DKIM Working Group E. Allman
Internet-Draft Sendmail, Inc.
Intended status: Standards Track M. Delany
Expires: March 20, 2008 Yahoo! Inc.
J. Fenton
Cisco Systems, Inc.
September 17, 2007
DKIM Sender Signing Practices
draft-ietf-dkim-ssp-01
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
DomainKeys Identified Mail (DKIM) defines a domain-level
authentication framework for email using public-key cryptography and
key server technology to permit verification of the source and
contents of messages by either Mail Transport Agents (MTAs) or Mail
User Agents (MUAs). The primary DKIM protocol is described in
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[RFC4871].
This document describes the records that senders may use to advertise
how they sign their outgoing mail, and how verifiers should access
and interpret those results.
Requirements Language
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 [RFC2119].
(Unresolved Issues/To Be Done)
Need to consider handling of multiple responses to a DNS query for
the SSP record.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Language and Terminology . . . . . . . . . . . . . . . . . . . 5
2.1. Terms Imported from DKIM Signatures Specification . . . . 5
2.2. Valid Signature . . . . . . . . . . . . . . . . . . . . . 5
2.3. Originator Address . . . . . . . . . . . . . . . . . . . . 5
2.4. Originator Domain . . . . . . . . . . . . . . . . . . . . 6
2.5. Alleged Signer . . . . . . . . . . . . . . . . . . . . . . 6
2.6. Alleged Originator . . . . . . . . . . . . . . . . . . . . 6
2.7. Sender Signing Practices . . . . . . . . . . . . . . . . . 6
2.8. Originator Signature . . . . . . . . . . . . . . . . . . . 6
2.9. Suspicious . . . . . . . . . . . . . . . . . . . . . . . . 6
2.10. Third-Party Signature . . . . . . . . . . . . . . . . . . 7
2.11. Verifier Acceptable Third-Party Signature . . . . . . . . 7
3. Operation Overview . . . . . . . . . . . . . . . . . . . . . . 7
4. Detailed Description . . . . . . . . . . . . . . . . . . . . . 8
4.1. DNS Representation . . . . . . . . . . . . . . . . . . . . 8
4.2. Publication of SSP Records . . . . . . . . . . . . . . . . 9
4.3. Record Syntax . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Sender Signing Practices Check Procedure . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
6.1. Fraudulent Sender Address . . . . . . . . . . . . . . . . 14
6.2. DNS Attacks . . . . . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 15
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 15
B.1. Changes since -ietf-dkim-ssp-00 . . . . . . . . . . . . . 15
B.2. Changes since -allman-ssp-02 . . . . . . . . . . . . . . . 16
B.3. Changes since -allman-ssp-01 . . . . . . . . . . . . . . . 16
B.4. Changes since -allman-ssp-00 . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
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1. Introduction
DomainKeys Identified Mail (DKIM) defines a mechanism by which email
messages can be cryptographically signed, permitting a signing domain
to claim responsibility for the introduction of a message into the
mail stream. Message recipients can verify the signature by querying
the signer's domain directly to retrieve the appropriate public key,
and thereby confirm that the message was attested to by a party in
possession of the private key for the signing domain.
However, the legacy of the Internet is such that not all messages
will be signed, and the absence of a signature on a message is not an
a priori indication of forgery. In fact, during early phases of
deployment it must be expected that most messages will remain
unsigned. However, some domains may choose to sign all of their
outgoing mail, for example, to protect their brand name. It is
highly desirable for such domains to be able to advertise that fact
to verifiers, and that messages claiming to be from them that do not
have a valid signature are likely to be forgeries. This is the topic
for sender signing practices.
In the absence of a valid DKIM signature on behalf of the "From"
address [RFC2822], message verifiers implementing this specification
MUST determine whether messages from that sender are expected to be
signed, and what signatures are acceptable. In particular, whether a
domain signs all outbound email must be made available to the
verifier. Without such a mechanism, the benefit of message signing
techniques such as DKIM is limited since unsigned messages will
always need to be considered to be potentially legitimate. This
determination is referred to as a Sender Signing Practices check.
Conceivably, such expressions might be imagined to be extended in the
future to include information about what hashing algorithms a domain
uses, what kind of messages might be sent (e.g., bulk vs. personal
vs. transactional), etc. Such concerns are out of scope of this
standard, because they can be expressed in the key record
("Selector") with which the signature is verified. In contrast, this
specification focuses on information which is relevant in the absence
of a valid signature. Expressions of signing practice which require
outside auditing are similarly out of scope for this specification
because they fall under the purview of reputation and accreditation.
The detailed requirements for Sender Signing Practices are given in
[I-D.ietf-dkim-ssp-requirements], which the protocol described in
this document attempts to satisfy. This document refers extensively
to [RFC4871], which should be read as a prerequisite to this
document.
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2. Language and Terminology
2.1. Terms Imported from DKIM Signatures Specification
Some terminology used herein is derived directly from [RFC4871].
Briefly,
o A "Signer" is the agent that signs a message. In many cases it
will correspond closely with the original author of the message or
an agent working on the author's behalf.
o A "Verifier" is the agent that verifies a message by checking the
actual signature against the message itself and the public key
published by the Alleged Signer. The Verifier also looks up the
Sender Signing Practices published by the domain of the Originator
Address if the message is not correctly signed by the Alleged
Originator.
o A "Selector" specifies which of the keys published by a signing
domain should be queried. It is essentially a way of subdividing
the address space to allow a single sending domain to publish
multiple keys.
2.2. Valid Signature
A "Valid Signature" is any signature on a message which correctly
verifies using the procedure described in section 6.1 of [RFC4871].
2.3. Originator Address
The "Originator Address" is the email address in the From header
field of a message [RFC2822], or if and only if the From header field
contains multiple addresses, the first address in the From header
field.
NON-NORMATIVE RATIONALE: The alternative option when there are
multiple addresses in the From header field is to use the value of
the Sender header field. This would be closer to the semantics
indicated in [RFC2822] than using the first address in the From
header field. However, the large number of deployed Mail User
Agents that do not display the Sender header field value argues
against that. Multiple addresses in the From header field are
rare in real life.
Even when there is only one address in the From header field, this
address is chosen as the reference address for SSP lookups because
it represents the author of the message and is more widely
displayed by Mail User Agents as a result. The Sender header
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field frequently has other meanings.
2.4. Originator Domain
The "Originator Domain" is everything to the right of the "@" in the
Originator Address (excluding the "@" itself).
2.5. Alleged Signer
An "Alleged Signer" is the identity of the signer claimed in a DKIM-
Signature header field in a message received by a Verifier; it is
"alleged" because it has not yet been verified.
2.6. Alleged Originator
An "Alleged Originator" is the Originator Address of a message
received by a Verifier; it is "alleged" because it has not yet been
verified.
2.7. Sender Signing Practices
"Sender Signing Practices" (or just "practices") consist of a
machine-readable record published by the domain of the Alleged
Originator which includes information about whether or not that
domain signs all of their email, and whether signatures from third
parties are sanctioned by the Alleged Originator.
2.8. Originator Signature
An "Originator Signature" is any Valid Signature where the signing
address (listed in the "i=" tag if present, otherwise its default
value, consisting of the null address, representing an unknown user,
followed by "@", followed by the value of the "d=" tag) matches the
Originator Address. If the signing address does not include a local-
part, then only the domains must match; otherwise, the two addresses
must be identical.
2.9. Suspicious
Messages that do not contain a valid Originator Signature and which
are inconsistent with a Sender Signing Practices check (e.g., are
received without a Valid Signature and the sender's signing practices
indicate all messages from the domain are signed) are referred to as
"Suspicious". The handling of such messages is at the discretion of
the Verifier or final recipient. "Suspicious" applies only to the
DKIM evaluation of the message; a Verifier may decide the message
should be accepted on the basis of other information beyond the scope
of this document. Conversely, messages not deemed Suspicious may be
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rejected for other reasons.
2.10. Third-Party Signature
A "Third-Party Signature" is a Valid Signature which is not an
Originator Signature.
2.11. Verifier Acceptable Third-Party Signature
A Verifier Acceptable Third-Party Signature is a Third-Party
Signature that the Verifier is willing to accept as meaningful for
the message under consideration. The Verifier may use any criteria
it deems appropriate for making this determination.
3. Operation Overview
Sender Signing Practices checks MUST be based on the Originator
Address. If the message contains a valid Originator Signature, no
Sender Signing Practices check need be performed: the Verifier
SHOULD NOT look up the Sender Signing Practices and the message MUST
NOT be considered Suspicious.
Verifiers checking messages that do not have at least one valid
Originator Signature MUST perform a Sender Signing Practices check on
the domain specified by the Originator Address as described in
Section 4.4.
A Sender Signing Practices check produces one of four possible
results:
1. Some messages from this domain are not signed; the message MUST
NOT be considered Suspicious, even in the absence of a valid
signature. This is the default.
2. All messages from this domain are signed. Messages containing a
Verifier Acceptable Third-Party Signature MUST NOT be considered
Suspicious.
NON-NORMATIVE RATIONALE: Third-party signatures, since they
can potentially represent any domain, are considered more
likely to be abused by attackers seeking to spoof a specific
address. It may therefore be desirable for verifiers to apply
other criteria outside the scope of this specification in
deciding to accept a given third-party signature. For
example, a list of known mailing list domains used by
addresses served by the verifier might be specifically
considered acceptable third-party signers.
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3. All valid messages from this domain are signed; the domain of the
Alleged Originator requests that only messages with valid
Originator Signatures be considered not Suspicious; Third-Party
Signatures are irrelevant. This practice would typically be used
by domains which send only transactional email (i.e., do not use
mailing lists and such that are likely to break signatures) and
which wish to emphasize security over deliverability of their
messages. In the absence of a valid Originator Signature, the
message MUST be considered Suspicious.
4. The domain does not exist; the message MUST be considered
Suspicious.
If the Sender Signing Practices record for the domain does not exist
but the domain does exist, Verifier systems MUST assume that some
messages from this domain are not signed and the message MUST NOT be
considered Suspicious.
4. Detailed Description
4.1. DNS Representation
Sender Signing Practices records are published using the DNS TXT
resource record type.
NON-NORMATIVE DISCUSSION: There has been considerable discussion
on the DKIM WG mailing list regarding the relative advantages of
TXT and a new resource record (RR) type. Many DNS server and
resolver implementations are incapable of quickly and easily
supporting new resource record types. For this reason, support of
TXT records is required whether a new RR type is defined or not.
However, without a "flag day" on which SSP TXT record support is
to be withdrawn, such support is likely to continue indefinitely.
As a result, this specification defines no new RR type for SSP.
Another alternative proposed by P. Hallam-Baker is the publication
of both a TXT record and, when implementations permit, a new RR,
referred to as XPTR, which gives the location from which SSP and
other policy information relating to a give domain can be
retrieved. This has the advantage of supporting a variety of
policies in a scalable manner, with better handling of wildcards
and centralized publication of policy records, with caching
advantages. However, the above implementation issues also apply
to XPTR, and an additional lookup is required to retrieve SSP via
the XPTR method. At the time of publication of this draft,
consensus on this proposal was unclear.
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The RDATA for SSP resource records is textual in format, with
specific syntax and semantics relating to their role in describing
sender signing practices. The "Tag=Value List" syntax described in
section 3.2 of [RFC4871] is used. Records not in compliance with
that syntax or the syntax of individual tags described in Section 4.3
MUST be ignored (considered equivalent to a NODATA result) for
purposes of message disposition, although they MAY cause the logging
of warning messages via an appropriate system logging mechanism.
SSP records for a domain are published at a location in the domain's
DNS hierarchy prefixed by _ssp._domainkey; e.g., the SSP record for
example.com would be a TXT record that is published at
_ssp._domainkey.example.com.
4.2. Publication of SSP Records
Sender Signing Practices are intended to apply to all mail sent from
the domain of an Alleged Originator, and to the greatest extent
possible, to all subdomains of that domain. There are several cases
that need to be considered in that regard:
o The domain itself
o Subdomains which may or may not be used for email
o Hostnames which may or may not be used for email
o Other named resource records in the domain
o Multi-level examples of the above, e.g., a.b.example.com
o Non-existent cases, i.e., a subdomain or hostname that does not
actually exist within the domain
Normally, a domain expressing Sender Signing Practices will want to
do so for both itself and all of its "descendents" (child domains and
hosts, at all lower levels). Domains wishing to do so MUST publish
SSP records as follows:
Publish an SSP record for the domain itself
Publish an SSP record for any existing subdomain
Note that since the lookup algorithm described below references the
immediate parent of the alleged originating domain, it is not
necessary to publish SSP records for every single-level label within
the domain. This has been done to relieve domain administrators of
the burden of publishing an SSP record for every other record in the
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domain, which would be otherwise required.
Wildcards within a domain, including but not limited to wildcard MX
records, pose a particular problem. While referencing the immediate
parent domain allows the discovery of an SSP record corresponding to
an unintended immediate-child subdomain, wildcard records apply at
multiple levels. For example, if there is a wildcard MX record for
example.com, the domain foo.bar.example.com can receive mail through
the named mail exchanger. Conversely, the existence of the record
makes it impossible to tell whether foo.bar.example.com is a
legitimate name since a query for that name will not return an
NXDOMAIN error. For that reason, SSP coverage for subdomains of
domains containing a wildcard record is incomplete.
NON-NORMATIVE NOTE: Complete SSP coverage of domains containing
(or where any parent contains) wildcards generally cannot be
guaranteed.
4.3. Record Syntax
SSP records follow the "tag=value" syntax described in section 3.2 of
[RFC4871]. The SSP record syntax is a tag-list as defined in that
section, including the restriction on duplicate tags, the use of
white space, and case sensitivity.
Tags used in SSP records are as follows. Unrecognized tags MUST be
ignored. In the ABNF below, the FWS token is inherited from
[RFC2822] with the exclusion of obs-FWS. The ALPHA and DIGIT tokens
are imported from [RFC4234].
dkim= Outbound signing practices for the domain (plain-text;
REQUIRED). Possible values are as follows:
unknown The domain may sign some or all email.
all All mail from the domain is signed; unsigned email MUST be
considered Suspicious. The domain may send messages through
agents that may modify and re-sign messages, so email signed
with a Verifier Acceptable Third-Party Signature SHOULD NOT be
considered Suspicious.
strict All mail from the domain is signed; messages lacking a
valid Originator Signature MUST be considered Suspicious. The
domain does not expect to send messages through agents that may
modify and re-sign messages.
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NON-NORMATIVE RATIONALE: Strict practices may be used by
entities which send only transactional email to individual
addresses and which are willing to accept the consequence of
having some mail which is re-signed appear suspicious in
return for additional control over their addresses. Strict
practices may also be used by entities which do not send
(and therefore do not sign) any email.
ABNF:
ssp-dkim-tag = "dkim" [FWS] "=" [FWS] ("unknown" /
"all" / "strict")
handling= Non-compliant message handling request for the domain
(plain-text; OPTIONAL). Possible values are as follows:
process Messages which are Suspicious from this domain SHOULD be
processed by the verifier, although the SSP failure MAY be
considered in subsequent evaluation of the message. This is
the default value.
deny Messages which are Suspicious from this domain MAY be
rejected, bounced, or otherwise not delivered at the option of
the verifier.
NON-NORMATIVE EXPLANATION: The "deny" practice is intended
for use by domains that value security over deliverability.
For example, a domain used by a financial institution to
send transactional email, which signs all of its messages,
might consider their concern about phishing messages
purporting to come from their domain to be higher than their
concern about some some legitimate messages not being
delivered. The "handling=deny" practice allows them to
express that concern in a way that can be acted upon by
verifiers, if they so choose.
ABNF:
ssp-handling-tag = "handling" [FWS] "=" [FWS] ("process" /
"deny")
t= Flags, represented as a colon-separated list of names (plain-text;
OPTIONAL, default is that no flags are set). Flag values are:
y The domain is testing signing practices, and the Verifier
SHOULD NOT consider a message suspicious based on the record.
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s The signing practices apply only to the named domain, and not
to subdomains.
ABNF:
ssp-t-tag = %x75 [FWS] "=" [FWS] ssp-t-tag-flag
0*( [FWS] ":" [FWS] ssp-t-tag-flag )
ssp-t-tag-flag = "y" / "s" / hyphenated-word
; for future extension
hyphenated-word = ALPHA [ *(ALPHA / DIGIT / "-")
(ALPHA / DIGIT) ]
Unrecognized flags MUST be ignored.
4.4. Sender Signing Practices Check Procedure
Verifiers MUST produce a result that is semantically equivalent to
applying the following steps in the order listed. In practice,
several of these steps can be performed in parallel in order to
improve performance.
1. If a valid Originator Signature exists, the message is not
Suspicious, and the algorithm terminates.
2. The Verifier MUST query DNS for a TXT record corresponding to
the Originator Domain prefixed by "_ssp._domainkey.". If the
result of this query is a NOERROR response with one or more
answers which are syntactically-valid SSP responses, proceed to
step 7.
3. The Verifier MUST query DNS for an MX record corresponding to
the Originator Domain (with no prefix). This query is made only
to check the existence of the domain name and MAY be done in
parallel with the query made in step 2. If the result of this
query is an NXDOMAIN error, the message is Suspicious and the
algorithm terminates.
NON-NORMATIVE DISCUSSION: Any resource record type could be
used for this query since the existence of a resource record
of any type will prevent an NXDOMAIN error. The choice of MX
for this purpose is because this record type is thought to be
the most common for likely domains, and will therefore result
in a result which can be more readily cached than a negative
result.
4. If the immediate parent of the Originator Domain is a top-level
domain (a domain consisting of a single element such as "com",
"us", or "jp"), then the message is not Suspicious (because no
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SSP record was found) and the algorithm terminates. The
verifier MAY also compare the parent domain against a locally-
maintained list of known address suffixes (e.g., .co.uk) and
terminate the algorithm with a not Suspicious result if the
parent domain matches an entry on the list.
5. The Verifier MUST query DNS for a TXT record for the immediate
parent domain, prefixed with "_ssp._domainkey." If the result
of this query is a NOERROR response with one or more answers
which are syntactically-valid SSP responses, proceed to step 6.
Otherwise, the message is not Suspicious and the algorithm
terminates.
6. If the SSP "t" tag exists in the response and any of the flags
is "s" (indicating it should not apply to a subdomain), the
message is not Suspicious and the algorithm terminates.
7. If the SSP "t" tag exists in the response and any of the flags
is "y" (indicating testing), the message is not Suspicious and
the algorithm terminates.
8. If the value of the SSP "dkim" tag is "unknown", the message is
not Suspicious and the algorithm terminates.
9. If the value of the SSP "dkim" tag is "all", and one or more
Verifier Acceptable Third-Party Signatures are present on the
message, the message is not Suspicious and the algorithm
terminates.
10. The message is Suspicious and the algorithm terminates.
If any of the queries involved in the Sender Signing Practices Check
result in a SERVFAIL error response, the verifier MAY either queue
the message or return an SMTP error indicating a temporary failure.
5. IANA Considerations
IANA is requested to create a "DKIM selector name" registry and to
reserve the selector name "_ssp" to avoid confusion between DKIM key
records and SSP records.
6. Security Considerations
Security considerations in the Sender Signing Practices are mostly
related to attempts on the part of malicious senders to represent
themselves as other senders, often in an attempt to defraud either
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the recipient or the Alleged Originator.
Additional security considerations regarding Sender Signing Practices
may be found in the DKIM threat analysis [RFC4686].
6.1. Fraudulent Sender Address
[[Assuming 3rd party signature is based on Sender header field]] If
the Sender Signing Practices sanction third-party signing, an
attacker can create a message with a From header field of an
arbitrary sender and a legitimately signed Sender header field
6.2. DNS Attacks
An attacker might attack the DNS infrastructure in an attempt to
impersonate SSP records. However, such an attacker is more likely to
attack at a higher level, e.g., redirecting A or MX record lookups in
order to capture traffic that was legitimately intended for the
target domain. Domains concerned about this should use DNSSEC
[RFC4033].
Because SSP operates within the framework of the legacy e-mail
system, the default result in the absence of an SSP record is that
the domain does not sign all of its messages. Therefore, a DNS
attack which is successful in suppressing the SSP response to the
verifier is sufficient to cause the verifier to see unsigned messages
as non-suspicious, even when that is not intended by the alleged
originating domain.
7. References
7.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
[RFC4871] Allman, E., Callas, J., Delany, M., Libbey, M., Fenton,
J., and M. Thomas, "DomainKeys Identified Mail (DKIM)
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Signatures", RFC 4871, May 2007.
7.2. Informative References
[I-D.ietf-dkim-ssp-requirements]
Thomas, M., "Requirements for a DKIM Signing Practices
Protocol", draft-ietf-dkim-ssp-requirements-05 (work in
progress), April 2007.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4686] Fenton, J., "Analysis of Threats Motivating DomainKeys
Identified Mail (DKIM)", RFC 4686, September 2006.
Appendix A. Acknowledgements
The authors wish to thank many members of the ietf-dkim mailing list,
in particular Arvel Hathcock and Eliot Lear, for valuable suggestions
and constructive criticism of earlier versions of this draft.
Appendix B. Change Log
B.1. Changes since -ietf-dkim-ssp-00
o Clarified Operation Overview and eliminated use of Legitimate as
the counterpart of Suspicious since the words have different
meanings.
o Improved discussion (courtesy of Arvel Hathcock) of the use of TXT
records in DNS vs. a new RR type.
o Clarified publication rules for multilevel names.
o Better description of overall record syntax, in particular that
records with unknown tags are considered syntactically correct.
o Clarified Sender Signing Practices Check Procedure, primarily by
use of new term Originator Domain.
o Eliminated section "Third-Party Signatures and Mailing Lists" that
is better included in the DKIM overview document.
o Added "handling" tag to express alleged sending domain's
preference about handling of Suspicious messages.
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o Clarified handling of SERVFAIL error in SSP check.
o Replaced "entity" with "domain", since with the removal of user-
granularity SSP, the only entities having sender signing policies
are domains.
B.2. Changes since -allman-ssp-02
o Removed user-granularity SSP and u= tag.
o Replaced DKIMP resource record with a TXT record.
o Changed name of the primary tag from "p" to "dkim".
o Replaced lookup algorithm with one which traverses upward at most
one level.
o Added description of records which must be published, and effect
of wildcard records within the domain, on SSP.
B.3. Changes since -allman-ssp-01
o Changed term "Sender Signing Policy" to "Sender Signing
Practices".
o Changed query methodology to use a separate DNS resource record
type, DKIMP.
o Changed tag values from SPF-like symbols to words.
o User level policies now default to that of the domain if not
specified.
o Removed the "Compliance" section since we're still not clear on
what goes here.
o Changed the "parent domain" policy to only search up one level
(assumes that subdomains will publish SSP records if appropriate).
o Added detailed description of SSP check procedure.
B.4. Changes since -allman-ssp-00
From a "diff" perspective, the changes are extensive. Semantically,
the changes are:
o Added section on "Third-Party Signatures and Mailing Lists"
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o Added "Compliance" (transferred from -base document). I'm not
clear on what needs to be done here.
o Extensive restructuring.
Authors' Addresses
Eric Allman
Sendmail, Inc.
6475 Christie Ave, Suite 350
Emeryville, CA 94608
USA
Phone: +1 510 594 5501
Email: eric+dkim@sendmail.org
URI:
Mark Delany
Yahoo! Inc.
701 First Avenue
Sunnyvale, CA 94089
USA
Phone: +1 408 349 6831
Email: markd+dkim@yahoo-inc.com
URI:
Jim Fenton
Cisco Systems, Inc.
MS SJ-9/2
170 W. Tasman Drive
San Jose, CA 95134-1706
USA
Phone: +1 408 526 5914
Email: fenton@cisco.com
URI:
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