Operational Considerations for use of DNS in IoT devices
draft-richardson-opsawg-mud-iot-dns-considerations-01

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OPSAWG Working Group                                       M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Best Current Practice                 November 04, 2019
Expires: May 7, 2020

        Operational Considerations for use of DNS in IoT devices
         draft-richardson-opsawg-mud-iot-dns-considerations-01

Abstract

   This document details concerns about how Internet of Things devices
   use IP addresses and DNS names.  The issue becomes acute as network
   operators begin deploying RFC8520 Manufacturer Usage Description
   (MUD) definitions to control device access.

   This document explains the problem through a series of examples of
   what can go wrong, and then provides some advice on how a device
   manufacturer can best make deal with these issues.  The
   recommendations have an impact upon device and network protocol
   design.

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 https://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 7, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Strategies to map names . . . . . . . . . . . . . . . . . . .   3
   3.  DNS and IP Anti-Patterns for IoT device Manufacturers . . . .   5
     3.1.  Use of IP address literals in-protocol  . . . . . . . . .   5
     3.2.  Use of non-deterministic DNS names in-protocol  . . . . .   6
     3.3.  Use of a too inclusive DNS name . . . . . . . . . . . . .   6
   4.  DNS privacy and outsourcing vs MUD controllers  . . . . . . .   7
   5.  Recommendations to IoT device manufacturer on MUD and DNS
       usage . . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Consistently use DNS  . . . . . . . . . . . . . . . . . .   8
     5.2.  Use primary DNS names controlled by the manufacturer  . .   8
     5.3.  Use Content-Distribution Network with stable names  . . .   8
     5.4.  Prefer DNS servers learnt from DHCP/Route Advertisements    8
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Appendices . . . . . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   [RFC8520] provides a standardized way to describe how a specific
   purpose device makes use of Internet resources.  Access Control Lists
   (ACLs) can be defined in an RFC8520 Manufacturer Usage Description
   (MUD) file that permit a device to access Internet resources by DNS
   name.

   Use of a DNS name rather than IP address in the ACL has many
   advantages: not only does the layer of indirection permit the mapping
   of name to IP address to be changed over time, it also generalizes
   automatically to IPv4 and IPv6 addresses, as well as permitting
   loading balancing of traffic by many different common ways, including
   geography.

   At the MUD policy enforcement point - the firewall - there is a
   problem.  The firewall has only access to the layer-3 headers of the
   packet.  This includes the source and destination IP address, and if

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   not encrypted by IPsec, the destination UDP or TCP port number
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