Internet Engineering Task Force P. Hallam-Baker Internet-Draft VeriSign Inc Intended status: Informational July 13, 2008 Expires: January 14, 2009 DKIM Extensions draft-hallambaker-dkim-extensions-01 Status of this Memo By submitting this Internet-Draft, each author represents that any 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 aware will be disclosed, in accordance with Section 6 of 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 January 14, 2009. Abstract Optional extensions for DKIM are described. A DKIM Policy statement is defined for the policy 'this zone never sends mail'. The NULL Key Algorithm is defined to simplify management of large zones where most mail is signed but with important exceptions. The X509 key record extension allows the location from which an X.509v3 certificate for the key specified in the record may be obtained. Hallam-Baker Expires January 14, 2009 [Page 1] Internet-Draft DKIM Extensions July 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 2. NoMail Policy . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. NULL Signature Algorithm . . . . . . . . . . . . . . . . . . . 3 4. X509 Certificate Location Extension . . . . . . . . . . . . . . 3 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 8. Normative References . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 4 Intellectual Property and Copyright Statements . . . . . . . . . . 5 Hallam-Baker Expires January 14, 2009 [Page 2] Internet-Draft DKIM Extensions July 2008 1. Introduction 1.1. 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 RFC 2119 [RFC2119]. 2. NoMail Policy The NOMAIL policy is declared in an SSP record using the tag "NOMAIL". No parameters are specified for the NOMAIL policy. If specified the NOMAIL policy states that no mail is sent from the domain to which it is attached. All mail that purports to have been sent by that domain MUST be considered suspicious. 3. NULL Signature Algorithm The NULL Signature algorithm is a DKIM signature algorithm that always produces the same signature value regardless of the message contents. A message signed with the NULL signature MUST be treated as if it were unsigned for all purposes other than verifying compliance with a DKIM policy. For purposes of policy compliance, a message that carries a NULL signature is considered to be compliant if and only if it is consistent with the signing restrictions specified in the key record. A key record that specifies the NULL signature algorithm SHOULD specify usage restricted to specific senders. 4. X509 Certificate Location Extension The x509 key record extension specifies a URL from which a certificate chain corresponding to the key specified in the key record may be obtained. The key chain is specified as a CMS SignedData structure with no data. Hallam-Baker Expires January 14, 2009 [Page 3] Internet-Draft DKIM Extensions July 2008 5. Acknowledgements The ideas in this document arose from extensive discussions with the DKIM working group, in particular Hector Santos and others. 6. IANA Considerations This document requests allocation of a DKIM SSP tag 'NOMAIL' 7. Security Considerations The NOMAIL policy MAY be employed to perform a denial of service attack. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Author's Address Phillip Hallam-Baker VeriSign Inc Email: pbaker@verisign.com Hallam-Baker Expires January 14, 2009 [Page 4] Internet-Draft DKIM Extensions July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Hallam-Baker Expires January 14, 2009 [Page 5]