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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'UDP' is mentioned on line 135, but not defined == Missing Reference: 'TCP' is mentioned on line 135, but not defined == Missing Reference: 'DOT' is mentioned on line 135, but not defined Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group B. Dickson 3 Internet-Draft GoDaddy 4 Intended status: Standards Track 24 October 2021 5 Expires: 27 April 2022 7 Resource Record for Signaling Transport for DNS to Authority Servers 8 draft-dickson-dprive-dnst-00 10 Abstract 12 This Internet Draft proposes an RRTYPE to signal explicit support for 13 transport types for DNS service. This new RRTYPE is "DNST". The 14 available transports to signal are TCP and UDP on port 53 (DNS), and 15 DoT (DNS over TLS) transport using TCP port 853. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on 27 April 2022. 34 Copyright Notice 36 Copyright (c) 2021 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 41 license-info) in effect on the date of publication of this document. 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. Code Components 44 extracted from this document must include Simplified BSD License text 45 as described in Section 4.e of the Trust Legal Provisions and are 46 provided without warranty as described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2 52 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 53 4. Remove Before Publication . . . . . . . . . . . . . . . . . . 2 54 5. DNS Transport RRTYPE . . . . . . . . . . . . . . . . . . . . 3 55 6. Restrictions . . . . . . . . . . . . . . . . . . . . . . . . 3 56 7. Wire Format . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 8. Presentation Format . . . . . . . . . . . . . . . . . . . . . 3 58 9. Additional Processing . . . . . . . . . . . . . . . . . . . . 4 59 10. Security Considerations . . . . . . . . . . . . . . . . . . . 4 60 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 61 12. Normative References . . . . . . . . . . . . . . . . . . . . 4 62 13. Informative References . . . . . . . . . . . . . . . . . . . 4 63 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 4 64 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 66 1. Introduction 68 2. Conventions and Definitions 70 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 71 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 72 "OPTIONAL" in this document are to be interpreted as described in BCP 73 14 [RFC2119] [RFC8174] when, and only when, they appear in all 74 capitals, as shown here. 76 3. Background 78 DNS over TLS is defined in [RFC7858]. However, there is no explicit 79 signaling for when DoT should be used. Without explicit signaling, 80 there is no protection against downgrade attacks by an on-path 81 attacker. 83 4. Remove Before Publication 85 Notes on design decisions, including the decision NOT to use an SVCB- 86 compatible format: 88 * NS records MUST point to non-CNAME records. Thus, there is no 89 need for the SVCB "Alias-form" behavior. DNST does not support 90 aliasing, 92 * DNST allows for explicit rejection of default transport (UDP/53 93 and TCP/53) 95 * DNST allows explicit signaling of DoT 96 * There is no need for alternate port numbers for UDP or TCP port 97 53, or for DoT port 853. 99 * There is no need for DoH, since the expected clients are limited 100 to DNS resolvers. 102 5. DNS Transport RRTYPE 104 The solution to this problem is to introduce a method for explicit 105 signaling for when DoT is available. When combined with TLSA 106 [RFC6698] records for the corresponding DNS server name, any client 107 wishing to use DoT is able to know that it is available, and can 108 detect and avoid any attempts at transport downgrade. 110 This document defines the RRTYPE value {TBD} with mnemonic name DNST 111 ("DNS Transport"). This consists of a set of flags indicating 112 supported transport for the DNS server at the owner name. The flag 113 bits represent transports: 115 * UDP on port 53 117 * TCP on port 53 119 * DoT (DNS over TLS) on port 853 121 6. Restrictions 123 The DNST record may occur anywhere, including at the apex of a DNS 124 zone, and may co-exist with any other type that also permits other 125 types. 127 7. Wire Format 129 The RDATA wire format is an 8-bit octet of flag bits. 131 | UDP | TCP | DOT | 5 unused bits | 133 8. Presentation Format 135 OWNER CLASS TTL DNST [UDP] [TCP] [DOT] 137 At least one of the transport types must be present. 139 9. Additional Processing 141 The authoritative server MAY/SHOULD return both the DNST record(s) 142 and any/all A and AAAA records with the same owner name. This 143 reduces the number of queries the resolver would otherwise have to 144 make (i.e. two additional queries for A and AAAA record types). 146 10. Security Considerations 148 The DNST record MUST be in a DNSSEC-signed zone. This ensures 149 protection against downgrade attacks on the transport signaling. 151 11. IANA Considerations 153 IANA is directed to add a new record to the DNS RRTYPES table to add 154 the entry "DNST" with value "TBD", referencing this document. 156 12. Normative References 158 [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication 159 of Named Entities (DANE) Transport Layer Security (TLS) 160 Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August 161 2012, . 163 [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., 164 and P. Hoffman, "Specification for DNS over Transport 165 Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May 166 2016, . 168 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 169 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 170 May 2017, . 172 13. Informative References 174 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 175 Requirement Levels", BCP 14, RFC 2119, 176 DOI 10.17487/RFC2119, March 1997, 177 . 179 Appendix A. Acknowledgments 181 Thanks to everyone who helped create the tools that let everyone use 182 Markdown to create Internet Drafts, and the RFC Editor for xml2rfc. 184 Thanks to Dan York for his Tutorial on using Markdown (specificially 185 mmark) for writing IETF drafts. 187 Thanks to YOUR NAME HERE for contributions, reviews, etc. 189 Author's Address 191 Brian Dickson 192 GoDaddy 194 Email: brian.peter.dickson@gmail.com