draft-ietf-dkim-ssp-05.txt   draft-ietf-dkim-ssp-06.txt 
Network Working Group E. Allman Network Working Group E. Allman
Internet-Draft Sendmail, Inc. Internet-Draft Sendmail, Inc.
Intended status: Standards Track J. Fenton Intended status: Standards Track J. Fenton
Expires: February 6, 2009 Cisco Systems, Inc. Expires: March 23, 2009 Cisco Systems, Inc.
M. Delany M. Delany
Yahoo! Inc. Yahoo! Inc.
J. Levine J. Levine
Taughannock Networks Taughannock Networks
August 5, 2008 September 19, 2008
DKIM Author Domain Signing Practices (ADSP) DKIM Author Domain Signing Practices (ADSP)
draft-ietf-dkim-ssp-05 draft-ietf-dkim-ssp-06
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
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This Internet-Draft will expire on February 6, 2009. This Internet-Draft will expire on March 23, 2009.
Abstract Abstract
DomainKeys Identified Mail (DKIM) defines a domain-level DomainKeys Identified Mail (DKIM) defines a domain-level
authentication framework for email to permit verification of the authentication framework for email to permit verification of the
source and contents of messages. This document specifies an adjunct source and contents of messages. This document specifies an adjunct
mechanism to aid in assessing messages that do not contain a DKIM mechanism to aid in assessing messages that do not contain a DKIM
signature for the domain used in the author's address. It defines a signature for the domain used in the author's address. It defines a
record that can advertise whether a domain signs its outgoing mail, record that can advertise whether a domain signs its outgoing mail,
and how other hosts can access that record. and how other hosts can access that record.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Language and Terminology . . . . . . . . . . . . . . . . . . . 3 2. Language and Terminology . . . . . . . . . . . . . . . . . . . 4
2.1. Terms Imported from DKIM Signatures Specification . . . . 3 2.1. Terms Imported from DKIM Signatures Specification . . . . 4
2.2. Valid Signature . . . . . . . . . . . . . . . . . . . . . 4 2.2. Valid Signature . . . . . . . . . . . . . . . . . . . . . 5
2.3. Author Address . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Author Address . . . . . . . . . . . . . . . . . . . . . . 5
2.4. Author Domain . . . . . . . . . . . . . . . . . . . . . . 4 2.4. Author Domain . . . . . . . . . . . . . . . . . . . . . . 5
2.5. Alleged Author . . . . . . . . . . . . . . . . . . . . . . 4 2.5. Alleged Author . . . . . . . . . . . . . . . . . . . . . . 5
2.6. Author Domain Signing Practices . . . . . . . . . . . . . 4 2.6. Author Domain Signing Practices . . . . . . . . . . . . . 5
2.7. Author Signature . . . . . . . . . . . . . . . . . . . . . 4 2.7. Author Signature . . . . . . . . . . . . . . . . . . . . . 5
3. Operation Overview . . . . . . . . . . . . . . . . . . . . . . 5 3. Operation Overview . . . . . . . . . . . . . . . . . . . . . . 6
3.1. ADSP Applicability . . . . . . . . . . . . . . . . . . . . 5 3.1. ADSP Applicability . . . . . . . . . . . . . . . . . . . . 6
3.2. ADSP Usage . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. ADSP Usage . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. ADSP Results . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. ADSP Results . . . . . . . . . . . . . . . . . . . . . . . 7
4. Detailed Description . . . . . . . . . . . . . . . . . . . . . 6 4. Detailed Description . . . . . . . . . . . . . . . . . . . . . 7
4.1. DNS Representation . . . . . . . . . . . . . . . . . . . . 6 4.1. DNS Representation . . . . . . . . . . . . . . . . . . . . 7
4.2. Publication of ADSP Records . . . . . . . . . . . . . . . 7 4.2. Publication of ADSP Records . . . . . . . . . . . . . . . 8
4.3. ADSP Lookup Procedure . . . . . . . . . . . . . . . . . . 7 4.3. ADSP Lookup Procedure . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5.1. ADSP Specification Tag Registry . . . . . . . . . . . . . 9 5.1. ADSP Specification Tag Registry . . . . . . . . . . . . . 10
5.2. ADSP Outbound Signing Practices Registry . . . . . . . . . 9 5.2. ADSP Outbound Signing Practices Registry . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6.1. ADSP Threat Model . . . . . . . . . . . . . . . . . . . . 10 6.1. ADSP Threat Model . . . . . . . . . . . . . . . . . . . . 11
6.2. DNS Attacks . . . . . . . . . . . . . . . . . . . . . . . 10 6.2. DNS Attacks . . . . . . . . . . . . . . . . . . . . . . . 11
6.3. DNS Wildcards . . . . . . . . . . . . . . . . . . . . . . 11 6.3. DNS Wildcards . . . . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. References - Normative . . . . . . . . . . . . . . . . . . 11 7.1. References - Normative . . . . . . . . . . . . . . . . . . 12
7.2. References - Informative . . . . . . . . . . . . . . . . . 12 7.2. References - Informative . . . . . . . . . . . . . . . . . 13
Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 12 Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 13
A.1. Single Location Domains . . . . . . . . . . . . . . . . . 12 A.1. Single Location Domains . . . . . . . . . . . . . . . . . 13
A.2. Bulk Mailing Domains . . . . . . . . . . . . . . . . . . . 13 A.2. Bulk Mailing Domains . . . . . . . . . . . . . . . . . . . 14
A.3. Bulk Mailing Domains with Discardable Mail . . . . . . . . 13 A.3. Bulk Mailing Domains with Discardable Mail . . . . . . . . 14
A.4. Third Party Senders . . . . . . . . . . . . . . . . . . . 13 A.4. Third Party Senders . . . . . . . . . . . . . . . . . . . 14
A.5. Domains with Independent Users and Liberal Use Policies . 14 A.5. Domains with Independent Users and Liberal Use Policies . 15
A.6. Non-email Domains . . . . . . . . . . . . . . . . . . . . 14 A.6. Non-email Domains . . . . . . . . . . . . . . . . . . . . 15
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 14 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 15
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 14 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 15
C.1. Changes since -ietf-dkim-04 . . . . . . . . . . . . . . . 14 C.1. Changes since -ietf-dkim-05 . . . . . . . . . . . . . . . 15
C.2. Changes since -ietf-dkim-03 . . . . . . . . . . . . . . . 14 C.2. Changes since -ietf-dkim-04 . . . . . . . . . . . . . . . 15
C.3. Changes since -ietf-dkim-02 . . . . . . . . . . . . . . . 15 C.3. Changes since -ietf-dkim-03 . . . . . . . . . . . . . . . 16
C.4. Changes since -ietf-dkim-ssp-01 . . . . . . . . . . . . . 16 C.4. Changes since -ietf-dkim-02 . . . . . . . . . . . . . . . 16
C.5. Changes since -ietf-dkim-ssp-00 . . . . . . . . . . . . . 17 C.5. Changes since -ietf-dkim-ssp-01 . . . . . . . . . . . . . 17
C.6. Changes since -allman-ssp-02 . . . . . . . . . . . . . . . 17 C.6. Changes since -ietf-dkim-ssp-00 . . . . . . . . . . . . . 18
C.7. Changes since -allman-ssp-01 . . . . . . . . . . . . . . . 18 C.7. Changes since -allman-ssp-02 . . . . . . . . . . . . . . . 19
C.8. Changes since -allman-ssp-00 . . . . . . . . . . . . . . . 18 C.8. Changes since -allman-ssp-01 . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 C.9. Changes since -allman-ssp-00 . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
Intellectual Property and Copyright Statements . . . . . . . . . . 21
1. Introduction 1. Introduction
DomainKeys Identified Mail (DKIM) defines a mechanism by which email DomainKeys Identified Mail (DKIM) defines a mechanism by which email
messages can be cryptographically signed, permitting a signing domain messages can be cryptographically signed, permitting a signing domain
to claim responsibility for the introduction of a message into the to claim responsibility for the introduction of a message into the
mail stream. Message recipients can verify the signature by querying mail stream. Message recipients can verify the signature by querying
the signer's domain directly to retrieve the appropriate public key, the signer's domain directly to retrieve the appropriate public key,
and thereby confirm that the message was attested to by a party in and thereby confirm that the message was attested to by a party in
possession of the private key for the signing domain. possession of the private key for the signing domain.
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satisfy ADSP. satisfy ADSP.
3. Operation Overview 3. Operation Overview
Domain owners can publish ADSP information via a query mechanism such Domain owners can publish ADSP information via a query mechanism such
as the Domain Name System; specific details are given in Section 4.1. as the Domain Name System; specific details are given in Section 4.1.
Hosts can look up the ADSP information of the domain(s) specified by Hosts can look up the ADSP information of the domain(s) specified by
the Author Address(es) as described in Section 4.3. If a message has the Author Address(es) as described in Section 4.3. If a message has
multiple Author Addresses the ADSP lookups SHOULD be performed multiple Author Addresses the ADSP lookups SHOULD be performed
independently on each address. This standard does not address the independently on each address. This document does not address the
process a host might use to combine the lookup results. process a host might use to combine the lookup results.
3.1. ADSP Applicability 3.1. ADSP Applicability
ADSP as defined in this document is bound to DNS. For this reason, ADSP as defined in this document is bound to DNS. For this reason,
ADSP is applicable only to Author Domains with appropriate DNS ADSP is applicable only to Author Domains with appropriate DNS
records (see Note below). The handling of other Author Domains is records (see Note below). The handling of other Author Domains is
outside the scope of this document. However, attackers may use such outside the scope of this document. However, attackers may use such
domain names in a deliberate attempt to sidestep an organization's domain names in a deliberate attempt to sidestep an organization's
ADSP policy statements. It is up to the ADSP checker implementation ADSP policy statements. It is up to the ADSP checker implementation
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results: results:
o Messages from this domain might or might not have an author o Messages from this domain might or might not have an author
signature. This is the default if the domain exists in the DNS signature. This is the default if the domain exists in the DNS
but no record is found. but no record is found.
o All messages from this domain are signed. o All messages from this domain are signed.
o All messages from this domain are signed and discardable. o All messages from this domain are signed and discardable.
o The domain is not a valid mail domain. o This domain is out of scope.
4. Detailed Description 4. Detailed Description
4.1. DNS Representation 4.1. DNS Representation
ADSP records are published using the DNS TXT resource record type. ADSP records are published using the DNS TXT resource record type.
The RDATA for ADSP resource records is textual in format, with The RDATA for ADSP resource records is textual in format, with
specific syntax and semantics relating to their role in describing specific syntax and semantics relating to their role in describing
ADSP. The "Tag=Value List" syntax described in section 3.2 of ADSP. The "Tag=Value List" syntax described in section 3.2 of
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4.3. ADSP Lookup Procedure 4.3. ADSP Lookup Procedure
Hosts doing an ADSP lookup MUST produce a result that is semantically Hosts doing an ADSP lookup MUST produce a result that is semantically
equivalent to applying the following steps in the order listed below. equivalent to applying the following steps in the order listed below.
In practice, these steps can be performed in parallel in order to In practice, these steps can be performed in parallel in order to
improve performance. However, implementations SHOULD avoid doing improve performance. However, implementations SHOULD avoid doing
unnecessary DNS lookups. unnecessary DNS lookups.
For the purposes of this section a "valid ADSP record" is one that is For the purposes of this section a "valid ADSP record" is one that is
both syntactically and semantically correct; in particular, it both syntactically and semantically correct; in particular, it
matches the ABNF for a "tag-list" and includes a valid "dkim" tag. matches the ABNF for a "tag-list" and starts with a valid "dkim" tag.
Check Domain Scope: An ADSP checker implementation MUST determine Check Domain Scope: An ADSP checker implementation MUST determine
whether a given Author Domain is within scope for ADSP. Given the whether a given Author Domain is within scope for ADSP. Given the
background in Section 3.1 the checker MUST decide which degree of background in Section 3.1 the checker MUST decide which degree of
approximation is acceptable. The checker MUST return an approximation is acceptable. The checker MUST return an
appropriate error result for Author Domains that are outside the appropriate error result for Author Domains that are outside the
scope of ADSP. scope of ADSP.
The host MUST perform a DNS query for a record corresponding to The host MUST perform a DNS query for a record corresponding to
the Author Domain (with no prefix). The type of the query can be the Author Domain (with no prefix). The type of the query can be
of any type, since this step is only to determine if the domain of any type, since this step is only to determine if the domain
itself exists in DNS. This query MAY be done in parallel with the itself exists in DNS. This query MAY be done in parallel with the
query to fetch the Named ADSP Record. If the result of this query query to fetch the named ADSP Record. If the result of this query
is that the Author domain does not exist in the DNS (often called is that the Author domain does not exist in the DNS (often called
an "NXDOMAIN" error), the algorithm MUST terminate with an error an "NXDOMAIN" error, rcode=3 in [RFC1035]), the algorithm MUST
indicating that the domain is out of scope. terminate with an error indicating that the domain is out of
scope.
NON-NORMATIVE DISCUSSION: Any resource record type could be NON-NORMATIVE DISCUSSION: Any resource record type could be
used for this query since the existence of a resource record of used for this query since the existence of a resource record of
any type will prevent an "NXDOMAIN" error. MX is a reasonable any type will prevent an "NXDOMAIN" error. MX is a reasonable
choice for this purpose because this record type is thought to choice for this purpose because this record type is thought to
be the most common for domains used in e-mail, and will be the most common for domains used in e-mail, and will
therefore produce a result which can be more readily cached therefore produce a result which can be more readily cached
than a negative result. than a negative result.
If the domain does exist, the checker MAY make more extensive If the domain does exist, the checker MAY make more extensive
checks to verify the existence of the domain, such as the ones checks to verify the existence of the domain, such as the ones
described in Section 5 of [RFC2821]. If those checks indicate described in Section 5 of [RFC2821]. If those checks indicate
that the Author domain does not exist for mail, e.g., the domain that the Author domain does not exist for mail, e.g., the domain
has no MX, A, or AAAA record, the checker SHOULD terminate with an has no MX, A, or AAAA record, the checker SHOULD terminate with an
error indicating that the domain is out of scope. error indicating that the domain is out of scope.
Fetch Named ADSP Record: The host MUST query DNS for a TXT record Fetch Named ADSP Record: The host MUST query DNS for a TXT record
corresponding to the Author Domain prefixed by "_adsp._domainkey." corresponding to the Author Domain prefixed by "_adsp._domainkey."
(note the trailing dot). (note the trailing dot).
If the result of this query is a "NOERROR" response with an answer If the result of this query is a "NOERROR" response (rcode=0 in
which is a valid ADSP record, use that record, and the algorithm [RFC1035]) with an answer which is a valid ADSP record, use that
terminates. record, and the algorithm terminates.
If a query results in a "SERVFAIL" error response, the algorithm If a query results in a "SERVFAIL" error response (rcode=2 in
terminates without returning a result; possible actions include [RFC1035]), the algorithm terminates without returning a result;
queuing the message or returning an SMTP error indicating a possible actions include queuing the message or returning an SMTP
temporary failure. error indicating a temporary failure.
5. IANA Considerations 5. IANA Considerations
ADSP adds the following namespaces to the IANA registry. In all ADSP adds the following namespaces to the IANA registry. In all
cases, new values are assigned only for values that have been cases, new values are assigned only for values that have been
documented in a published RFC that has IETF Consensus [RFC5226]. documented in a published RFC after IETF Review as specified in
[RFC5226].
5.1. ADSP Specification Tag Registry 5.1. ADSP Specification Tag Registry
An ADSP record provides for a list of specification tags. IANA has An ADSP record provides for a list of specification tags. IANA has
established the ADSP Specification Tag Registry for specification established the ADSP Specification Tag Registry for specification
tags that can be used in ADSP fields. tags that can be used in ADSP fields.
The initial entry in the registry is: The initial entry in the registry is:
+------+-----------------+ +------+-----------------+
| TYPE | REFERENCE | | TYPE | REFERENCE |
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the "_adsp._domainkey." prefix on ADSP records does not allow the "_adsp._domainkey." prefix on ADSP records does not allow
publication of wildcard records that cover ADSP records without also publication of wildcard records that cover ADSP records without also
covering non-ADSP records, nor of wildcard records that cover non- covering non-ADSP records, nor of wildcard records that cover non-
ADSP records without also covering ADSP records. Hence a domain MUST ADSP records without also covering ADSP records. Hence a domain MUST
NOT publish wildcard ADSP records. NOT publish wildcard ADSP records.
7. References 7. References
7.1. References - Normative 7.1. References - Normative
[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 [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.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001. April 2001.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005. RFC 4033, March 2005.
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This document greatly benefited from comments by Steve Atkins, Jon This document greatly benefited from comments by Steve Atkins, Jon
Callas, Dave Crocker, JD Falk, Arvel Hathcock, Ellen Siegel, Michael Callas, Dave Crocker, JD Falk, Arvel Hathcock, Ellen Siegel, Michael
Thomas, and Wietse Venema. Thomas, and Wietse Venema.
Appendix C. Change Log Appendix C. Change Log
*NOTE TO RFC EDITOR: This section may be removed upon publication of *NOTE TO RFC EDITOR: This section may be removed upon publication of
this document as an RFC.* this document as an RFC.*
C.1. Changes since -ietf-dkim-04 C.1. Changes since -ietf-dkim-05
Minor editorial nits: define NOERROR, SERVFAIL, NXDOMAIN as rfc1035
rcodes, change some punctuation, IANA section change IETF Consensus
to the new IETF Review.
C.2. Changes since -ietf-dkim-04
o Require dkim at the front of each record. o Require dkim at the front of each record.
o Disparage wildcard records. o Disparage wildcard records.
o Changed ABNF use of whitespace from FWS back to WSP, dkim-base is o Changed ABNF use of whitespace from FWS back to WSP, dkim-base is
wrong. wrong.
o RFC 2434 -> 5226, make ref to 4686 informational since it's not o RFC 2434 -> 5226, make ref to 4686 informational since it's not
standards track. standards track.
o Improve examples with material from Ellen. o Improve examples with material from Ellen.
C.2. Changes since -ietf-dkim-03 C.3. Changes since -ietf-dkim-03
o Name change for title and filename, to be ADSP o Name change for title and filename, to be ADSP
o String changes throughout, to author Domain signing practices and o String changes throughout, to author Domain signing practices and
to aDsp. to aDsp.
o Added some keywords. o Added some keywords.
o Clarified comparison of local part and domain in Author Address. o Clarified comparison of local part and domain in Author Address.
o Streamlined the Abstract. o Streamlined the Abstract.
o Revised text of last bullet in Results list. o Revised text of last bullet in Results list.
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o Revised wildcard text. o Revised wildcard text.
o Removed 't' tag. o Removed 't' tag.
o Removed ADSP Flags Registry section. o Removed ADSP Flags Registry section.
o Changed ABNF use of whitespace from WSP back to FWS, for o Changed ABNF use of whitespace from WSP back to FWS, for
consistency with dkim-base. consistency with dkim-base.
C.3. Changes since -ietf-dkim-02 C.4. Changes since -ietf-dkim-02
o Merge in more text from ADSP draft. o Merge in more text from ADSP draft.
o Phrase actions as host's rather than checker. o Phrase actions as host's rather than checker.
o Explanatory description of i= matching. o Explanatory description of i= matching.
o Lookup procedure consistently refers to one ADSP record per o Lookup procedure consistently refers to one ADSP record per
lookup. lookup.
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o Simplify imports of terms from other RFCs, add Local-part, 4234 -> o Simplify imports of terms from other RFCs, add Local-part, 4234 ->
5234. 5234.
o Add usage example appendix. o Add usage example appendix.
o Add IANA considerations. o Add IANA considerations.
o Update authors list o Update authors list
C.4. Changes since -ietf-dkim-ssp-01 C.5. Changes since -ietf-dkim-ssp-01
o Reworded introduction for clarity. o Reworded introduction for clarity.
o Various definition clarifications. o Various definition clarifications.
o Changed names of practices to unknown, all, and discardable. o Changed names of practices to unknown, all, and discardable.
o Removed normative language mandating use of SSP in particular o Removed normative language mandating use of SSP in particular
situations (issue 1538). situations (issue 1538).
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o Introduced the concepts of "SSP Checker" and "Evaluator". o Introduced the concepts of "SSP Checker" and "Evaluator".
o Multiple author case now handled my separate invocations of SSP o Multiple author case now handled my separate invocations of SSP
checker by Evaluator (issue 1525). checker by Evaluator (issue 1525).
o Removed check to avoid querying top-level domains. o Removed check to avoid querying top-level domains.
o Changed ABNF use of whitespace from [FWS] to *WSP (partially o Changed ABNF use of whitespace from [FWS] to *WSP (partially
addresses issue 1543). addresses issue 1543).
C.5. Changes since -ietf-dkim-ssp-00 C.6. Changes since -ietf-dkim-ssp-00
o Clarified Operation Overview and eliminated use of Legitimate as o Clarified Operation Overview and eliminated use of Legitimate as
the counterpart of Suspicious since the words have different the counterpart of Suspicious since the words have different
meanings. meanings.
o Improved discussion (courtesy of Arvel Hathcock) of the use of TXT o Improved discussion (courtesy of Arvel Hathcock) of the use of TXT
records in DNS vs. a new RR type. records in DNS vs. a new RR type.
o Clarified publication rules for multilevel names. o Clarified publication rules for multilevel names.
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o Added "handling" tag to express alleged sending domain's o Added "handling" tag to express alleged sending domain's
preference about handling of Suspicious messages. preference about handling of Suspicious messages.
o Clarified handling of SERVFAIL error in SSP check. o Clarified handling of SERVFAIL error in SSP check.
o Replaced "entity" with "domain", since with the removal of user- o Replaced "entity" with "domain", since with the removal of user-
granularity SSP, the only entities having sender signing policies granularity SSP, the only entities having sender signing policies
are domains. are domains.
C.6. Changes since -allman-ssp-02 C.7. Changes since -allman-ssp-02
o Removed user-granularity SSP and u= tag. o Removed user-granularity SSP and u= tag.
o Replaced DKIMP resource record with a TXT record. o Replaced DKIMP resource record with a TXT record.
o Changed name of the primary tag from "p" to "dkim". o Changed name of the primary tag from "p" to "dkim".
o Replaced lookup algorithm with one which traverses upward at most o Replaced lookup algorithm with one which traverses upward at most
one level. one level.
o Added description of records to be published, and effect of o Added description of records to be published, and effect of
wildcard records within the domain, on SSP. wildcard records within the domain, on SSP.
C.7. Changes since -allman-ssp-01 C.8. Changes since -allman-ssp-01
o Changed term "Sender Signing Policy" to "Sender Signing o Changed term "Sender Signing Policy" to "Sender Signing
Practices". Practices".
o Changed query methodology to use a separate DNS resource record o Changed query methodology to use a separate DNS resource record
type, DKIMP. type, DKIMP.
o Changed tag values from SPF-like symbols to words. o Changed tag values from SPF-like symbols to words.
o User level policies now default to that of the domain if not o User level policies now default to that of the domain if not
specified. specified.
o Removed the "Compliance" section since we're still not clear on o Removed the "Compliance" section since we're still not clear on
what goes here. what goes here.
o Changed the "parent domain" policy to only search up one level o Changed the "parent domain" policy to only search up one level
(assumes that subdomains will publish SSP records if appropriate). (assumes that subdomains will publish SSP records if appropriate).
o Added detailed description of SSP check procedure. o Added detailed description of SSP check procedure.
C.8. Changes since -allman-ssp-00 C.9. Changes since -allman-ssp-00
From a "diff" perspective, the changes are extensive. Semantically, From a "diff" perspective, the changes are extensive. Semantically,
the changes are: the changes are:
o Added section on "Third-Party Signatures and Mailing Lists" o Added section on "Third-Party Signatures and Mailing Lists"
o Added "Compliance" (transferred from -base document). I'm not o Added "Compliance" (transferred from -base document). I'm not
clear on what needs to be done here. clear on what needs to be done here.
o Extensive restructuring. o Extensive restructuring.
 End of changes. 23 change blocks. 
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