Internet DRAFT - draft-peterson-dot-dhcp
draft-peterson-dot-dhcp
Network Working Group T. Peterson
Internet-Draft July 22, 2019
Intended status: Standards Track
Expires: January 23, 2020
DNS over Transport Layer Security announcements using DHCP or Router
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draft-peterson-dot-dhcp-01
Abstract
This specification describes a DHCP option and Router Advertisement
(RA) extension to inform clients of the presence of DNS resolvers
with Transport Layer Security (TLS).
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 January 23, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2
3. The DNS over TLS Option . . . . . . . . . . . . . . . . . . . 2
3.1. IPv4 DHCP Option . . . . . . . . . . . . . . . . . . . . 3
3.2. IPv6 DHCP Option . . . . . . . . . . . . . . . . . . . . 3
3.3. The DoT IPv6 RA Option . . . . . . . . . . . . . . . . . 3
3.4. Trust Anchoring . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
DHCPv4 [RFC2131], DHCPv6 [RFC3646], and IPv6 Router Announcements
[RFC8106] all provide means to inform clients of available resolvers
using the incumbent DNS protocol for querying, however there is no
means of specifying alternate protocols to perform DNS queries.
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.
"DoT", "Do53" and other related abbreviations follow the definitions
as defined in [I-D.draft-hoffman-dns-terminology-ter-01].
3. The DNS over TLS Option
The DoT DHCP/RA option informs the client that a DoT service is
available for use for answering DNS queries using the same IP
address(es) returned in Do53 DNS Server DHCP/RA options. Thus
networks which announce DoT services MUST announce DNS resolver
availability via their respective options, and provide a TLS
certificate on the DoT service which passes verification ([RFC6125])
against the DNS Host Name provided in the DoT DHCP/RA option.
The maximum length of the DNS Host Name that can be carried in IPv4
DHCP is 255 bytes, so DNS Host Names longer than 255 bytes SHOULD NOT
be used in IPv6 DHCP or IPv6 RA.
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3.1. IPv4 DHCP Option
The format of the IPv4 DoT DHCP option is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| DNS Host Name |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: The DoT DHCPv4 option (one octet)
Len: Length of the DNS Host Name
DNS Host Name: The DNS Host Name
3.2. IPv6 DHCP Option
The format of the IPv6 Captive-Portal DHCP option is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| DNS Host Name |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: TODO (two octets)
option-len: Length of the DNS Host Name, in octects
DNS Servers: The DNS Host Name
3.3. The DoT IPv6 RA Option
The format of the DoT Router Advertisement option is shown below.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| DNS Host Name |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TODO (one octet)
Len: The length of the DNS Host Name, in octets
DNS Server: The DNS Host Name
3.4. Trust Anchoring
TODO: Put in considerations for using DANE and/or existing
certificate authorities for trust anchoring.
4. Security Considerations
An attacker with the ability to inject DHCP messages could include
this option and present a malicious resolver.
TODO: Further risk and threat assessments.
5. IANA Considerations
TODO: This section must be updated after assignments have been
issued.
This document requires the assignment of an option code assigned
under the "BOOTP Vendor Extensions and DHCP Options"
[bootp-registry], in addition to an option code assigned under the
"Option Codes" registry under DHCPv6 parameters [dhcpv6-registry].
Also, an assignment for an IPv6 RA Option Type from the "IPv6
Neighbor Discovery Option Formats" registry under ICMPv6 paramters
[icmpv6-registry].
6. References
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6.1. Normative References
[I-D.draft-hoffman-dns-terminology-ter-01]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-hoffman-dns-terminology-ter-01 (work in
progress), April 2019.
[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>.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
<https://www.rfc-editor.org/info/rfc2132>.
[RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
DOI 10.17487/RFC3646, December 2003,
<https://www.rfc-editor.org/info/rfc3646>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 8106, DOI 10.17487/RFC8106, March 2017,
<https://www.rfc-editor.org/info/rfc8106>.
[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>.
6.2. Informative References
[bootp-registry]
"Dynamic Host Configuration Protocol (DHCP) and Bootstrap
Protocol (BOOTP) Parameters", n.d.,
<http://www.iana.org/assignments/bootp-dhcp-parameters>.
[dhcpv6-registry]
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
n.d., <http://www.iana.org/assignments/dhcpv6-parameters>.
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[icmpv6-registry]
"Internet Control Message Protocol version 6 (ICMPv6)
Parameters", n.d.,
<http://www.iana.org/assignments/icmpv6-parameters>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>.
Acknowledgments
The author would like to acknowledge the extensive feedback from
Martin Thomson.
Author's Address
Thomas Peterson
Email: nosretep.samoht@gmail.com
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