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An Proxy Use Case of DNS over HTTPS

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Document Type This is an older version of an Internet-Draft whose latest revision is Expired
Authors Linjian Song , Paul A. Vixie , Shane Kerr
Last updated 2018-03-21
Replaces draft-song-dns-wireformat-http
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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


   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

   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
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 22, 2018.

Copyright Notice

   Copyright (c) 2018 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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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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    Subject: Registration of MIME media type

    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,

    Intended usage:  COMMON

    Restrictions on usage:  n/a

    Author:  Linjian Song,

    Change controller:  IESG

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5.  Acknowledgments

   Thanks to Bob Harold, Paul Hoffman, Julian Reschke, and Erik Kline
   for review.

6.  References

              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, <>.

   [RFC5625]  Bellis, R., "DNS Proxy Implementation Guidelines",
              BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,

Authors' Addresses

   Linjian Song
   Beijing Internet Institute
   2nd Floor, Building 5, No.58 Jing Hai Wu Lu, BDA
   Beijing  100176
   P. R. China


   Paul Vixie
   11400 La Honda Road
   Woodside, California  94062


   Shane Kerr
   Antoon Coolenlaan 41
   Uithoorn  1422 GN


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