draft-ietf-appsawg-email-auth-codes-07.txt   rfc7372.txt 
Network Working Group M. Kucherawy Internet Engineering Task Force (IETF) M. Kucherawy
Internet-Draft August 8, 2014 Request for Comments: 7372 September 2014
Updates: 7208 (if approved) Updates: 7208
Intended status: Standards Track Category: Standards Track
Expires: February 9, 2015 ISSN: 2070-1721
Email Authentication Status Codes Email Authentication Status Codes
draft-ietf-appsawg-email-auth-codes-07
Abstract Abstract
This document registers code points to allow status codes to be This document registers code points to allow status codes to be
returned to an email client to indicate that a message is being returned to an email client to indicate that a message is being
rejected or deferred specifically because of email authentication rejected or deferred specifically because of email authentication
failures. failures.
This document updates [RFC7208] since some of the code points This document updates RFC 7208, since some of the code points
registered replace the ones recommended for use in that document. registered replace the ones recommended for use in that document.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
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Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on February 9, 2015. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7372.
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.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. New Enhanced 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 . . . . . . . . . . . . . . . . . 5 3.3. Reverse DNS Failure Code . . . . . . . . . . . . . . . . 5
3.4. Multiple Authentication Failures Code . . . . . . . . . . . 5 3.4. Multiple Authentication Failures Code . . . . . . . . . . 5
4. General Considerations . . . . . . . . . . . . . . . . . . . . 6 4. General Considerations . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . . 7 7. Normative References . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 8
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 (DKIM) and Sender Policy Framework (SPF), two Identified Mail (DKIM) and Sender Policy Framework (SPF), two
protocols for conducting message authentication. Another common protocols for conducting message authentication. Another common
email acceptance test is the reverse Domain Name System (DNS) check email acceptance test is the reverse Domain Name System (DNS) check
skipping to change at page 3, line 37 skipping to change at page 3, line 7
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 Enhanced Status Codes 3. New Enhanced Status Codes
The following new enhanced status codes are defined: The new enhanced status codes are defined in the following
subsections.
3.1. DKIM Failure Codes 3.1. DKIM Failure Codes
In the code point definitions below, the following definitions are In the code point definitions below, the following definitions are
used: used:
passing: A signature is "passing" if the basic DKIM verification passing: A signature is "passing" if the basic DKIM verification
algorithm as defined in [RFC6376] succeeds. algorithm, as defined in [RFC6376], succeeds.
acceptable: A signature is "acceptable" if it satisfies all locally acceptable: A signature is "acceptable" if it satisfies all locally
defined requirements (if any) in addition to passing the basic defined requirements (if any) in addition to passing the basic
DKIM verification algorithm (e.g., certain header fields are DKIM verification algorithm (e.g., certain header fields are
included in the signed content; no partial signatures; etc.). included in the signed content, no partial signatures, etc.).
Code: X.7.20 Code: X.7.20
Sample Text: No passing DKIM signature found Sample Text: No passing DKIM signature found
Associated basic status code: 550 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 any passing DKIM did not contain any passing DKIM
signatures. (This violates the signatures. (This violates the
advice of Section 6.1 of RFC6376.) advice of Section 6.1 of RFC 6376.)
Reference: [this document]; RFC6376 Reference: [RFC7372]; [RFC6376]
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
Code: X.7.21 Code: X.7.21
Sample Text: No acceptable DKIM signature found Sample Text: No acceptable DKIM signature found
Associated basic status code: 550 Associated basic status code: 550
Description: This status code is returned when a message Description: This status code is returned when a message
contains one or more passing DKIM signatures, contains one or more passing DKIM signatures,
but none are acceptable. (This violates the but none are acceptable. (This violates the
advice of Section 6.1 of RFC6376.) advice of Section 6.1 of RFC 6376.)
Reference: [this document]; RFC6376 Reference: [RFC7372]; [RFC6376]
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
Code: X.7.22 Code: X.7.22
Sample Text: No valid author-matched DKIM signature found Sample Text: No valid author-matched DKIM signature found
Associated basic status code: 550 Associated basic status code: 550
Description: This status code is returned when a message Description: This status code is returned when a message
contains one or more passing DKIM contains one or more passing DKIM
signatures, but none are acceptable because signatures, but none are acceptable because
none have an identifier(s) none have an identifier(s)
that matches the author address(es) found in that matches the author address(es) found in
the From header field. This is a special the From header field. This is a special
case of X.7.21. (This violates the advice case of X.7.21. (This violates the advice
of Section 6.1 of RFC6376.) of Section 6.1 of RFC 6376.)
Reference: [this document]; RFC6376 Reference: [RFC7372]; [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.7.23 Code: X.7.23
Sample Text: SPF validation failed Sample Text: SPF validation failed
Associated basic status code: 550 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 RFC 7208.
Reference: [this document]; RFC7208 Reference: [RFC7372]; [RFC7208]
Submitter: M. Kucherawy Submitter: M. Kucherawy
Change controller: IESG Change controller: IESG
Code: X.7.24 Code: X.7.24
Sample Text: SPF validation error Sample Text: SPF validation error
Associated basic status code: 451/550 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 8.7 of RFC7208. 8.6 and 8.7 of RFC 7208.
Reference: [this document]; RFC7208 Reference: [RFC7372]; [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.7.25 Code: X.7.25
Sample Text: Reverse DNS validation failed Sample Text: Reverse DNS validation failed
Associated basic status code: 550 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: [RFC7372]; 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.7.26 Code: X.7.26
Sample Text: Multiple authentication checks failed Sample Text: Multiple authentication checks failed
Associated basic status code: 550 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 particular mechanisms that failed are not
specified. specified.
Reference: [this document] Reference: [RFC7372]
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 DKIM signature. There special treatment of messages bearing no valid DKIM signature. There
are some operators that disregard this advice, a few of which go so are some operators that disregard this advice, a few of which go so
far as to require a valid Author Domain signature (that is, one far as to require a valid Author Domain Signature (that is, one
matching the domain(s) in the From header field) in order to accept matching the domain(s) in the From header field) in order to accept
the message. Moreover, some nascent technologies built atop SPF and the message. Moreover, some nascent technologies built atop SPF and
DKIM 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 for these codes is mailing list software, which A specific use case for these codes is mailing list software, which
processes rejections in order to remove from the subscriber set those 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 addresses that are no longer valid. There is a need in that case to
distinguish authentication failures versus indications that the distinguish authentication failures from indications that the
recipient address is no longer valid. recipient address is no longer valid.
If a receiving server performs multiple authentication checks, and If a receiving server performs multiple authentication checks and
more than one of them fails thus warranting rejection of the message, more than one of them fails, thus warranting rejection of the
the SMTP server SHOULD use the code that indicates multiple methods message, the SMTP server SHOULD use the code that indicates multiple
failed rather than only reporting the first one that failed. It may methods failed rather than only reporting the first one that failed.
be the case that one method is always expected to fail, and thus It may be the case that one method is always expected to fail; thus,
returning that method's specific code is not information useful to returning that method's specific code is not information useful to
the sending agent. 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 3 of [RFC7001].
Any message authentication or policy enforcement technologies Any message authentication or policy enforcement technologies
developed in the future should also include registration of their own developed in the future should also include registration of their own
enhanced status codes so that this kind of specific reporting is enhanced status codes so that this kind of specific reporting is
available to operators that wish to use them. available to operators that wish to use them.
5. 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 undesired mail. It should be noted that there is no to deliver undesired 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, 5.7.1, or even 5.7.0. result code such as 5.7.7, 5.7.1, or even 5.7.0.
6. IANA Considerations 6. IANA Considerations
Registration of new enhanced status codes, for addition to the Registration of new enhanced status codes, for addition to the
Enumerated Stauts Codes sub-registry of the SMTP Enhanced Status Enumerated Status Codes sub-registry of the SMTP Enhanced Status
Codes Registry, can be found in Section 3. Codes Registry, can be found in Section 3.
7. Normative References 7. 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, March 1997. 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
RFC 3463, January 2003. 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.
 End of changes. 28 change blocks. 
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