[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-ohba-6lo-mle-hip-dex) 00 01

Network Working Group                                       Y. Ohba, Ed.
Internet-Draft                                                   Toshiba
Intended status: Experimental                             April 19, 2016
Expires: October 21, 2016


An Extension to Mesh Link Establishment (MLE) for Host Identity Protocol
                        Diet Exchange (HIP DEX)
                     draft-ietf-6lo-mle-hip-dex-01

Abstract

   HIP DEX (Host Identity Protocol Diet EXchange) is a light-weight key
   exchange protocol designed for constrained devices.  MLE (Mesh Link
   Establishment) is defined for establishing and configuring secure
   links in IEEE 802.15.4 mesh networks.  This document defines an
   extension of MLE protocol to encapsulate HIP DEX key exchange
   protocol messages.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://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 October 21, 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



Ohba                    Expires October 21, 2016                [Page 1]


Internet-Draft              HIP DEX over MLE                  April 2016


   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirement Language  . . . . . . . . . . . . . . . . . .   3
     1.2.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Convention  . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Key Establishment Phase . . . . . . . . . . . . . . . . . . .   4
   4.  Key Update Phase  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Key Materials . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Pair-wise Key . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Group Keys  . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  MLE Security  . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Certificate Revocation  . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  MLE TLV Types . . . . . . . . . . . . . . . . . . . . . .  10
     9.2.  HIP Parameter . . . . . . . . . . . . . . . . . . . . . .  10
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     11.2.  External Informative References  . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   HIP DEX (Host Identity Protocol Diet EXchange) [I-D.ietf-hip-dex] is
   a light-weight key exchange protocol designed for constrained
   devices.  HIP DEX builds on the HIP Base EXchange (HIP BEX)
   [I-D.ietf-hip-rfc5201-bis] and inherits the transport-agnostic
   property of HIP BEX.

   MLE (Mesh Link Establishment) [I-D.ietf-6lo-mesh-link-establishment]
   is defined for establishing and configuring secure links in IEEE
   802.15.4 mesh networks.  MLE assumes that shared keys to secure link-
   layer frames and MLE messages exchanged between a pair of nodes are
   pre-configured between the nodes.  Therefore, a key exchange protocol
   is required in order to dynamically configure the required shared
   keys.  While such a key exchange protocol can be run outside MLE,
   sequentially running a key exchange protocol and MLE as separate
   protocols requires more message roundtrips.  For example, running a
   HIP DEX 4-way handshake followed by an MLE 3-way handshake requires
   3.5 message roundtrips.





Ohba                    Expires October 21, 2016                [Page 2]


Internet-Draft              HIP DEX over MLE                  April 2016


   In this document, an extension to the MLE protocol for encapsulating
   HIP DEX messages is defined in order to realize optimized key
   exchange and link establishment for IEEE 802.15.4 mesh networks.

1.1.  Requirement Language

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

1.2.  Acronyms

   DEX-I1, DEX-R1, DEX-I2, DEX-R2: HIP DEX I1, R1, I2, R2 messages

   ECDH: Elliptic Curve Diffie-Hellman

   EI: HIP DEX Key Establishment Initiator

   ER: HIP DEX Key Establishment Responder

   LLFC: Link-Layer Frame Counter

   MIC: MLE Message Integrity Code

   MLFC: MLE Frame Counter

   UI: HIP DEX Key Update Initiator

   UR: HIP DEX Key Update Responder

1.3.  Convention

   In the figures of this document, MLE messages marked with '*' are
   those secured by the MLE protocol.

   In the key material formats in this document, '|' denotes
   concatenation operator.

2.  Overview

   HIP DEX over MLE consists of two phases, i.e., Key Establishment
   Phase and Key Update Phase.  In Key Establishment Phase, a HIP DEX
   4-way handshake using I1, R1, I2 and R2 messages is conducted to
   establish a secure channel between an EI and an ER based on an ECDH
   shared secret and exchange session key materials over the secure
   channel.




Ohba                    Expires October 21, 2016                [Page 3]


Internet-Draft              HIP DEX over MLE                  April 2016


   In Key Update Phase, HIP DEX Update messages encrypting session key
   materials are exchanged between a UI and each UR using an MLE Update
   Request and Update exchange, followed by a multicast MLE Update
   message for triggering each UR to simultaneously activate new key
   materials and reset the associated link-layer frame counters.  The UI
   and UR roles for a pair of nodes may be determined independently of
   the EI and ER roles that have been taken by the nodes.

   All MLE messages used for the extension defined in this document
   SHOULD NOT be protected by link-layer so that a key exchange can be
   done regardless of the security state of the link-layer.  A node that
   implements this specification MUST allow sending and receiving MLE
   messages not secured by the link-layer.

   Secured 802.15.4 MAC frames and MLE messages that use keys
   established via HIP DEX MUST use a 5-octet Frame Counter.  An MLE
   Frame Counter is always carried in the Frame Counter field in the Aux
   Header of any secured MLE frame.  Note that [IEEE802154e] supports
   5-octet MAC Frame Counter for CSMA (Carrier Sense Multiple Access)
   and uses 5-octet ASN (Absolute Slot Number) as MAC Frame Counter for
   TSCH (Time-Slotted Channel Hopping) MAC.

   Other than the rules described in this document, the rules defined in
   [I-D.ietf-6lo-mesh-link-establishment] are preserved.

3.  Key Establishment Phase

   A message exchange diagram for Key Establishment Phase is shown in
   Figure 1.

  (EI)  (ER)
     -->    Advertisement [HIP{DEX-I1}, Link Quality]

     <--    Advertisement [HIP{DEX-R1}, Link Quality]

     -->    Link Request  [HIP{DEX-I2}, Source Address, Mode,
                           Timeout, Challenge]*

     <--    Link Accept and Request
                          [HIP{DEX-R2}, LLFC, MLFC, Source Address, Mode,
                           Timeout, Response, Challenge]*

     -->    Link Accept   [LLFC, MLFC, Response]*

                     Figure 1: Key Establishment Phase






Ohba                    Expires October 21, 2016                [Page 4]


Internet-Draft              HIP DEX over MLE                  April 2016


   An EI sends an MLE Advertisement message containing a HIP TLV and a
   Link Quality TLV to an ER.  The HIP TLV carries a DEX-I1 packet.  How
   an EI discovers an ER is outside the scope of this document.

   The ER receives the MLE Advertisement message containing a DEX-I1
   packet from the EI and sends an MLE Advertisement message containing
   a HIP TLV and a Link Quality TLV to the EI.  The HIP TLV carries a
   DEX-R1 packet.  The DEX-R1 packet MUST contain mandatory R1
   parameters specified in [I-D.ietf-hip-dex].  The DEX-R1 packet MAY
   contain optional R1 parameters specified in [I-D.ietf-hip-dex] and a
   CERT parameter defined in [RFC6253].

   The EI receives the MLE Advertisement message from the ER and sends a
   secured MLE Link Request message containing HIP, Source Address,
   Mode, Timeout and Challenge TLVs to the ER.  The HIP TLV carries a
   DEX-I2 packet.  The DEX-I2 packet MUST contain mandatory I2
   parameters specified in [I-D.ietf-hip-dex] including an ENCRYPTED_KEY
   parameter wrapping a session key material of the EI.  The DEX-I2
   packet MUST also contain an ENCRYPTED parameter wrapping group key
   materials of the EI.  The DEX-I2 packet MAY contain optional I2
   parameters specified in [I-D.ietf-hip-dex] and a CERT parameter
   defined in [RFC6253].  The MLE Link Request message is protected by
   the EI's group MLE key (see section Section 5.2) derived from the
   EI's group key materials.

   The ER receives the MLE Link Request message from the EI and extracts
   the EI's session key material wrapped in the ENCRYPTED_KEY parameter
   and the EI's group key materials wrapped in the ENCRYPTED parameter.
   Then the ER sends a secured MLE Link Accept and Request message
   containing HIP, LLFC, MLFC, Source Address, Mode Timeout, Response
   and Challenge TLVs to the EI.  The HIP TLV carries a DEX-R2 packet.
   The DEX-R2 packet MUST contain R2 parameters specified in
   [I-D.ietf-hip-dex] including an ENCRYPTED_KEY parameter wrapping a
   session key material of the ER.  The DEX-R2 packet MUST also contain
   an ENCRYPTED parameter wrapping group key materials of the ER.  The
   DEX-R2 packet MAY contain optional R2 parameters specified in
   [I-D.ietf-hip-dex].  Note that the MIC field of the MLE Link Request
   message is verified after the ER successfully extracts the EI's group
   key materials.

   The EI receives the MLE Link Accept and Request message from the ER
   and extracts the ER's session key material wrapped in the
   ENCRYPTED_KEY parameter and the ER's group key materials wrapped in
   the ENCRYPTED parameter.  Then the EI sends a secured MLE Link Accept
   message containing LLFC TLV, MLFC and Response TLVs to the ER.  If a
   pair-wise key is used by the link-layer, the EI also creates a Pair-
   wise Key SA with the session key generated by the pair of session key
   materials of the EI and ER as specified in [I-D.ietf-hip-dex].  Note



Ohba                    Expires October 21, 2016                [Page 5]


Internet-Draft              HIP DEX over MLE                  April 2016


   that the MIC field of the MLE Link Accept and Request message is
   verified after the EI successfully extracts the ER's group key
   materials.

   The ER receives the MLE Link Accept message from the EI.  If a pair-
   wise key is used by the link-layer, the EI creates a Pair-wise Key SA
   with the session key generated by the pair of session key materials
   of the EI and ER as specified in [I-D.ietf-hip-dex].

   In addition to initial key establishment time, Key Establishment
   Phase is also entered when an outgoing MAC Frame Counter or an
   outgoing MLE Frame Counter of a node reaches its maximum value (this
   is almost unlikely to happen with 5-octet Frame Counter, though).  In
   this case, the node MUST first update its HIP-DEX certificate before
   re-entering Key Establishment Phase.  How a HIP-DEX certificate is
   updated is out of the scope of this document.

4.  Key Update Phase

   In Key Update Phase, group key materials are updated.

   A Key Update Phase is invoked when a peer node that shares the group
   key is revoked.  Both link-layer Frame Counters and MLE Frame
   Counters are not reset in the Key Update Phase.  A message exchange
   diagram for group key update is shown in Figure 2.

    (UI) (UR1)..(URn)
                     // Update 1st peer
      ---->          Update Request [HIP{UPDATE}, MLFC, Source Address]*
      <----          Update [HIP{UPDATE}, MLFC, Source Address]*
           ..                       ..

                     // Update n-th peer
      ----------->   Update Request [HIP{UPDATE}, MLFC, Source Address]*
      <-----------   Update [HIP{UPDATE}, MLFC, Source Address]*

                     // Key switch notification (multicast)
      ----> .. -->   Update [LLFC, MLFC]*

                        Figure 2: Group Key Update

   First, a UI performs the following exchange for each UR:

   o  The UI sends an MLE Update Request message containing HIP, MLFC,
      Source Address and MIC TLVs to a UR.  The HIP TLV carries a HIP
      UPDATE packet containing SEQ, HIP_MAC and ENCRYPTED parameters.
      The ENCRYPTED parameter wraps new group key materials of the UI.




Ohba                    Expires October 21, 2016                [Page 6]


Internet-Draft              HIP DEX over MLE                  April 2016


   o  The UR receives the MLE Update Request message from the UI,
      extracts UI's new group key materials from the ENCRYPTED
      parameter, activates the UI's new group key materials for incoming
      frames, and sends an MLE Update message containing HIP, MLFC and
      Source Address TLVs, where the HIP TLV carries a HIP UPDATE packet
      containing ACK and HIP_MAC parameters.  Note that the MIC field of
      the MLE Update message is verified after the UR successfully
      extracts the UI's new group key materials.

   Once MLE Update Request and Update exchange is completed for all URs,
   the UI activates the UI's new group key materials for outgoing frames
   by multicasting an MLE Update message containing LLFC and MLFC TLVs.
   The MLE Update message is protected by the UI's group MLE key (see
   section Section 5.2) derived from the UI's new group key materials.

   When a UR receives the multicast MLE Update message, If the received
   message is valid, the UR deactivates the UI's old group key materials
   for incoming frames.

   A UR that did not receive the multicast MLE Update message may
   deactivate the UI's old group key materials for incoming frames when
   it receives a valid MAC frame protected by the link-layer key derived
   from the UI's new group key materials.

5.  Key Materials

5.1.  Pair-wise Key

   The first 16 octets of the session key corresponding to the HIP DEX
   Pair-wise SA [I-D.ietf-hip-dex] is used as the pairwise link-layer
   key used for securing unicast link-layer frames with Key Identifier
   Mode 0x00.

   An encrypted session key material is contained in an ENCRYPTED_KEY
   parameter of HIP when the session key is distributed during Key
   Establishment Phase.

5.2.  Group Keys

   Group key materials are created by a node and distributed to peer
   nodes.

   The group key materials consist of a 1-octet key identifier (KeyId)
   and a 16-octet group master key (GroupMasterKey), and encoded as
   follows:

   Group Key Materials = KeyId | GroupMasterKey




Ohba                    Expires October 21, 2016                [Page 7]


Internet-Draft              HIP DEX over MLE                  April 2016


   A 16-octet group link-layer key (GroupL2Key), and a 16-octet group
   MLE key (GroupMLEKey) are derived from GroupMasterKey as follows:

   GroupL2Key = The first 16-octet of HMAC_SHA256(GroupMasterKey,
   KeyId).

   GroupMLEKey = The last 16-octet of HMAC_SHA256(GroupMasterKey,
   KeyId).

   A GroupL2Key is used for securing link-layer frames with Key
   Identifier Mode 0x03 sent by the node that created the group key
   material.  GroupL2Key MUST be used for securing broadcast link-layer
   frames and MAY also be used for securing unicast link-layer frames.

   A GroupMLEKey MUST be used for securing MLE messages with Key
   Identifier Mode 0x03 sent by the node that created the group key
   material.

   The group key materials are contained in an GROUP_KEY_MATERIALS
   parameter of HIP, where the GROUP_KEY_MATERIALS parameter MUST be
   encrypted in an ENCRYPTED parameter of HIP.

6.  MLE Security

   As described in [I-D.ietf-6lo-mesh-link-establishment], MLE security
   reuses that of IEEE 802.15.4, i.e., AES-CCM* [IEEE802154].  Since
   some of the MLE messages (i.e., MLE Link Accept and Request and MLE
   Accept messages carrying DEX-I2 and DEX-R2 packets, respectively, and
   unicast MLE Update Request and Update messages carrying a DEX-UPDATE
   packet) require to be sent unencrypted and only authentication is
   needed, MIC-64 (Security Level 2) or MIC-128 (Security Level 3) is
   used to secure MLE messages.  MIC-64 is the default security level
   for securing MLE messages used in this document.  GroupMLEKey (see
   section Section 5.2) with Key Identifier Mode 0x03 and a 5-octet
   Frame Counter MUST be used for any secured MLE message.

7.  Certificate Revocation

   Any MLE message used in this document MAY also contain a CRL
   (Certificate Revocation List) TLV in which CertificateList defined in
   [RFC5280] is encoded in the Value field.  A complete CRL or a delta
   CRL is contained in a CRL TLV.  A node that receives a valid MLE
   message containing a CRL TLV revokes certificates specified in the
   TLV and deletes all pair-wise and group keys associated with the
   revoked certificates.  A node MUST reject a CERT parameter for a
   revoked certificate in Key Establishment Phase.





Ohba                    Expires October 21, 2016                [Page 8]


Internet-Draft              HIP DEX over MLE                  April 2016


   When a CRL TLV is carried in a multicast Update message and forwarded
   multiple hops, MPL [RFC7731] MAY be used.  In this case, the
   multicast Update message MUST be secured at the link layer and MUST
   NOT be secured by MLE as specified in
   [I-D.ietf-6lo-mesh-link-establishment].  Detailed MPL parameters for
   the multicast-based CRL distribution are out of the scope of this
   document.

   In order to reduce the size of a CRL, there are several guidelines.
   A delta CRL should be used whenever applicable.  Expired certificates
   should be excluded from a CRL.  A short lived (e.g., one month)
   certificate may be used (at the cost of increased frequency of
   certificate updates).  Hierarchically formed CAs may be used where
   each CA is expected to sign only a small number of certificates.

8.  Security Considerations

   The MLE extension defined in this document uses HIP DEX for key
   management of computation or memory constrained sensor/actuator
   devices, and thus it inherits all security considerations made for
   HIP DEX [I-D.ietf-hip-dex].

   In order to mitigate security weakness caused by lack of Perfect
   Forward Secrecy (PFS) in HIP DEX, it is RECOMMENDED to use this MLE
   extension in conjunction with an additional mechanism to update
   public/private key pairs and renew HIP DEX SAs using new public/
   private key pairs whenever necessary.

   In both Key Establishment Phase and Key Update Phase, MLE messages
   are secured using a group key instead of a pairwise key in order to
   optimize message roundtrips since a group key establishment requires
   only a half roundtrip.  As a result, a Denial of Service (DoS) attack
   from an insider sharing the group key is possible over MLE TLVs.

   Due to integration of HIP DEX into MLE, secured MLE messages are
   authenticated but not encrypted because decryption can be done only
   after establishing a key.  As a result, Source Address, Mode,
   Timeout, Challenge, Response LLFC and MLFC TLVs are sent in clear,
   and the cleartext information may be used by attackers for the DoS
   attack described above.  Note that authentication of the MLE message
   carrying a DEX-I2, DEX-R2 or DEX-UPDATE packet is possible by
   validating MIC of the MLE message after extracting the authentication
   key (i.e., GroupMLEKey) from the HIP DEX packet.








Ohba                    Expires October 21, 2016                [Page 9]


Internet-Draft              HIP DEX over MLE                  April 2016


9.  IANA Considerations

9.1.  MLE TLV Types

   The following MLE TLV types are to be assigned by IANA based on the
   policy described in [I-D.ietf-6lo-mesh-link-establishment]:

   o  HIP-DEX (Value: 9, Length: Variable, Meaning: HIP DEX packet,
      Reference: this document).

   o  CRL (Value: 10, Length: Variable, Meaning: Certificate Revocation
      List, Reference: this document).

9.2.  HIP Parameter

   The following HIP Parameter is assigned based on the policy described
   in [I-D.ietf-hip-rfc5201-bis]:

   o  GROUP_KEY_MATERIALS, (Value: 65530, Length: 33, Meaning: Group key
      materials for MLE and link-layer, Reference: this document).

10.  Acknowledgments

   The author would like to acknowledge the helpful comments of Randy
   Turner, Robert Cragie and Subir Das.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC6253]  Heer, T. and S. Varjonen, "Host Identity Protocol
              Certificates", RFC 6253, DOI 10.17487/RFC6253, May 2011,
              <http://www.rfc-editor.org/info/rfc6253>.

   [RFC7731]  Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
              and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
              February 2016, <http://www.rfc-editor.org/info/rfc7731>.



Ohba                    Expires October 21, 2016               [Page 10]


Internet-Draft              HIP DEX over MLE                  April 2016


   [I-D.ietf-hip-dex]
              Moskowitz, R. and R. Hummen, "HIP Diet EXchange (DEX)",
              draft-ietf-hip-dex-02 (work in progress), March 2016.

   [I-D.ietf-hip-rfc5201-bis]
              Moskowitz, R., Heer, T., Jokela, P., and T. Henderson,
              "Host Identity Protocol Version 2 (HIPv2)", draft-ietf-
              hip-rfc5201-bis-20 (work in progress), October 2014.

   [I-D.ietf-6lo-mesh-link-establishment]
              Kelsey, R., "Mesh Link Establishment", draft-ietf-6lo-
              mesh-link-establishment-00 (work in progress), December
              2015.

11.2.  External Informative References

   [IEEE802154]
              IEEE standard for Information Technology, "IEEE std.
              802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
              and Physical Layer (PHY) Specifications for Low-Rate
              Wireless Personal Area Networks", June 2011.

   [IEEE802154e]
              IEEE standard for Information Technology, "IEEE std.
              802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
              and Physical Layer (PHY) Specifications for Low-Rate
              Wireless Personal Area Networks - Amendment 1: MAC
              sublayer (Amendment to IEEE Std 802.15.4-2011)", April
              2012.

Author's Address

   Yoshihiro Ohba (editor)
   Toshiba Electronics Asia
   20 Pasir Panjang Road, #12-25/28, Mapletree Business City
   117439
   Singapore

   Phone: +65 6278 5252
   Email: yoshihiro.ohba@toshiba.co.jp











Ohba                    Expires October 21, 2016               [Page 11]


Html markup produced by rfcmarkup 1.123, available from https://tools.ietf.org/tools/rfcmarkup/