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Versions: 00 01 draft-ietf-6tisch-dtsecurity-secure-join

6tisch Working Group                                       M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Informational                          October 20, 2016
Expires: April 23, 2017

                      6tisch Secure Join protocol


   Charter: The WG will continue working on securing the join process
   and making that fit within the constraints of high latency, low
   throughput and small frame sizes that characterize IEEE802.15.4 TSCH.

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 April 23, 2017.

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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Credentials . . . . . . . . . . . . . . . . . . . . . . .   4
       1.2.1.  One-Touch Assumptions . . . . . . . . . . . . . . . .   4
       1.2.2.  Factory provided credentials (if any) . . . . . . . .   5
       1.2.3.  Credentials to be introduced  . . . . . . . . . . . .   5
     1.3.  Network Assumptions . . . . . . . . . . . . . . . . . . .   5
       1.3.1.  Security above and below IP . . . . . . . . . . . . .   6
       1.3.2.  Join network assumptions  . . . . . . . . . . . . . .   7
       1.3.3.  Number and cost of round trips  . . . . . . . . . . .   7
       1.3.4.  Size of packets, number of fragments  . . . . . . . .   7
     1.4.  Target end-state for join process . . . . . . . . . . . .   7
   2.  Join Protocol . . . . . . . . . . . . . . . . . . . . . . . .   7
     2.1.  Diagram of Join Process . . . . . . . . . . . . . . . . .   7
     2.2.  Description of Pledge States in Join Process  . . . . . .   8
       2.2.1.  (1) Layer-2 Enhanced Beacon . . . . . . . . . . . . .   8
       2.2.2.  (1B) Layer-3 Router Advertisement . . . . . . . . . .   8
       2.2.3.  (2) Pledge sends (unicast) Neighbor Solicitation to
               Join Assistant  . . . . . . . . . . . . . . . . . . .   8
       2.2.4.  (3) Join Assistant sends Query to Registar  . . . . .   9
       2.2.5.  (4) Join Assistant receives Acceptance response from
               Registrar . . . . . . . . . . . . . . . . . . . . . .   9
       2.2.6.  (5) Pledge receives (unicast) Neighbor Advertisement
               from join assistant . . . . . . . . . . . . . . . . .   9
     2.3.  Join process state machine for pledge . . . . . . . . . .  10
     2.4.  Description of Join Assistant States in Join Process  . .  11
       2.4.1.  Processing of Insecure Packets  . . . . . . . . . . .  12
   3.  Join Assistant to Registrar protocol  . . . . . . . . . . . .  13
     3.1.  Discovery of Registrar  . . . . . . . . . . . . . . . . .  13
     3.2.  Notification of a new pledge to Registar  . . . . . . . .  14
     3.3.  Passing of traffic from Pledge to Registar  . . . . . . .  14
   4.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  15
     4.1.  Privacy Considerations for Production network . . . . . .  15
     4.2.  Privacy Considerations for New Pledges  . . . . . . . . .  15
       4.2.1.  EUI-64 derived address for join time IID  . . . . . .  16
     4.3.  Privacy Considerations for Join Assistant . . . . . . . .  16
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   7.  Protocol Definition . . . . . . . . . . . . . . . . . . . . .  17
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Appendix A.  appendix . . . . . . . . . . . . . . . . . . . . . .  20
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  20

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1.  Introduction

   Enrollment of new nodes into LLNs present unique challenges.  The
   constrained nodes has no user interfaces, and even if they did,
   configuring thousands of such nodes manually is undesireable from a
   human resources issue, as well as the difficulty in getting
   consistent results.

   This document is about a standard way to introduce new nodes into a
   6tisch network that does not involve any direct manipulation of the
   nodes themselves.  This act has been called "zero-touch"
   provisioning, and it does not occur by chance, but requires
   coordination between the manufacturer of the node, the service
   operator running the LLN, and the installers actually taking the
   devices out of the shipping boxes.

   In other installations (such as some factory/industrial settings, and
   for some utilities), it is possible to pass devices through a
   "provisioning" room of some kind where the device in factory default
   state may be touched once (via a cable, or a push button, or by being
   placed in a faraday cage, etc.) such that the devices can be
   initialized in a way specific to that installation.  The devices are
   then returned to inventory, and may be deployed at some future time.
   The node is not provisioned with the current keying material, as the
   network will need to be regularly rekeyed (even the algorithms may
   change!), so in the one-touch provisioning case, the goal is simply
   to introduce some elements into the new node (the "pledge") such that
   the enrollment process will take less energy and fewer network

1.1.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119] and indicate requirement levels for compliant STuPiD

   The following terminology is repeated from
   [I-D.ietf-anima-bootstrapping-keyinfra] so as to have a common way to

   drop ship  The physical distribution of equipment containing the
      "factory default" configuration to a final destination.  In zero-
      touch scenarios there is no staging or pre-configuration during

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   imprint  the process where a device obtains the cryptographic key
      material to identity and trust future interactions with a network.
      This term is taken from Konrad Lorenz's work in biology with new
      ducklings: during a critical period, the duckling would assume
      that anything that looks like a mother duck is in fact their
      mother.  An equivalent for a device is to obtain the fingerprint
      of the network's root certification authority certificate.  A
      device that imprints on an attacker suffers a similar fate to a
      duckling that imprints on a hungry wolf.  Securely imprinting is a
      primary focus of this document. [duckling] anticipates this use.

   enrollment  the process where a device presents key material to a
      network and acquires a network specific identity.  For example
      when a certificate signing request is presented to a certification
      authority and a certificate is obtained in response.

   pledge  the prospective device, which has the identity provided to at
      the factory.  Neither the device nor the network knows if the
      device yet knows if this device belongs with this network.  This
      is definition 6, according to [pledge].

   Audit Token  A signed token from the manufacturer authorized signing
      authority indicating that the bootstrapping event has been
      successfully logged.  This has been referred to as an
      "authorization token" indicating that it authorizes bootstrapping
      to proceed.

   Ownership Voucher  A signed voucher from the vendor vouching that a
      specific domain "owns" the new entity as defined in

1.2.  Credentials

   In the zero-touch scenario, every device expected to be drop shipped
   would have an [ieee802-1AR] manufacturer installed certificate (MIC).
   The private key part of the certificate would either be generated in
   the device, or installed securely (and privately) as part of the
   manufacturer process.  [cullenCiscoPhoneDeploy] provides an example
   of process which has been active for a good part of a decade.

   The MIC would be signed by the manufacturer's CA, the public key
   component of that would be included in the firmware.

1.2.1.  One-Touch Assumptions

   In a one-touch scenario, devices would be provided with some
   mechanism by which a secure association may be made in a controlled
   environment.  There are many ways in which this might be done, and

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   detailing any of them is out of scope for this document.  But, some
   notion of how this might be done is important so that the underlying
   assumptions can be reasoned about.

   Some examples of how to do this could include: * JTAG interface *
   serial (craft) console interface * pushes of physical buttons
   simulatenous to network attachment * insecured devices operated in a
   Faraday cage

   There are likely many other ways as well.  What is assumed is that
   there can be a secure, private conversation between the Join
   Coordination Entity, and the Pledge, and that the two devices can
   exchange some trusted bytes of information.

1.2.2.  Factory provided credentials (if any)

   When a manufacturer installed certificate is provided as the IDevID,
   it SHOULD contain a number of fields.
   [I-D.ietf-anima-bootstrapping-keyinfra] provides a detailed set of

   A manufacturer unique serial number MUST be provided in the
   serialNumber SubjectAltName extension, and MAY be repeated in the
   Common Name.  There are no sequential or numeric requirements on the
   serialNumber, it may be any unique value that the manufacturer wants
   to use.  The serialNumber SHOULD be printed on the packaging and/or
   on the device in a discrete way.

1.2.3.  Credentials to be introduced

   The goal of the bootstrap process is to introduce one or more new
   locally relevant credentials:

   1.  a certificate signed by a local certificate authority/registrar.
       This is the LDevID of [ieee802-1AR].

   2.  alternatively, a network-wide key to be used to secure L2

   3.  alternatively, a network-wide key to be used to authenticate per-
       peer keying of L2 traffic using a mechanism such as provided by

1.3.  Network Assumptions

   This document is about enrollment of constrained devices [RFC7228] to
   a constrained network.  Constrained networks is such as [ieee802154],
   and in particular the time-slotted, channel hopping (tsch) mode,

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   feature low bandwidths, and limited opportunities to transmit.  A key
   feature of these networks is that receivers are only listening at
   certain times.

1.3.1.  Security above and below IP

   802.15.4 networks have three kinds of layer-2 security:

   o  a network key that is shared with all nodes and is used for
      unicast and multicast.

   o  a series of network keys that are shared (agreed to) between pairs
      of nodes (the per-peer key)

   o  a network key that is shared with all nodes (through a group key
      management system), and is used for multicast traffic only

   Setting up the credentials to bootstrap one of these kinds of
   security, (or directly configuring the key itself for the first case)
   is required.  This is the security below the IP layer.

   Security is required above the IP layer: there are three aspects
   which the credentials in the previous section are to be used.

   o  to provide for secure connection with a Path Computation Element
      [RFC4655], or other LLC (see ({RFC7554}} section 3).

   o  to initiate a connection between a Resource Server (RS) and an
      application layer Authorization Server (AS and CAS from
      [I-D.ietf-ace-actors]).  Perfect Forward Secrecy

   Perfert Forward Secrecy (PFS) is the property of a protocol such that
   complete knowledge of the crypto state (for instance, via a memory
   dump) at time X does not imply that data from a disjoint time Y can
   also be recovered.  ([PFS]).

   PFS is important for two reasons: one is that it offers protection
   against the compromise of a node.  It does this by changing the keys
   in a non-deterministic way.  This second property also makes it much
   easier to remove a node from the network, as any node which has not
   participated in the key changing process will find itself no longer

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1.3.2.  Join network assumptions

   The network which the new pledge will connect to will have to have
   the following properties:

   o  a known PANID.  The PANID 0xXXXX where XXXX is the assigned RFC#
      for this document is suggested.

   o  a minimal schedule with some Aloha time.  This is usually in the
      same slotframe as the Extended Beacon, but a pledge MUST listen
      for an unencrypted Extended Beacon to so that it can synchronize.

   o  a known K1 key, as described in [I-D.ietf-6tisch-minimal] section
      10, and used for reasons similar to [iec62591].

1.3.3.  Number and cost of round trips

1.3.4.  Size of packets, number of fragments

1.4.  Target end-state for join process

2.  Join Protocol

   This section describes the interaction between a new pledge and the
   Join Assistant.

2.1.  Diagram of Join Process

   This time sequence diagram intentionally shows additional layer-2 and
   layer-3 interactions, in order to put the entire process into

       <--------------- BEACON-L2                   (1)
       <-------RA ------                            (1B)
       ---- NS w/ARO --->                           (2)
                              ------- QUERY---->    (3)
                              <------ REPLY-----    (4)
       <--- NA answer----                           (5)

                   some time later
       <-----coaps--------<=======IPIP-COAPS====    (6)
                   multiple trips
       ------------------->====================>    (7)

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2.2.  Description of Pledge States in Join Process

2.2.1.  (1) Layer-2 Enhanced Beacon

   A new pledge must listen for a beacon for a period of at least 2s
   (HELP) on each of the 16 possible channels.  The pledge SHOULD
   collect all beacons from heard on all channels before selecting a
   beacon to start with.  If the pledge is unable to record all of the
   beacons that it hears due to limitations on volatile storage, then it
   should at least attempt to record the detail as to how to find that
   beacon again (channel, time sequence).

   This search process entails having the pledge keep the receiver
   portion of it's radio active for the entire period of time.

   The selection of which beacon to start with is outside the scope of
   this document.  Implementers SHOULD make use of information such as:
   whether the L2 address of the Beacon has been tried before, whether a
   Router Advertisement IE is present, any Network Identifier
   [I-D.richardson-6lo-ra-in-ie] seen, and the strength of the signal.

   Once a candidate network has been selected, the pledge can transition
   into a low-power duty cycle, waking only when the provided schedule
   indicates ALOHA slots which the pledge may use for the join process.

2.2.2.  (1B) Layer-3 Router Advertisement

   If [I-D.richardson-6lo-ra-in-ie] has not been used to embed a router
   advertisement in the Enhanced Beacon, then the pledge MUST wait to
   hear a Router Advertisement to know the layer-3 address of the
   adjacent router.  These will be broadcast periodically during the
   ALOHA slot.

   A pledge MAY timeout and send a layer-2 unicast Router Solicitation
   (to the layer-2 of the Enhanced Beacon) to the layer-3 all-routers
   address.  A pledge MAY also take this timeout to mean that this
   router is unwilling to perform Join Assistant activities and the
   pledge should move on to another Enhanced Beacon.

2.2.3.  (2) Pledge sends (unicast) Neighbor Solicitation to Join

   This NS message is formed much like a Duplicate Address Detection
   (DAD) message described in [RFC6775] section-4.3: it is a
   solicitation by the pledge for it's own address.  [RFC6775] does not
   describe doing DAD for link-local address however, so this aspect is

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   The Join Assistant will not validate the uniqueness using the DAR/DAC
   mechanism, but will otherwise process the NS as per normal:
   populating neighbor cache entries.  The Join Assistant will take
   extra care with expiring neighbor cache entries: unsecured NS should
   never push secured NCE entries out of the cache or overwrite them.
   There are two equivalent ways to do this:

   1.  marking the origin of the NCE and limiting unsecured ones to some
       portion of the entries;

   2.  by considering unsecured NS to be arriving from a different
       virtual interface (different if_index) than secured ones.  NCEs
       from different interfaces SHOULD already not be mixed.

   The pledge SHOULD NOT have configured a short Layer-2 address as it
   has no way to allocate a non-duplicate short address.  It SHOULD have
   formed a standard 64-bit layer-3 link-local address using a built-in
   IID.  This IID MUST be placed into the Address Resolution option
   (ARO) option in the Neighbor Soliciation, as it serves as the index
   by which the domain registrar will use to identify the device.

   The IID MAY be related to the layer-2 address, but privacy
   considerations recommend that the IID SHOULD instead be a form a
   stable privacy address [RFC7217].  Whichever method is used MUST be
   decided at manufacturing time, as the IID is also repeated as the
   SerialNumber in the Manufacturer Installed Certificate (MIC), also
   referred to as the 802.1AR IDevID.

2.2.4.  (3) Join Assistant sends Query to Registar

   This step does not involve the pledge, and it is described in section

2.2.5.  (4) Join Assistant receives Acceptance response from Registrar

   This step does not involve the pledge, and it is described in section

2.2.6.  (5) Pledge receives (unicast) Neighbor Advertisement from join

   This NA message is again identical to the Duplicate Address Detection
   mechanism described in [RFC6775].  The status field of the ARO is
   extended (see (#ianaconsiderations)) to include an additional status

   The pledge, upon receipt of ND_NS_JOIN_DECLINED considers that this
   network is not an appropriate network to join, and SHOULD move on to

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   attempt other networks.  The pledge MUST also realize that this NA
   message MAY have been forced, and it SHOULD attempt joining this
   network again at a future time, but MUST NOT repeatedly attempt to
   join the same network.

   The pledge, upon receipt of a Neighbor Cache Full response SHOULD
   attempt to join using a different join assistant on the same network.

   The pledge, upon receipt of a Duplicate Address response SHOULD
   attempt to join using a different join assistant on a different
   network, if it has such offers.  If it has no such offers, it should
   wait at least NEIGHBOR-CACHE TIMEOUT, and then retry.  This may be a
   sign of a Denial of Service attack, or it may be a non-malicious mis-

   Upon receive of a successful NA, the pledge SHOULD consider that it
   is now in enrolled in a join queue.  The pledge SHOULD resend
   Neighbor Soliciation (NUD) messages periodically as described in
   [RFC6775] to maintain the neighbor cache entry.

   A pledge with other Join Assistant offers MAY abandon this Join
   Assistant after a period of XXX minutes and attempt to join using a
   different Join Assistant.

2.3.  Join process state machine for pledge

         +----------------+         +----------+
         |  collecting    |-------->| sleep 1m |
         |    beacons     |<-----   +~~~~~~~~~~+
         +----------------+      \______/    ^
                 |                           |
                 V                           | no beacons
         +-----------------+                 | remain
         |  try next/first |                 |
         |   beacon/sched  |-----------------/
         +-----------------+<____________ timeout
                 |                       \--.<--.
                 | send NS/DAD <-------.    |   |
       /-------->|  w/ARO              |    |   |
       |         |              timeout|    |   |
       |         V           retries<3 |    |   |
       | +-----------------+           |    |   |
       | |  waiting for    |           |    |   |
       | |   NA w/ARO      |----------->---->   |
       | +-----------------+   or invalid NA    |
       |         |                              |
       |         |                              |
       |         |                              |

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       |         V                              |
       | +-----------------+   DTLS failure     |
       | |  open DTLS 6p   |--------------------/
       | |  for system     |                    ^
       | |   keychain      |<--------\          |
       | +-----------------+         |          |
       |         |                   | conclude |
       |         |         kill DTLS |  not net |
       |         |         try again |  looking |
       |         |         retries<3 |      for |
       |         V                   |          |
       | +-----------------+         |          |
       | | validate audit  |---------/----------/
       | |token posted to  |  does not validate
       | | proper URL      |
       | +-----------------+
       |         |
       |too long | validate
       |try      |  audit
       |again    |  token
       |         V
       | +-----------------+
       \-| accept 6p trans-|
         | actions for new |
         | certificate     |
                 | receive new certificate,
                 V  restart with beacon
                 X  run appropriate KMP

2.4.  Description of Join Assistant States in Join Process

   The Join Assistant is a standard 6LR.  It processes packets as
   described in [RFC6775], [I-D.ietf-6tisch-minimal] from secured
   (encrypted) sources.

   In particular the maintenance of Neighbor Cache Entries as described
   in [RFC6775] section 3.5.  The Join Assistant maintains two sets of
   NCE for each physical interface that it has: one set is for secured
   neighbors, and the other is for new pledges that wish to join.  The
   storage allocated for pledges will generally be a small fraction of
   available space.  The Join Assistant will garbage collect the
   different caches according to different thresholds.  It MAY chose to
   free space from the insecure cache to make space for additional
   secure entries, but it MUST NOT do the opposite.

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   It sends Enhanced Beacons which are authenticated with the network-
   wide key ("K2"), but it does not encrypt the Beacons.

   In addition, it listen for packets "encrypted" with the well-known
   "K1" key, and when it receives them, it considers them to be as
   "Insecure Packets".  It MAY also accept unencrypted, unauthenticated
   packets as being "Insecure Packets"

   Non-Join Assistant 6LRs would never accept K1 packets, nor
   unauthenticated packets.  Normal 6LRs and hosts MUST accept
   unencrypted Enhanced Beacons which can be authenticated with the "K2"

   In addition to seperating the secured and insecured packets for
   inbound processing, the Join Assistant also allocates a unique IID
   for the insecured interface.  This IID is used to configure the Link
   Local address on that virtual interface.  This Link Local address is
   called the Insecure Join Assistant Link Local, or IJALL.

   In addition, this IID is combined with the global prefix(es) (as
   found in various PIO(s) from the routing protocols).  This additional
   address is configured as an alias on the loopback interface such that
   the Join Assistant can receive packets to this address via secured
   network.  This activity SHOULD generate a routing protocol update
   (such as an updated DAO).  This IID SHOULD be generated using a
   stable privacy address mechanism as described in [RFC7217].  The
   easiest is to assign the insecure virtual interface a unique
   if_index.  This new address is called the Pledge Tunnel End Point
   Address, or PTEPA.

2.4.1.  Processing of Insecure Packets

   Only the following insecure packets are to be accepted by the Join

   1.  Unicast Neighbor Solicitations.

   2.  Unicast Link-Local UDP packets with a destination port that map
       to the Join Assistant's IPIP proxy.  Processing of Insecure Neighbor Solicitation packets

   Upon receipt of an insecure unicast NS with an ARO option, the Join
   Assistant looks up an NCE by the IID contained in the ARO in the
   insecure cache.  If it finds an existing there are three

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   1.  a lookup for this entry has previously been completed, and has
       resulted in a negative result.  In this case, a negative
       ND_NS_JOIN_DECLINED NA is returned.  The Join Assistant SHOULD
       rate limit the number of these messages that it is willing to

   2.  a lookup for this entry has previously been done, and has
       resulted in a positive result.  The NCE entry should be
       "refresh", to keep it in the cache for a longer period of time,
       and a new NA returned with a positive status.

   3.  a lookup for this entry has previously been started, but no
       result has been received.  In this case the Join Assistant SHOULD
       remain silent.  The Join Assistant may wish to send a GRASP
       M_NOOP message to verify that the connection is still useable if
       it has not receive any traffic in some time.

   If it does not find an existing entry, and there is space for another
   entry, (or it can make space via garbage collection), then a new
   entry is created, marked to be "in progress", and a new GRASP 6JOIN
   query is initiated, see section (#6joingrasp).

3.  Join Assistant to Registrar protocol

   There are three aspects to the protocols that the Join Assistant uses
   to communicate about its needs.  They are:

   1.  Discovery of Registrar

   2.  Notification of new pledge to Registrar

   3.  Passing of traffic from Pledge to Registar

3.1.  Discovery of Registrar

   The address of the registrar MAY be determined by other protocols,
   such as DHCP, RA or RPL extensions, or provisioned into the Join
   Assistant via other configuration protocol such as 6p.

   In order to support fully autonomic operations, the Join Assistant
   MAY use a GRASP discovery ([I-D.ietf-anima-grasp]) to find the
   address of the Registrar.  [I-D.richardson-anima-6join-discovery]
   describes the details of the process.

   In 6tisch networks multicast is not always available, requiring
   additional protocol [RFC7731] effort.  Instead of doing a multicast
   GRASP discovery, the Join Assistant SHOULD instead to a TCP connect
   to the GRASP_LISTEN_PORT on the IP address of the DODAG root (when

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   RPL is used as the routing protocol for 6tisch), or the ABRO address
   when another protocol is used.  The Join Assistant should then issue
   the appropriate M_DISCOVERY method using the 6JOIN objective.  The
   GRASP discovery will then reply using the same TCP connection as per
   Unicast Discovery in [I-D.ietf-anima-grasp] section TBD.

3.2.  Notification of a new pledge to Registar

   As illustrated in (#joindiagram), when the Join Assistant receives a
   Neighbor Solication from a pledge, it must notify the Registar of the
   pledge, indicating to it how to reach the new pledge.  The Registrar
   will respond with a positive acknowledgement if the Registrar is
   willing/able to accept the pledge.  The Registrar will respond with a
   negative acknowledgement if the provided pledge identity (the IID in
   the ARO) is not one that the Registrar recognizes as belonging to
   this network.

   The Registrar runs an ASA which is called the 6JOIN ASA (which can be
   discovered above).  This query/response is done using GRASP with the
   discovered ASA process.

   The query process is described in CDDL as:

request-6join-query = [M_REQ_NEG, session-id, "6JOIN", [IID, "6p-ipip"]]
IID = bytes .size 8

   The response from the Registrar is describe as:

   response-6join-query = [M_END, session-id, [O_ACCEPT]]

   or for a negative response:

   response-6join-query = [M_END, session-id, [O_DECLINE]]

   for the 6p-ipip, the Registrar will need to know where to send the
   IPIP packets to.  The Join Assistant will initiate the TCP connection
   to the Registrar's ASA using the IPv6 address associated with the
   insecure interface on which the pledge is located, i.e. using the

3.3.  Passing of traffic from Pledge to Registar

   When the Registrar is ready to initiate the pledge into the domain,
   the Registrar will reach out to the pledge using a secure CoAP
   protocol (6p).  The security is provided using DTLS or EDHOC.  As the
   pledge has only a link-local address, and the Registrar is not co-
   located on the same layer-2 as the pledge, the traffic must be
   relayed through the Join Assistant.

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   To do this the Registrar needs to configure a Link Local address on a
   virtual inteface which is the same as the PTEPA derived address.

   The Registrar then sends it's traffic (UDP packets with CoAPS
   inside), inside of an IPIP header to the Join Assistant.  The outer
   IP header is from the Registrar to the PTEPA.  The inner IP is from
   the link local address configured above, and the destination is the
   Link Local address of the pledge.

   The Registrar knows the IJALL by taking the IID from the connection
   address above, and knows the Link Local of the pledge from the IID in
   the objective message.

   The Join Assistant, upon receipt of the IPIP traffic from the
   Registar on it's PTEPA, then decapsulates it and forwards it on the
   appropriate.  (This is identical code to decapsulation of IPIP
   headers as specified in [I-D.ietf-roll-useofrplinfo].

   The Join Assistant, upon receiving traffic from the pledge to the
   IJALL, it encapsulates it into an IPIP header, setting the source of
   this outer header to the PTEPA, and the destination being the

   The Join Assistant can do this for as many pledges as the Registrar
   decides to communicate with, without using any additional per-pledge
   state other than the obligatory Neighbor Cache Entries needed to
   translate L3 addresses to L2 addresses.

4.  Privacy Considerations

   [I-D.ietf-6lo-privacy-considerations] details a number of privacy
   considerations important in Resource Constrained nodes.  There are
   two networks and three sets of constrained nodes to consider.  They
   are: 1. the production nodes on the production network.  2. the new
   pledges, which have yet to enroll, and which are on a join network.
   3. the production nodes which are also acting as proxy nodes.

4.1.  Privacy Considerations for Production network

   The details of this are out of scope for this document.

4.2.  Privacy Considerations for New Pledges

   New Pledges do not yet receive Router Advertisements with PIO
   options, and so configure link-local addresses only based upon
   layer-2 addresses using the normal SLAAC mechanisms described in

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   These link-local addresses are visible to any on-link eavesdropper
   (who is synchronized to the same Join Assistant), so regardless of
   what is chosen they can be seen.  This link-layer traffic is
   encapsulated by the Join Assistant into IPIP packets and carried to
   the JCE.  The traffic SHOULD never leave the operator's network, and
   no outside traffic should enter, so it should not be possible to do
   any ICMP scanning as described in

   The join process described herein requires that some identifier
   meaningful to the network operator be communicated to the JCE via the
   Neighbor Advertisement's ARO option.  This need not be a manufacturer
   created EUI-64 as assigned by IEEE; it could be another value with
   higher entropy and less interesting vendor/device information.
   Regardless of what is chosen, it can be used to track where the
   device attaches.

   For most constrained device, network attachment occurs very
   infrequently, often only once in their lifetime, so tracking
   opportunities may be rare.

   Further, during the enrollment process, a DTLS connection connection
   will be created.  Unless TLS1.3 is used, the device identity will be
   visible to passive observers in the 802.11AR IDevID certificate that
   is sent.  Even when TLS1.3 is used, an active attacker could collect
   the information by simply connecting to the device; it would not have
   to successful complete the negotiation either, or even attempt to
   Man-In-The-Middle the device.

   There is, at the same time, significant value in avoiding a link-
   local DAD process by using an IEEE assigned EUI-64, and there is also
   significant advantage to the operator being able to see what the
   vendor of the new device is.

4.2.1.  EUI-64 derived address for join time IID

   It is therefore suggested that the IID used in the link-local address
   used during the join process be a vendor assigned EUI-64.  After the
   join process has concluded, the device SHOULD be assigned a unique
   randomly generated long address, and a unique short address (not
   based upon the vendor EUI-64) for use at link-layer.  At that point,
   all layer-3 content is encrypted by the layer-2 key.

4.3.  Privacy Considerations for Join Assistant

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5.  Security Considerations

6.  IANA Considerations

   This document allocates one value from the subregistry "Address
   Registration Option Status Values": ND_NS_JOIN_DECLINED Join
   Assistant, JOIN DECLINED (TBD-AA)

7.  Protocol Definition

8.  References

8.1.  Normative References

              Jennings, C., "Transitive Trust Enrollment for Constrained
              Devices", 2012, <http://www.lix.polytechnique.fr/hipercom/

              Thaler, D., "Privacy Considerations for IPv6 over Networks
              of Resource-Constrained Nodes", draft-ietf-6lo-privacy-
              considerations-03 (work in progress), September 2016.

              Vilajosana, X. and K. Pister, "Minimal 6TiSCH
              Configuration", draft-ietf-6tisch-minimal-16 (work in
              progress), June 2016.

              Pritikin, M., Richardson, M., Behringer, M., and S.
              Bjarnason, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-03 (work in progress), June 2016.

              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-07 (work in progress), September 2016.

              Watsen, K. and M. Abrahamsson, "Zero Touch Provisioning
              for NETCONF or RESTCONF based Management", draft-ietf-
              netconf-zerotouch-09 (work in progress), July 2016.

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              Richardson, M., "802.15.4 Informational Element
              encapsulation of ICMPv6 Router Advertisements", draft-
              richardson-6lo-ra-in-ie-00 (work in progress), October

              Richardson, M., "GRASP discovery of Registrar by Join
              Assistant", draft-richardson-anima-6join-discovery-00
              (work in progress), October 2016.

              IEC, ., "62591:2016 Industrial networks - Wireless
              communication network and communication profiles -
              WirelessHART", 2016, <https://webstore.iec.ch/

              IEEE Standard, ., "IEEE 802.1AR Secure Device Identifier",
              2009, <http://standards.ieee.org/findstds/

              IEEE Standard, ., "802.15.4-2015 - IEEE Standard for Low-
              Rate Wireless Personal Area Networks (WPANs)", 2015,

              IEEE Standard, ., "802.15.9-2016 - IEEE Approved Draft
              Recommended Practice for Transport of Key Management
              Protocol (KMP) Datagrams", 2016,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,

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   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014,

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,

8.2.  Informative References

              Stajano, F. and R. Anderson, "The resurrecting duckling:
              security issues for ad-hoc wireless networks", 1999,

              Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
              architecture for authorization in constrained
              environments", draft-ietf-ace-actors-04 (work in
              progress), September 2016.

              Robles, I., Richardson, M., and P. Thubert, "When to use
              RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
              useofrplinfo-08 (work in progress), September 2016.

   [PFS]      Wikipedia, ., "Forward Secrecy", August 2016,

   [pledge]   Dictionary.com, ., "Dictionary.com Unabridged", 2015,

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <http://www.rfc-editor.org/info/rfc4191>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,

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   [RFC7554]  Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
              IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
              Internet of Things (IoT): Problem Statement", RFC 7554,
              DOI 10.17487/RFC7554, May 2015,

   [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>.

Appendix A.  appendix

   insert appendix here

Author's Address

   Michael Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca

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