Internet Engineering Task Force L. Song
Internet-Draft Beijing Internet Institute
Intended status: Experimental P. Vixie
Expires: September 22, 2018 TISF
S. Kerr
March 21, 2018
An Proxy Use Case of DNS over HTTPS
draft-ietf-dnsop-dns-wireformat-http-02
Abstract
This memo introduces a DNS proxy use case to tunnel DNS query and
response over HTTPs using DOH, a newly proposed DNS transport. This
is useful in some situation where DNS is not working properly and DOH
is not widely available for many stub-resolvers.
Status of This Memo
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This Internet-Draft will expire on September 22, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use case description . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3
4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. Registration of application/dns-tcpwireformat Media Type 4
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
RFC 1035 [RFC1035] specifies the wire format for DNS messages. It
also specifies DNS transport on UDP and TCP on port 53, which is
still used today. To enhance the availability of honest DNS, a new
DNS transport DOH is proposed which transport DNS over HTTPs
[I-D.ietf-doh-dns-over-https], in a way to cure DNS's long-time
suffering from on-path attack by spoofing and blocking.
This memo introduces a DNS proxy use case to leverage the DOH
protocol as a substrate to tunnel DNS data over HTTPs which is called
called DOH proxy in the rest of the document. It is useful
especially when most DNS stub-resolvers and servers are not aware the
new DOH protocol, but a public or private proxy using DOH can be
deployed and offer DOH capacity to users to bypass the networks where
DNS is not working properly.
Just as a normal DNS proxy described in [RFC5625], DOH proxy works as
a simple DNS forwarder keeping the transparency principle, so any
"hop-by-hop" mechanisms or newly introduced protocol extensions
operate as if the proxy were not there. The only difference is DOH
proxy consist two part, a proxy client as a initiator of DOH tunnel
and a proxy server as a terminator.
In order to keep the transparency of DOH proxy, a new media type is
required in DOH proxy use case to allow the proxy client and proxy
server use the same transport (UDP or TCP) connecting sub-resolver
and far-end server.
May REMOVE BEFORE PUBLICATION: Comparing using a general VPN, the DOH
proxy can work on an actual HTTP server, so it can be hosted on a
machine that also serves web pages. This means that DNS over HTTP is
slightly more "stealthy" than a VPN, in that it can be
indistinguishable from normal web traffic.
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2. Use case description
As mentioned in introduction, DOH proxy is a special use case to
provide to end users with better DNS availability by leveraging the
DOH protocol. The proxy client and proxy server speak DOH which
served as a tunnel for DNS query and response.
The typical scenario is that a DOH proxy sitting between stub-
resolver and the recursive server. The stub-resolver is configured
sending DNS query to a proxy client and expected reply from the same
proxy client. If proxy client receives the query via UDP, then it
will carry the media type "application/dns-udpwireformat" in the HTTP
request and includes the DNS query as the message body as defined in
DOH protocol. If proxy client receives the query via TCP, then it
will carry a new media type defined in this document "application/
dns-tcpwireformat" and speak DOH with proxy server with the same DNS
query without the two-byte length field defined in DNS over TCP
[section 4.2.2 in [RFC1035]].
The proxy server MUST be able to process both "application/dns-
udpwireformat" and "application/dns-tcpwireformat" request messages
and forward the query to a configured recursive server using the same
transport between sub-resolver and proxy client. The response will
be delivered back to sub-resolver accordingly. In DOH proxy use
case, each DNS query-response pair is mapped into a DOH query-
response pair. And the transport for DNS query and response MUST be
the same.
It is possible that a proxy client as a module can be deployed in the
same host with the sub-client listening to a loop-back address. A
proxy server can be implemented that way to host a recursive DNS
process as well. The can be combined to form four deployment
scenarios of DOH proxy use case.
It is also possible to use the proxy server as a regular web server
at the same time that is acting as a proxy server.
Note that the proxy client will face the same bootstrapping problem
described in DOH when the HTTPs request needs to resolve the name of
server and send the request to on IP address. The strategy is either
use the IP directly or use another resolver (like the normal DHCP-
supplied resolver) to lookup the IP of the server.
3. Security Considerations
The DOH proxy use case does not introduce new protocol and any new
security considerations since it is built on the DNS over HTTPS
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protocols. All security considerations and recommendations apply in
DOH proxy use case.
Since DOH proxy is a also a special DNS proxy, the security
recommendations of DNS proxy RFC 5625 [RFC5625] also apply in DOH
proxy use case.
Note that the ability to perform DNS queries in this way may allow
users to bypass local DNS policy. This may be problematic in any
environment where administrators need to enforce specific DNS
behavior, such as an enterprise environment. The protocol outlined
here does not introduce any new capabilities in this area, but by
creating a more standardized way of doing this it may cause
operational problems for enterprise administrators.
4. IANA considerations
4.1. Registration of application/dns-tcpwireformat Media Type
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To: ietf-types@iana.org
Subject: Registration of MIME media type
application/dns-tcpwireformat
MIME media type name: application
MIME subtype name: dns-tcpwireformat
Required parameters: n/a
Optional parameters: n/a
Encoding considerations: This is a binary format. The contents are a
DNS message as defined in RFC 1035. The format used here is for DNS
over UDP, which is the format defined in the diagrams in RFC 1035.
Security considerations: The security considerations for carrying
this data are the same for carrying DNS without encryption.
Interoperability considerations: None.
Published specification: This document.
Applications that use this media type:
Systems that want to ship DNS messages via HTTP.
Additional information:
Magic number(s): n/a
File extension(s): n/a
Macintosh file type code(s): n/a
Person & email address to contact for further information:
Linjian Song, songlinjian@gmail.com
Intended usage: COMMON
Restrictions on usage: n/a
Author: Linjian Song, songlinjian@gmail.com
Change controller: IESG
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5. Acknowledgments
Thanks to Bob Harold, Paul Hoffman, Julian Reschke, and Erik Kline
for review.
6. References
[I-D.ietf-doh-dns-over-https]
Hoffman, P. and P. McManus, "DNS Queries over HTTPS",
draft-ietf-doh-dns-over-https-03 (work in progress),
February 2018.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines",
BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
<https://www.rfc-editor.org/info/rfc5625>.
Authors' Addresses
Linjian Song
Beijing Internet Institute
2nd Floor, Building 5, No.58 Jing Hai Wu Lu, BDA
Beijing 100176
P. R. China
Email: songlinjian@gmail.com
URI: http://www.biigroup.com/
Paul Vixie
TISF
11400 La Honda Road
Woodside, California 94062
US
Email: vixie@tisf.net
URI: http://www.redbarn.org/
Shane Kerr
Antoon Coolenlaan 41
Uithoorn 1422 GN
NL
Email: shane@time-travellers.org
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