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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (March 19, 2018) is 2222 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- -- Looks like a reference, but probably isn't: '1' on line 243 == Outdated reference: A later version (-23) exists of draft-ietf-dmarc-arc-protocol-11 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DMARC Working Group K. Andersen 3 Internet-Draft LinkedIn 4 Intended status: Experimental S. Blank, Ed. 5 Expires: September 20, 2018 ValiMail 6 J. Levine, Ed. 7 Taughannock Networks 8 March 19, 2018 10 Using Multiple Signing Algorithms with the ARC (Authenticated Received 11 Chain) Protocol 12 draft-ietf-dmarc-arc-multi-01 14 Abstract 16 The Authenticated Received Chain (ARC) protocol creates a mechanism 17 whereby a series of handlers of an email message can conduct 18 authentication of the email message as it passes among them on the 19 way to its destination. 21 Initial development of ARC has been done with a single allowed 22 signing algorithm, but parallel work in the DCRUP working group 23 (https://datatracker.ietf.org/wg/dcrup/about/) is expanding the 24 supported algorithms. This specification defines how to extend ARC 25 for multiple signing algorithms. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on September 20, 2018. 44 Copyright Notice 46 Copyright (c) 2018 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (https://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3. Definitions and Terminology . . . . . . . . . . . . . . . . . 3 64 4. Supporting Alternate Signing Algorithms . . . . . . . . . . . 3 65 5. General Approach . . . . . . . . . . . . . . . . . . . . . . 3 66 5.1. Signers . . . . . . . . . . . . . . . . . . . . . . . . . 3 67 5.2. Validators . . . . . . . . . . . . . . . . . . . . . . . 4 68 6. Phases of Algorithm Evolution . . . . . . . . . . . . . . . . 4 69 6.1. Introductory Period . . . . . . . . . . . . . . . . . . . 4 70 6.2. Co-Existence Period . . . . . . . . . . . . . . . . . . . 4 71 6.3. Deprecation Period . . . . . . . . . . . . . . . . . . . 4 72 6.4. Obsolescence Period . . . . . . . . . . . . . . . . . . . 4 73 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 74 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 75 9. Security Considerations . . . . . . . . . . . . . . . . . . . 5 76 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 77 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 78 10.2. Informative References . . . . . . . . . . . . . . . . . 5 79 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6 80 Appendix B. Comments and Feedback . . . . . . . . . . . . . . . 6 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 83 1. Introduction 85 The Authenticated Received Chain (ARC) protocol adds a traceable 86 chain of signatures that cover the handling of an email message 87 through a chain of intermediary handlers. 89 Initial development of ARC has been done with a single allowed 90 signing algorithm, but parallel work in the DCRUP working group 91 (https://datatracker.ietf.org/wg/dcrup/about/) is expanding the 92 supported algorithms. This specification defines how to extend ARC 93 for multiple signing algorithms. 95 2. Overview 97 In order to phase in new signing algorithms, this specification 98 identifies how signers and validators process ARC sets found in email 99 messages. 101 3. Definitions and Terminology 103 This section defines terms used in the rest of the document. 105 The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", 106 "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and 107 "OPTIONAL" in this document are to be interpreted as described in 108 [RFC2119]. 110 Because many of the core concepts and definitions are found in 111 [RFC5598], readers should to be familiar with the contents of 112 [RFC5598], and in particular, the potential roles of intermediaries 113 in the delivery of email and the problems [RFC7960] created by the 114 initial DMARC [RFC7489] . 116 4. Supporting Alternate Signing Algorithms 118 During a period where multiple algorithms are allowed, all of the 119 statements in the ARC spec which refer to "exactly one set of ARC 120 headers per instance" need to be understood as "at least one set per 121 instance and no more than one set per instance per algorithm". 123 5. General Approach 125 5.1. Signers 127 There is a separate independent signing chain for each signing 128 algorithm. Hence, when creating an ARC signature, a signer MUST 129 include only other signatures that use the same algorithm as the 130 signature being created. 132 Wnen signing a message with no previous ARC signatures, signers MUST 133 sign using all supported algorithms. 135 A signer MUST continue the longest ARC chain(s) in a message with all 136 algorithms that it supports. That is, if at least one of the longest 137 chains uses an algorithm that a signer supports, the signer continues 138 the chain(s). If none of the longest chains in a message use an 139 algorithm supported by a signer, the signer MUST NOT extend any 140 chains, even if a shorter chain does use a supported algorithm. 142 5.2. Validators 144 A validator MUST use the longest ARC chain(s) on the message. If a 145 validator cannot interpret the signing algorithm on any of the 146 longest chains, validation fails, evven if a shorter chain does use a 147 supported algorithm. 149 If there is more than one longest chain, the overall result reported 150 can be that of of any of the validations. The result used when 151 extending an ARC chain MUST be the result from validating that chain. 153 6. Phases of Algorithm Evolution 155 6.1. Introductory Period 157 Intermediaries MUST be able to validate ARC chains built with either 158 algorithm but MAY create ARC sets with either (or both) algorithm. 160 The introductory period should be at least six (6) months. 162 6.2. Co-Existence Period 164 Intermediaries MUST be able to validate ARC chains build with either 165 algorithm and MUST create ARC sets with both algorithms. Chains 166 ending with either algorithm may be used for the result. 168 6.3. Deprecation Period 170 ARC sets built with algorithms that are being deprecated MAY be 171 considered valid within an ARC chain, however, intermediaries MUST 172 NOT create additional sets with the deprecated algorithm. 174 The deprecation period should be at least two (2) years. 176 6.4. Obsolescence Period 178 ARC sets built with algorithms that are obsolete MUST NOT be 179 considered valid within an ARC chain. Intermediaries MUST NOT create 180 any sets with any obsoleted algorithm. 182 7. Privacy Considerations 184 No unique privacy considerations are introduced by this specification 185 beyond those of the base [ARC-DRAFT-11] protocol. 187 8. IANA Considerations 189 No new IANA considerations are introduced by this specification. 191 9. Security Considerations 193 No new security considerations are introduced by this specification 194 beyond those of the base [ARC-DRAFT-11] protocol. 196 10. References 198 10.1. Normative References 200 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 201 Requirement Levels", BCP 14, RFC 2119, 202 DOI 10.17487/RFC2119, March 1997, 203 . 205 [RFC5598] Crocker, D., "Internet Mail Architecture", RFC 5598, 206 DOI 10.17487/RFC5598, July 2009, 207 . 209 10.2. Informative References 211 [ARC-DRAFT-11] 212 Andersen, K., Long, B., and S. Jones, "Authenticated 213 Received Chain (ARC) Protocol (I-D-11)", n.d., 214 . 217 [RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based 218 Message Authentication, Reporting, and Conformance 219 (DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015, 220 . 222 [RFC7960] Martin, F., Ed., Lear, E., Ed., Draegen. Ed., T., Zwicky, 223 E., Ed., and K. Andersen, Ed., "Interoperability Issues 224 between Domain-based Message Authentication, Reporting, 225 and Conformance (DMARC) and Indirect Email Flows", 226 RFC 7960, DOI 10.17487/RFC7960, September 2016, 227 . 229 10.3. URIs 231 [1] mailto:dmarc@ietf.org 233 Appendix A. Acknowledgements 235 This draft is the work of DMARC Working Group. 237 Grateful appreciation is extended to the people who provided feedback 238 through the discuss mailing list. 240 Appendix B. Comments and Feedback 242 Please address all comments, discussions, and questions to 243 dmarc@ietf.org [1]. 245 Authors' Addresses 247 Kurt Andersen 248 LinkedIn 249 1000 West Maude Ave 250 Sunnyvale, California 94085 251 US 253 Email: kurta@linkedin.com 255 Seth Blank (editor) 256 ValiMail 257 Montgomery 258 San Francisco, California 259 US 261 Email: seth@valimail.com 263 John Levine (editor) 264 Taughannock Networks 265 PO Box 727 266 Trumansburg, New York 267 US 269 Email: standards@taugh.com