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Versions: (draft-kosters-dnsext-dnssec-opt-in) 00 01 02 03 04 05 06 07 08 09 RFC 4956

Network Working Group                                         M. Kosters
Internet-Draft                                   Network Solutions, Inc.
Expires: December 25, 2001                                 June 26, 2001


                     DNSSEC Opt-in for Large Zones
                 draft-ietf-dnsext-dnssec-opt-in-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 25, 2001.

Copyright Notice

   Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract

   In order for DNSSEC to be deployed operationally with large zones
   and little operational impact, there needs to be included a
   mechanism that allows for the separation of secure versus unsecure
   views of zones. This needs to be done in a transparent fashion that
   allows DNSSEC to be deployed in an incremental manner.  This
   document proposes a method using views to allow for incremental
   growth of delegations that are registered as secure. This is
   accomplished by extending the use of the NXT record to deal with
   non-secure delegations as well as for non-existence.






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Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2. Rationale  . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3. Protocol Additions . . . . . . . . . . . . . . . . . . . . . . . 4
   4. Security Considerations  . . . . . . . . . . . . . . . . . . . . 7
   5. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . . 7
   6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7
      References . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
      Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
      Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 9








































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1. Introduction

   DNS is an unsecure system. The key features that give DNS its power
   can also be its chief weaknesses. One feature is the facility to
   delegate branches of information from one set of servers to another.
   Currently, this is done in a non-cryptographically verified way that
   allows spoofing attacks. For example, in July 1997, an alternative
   domain registry called AlterNIC exploited this vulnerability to
   redirect the www.netsol.com and www.internic.net websites to the
   AtlerNIC website. If this delegated information had been
   cryptographically verified, this attack would not have been able to
   occur.

   In recent years, there has been much work within the IETF regarding
   DNS security. There are a number of RFCs that integrate public key
   technology within DNS to enable cryptographically-verified answers.
   To this end, three new resource record types (RR's) have been
   defined:

   o  KEY - one of the public keys of the zone
   o  SIG - a signature of an accompanying RR set
   o  NXT - a record that indicates the range of labels to show
      negative proof

   A zone's authoritative RR's are combined into groups for signing. A
   set of RR's will be in the same group if and only if they have the
   same name and the same RR type. Each group is then signed with each
   of the zone's keys, and each of these signings produces one SIG
   record.  Each zone KEY RR can be verified hierarchically with a SIG
   RR from the direct parent zone. For unsecure delegations, a NULL KEY
   RR is inserted in the parent zone to verifiably attest the subdomain
   is insecure. Finally, NXT RR's and their accompanying SIG RR's are
   issued in the case of a negative reply.

   As a zone maintainer, transitioning to a secure zone has a high
   overhead in the following areas:

   KEY RR
      At a delegation point, the zone maintainer needs to place a NULL
      KEY and accompanying SIG RR's when the child zone is not known to
      be secure.
   NXT RR
      Each delegation needs to be lexigraphically ordered so that a NXT
      RR can be generated and signed with SIG RR's. For large zone
      operators, ordering the zone file is a very time-consuming
      process. In the resolution process, NXT lookups require that the
      server replace efficient hash structures with a lexigraphically
      ordered search structure that degrades lookup performance. This
      lookup performance is a critical element for a high-query rate


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      DNS server.

   Thus, the net effect is when one initially secures a zone as defined
   in RFC2535[4], the amount of processing is massive because of the
   following factors:

   1.  Zone ordering and maintenance for large zones is difficult and
       expensive.
   2.  Adding NULL KEY RR's, NXT RR's and their accompanying SIG RR's
       for unsecure delegations will consume large amounts of memory
       (six times the current memory requirements).
   3.  Having a less efficient lookup algorithm to provide answers to
       queries will degrade overall performance.
   4.  There is very little initial payoff (anticipate only a small
       fraction of delegations to be signed. This equates to less than
       1% over the first six months).
   5.  Unsecured delegations are more expensive at the parent than
       secure delegations (NULL KEY).

2. Rationale

   As DNSSEC is initially deployed, it is anticipated that DNSSEC
   adoption will be slow to materialize. It is also anticipated that
   DNSSEC security resolution will be top-down. Thus for DNSSEC to be
   widely adopted, the root zone and GTLD zones will need to be signed.
   Based on the implications previously listed, a large zone maintainer
   such as the administrator of COM, needs to create an infrastructure
   that is an order of magnitude larger than its current state with
   very little initial benefit.

   This document proposes an alternative opt-in approach that minimizes
   the expense and complexity of DNSSEC adoption by large zones. This
   is done by allowing for an alternate view with only secured
   delegations.

3. Protocol Additions

   The opt-in proposal allows for a zone operator to maintain two views
   of its delegations - one being signed and the other not. The
   non-DNSSEC view will have all delegations - both secured and
   non-secured. The DNSSEC aware view will only have secured
   delegations. It is assumed that neither view will have any innate
   knowledge of the other's delegations. Thus, the cost of securing a
   zone is proportional to the demand of its delegations with the added
   benefit of no longer having to maintain NULL KEY RRs for unsecure
   delegations.

   Since the opt-in model changes the semantics of the NXT RR, the
   resolver needs to know if the zone itself follows a RFC2535[4] style


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   model or the opt-in model. An opt-in zone is identified by setting
   bit 4 of the flags section within the KEY RR for that particular
   zone.

   To determine which view each DNS query packet is to be queried
   against, there is a simple algorithm to be followed:

   1.  The DNSSEC view MUST be queried when the DO bit is set within
       the EDNS0 OPT meta RR as indicated in [6] Additionally,
   2.  The DNSSEC view MUST be queried when the query type is SIG, KEY,
       or NXT.

   If the query does not follow either case (1) or (2), the non-DNSSEC
   view MUST be consulted by default.

   Since the DNSSEC view will have a subset of the actual delegations
   of that zone, it will not be able to respond to an unsecured
   delegation query. To that end, one of the two following events will
   occur:

   1) If the RR set exists within the unsecure view, the answer will
   show up normally with in the Answer and Additional sections.
   Additionally, the NXT RR from the secure view is folded into the
   Authority section along with the related KEY RR's and its SIG in the
   Additional section. The NXT RR is added to prove the answer does not
   exist in the secure view.

   2) If the RR set does not exist within the unsecure view, the RCODE
   will be set to NXDOMAIN. Additionally, the NXT RR from the secure
   view is sent in the Authority section along with the related KEY
   RR's and its SIG in the Additional section.  Again, the NXT RR is
   added to prove the answer does not exist in the secure view.

   Example:

   Consider a zone with the secure names 3, 6, and 9, and unsecure
   names 2, 4, 5, 7, and 8.

   Unsecured zone Contents:

     @ SOA
     2 NS
     3 NS
     4 NS
     5 NS
     6 NS
     7 NS
     8 NS
     9 NS


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   Secured zone Contents:
     @ SOA, SIG SOA, NXT(3), SIG NXT
     3 NS, SIG NS, NXT(6), SIG NXT
     6 NS, SIG NS, NXT(9), SIG NXT
     9 NS, SIG NS, NXT(@), SIG NXT

   1.  A query for 5 RR type A with EDNS0 DO bit set would return with
       the following response:


     RCODE=NOERROR
     Authority Section:
       5 NS
       3 NXT(6), SIG NXT
     Additional Section:
       KEY, SIG KEY


       The secure server would see that 5 is lexographically between 3
       and 6 and therefore know that 5 is insecure.

   2.  A query for 55 RR type A with EDNS0 DO bit set would return with
       the following response:


     RCODE=NXDOMAIN
     Authority Section:
       SOA, SIG SOA, 3 NXT(6), SIG NXT
     Additional Section:
       KEY, SIG KEY


       The secure server would see that 55 is lexographically between
       3 and 6 and therefore know that 55 is definitely does not exist
       in the secure realm.

   3.  A query for 3 RR type KEY without EDNS DO bit set would return
       with an response as defined in RFC2535[4].

   4.  A Query for 3 RR type A, with EDNS0 DO bit set would return with
       a response as defined in RFC2535[4].

   5.  A Query for 6 RR type A, without EDNS0 DO bit set would return
       with a response as defined in RFC1035[2].







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4. Security Considerations

   This draft is different and separate from RFC2535[4] in that it
   allows for secured delegation paths to exist but does not allow for
   secure answers to unsecured delegations at the parent level.
   Increased exposure will be marginal given that the children are
   unsecure.

5. IANA Considerations

   The IANA is requested to reserve the use of the fourth bit of the
   KEY RR to indicate that the zone is an opt-in zone.

6. Acknowledgements

   This document is based on a rough draft by Brian Wellington along
   with input from Olafur Gudmundsson, David Blacka, and Mike
   Schiraldi.

References

   [1]  Mockapetris, P.V., "Domain names - concepts and facilities",
        RFC 1034, STD 13, Nov 1987.

   [2]  Mockapetris, P.V., "Domain names - implementation and
        specification", RFC 1035, STD 13, Nov 1987.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", RFC 2119, BCP 14, March 1997.

   [4]  Eastlake, D., "Domain Name System Security Extensions", RFC
        2535, March 1999.

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

   [6]  Conrad, D. R., "Indicating Resolver Support of DNSSEC (work in
        progress)", August 2000.













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Author's Address

   Mark Kosters
   Network Solutions, Inc.
   505 Huntmar Park Drive
   Herndon, VA  22070
   US

   Phone: +1 703 948-3362
   EMail: markk@netsol.com
   URI:   http://www.netsol.com








































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Full Copyright Statement

   Copyright (C) The Internet Society (2001). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
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   kind, provided that the above copyright notice and this paragraph
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   The limited permissions granted above are perpetual and will not be
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   This document and the information contained herein is provided on an
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Acknowledgement

   Funding for the RFC editor function is currently provided by the
   Internet Society.



















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