Internet DRAFT - draft-dickson-dprive-dnst
draft-dickson-dprive-dnst
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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 27 April 2022.
Copyright Notice
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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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