Network Reconnaissance in IPv6 Networks
RFC 7707

Document Type RFC - Informational (March 2016; No errata)
Obsoletes RFC 5157
Last updated 2016-03-09
Replaces draft-gont-opsec-ipv6-host-scanning
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Gunter Van de Velde
Shepherd write-up Show (last changed 2015-05-30)
IESG IESG state RFC 7707 (Informational)
Consensus Boilerplate Yes
Telechat date
Responsible AD Joel Jaeggli
Send notices to (None)
IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                           F. Gont
Request for Comments: 7707                           Huawei Technologies
Obsoletes: 5157                                                 T. Chown
Category: Informational                                             Jisc
ISSN: 2070-1721                                               March 2016

                Network Reconnaissance in IPv6 Networks

Abstract

   IPv6 offers a much larger address space than that of its IPv4
   counterpart.  An IPv6 subnet of size /64 can (in theory) accommodate
   approximately 1.844 * 10^19 hosts, thus resulting in a much lower
   host density (#hosts/#addresses) than is typical in IPv4 networks,
   where a site typically has 65,000 or fewer unique addresses.  As a
   result, it is widely assumed that it would take a tremendous effort
   to perform address-scanning attacks against IPv6 networks; therefore,
   IPv6 address-scanning attacks have been considered unfeasible.  This
   document formally obsoletes RFC 5157, which first discussed this
   assumption, by providing further analysis on how traditional address-
   scanning techniques apply to IPv6 networks and exploring some
   additional techniques that can be employed for IPv6 network
   reconnaissance.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7707.

Gont & Chown                  Informational                     [Page 1]
RFC 7707                   IPv6 Reconnaissance                March 2016

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
   Provisions Relating to IETF Documents
   (http://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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Requirements for the Applicability of Network Reconnaissance
       Techniques  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IPv6 Address Scanning . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Address Configuration in IPv6 . . . . . . . . . . . . . .   6
       4.1.1.  Stateless Address Autoconfiguration (SLAAC) . . . . .   6
       4.1.2.  Dynamic Host Configuration Protocol for IPv6 (DHCPv6)  11
       4.1.3.  Manually Configured Addresses . . . . . . . . . . . .  12
       4.1.4.  IPv6 Addresses Corresponding to
               Transition/Coexistence Technologies . . . . . . . . .  14
       4.1.5.  IPv6 Address Assignment in Real-World Network
               Scenarios . . . . . . . . . . . . . . . . . . . . . .  14
     4.2.  IPv6 Address Scanning of Remote Networks  . . . . . . . .  17
       4.2.1.  Reducing the Subnet ID Search Space . . . . . . . . .  18
     4.3.  IPv6 Address Scanning of Local Networks . . . . . . . . .  19
     4.4.  Existing IPv6 Address-Scanning Tools  . . . . . . . . . .  20
       4.4.1.  Remote IPv6 Network Address Scanners  . . . . . . . .  20
       4.4.2.  Local IPv6 Network Address Scanners . . . . . . . . .  21
     4.5.  Mitigations . . . . . . . . . . . . . . . . . . . . . . .  21
     4.6.  Conclusions . . . . . . . . . . . . . . . . . . . . . . .  22
   5.  Alternative Methods to Glean IPv6 Addresses . . . . . . . . .  23
     5.1.  Leveraging the Domain Name System (DNS) for Network
           Reconnaissance  . . . . . . . . . . . . . . . . . . . . .  23
       5.1.1.  DNS Advertised Hosts  . . . . . . . . . . . . . . . .  23
       5.1.2.  DNS Zone Transfers  . . . . . . . . . . . . . . . . .  23
       5.1.3.  DNS Brute Forcing . . . . . . . . . . . . . . . . . .  23
       5.1.4.  DNS Reverse Mappings  . . . . . . . . . . . . . . . .  24
     5.2.  Leveraging Local Name Resolution and Service Discovery
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