Individual submission M. Kucherawy
Internet-Draft Sendmail, Inc.
Intended status: Standards Track January 28, 2009
Expires: August 1, 2009
Reporting of DKIM Verification Failures
draft-kucherawy-dkim-reporting-05
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 1, 2009.
Copyright Notice
Copyright (c) 2009 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.
Kucherawy Expires August 1, 2009 [Page 1]
Internet-Draft DKIM Reporting January 2009
Abstract
This memo presents an extension to the DomainKeys Identified Mail
(DKIM) specifications to allow public keys for verification to
include a reporting address to be used to report message verification
issues, and extends an Internet Message reporting format to be
followed when generating such reports.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Keywords . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Imported Definitions . . . . . . . . . . . . . . . . . . . 4
3. Optional Key Reporting Address for DKIM . . . . . . . . . . . 5
4. Optional Key Reporting Address for DKIM-ADSP . . . . . . . . . 7
5. Requested Reports . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Requested Reports for DKIM Failures . . . . . . . . . . . 9
5.2. Requested Reports for DKIM ADSP Failures . . . . . . . . . 9
6. Reporting Formats . . . . . . . . . . . . . . . . . . . . . . 10
7. Extension ARF Fields for DKIM Reporting . . . . . . . . . . . 11
7.1. New ARF Feedback Type . . . . . . . . . . . . . . . . . . 11
7.2. New ARF Header Names . . . . . . . . . . . . . . . . . . . 11
7.3. DKIM Failure Types . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8.1. DKIM Key Tag Registration . . . . . . . . . . . . . . . . 13
8.2. DKIM ADSP Tag Registration . . . . . . . . . . . . . . . . 13
8.3. Updates to ARF Feedback Types . . . . . . . . . . . . . . 13
8.4. Updates to ARF Header Names . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9.1. Forgeries . . . . . . . . . . . . . . . . . . . . . . . . 15
9.2. Automatic Generation . . . . . . . . . . . . . . . . . . . 15
9.3. Envelope Sender Selection . . . . . . . . . . . . . . . . 15
9.4. Reporting Multiple Incidents . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 18
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 19
B.1. Example Use of DKIM Key Extension Tags . . . . . . . . . . 19
B.2. Example Use of DKIM ADSP Extension Tags . . . . . . . . . 19
B.3. Example Use of ARF Extension Headers . . . . . . . . . . . 20
Appendix C. Public Discussion . . . . . . . . . . . . . . . . . . 21
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22
Kucherawy Expires August 1, 2009 [Page 2]
Internet-Draft DKIM Reporting January 2009
1. Introduction
[DKIM] introduced a standard for digital signing of messages for the
purposes of sender authentication. There exist cases in which a
domain name owner might want to receive reports from verifiers that
determine DKIM-signed mail apparently from its domain is failing to
verify according to [DKIM] or is "Suspicious" according to
[I-D.DRAFT-IETF-DKIM-SSP].
This document extends [DKIM] and [I-D.DRAFT-IETF-DKIM-SSP] to add an
optional reporting address to selector records, an optional means of
specifying a desired report format, and furthermore extends
[I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT] to add features required for
DKIM reporting.
This memo presumes those specifications thus modified will issue as
RFCs without these modifications. If the modifications are adopted
prior to their publicatons, clearly those sections of this memo can
be removed.
Kucherawy Expires August 1, 2009 [Page 3]
Internet-Draft DKIM Reporting January 2009
2. Definitions
2.1. Keywords
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KEYWORDS].
2.2. Imported Definitions
The ABNF token "qp-section" is imported from [MIME].
base64 is defined in [MIME].
Kucherawy Expires August 1, 2009 [Page 4]
Internet-Draft DKIM Reporting January 2009
3. Optional Key Reporting Address for DKIM
There exist cases in which a domain name owner employing [DKIM] for
e-mail signing and authentication may want to know when signatures in
use by specific keys are not successfully verifying. Currently there
is no such mechanism defined.
This document adds the following two optional "tags" (as defined in
[DKIM]) to the DKIM key records, using the form defined in that
specification:
r= Reporting Address (plain-text; OPTIONAL; no default). The value
MUST be a dkim-quoted-printable string containing the local-part
of an e-mail address to which a report SHOULD be sent when mail
signed with this key fails verification because either (a) the
signature verification itself failed, or (b) the body hash test
failed. The format of this reply is selected by the value of the
"rf=" tag, defined below. To generate a complete address to which
the report is sent, the verifier simply appends to this value an
"@" followed by the domain found in the "d=" tag of the signature
whose validation failed.
ABNF:
key-r-tag = %x72 *WSP "=" *WSP qp-section
rf= Reporting Format (plain-text; OPTIONAL; default is "arf"). The
value MUST be a colon-separated list of tokens representing
desired reporting formats in order of preference. Each element of
the list MUST be a token which is taken from the registered list
of DKIM report formats. See Section 8 for a description of the
registry and Section 6 for a description of recognized formats.
The verifier generating reports MUST generate a report using the
first token in the list which represents a report format it is
capable of generating.
ABNF:
rep-format = ( "arf" / "smtp" )
key-rf-tag = %x72 %x66 *WSP "=" *WSP rep-format *WSP 0*( ":" *WSP
rep-format )
ri= Requested Report Interval (plain-text; OPTIONAL; default is
"0"). The value is an integer which specifies an interval during
which no more than one report about a given type of incident
should be generated. A value of "0" requests a report for every
incident. Where the requested interval is not zero, the agent
Kucherawy Expires August 1, 2009 [Page 5]
Internet-Draft DKIM Reporting January 2009
generating a report SHOULD include an "Incidents:" header in the
generated report so the receiving agent has some indication of how
many reports were suppressed.
ABNF:
key-ri-tag = %x72 %x69 *WSP "=" *WSP 1*DIGIT
ro= Requested Reports (plain-text; OPTIONAL; default is "all"). The
value MUST be a colon-separated list of tokens representing those
conditions under which a report is desired. See Section 5.1 for a
list of valid tags.
ABNF:
key-ro-type = ( "all" / "s" / "v" / "x" )
key-ro-tag = %x72 %x6f *WSP "=" *WSP key-ro-type *WSP 0* ( ":"
*WSP key-ro-type )
rs= Requested SMTP Error String (plain-text; OPTIONAL; no default).
The value is a string the signing domain requests be included in
SMTP error strings when messages are rejected.
ABNF:
key-rs-tag = %x72 %x73 *WSP "=" qp-section
Kucherawy Expires August 1, 2009 [Page 6]
Internet-Draft DKIM Reporting January 2009
4. Optional Key Reporting Address for DKIM-ADSP
There also exist cases in which a domain name owner employing
[I-D.DRAFT-IETF-DKIM-SSP] for announcing signing practises with DKIM
may want to know when messages are received unsigned or signed with
third-party signatures contrary to the sender's published policy.
Currently there is no such mechanism defined.
This document adds the following two optional "tags" (as defined in
[I-D.DRAFT-IETF-DKIM-SSP]) to the DKIM ADSP records, using the form
defined in that specification:
r= Reporting Address (plain-text; OPTIONAL; no default). The value
MUST be a dkim-quoted-printable string containing the local-part
of an e-mail address to which a report SHOULD be sent when mail
claiming to be from this domain failed the verification algorithm
described in [I-D.DRAFT-IETF-DKIM-SSP], in particular because a
message arrived unsigned or signed by a third-party signature in
violation of the sender's published policy. The format of this
reply MUST be in the format specified by the "rf=" tag defined
below. To generate a complete address to which the report is
sent, the verifier simply appends to this value an "@" followed by
the domain whose policy was queried in order to evaluate the
sender's ADSP.
ABNF:
adsp-r-tag = %x72 *WSP "=" qp-section
ABNF:
key-r-tag = %x72 *WSP "=" qp-section
rf= Reporting Format (plain-text; OPTIONAL; default is "arf"). The
value MUST be a colon-separated list of tokens representing
desired reporting formats in decreasing order of preference. Each
element of the list MUST be a token which is taken from the
registered list of DKIM report formats. See Section 8 for a
description of the registry and Section 6 for a description of
recognized formats. The verifier generating reports MUST generate
a report using the first token in the list which represents a
report format it is capable of generating.
ABNF:
Kucherawy Expires August 1, 2009 [Page 7]
Internet-Draft DKIM Reporting January 2009
adsp-rf-tag = %x72 %x66 *WSP "=" *WSP rep-format *WSP 0*( ":" *WSP
rep-format )
ri= Requested Report Interval (plain-text; OPTIONAL; default is
"0"). The value is an integer which specifies an interval during
which no more than one report about a given type of incident
should be generated. A value of "0" requests a report for every
incident. Where the requested interval is not zero, the agent
generating a report SHOULD include an "Incidents:" header in the
generated report so the receiving agent has some indication of how
many reports were suppressed.
ABNF:
adsp-ri-tag = %x72 %x69 *WSP "=" *WSP 1*DIGIT
ro= Requested Reports (plain-text; OPTIONAL; default is "all"). The
value MUST be a colon-separated list of tokens representing those
conditions under which a report is desired. See Section 5.2 for a
list of valid tags.
ABNF:
adsp-ro-type = ( "all" / "s" / "u" )
adsp-ro-tag = %x72 %x6f *WSP "=" *WSP adsp-ro-type *WSP 0* ( ":"
*WSP adsp-ro-type )
rs= Requested SMTP Error String (plain-text; OPTIONAL; no default).
The value is a string the signing domain requests be included in
SMTP error strings when messages are rejected.
ABNF:
adsp-rs-tag = %x72 %x73 *WSP "=" qp-section
Kucherawy Expires August 1, 2009 [Page 8]
Internet-Draft DKIM Reporting January 2009
5. Requested Reports
This memo also includes, as the "ro" tags defined above, the means by
which the sender can request reports for specific circumstances of
interest. Verifiers MUST NOT generate reports for incidents which do
not match a requested report.
5.1. Requested Reports for DKIM Failures
The following report requests are defined for DKIM keys:
all All reports are requested.
s Reports are requested for signature or key syntax errors.
v Reports are requested for signature verification failures or body
hash mismatches.
x Reports are requested for signatures rejected by the verifier
because the expiration time has passed.
5.2. Requested Reports for DKIM ADSP Failures
The following report requests are defined for DKIM keys:
all All reports are requested.
s Reports are requested for messages for which the ADSP algorithm
determines the message is both signed and Suspicious.
u Reports are requested for messages for which the ADSP algorithm
determines the message is both unsigned and Suspicious.
Kucherawy Expires August 1, 2009 [Page 9]
Internet-Draft DKIM Reporting January 2009
6. Reporting Formats
This section lists reporting formats supported by this DKIM reporting
mechanism. Currently only two formats are supported:
arf: Abuse Reporting Format, as defined in
[I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT], and as extended in
Section 7.
smtp: An SMTP error with a string descriptive of the problem which
caused the DKIM verification to fail. This explicitly requests
evaluation of DKIM concurrent with the SMTP session, and rejection
(if appropriate) whenever possible rather than acceptance of the
message and later generation of a feedback report of some kind
(e.g. "arf" above) when verification fails. The presence of an
"rs" tag (see Section 3 and Section 4) further requests a specific
substring be included in the reply to ease automatic handling of
such errors by sending or relaying MTAs.
Kucherawy Expires August 1, 2009 [Page 10]
Internet-Draft DKIM Reporting January 2009
7. Extension ARF Fields for DKIM Reporting
The current ARF format defined in
[I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT] lacks some specific features
required to do effective DKIM reporting. This section describes the
extensions required to do so and thus required to conform to this
specification.
7.1. New ARF Feedback Type
A new feedback type of "dkim" is defined as an extension to Section
8.2 of [I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT]. See Section 8.3 for
details.
The header names listed in that draft which may appear for this new
feedback type include all shown in the draft except "Relevant-URI"
and "Removal-Recipient" as they have no semantics relating to DKIM.
7.2. New ARF Header Names
The following new ARF header names are defined as extensions to
Section 8.1 of [I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT]:
DKIM-Canonicalized-Body: A base64 encoding of the canonicalized body
of the message as generated by the verifier. This header and
value MUST be present for reports using feedback type "dkim" when
reporting a "bodyhash" failure.
DKIM-Canonicalized-Headers: A base64 encoding of the canonicalized
header of the message as generated by the verifier. This header
and value MUST be present for reports using feedback type "dkim".
DKIM-Failure: Indicates the type of DKIM failure that is being
reported. The list of valid values is enumerated below. This
header and value MUST be present for reports using feedback type
"dkim".
DKIM-Identity: The identity of the signature which failed
verification, taken from the "i=" tag of the signature. This
header and value MUST be present for reports using feedback type
"dkim" when reporting anything other than an "asp" failure.
DKIM-Selector: The selector of the signature which failed
verification, taken from the "s=" tag of the signature. This
header and value MUST be present for reports using feedback type
"dkim" when reporting anything other than an "asp" failure.
Kucherawy Expires August 1, 2009 [Page 11]
Internet-Draft DKIM Reporting January 2009
Incidents: A count of the number of times the cited incident
occurred. This permits a limited form of aggregate reporting
rather than sending one report message per incident. The absence
of this field implies the report refers to a single incident.
The values which are base64 encodings may contain FWS for formatting
purposes as per the usual header field wrapping defined in [MAIL].
During decoding, any characters not in the base64 alphabet are
ignored so that such line wrapping does not harm the value. The ABNF
token "FWS" is defined in [DKIM].
7.3. DKIM Failure Types
The list of defined DKIM failure types, used in the "DKIM-Failure:"
header (defined above), is as follows:
asp: The sender's published signing practises determined the message
is suspicious.
bodyhash: The body hash in the signature and the body hash computed
by the verifier did not match.
granularity: The key referenced by the signature on the message was
not authorized for use by the sender.
revoked: The key referenced by the signature on the message has been
revoked.
signature: The signature on the message did not successfully verify
against the header hash and public key.
Supplementary data may be included in the form of [MAIL]-compliant
comments. For example, "Failure: asp" could be augmented by a
comment to indicate that the failed message was rejected because it
was not signed when it should have been. See Appendix B for
examples.
Kucherawy Expires August 1, 2009 [Page 12]
Internet-Draft DKIM Reporting January 2009
8. IANA Considerations
As required by [IANA-CONSIDERATIONS], this section contains registry
information for the new [DKIM] key tag, the new
[I-D.DRAFT-IETF-DKIM-SSP] tag, and the extensions to
[I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT].
8.1. DKIM Key Tag Registration
IANA is requested to update the DKIM Key Tag Specification Registry
to include the following new items:
+------+-----------------+
| TYPE | REFERENCE |
+------+-----------------+
| r | (this document) |
| rf | (this document) |
| ri | (this document) |
| ro | (this document) |
| rs | (this document) |
+------+-----------------+
8.2. DKIM ADSP Tag Registration
IANA is requested to update the DKIM ADSP Tag Specification Registry
to include the following new items:
+------+-----------------+
| TYPE | REFERENCE |
+------+-----------------+
| r | (this document) |
| rf | (this document) |
| ri | (this document) |
| ro | (this document) |
| rs | (this document) |
+------+-----------------+
8.3. Updates to ARF Feedback Types
The following feedback type is added to the Feedback Report Feedback
Type Registry:
Feedback Type: dkim
Description: DKIM failure report
Registration: (this document)
Kucherawy Expires August 1, 2009 [Page 13]
Internet-Draft DKIM Reporting January 2009
8.4. Updates to ARF Header Names
The following headers are added to the Feedback Report Header Names
Registry:
Field Name: DKIM-Canonicalized-Body
Description: Canonicalized body, per DKIM
Multiple Appearances: No
Related "Feedback-Type": dkim
Field Name: DKIM-Canonicalized-Headers
Description: Canonicalized headers, per DKIM
Multiple Appearances: No
Related "Feedback-Type": dkim
Field Name: DKIM-Failure
Description: Type of DKIM failure
Multiple Appearances: No
Related "Feedback-Type": dkim
Field Name: DKIM-Identity
Description: Identity from DKIM signature
Multiple Appearances: No
Related "Feedback-Type": dkim
Field Name: DKIM-Selector
Description: Selector from DKIM signature
Multiple Appearances: No
Related "Feedback-Type": dkim
Field Name: Incidents
Description: Incident count, for aggregate reporting
Multiple Appearances: No
Related "Feedback-Type": any
Kucherawy Expires August 1, 2009 [Page 14]
Internet-Draft DKIM Reporting January 2009
9. Security Considerations
Security issues with respect to these DKIM reports are similar to
those found in [DSN].
9.1. Forgeries
These reports may be forged as easily as ordinary Internet electronic
mail. User agents and automatic mail handling facilities (such as
mail distribution list exploders) that wish to make automatic use of
DSNs of any kind should take appropriate precautions to minimize the
potential damage from denial-of-service attacks.
Security threats related to forged DSNs include the sending of:
a. A falsified DKIM failure notification when the message was in
fact delivered to the indicated recipient;
b. Falsified signature information, such as selector, domain, etc.
Perhaps the simplest means of mitigating this threat is to assert
that DKIM reports should themselves be signed. On the other hand, if
there's a problem with the DKIM infrastructure at the verifier,
signing DKIM failure reports may produce reports that aren't trusted
or even accepted by their intended recipients.
9.2. Automatic Generation
Automatic generation of these reports by verifying agents can cause a
denial-of-service attack when a large volume of e-mail is sent that
causes DKIM verification failures for whatever reason.
It is unclear what a good solution for this issue is. Limiting the
rate of generation of these messages may be apropos but threatens to
inhibit the distribution of important and possibly time-sensitive
information.
9.3. Envelope Sender Selection
In the case of transmitted DKIM reports in the form of a new message,
it is necessary to construct the message so as to avoid amplification
attacks, deliberate or otherwise. Thus, per Section 2 of [DSN], the
envelope sender address of the DKIM report SHOULD be chosen to ensure
that no delivery status reports will be issued in response to the
DKIM report itself, and MUST be chosen so that these reports will not
generate mail loops. Whenever an SMTP transaction is used to send a
DKIM report, the MAIL FROM command MUST use a NULL return address,
i.e. "MAIL FROM:<>".
Kucherawy Expires August 1, 2009 [Page 15]
Internet-Draft DKIM Reporting January 2009
9.4. Reporting Multiple Incidents
If it is known that a particular host generates abuse reports upon
certain incidents, an attacker could forge a high volume of messages
which will trigger such a report. The recipient of the report could
then be innundated with reports. This could easily be extended to a
distributed denial-of-service attack by finding a number of report-
generating servers.
The incident count referenced in Section 7.2 provides a limited form
of mitigation. The host generating reports may elect to send reports
only periodically, with each report representing a number of
identical or near-identical incidents. One might even do something
inverse-exponentially, sending reports for each of the first ten
incidents, then every tenth incident up to 100, then every 100th
incident up to 1000, etc. until some period of relative quiet after
which the limitation resets.
The use of this for "near-identical" incidents in particular causes a
degradation in reporting quality, however. If for example a large
number of pieces of spam arrive from one attacker, a reporting agent
may decide only to send a report about a fraction of those messages.
While this averts a flood of reports to a system administrator, the
precise details of each incident are similarly not sent.
Kucherawy Expires August 1, 2009 [Page 16]
Internet-Draft DKIM Reporting January 2009
10. References
10.1. Normative References
[DKIM] Allman, E., Callas, J., Delany, M., Libbey, M., Fenton,
J., and M. Thomas, "DomainKeys Identified Mail (DKIM)
Signatures", RFC 4871, May 2007.
[I-D.DRAFT-IETF-DKIM-SSP]
Allman, E., Delany, M., and J. Fenton, "DKIM Sender
Signing Practises", I-D DRAFT-IETF-DKIM-SSP-03.
[I-D.DRAFT-SHAFRANOVICH-FEEDBACK-REPORT]
Shafranovich, Y., Levine, J., Hoffman, P., and M.
Kucherawy, "An Extensible Format for Email Feedback
Reports", I-D DRAFT-SHAFRANOVICH-FEEDBACK-REPORT-04,
March 2008.
[IANA-CONSIDERATIONS]
Alvestrand, H. and T. Narten, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226, May 2008.
[KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[MAIL] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
10.2. Informative References
[DSN] Moore, K. and G. Vaudreuil, "An Extensible Message Format
for Delivery Status Notifications", RFC 3464,
January 2003.
Kucherawy Expires August 1, 2009 [Page 17]
Internet-Draft DKIM Reporting January 2009
Appendix A. Acknowledgements
The author wishes to acknowledge the following for their review and
constructive criticism of this proposal: (add names here)
Kucherawy Expires August 1, 2009 [Page 18]
Internet-Draft DKIM Reporting January 2009
Appendix B. Examples
This section contains examples of the use of each of the extensions
defined by this memo.
B.1. Example Use of DKIM Key Extension Tags
A DKIM key record including use of the extensions defined by this
memo:
v=DKIM1; k=rsa; t=y; r=dkim-errors; rf=arf; ro=v:x; p=MIGfMA0GCS
qGSIb3DQEBAQUAA4GNADCBiQKBgQDh2vbhJTijCs2qbyJcwRCa8WqDTxI+PisFJo
faPtoDJy0Qn41uNayCajfKADVcLqc87sXQS6GxfchPfzx7Vh9crYdxRbN/o/URCu
ZsKmym1i1IPTwRLcXSnuKS0XDs1eRW2WQHGYlXksUDqSHWOS3ZO1W5t/FLcZHpIl
l/80xs4QIDAQAB
Example 1: DKIM key record using these extensions
This example DKIM key record contains the following data in addition
to the basic DKIM key data:
o Reports about signature evaluation failures should be send to the
address "dkim-errors" at the sender's domain;
o The sender's domain requests reports in the "arf" format;
o Only reports about signature verification failures and expired
signatures should be generated.
B.2. Example Use of DKIM ADSP Extension Tags
A DKIM ADSP record including use of the extensions defined by this
memo:
dkim=all; r=dkim-adsp-errors; rf=arf; ro=u
Example 2: DKIM ADSP record using these extensions
This example ADSP record makes the following assertions:
o The sending domain (i.e. the one that is advertising this policy)
signs all mail it sends;
o Reports about ADSP evaluation failures should be send to the
address "dkim-adsp-errors" at the sender's domain;
o The sender's domain requests reports in the "arf" format;
Kucherawy Expires August 1, 2009 [Page 19]
Internet-Draft DKIM Reporting January 2009
o Only reports about unsigned messages should be generated.
B.3. Example Use of ARF Extension Headers
Kucherawy Expires August 1, 2009 [Page 20]
Internet-Draft DKIM Reporting January 2009
Appendix C. Public Discussion
[REMOVE BEFORE PUBLICATION]
Public discussion of this proposed specification is handled via the
mail-vet-discuss@mipassoc.org mailing list. The list is open.
Access to subscription forms and to list archives can be found at
http://mipassoc.org/mailman/listinfo/mail-vet-discuss.
Kucherawy Expires August 1, 2009 [Page 21]
Internet-Draft DKIM Reporting January 2009
Author's Address
Murray S. Kucherawy
Sendmail, Inc.
6475 Christie Ave., Suite 350
Emeryville, CA 94608
US
Phone: +1 510 594 5400
Email: msk+ietf@sendmail.com
Kucherawy Expires August 1, 2009 [Page 22]