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Network Working Group                                             W. Liu
Internet-Draft                                       Huawei Technologies
Intended status: Informational                                   F. Gont
Expires: July 5, 2014                             SI6 Networks / UTN-FRH
                                                                 T. Tsou
                                               Huawei Technologies (USA)
                                                         January 1, 2014


                            DS-lite security
                  draft-liu-opsec-ds-lite-security-00

Abstract

   More and more operators have deployed or are about to deploy IPv6
   transition technologies such as DS-lite, MAP, LAFT6, etc.  The
   fundamental elements of these technologies are Network Address
   Translation (NAT) and Tunneling.  The elements of these transition
   technologies may be subject to a number of attacks, unless
   appropriate mitigations are in place.  This memo discusses the
   security implications of the aforementioned points, and additionally,
   provides a number of operational mitigations that could be deployed
   against these attacks.

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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   This Internet-Draft will expire on July 5, 2014.

Copyright Notice

   Copyright (c) 2014 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



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   (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
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  DHCPv6-based attacks  . . . . . . . . . . . . . . . . . . . . . 4
   4.  IPv6 fragmentation  . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Attacks against the AFTR/CPE //neet to reorganize the arch  . . 4
   6.  Attacks based on encapsulation/decapsulation  . . . . . . . . . 5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6






























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1.  Introduction

   Due to the world-wide IPv4 address exhaustion, more and more
   operators have deployed or are about to deploy IPv6 transition
   technologies such as DS-lite, MAP, LAFT6, etc.  The fundamental
   elements of these technologies are Network Address Translation (NAT)
   and Tunneling.  The traffic traversing a NAT or Tunneling function
   may be under attack due to the lack of protection on the node where
   the NAT or/and Tunneling is placed.  In addition, the node conducting
   the function of NAT or/and Tunneling may also be the victim of DDOS
   attack.  This memo discusses the security implications of the
   aforementioned points, and additionally, provides a number of
   operational mitigations that could be deployed against these attacks.

   Dual-Stack Lite (DS-Lite) technology, which enables a broadband
   service provider to share IPv4 addresses among customers by combining
   two well-known technologies: IP in IP (IPv4- in-IPv6) and Network
   Address Translation (NAT), was proposed aiming at better aligning the
   costs and benefits of deploying IPv6 in service provider networks.
   [RFC6333] A typical DS-Lite deployment is shown in the figure below.
   the Dual-Stack Lite model is built on to cross the network to reach a
   carrier-grade IPv4-IPv4 NAT (the AFTR), where customers will share
   IPv4 addresses.  A IPv4-in-IPv6 tunnel(DS-Lite Tunnel) is built from
   Bridging BroadBand (B4) element crossing the network to reach a DS-
   Lite Address Family Transition Router (AFTR) element, where a
   carrier-grade IPv4-IPv4 NAT is implemented.  In such an end to end
   DS-Lite deployment, there are several points that are vulnerable and
   will be discussed in the rest of this document.


                        ------                        ------
                     //        \\    +--------+    //        \\
  +---+   +--+   |   IPv6     |   |  BRAS  |   |    IPv4    |   +------+
  |Cli|-->|B4|-->+  network   +-->+  with  +-->+   network  +-->|Server|
  +---+   +--+   |            |   |  AFTR  |   |            |   +------+
                     \\        //    +--------+    \\        //
                        ------                        ------

                      DS-Lite Tunnel
            +--------------------------+

                       Figure 1: DS-Lite deployment


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this



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   document are to be interpreted as described in [RFC2119].


3.  DHCPv6-based attacks

   In DS-Lite, DHCPv6 [RFC3115] is used to assign address for CPE, so
   DHCPv6 can be exploited as an attack vector.  The following aspects
   should be considered:

   1.  Authentication between client and server.

      a) Rogue/malicious DHCP server: A rogue server may allocate fake
      IP address to the client requesting address and causes the client
      unable to communicate.  This has been well discussed in
      draft-ietf-opsec-dhcpv6-shield.

      b) Rogue/malicious client: A rogue client may make DoS attacks by
      following two ways:

         i)Using up all the resources of DHCP server.  A client may
         unremittingly send forged DHCP requests to DHCP server to use
         up the resources of DHCP server.

         ii)Dos attack other client by forging its IP address.  A
         malicious client may unremittingly send forged DHCP requests to
         cause it unable to communicate.

   We note that these attacks are not different than in the typical home
   network case where a DHCPv6 server is employed.


4.  IPv6 fragmentation

   Since the encapsulation of IPv4 traffic in IPv6 may rely on the use
   of IPv6 fragmentation, DS-lite may be subject to fragmentation-based
   attacks.

   Operational mitigation: Limit resources used by per client and/or
   globally.


5.  Attacks against the AFTR/CPE //neet to reorganize the arch

   1.  Forge tunnel source addresses of CPE(B4).  An attacker may forge
   many IPv6 addresses as DS-lite tunnel source addresses and create
   many tunnels, and/or entries in the NAT state table with AFTR,
   causing a DoS attack to the CGN(AFTR).




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   +---------+    +----------+    +----------+
   + Host    +----+ CPE1(B4) +----+ CGN(AFTR)+---------- Internet
   +---------+    +----------+    +-----+----+
                                        |
   +---------+    +----------+          |
   +Attacker +----+ CPE2(B4) +----------+
   +---------+    +----------+

            Figure 2: Forge tunnel source addresses of CPE(B4)

   As shown in Figure 2, the attacker can cause a DoS attack to the
   CGN(AFTR) by creating tunnels on CPE2(B4), and/or entries in the NAT
   state table with the CGN(AFTR).

   2.  Forge CPE's address.  One or many hackers may forge IPv6
   addresses of CPEs of other users and send lots of packets to
   CGN(AFTR).  After receiving too many such packets, the CNG(AFTR) may
   deny the further request from those victim CPEs whose addresses are
   forged.

   Take Figure 2 as an example, Attacker may make CPE2(B4) to forge the
   address of CPE1 and start an attack.  With too many packets from with
   the v6 address of CPE1 received, the CGN might deny the service of
   CPE1.

   3.  Session attack.  An attacker may create many sessions at the same
   time within one tunnel.  This may cause a DoS attack that other user
   can hardly create sessions due to resource excessive occupancy.

   4.  Big header attack.  An attacker forges DS-lite packet with
   multiple Next Headers in IP header to cause an excessive occupancy of
   the CPU resource.

   Operational mitigation: Limit on the number of sessions per client
   and globally.  Limit on the rate of building sessions to avoid the
   memory being used up.  Limit on the number of next headers of packet
   to avoid the CPU resource being used up.


6.  Attacks based on encapsulation/decapsulation

   Not sure about this one.  Could you please write more about this?
   Thanks.

   e.g.  Can clients leverage DS-LITE to spoof the sure address? [fgont]
   Yes Can clients diretly acess themselves with DS-list (to avoid being
   monitored)? [fgont] This would be another possible one. [fgont] You
   might find this reference useful: RFC 6169



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7.  Security Considerations

   N/A.


8.  Acknowledgements

   N/A.


9.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.


Authors' Addresses

   Will(Shucheng) Liu
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   P.R. China

   Email: liushucheng@huawei.com


   Fernando Gont
   SI6 Networks / UTN-FRH
   Evaristo Carriego 2644
   Haedo, Provincia de Buenos Aires  1706
   Argentina

   Phone: +54 11 4650 8472
   Email: fgont@si6networks.com
   URI:   http://www.si6networks.com







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   Tina Tsou
   Huawei Technologies (USA)
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Phone: +1 408 330 4424
   Email: tina.tsou.zouting@huawei.com











































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