Let 'localhost' be localhost.
draft-west-let-localhost-be-localhost-03

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DNSOP                                                            M. West
Internet-Draft                                               Google, Inc
Updates: 6761 (if approved)                            November 17, 2016
Intended status: Standards Track
Expires: May 21, 2017

                     Let 'localhost' be localhost.
                draft-west-let-localhost-be-localhost-03

Abstract

   This document updates RFC6761 by requiring that the domain
   "localhost." and any names falling within ".localhost." resolve to
   loopback addresses.  This would allow other specifications to join
   regular users in drawing the common-sense conclusions that
   "localhost" means "localhost", and doesn't resolve to somewhere else
   on the network.

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
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   This Internet-Draft will expire on May 21, 2017.

Copyright Notice

   Copyright (c) 2016 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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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and notation  . . . . . . . . . . . . . . . . . .   3
   3.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Implementation Considerations . . . . . . . . . . . . . . . .   4
     4.1.  Non-DNS usage of localhost names  . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Section 6.3 of [RFC6761] invites developers to "assume that IPv4 and
   IPv6 address queries for localhost names will always resolve to the
   respective IP loopback address".  That suggestion, unfortunately,
   doesn't match reality.  Client software is empowered to send
   localhost names to DNS resolvers, and resolvers are empowered to
   return unexpected results in various cases.  This has several
   impacts.

   One of the clearest is that the [SECURE-CONTEXTS] specification
   declines to treat "localhost" as "secure enough", as it might not
   actually be the "localhost" that developers are expecting.  This
   exclusion has (rightly) surprised some developers.

   Following on from that, the lack of confidence that "localhost"
   actually resolves to the loopback interface may encourage application
   developers to hard-code IP addresses, which causes problems in the
   transition from IPv4 to IPv6 (see problem 8 in
   [draft-ietf-sunset4-gapanalysis]).  [SECURE-CONTEXTS] excluding
   "localhost" would exacerbate this risk, giving developers positive
   encouragement to use the loopback address rather than a localhost
   name.

   This document suggests that we should resolve the confusion by
   requiring that DNS resolution work the way that users expect:
   "localhost" is the loopback interface on the local host.  Resolver
   APIs will resolve "localhost." and any names falling within
   ".localhost." to loopback addresses [RFC5735]

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