Publishing organization boundaries in the DNS
draft-levine-orgboundary-00

Network Working Group                                          J. Levine
Internet-Draft                                      Taughannock Networks
Intended status: Informational                             June 09, 2013
Expires: December 11, 2013

             Publishing organization boundaries in the DNS
                      draft-levine-orgboundary-00

Abstract

   Often, the organization that manages a subtree in the DNS is is
   different from the one that manages the tree above it.  Rather than
   describing a particular design, we describe an architecture to
   publish in the DNS the boundaries between organizations that can be
   adapted to various policy models.

Status of This Memo

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   This Internet-Draft will expire on December 11, 2013.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Design issues . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Lookup process  . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  DNS records . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Informative References  . . . . . . . . . . . . . . . . .   6
     6.2.  Normative References  . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Often, the organization that manages a subtree in the DNS is is
   different from the one that manages the tree above it.  Many
   applications use information about such boundaries to implement
   security policies.  For example, web browsers use them to limit the
   names where web cookies can be set.  SSL certificate services use
   them to determine the responsible party for the domain in a signing
   request.  Some mail security applications such as DMARC use them to
   locate an organization's policy records.

   The most widely used source of boundary data is the Public Suffix
   List, maintained by the Mozilla Foundation.  It is distributed as a
   text file available at a well known URL, with some libraries to parse
   and search it.  While it has worked adequately, it has a variety of
   issues.  Downloading the file is relatively slow, and adequate
   performance requires that each application cache a copy of the file.
   The file is in a unique format that requires a specialized parser and
   lookup routines.  The file is managed by a third party rather than
   directly by the domain owners, which may or may not be considered a
   problem.

2.  Design issues

   This design can adapt to a variety of design points.

   Policies can be published by the domains themselves, or by a third
   party.  In the former case, each domain asserts its own boundary
   policies.  In the latter case, the third party makes the assertions,
   which may or may not agree with what the domains themselves would
   want.

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   Multiple levels of delegation may be implemented, which is different
   from irregular boundaries.  For example, ca, on.ca, and toronto.on.ca
   are irregular boundaries, because they're all handled by CIRA.
   CentralNIC's uk.com would be a second level of delegation below
   Verisign's com.

   Different sets of boundary rules can be published for different
   applications.  For example, the boundaries for SSL certificates might
   be different from the boundaries for e-mail policies, or for web
   cookie setting policies.

   In the lookup process below, the boundary point data is stored in TXT
   records.  While it wouldn't hurt anything to use a new RRTYPE, it
   wouldn't be useful.  All of the DNS names used include a distinctive
   prefixed name component, so there shouldn't be any RRs at those names
   other than the TXT record for the boundary.  To avoid confusion due
   to top-level wildcards that might inadvertently cover the subtree of
   boundary records, the TXT strings contain a prefix tag.

3.  Lookup process

   Each collection of boundary data has a base name and a prefix tag.
   If domains publish their own information, the base name is the DNS
   root.  Otherwise it is a domain belonging to the publishing entity.
   The tag starts with an underscore and is intended to be unique.  All
   of the rules for a given application use the same tag.  In the
   examples below, the tag is _sb for sample boundary.

   Every valid policy record starts with a fixed prefix "ob=1 " for
   organization boundary version 1.  If a lookup returns no TXT records
   that start with the prefix, or more than one record that starts with
   the prefix, the lookup fails.

   The lookup process takes a domain name and returns the name of the
   node closest to the root that belongs to the same organization.  This
   may be the domain itself or a parent.  If there is no policy for the
   domain the lookup fails; there are no defaults and the DNS root is
   not within any organization boundary.  (Applications may apply
   defaults of their own, but that is beyond the scope of this
   specification.)

   For the first lookup, the client separates the top level component of
   the domain name from the subcomponents, if any, and inserts the
   prefix between the top level component and the subcomponents.  For
   example, if the domain to be checked is example.com, the client looks
   up example._sb.com, if the domain is www.example.com, the client
   looks up www.example._sb.com, and if the domain is just example, the
   client looks up _sb.example.  If the base name is not null, it is

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   appended to the name to be looked up, so if the name example.com were
   to be checked in a collection with the base cookies.example, the name
   looked up would be example._sb.com.cookies.example.

   If the lookup returns a valid policy record, the contents of the
   record disregarding the prefix is the domain name just above the
   policy boundary.  For example, if there is a boundary between
   example.com and the com TLD, the record would contain "ob=1 com" when
   checking example.com or www.example.com.  If there are no boundaries
   below the TLD, the policy record contains "." for the root.  For
   example, if all subdomains of the "example" TLD are under the same
   management as the TLD itself, checks for example, foo.example, and
   www.foo.example would all return "ob=1 .".

   If the lookup process only allows a single level of delegation, the
   process stops after a single lookup.  If it allows multiple levels of
   delegation, the client moves the tag just below the name below the
   boundary just found and repeats the lookup.  For example, if a lookup
   of www.foo.example._sb.com returned "ob=1 com", the next lookup would
   be www.foo._sb.example.com.  or if a lookup of www.example.on._sb.ca
   returned "ob=1 on.ca" the next lookup would be www._sb.example.on.ca.
   This process repeats until a DNS lookup returns NXDOMAIN or NODATA,
   at which point the result is the result of the last successful
   lookup.  The total number of DNS lookups is the number of levels of
   delegation, which is unlikely to be more than 1 or 2 in realistic
   scenarios.

4.  DNS records

   The publishing entity uses a combination of wildcard and non-wildcard
   names to cover the relevant name space.

   If there is a boundary below a given name, a wildcard covers the
   names below it.  For example, if there is a boundary at or
   immediately below .TEST, a suitable record would be:

   *._sb.test txt "ob=1 test"

   If the boundary is at the .TEST domain, i.e., TEST. is under the same
   management as FOO.TEXT, an additional non-wildcard record covers the
   domain itself.

   _sb.test txt "ob=1 test"

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   If the TLD has no policy for itself, e.g., the TLD has no mail policy
   because there are no mail addresses in the TLD itself, it publishes
   no policy record for itself.

   In domains with irregular policy boundaries, multiple wildcards
   describe the delegation points.  For example, in the .CA TLD, for
   national organizations there might be a boundary directly below the
   TLD, for provincial organizations a boundary below a provincial
   subdomain such as on.ca, and for local organizations, a boundary
   below a municipal subdomain such as toronto.on.ca.  A suitable set of
   wildcards covers this structure.

   *._sb.ca txt "ob=1 ca"
   *.on._sb.ca txt "ob=1 on.ca"
   *.toronto.on._sb.ca txt "ob=1 toronto.on.ca"

   The closest encloser rule in RFC 4592 [RFC4592] makes the wildcards
   match the appropriate names.

   For any set of policy boundaries in a tree of DNS names, a suitable
   set of policy records can describe the boundaries, so a client can
   find the boundary for any name in the tree with a single policy
   lookup per level of delegation.

5.  Security considerations

   The point of publishing organization boundaries is to provide advice
   to third parties that wish to know whether two names are managed by
   the same organization so the names can be treated "the same" in some
   sense.  Clients that rely on published boundaries are outsourcing
   some part of their own security policy to the publisher, so their own
   security depends on the publisher's boundaries being accurate.

   Although in some sense domains are always in control of their
   subdomains, there are many situations in which parent domains are not
   expected to mess with child subdomains, e.g., ICANN contracted gTLDs
   and registered second level domains.  Since there is no technical bar
   to a parent publishing records that shadow part or all of the
   boundary record namespace for delegated subdomains, correct operation
   depends on the parent and subdomains agreeing about who publishes
   what.

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6.  References

6.1.  Informative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

6.2.  Normative References

   [RFC4592]  Lewis, E., "The Role of Wildcards in the Domain Name
              System", RFC 4592, July 2006.

Author's Address

   John Levine
   Taughannock Networks
   PO Box 727
   Trumansburg, NY  14886

   Phone: +1 831 480 2300
   Email: standards@taugh.com
   URI:   http://jl.ly

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