Least-Common Scope Communications
draft-mudric-6man-lcs-02

Document Type Active Internet-Draft (individual)
Authors Dusan Mudric  , Alexandre Petrescu 
Last updated 2020-11-14
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6MAN Working Group                                             D. Mudric
Internet-Draft                                                     Ciena
Updates: RFC5014, RFC6724 (if approved)                      A. Petrescu
Intended status: Standards Track                               CEA, LIST
Expires: May 18, 2021                                  November 14, 2020

                   Least-Common Scope Communications
                        draft-mudric-6man-lcs-02

Abstract

   This draft formulates a security problem statement.  The problem
   arises when a Host uses its Global Unicast Address (GUA) to
   communicate with another Host situated on the same link.

   To address this problem, we suggest to select and use addresses of a
   least scope that are common.

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
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   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 18, 2021.

Copyright Notice

   Copyright (c) 2020 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
   carefully, as they describe your rights and restrictions with respect
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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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Least Common Scope Communications . . . . . . . . . . . . . .   3
   4.  LL Address Resolution . . . . . . . . . . . . . . . . . . . .   3
   5.  Sending algorithm with LL Address . . . . . . . . . . . . . .   7
   6.  Other Issues with LL Address Resolution . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  ChangeLog  . . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Problem Statement

   Sockets listening on a global addresses are exposed to attacks.
   RFC6724 Rule 8 selects a candidate address with the smallest scope.
   Applications don't always have LL candidate address.  They usually
   have a GUA address.  If GUA is on a local link, an application will
   open a socket using GUA.  To avoid using GUA on the local link, a
   sender needs to find a destination LL address.  Currently SASA
   algorithm (RFC 6724 "Default Address Selection for Internet Protocol
   Version 6 (IPv6)") cannot use the smallest common scope, given
   destination GUA.

   For security reasons, hosts should use an address with the smallest
   scope.  To avoid these attacks, the host should use LL or ULA
   addresses.

   These security reasons, in more detail, are described next.  There is
   a security problem when a Host uses (one of) its Global Unicast
   Address(es) (GUA) to communicate to another Host situated on the same
   link.  The problem appears even if that second Host uses its link-
   local address (LL) for this communication.

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   The problem is that the Host that uses the GUA to actively
   communicate with another Host situated on the same link opens a
   globally reachable entry point in its operating system kernel.  This
   entry point appears when the GUA is assigned to a socket structure.
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