Network Working Group                                         B. Dickson
Internet-Draft                                                   GoDaddy
Intended status: Standards Track                         24 October 2021
Expires: 27 April 2022


  Resource Record for Signaling Transport for DNS to Authority Servers
                      draft-dickson-dprive-dnst-00

Abstract

   This Internet Draft proposes an RRTYPE to signal explicit support for
   transport types for DNS service.  This new RRTYPE is "DNST".  The
   available transports to signal are TCP and UDP on port 53 (DNS), and
   DoT (DNS over TLS) transport using TCP port 853.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 27 April 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Remove Before Publication . . . . . . . . . . . . . . . . . .   2
   5.  DNS Transport RRTYPE  . . . . . . . . . . . . . . . . . . . .   3
   6.  Restrictions  . . . . . . . . . . . . . . . . . . . . . . . .   3
   7.  Wire Format . . . . . . . . . . . . . . . . . . . . . . . . .   3
   8.  Presentation Format . . . . . . . . . . . . . . . . . . . . .   3
   9.  Additional Processing . . . . . . . . . . . . . . . . . . . .   4
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   4
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   12. Normative References  . . . . . . . . . . . . . . . . . . . .   4
   13. Informative References  . . . . . . . . . . . . . . . . . . .   4
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Background

   DNS over TLS is defined in [RFC7858].  However, there is no explicit
   signaling for when DoT should be used.  Without explicit signaling,
   there is no protection against downgrade attacks by an on-path
   attacker.

4.  Remove Before Publication

   Notes on design decisions, including the decision NOT to use an SVCB-
   compatible format:

   *  NS records MUST point to non-CNAME records.  Thus, there is no
      need for the SVCB "Alias-form" behavior.  DNST does not support
      aliasing,

   *  DNST allows for explicit rejection of default transport (UDP/53
      and TCP/53)

   *  DNST allows explicit signaling of DoT



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   *  There is no need for alternate port numbers for UDP or TCP port
      53, or for DoT port 853.

   *  There is no need for DoH, since the expected clients are limited
      to DNS resolvers.

5.  DNS Transport RRTYPE

   The solution to this problem is to introduce a method for explicit
   signaling for when DoT is available.  When combined with TLSA
   [RFC6698] records for the corresponding DNS server name, any client
   wishing to use DoT is able to know that it is available, and can
   detect and avoid any attempts at transport downgrade.

   This document defines the RRTYPE value {TBD} with mnemonic name DNST
   ("DNS Transport").  This consists of a set of flags indicating
   supported transport for the DNS server at the owner name.  The flag
   bits represent transports:

   *  UDP on port 53

   *  TCP on port 53

   *  DoT (DNS over TLS) on port 853

6.  Restrictions

   The DNST record may occur anywhere, including at the apex of a DNS
   zone, and may co-exist with any other type that also permits other
   types.

7.  Wire Format

   The RDATA wire format is an 8-bit octet of flag bits.

   | UDP | TCP | DOT | 5 unused bits |

8.  Presentation Format

   OWNER CLASS TTL DNST [UDP] [TCP] [DOT]

   At least one of the transport types must be present.









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9.  Additional Processing

   The authoritative server MAY/SHOULD return both the DNST record(s)
   and any/all A and AAAA records with the same owner name.  This
   reduces the number of queries the resolver would otherwise have to
   make (i.e. two additional queries for A and AAAA record types).

10.  Security Considerations

   The DNST record MUST be in a DNSSEC-signed zone.  This ensures
   protection against downgrade attacks on the transport signaling.

11.  IANA Considerations

   IANA is directed to add a new record to the DNS RRTYPES table to add
   the entry "DNST" with value "TBD", referencing this document.

12.  Normative References

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <https://www.rfc-editor.org/info/rfc6698>.

   [RFC7858]  Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
              and P. Hoffman, "Specification for DNS over Transport
              Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
              2016, <https://www.rfc-editor.org/info/rfc7858>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

13.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

Appendix A.  Acknowledgments

   Thanks to everyone who helped create the tools that let everyone use
   Markdown to create Internet Drafts, and the RFC Editor for xml2rfc.

   Thanks to Dan York for his Tutorial on using Markdown (specificially
   mmark) for writing IETF drafts.




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   Thanks to YOUR NAME HERE for contributions, reviews, etc.

Author's Address

   Brian Dickson
   GoDaddy

   Email: brian.peter.dickson@gmail.com











































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