One document matched: draft-dupont-mipv6-rrcookie-01.txt

Differences from draft-dupont-mipv6-rrcookie-00.txt

Network Working Group                                          F. Dupont
Internet-Draft                                                    Point6
Expires: December 25, 2005                                   J-M. Combes
                                                     France Telecom DR&D
                                                           June 23, 2005


          Care-of Address Test for MIPv6 using a State Cookie
                   draft-dupont-mipv6-rrcookie-01.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document defines a procedure which performs a "care-of address
   test" using a state cookie for routing optimization in Mobile IPv6
   not protected by the routing routability procedure, i.e., protected
   by some alternative mechanisms like pre-shared secret or pre-
   established IPsec security associations.





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1.  Introduction

   The Mobile IPv6 specifications [RFC3775] defines a default protection
   for routing optimization, the routing routability procedure, which
   includes an explicit "care-of address test".  Alternative protection
   mechanisms like pre-shared secret [pcfgkbm] or pre-established IPsec
   security associations [CNIPsec] are more efficient and secure but
   require in some cases a care-of address test to avoid a "3rd party
   bombing" vulnerability.

   This document proposes a care-of address test procedure at the
   initiative of the correspondent node using a state cookie as in SCTP
   [RFC2960] or IKEv2 [IKEv2].

2.  Keywords

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119].

3.  A signaling extension for a care-of address test using a state
    cookie

3.1  Applicability

   The care-of address test procedure defined by this document MAY be
   used in order to check whether the mobile node can really receive
   packets sent to the care-of address of a new binding update.  It
   SHOULD NOT be used for entry deletion, i.e., when the care-of address
   is the home address.  It MUST be used for real alternate care-of
   address, i.e., when the address carried by an alternate care-of
   address option is not the source address of the IP header nor the
   home address of the mobile node (following the recommendation of
   [bombing]).

3.2  Protocol

   The procedure is based on the state cookie idea of SCTP [RFC2960]
   which can be found again in IKEv2 proposal [IKEv2].  The binding
   update is in a first time (1) rejected by a binding acknowledgment
   with a new dedicated status and a cookie option sent to the tested
   care-of address.  Upon the reception (2) of this binding
   acknowledgment, the mobile node retransmits (3) the binding update
   with the exact received cookie placed in a cookie option.  When the
   correspondent node receives (4) the augmented binding update, it can
   check by recomputing the cookie and comparing it to the cookie option
   data that the binding update is from the same mobile node and for the



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   same care-of address (so it can infer the mobile node is reachable at
   this care-of address, i.e., a "care-of address test" has been
   successfully performed).

   The cookie MUST reflect the mobile node identity or the binding cache
   entry or an equivalent, and MUST reflect the tested care-of address.
   It MUST NOT be easy to infer by the mobile node, including with the
   knowledge of previous cookies from the same node.

   The last point is what to do waiting the retransmitted and augmented
   binding update.  Possibilities are:
   -  apply the binding update with the new care-of address.  It defeats
      the purpose of the care-of address test so it SHOULD NOT be done,
      and it MUST NOT be done for a real alternate care-of address.
   -  keep the previous care-of address.  As it is not possible to know
      whether the previous care-of address is still usable, i.e.,
      whether the mobile node is still reachable at this previous
      care-of address, the default policy SHOULD NOT be to keep the
      previous care-of address.  The correspondent node MAY keep the
      previous care-of address in special cases where this is known to
      be the best solution.
   -  temporarily disable the binding cache entry, i.e., by using the
      home address for communication to the mobile node until another
      binding update is received.  This SHOULD be the default policy.

3.3  Cookie Generation Example

   This method assumes a global secret key is available and uses in
   sequence:
   -  a 16 bit timestamp of when the cookie is created
   -  the tested care-of address
   -  the truncated HMAC [RFC2104], keyed by a secret key, of the
      preceding two fields, the home address and the correspondent
      address.
   The secret key SHOULD be random or pseudo-random and SHOULD be
   changed reasonably frequently.  The timestamp MAY be used to
   determine which key was used.  The HMAC has to be truncated in order
   to keep the cookie option length less than the maximum, the higher 96
   bits of the HMAC should be enough.

4.  Acknowledgments

   This document was extracted from [CNIPsec] because what it provides
   is needed by any alternative to the return routability procedure
   which has no built-in care-of address test.






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5.  Security Considerations

   Without a test of the care-of address or an other way to trust it,
   the care-of address presented by the mobile node can be a fake one
   and offers a 3rd party bombing attack.

   Binding updates and acknowledgments are validated using an
   alternative protection mechanisms so they can't be injected by third
   parties.  The cookie sub-option is small enough to make this
   procedure a poor candidate for a third party bombing mechanism.

6.  IANA Considerations

   This document requires:
   -  a new status for binding acknowledgment.
   -  a new option for mobility messages used in binding update and
      acknowledgment messages.

7.  References

7.1  Normative References

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104, March 1997.

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

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

7.2  Informative References

   [CNIPsec]  Dupont, F. and J-M. Combes, "Using IPsec between Mobile
              and Correspondent IPv6 Nodes",
              draft-ietf-mip6-cn-ipsec-01.txt (work in progress),
              June 2005.

   [IKEv2]    Kaufman, C., Ed., "Internet Key Exchange (IKEv2)
              Protocol", draft-ietf-ipsec-ikev2-17.txt (work in
              progress), September 2004.

   [RFC2960]  Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
              Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
              Zhang, L., and V. Paxson, "Stream Control Transmission
              Protocol", RFC 2960, October 2000.

   [bombing]  Dupont, F., "A note about 3rd party bombing in Mobile



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              IPv6", draft-dupont-mipv6-3bombing-02.txt (work in
              progress), June 2005.

   [pcfgkbm]  Perkins, C., "Preconfigured Binding Management Keys for
              Mobile IPv6", draft-ietf-mip6-precfgkbm-02.txt (work in
              progress), May 2005.


Authors' Addresses

   Francis Dupont
   Point6
   c/o GET/ENST Bretagne
   2 rue de la Chataigneraie
   CS 17607
   35576 Cesson-Sevigne Cedex
   France

   Fax:   +33 2 99 12 70 30
   Email: Francis.Dupont@enst-bretagne.fr


   Jean-Michel Combes
   France Telecom DR&D
   38/40 rue du General Leclerc
   92794 Issy-les-Moulineaux Cedex 9
   France

   Fax:   +33 1 45 29 65 19
   Email: jeanmichel.combes@francetelecom.com





















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