One document matched: draft-eastlake-local-names-00.txt
INTERNET-DRAFT Local Domain Names
July 1997
Expires January 1998
Local DNS Names
----- --- -----
Donald E. Eastlake 3rd
Status of This Document
This draft, file name draft-eastlake-local-names-00.txt, is intended
to be become an Informational RFC. Distribution of this document is
unlimited. Comments should be sent to the DNS mailing list
<namedroppers@tis.com> or to the authors.
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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Abstract
A set of second level domain names are defined under a new top level
domain name such that local private DNS zones can be maintained
similar to the private IP addresses reserved in RFC 1918 but which
locally appear to be part of the global DNS name tree.
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Table of Contents
Status of This Document....................................1
Abstract...................................................1
Table of Contents..........................................2
1. Introduction............................................3
2. The .local Top Level Domain.............................4
2.1 Local DNS Servers......................................4
2.2 Local in-addr.arpa Zones...............................4
2.3 Name Conflicts.........................................5
2.4 Nested Enclaves........................................5
3. Security Considerations.................................6
3.1 Interaction with DNSSEC................................6
3.2 Network Abuse..........................................6
3.3 Strength of Privacy Offered............................6
References.................................................8
Author's Address...........................................8
Expiration and File Name...................................8
Appendix A: the .local zone................................9
Appendix B: the .in-addr.arpa zone.......................11
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1. Introduction
The global Internet Domain Name System (DNS) is documented in RFC
1034, 1035, 1591 and numerous additional Requests for Comment. It
defines a tree of names starting with root, ".", immediately below
which are top level domain names such as .com and .us as discussed in
RFC 1591. Below top level domain names there are normally additional
levels of names.
Generally the information in the DNS is public and intended to be
globally accessible. Certainly, in the past, the model of the
Internet was one of end-to-end openness. [RFC 1958] However, with
increasing security threats and concerns, firewalls and enclaves have
appeared. In many cases, organizations have hosts or resources that
they specifically want to reference with DNS names but which they
also want to be walled off from global access and even from global
knowledge of the DNS name.
In the realm of IP addresses, this has been accomplished by reserving
three blocks of addresses as documented in RFC 1918.
In the DNS area, local private names have generally be achieved in
the past by "splitting" DNS at the enclave boundary, giving different
answers to resolvers depending or whether they are inside or outside
of the enclave, using different servers for inside and outside,
creating fake local root servers, and similar relatively complex
configuration diddling, which is arguably at variance with the simple
global tree structure of the DNS.
The document specifies an alternative approach to achieving the
effect of local names.
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2. The .local Top Level Domain
The fundamental idea, as described in more detail below, is to define
second level domains under .local which are served by DNS name
servers that have private IP addresses. These server addresses would
only be routed within the enclave to which the names are local. Thus
the servers and the names and resource records inside them would
automatically be inaccessible outside the enclave.
2.1 Local DNS Servers
A variety of second level names are provided in the .local zone each
of which is a delegation point to a zone with some number of name
servers in one of the private IP address space blocks. The Appendix A
to this document gives the recommended content of the .local zone.
Glue records are provided to give private IP addresses for initial
servers; however, it should be noted that the NS and A records in the
local zones will dominate the information stored in the .local zone.
This means that once a resolver has contacted a local server, the
list of NS RRs in the local zone on that server will control and
could contain more servers than were given at the chosen ??.local
delegation point.
It is only necessary for the local DNS servers to have private IP
addresses to achieve the effect of local names. Any address pointers
associated with these local names would most likely point to private
IP addresses but could point to global addresses. However, care MUST
be taken that none of the local DNS servers or any server that might
cache their output is accessible by any network interface that has a
non-private IP address. Otherwise considerable confusion could
result if local names are resolved by a resolver outside a local
enclave to private IP addresses which have a different meaning for
the resolver.
2.2 Local in-addr.arpa Zones
Inverse lookup of local names corresponding to private IP addresses
needs to be provided via the in-addr.arpa zone. Appendix B contains
recommended additions to the in-addr.arpa zone to accomplish this.
Because of the fixed naming within this zone, different names with
different numbers of servers can not be provided but two servers
should be sufficient. As with the forward ??.local entries, the
actual NS RRs in the servers serving the private portions of in-
addr.arpa will dominate. When one of these is queried by a resolver,
it can provide information on additional servers for that particular
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subzone in the private IP address portion of the in-addr.arpa tree.
2.3 Name Conflicts
The intention is that local names would only be used in the enclave
where the entities they refer to exist, and these names would not be
exported. However, experience indicates that such names will leak
out and can cause confusion and if they can conflict with global
names or names local to other enclaves. Use of the .local TLD
assures no conflict with global names. To assure no conflict with
different local names, the domain name of the enclave SHOULD always
be prefixed to .local.
For example, a company might have
www.company.com.xx
as a globally accessible web server and
www.company.com.xx.b3.local
as a web server for internal use only. The global name could
normally be resolvable anywhere on the Internet while the local name
could not be resolved anywhere except within the company enclave.
2.4 Nested Enclaves
It is possible to have enclaves within enclaves. In general the best
way to accomplish this is to use a different portion of the private
IP address space at each level of enclave. (Private IP address space
can be reused in enclaves that are siblings or the like.) Then
similar entries to those proposed here for .local can be made in the
private zone referring to name servers with addresses in the nested
enclaves IP address space.
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3. Security Considerations
3.1 Interaction with DNSSEC
Although an enclave may derive some small amount of security by
virtue of its isolation, it will normally be desirable to implement
DNS security [RFC 2065] within the enclave. The enclave owner should
generate their own keys and sign their ??.local zone. However, a
signed copy of their public key can not be included in the .local
zone as it is different for every enclave. Thus, to authenticate the
??.local zone contents, it will be necessary to staticly configure
the public key for the ??.local zone in local resolvers or cross sign
the KEY RR at the apex of the local ??.local zone with another key
that is trusted by local resolvers.
3.2 Network Abuse
Use of the defined second level domain names under .local in URLs,
email return addresses, or the like, can cause DNS, SMTP, and many
other types of references to IP addresses in the RFC 1918 blocks.
This can occur from within a firewall due to web browsing or email
processing of web pages or email from virtually anywhere in the
Internet. However, this is not a new situation as anyone who
controls any zone in the DNS, say zone.foo.example, can create
entries therein with arbitrary IP addresses (including multicast and
undefined formats) and then, by using these name entries in email,
web links, etc., cause a variety of spurious protocol connections to
those addresses.
Local names may provide another way for network abusers to create
confusion to cover their tracks and make abuse hard to trace. But
ephemeral or unreachable names can be created currently via rapid
zone changes or delegation to non-existent server. Use of .local at
least provides some warning that a name may be unreachable..
3.3 Strength of Privacy Offered
It should be noted that the privacy of the DNS information protected
by storing it in servers with private IP addresses is relatively
weak. It is completely dependent on the integrity of enclave
perimeter routing to make these servers inaccessible.
Software should not depend on local names being accessible only
within a particular enclave as someone could deliberately create the
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same names within a different enclave even if they include the name
of the original enclave to try to avoid such conflicts.
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References
RFC 1033 - M. Lottor, "Domain Administrators Operations Guide",
November 1987.
RFC 1034 - P. Mockapetris, "Domain Names - Concepts and Facilities",
STD 13, November 1987.
RFC 1035 - P. Mockapetris, "Domain Names - Implementation and
Specifications", STD 13, November 1987.
RFC 1591 - J. Postel, "Domain Name System Structure and Delegation",
03/03/1994.
RFC 1918 - Y. Rekhter, R. Moskowitz, D. Karrenberg, G. de Groot, E.
Lear, "Address Allocation for Private Internets", 02/29/1996.
RFC 1958 - B. Carpenter, "Architectural Principles of the Internet",
06/06/1996.
RFC 2065 - D. Eastlake, C. Kaufman, "Domain Name System Security
Extensions", 01/03/1997.
Author's Address
Donald E. Eastlake 3rd
CyberCash, Inc.
318 Acton Street
Carlisle, MA 01741 USA
Telephone: +1 508 287 4877
+1 703 620-4200 (main office, Reston, VA)
FAX: +1 508 371 7148
EMail: dee@cybercash.com
Expiration and File Name
This draft expires January 1998.
Its file name is draft-eastlake-local-names-00.txt.
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Appendix A: the .local zone
===== The .local zone ====
local. IN SOA ... ... (
1234 ; serial
90000 ; refresh, 25 hours
18000 ; retry, 5 hours
3456000 ; expiry, 40 days
43200 ) ; minimum of 12 hours
NS ... ; actual servers for .local zone
NS ...
...
a2.local. NS ns1.a2.local.
ns1 A 10.1.1.2
NS ns2.a2.local.
ns2 A 10.1.2.2
a3.local. NS ns1.a3.local.
ns1 A 10.1.1.2
NS ns2.a3.local.
ns2 A 10.1.2.2
NS ns3.a3.local.
ns3 A 10.2.1.2
a4.local. NS ns1.a4.local.
ns1 A 10.1.1.2
NS ns2.a4.local.
ns2 A 10.1.2.2
NS ns3.a4.local.
ns3 A 10.2.1.2
NS ns4.a4.local.
ns4 A 10.128.1.2
b2.local. NS ns1.b2.local.
ns1 A 172.16.1.2
NS ns2.b2.local.
ns2 A 172.16.2.2
b3.local. NS ns1.b3.local.
ns1 A 172.16.1.2
NS ns2.b3.local.
ns2 A 172.16.2.2
NS ns3.b3.local.
ns3 A 172.16.128.2
c2.local. NS ns1.c2.local.
ns1 A 192.168.1.2
NS ns2.c2.local.
ns2 A 192.168.2.2
c3.local. NS ns1.c3.local.
ns1 A 192.168.1.2
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NS ns2.c3.local.
ns2 A 192.168.2.2
NS ns3.c3.local.
ns3 A 192.168.128.2
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Appendix B: the .in-addr.arpa zone
===== Entries in the in-addr.arpa zone ====
10.in-addr.arpa. NS ns1.a2.local.
NS ns2.a2.local.
ns1.a2.local. A 10.1.1.2
ns2.a2.local. A 10.1.2.2
16.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
ns1.b2.local. A 172.16.1.2; one set of glue records
ns2.b2.local. A 172.16.2.2 ; for all the b2 cases
17.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
18.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
19.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
20.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
21.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
22.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
23.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
24.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
25.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
26.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
27.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
28.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
29.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
30.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
31.172.in-addr.arpa. NS ns1.b2.local.
NS ns2.b2.local.
168.192.in-addr.arpa. NS ns1.c2.local.
NS ns2.c2.local.
ns1.c2.local. A 192.168.1.2
ns2.c2.local. A 102.168.2.2
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