Internet DRAFT - draft-kolkman-root-test-delegation
draft-kolkman-root-test-delegation
Network Working Group G. Huston
Internet-Draft APNIC
Intended status: Experimental Protocol O. Kolkman
Expires: May 20, 2014 NLnet Labs
A. Sullivan
Dyn, Inc.
W. Kumari
Google, Inc.
November 18, 2013
Using Test Delegations from the Root Prior to Full Allocation and
Delegation
draft-kolkman-root-test-delegation-02
Abstract
The delegation of certain strings as generic Top Level Domains
(gTLDs) may cause stability and security issues if such strings have
been used in private environments prior to their delegation. Test
delegations can be used to enable empirical research on the extent of
the potential for name collision. This document describes one such
approach to an empirical testing framework for name collision, and
considers the applicability of this approach to detect other forms of
name collision.
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
and may be updated, replaced, or obsoleted by other documents at any
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 May 20, 2014.
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Copyright Notice
Copyright (c) 2013 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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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . 2
1.1. Scire est mensurare . . . . . . . . . . . . . . . . . . . 3
2. Terms and Conventions Used in this Memo . . . . . . . . . . . 4
3. Principle of Operation . . . . . . . . . . . . . . . . . . . . 4
3.1. Measurements Servers and Zones . . . . . . . . . . . . . . 5
3.2. Query Generation . . . . . . . . . . . . . . . . . . . . . 5
3.3. Sampling . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Name Resolution Considerations . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction and Motivation
[[The authors are aware that this version of the document is not
fully consistent. However they would value feedback on whether the
idea is worth further study. A mail list to discuss this draft is
collisions@lists.dns-oarc.net.]]
While certain names have been reserved for internal or private use
[RFC6761], there is evidence [SAC45] that various sites connected to
the Internet have used other names for internal purposes. In fact,
the Multicast DNS specification [RFC6762] advises not to use .local
for private use and observes: "the following top-level domains have
been used on private internal networks without the problems caused by
trying to reuse ".local." for this purpose:
.intranet
.internal.
.private.
.corp.
.home.
.lan.
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In the event such names are delegated for use in the public DNS,
there will be inevitable consequences for sites that have used those
names. Some of those consequences may have security implications,
with the potential for leakage of credentials and HTTP cookies
([RFC6265]). Responsible administration of the public namespace
therefore requires careful consideration in permitting public
delegation of any name when there are grounds to believe it is in
widespread use as a private namespace, even though such private
namespaces are (from the point of view of the DNS) irregular, even if
common.
One form of name collision involves network domains that use selected
names as local-use top level domains, as noted in [RFC6762]. In the
case where the same label is delegated in the global DNS as a gTLD,
then hosts in the local domain will be unable to resolve domain names
in the context of the gTLD. This state of name occlusion is further
compounded by a number of scenarios where the resolution of a name is
performed across multiple name scope domains. This may happen with a
mobile host (in the case, for example, when the host uses a
statically defined "home page" on their local browser that is defined
within a particular local scope), or even with applications, such as,
for example, mail delivery (in the case where multiple MTAs who are
listed as mail servers for a domain reside in different name scope
domains, some of which have this name collision between the domain
and locally defined pseudo-TLDs).
Name collision opens up the potential for misdirection, where the
named remote point being contacted by the application may not
necessarily be the intended service point for the transaction. When
a host leaves the intranet environment, the host's applications may
anticipate that the DNS names associated with a label return an RCODE
3 (NXDOMAIN) response, but may encounter an unanticipated response
when the gTLD is deployed with a colliding name. Similarly, a host
that has an association with a named service point within the gTLD
may encounter unanticipated responses when the host is placed into an
intranet environment where the same name exist as a locally-scoped
pseudo-TLD.
There is a subtle form of interaction of names when the same name is
placed on a local name search list. Certain name resolver libraries
first query the original name, and if the query returns an NXDOMAIN,
then they apply the local search list to the original name. When
this process occurs in the context of a visible gTLD name colliding
with the local name there is the possibility of the name resolving in
the context of the gTLD, which then bypasses the application of the
local search list.
1.1. Scire est mensurare
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The local use of undelegated top-level domain names is troublesome
because it may produce different user experiences depending on the
locally used name, the names placed in a local search list and the
location of a given host, and the host's name resolution behaviour.
Prudent operation of the root zone requires that deployment of new
names in the root should not necessarily cause widespread untoward
effects for users of the DNS, particularly when those users are
relying on name resolution outcomes that have always been part of the
name resolution behaviour up unto this point.
What is useful in this context is a mechanism to test whether a
particular delegation from the root zone presents a conflict with
widespread local use. This memo presents a methodology for making
such a determination.
The methodology considered here depends on temporary delegation of
the top-level domains in question, and the use of a domain under an
existing TLD in order to capture and compare queries generated by a
large number of querying sources under the control of the experiment.
2. Terms and Conventions Used in this Memo
The mechanism outlined here is intended to complement the analysis
already performed in "Name Collision in the DNS" [namecollision]. We
therefore use the terms defined in section 1.1 of [namecollision]
whenever appropriate.
Note that the evaluation methodology outlined here is intended to be
complementary input to a risk analysis e.g. as found in
[namecollision]; risk tradeofs are likely to include other factors
than the effects measured herewith.
3. Principle of Operation
The goal of the experiment is to assess whether there is significant
existing use of a given candidate string ("CandidateTLD").
We propose the use of a software test that is executed by a large
number of end hosts drawn from across the entire Internet. The
execution of this test will cause the end host to attempt to retrieve
a small set of URLs. This will trigger a set of DNS queries to
resolve the domain name part of each URL, and subsequent HTTP queries
to retrieve the object in the case that the DNS name is successfully
resolved to an IP address. Both the DNS queries and the HTTP
requests are answered by dedicated servers that analyse the received
responses and match them to the original set of queries that were
used by the end host. This will allow us to infer whether the lost
is located in an context where there is name collision with the
CandidateTLD. In this section we describe the query generation, data-
collection, and analysis.
This methodology is based on earlier work by APNIC [Method].
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3.1. Measurements Servers and Zones
In addition to the use of CandidateTLD, the methodology uses an
additional name, delegated from a 'common' existing TLD,
("TestName.ExistingTLD") to the experiment's server.
The experiment's name server is authoritative for CandidateTLD and
TestName.ExistingTLD. The name server will respond to an A and AAAA
query for any name within "TestName.CandidateTLD" with the IPV4 or
IPv6 address of the experiment's HTTP server. The name server will
respond to queries for any other name within CandidateTLD with RCODE
3 (Name Error or NXDOMAIN). The name server will respond to A and
AAAA queries in TestName.ExistingTLD with the IPv4 or IPv6 address of
the experiment's HTTP server.
The experiment's HTTP server will respond with a "200 OK" for a
request for the object "1x1.png" in TestName.CandidateTLD and in
TestName.ExistingTLD. The server will respond with "404 Not Found"
for any other object name.
3.2. Query Generation
The TestName is a synthetic name with no intentional semantic
meaning, that is generated in such a way to reduce the likliehood of
collision with any existing delegated name. It is suggested that it
be generated by using the hex encoding of a randomly selected integer
value between 1,000,000,000 and 2,000,000,000. The name must not be
already delegated from the root or in the ExistingTLD.
Each query set constitutes one "measurement". A "measurement" is
identified by a measurement identifier (<uniqueid>, syntactically a
valid hostname) that is uniquely generated for each instance of a
measurement. This ensures that when the domain name is resolved, and
when the named object is retrieved there is no occlusion of the
interaction with the experiment's services because of local name or
web object caches. The set uses the following URLs:
A: http://<unique_id>-a.TestName.CandidateTLD/1x1.png?
<uniqueid>-a
B: http://<unique_id>-a.TestName.ExistingTLD/1x1.png?
<uniqueid>-b
C: http://results.TestName.ExistingTLD/1x1.png?
<uniqueid>?za=<a_result>&zb=<b_result>
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The A URL is intended to test if CandidateTLD is a locally used name.
In other words, if local use of CandidateTLD occludes visibility of
CandidateTLD as a gTLD. The DNS query for the A Fully Qualified
Domain Name (FQDN) will only be received by the authoritative name
server for this name if there is no local name resolution function
that uses the CandidateTLD name as a locally defined pseudo-top level
domain.
The B URL is intended to function as the control test for the
experiment, and the use of ExistingTLD in B is intended to operate as
a name that does not collide with a local use context.
As the experiment uses the absence of a fetch of the A URL to infer
the name resolution behaviour of the location where the measurement
is being performed, it is necessary to ensure that the measurement
code has run to completion. The measurement code starts a timer at
the start of its execution. Upon expiration of the timer, or when
both the A and B objects have been successfully retrieved, the code
will schedule the retrieval of the C URL. The arguments to the C URL
include the client-side measurement of the elapsed time to retrieve
the A and B URLs.
3.3. Sampling
One way to perform this measurement is to embed the measurement in
web content, using a scripting language. When the web content is
loaded the script is activated, and the measurement sequence is
performed.
One way to distribute this content to clients to perform the test is
via an online (ad) campaign. If the measurement script is enclosed
within the ad itself, then there is no reason for the campaign
actually to cause users to click though in order to perform the test.
Behavior of this sort is trivially achievable with a number of
available online advertising systems.
It is also necessary to spread the delivery of the ad to a very broad
spectrum of clients, uso the as should be presented across all time
zones, across all language bases, and across all geographic regions.
4. Evaluation
To evaluate the results, we take those measurements that return the C
URL. The use of the C URL ensures that we use measurement results
where the ExistingTLD name is not being locally occluded. We count
the number of experiments of each of the possible combinations of
retrieving the A and B URLs. These combinations are:
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Not A and Not B: This result contributes to experimental
uncertainty. (We know that ExistingTLD is not locally
occluded, so the failure to retrieve B is due to other factors
that are not being examined in the context of this
measurement.)
A and Not B: This result indicates that the client is able to
resolve names in the CandidateTLD in the context of the global
DNS, but the inability to retrieve the B URL contributes to
experimental uncertainty. (The same reasoning about the
ExistingTLD and local occlusion applies to this case).
Not A and B: This result is an indicator that the client's use of
CandidateTLD is probably being occluded by some form of local
use.
A and B: This result indicates that the client is able to resolve
names in the CandidateTLD in the context of the global DNS.
If the CandidateTLD is in widespread private use then we would see
the count of "Not A and B" be far in excess of the level of
experimental uncertainty, then we can conclude that there are locales
where the CandidateTLD is being used in local context. Analysis of
the source IP addresses of the clients that fetch "Not A and B", and
the BGP Origin AS of these addresses and their geolocation may
indicate if such local use is clustered in a particular network or
group or networks, or clustered in a particular geography or language
region.
5. Name Resolution Considerations
Eariler versions of this memo proposed to use this experimental
technique to detect name search list considerations. This section
describes the name search list collision considerations, and
describes some further investigation that has lead to the conclusion
that this technique would not necessarily be applicable in that
context.
The basic algorithm used in name resolution when search lists are
present appears to be consistent across a number of implementations:
various permutations of using the base name and appending individual
values from the name search list are used as DNS queries in order to
find a name that can be resolved by the local DNS resolver. The
search process stops when the DNS query returns other than an
NXDOMAIN response.
However the exact order of generating these candidate names has been
observerd to vary across implementations. To describe these
observations it is first necessary to introduce some basic
terminology. There are four generic ways that name resolution
libraries apply a search list to a "base name" in order to construct
a set of FQDN that are used in DNS queries:
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none the search list is not applied to the base name.
pre the search list is applied to the base name, then the base
name alone is used.
post the base name alone is used, then the search list is applied
to the base name.
always the search list is applied to the base name, and the base
name alone is not used.
The form of name collision with search lists, as discribed in the
introduction section of this memo, occurs in the "post" case, where
the unexpected resolution of the base name causes the search list not
to be applied to the base name, and the global name context is
applied to the base name, rather applying a local name context, as
defined by the search list.
Table 1 provides a summary of the behaviour of various operating
systems and their local name resolver library behaviour when
resolving base names that contain a single label, and names that
contain two labels. As can be seen, only Windows XP and Unix-based
libraries perform the "post" form of search name application that
would be susceptable for this form of name collision.
+---------------+--------------+-------------+
| System | Single Label | Multi-Label |
+---------------+--------------+-------------+
| MAC OSX 10.9 | always | never |
| Windows XP | always | post |
| Windows Vista | always | never |
| Windows 7 | always | never |
| Windows 8.1 | always | never |
| FreeBSD 9.1 | pre | post |
| Ubuntu 13.04 | pre | post |
+---------------+--------------+-------------+
The experimental approach described here does not necessarily use the
operating system's name resolution libraries. The experimental
technique forms a name query within the browser, so it is more
relevant to examine the behaviour of the browsers when given single
and multi-label names to lookup. Table 2 shows the behaviour of a
number of browsers on two operating system platforms. (It should be
noted that these results in Table 2 were obtained by using Javascript
to feed names to the browser. The interactive data entry procedures
in current browsers are a dual purpose URL and search engine term
data entry, and the variations on behaviour between browsers in the
way in which entered data is interpreted is more due to the
differences in the browser's input parser than it is due to any
differences in the browser's name resolution library.)
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+---------------------------+--------------+-------------+
| System | Single Label | Multi-Label |
+---------------------------+--------------+-------------+
| MacOS OSX 10.9 | | |
| Chrome (31.0.1650.39) | always | post |
| Opera (12.16) | always | never |
| Firefox (25.0) | always | never |
| Safari (7.0 9537.71) | always | never |
| Windows 8.1 | | |
| Chrome (30.0.1599.101) | always | never |
| Opera (17.0) | always | never |
| Firefox (25.0) | always | never |
| Safari (5.1.7 7534.57.2) | always | never |
| Explorer (11.0.900.16384) | always | never |
+---------------------------+--------------+-------------+
Only one browser / Operating System combination tested shows the
"post" form of search name use, namely Chrome on the Mac OSX
platform. In all other cases a single label name always has the
local search list appended, and a multi-label name never applies the
local search list.
6. Security Considerations
The delegation of the Proposed TLD (CandidateTLD) comes with some
risk of interference with existing deployments. In the case where a
local system queries a name, and that query returns a NXDOMAIN
response, then local system then queries further name forms where
each entry on a local name search list is appended to the original
name in turn, searching for a name response that is not NXDOMAIN.
The delegation of CandidateTLD for this experiment may interfere this
this behaviour.
However, two observations mitigate this concern. The first is that
this situation of potential collision arises in the case where the
local system is querying for the CandidateTLD name as a "dotless"
name (as the only delegated subdomain in the CandidateTLD zone is
TestName, which is intended to have no semantic meaning in any
language). The second observation is that for such "dotless" names,
the currently widely deployed name resolver libraries no not
initially query the "dotless" domain name then apply the search list
is the first query results in an RCODE 3 response. Many name
resolver libraries do not query for "dotless" domain names at all,
while those libraries that have been observed to perform such queries
(Windows XP, Linux, FreeBSD) perform them after using the local
search name list, rather then before.
7. References
[Method] APNIC, "APNIC Labs IPv6 Measurement System ", May 2013.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
April 2011.
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[RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
RFC 6761, February 2013.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
February 2013.
[SAC45] ICANN Security and Stability Advisory Committee, "Invalid
Top Level Domain Queries at the Root Level of the Domain
Name System", 11 2010, <http://www.icann.org/en/groups/
ssac/documents/sac-045-en.pdf>.
[namecollision]
Interisle Consulting Group, "Name Collision in the DNS",
August 2013.
Appendix A. Acknowledgements
This draft is a follow-up of, an borrows heavily from, our earlier
(abandonded) work on "A Procedure for Cautious Delegation of a DNS
Names". Discussion of that document in various hallways lead to
inspiration for this document and we want to thank those that gave us
feed-back.
The idea of using different names to trigger events in a DNS server
is due to Geoff Huston and George Michaelson.
The approach described here of using code embedded in ads delivered
by online advertisement networks to generate a large volume of URL-
based experiments performed by end users' browsers was developed by
George Michaelson, Byron Ellacot and Geoff Huston.
Authors' Addresses
Geoff Huston
APNIC
6 Cordelia St
South Brisbane, QLD 4101
Australia
Email: gih@apnic.net
Olaf Kolkman
NLnet Labs
Science Park 400
Amsterdam, 1098 XH
The Netherlands
Email: olaf@NLnetLabs.nl
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Andrew Sullivan
Dyn, Inc.
150 Dow St
Manchester, NH 03101
U.S.A.
Email: asullivan@dyn.com
Warren Kumari
Google, Inc.
1600 Amphitheatre Pkwy
Mountain View, CA 94043
U.S.A.
Email: warren@kumari.net
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