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Levine 3 Internet-Draft Taughannock Networks 4 Updates: 5321 (if approved) January 26, 2019 5 Intended status: Standards Track 6 Expires: July 30, 2019 8 Update to Additional Registered Clauses in SMTP Received Headers 9 draft-levine-additional-registered-clauses-02 11 Abstract 13 SMTP servers add Received: trace headers to mail messages to track 14 their progress This document updates the registration criteria for 15 Additional Registered Clauses in those headers to Expert Review, and 16 adds a new clause for Server Name Indication (SNI). 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on July 30, 2019. 35 Copyright Notice 37 Copyright (c) 2019 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. The Server Name Indication clause . . . . . . . . . . . . . . 2 54 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 55 3.1. Guidance for Designated Expert . . . . . . . . . . . . . 3 56 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 57 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 5.1. Normative References . . . . . . . . . . . . . . . . . . 3 59 5.2. Uninformative References . . . . . . . . . . . . . . . . 4 60 Appendix A. Change history . . . . . . . . . . . . . . . . . . . 4 61 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 63 1. Introduction 65 SMTP servers add Received: trace headers to mail messages to track 66 their progress. The syntax of those headers is defined in [RFC5321]. 67 Each header can include optional Additional Registered Clauses that 68 log information related to optional SMTP features. 70 This document updates the registration criteria for Additional 71 Registered Clauses in those headers to Expert Review, and adds a new 72 clause for Server Name Indication (SNI). The headers can include 73 Additional Registered Clauses that add information about optional 74 SMTP features. 76 2. The Server Name Indication clause 78 Server Name Indication or SNI [RFC6066] is an optional TLS feature 79 that a TLS client can use to advise a server the name it expects the 80 server to have. When used in the initial negotiation for a STARTTLS 81 [RFC3207] session it enables the server to use a certificate with the 82 identity that the client expects, as is recommended in [RFC7817] and 83 is required for SMTP MTA-STS [RFC8461]. When a client presents a 84 name using SNI, the server can log the name using the "sni" 85 additional-registered-clause. 87 IANA is requested to add one new entry to the additional-registered- 88 clauses registry: 90 "sni" - indicates the Server Name Indication was used. 92 "name" - the name provided by SNI. It has the syntax of a Domain 93 Name. 95 3. IANA Considerations 97 IANA is requested to update the Registration Procedure for the 98 Additional-registered-clauses registry to Expert Review. The IESG 99 will appoint the expert(s). 101 3.1. Guidance for Designated Expert 103 The Designated Expert is expected to check that a proposed 104 Additional-registered-clause has a specification that is stable and 105 detailed enough to implement the clause and interoperate. The Expert 106 should ensure that the clause name is reasonably related to the 107 information it represents, that the contents of the clause are well- 108 defined, and that any external references it depends on, e.g., a 109 vocabulary of keywords, are stable and well-defined. 111 4. Security Considerations 113 E-mail is subject to a vast range of threats and abuses. In a few 114 circumstances, a new Additional-registered-clause might disclose 115 information to a recipient that was otherwise unavailable. On the 116 other hand, better logging usually makes it easier to diagnose 117 failures and attacks. 119 If the SNI information in a STARTTLS negotiation is logged, it may 120 make it easier to determine the recipient(s) of the message if they 121 are not already logged in trace headers. 123 5. References 125 5.1. Normative References 127 [RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over 128 Transport Layer Security", RFC 3207, DOI 10.17487/RFC3207, 129 February 2002, . 131 [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, 132 DOI 10.17487/RFC5321, October 2008, 133 . 135 [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) 136 Extensions: Extension Definitions", RFC 6066, 137 DOI 10.17487/RFC6066, January 2011, 138 . 140 5.2. Uninformative References 142 [RFC7817] Melnikov, A., "Updated Transport Layer Security (TLS) 143 Server Identity Check Procedure for Email-Related 144 Protocols", RFC 7817, DOI 10.17487/RFC7817, March 2016, 145 . 147 [RFC8461] Margolis, D., Risher, M., Ramakrishnan, B., Brotman, A., 148 and J. Jones, "SMTP MTA Strict Transport Security (MTA- 149 STS)", RFC 8461, DOI 10.17487/RFC8461, September 2018, 150 . 152 Appendix A. Change history 154 02 to 02 Take out ESNI clause to prevent downref. 156 00 to 01 Add new ESNI clause. Fix many typos. 158 00 New draft 160 Author's Address 162 John Levine 163 Taughannock Networks 164 PO Box 727 165 Trumansburg, NY 14886 167 Phone: +1 831 480 2300 168 Email: standards@taugh.com 169 URI: http://jl.ly