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Versions: (draft-sury-dnsext-cname-dname) 00 01

dnsop                                                            O. Sury
Internet-Draft                               Internet Systems Consortium
Updates: 1034 (if approved)                                July 15, 2018
Intended status: Standards Track
Expires: January 16, 2019


                      CNAME+DNAME Name Redirection
                  draft-sury-dnsop-cname-plus-dname-01

Abstract

   This document updates RFC1034 to allow coexistence of the CNAME
   Resource Record with DNAME Resource Record at the same owner node,
   which provides redirection for a sub-tree of the domain name tree in
   the DNS system, in a parent zone.  By allowing this cooexistence, DNS
   system will have a way how to create a sub-tree redirection together
   that includes the Resource Records owner name.  This would allow
   parent zones to create full domain aliases.

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on January 16, 2019.

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
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   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



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  CNAME+DNAME Bundle  . . . . . . . . . . . . . . . . . . . . .   4
   4.  Query processing  . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Processing by Authoritative Servers . . . . . . . . . . .   4
     4.2.  Processing by Recursive Servers . . . . . . . . . . . . .   4
   5.  Implementation Report . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   RFC 1034 [RFC1034] defines CNAME resource record for cases when there
   are multiple names for single host.  A CNAME resource record
   identifies its owner name as an alias, and specifies the
   corresponding canonical name in the RDATA section of the resource
   record.  If a CNAME resource record is present at a node, no other
   data MUST be present; this ensures that the data for a canonical name
   and its aliases cannot be different.  This rule also insures that a
   cached CNAME can be used without checking with an authoritative
   server for other resource record types.

   However there is already existing exceptions to this rule.  RFC 4034
   [RFC4034] defines exception to RRSIG and NSEC records, which MUST
   exist for the same name as a CNAME resource record in a signed zone.

   RFC 6672 [RFC6672] defines DNAME resource record, which provides
   redirection for a sub-tree of the domain name tree in the DNS system.
   That is, all names that end with a particular suffix are redirected
   to another part of the DNS.

   The DNAME RR and the CNAME RR RFC 1034 [RFC1034] cause a lookup to
   (potentially) return data corresponding to a domain name different
   from the queried domain name.  The difference between the two
   resource records is that the CNAME RR directs the lookup of data at
   its owner to another single name, a DNAME RR directs lookups for data



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   at descendents of its owner's name to corresponding names under a
   different (single) node of the tree.

1.1.  Terminology

   All the basic terms used in this specification are defined in the
   documents RFC 1034 [RFC1034], RFC 1035 [RFC1035], and RFC 6672
   [RFC6672].

1.2.  Requirements Language

   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 RFC 2119 [RFC2119].

2.  Motivation

   In some languages, some characters has the variants, which look
   differently or very similar but are identical in the meaning.  For
   example, Chinese character U+56FD and its variant U+570B look
   differently, but are identical in the meaning.  If Internationalized
   Domain Label or "IDL" RFC 3743 [RFC3743] are composed of variant
   characters, we regard this kind of IDL as the IDL variant.  If these
   IDL variants are put into the DNS for resolution, they are expected
   to be identical in the DNS resolution.  More comprehensible example
   is that we expect color.example.com to be equivalent with the
   colour.example.com in the DNS resolution.  Currently this is
   something we are unable to achieve without copying the data for the
   owner of the domain record (ie. for the color.example.com) and
   keeping it in sync by some external mechanism.  The CNAME+DNAME
   record placed in the parent zone will remove this need for
   synchronization.  Without this bundling mechanism, current mechanisms
   such as DNAME or CNAME are not enough capable to solve all the
   problems with the emergence of internationalized domain names.  The
   internationalized domain names may have alias or equivalence of the
   original one.

   The CNAME+DNAME is not limited to internationalized domain names.
   This bundling could be used by TLD registries to offer additional
   service for it's registrants.  F.e. a hosting company could create
   generic record for it's service and with simple CNAME+DNAME bundle it
   can create all needed DNS resource records for providing this
   service.

   There are already such uses of CNAME which violates existing DNS
   standards by replying with CNAME records in the apex of the zone.
   This proposal would allow these perpetrators to comply with the DNS
   standard again.



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3.  CNAME+DNAME Bundle

   This proposal doesn't change wire formats of the existing CNAME and
   DNAME records.  It also doesn't change handling of the CNAME and
   DNAME on the resolver side.

4.  Query processing

   Existing rules for a DNAME RR and a CNAME RR are still valid with
   following exception: The DNAME and CNAME resource records MAY co-
   exist at the same owner name in the parent zone.

4.1.  Processing by Authoritative Servers

   The authoritative server implementations MUST allow CNAME record when
   there is a DNAME record for the same name and vice versa.

   The authoritative server implementations compliant with this
   specification SHOULD add an associated DNAME record into an
   ADDITIONAL (or ANSWER?) section for any non-DNAME query along with
   the CNAME record that would be normally required.  This would allow
   recursive DNS server implementation that understand the DNAME record
   to synthetize the answers for the subtree directly without making an
   additional queries to the respective authoritative DNS servers.

4.2.  Processing by Recursive Servers

   The recursive server implementations MUST NOT deny CNAME record when
   there is a DNAME record already present in the cache for the same
   name and vice versa.

   The recursive DNS server implementation SHOULD accept the extra DNAME
   resource record that would be returned along with the CNAME record in
   the ADDITIONAL (or ANSWER?) section.

5.  Implementation Report

   The author has implemented a change for BIND 9 authoritative server
   during the IETF Hackathon in Montreal, and the domain with
   CNAME+DNAME can be tested at www.cname-plus-dname.rocks.

   The conducted experiment confirmed that BIND, Unbound and Google
   Public DNS work fine, Knot Resolver has a bug that makes the DNS
   answer contain the DNAME records, but with RCODE=SERVFAIL, and
   PowerDNS returns RCODE=SERVFAIL for any DNAME query.  The other
   public DNS implementations follow the errors of their respective
   deployed software.




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6.  Security Considerations

   In case the recursive DNS server looking for records has enabled DNS
   Query Name Minimization (RFC 7816 [RFC7816]), the CNAME+DNAME
   specification might make the resolver send one more label than needed
   from the original DNS Query Name to the nameservers authoritative for
   the CNAME+DNAME records unless the authoritative DNS server
   preemptively returns DNAME record along with the CNAME resource
   record for the minimized query, and at the same time the recursive
   DNS server understand the additional data in the answer and utilizes
   it to synthetize the answer.

7.  IANA Considerations

   This document makes no requests of IANA.

8.  References

8.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [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>.

   [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>.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <https://www.rfc-editor.org/info/rfc4034>.

   [RFC6672]  Rose, S. and W. Wijngaards, "DNAME Redirection in the
              DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
              <https://www.rfc-editor.org/info/rfc6672>.

8.2.  Informative References








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   [RFC3743]  Konishi, K., Huang, K., Qian, H., and Y. Ko, "Joint
              Engineering Team (JET) Guidelines for Internationalized
              Domain Names (IDN) Registration and Administration for
              Chinese, Japanese, and Korean", RFC 3743,
              DOI 10.17487/RFC3743, April 2004,
              <https://www.rfc-editor.org/info/rfc3743>.

   [RFC7816]  Bortzmeyer, S., "DNS Query Name Minimisation to Improve
              Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016,
              <https://www.rfc-editor.org/info/rfc7816>.

Author's Address

   Ondrej Sury
   Internet Systems Consortium
   CZ

   Email: ondrej@isc.org

































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