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Versions: (draft-vanderstok-anima-constrained-join-proxy) 00 01

anima Working Group                                        M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Standards Track                         P. van der Stok
Expires: June 4, 2021                             vanderstok consultancy
                                                           P. Kampanakis
                                                           Cisco Systems
                                                       December 01, 2020


           Constrained Join Proxy for Bootstrapping Protocols
                 draft-anima-constrained-join-proxy-01

Abstract

   This document defines a protocol to securely assign a pledge to a
   domain, represented by a Registrar, using an intermediary node
   between pledge and Registrar.  This intermediary node is known as a
   "constrained Join Proxy".

   This document extends the work of
   [I-D.ietf-anima-bootstrapping-keyinfra] by replacing the Circuit-
   proxy by a stateless/stateful constrained (CoAP) Join Proxy.  It
   transports join traffic from the pledge to the Registrar without
   requiring per-client state.

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 https://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 June 4, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   4.  Join Proxy functionality  . . . . . . . . . . . . . . . . . .   4
   5.  Join Proxy specification  . . . . . . . . . . . . . . . . . .   5
     5.1.  Statefull Join Proxy  . . . . . . . . . . . . . . . . . .   5
     5.2.  Stateless Join Proxy  . . . . . . . . . . . . . . . . . .   6
     5.3.  Stateless Message structure . . . . . . . . . . . . . . .   8
   6.  Comparison of stateless and statefull modes . . . . . . . . .   9
   7.  Discovery . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Pledge discovery of Registrar . . . . . . . . . . . . . .  11
       7.1.1.  CoAP discovery  . . . . . . . . . . . . . . . . . . .  11
       7.1.2.  Autonomous Network  . . . . . . . . . . . . . . . . .  11
       7.1.3.  6tisch discovery  . . . . . . . . . . . . . . . . . .  11
     7.2.  Pledge discovers Join Proxy . . . . . . . . . . . . . . .  11
       7.2.1.  Autonomous Network  . . . . . . . . . . . . . . . . .  11
       7.2.2.  CoAP discovery  . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Resource Type registry  . . . . . . . . . . . . . . . . .  13
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  13
   12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.1.  00 to 01 . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.2.  00 to 00 . . . . . . . . . . . . . . . . . . . . . . . .  14
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     13.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Stateless Proxy payload examples . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Enrolment of new nodes into networks with enrolled nodes present is
   described in [I-D.ietf-anima-bootstrapping-keyinfra] ("BRSKI") and
   makes use of Enrolment over Secure Transport (EST) [RFC7030] with



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   [RFC8366] vouchers to securely enroll devices.  BRSKI connects new
   devices ("pledges") to "Registrars" via a Join Proxy.

   The specified solutions use https and may be too large in terms of
   code space or bandwidth required for constrained devices.
   Constrained devices possibly part of constrained networks [RFC7228]
   typically implement the IPv6 over Low-Power Wireless personal Area
   Networks (6LoWPAN) [RFC4944] and Constrained Application Protocol
   (CoAP) [RFC7252].

   CoAP can be run with the Datagram Transport Layer Security (DTLS)
   [RFC6347] as a security protocol for authenticity and confidentiality
   of the messages.  This is known as the "coaps" scheme.  A constrained
   version of EST, using Coap and DTLS, is described in
   [I-D.ietf-ace-coap-est].  The {I-D.ietf-anima-constrained-voucher}
   describes the BRSKI extensions to the Registrar.

   DTLS is a client-server protocol relying on the underlying IP layer
   to perform the routing between the DTLS Client and the DTLS Server.
   However, the new "joining" device will not be IP routable until it is
   authenticated to the network.  A new "joining" device can only
   initially use a link-local IPv6 address to communicate with a
   neighbour node using neighbour discovery [RFC6775] until it receives
   the necessary network configuration parameters.  However, before the
   device can receive these configuration parameters, it needs to
   authenticate itself to the network to which it connects.  IPv6
   routing is necessary to establish a connection between joining device
   and the Registrar.

   A DTLS connection is required between Pledge and Registrar.

   This document specifies a new form of Join Proxy and protocol to act
   as intermediary between joining device and Registrar to establish a
   connection between joining device and Registrar.

   This document is very much inspired by text published earlier in
   [I-D.kumar-dice-dtls-relay].
   [I-D.richardson-anima-state-for-joinrouter] outlined the various
   options for building a join proxy.
   [I-D.ietf-anima-bootstrapping-keyinfra] adopted only the Circuit
   Proxy method (1), leaving the other methods as future work.  This
   document standardizes the CoAP/DTLS (method 4).

2.  Terminology

   The following terms are defined in [RFC8366], and are used
   identically as in that document: artifact, imprint, domain, Join




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   Registrar/Coordinator (JRC), Manufacturer Authorized Signing
   Authority (MASA), pledge, Trust of First Use (TOFU), and Voucher.

3.  Requirements 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
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

4.  Join Proxy functionality

   As depicted in the Figure 1, the joining Device, or pledge (P), in an
   LLN mesh can be more than one hop away from the Registrar (R) and not
   yet authenticated into the network.

   In this situation, it can only communicate one-hop to its nearest
   neighbour, the Join Proxy (J) using their link-local IPv6 addresses.
   However, the Pledge (P) needs to communicate with end-to-end security
   with a Registrar hosting the Registrar (R) to authenticate and get
   the relevant system/network parameters.  If the Pledge (P) initiates
   a DTLS connection to the Registrar whose IP address has been pre-
   configured, then the packets are dropped at the Join Proxy (J) since
   the Pledge (P) is not yet admitted to the network or there is no IP
   routability to Pledge (P) for any returned messages.

             ++++ multi-hop
             |R |---- mesh  +--+        +--+
             |  |    \      |J |........|P |
             ++++     \-----|  |        |  |
                            +--+        +--+
          Registrar       Join Proxy   Pledge
                                       "Joining" Device


                      Figure 1: multi-hop enrolment.

   Without routing the Pledge (P) cannot establish a secure connection
   to the Registrar (R) in the network assuming appropriate credentials
   are exchanged out-of-band, e.g. a hash of the Pledge (P)'s raw public
   key could be provided to the Registrar (R).

   Furthermore, the Pledge (P) may be unaware of the IP address of the
   Registrar (R) to initiate a DTLS connection and perform
   authentication.





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   To overcome the problems with non-routability of DTLS packets and/or
   discovery of the destination address of the EST Server to contact,
   the Join Proxy is introduced.  This Join Proxy functionality is
   configured into all authenticated devices in the network which may
   act as the Join Proxy for newly joining nodes.  The Join Proxy allows
   for routing of the packets from the Pledge using IP routing to the
   intended Registrar.

5.  Join Proxy specification

   A Join Proxy can operate in two modes:

   o  Statefull mode

   o  Stateless mode

5.1.  Statefull Join Proxy

   In stateful mode, the joining node forwards the DTLS messages to the
   Registrar.

   Assume that the Pledge does not know the IP address of the Registrar
   it needs to contact.  In that situation, the Join Proxy must know the
   (configured or discovered) IP address of a Registrar.  (Discovery can
   be based upon [I-D.ietf-anima-bootstrapping-keyinfra] section 4.3, or
   via DNS-SD service discovery [RFC6763]).  The Pledge initiates its
   request as if the Join Proxy is the intended Registrar.  The Join
   Proxy changes the IP packet (without modifying the DTLS message) by
   modifying both the source and destination addresses to forward the
   message to the intended Registrar.  The Join Proxy maintains a
   4-tuple array to translate the DTLS messages received from the
   Registrar and forward it to the EST Client.  This is a form of
   Network Address translation, where the Join Proxy acts as a forward
   proxy.  In Figure 2 the various steps of the message flow are shown,
   with 5684 being the standard coaps port:
















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   +------------+------------+-------------+--------------------------+
   |   Pledge   | Join Proxy |  Registrar  |          Message         |
   |    (P)     |     (J)    |    (R)      | Src_IP:port | Dst_IP:port|
   +------------+------------+-------------+-------------+------------+
   |      --ClientHello-->                 |   IP_P:p_P  | IP_Ja:5684 |
   |                    --ClientHello-->   |   IP_Jb:p_Jb| IP_R:5684  |
   |                                       |             |            |
   |                    <--ServerHello--   |   IP_R:5684 | IP_Jb:p_Jb |
   |                            :          |             |            |
   |       <--ServerHello--     :          |   IP_Ja:5684| IP_P:p_P   |
   |               :            :          |             |            |
   |               :            :          |       :     |    :       |
   |               :            :          |       :     |    :       |
   |        --Finished-->       :          |   IP_P:p_P  | IP_Ja:5684 |
   |                      --Finished-->    |   IP_Jb:p_Jb| IP_R:5684  |
   |                                       |             |            |
   |                      <--Finished--    |   IP_R:5684 | IP_Jb:p_Jb |
   |        <--Finished--                  |   IP_Ja:5684| IP_P:p_P   |
   |              :             :          |      :      |     :      |
   +---------------------------------------+-------------+------------+
   IP_P:p_P = Link-local IP address and port of Pledge (DTLS Client)
   IP_R:5684 = Global IP address and coaps port of Registrar
   IP_Ja:5684 = Link-local IP address and coaps port of Join Proxy
   IP_Jb:p_Rb = Global IP address and port of Join proxy

    Figure 2: constrained statefull joining message flow with Registrar
                       address known to Join Proxy.

5.2.  Stateless Join Proxy

   The stateless Join Proxy aims to minimize the requirements on the
   constrained Join Proxy device.  Stateless operation requires no
   memory in the Join Proxy device, but may also reduce the CPU impact
   as the device does not need to search through a state table.

   When a client joining device attempts a DTLS connection to the
   Registrar, it uses its link-local IP address as its IP source
   address.  This message is transmitted one-hop to a neighbouring (join
   proxy) node.  Under normal circumstances, this message would be
   dropped at the neighbour node since the pledge is not yet IP routable
   or it is not yet authenticated to send messages through the network.
   However, if the neighbour device has the Join Proxy functionality
   enabled, it routes the DTLS message to a specific Registrar.
   Additional security mechanisms need to exist to prevent this routing
   functionality being used by rogue nodes to bypass any network
   authentication procedures.





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   If an untrusted pledge that can only use link-local addressing wants
   to contact a trusted Registrar, it sends the DTLS message to the Join
   Proxy.

   The Join Proxy extends this message into a new type of message called
   Join ProxY (JPY) message and sends it on to the Registrar.

   The JPY message payload consists of two parts:

   o  Header (H) field: consisting of the source link-local address and
      port of the Pledge (P), and

   o  Contents (C) field: containing the original DTLS message.

   On receiving the JPY message, the Registrar retrieves the two parts.

   The Registrar transiently stores the Header field information.  The
   Registrar uses the Contents field to execute the Registrar
   functionality.  However, when the Registrar replies, it also extends
   its DTLS message with the header field in a JPY message and sends it
   back to the Join Proxy.  The Registrar SHOULD NOT assume that it can
   decode the Header Field, it should simply repeat it when responding.
   The Header contains the original source link-local address and port
   of the pledge from the transient state stored earlier and the
   Contents field contains the DTLS message.

   On receiving the JPY message, the Join Proxy retrieves the two parts.
   It uses the Header field to route the DTLS message retrieved from the
   Contents field to the Pledge.

   The Figure 3 depicts the message flow diagram:




















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   +--------------+------------+---------------+-----------------------+
   | EST  Client  | Join Proxy |    Registrar  |        Message        |
   |     (P)      |     (J)    |      (R)      |Src_IP:port|Dst_IP:port|
   +--------------+------------+---------------+-----------+-----------+
   |      --ClientHello-->                     | IP_P:p_P  |IP_Ja:p_Ja |
   |                    --JPY[H(IP_P:p_P),-->  | IP_Jb:p_Jb|IP_R:p_Ra  |
   |                          C(ClientHello)]  |           |           |
   |                    <--JPY[H(IP_P:p_P),--  | IP_R:p_Ra |IP_Jb:p_Jb |
   |                         C(ServerHello)]   |           |           |
   |      <--ServerHello--                     | IP_Ja:p_Ja|IP_P:p_P   |
   |              :                            |           |           |
   |              :                            |     :     |    :      |
   |                                           |     :     |    :      |
   |      --Finished-->                        | IP_P:p_P  |IP_Ja:p_Ja |
   |                    --JPY[H(IP_P:p_P),-->  | IP_Jb:p_Jb|IP_R:p_Ra  |
   |                          C(Finished)]     |           |           |
   |                    <--JPY[H(IP_P:p_P),--  | IP_R:p_Ra |IP_Jb:p_Jb |
   |                         C(Finished)]      |           |           |
   |      <--Finished--                        | IP_Ja:p_Ja|IP_P:p_P   |
   |              :                            |     :     |    :      |
   +-------------------------------------------+-----------+-----------+
   IP_P:p_P = Link-local IP address and port of the Pledge
   IP_R:p_Ra = Global IP address and join port of Registrar
   IP_Ja:p_Ja = Link-local IP address and join port of Join Proxy
   IP_Jb:p_Jb = Global IP address and port of Join Proxy

   JPY[H(),C()] = Join Proxy message with header H and content C


           Figure 3: constrained stateless joining message flow.

5.3.  Stateless Message structure

   The JPY message is constructed as a payload with medi-type
   aplication/cbor

   Header and Contents fields togther are one cbor array of 5 elements:

   1.  header field: containing a CBOR array [RFC7049] with the pledge
       IPv6 Link Local address as a cbor byte string, the pledge's UDP
       port number as a CBOR integer, the IP address family (IPv4/IPv6)
       as a cbor integer, and the proxy's ifindex or other identifier
       for the physical port as cbor integer.  The header field is not
       DTLS encrypted.

   2.  Content field: containing the DTLS encrypted payload as a CBOR
       byte string.




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   The join_proxy cannot decrypt the DTLS ecrypted payload and has no
   knowledge of the transported media type.

       JPY_message =
       [
          ip      : bstr,
          port    : int,
          family  : int,
          index   : int
          payload : bstr
       ]


               Figure 4: CDDL representation of JPY message

   The content fields are DTLS encrypted.  In CBOR diagnostic notation
   the payload JPY[H(IP_P:p_P)], will look like:

         [h'IP_p', p_P, family, ident, h'DTLS-content']

   Examples are shown in Appendix A.

6.  Comparison of stateless and statefull modes

   The stateful and stateless mode of operation for the Join Proxy have
   their advantages and disadvantages.  This section should enable to
   make a choice between the two modes based on the available device
   resources and network bandwidth.























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   +-------------+----------------------------+------------------------+
   | Properties  |         Stateful mode      |     Stateless mode     |
   +-------------+----------------------------+------------------------+
   | State       |The Join Proxy needs        | No information is      |
   | Information |additional storage to       | maintained by the Join |
   |             |maintain mapping between    | Proxy. Registrar needs |
   |             |the address and port number | to store the packet    |
   |             |of the pledge and those     | header.                |
   |             |of the Registrar.           |                        |
   +-------------+----------------------------+------------------------+
   |Packet size  |The size of the forwarded   |Size of the forwarded   |
   |             |message is the same as the  |message is bigger than  |
   |             |original message.           |the original,it includes|
   |             |                            |additional source and   |
   |             |                            |destination addresses.  |
   +-------------+----------------------------+------------------------+
   |Specification|The Join Proxy needs        |New JPY message to      |
   |complexity   |additional functionality    |encapsulate DTLS message|
   |             |to maintain state           |The Registrar           |
   |             |information, and modify     |and the Join Proxy      |
   |             |the source and destination  |have to understand the  |
   |             |addresses of the DTLS       |JPY message in order    |
   |             |handshake messages          |to process it.          |
   +-------------+----------------------------+------------------------+

         Figure 5: Comparison between stateful and stateless mode

7.  Discovery

   It is assumed that Join Proxy seamlessly provides a coaps connection
   between Pledge and coaps Registrar.  In particular this section
   replaces section 4.2 of [I-D.ietf-anima-bootstrapping-keyinfra].

   The discovery follows two steps:

   1.  The pledge is one hop away from the Registrar.  The pledge
       discovers the link-local address of the Registrar as described in
       {I-D.ietf-ace-coap-est}. From then on, it follows the BRSKI
       process as described in {I-D.ietf-ace-coap-est}, using link-local
       addresses.

   2.  The pledge is more than one hop away from a relevant Registrar,
       and discovers the link-local address of a Join Proxy.  The pledge
       then follows the BRSKI procedure using the link-local address of
       the Join Proxy.

   Once a pledge is enrolled, it may function as Join Proxy.  The Join
   Proxy functions are advertised as descibed below.  In principle, the



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   Join Proxy functions are offered via a "join" port, and not the
   standard coaps port.  Also the Registrar offer a "join" port to which
   the stateless join proxy sends the JPY message.  The Join Proxy and
   Registrar MUST show the extra join port number when reponding to the
   .well-known/core request addressed to the standard coap/coaps port.

   Three discovery cases are discussed: coap discovery, 6tisch discovery
   and GRASP discovery.

7.1.  Pledge discovery of Registrar

   The Pledge and Join Proxy are assumed to communicate via Link-Local
   addresses.

7.1.1.  CoAP discovery

   The discovery of the coaps Registrar, using coap discovery, by the
   Join Proxy follows section 6 of [I-D.ietf-ace-coap-est].  The
   extension to discover the additional port needed by the stateless
   proxy is described in Section 7.2.2 by using rt=brski-proxy.

7.1.2.  Autonomous Network

   In the context of autonomous networks, the Join Proxy uses the DULL
   GRASP M_FLOOD mechanism to announce itself.  Section 4.1.1 of
   [I-D.ietf-anima-bootstrapping-keyinfra] discusses this in more
   detail.  The Registrar announces itself using ACP instance of GRASP
   using M_FLOOD messages.  Autonomous Network Join Proxies MUST support
   GRASP discovery of Registrar as decribed in section 4.3 of
   [I-D.ietf-anima-bootstrapping-keyinfra] .

7.1.3.  6tisch discovery

   The discovery of Registrar by the pledge uses the enhanced beacons as
   discussed in [I-D.ietf-6tisch-enrollment-enhanced-beacon].

7.2.  Pledge discovers Join Proxy

7.2.1.  Autonomous Network

   The pledge MUST listen for GRASP M_FLOOD [I-D.ietf-anima-grasp]
   announcements of the objective: "AN_Proxy".  See section
   Section 4.1.1 [I-D.ietf-anima-bootstrapping-keyinfra] for the details
   of the objective.







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7.2.2.  CoAP discovery

   In the context of a coap network without Autonomous Network support,
   discovery follows the standard coap policy.  The Pledge can discover
   a Join Proxy by sending a link-local multicast message to ALL CoAP
   Nodes with address FF02::FD.  Multiple or no nodes may respond.  The
   handling of multiple responses and the absence of responses follow
   section 4 of [I-D.ietf-anima-bootstrapping-keyinfra].

   The presence and location of (path to) the Join Proxy resource are
   discovered by sending a GET request to "/.well-known/core" including
   a resource type (rt) parameter with the value "brski-proxy"
   [RFC6690].  Upon success, the return payload will contain the root
   resource of the Join Proxy resources.  It is up to the implementation
   to choose its root resource; throughout this document the example
   root resource /jp is used.  The example below shows the discovery of
   the presence and location of Join Proxy resources.

     REQ: GET coap://[FF02::FD]/.well-known/core?rt=brski-proxy

     RES: 2.05 Content
     <coaps://[IP_address]:jp-port/jp>; rt="brski-proxy"

   Port numbers are assumed to be the default numbers 5683 and 5684 for
   coap and coaps respectively (sections 12.6 and 12.7 of [RFC7252] when
   not shown in the response.  Discoverable port numbers are usually
   returned for Join Proxy resources in the <href> of the payload (see
   section 5.1 of [I-D.ietf-ace-coap-est]).

8.  Security Considerations

   It should be noted here that the contents of the CBOR map used to
   convey return address information is not protected.  However, the
   communication is between the Proxy and a known registrar are over the
   already secured portion of the network, so are not visible to
   eavesdropping systems.

   All of the concerns in [I-D.ietf-anima-bootstrapping-keyinfra]
   section 4.1 apply.  The pledge can be deceived by malicious AN_Proxy
   announcements.  The pledge will only join a network to which it
   receives a valid [RFC8366] voucher.

   If the proxy/Registrar was not over a secure network, then an
   attacker could change the cbor array, causing the pledge to send
   traffic to another node.  If the such scenario needed to be
   supported, then it would be reasonable for the Proxy to encrypt the
   CBOR array using a locally generated symmetric key.  The Registrar




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   would not be able to examine the result, but it does not need to do
   so.  This is a topic for future work.

9.  IANA Considerations

   This document needs to create a registry for key indices in the CBOR
   map.  It should be given a name, and the amending formula should be
   IETF Specification.

9.1.  Resource Type registry

   This specification registers a new Resource Type (rt=) Link Target
   Attributes in the "Resource Type (rt=) Link Target Attribute Values"
   subregistry under the "Constrained RESTful Environments (CoRE)
   Parameters" registry.

     rt="brski-proxy". This BRSKI resource is used to query and return
     the supported BRSKI resource using the additional BRSKI port of
     Join Proxy or Registrar.

10.  Acknowledgements

   Many thanks for the comments by Brian Carpenter.

11.  Contributors

   Sandeep Kumar, Sye loong Keoh, and Oscar Garcia-Morchon are the co-
   authors of the draft-kumar-dice-dtls-relay-02.  Their draft has
   served as a basis for this document.  Much text from their draft is
   copied over to this draft.

12.  Changelog

12.1.  00 to 01

   o  Registrar used throughout instead of EST server

   o  Emphasized additional Join Proxy port for Join Proxy and Registrar

   o  updated discovery accordingly

   o  updated stateless Join Proxy JPY header

   o  JPY header described with CDDL

   o  Example simplified and corrected





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12.2.  00 to 00

   o  copied from vanderstok-anima-constrained-join-proxy-05

13.  References

13.1.  Normative References

   [I-D.ietf-6tisch-enrollment-enhanced-beacon]
              Dujovne, D. and M. Richardson, "IEEE 802.15.4 Information
              Element encapsulation of 6TiSCH Join and Enrollment
              Information", draft-ietf-6tisch-enrollment-enhanced-
              beacon-14 (work in progress), February 2020.

   [I-D.ietf-ace-coap-est]
              Stok, P., Kampanakis, P., Richardson, M., and S. Raza,
              "EST over secure CoAP (EST-coaps)", draft-ietf-ace-coap-
              est-18 (work in progress), January 2020.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
              and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-45 (work in progress), November 2020.

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", draft-
              ietf-anima-constrained-voucher-09 (work in progress),
              November 2020.

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-15 (work in progress), July 2017.

   [I-D.ietf-core-multipart-ct]
              Fossati, T., Hartke, K., and C. Bormann, "Multipart
              Content-Format for CoAP", draft-ietf-core-multipart-ct-04
              (work in progress), August 2019.

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






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   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,
              <https://www.rfc-editor.org/info/rfc8366>.

13.2.  Informative References

   [I-D.kumar-dice-dtls-relay]
              Kumar, S., Keoh, S., and O. Garcia-Morchon, "DTLS Relay
              for Constrained Environments", draft-kumar-dice-dtls-
              relay-02 (work in progress), October 2014.

   [I-D.richardson-anima-state-for-joinrouter]
              Richardson, M., "Considerations for stateful vs stateless
              join router in ANIMA bootstrap", draft-richardson-anima-
              state-for-joinrouter-03 (work in progress), September
              2020.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <https://www.rfc-editor.org/info/rfc4944>.

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
              <https://www.rfc-editor.org/info/rfc6690>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/rfc6763>.

   [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,
              <https://www.rfc-editor.org/info/rfc6775>.



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   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/info/rfc7228>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <https://www.rfc-editor.org/info/rfc7252>.

Appendix A.  Stateless Proxy payload examples

   The examples show the get coaps://[192.168.1.200]:5965/est/crts to a
   Registrar.  The header generated between Client and registrar and
   from registrar to client are shown in detail.  The DTLS encrypted
   code is not shown.

   The request from Join Proxy to Registrar looks like:

      85                                   # array(5)
         50                                # bytes(16)
            00000000000000000000FFFFC0A801C8 #
         19 BDA7                           # unsigned(48551)
         0A                                # unsigned(10)
         00                                # unsigned(0)
         58 2D                             # bytes(45)
      <cacrts DTLS encrypted request>

   In CBOR Diagnostic:

       [h'00000000000000000000FFFFC0A801C8', 48551, 10, 0,
        h'<cacrts DTLS encrypted request>']

   The response is:

      85                                   # array(5)
         50                                # bytes(16)
            00000000000000000000FFFFC0A801C8 #
         19 BDA7                           # unsigned(48551)
         0A                                # unsigned(10)
         00                                # unsigned(0)
      59 026A                              # bytes(618)
         <cacrts DTLS encrypted response>



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   In CBOR diagnostic:

       [h'00000000000000000000FFFFC0A801C8', 48551, 10, 0,
       h'<cacrts DTLS encrypted response>']

Authors' Addresses

   Michael Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca


   Peter van der Stok
   vanderstok consultancy

   Email: consultancy@vanderstok.org


   Panos Kampanakis
   Cisco Systems

   Email: pkampana@cisco.com




























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