Operating a Glueless DNS Authority Server
draft-dickson-dnsop-glueless-01

Network Working Group                                         B. Dickson
Internet-Draft                                                   GoDaddy
Intended status: Informational                         17 September 2021
Expires: 21 March 2022

               Operating a Glueless DNS Authority Server
                    draft-dickson-dnsop-glueless-01

Abstract

   This Internet Draft proposes a method for protecting authority
   servers against MITM and poisoning attacks, using a domain naming
   strategy to not require glue A/AAAA records and use of DNSSEC.

   This technique assumes the use of validating resolvers.

   MITM and poisoning attacks should only be effective/possible against
   unsigned domains.

   However, until all domains are signed, this guidance is relevant, in
   that it can limit the attack surface of unsigned domains.

   This guidance should be combined with [I-D.dickson-dnsop-ds-hack]

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

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 21 March 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Proposed Solutions  . . . . . . . . . . . . . . . . . . . . .   3
   5.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   DNS Security extensions (DNSSEC) are additions to the DNS protocol
   which provide data integrity and authenticity protections, but do not
   provide privacy.

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.  Background

   Use of DNSSEC requires upgrades to software for authorative servers,
   resolvers, and optionally clients, in order to benefit from these
   protections.  It also requires that DNS operators actually sign their
   zones.

   When a given zone is unsigned, those protections to the zone contents
   are not available.

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   Any unsigned zone is trivially able to be altered by an on-path
   attacker.

   An off-path attacker is limited to use of cache poisoning attacks.

   However, some class of cache poisoning attacks target unsigned
   delegation data.  These records consist of the necessary NS records,
   and when necessary, "glue" records for IP address corresponding to
   these NS records.

   The impact to successful cache poisoning of delegation records is
   that the attacker may substitute their own name servers for the
   legitimate name server.  In other words, the attacker is able to
   promote itself to being effectively on-path, and trivially modify
   unsigned domain results.

4.  Proposed Solutions

   There are two delegation record types that require protection against
   off-path attackers, for unsigned domains.

   For protecting NS records used in delegations, there is a new
   proposal for use of a new DS record.  See [I-D.dickson-dnsop-ds-hack]
   for details.

   The present draft addresses the "glue" records, by recommending
   methods to make them unnecessary.  If there is no delegation glue
   data, an attacker cannot poison that data.  The resolver cache would
   contain only authoritative data, which cannot be pre-empted by such
   poisoning attacks.

5.  Recommendations

   The following practice is RECOMMENDED for unsigned zones:

   *  Do not use in-bailiwick name server names for unsigned zones.

   *  Use out-of-zone names for the name servers for unsigned zones

   Example:

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   Do NOT do the following (delegations requiring glue):
   unsigned-zone.example NS ns1.unsigned-zone.example
   unsigned-zone.example NS ns2.unsigned-zone.example
   // glue
   ns1.unsigned-zone.example A (IP address)
   ns1.unsigned-zone.example AAAA (IP address)
   ns2.unsigned-zone.example A (IP address)
   ns2.unsigned-zone.example AAAA (IP address)

   Instead, do the following (glueless delegations):
   unsigned-zone.example NS ns1.nameserver-signed-zone.example
   unsigned-zone.example NS ns2.nameserver-signed-zone.example
   //
   // Delegation to signed zone containing name server names
   nameserver-signed-zone.example NS ns1.nameserver-signed-zone.example
   nameserver-signed-zone.example NS ns2.nameserver-signed-zone.example
   nameserver-signed-zone.example DS (DS record data)
   // glue records for this delegation
   ns1.nameserver-signed-zone.example A (IP address)
   ns1.nameserver-signed-zone.example A (IP address)
   ns2.nameserver-signed-zone.example AAAA (IP address)
   ns2.nameserver-signed-zone.example AAAA (IP address)

   The following practice is RECOMMENDED (for signed name server name
   zones, i.e. large operators' zones):

   *  For name server name zones (zones containing data for name
      servers), use dedicated name server names for the zone itself

   *  Consider use of another zone for the dedicated name server names,
      to make the name server name zone itself fully glueless

   *  For this additional zone, also consider using a different name
      server _name_ for its delegation's exclusive use

   *  Decoupling the respective NS names, ensures changes and updates to
      the zone that uses glue, don't affect any other zones

   *  Depending on parent zone policy (e.g.  TLD database policy),
      renaming or renumbering name servers may affect delegations using
      them (NS entries)

   *  A single zone with non-reused NS names guarantees side effects of
      this sort are not possible

   *  Additional lookups are required on the initial reference to any NS
      in the main glueless zone

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   *  Subsequent (new) queries for the IP addresses of glueless name
      servers only require single queries

   Example:

   Entries in the example TLD
   //
   // Same unsigned zone uses the same name servers
   // However, the name server is in its own glueless zone
   unsigned-zone.example NS ns1.nameserver-signed-zone.example
   unsigned-zone.example NS ns2.nameserver-signed-zone.example
   //
   nameserver-signed-zone.example NS ns1.separate-zone.example
   nameserver-signed-zone.example NS ns2.separate-zone.example
   nameserver-signed-zone.example DS (DS record data)
   //
   separate-zone.example NS special-ns1.separate-zone.example
   separate-zone.example NS special-ns2.separate-zone.example
   separate-zone.example DS (DS record data)
   // glue for special-ns1 and -2
   // special-ns1 and -2 are used only for/by separate-zone
   special-ns1.separate-zone.example A (IP address)
   special-ns1.separate-zone.example AAAA (IP address)
   special-ns2.separate-zone.example A (IP address)
   special-ns2.separate-zone.example AAAA (IP address)

   Zone file for nameserver-signed-zone:
   nameserver-signed-zone.example SOA (soa record data)
   // glueless NS are used
   nameserver-signed-zone.example NS ns1.separate-zone.example
   nameserver-signed-zone.example NS ns2.separate-zone.example
   // actual glueless address records for "real" name server names
   ns1.nameserver-signed-zone.example A (IP address)
   ns1.nameserver-signed-zone.example AAAA (IP address)
   ns2.nameserver-signed-zone.example A (IP address)
   ns2.nameserver-signed-zone.example AAAA (IP address)
   // etc etc etc

   Zone file for separate-zone:
   separate-zone.example SOA (soa record data)
   // This is the only non-glueless NS in use
   // NB: matches glue in parent
   separate-zone.example NS special-ns1.separate-zone.example
   separate-zone.example NS special-ns2.separate-zone.example
   special-ns1.separate-zone.example A (IP address)
   special-ns1.separate-zone.example AAAA (IP address)
   special-ns2.separate-zone.example A (IP address)
   special-ns2.separate-zone.example AAAA (IP address)

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   // actual address records for "real" name server name
   // (only used by nameserver-signed-zone)
   ns1.separate-zone.example A (IP address)
   ns1.separate-zone.example AAAA (IP address)
   ns2.separate-zone.example A (IP address)
   ns2.separate-zone.example AAAA (IP address)

6.  Security Considerations

   This guidance is not a substitute for use of DNSSEC for DNS domains.

   This guidance is useful in preventing off-path attackers from
   poisoning DNS cache entries necessary for delegations.

   However, an on-path attacker is still able to manipulate DNS
   responses sent over UDP or unencrypted TCP.

   Use of an encrypted transport is one potential method of preventing
   MITM attacks (i.e.  DNS over TLS from resolver to authoritative
   server, aka ADoT), but this is still less secure than use of DNSSEC.

7.  IANA Considerations

   This document has no IANA actions.

8.  Normative References

   [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>.

9.  Informative References

   [I-D.dickson-dnsop-ds-hack]
              Dickson, B., "DS Algorithms for Securing NS and Glue",
              Work in Progress, Internet-Draft, draft-dickson-dnsop-ds-
              hack-00, 11 August 2021,
              <https://datatracker.ietf.org/doc/html/draft-dickson-
              dnsop-ds-hack-00>.

   [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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Appendix A.  Acknowledgments

   Thanks to everyone who helped create the tools that let everyone use
   Markdown to create Internet Drafts, and the RFC Editor for xml2rfc.

   Thanks to Dan York for his Tutorial on using Markdown (specifically
   mmark) for writing IETF drafts.

   Thanks to YOUR NAME HERE for contributions, reviews, etc.

Author's Address

   Brian Dickson
   GoDaddy

   Email: brian.peter.dickson@gmail.com

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