Internet DRAFT - draft-andrews-dnsop-update-parent-zones
draft-andrews-dnsop-update-parent-zones
Network Working Group M. Andrews
Internet-Draft ISC
Expires: May 11, 2014 November 7, 2013
Updating Parent Zones
draft-andrews-dnsop-update-parent-zones-04
Abstract
DNS UPDATE was developed to allow DNS zones to be updated.
There is a perception that UPDATE cannot be used in conjuction with
the Registry, Registar, Registrant (RRR) model to update a zone.
This document explains how UPDATE can be used in the RRR model.
Status of this Memo
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This Internet-Draft will expire on May 11, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Translation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Authentication . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Direct to Registrar . . . . . . . . . . . . . . . . . . . . . . 4
6. Indirect to Registrar . . . . . . . . . . . . . . . . . . . . . 4
7. UPDATE Server Discovery . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
UPDATE [RFC2136] is designed to update any zone in the DNS. This
includes updating delegating NS records, glue address records and DS
records.
While UPDATE is primarily designed to UPDATE a zone directly there in
no reason why UPDATE requests cannot be translated to the EPP
requests to perform the changes.
This would provide a uniform model to update parent zone regardless
of where they are in the DNS hierarchy or whether the zone is signed
or not.
2. Requirements
This document was written with the following requirements in mind:
o must be able to authenticate the transaction.
o must be able to update address records to support automated
renumbering.
o must be able to update DS records to support DNSKEY rollover buy
key management tools.
o must work for unsigned zones (parent and/or child).
o must work for signed zones (parent and/or child).
o must work for RRR managed zones.
o must work for non RRR managed zones.
o desirable support updating of NS RRsets so that nameservers can
ensure delegations delgation data remains consistent.
3. Translation
The Registrar would host a server that authenticates UPDATE requests
received directly or relayed by the Registry using TSIG [RFC2845],
then translate the actions in the UPDATE request into EPP transaction
requests. The results of those EPP transactions would be relayed to
the UPDATE client.
Requests that are not TSIG signed or fail verification must be
rejected.
The translating server would handle a restricted subset of UPDATE
requests, possibly ignoring the prerequiste section. UPDATE requests
would be limited to those supported by EPP.
e.g. Add NS record. Delete all NS records. Add A record. Delete
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AAAA record. Add DS record. Delete DS record.
The translating server may also override/ignore the TTL in the UPDATE
request.
4. Authentication
Authentication would be done using TSIG. TSIG was designed to be
used in a environment where requests are relayed.
Authentication can be done down to the <NAME,TYPE> tuple. There
exist nameservers that already implement access contols down to this
level of granularity based on the presented TSIG.
This would allow nameservers to update their own address records as
they get renumbered without being able to update anything else.
This would allow DNSSEC key management software to update DS records
without being able to update anything else.
As Registrars do all the authentication and generate the signed
responses there is no need for the Registry to have access to the
private key material used in TSIG.
Registrars already handle shared keys in these numbers with their web
interfaces so it is not unreasonable to expect them to be able to
handle a similar number of shared TSIG keys.
5. Direct to Registrar
The hardest part of Direct to Registrar is finding where to send the
UPDATE request. This would most probably just be advised to the
Registrant.
6. Indirect to Registrar
In the indirect model the Registry would host a UPDATE relay server
which would examine the first record of the UPDATE section and relay
the request to the Registrar of record for the owner name of that
record. The Registrar would verify the validity if the request based
on the TSIG then update the registry contents using EPP if
appropriate. The response from the Registrar would be relayed back
to the client via the Registry.
The Registry takes no action other than to relay the request and
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response unless it is directed to do so by the Registrar.
The relay can use either TCP or UDP when forwarding UPDATE requests
as TSIG supports changes to the DNS id field when a request/response
is relayed. Only the Registrar and the client (Registrant) need to
know the TSIG secret.
This is consistent with how tools like nsupdate work out where to
send a UPDATE request if the zone is not explicity set. They look at
the ownername of the first record and use it to discover the
containing zone.
7. UPDATE Server Discovery
UPDATE server discovery is a issue when the RRR model is in use as
the UPDATE may need to be directed through EPP and/or sent to a
Registrar. There are a number of way this could be done:
1) Adding a underscore infix labels to the zone which contain SRV
records at pointing to Registar/Registry servers for each child.
e.g. <child>._update._tcp.<parent> SRV 0 0 53 server.example.tld
The server pointed to could be be a relay server, as described above,
or a UDPATE to EPP translating server. A relay server would allow
for slower zone growth.
Using underscore infix labels requires no changes to nameservers
operated by Registries but does require the zone content to be
updated or a separate zone (e.g. _update._tcp.<parent>) to be
delegated to contain this information.
A level of indirection could be added by using CNAME records to point
to a domain operated by the registrar which contains the SRV record.
This would allow the registrar to update the SRV records without
having to update the zone being served by the registry. The CNAME
would be updated on registrar changes. Note the target name the
CNAME could also be managed by the registry as a way to consolidate
the SRV record management.
child._update._tcp.tld CNAME registrar._registrars.tld
registrar._registrars.tld SRV 0 0 53 server.example.tld
As with traditional use of SRV, non-support can be signaled with
*._update._tcp SRV 0 0 0 .
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If the Resistry is operating a relay this can be supported with a
single wildcard record.
*._update._tcp SRV 0 0 0 server.registry.tld
The client can fallback to direct update to parent servers if no SRV
record is discovered. This allows the scheme to work outside of the
registry, registrar, registant model.
2) Extend UDPATE to return the update server. Currently the Zone
section of the UPDATE refers to the zone to be update and is
identified by the <QNAME,SOA,QCLASS> tuple. Replacing SOA with one
or more of DS, NS, A and AAAA would allow a nameserver to distingish
between a traditional UPDATE request and a request to find the UPDATE
servers. The tuple would contain the resource to be updated and the
reply would contain SRV records pointing to the UPDATE servers. As
there would possibly more than one parent the owner records would
refer to the parent zone being updated.
8. Security Considerations
The UPDATE requests are all TSIG signed. This is a proven method for
securing UPDATE requests in the DNS.
9. Normative References
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997.
[RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, May 2000.
Author's Address
M. Andrews
Internet Systems Consortium
950 Charter Street
Redwood City, CA 94063
US
Email: marka@isc.org
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