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Versions: 00                                                            
Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                                 R. Arends
Expires: August 30, 2012                                         Nominet
                                                       February 27, 2012


                               EDNS Echo.
                      draft-wkumari-dnsext-echo-00

Abstract

   This document describes a DNS protocol extension to allow for
   arbritry data to be inserted into a DNS Request and have that same
   data be returned in a DNS Reply.

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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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 30, 2012.

Copyright Notice

   Copyright (c) 2012 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
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   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . . . 3
   2.  Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  Increasing the size of the ID space . . . . . . . . . . . . 3
   3.  ECHO Option format  . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Presentation format . . . . . . . . . . . . . . . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 4
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Changes / Author Notes.  . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 5



































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1.  Introduction

   RFC2671 [RFC2671] specifies an extension mechanism for DNS.  This
   document describes an EDNS option to allow for arbritry data to be
   inserted into a DNS Request and have that same data be returned in a
   DNS Reply.  This functionality can be used to increase the effective
   size of the ID field [RFC1035, Section 4.1.1 [RFC1035]] and to aid in
   diagnostics.

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  Use cases

2.1.  Increasing the size of the ID space

   The Header section of the DNS Message format contains a 16-bit ID
   field (see [RFC1035, Section 4.1.1 [RFC1035]).  This field is used to
   match replies to their queries.  If an attacker is able to predict
   this field he may be able to spoof a reply and perform a DNS cache
   poisining attack.  By inserting arbritary data into the ECHO OPTION-
   DATA in a query (and checking that the same data is returned in the
   response), an iterative resolver can protect itself against this type
   of attack.  Note that the resolver needs to add additional steps to
   protect against a downgrade attack.  This technique does not protect
   against a man in the middle attack.

   To avoid maintaining additional state for each query, the sender can
   algorithmically generate the ECHO OPTION-DATA.  As an example it
   could generate this data field by calculating a hash over the
   concatenation of various fileds (such as the QNAME and the ID field)
   and a secret.


3.  ECHO Option format

   The OPTION-CODE for the ECHO option is TBD.

   The OPTION-DATA for the ECHO option is an opaque byte string, the
   semantics of which are deliberately left outside the protocol.

   The OPTION-DATA only has meaning to the sender.  The software that
   generates the response or any intermediate device SHOULD NOT try and
   infer anything from the data.



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3.1.  Presentation format

   User interfaces MUST read and write the contents of the ECHO option
   as a sequence of hexadecimal digits, two digits per payload octet.
   The ECHO payload is binary data.  Any comparison between ECHO
   payloads MUST be a comparison of the raw binary data.  Copy
   operations MUST NOT assume that the raw payload is null-terminated.


4.  IANA Considerations

   The IANA is requested to assign a value from the "DNS EDNS0 Options"
   registry, setting the name to be "ECHO" and referencing this
   document.

   The code for the option should be TBD.


5.  Security Considerations

   A common form of denial of service attack is the reflected DNS
   amplification attack.  In this attack an attacker spoofs DNS requests
   from the victim that will result in a much larger reply (the
   amplification factor).  While the attacker could include a large
   amount of data in the ECHO payload of the spoofed DNS requests, this
   doesn't create any amplification.

   The ECHO option could be used for DNS tunneling and exfiltration of
   data.


6.  Acknowledgements

   The authors wish to thank some folk.


7.  References

7.1.  Normative References

   [IANA.AS_Numbers]
              IANA, "Autonomous System (AS) Numbers",
              <http://www.iana.org/assignments/as-numbers>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate



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              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2671]  Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
              RFC 2671, August 1999.

7.2.  Informative References

   [I-D.ietf-sidr-iana-objects]
              Manderson, T., Vegoda, L., and S. Kent, "RPKI Objects
              issued by IANA", draft-ietf-sidr-iana-objects-03 (work in
              progress), May 2011.


Appendix A.  Changes / Author Notes.

   [RFC Editor: Please remove this section before publication ]

   Changes from $undefined to -00.

   o  Initial document generation.

   Notes / references:

   o  rfc2671.txt - Extension Mechanisms for DNS (EDNS0)
   o  rfc5001.txt - DNS Name Server Identifier (NSID) Option


Authors' Addresses

   Warren Kumari
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   US

   Email: warren@kumari.net


   Roy Arends
   Nominet
   Minerva House, Edmund Halley Road
   Oxford  OX4 6LB
   UK

   Email: roy@nominet.org.uk






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