Internet DRAFT - draft-wouters-dnsop-secure-update-use-cases
draft-wouters-dnsop-secure-update-use-cases
DNSOP P. Wouters
Internet-Draft Red Hat
Intended status: Informational July 9, 2012
Expires: January 10, 2013
Secure parent-child DNS update use cases
draft-wouters-dnsop-secure-update-use-cases-00.txt
Abstract
DNS zone administrators occasionally need to update data published by
a parent zone, such as NS and DS records. Traditionally these
updates have happened out-of-band: through DNS registrar interfaces,
EPP, websites, or manually by operators. Some updates could also be
done using DNS Dynamic Update [RFC2136].
The IETF's DNSOP working group is considering proposing additional
mechanisms for such updates, possibly leveraging DNSSEC for
authentication.
This document presents some use cases to drive this design work.
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
working documents as Internet-Drafts. The list of current Internet-
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 January 10, 2013.
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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. DNS records with use cases for automated updates . . . . . . . 4
3.1. The DS RRset . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. The NS RRset . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Glue records . . . . . . . . . . . . . . . . . . . . . . . 5
4. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. DNSSEC use cases in the Registant, Registrar, Registry
model . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.1. Registrar has not adopted DNSSEC . . . . . . . . . . . 5
4.1.2. Registrar supports DNSSEC tediously . . . . . . . . . 5
4.1.3. sub-Registrar supports DNSSEC but Registrar does
not . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1.4. Registrant not setup to talk EPP to Registrar . . . . 6
4.2. DNSSEC use cases with direct parent-child DNS server
communication . . . . . . . . . . . . . . . . . . . . . . 6
4.2.1. DNS management solution of different vendors
cannot communicate . . . . . . . . . . . . . . . . . . 6
4.2.2. DNS management solution requires non-DNS traffic
and new Authentication method . . . . . . . . . . . . 6
4.2.3. DNS Management GUI tools are lacking DNSSEC support . 6
4.2.4. DNS management solution does not handle when being
both child and parent . . . . . . . . . . . . . . . . 7
4.3. Non-DNSSEC related DNS record updates . . . . . . . . . . 7
4.3.1. NS record and glue updates for the parent . . . . . . 7
4.3.2. Parent changes its infrastructure . . . . . . . . . . 7
5. Relationships of zones and name servers . . . . . . . . . . . 7
5.1. Hidden primary servers . . . . . . . . . . . . . . . . . . 8
5.2. Offline private keys . . . . . . . . . . . . . . . . . . . 8
5.3. Parent infrastructure . . . . . . . . . . . . . . . . . . 8
5.4. Update capability indicator . . . . . . . . . . . . . . . 8
5.5. Legalities . . . . . . . . . . . . . . . . . . . . . . . . 8
6. The in-band update process . . . . . . . . . . . . . . . . . . 8
6.1. No automatic updates . . . . . . . . . . . . . . . . . . . 8
6.2. Automatic child to parent updates for the DS record
only . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. Fully-automatic child to parent updates . . . . . . . . . 9
6.4. Automatic parent to child updates . . . . . . . . . . . . 9
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6.5. Fully-automatic child and parent synchronization . . . . . 9
6.6. Semi-automatic update . . . . . . . . . . . . . . . . . . 9
7. Applicability of automated updates to DNS infrastructure
records . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Administrative Criteria . . . . . . . . . . . . . . . . . 9
7.1.1. Contractual obligations . . . . . . . . . . . . . . . 9
7.1.2. Company policy . . . . . . . . . . . . . . . . . . . . 10
7.1.3. Separation of roles . . . . . . . . . . . . . . . . . 10
7.2. Content criteria . . . . . . . . . . . . . . . . . . . . . 10
7.2.1. DS update changing a secure zone to become insecure . 10
7.2.2. DS update changing a zone to become bogus . . . . . . 10
7.2.3. DS update changing a zone to become secure . . . . . . 11
7.2.4. NS update causing an outage . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Existing mechanisms for child-to-parent communication in DNS have
some constraints that limit their utility. In particular, they
require an authentication, which typically requires an extra
credential to be exchanged between parent and child. With the advent
of DNSSEC, it might be possible to use DNSSEC to authenticate these
updates.
Furthermore, current mechanisms such as dynamic update also require
that the child zone be able to reach the master server for the parent
zone. In environments with hidden masters, offline DNSSEC signers or
other network architecture constraints, this is not always be
feasible.
This document identifies the main targets and use cases for automated
updates and the concerns related to such automation.
[Note: While the document describes the use-cases with the zone, not
the name server, as actor, this should not be taken to mean the
signaling must be within the zone ]
2. Terminology
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].
3. DNS records with use cases for automated updates
This document limits the scope of use cases to those DNS records that
relate to the parent-child relationship itself. Policies for the TTL
could be dictated by the parent or the child, depending on the
relationship.
3.1. The DS RRset
The DS record needs to be updated when the child zone performs a Key
Signing Key rollover. The parent name server cannot necessarily
confirm the updated information by looking into the child zone, for
example when the child zone has a spare, unpublished, DNSKEY record.
Some parents want to receive DNSKEYs and create the DS record based
on the received record. Other parents do not want to be responsible
for creating any data for the child, and want to receive ready-made
DS records, optionally restrained by the parent's choices of valid
algorithms.
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3.2. The NS RRset
Both the child and the parent have a copy of the NS RRset. These
RRsets are supposed to be identical. If they differ, it is referred
as a "Lame Delegation". Keeping these sets synchronized would result
in fewer lame delegations. Modifying the NS RRset is more
complicated, as it could involve talking to name servers who do not
yet know about the zone.
3.3. Glue records
Glue records are A or AAAA records that are needed to resolve an NS
record that has a recursive relationship. For example, if the NS
record for example.com points to ns.example.com, then a glue record
is added to the parent zone (.com) for ns.example.com. Note that
ns.example.com could be used in NS records for other zones as well.
4. Use cases
There are different kind of parent-child relationships. A very
common relationship is the TLD registry using a Registry-Registrar-
Registrant model. In this model, the child dictates the content to
the parent. Another common parent-child relationship is the
corporate relationship where the head office dictates some parent
zone content to the child.
4.1. DNSSEC use cases in the Registant, Registrar, Registry model
4.1.1. Registrar has not adopted DNSSEC
Registrant running the child zone needs to convey their DS record to
the Registry running the parent zone. Registrant can only
communicate to the Registry using a Registrar. This Registrar does
not support the EPP option to convey the DS record from Registrant to
Registry. By sending an update via DNS to the Registry, Registrant
bypasses the limitations of the Registrar. This use case would
require some kind of boot-strap.
4.1.2. Registrar supports DNSSEC tediously
Registrar supports sending a DS record to the Registry via EPP.
Registrant needs to use a human-oriented website interface of
Registrar, which is very hard to automate and would break every time
Registrar modifies their website for Registrants. By sending an
update via DNS to the Registry, Registrant bypasses the limitations
of the Registrar.
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4.1.3. sub-Registrar supports DNSSEC but Registrar does not
Registrant can send DNSSEC updates to their (sub)Registrar, but the
Registrar does not support receiving updates from sub-Registrar and
sub-Registrar cannot communicate to Registry directly. The
Registrant or sub-Registrar could bypass the limitations of the
Registrar by sending DNSSEC updates directly to the Registry.
4.1.4. Registrant not setup to talk EPP to Registrar
Registrant is a lightweight entity using an off-the-shelve DNSSEC
management solution. They have no technical expertise to communicate
using EPP to the Registrar or Registry. Their DNS software could
automate sending DNSSEC updates to the Registrar or Registry.
4.2. DNSSEC use cases with direct parent-child DNS server communication
4.2.1. DNS management solution of different vendors cannot communicate
Two different vendors have implemented non-standard, vendor-specific
methods for non-DNS parent-child interaction. The DNS
administrator(s) have different devices that cannot communicate with
each other. If a generic DNS method was standardized, devices could
implement this method and inter-operate with each other.
4.2.2. DNS management solution requires non-DNS traffic and new
Authentication method
A non-DNS method for updating DS records between parent and child has
been implemented. This method requires a lot of overhead to deploy.
A new authentication method between parent and child is needed, for
which there is no standard, causing potential interoperability
issues. Firewall zones for DNS servers need to be updated to allow
non-DNS traffic. If a generic DNS method was standardized, devices
could implement this method and inter-operate with each other.
4.2.3. DNS Management GUI tools are lacking DNSSEC support
The DNS administrator is both administrating parent and child zone
using one or more DNS management solutions. These solutions are
running known up to date name server software but the vendor has not
yet adopted DNSSEC in their GUI. A standardized solution not
requiring additional GUI components could support updates more
readily.
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4.2.4. DNS management solution does not handle when being both child
and parent
The DNS administrator uses a vendor product that does not automate
adding the DS in the parent zone, despite the child DNSKEY being
available to it. The DNS administrator needs to manually calculate
the DS record and add it to the parent. They can no longer run
automated rollovers due to this required action that can only be
performed manually. If a generic DNS method was standardized, the
device could send updates irrespective of whether it also manages the
parent zone without additional effort.
4.3. Non-DNSSEC related DNS record updates
4.3.1. NS record and glue updates for the parent
Registrant has a difficult time keeping parent glue and NS RRsets up
to date due to using a manual process. After establishing an
authenticated relationship between parent and child using the
DNSKEY/DS records, the parent could update its glue records based on
the child zone content, either by regular polling, or by receiving a
notification of the child to update. The parent could distribute
such a notification to its siblings.
4.3.2. Parent changes its infrastructure
Parent name servers are pulling zones from different hidden primaries
run by different departments with hundreds of zones. The parent name
server infrastructure changes, and it wants to all its hidden
primaries to use a different NS RRset. The parent sends an update to
the hidden primaries to update the NS RRset for their zones. This
category would also cover dyndns solutions where clients send
individual host record updates to a parent that might change its
location.
5. Relationships of zones and name servers
While the relationship between child zone and parent zone are well
defined, in practice the chain of DNS servers involved is more
complicated. Often the authoritative servers for the child zone do
not communicate directly with the authoritative servers of the parent
zone. Any methods for signaling between the child and parent zone
should attempt to accommodate the listed infrastructure.
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5.1. Hidden primary servers
Zones could be updated with IXFR/AXFR using hidden primary servers.
DNSSEC signers often work this way. These primary name servers are
usually restricted via dedicated VPN links or firewalls, and may not
be able to determine or communicate with the required parent server
for sending or receiving updates.
5.2. Offline private keys
Some DNSSEC signing solutions keep the private key inside an HSM or
otherwise keep the private keys offline. Updates would need to be
able to be generated offline, transported to an internet connected
machine, and then transmitted to the parent zone.
5.3. Parent infrastructure
Some parent zones will require receiving updates for child zones
directly from the child name servers, facilitating their current use
of firewalls to restrict communication within the network. Other
parent zones, such as TLDs, will want to leave their current name
server structure unchanged and prefer updates for the child to a
special name server dedicated to receive these updates.
5.4. Update capability indicator
Servers or zones that do not support or allow secure updates should
not be sent repetitive update requests.
5.5. Legalities
Some deployments need to take legal restrictions into account. One
such example is the Registry, Registrar, Registrant model, where the
Registrant and Registry have no formal relationship with each other
or are prohibited from communicating directly with each other. In
such situations, secure automated updates should not be attempted.
6. The in-band update process
Depending on the appropriate process and relationship between parent
and child zone, there could be different requirements for the update
process.
6.1. No automatic updates
Records must be added or modified by the administrator of the zone
using an out-of-band method.
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6.2. Automatic child to parent updates for the DS record only
The child can send updates of its DS record to the parent, but cannot
request updates to the NS RRset or glue records. The parent must be
able to reject DS records that do not comply to its allowed selection
of valid DNSKEY algorithms.
6.3. Fully-automatic child to parent updates
The child can send updates of all its records hosted at the parent,
including DS records, NS records and glue records. The parent must
be able to reject certain updates based on local policy
6.4. Automatic parent to child updates
The parent can send updates to the child for the NS records and glue
records.
6.5. Fully-automatic child and parent synchronization
Parent and child automatically synchronize with no interaction on the
part of the operators. This could be uni-directional of bi-
directional.
6.6. Semi-automatic update
Parent and child synchronize, but only on the request of the parent
or child administrator.
7. Applicability of automated updates to DNS infrastructure records
Automation and direct communication might not be appropriate in all
scenarios. Implementations should take note of the considerations in
this section.
7.1. Administrative Criteria
There are many situations where automated updates would not be
allowed, or in practice could not be deployed in certain
jurisdictions or corporate structures. Automatic update solutions
should allow for disabling any such updates to support these
restricted deployments.
7.1.1. Contractual obligations
Some DNS deployments have contractual restrictions that prevents
certain parties from directly communicating with each other. For
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example, some TLDs using the RRR model do not allow the Registry to
talk to Registrants directly.
7.1.2. Company policy
Corporations often separate duties to different individuals or
departments, sometimes across different jurisdictions . For example,
a DNS officer in one country might not have the authorization of the
company to update a DNS zone run by a subsidiary in other country.
However, the reverse policy could also be true, where a DNS officer
in one country running the parent zone must be able to update any
child zone record of a subsidiary in another country.
7.1.3. Separation of roles
A Registrant (or "owner") of a zone might use a subcontractor to run
the infrastructure of its zone. It might not be appropriate for the
subcontractor to make any changes in the infrastructure of the zone,
despite being in possession of required private keys to send changes
to the parent. Similarly, a DNS administrator might be using a
DNSSEC signing service, but would not want to allow this signing
service to make any changes to the zone content other then signing
the zone.
7.2. Content criteria
[ Note: With NS records, are there any cases where the NS and glue
records in the parent zone should not be identical to those in the
child zone? What if the child name servers report different NS
RRsets?]
When a DNS update is requested by the child zone, the parent zone
could check and see if such an update would cause (significant?) harm
to the child zone, and potentially refuse such an update.
7.2.1. DS update changing a secure zone to become insecure
If a DS record deletion request would cause the last DS record in the
parent for that zone to be deleted, DNSSEC validation for the child
zone would change from secure to insecure. A parent zone might wish
to refuse such an update or require an additional confirmation.
7.2.2. DS update changing a zone to become bogus
The parent zone has two DS records for a child zone. Only one of
these matches a DNSKEY record in the child zone. If a DS record
deletion request would cause the valid DS record in the parent zone
to be deleted, DNSSEC validation for the child zone would change from
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secure to bogus. Similarly, if a child zone is is currently not
signed, and the parent zone receives a DS record addition request,
DNSSEC validation for the child zone would switch from insecure to
bogus. A parent zone might wish to refuse such an update or require
an additional confirmation.
7.2.3. DS update changing a zone to become secure
If a child zone becomes signed and automatically sends a DS addition
request to the parent zone, the child zone would change from insecure
to secure. This requires a sustained commitment by the child to
maintain its DNSSEC status by regularly resigning its RRSIG records.
The operators of the child zone might not be ready for such
commitment, resulting in the zone becoming bogus at a later state. A
parent zone might wish to refuse such an update or require an
additional confirmation.
7.2.4. NS update causing an outage
If a child zone sends an NS update to the parent, the parent zone
could check if the new NS records are properly configured to serve
the child zone, guaranteeing that no service interruption would be
caused by this update. A parent zone might wish to ignore such an
update without an explicit override flag. This might be especially
important to DNS operators that are unaware of these new DNS update
mechanism and believe that changing zone content on the child would
never cause any impacts to the parents.
8. Security Considerations
[Note: This currently overlaps with the section above]
An update of a DS record could change the authentication state of the
parent-child relationship and should be handled with care. [ Note: or
require out-of-band signaling?]
9. IANA Considerations
This Internet Draft includes no request to IANA.
10. Acknowledgements
[ Note: none yet ]
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11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative References
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
Author's Address
Paul Wouters
Red Hat
Email: pwouters@redhat.com
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