFC 6376,
September 2011. September 2011.
[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
Ned Freed, Arnt Gulbrandsen, and Barry Leiba contributed to this Claudio Allocchio, Ned Freed, Arnt Gulbrandsen, Scott Kitterman,
Barry Leiba, Alexey Melnikov, and Hector Santos contributed to this
work. 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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