Network Working Group E. Lewis
Request for Comments: 3130 NAI Labs
Category: Informational June 2001
Notes from the State-Of-The-Technology: DNSSEC
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This is a memo of a DNSSEC (Domain Name System Security Extensions)
status meeting.
1.0 Introduction
A meeting of groups involved in the development of the DNS Security
Extensions (DNSSEC) was held in conjunction with the 49th IETF. The
discussion covered the extent of current efforts, a discussion of
what questions are being asked of DNSSEC, and what is needed by the
IETF to progress the definition to the Draft Standard level.
DNSSEC [RFC 2535] has been under consideration for quite a few years,
with RFC 2535 being the core of the most recent definition. DNSSEC
is part of the charter of two working groups, DNSEXT and DNSOP.
ISC's BIND v8.2 implemented part of the specification, BIND v9
represents the first full implementation. In 1999 and 2000, more
than a half dozen workshops have been held to test the concepts and
the earliest versions of implementations. But to date, DNSSEC is not
in common use.
The current collective wisdom is that DNSSEC is 1) important, 2) a
buzzword, 3) hard, 4) immature. To capture the true state of the
technology and identify where work is needed, an informal gathering
of groups known to be involved in DNSSEC was held in conjunction with
the 49th IETF. The attendees represented NLnet Labs, The Foundation
for Internet Infrastructure, RIPE NCC, ARIN, CAIRN (ISI and NAI
Labs), NIST, DISA, RSSAC, Network Associates and Verisign
(COM/NET/ORG TLDs).
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The agenda of the meeting consisted of three items. Reports from
each group on their current research goals were followed by a
discussion of questions being asked of DNSSEC. Finally, with
reaching Draft Standard status as a goal, what was needed to make
this happen was considered.
This report is not simply a transcript of the meeting, it is a
summary. Some of the information presented here was obtained in
direct contact with participants after the meeting.
1.1 What does the term "DNSSEC" mean?
One of the comments made during discussions is that DNSSEC does not
refer to just one monolithic technology. The term has come to refer
to "toolbox" of techniques and methodologies, that when used properly
can improve the integrity of the DNS. Given this observation, it can
be seen that some portions of DNSSEC are evolving much more rapidly
than other portions. In particular, TSIG [RFC 2845] has certainly
reached a level "being deployable" for zone transfers.
The following four components are considered to be part of DNSSEC.
The concept of digital signature protection of DNS traffic as
described in RFC 2535 and a few support documents (such as [RFC
3008]), which is designed to protect the transfer of data on an
Internet scale. The concept of protecting queries and responses
through the less-scalable but more efficient TSIG mechanism [RFC
2845], which has applicability to zone transfers, DHCP registrations,
and other resolver to name server traffic. Secure dynamic updates
[RFC 3007], by virtue of using TSIG, can be considered to be part of
DNSSEC. Finally, the definition of the CERT resource record [RFC
2538] gives DNS the ability to become a distribution mechanism for
security data.
This definition of the components of DNSSEC is in no way definitive.
To be honest, this is a somewhat artificial grouping. DNSSEC does
not encompass all of the security practiced in DNS today, for
example, the redefinition of when and how data is cached [RFC 2181],
plays a big role in hardening the DNS system. The four elements of
DNSSEC described in the previous paragraph are grouped together
mostly because they do interrelate, but also they were developed at
approximately the same time.
2.0 Group Reports
The first part of the meeting consisted of reports of goals. From
this a taxonomy of efforts has been made to see if there are gaps in
the work.
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2.1 NLnet Labs
Efforts by NLnet Labs are directed towards yielding an understanding
of the impact of DNSSEC on ccTLDs, specifically .de (Germany), .nl
(The Netherlands), and .se (Sweden). Work to date has studied the
problem of applying digital signatures and NXT records to a zone.
The conclusion drawn is that there are no real problems regarding
memory or CPU speed when signing large zones, not even for ".com."
NLnet Labs has offered to work with Verisign to examine this further.
NLnet Labs is trying to define and document procedures for TLD
registries, registrars and registrants to properly handle actions
like zone-resigning and key-rollover at the root, TLD, and lower
levels. The outcome so far is that the DNSOP Roll Over proposal
seems impractical or possibly even impossible to implement at large
TLDs. NLnet Labs will produce a draft on an alternative KEY+SIG
handling scheme where SIGs are only kept in the zone where the
corresponding zone-KEY is located. This scheme reduces the necessary
actions for resigning zones from 2 levels (current zone and all
children) to 1 level (current zone), and for key-rollover from 3
levels (parent, current zone and all children) to 2 levels (parent
and current zone).
2.2 Verisign
Verisign's registry operations and corporate components have been
investigating what DNSSEC means to very large zones, not just from a
hardware point of view, but from an institutional point of view.
With the service of providing delegations already commercialized,
they are attempting to define what it would take to provide a DNSSEC
service. An important issue is the parent validation of each
delegated zone's keys.
2.3 The Foundation for Internet Infrastructure
The Foundation for Internet Infrastructure, an organization in
Sweden, is running a project with two parts. One part is directed at
the "topology" of the participants in DNSSEC, the other part of the
project is directed towards general development of tools.
The study is examining the administrative issues of running DNSSEC.
One issue is the possible 4-party interaction in the use of DNSSEC.
The four parties are the registry, the registrar, the registrant, and
the DNS operator. Of these four parties, any combination may occur
within one entity, such as a registrant that operates their own DNS
as part of their information technology department.
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The other part of the study is looking at what happens in the
resolver. Goals include DNSSEC-enabling tools such as ISAKMPd (an
IPSEC key negotiation software) secure NTP4, and e-mail. Part of
this effort is implemented in the sigz.net experiment, information on
this exists at www.sigz.net.
2.4 RSSAC
The RSSAC (Root Server System Advisory Committee) has come to the
conclusion that TSIG is worthwhile and should be deployed. There is
no schedule for deployment, however.
As for the rest of DNSSEC, there is a need to better understand the
impact of the new features before being introduced into production.
Currently issues regarding potential testbeds are being documented.
Two fundamental assumptions are that a DNSSEC testbed involving the
root servers is desirable and that such a testbed would allow for
long term testing. The latter assumption is based upon the need to
understand how repeated zone key validations can occur at multiple
independent levels of the DNS hierarchy.
2.5 CAIRN
CAIRN (Collaborative Advanced Interagency Research Network) is a
DARPA-sponsored network for collaborative research. A funded
activity that involves DNSSEC is FMESHD, shorthand for Fault-Tolerant
Mesh of Trust in DNSSEC. The effort of this activity is to determine
a means of building a resolver's chain of trust when some of the DNS
tree is unavailable or unsecured. An early deliverable of this is an
extension of secure shell to retrieve keys from DNSSEC. As part of
this activity, the use of DNSSEC in a non-major provider zone is
being implemented and studied.
2.6 NIST
NIST is collecting performance information regarding DNSSEC. One of
the fears in adopting DNSSEC is the workload it adds to existing DNS
machine workload. The hopes of this effort is to quantify the fear,
to see if it is real or imagined.
If time permits, there may be an effort to implement a zone integrity
checking program (implemented in Java) that will look for missteps in
the use of DNSSEC. Base code exists, but needs work (beyond the
current baseline).
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2.7 DISA
The U.S. Defense Information Systems Agency is providing funds to
have DNSSEC implemented in BIND. Of particular interest is making
sure that the DNSSEC specifications are correct, that BIND adheres to
the specifications, and that BIND is available on the operating
systems in use by the US Department of Defense. DISA expects that
every line of code developed through this effort be made publicly
available as part of stock BIND releases.
2.8 RIPE NCC
The RIPE NCC is looking at the impact of DNSSEC on IP-registries.
The RIPE NCC is planning to coordinate and assist in the deployment
of DNSSEC. Because the RIPE NCC is the Regional Internet Registry
for Europe the focus will be on the deployment of DNSSEC on the
reverse map tree (in-addr.arpa for IPv4).
2.9 ARIN
ARIN is investigating DNSSEC for use in signing its delegated zones
under in-addr.arpa. It participated in a dnssec workshop following
NANOG 20 held in Washington, DC in October, 2000. It also
participated in an ipv6-dnssec workshop that followed IETF 49 in San
Diego, California. Additionally, ARIN has stood up a server
dedicated to testing various dns experimentation, including dnssec
and carrying out limited testing.
2.10 Network Associates
NAI is pressing to get the tislabs.com zone running in accordance
with DNSSEC. This is an example of a non-Internet service provider
(neither an IP transit, IP address allocation, nor a domain name
managing entity) making use of DNSSEC within the normal operations of
the Information Technology department.
2.11 ip6.int. domain
The name servers authoritative for the ip6.int. domain are mostly
upgraded to be able to support CERT records and TSIG. Once this is
fully accomplished and proposals are approved, TSIG and CERT records
will be used. Further DNSSEC work is unknown.
2.12 Topology Based Domain Search
Topology Based Domain Search (TBDS), is a DARPA funded activity
investigating how DNS may continue to run in disconnected parts of
the Internet. Topics of interest (either covered by this project, or
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associated with the project) are the use of split keys, self-signed
zone (keys), and multiple signing algorithms. A goal is the
establishment of signed infrastructure zones, facilitating the
creation of a distributed CA for activities like IPSEC and FreeSwan.
3.0 Taxonomy of efforts and What is missing
The efforts being undertaken appear to cover a broad range of work
areas, from large domain registries to domain name consumers. Work
has been progressing in the production of zones (signing, key
management), and is starting in the use (resolver) of DNSSEC secured
data.
From the discussion, there were no apparent areas lacking attention.
Additional input in some areas is needed however, particularly in
making use (applications and IT department) of DNSSEC.
4.0 Questions facing DNSSEC
By the 49th IETF meeting, the most pressing question on DNSSEC is "is
it deployable?" From just the emphasis placed on this question, the
meeting generated a list of questions and made sure that either the
answer was known, or work was being done to address the question.
4.1 Is it deployable? When?
The usual answer to this has been "not now." When is always off into
the future - "about a year." To get to a deployable point, a series
of workshops have been held since the spring of 1999.
At this point, it is becoming clearer that longer term workshops are
needed. In going through the motions of any workshop, the number of
issues raised that impact the protocol's specification is
diminishing, as well as implementation issues. As such, one or two
day workshops have been helping less and less in reaching deployment.
What is needed is to run longer term test configurations, possibly
workshops that are help in conjunction with other events and that
assume continuity. This will allow a better assessment of the issues
that involve the passage of time - expirations on key validations,
etc.
As was noted in section 1.1, and touched on in section 2, one
component of DNSSEC, TSIG, is more advanced that the others. Use of
TSIG to protect zone transfers is already matured to the "really good
idea to do stage" even if other elements of DNSSEC are not. Using
TSIG to protect traffic between local resolver and their "default"
recursive name server still needs more work, however.
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4.2 Does DNSSEC work? Is it the right approach?
Currently there is a lot of effort into making the specification as
proposed work. There is some effort in assessing the specification
at this point, particularly the value of the NXT records and possible
replacements of it.
There seems little question on value of the KEY and SIG records.
There is some research still needed on KEY validation across zone
boundaries. Such work is at least scheduled.
4.3 How will client software make use of DNSSEC?
There are a number of efforts to take existing applications and have
them make direct use of DNSSEC to carry out their functions. One
such example is secure shell.
When or whether DNSSEC will be understood in the (using POSIX-like
terms) operating systems "gethostbyname" and similar routines has not
been addressed.
4.4 What are the remaining issues?
There are still a few protocol issues. The NXT resource record is
designed to provide a means to authentically deny data exists. The
problem is that the solution proposed may be worse than the problem,
in the eyes of some. There is an alternative proposal, the NO
resource record, under consideration in the DNSEXT working group. At
the present time, the DNSEXT working is considering the following
question: Is there a need to authentically deny existence of data, if
so, which is better, NXT (being incumbent) or NO?
Another less defined issue is the mechanism for parent validation of
children signatures. Although the protocol elements of this are
becoming settled, the operational considerations are not, as
evidenced by work mentioned in section 2. DNSSEC interactions have
also been referenced in discussions over a standard registry-
registrar protocol.
5.0 Progressing to Draft Standard
The IETF goal for DNSSEC is to progress the documents through the
standards track [RFC 2026]. Currently, RFC 2535 is the second
iteration at the Proposed standard level. There is a need to cycle
through Proposed once more. Following this, the next goal is Draft.
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To pass to the Draft Standard level, two main requirements must be
met. There must be two or more interoperable implementations. There
must also be sufficient successful operational experience.
5.1 Revision of RFC 2535 via DNSEXT
DNSEXT will soon begin a rewrite of the RFC 2535 specification (and
its support documents), rolling in updates and clarifications based
upon implementation and testing experience.
5.2 Operations document(s) via DNSOP
DNSOP will continue to be the forum for operations documents based
upon DNSSEC activity. There is a need for the community to provide
more documents to this group.
5.3 Interoperability
Demonstrating interoperability of DNSSEC, meaning the interaction of
two different implementations when performing DNSSEC work, poses an
issue because, to date, only BIND is seriously being fitted with
DNSSEC. There are other partial implementations of DNSSEC
functionality, so the potential for partial interoperability
demonstrations may exist.
During the meeting, it was realized that given goals stated, a second
DNSSEC implementation is needed in 18 months. Various folks in the
room mentioned that they would begin see what could be done about
this.
6.0 Acknowledgements
The following people attended the meeting and/or provided text for
this report (in no particular order): Mark Kosters (Network
Solutions), Patrik Faltstrom (Cisco), Ted Lindgreen and Miek Gieben
(NLnet Labs), Jaap Akerhuis (SIDN), Olaf Kolkmann (RIPE NCC), Bill
Manning and Dan Massey (ISI), Martin Fredriksson, Hakan Olsson and
Jakob Schlyter (Carlstedt Research & Technology), Doug Montgomery and
Scott Rose (NIST), Johan Ihren and Lars-Johan Liman (Autonomica),
Brian Wellington (Nominum), Kevin Meynell (CENTR), Ed Lewis and
Olafur Gudmundsson (NAI Labs).
7.0 IANA Considerations
This document does not involve assigned numbers in any way.
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8.0 Security Considerations
This document, although a discussion of security enhancements to the
DNS, does not itself impact security. Where security issues arise,
they will be discussed in the Security Considerations of the
appropriate document.
9.0 References
The text of any RFC may be retrieved by a web browser by requesting
the URL: ftp://ftp.isi.edu/in-notes/rfc<wxyz>.txt, where "wxyz" is
the number of the RFC.
[RFC 2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC 2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", July 1997.
[RFC 2535] Eastlake, D., "Domain Name System Security Extensions",
March 1999.
[RFC 2538] Eastlake, D. and O. Gudmundsson, "Storing Certificates in
the Domain Name System", March 1999.
[RFC 2845] Vixie, P., Gudmundsson, O., Eastlake, D. and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", May 2000.
[RFC 3007] Wellington, B., "Secure Domain Name System Dynamic
Update", November 2000.
[RFC 3008] Wellington, B., "Domain Name System Security Signing
Authority", November 2000.
10.0 Editor's Address
Edward Lewis
3060 Washington Rd (Rte 97)
Glenwood, MD 21738
Phone: +1(443)259-2352
EMail: lewis@tislabs.com
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11.0 Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
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English.
The limited permissions granted above are perpetual and will not be
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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