Email Authentication Status Codes
draft-ietf-appsawg-email-auth-codes-03
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (appsawg WG) | |
|---|---|---|---|
| Author | Murray Kucherawy | ||
| Last updated | 2014-06-26 | ||
| Replaces | draft-kucherawy-email-auth-codes | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text xml htmlized pdfized bibtex | ||
| Reviews |
SECDIR Last Call review
(of
-04)
Has Issues
|
||
| Stream | WG state | In WG Last Call | |
| Document shepherd | S Moonesamy | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-appsawg-email-auth-codes-03
Network Working Group M. Kucherawy
Internet-Draft June 26, 2014
Updates: 7208 (if approved)
Intended status: Standards Track
Expires: December 28, 2014
Email Authentication Status Codes
draft-ietf-appsawg-email-auth-codes-03
Abstract
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
because of email authentication failures. This document registers
codes for this purpose.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 28, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Kucherawy Expires December 28, 2014 [Page 1]
Internet-Draft Email Auth Status Codes June 2014
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. New Status Codes . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. DKIM Failure Codes . . . . . . . . . . . . . . . . . . . . 3
3.2. SPF Failure Codes . . . . . . . . . . . . . . . . . . . . . 4
3.3. Reverse DNS Failure Code . . . . . . . . . . . . . . . . . 4
3.4. Multiple Authentication Failures Code . . . . . . . . . . . 5
4. General Considerations . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7
Kucherawy Expires December 28, 2014 [Page 2]
Internet-Draft Email Auth Status Codes June 2014
1. Introduction
[RFC3463] introduced Enhanced Mail System Status Codes, and [RFC5248]
created an IANA registry for these.
[RFC6376] and [RFC7208] introduced, respectively, DomainKeys
Identified Mail and Sender Policy Framework, two protocols for
conducting email authentication. Another common email acceptance
test is the reverse Domain Name System check 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
for indicating that a message is being rejected or deferred due to
local policy reasons related to any of these mechanisms. This is
potentially useful information to agents that need more than
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. 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:
3.1. DKIM Failure Codes
Code: X.7.20
Sample Text: No valid DKIM signature found
Associated basic status code: 5
Description: This status code is returned when a message
did not contain a valid DKIM signature,
contrary to local policy requirements.
(Note that this violates the advice of
Section 6.1 of RFC6376.)
Reference: [this document]; RFC6376
Submitter: M. Kucherawy
Change controller: IESG
Kucherawy Expires December 28, 2014 [Page 3]
Internet-Draft Email Auth Status Codes June 2014
Code: X.7.21
Sample Text: No valid author-aligned DKIM signature found
Associated basic status code: 5
Description: This status code is returned when a message
did not contain a valid DKIM signature
matching the domain(s) found in the From
header field, contrary to local policy
requirements. (Note that this violates the
advice of Section 6.1 of RFC6376.)
Reference: [this document]; RFC6376
Submitter: M. Kucherawy
Change controller: IESG
3.2. SPF Failure Codes
Code: X.7.22
Sample Text: SPF validation failed
Associated basic status code: 5
Description: This status code is returned when a message
completed an SPF check that produced a
"fail" result, contrary to local policy
requirements. Used in place of 5.7.1 as
described in Section 8.4 of RFC7208.
Reference: [this document]; RFC7208
Submitter: M. Kucherawy
Change controller: IESG
Code: X.7.23
Sample Text: SPF validation error
Associated basic status code: 4/5
Description: This status code is returned when evaluation
of SPF relative to an arriving message
resulted in an error. Used in place of
4.4.3 or 5.5.2 as described in Sections
8.6 and 8.6 of RFC7208.
Reference: [this document]; RFC7208
Submitter: M. Kucherawy
Change controller: IESG
3.3. Reverse DNS Failure Code
Kucherawy Expires December 28, 2014 [Page 4]
Internet-Draft Email Auth Status Codes June 2014
Code: X.7.24
Sample Text: Reverse DNS validation failed
Associated basic status code: 5
Description: This status code is returned when an SMTP
client's IP address failed a reverse DNS
validation check, contrary to local policy
requirements.
Reference: [this document]; Section 3 of RFC7001
Submitter: M. Kucherawy
Change controller: IESG
3.4. Multiple Authentication Failures Code
Code: X.7.25
Sample Text: Multiple authentication checks failed
Associated basic status code: 5
Description: This status code is returned when a message
failed more than one message authentication
check, contrary to local policy requirements.
The specific mechanisms that failed are not
specified.
Reference: [this document]
Submitter: M. Kucherawy
Change controller: IESG
4. General Considerations
By the nature of the Simple Mail Transfer Protocol (SMTP), only one
enhanced status code can be returned for a given exchange between
client and server. However, an operator might decide to defer or
reject a message for a plurality of reasons. Clients receiving 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
reason, for non-acceptance of the message or command.
It is important to note that Section 6.1 of [RFC6376] discourages
special treatment of messages bearing no valid signature. There 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 matching
the domain(s) in the From header field) in order to accept the
message. Moreover, some nascent technologies built atop SPF and DKIM
depend on such authentications. This work does not endorse
configurations that violate DKIM's recommendations, but rather
acknowledges that they do exist and merely seeks to provide for
improved interoperability with such operators.
A specific use case is mailing list software, which processes
Kucherawy Expires December 28, 2014 [Page 5]
Internet-Draft Email Auth Status Codes June 2014
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 versus indications that the
recipient address is no longer valid.
When multiple authentication methods fail, the SMTP server SHOULD use
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
expected to fail, and thus returning that method's specific code is
not information useful to the sending agent.
The reverse IP DNS check is defined in Section 2.6.3 of [RFC7001].
5. Security Considerations
Use of these codes reveals local policy with respect to email
authentication, which can be useful information to actors attempting
to deliver undesirable mail. It should be noted that there is no
specific obligation to use these codes; if an operator wishes not to
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.
6. IANA Considerations
Registration of new enhanced status codes, for addition to the SMTP
Enhanced Status Codes Registry, can be found in Section 3.
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",
RFC 3463, January 2003.
[RFC5248] Hansen, T. and J. Klensin, "A Registry for SMTP Enhanced
Mail System Status Codes", BCP 138, RFC 5248, June 2008.
[RFC6376] Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys
Identified Mail (DKIM) Signatures", STD 76, RFC 6376,
September 2011.
[RFC7001] Kucherawy, M., "Message Header Field for Indicating
Message Authentication Status", RFC 7001, September 2013.
[RFC7208] Kitterman, S., "Sender Policy Framework (SPF) for
Authorizing Use of Domains in Email, Version 1", RFC 7208,
April 2014.
Kucherawy Expires December 28, 2014 [Page 6]
Internet-Draft Email Auth Status Codes June 2014
Appendix A. Acknowledgments
Claudio Allocchio, Dave Crocker, Ned Freed, Arnt Gulbrandsen, Scott
Kitterman, Barry Leiba, Alexey Melnikov, and Hector Santos
contributed to this work.
Author's Address
Murray S. Kucherawy
270 Upland Drive
San Francisco, CA 94127
USA
EMail: superuser@gmail.com
Kucherawy Expires December 28, 2014 [Page 7]