anima Working Group                                        M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Standards Track                         P. van der Stok
Expires: February 11, 2022                        vanderstok consultancy
                                                           P. Kampanakis
                                                           Cisco Systems
                                                         August 10, 2021


           Constrained Join Proxy for Bootstrapping Protocols
               draft-ietf-anima-constrained-join-proxy-04

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 [RFC8995] by replacing the Circuit-
   proxy between Pledge and Registrar by a stateless/stateful
   constrained (CoAP) Join Proxy.  It relays join traffic from the
   Pledge to the Registrar.

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 February 11, 2022.

Copyright Notice

   Copyright (c) 2021 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



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   (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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   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  . . . . . . . . . . . . . . . . . .   7
     5.3.  Stateless Message structure . . . . . . . . . . . . . . .   8
   6.  Comparison of stateless and statefull modes . . . . . . . . .   9
   7.  Discovery . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Join-Proxy discovers 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 . . . . . . . . . . . . . . .  12
       7.2.1.  Autonomous Network  . . . . . . . . . . . . . . . . .  12
       7.2.2.  CoAP discovery  . . . . . . . . . . . . . . . . . . .  12
       7.2.3.  6tisch discovery  . . . . . . . . . . . . . . . . . .  12
     7.3.  Join Proxy discovers Registrar join port  . . . . . . . .  12
       7.3.1.  CoAP discovery  . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Resource Type registry  . . . . . . . . . . . . . . . . .  13
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  14
   12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     12.1.  03 to 04 . . . . . . . . . . . . . . . . . . . . . . . .  14
     12.2.  02 to 03 . . . . . . . . . . . . . . . . . . . . . . . .  14
     12.3.  01 to 02 . . . . . . . . . . . . . . . . . . . . . . . .  14
     12.4.  00 to 01 . . . . . . . . . . . . . . . . . . . . . . . .  14
     12.5.  00 to 00 . . . . . . . . . . . . . . . . . . . . . . . .  15
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     13.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  Stateless Proxy payload examples . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18





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1.  Introduction

   Enrolment of new nodes into networks with enrolled nodes present is
   described in [RFC8995] ("BRSKI") and makes use of Enrolment over
   Secure Transport (EST) [RFC7030] with [RFC8366] vouchers to securely
   enroll devices.  BRSKI connects a new joining device (called Pledge)
   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]
   extends [I-D.ietf-ace-coap-est] with BRSKI artefacts such as voucher,
   request voucher, and the protocol extensions for constrained Pledges.

   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 Pledge will not be IP routable until it is
   authenticated to the network.  A new Pledge can only initially use a
   link-local IPv6 address to communicate with a neighbour on the same
   link [RFC6775] until it receives the necessary network configuration
   parameters.  However, before the Pledge can receive these
   configuration parameters, it needs to authenticate itself to the
   network to which it connects.

   During enrollment, 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 Pledge and Registrar to relay DTLS messages
   between Pledge and Registrar.  Two versions of the Join Proxy are
   specified:

   1 A stateful Join Proxy that locally stores IP addresses
     during the connection.
   2 A stateless Join Proxy that where the connection state
    is stored in the messages.

   This document is very much inspired by text published earlier in
   [I-D.kumar-dice-dtls-relay].



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   [I-D.richardson-anima-state-for-joinrouter] outlined the various
   options for building a join proxy.  [RFC8995] 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
   Registrar/Coordinator (JRC), Manufacturer Authorized Signing
   Authority (MASA), Pledge, Trust of First Use (TOFU), and Voucher.

   The term "installation network" refers to all devices in the
   installation and the network connections between them.  The term
   "installation IP_address" refers to the set of adresses which are
   routable over the whole installation network.

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 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, the Pledge 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 to authenticate and get the relevant
   system/network parameters.  If the Pledge (P), knowing the IP-address
   of the Registrar, initiates a DTLS connection to the Registrar, 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 from the Registrar.











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



                      Figure 1: multi-hop enrolment.

   Without routing the Pledge (P) cannot establish a secure connection
   to the Registrar (R) over multiple hops in the network.

   Furthermore, the Pledge (P) cannot discover the IP address of the
   Registrar (R) over multiple hops to initiate a DTLS connection and
   perform authentication.

   To overcome the problems with non-routability of DTLS packets and/or
   discovery of the destination address of the Registrar, the Join Proxy
   is introduced.  This Join Proxy functionality is configured into all
   authenticated devices in the network which may act as a Join Proxy
   for Pledges.  The Join Proxy allows for routing of the packets from
   the Pledge using IP routing to the intended Registrar.  An
   authenticated Join Proxy can discover the routable IP address of the
   Registrar over multiple hops.  The following Section 5 specifies the
   two Join Proxy modes.  A comparison is presented in Section 6.

5.  Join Proxy specification

   A Join Proxy can operate in two modes:

   o  Statefull mode

   o  Stateless mode

   A Join Proxy MUST implement one of the two modes.  A Join Proxy MAY
   implement both, with an unspecified mechanism to switch between the
   two modes.

5.1.  Statefull Join Proxy

   In stateful mode, the Join Proxy forwards the DTLS messages to the
   Registrar.

   Assume that the Pledge does not know the IP address of the Registrar
   it needs to contact.  The Join Proxy has has been enrolled via the
   Registrar and learns the IP address and port of the Registrar, for



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   example by using the discovery mechanism described in Section 7.  The
   Pledge first discovers (see Section 7) and selects the most
   appropriate Join Proxy.  (Discovery can also be based upon [RFC8995]
   section 4.1, or via DNS-SD service discovery [RFC6763]).  The Pledge
   initiates its request as if the Join Proxy is the intended Registrar.
   The Join Proxy receives the message at a discoverable "Join" port.
   The Join Proxy constructs an IP packet by copying the DTLS payload
   from the message received from the Pledge, and provides 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 back to the
   Pledge.

   In Figure 2 the various steps of the message flow are shown, with
   5684 being the standard coaps port:

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

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








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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.

   If an untrusted Pledge that can only use link-local addressing wants
   to contact a trusted Registrar, and the Registrar is more than one
   hop away, it sends its DTLS messages to the Join Proxy.

   When a Pledge attempts a DTLS connection to the Join Proxy, 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 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 its Registrar of choice.

   The Join Proxy sends a "new" JPY message which includes the DTLS data
   as payload.

   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 payload.

   On receiving the JPY message, the Registrar (or proxy) 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 payload.

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





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   In this scenario, both the Registrar and the Join Proxy use
   discoverable "Join" ports, which may be the default ports.

   The Figure 3 depicts the message flow diagram:

   +--------------+------------+---------------+-----------------------+
   |    Pledge    | 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   |
   |              :                            |           |           |
   |          [ DTLS messages ]                |     :     |    :      |
   |              :                            |     :     |    :      |
   |      --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 = Routable 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 = Routable 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 media-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




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       for the physical port as cbor integer.  The header field is not
       DTLS encrypted.

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

   The join_proxy cannot decrypt the DTLS 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-payload']

   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 IP-addresses |
   +-------------+----------------------------+------------------------+
   |Specification|The Join Proxy needs        |New JPY message to      |
   |complexity   |additional functionality    |encapsulate DTLS payload|
   |             |to maintain state           |The Registrar           |
   |             |information, and specify    |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.          |
   +-------------+----------------------------+------------------------+
   | Ports       | Join Proxy needs           |Join Proxy and Registrar|
   |             | discoverable "Join" port   |need discoverable       |
   |             |                            | "Join" ports           |
   +-------------+----------------------------+------------------------+


         Figure 5: Comparison between stateful and stateless mode

7.  Discovery

   It is assumed that Join Proxy seamlessly provides a coaps connection
   between Pledge and Registrar.  In particular this section replaces
   section 4.1 of [RFC8995].

   The discovery follows two steps with two alternatives for step 1:

   1.  Two alternatives:

   a.  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] and
   [I-D.ietf-anima-constrained-voucher], using link-local addresses.





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

   1.  Once enrolled, the Join Proxy discovers the join port of the
       Registrar.

   Once a Pledge is enrolled, it may function as Join Proxy.  The Join
   Proxy functions are advertised as descibed below.  In principle, the
   Join Proxy functions are offered via a "join" port, and not the
   standard coaps port.  Also the Registrar offers a "join" port to
   which the stateless join proxy sends the JPY message.  The Join Proxy
   and Registrar show the extra join port number when reponding to a
   /.well-known/core discovery request addressed to the standard coap/
   coaps port.

   Three discovery cases are discussed: Join_proxy discovers Registrar,
   Pledge discovers Registrar, and Pledge discovers Join-proxy.  Each
   discovery case considers threa alternatives: coap discovery, 6tisch
   discovery and GRASP discovery.

7.1.  Join-Proxy discovers Registrar

   In this section, the Pledge and Join Proxy are assumed to communicate
   via Link-Local addresses.  This section describes the discovery of
   the Registrar by the Join-Proxy.

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].

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
   [RFC8995] 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 [RFC8995] .

7.1.3.  6tisch discovery

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





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7.2.  Pledge discovers Join Proxy

7.2.1.  Autonomous Network

   The Pledge MUST listen for GRASP M_FLOOD [RFC8990] announcements of
   the objective: "AN_Proxy".  See section Section 4.1.1 [RFC8995] for
   the details of the objective.

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 [RFC8995].

   The join port of the Join Proxy is 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 join port.

   The example below shows the discovery of the join port of the Join
   Proxy.

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

     RES: 2.05 Content
     <coaps://[IP_address]:join-port>; 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]).

7.2.3.  6tisch discovery

   Not applicable.

7.3.  Join Proxy discovers Registrar join port

7.3.1.  CoAP discovery

   The stateless Join Proxy can discover the join port of the Registrar
   by sending a GET request to "/.well-known/core" including a resource
   type (rt) parameter with the value "join-proxy" [RFC6690].  Upon




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   success, the return payload will contain the join Port of the
   Registrar.

     REQ: GET coap://[IP_address]/.well-known/core?rt=join-proxy

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

   The 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 [RFC8995] section 4.1 apply.  The Pledge can
   be deceived by malicious Join_Proxy announcements.  The Pledge will
   only join a network to which it receives a valid [RFC8366] voucher
   [I-D.ietf-anima-constrained-voucher].

   If the communicatione between Join-Proxy and Registrar passed over an
   unsecure 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 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.






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

     rt="join-proxy". This BRSKI resource is used to query and return
     the supported BRSKI port of the Registrar.

10.  Acknowledgements

   Many thanks for the comments by Brian Carpenter and Esko Dijk.

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.  03 to 04

   * mail address and reference

12.2.  02 to 03

   * Terminology updated
   * Several clarifications on discovery and routability
   * DTLS payload introduced

12.3.  01 to 02

   o  Discovery of Join Proxy and Registrar ports

12.4.  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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12.5.  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]
              (editor), D. D. and M. Richardson, "Encapsulation of
              6TiSCH Join and Enrollment Information Elements", draft-
              ietf-6tisch-enrollment-enhanced-beacon-14 (work in
              progress), February 2020.

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

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P. V. D., Kampanakis, P., and E.
              Dijk, "Constrained Voucher Artifacts for Bootstrapping
              Protocols", draft-ietf-anima-constrained-voucher-13 (work
              in progress), July 2021.

   [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>.

   [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>.





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   [RFC8990]  Bormann, C., Carpenter, B., Ed., and B. Liu, Ed., "GeneRic
              Autonomic Signaling Protocol (GRASP)", RFC 8990,
              DOI 10.17487/RFC8990, May 2021,
              <https://www.rfc-editor.org/info/rfc8990>.

   [RFC8995]  Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
              and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995,
              May 2021, <https://www.rfc-editor.org/info/rfc8995>.

13.2.  Informative References

   [I-D.kumar-dice-dtls-relay]
              Kumar, S. S., Keoh, S. L., 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. C., "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>.

   [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>.





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   [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 request "GET coaps://192.168.1.200:5965/est/
   crts" to a Registrar.  The header generated between Join-Proxy and
   Registrar and from Registrar to Join-Proxy are shown in detail.  The
   DTLS payload is not shown.

   The request from Join Proxy to Registrar looks like:

      85                                   # array(5)
         50                                # bytes(16)
            FE800000000000000000FFFFC0A801C8 #
         19 BDA7                           # unsigned(48551)
         0A                                # unsigned(10)
         00                                # unsigned(0)
         58 2D                             # bytes(45)
      <cacrts DTLS encrypted request>

   In CBOR Diagnostic:

       [h'FE800000000000000000FFFFC0A801C8', 48551, 10, 0,
        h'<cacrts DTLS encrypted request>']

   The response is:

      85                                   # array(5)
         50                                # bytes(16)
            FE800000000000000000FFFFC0A801C8 #
         19 BDA7                           # unsigned(48551)
         0A                                # unsigned(10)
         00                                # unsigned(0)
      59 026A                              # bytes(618)
         <cacrts DTLS encrypted response>

   In CBOR diagnostic:

       [h'FE800000000000000000FFFFC0A801C8', 48551, 10, 0,
       h'<cacrts DTLS encrypted response>']



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Authors' Addresses

   Michael Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca


   Peter van der Stok
   vanderstok consultancy

   Email: stokcons@bbhmail.nl


   Panos Kampanakis
   Cisco Systems

   Email: pkampana@cisco.com

































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