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Mobility for IP (MIPSHOP)                                      W. Haddad
Internet-Draft                                                M. Naslund
Intended status: Standards Track                                Ericsson
Expires: April 23, 2010                                 October 20, 2009


   On Using 'Symbiotic Relationship' to Repel Network Flooding Attack
                draft-haddad-mipshop-netflood-defense-03

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on April 23, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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Abstract

   This memo describes a simple defense mechanism against a specific
   type of network flooding attacks.  The suggested mechanism requires a
   mobile node to establish a 'symbiotic relationship' with the
   infrastructure, in order to empower it to repel such attack while
   giving enough insurance to the source(s) of the traffic about the
   need to cease sending traffic to the targeted network.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Protocol Overview  . . . . . . . . . . . . . . . . . . . . . .  6
   5.  New Messages and Options . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11





























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1.  Introduction

   Network flooding attacks aim to saturate the targeted network, e.g.,
   the access infrastructure, with junk packets in order to create an
   environment where all hosts located on a particular link(s) become
   victims to a denial-of service attack (DoS).

   As the name suggests, network flooding attacks targets a whole
   portion of the network infrastructure instead of targeting one
   particular node (e.g., SYN flooding attack) and thus, can have a more
   devastating effect.

   This memo describes a simple defense mechanism against a specific
   type of network flooding attacks.  The suggested mechanism requires a
   mobile (and potentially multihomed) host to establish a 'symbiotic
   relationship (SR)' as described in
   [I-D.haddad-csi-symbiotic-sendproxy], with the network infrastructure
   in order to empower it to repel such attack.  In order to be
   successful, the defense mechanism described as a "counter attack"
   mounted by the targeted infrastructure must provide enough insurance
   to the source(s) of harmful traffic about the need to cease sending
   packets towards the targeted network.





























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2.  Conventions used in this document

   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 [RFC2119].














































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3.  Motivation

   It is safe to assume that any practical defense against network
   flooding attacks does not need to be motivated!  However, we feel
   important to highlight how such attack can be mounted in a mobile
   and/or multihomed environment(s) and describe the current defense
   mechanism and its consequences on the mobile node (MN).

   A specific type of network flooding attack can be launched from using
   Mobile IPv6 protocol (described in [I-D.ietf-mext-rfc3775bis]).  Such
   attack is mounted by having the malicious MN attaching to the
   targeted network then updating each of its correspondent nodes (CNs)
   about its new care-of address (CoA) by sending binding updates (BU)
   messages.  Once the update(s) is done, each CN is supposed to start
   re-routing data packets to the MN's new CoA.  The next step for the
   attacker is to detach itself from the foreign link while keeping
   sending ACK messages to each CN via its home agent (HA).  Such step
   requires the MN to switch to another network or to use another
   interface in case it is multihomed.  However, the impact will be the
   same on the targeted network in both scenarios, since each CN will
   keep sending data packets to the MN's CoA as long as it keeps
   receiving ACK messages and the binding lifetime has not expired (for
   more details, refer to [RFC4225]).

   In MIPv6 protocol, the defense against the type of network flooding
   attack described in the above, is provided by repeating the return
   routability (RR) procedure every 7 minutes.  This means also that
   even if the MN is not moving, then it has to perform the HoTI/HoT and
   CoTI/CoT signaling exchange with each correspondent node (CN).  It
   follows that a significant amount of signaling messages can be
   imposed on the MN in some cases.

   Enhanced Mobile IPv6 (EMIPv6), described in [RFC4866], introduces a
   strong optimization to MIPv6 protocol by exploiting the crypto-
   generated address technique [RFC3972] for the purpose of establishing
   a long lifetime bidirectional security association (SA) between the
   MN and the CN.  However, while EMIPv6 succeeds in reducing the load
   of signaling messages, it does not provide strong defense against the
   type of network flooding attack described earlier.

   Our main motivation in this document is to provide an efficient and
   simpler mechanism, which enables the targeted (visited) network to
   repel network flooding attacks mounted by an attacker using mobility
   and multihoming protocols.







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4.  Protocol Overview

   In order to empower the network infrastructure to repel the type of
   network flooding attack described earlier, the suggested protocol
   puts a strong -yet neutral in its effect- requirement on any node
   attaching to the network access infrastructure.  The new requirement
   consists on establishing an SR with any public key(s) advertised by
   the access router (AR) in the router advertisement (RtAdv) messages.
   This is motivated by the fact that an AR may or may not be the
   node(s), which can launch a counter attack to repel the flooding
   attack.  Consequently, the AR has to advertise the public keys of
   other dedicated node(s), which has this feature.  It follows, that a
   main assumption in our protocol is to have the secure neighbor
   discovery [RFC3971] protocol deployed in the targeted infrastructure.
   For simplicity reasons, we assume in the following that the AR is the
   node able to carry counter attacks if/when needed.  This means that
   no additional public key(s) is advertised in the RtAdv messages.

   When configuring its IPv6 address, e.g., CoA, the MN MUST establish
   the SR and sends back the RAN(128) to the AR.  The MN SHOULD encrypt
   the RAN(128) with the AR's public key and the latter SHOULD NOT allow
   access to any node which does not establish an SR upon attachment to
   its corresponding link(s).  Upon receiving a neighbor discovery
   message [RFC4861] carrying the SR component, the AR should validate
   it before storing it in its cache memory.  Only after storing the SR
   in its cache memory and approving it in a signed NDP message, that a
   MN can trigger the exchange of mobility signaling messages with the
   CN(s), in order to request re-routing data traffic to its new CoA.

   Let's assume that after resuming data packets exchange using its new
   CGA, the MN (being malicious!) decides to mount the same type of
   network flooding attack against the visited network.  This means that
   once it has synchronized the transmission of ACK messages sent via
   other paths with data packets rates received from the CNs, it can
   detach itself from the foreign link and keep sending ACK messages to
   the CNs at the appropriate frequencies.

   After leaving the link, the AR will notice at some point (e.g., using
   NDP messages) that the MN has vanished while data packets are still
   routed to the MN's CoA.  At this stage, the AR MAY decide to act
   immediately or within a pre-configured time interval.  In both
   scenarios, the AR will launch its counter attack by fetching first
   all IP source address(es) carried in data packets sent to the MN's
   CoA, then sending a new mobility message (called "Flush Request
   (FR)") to each corresponding CN.  The FR message MUST carry the MN's
   CoA together with the SR corresponding "proof of relationship (PoR)"
   and MUST be signed with the AR's CGA private key.




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   Upon receiving a FR message, the CN validates it by checking first if
   the CoA is stored in its binding cache entries (BCE) table.  Then, it
   checks in the following order:

   - the SR PoR
   - the AR's CGA address
   - the signature

   If the FR message is valid, the CN MUST immediately flush out the
   MN's CoA from its BCE and tear down all ongoing sessions using the
   MN's IPv6 home address which is bind to the CoA carried in the FR
   message.  Then, the CN SHOULD send a "Flush Acknowledgment (FA)"
   message to the AR which MUST carry the token and the PoR.  Finally,
   the CN MUST also sign the FA message with its CGA private key.  In
   case any of the above validation steps fail, the CN SHOULD silently
   discard the message and keeps exchanging data packets with the MN.

   As mentioned earlier, the AR MUST send a FR message to each CN in
   order to completely stop the attack.  This means that the intensity
   of the flooding attack should gradually decrease gradually before it
   comes to a halt.






























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5.  New Messages and Options

   TBD
















































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6.  Security Considerations

   This document describes a defense mechanism against a specific type
   of network flooding attack which can be mounted by one or many
   malicious node(s) having to attach to the targeted network before
   triggering the attack.  Consequently, the main goal behind this
   document is to increase the overall network infrastructure security.
   It should be noted however, that the suggested defense mechanism
   looses its efficiency when the CN is also involved in the attack.

   A key feature in our mechanism is the SR between any host and the AR.
   However, such feature can easily be turned into a denial-of-service
   (DoS) attack against the host itself in case it accepts to establish
   an SR with any node whose claimed certificate cannot be verified.  It
   follows that a key requirement is to have SeND deployed in order to
   protect the link between the AR and the MN.  Note that in case the AR
   gets compromised then it can send at anytime an FR message to the CN
   to tear down the MN's ongoing session(s).  However, such scenario is
   no different than having the AR dropping data packets sent to the MN.

   Finally, it should be noted that the AR is not taking any step in
   order to protect the CN against attacks which aim to exhaust its
   processing power by flooding it with fake FR messages.  In fact,
   there are three reasons for not imposing a preventive step, e.g., a
   CoTI/CoT message exchange.  First, the CN is able to check the SR
   before it validates the signature.  This means that the CN will drop
   the message in case the SR is not valid.  The second reason is that
   the RAN(128) parameter is sent in an encrypted form to the AR only.
   Consequently, prior to sending an FR message, the SR is known only by
   the MN and its AR.  The third one is the fact that after sending a FR
   message, the MN's CoA won't be used anymore so disclosing it in a FR
   message should not introduce any new threat against the CN.



















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7.  References

7.1.  Normative References

   [I-D.ietf-mext-rfc3775bis]
              Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", draft-ietf-mext-rfc3775bis-04 (work in
              progress), July 2009.

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

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
              Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

   [RFC4225]  Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
              Nordmark, "Mobile IP Version 6 Route Optimization Security
              Design Background", RFC 4225, December 2005.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4866]  Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
              Optimization for Mobile IPv6", RFC 4866, May 2007.

7.2.  Informative References

   [I-D.haddad-csi-symbiotic-sendproxy]
              Haddad, W. and M. Naslund, "On Secure Neighbor Discovery
              Proxying Using 'Symbiotic' Relationship",
              draft-haddad-csi-symbiotic-sendproxy-01 (work in
              progress), July 2009.















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Authors' Addresses

   Wassim Michel Haddad
   Ericsson
   6210 Spine Road
   Boulder, CO  80301
   US

   Phone: +1 303 473 6963
   Email: Wassim.Haddad@ericsson.com


   Mats Naslund
   Ericsson
   Torshamnsgatan 23
   SE-164 80 Stockholm
   Sweden

   Phone: +46 8 58533739
   Email: Mats.Naslund@ericsson.com































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