DNS over HTTP resolver announcement Using DHCP or Router Advertisements
draft-peterson-doh-dhcp-00
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| Author | Thomast Peterson | ||
| Last updated | 2019-04-25 | ||
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draft-peterson-doh-dhcp-00
Network Working Group T. Peterson
Internet-Draft April 25, 2019
Intended status: Standards Track
Expires: October 27, 2019
DNS over HTTP resolver announcement Using DHCP or Router Advertisements
draft-peterson-doh-dhcp-00
Abstract
This specification describes a DHCP option and Router Advertisement
(RA) extension to inform clients of the presents of a DNS over HTTP
(DoH) service to be used for DNS queries.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 27, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2
3. The DoH Option . . . . . . . . . . . . . . . . . . . . . . . 2
3.1. IPv4 DHCP Option . . . . . . . . . . . . . . . . . . . . 3
3.2. IPv6 DHCP Option . . . . . . . . . . . . . . . . . . . . 3
3.3. The DoH IPv6 RA Option . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
DHCPv4 [RFC3132], 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.
3. The DoH Option
The DoH DHCP/RA option informs the client that a DoH service is
available for use for answering DNS queries. In order to support
multiple "classes" of clients, the network operator can provide the
URI template [RFC6570] which describes how a client can construct the
URL to use for resolution. Whilst DoH servers may support multiple
URI Templates, only one template MUST be transmitted.
URI Templates that contain a host name SHOULD only be sent where a
DHCP server or Router provide name servers, as name resolution of any
host name in the template will require clients to use the non-DoH
servers provided or manual configuration.
The maximum length of the URI template that can be carried in IPv4
DHCP is 255 bytes, so URI templates 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 DoH 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 | Length | URI Template .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Code: The DoH DHCPv4 option (one octet).
o Length: The length, in octets of the URI template.
o URI Template: The DoH server available, encoded following the
rules of [RFC3986].
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. URI Template .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o option-code: TODO (two octets)
o option-len: The length, in octects of the URI Template.
o URI Template: The DoH server
3.3. The DoH IPv6 RA Option
The format of the DoH 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 | Length | URI Template .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: TODO (one octet)
o Length: 8-bit unsigned integer representing the entire length of
all fields, in units of 8 bytes.
o URI Template: The DoH server available for use. This should be
padded with NULL (0x0) to make the total option length (including
the Type and Length fields) a multiple of 8 bytes.
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
6.1. Normative 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>.
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[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012,
<https://www.rfc-editor.org/info/rfc6570>.
[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>.
[icmpv6-registry]
"Internet Control Message Protocol version 6 (ICMPv6)
Parameters", n.d.,
<http://www.iana.org/assignments/icmpv6-parameters>.
[RFC3132] Kempf, J., "Dormant Mode Host Alerting ("IP Paging")
Problem Statement", RFC 3132, DOI 10.17487/RFC3132, June
2001, <https://www.rfc-editor.org/info/rfc3132>.
[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>.
[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>.
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Acknowledgments
TODO
Author's Address
Thomas Peterson
Email: nosretep.samoht@gmail.com
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