anima Working Group                                        M. Richardson
Internet-Draft                                  Sandelman Software Works
Intended status: Standards Track                         P. van der Stok
Expires: 26 March 2021                            vanderstok consultancy
                                                           P. Kampanakis
                                                           Cisco Systems
                                                       22 September 2020


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

Abstract

   This document defines a protocol to securely assign a pledge to an
   owner, using an intermediary node between pledge and owner.  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 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 26 March 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  . . . . . . . . . . . . . . . . . . . . . . . .   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  . . . . . . . . . . . . . . . . . .   6
     5.3.  Stateless Message structure . . . . . . . . . . . . . . .   8
   6.  Comparison of stateless and statefull modes . . . . . . . . .   9
   7.  Discovery . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Pledge discovery of Join Proxy  . . . . . . . . . . . . .  10
       7.1.1.  CoAP discovery  . . . . . . . . . . . . . . . . . . .  10
       7.1.2.  Autonomous Network  . . . . . . . . . . . . . . . . .  11
       7.1.3.  6tisch discovery  . . . . . . . . . . . . . . . . . .  11
     7.2.  Join Proxy discovers EST server . . . . . . . . . . . . .  11
       7.2.1.  Autonomous Network  . . . . . . . . . . . . . . . . .  11
       7.2.2.  CoAP discovery  . . . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Resource Type registry  . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  13
   12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.1.  01 to 02 . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.2.  00 to 01 . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.3.  00 to 00 . . . . . . . . . . . . . . . . . . . . . . . .  13
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     13.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Stateless Proxy payload examples . . . . . . . . . .  16
     A.1.  cacerts . . . . . . . . . . . . . . . . . . . . . . . . .  18
     A.2.  serverkeygen  . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20







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1.  Introduction

   Enrolment of new nodes into constrained networks with constrained
   nodes present is described in [I-D.ietf-anima-bootstrapping-keyinfra]
   ("BRSKI") and makes use of Enrolment over Secure Transport (EST)
   [RFC7030] with [RFC8366] vouchers to securely enroll devices.  BRSKI
   connects new devices ("pledges") to extended EST servers
   ("Registrars") via a Join Proxy.

   The specified solutions use https and may be too large in terms of
   code space or bandwidth required.  Constrained devices in 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 described as the "coaps" scheme.  A
   constrained version of EST, using Coap and DTLS, is described in
   [I-D.ietf-ace-coap-est].

   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 extended EST server.

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

   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.  The
   document standardizes the CoAP/DTLS (method 4).







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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.

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 is more than one hop away from the EST server (E) and not
   yet authenticated into the network.

   At this stage, 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 EST server (E) to authenticate and get
   the relevant system/network parameters.  If the Pledge (P) initiates
   a DTLS connection to the EST server 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
             |E |---- mesh  +--+        +--+
             |  |    \      |J |........|P |
             ++++     \-----|  |        |  |
          EST server        +--+        +--+
          Registrar       Join Proxy   Pledge
                                       "Joining" Device

                       Figure 1: multi-hop enrolment.

   Furthermore, the Pledge (P) may wish to establish a secure connection
   to the EST server (E) 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 EST server (E).  However, the Pledge (P)
   may be unaware of the IP address of the EST-server (E) to initiate a
   DTLS connection and perform authentication with.




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   A DTLS connection is required between Pledge and EST server.  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 EST Server.

5.  Join Proxy specification

   A Join Proxy can operate in two modes:

   *  Statefull mode

   *  Stateless mode

5.1.  Statefull Join Proxy

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

   Assume that the Pledge does not know the IP address of the EST Server
   it needs to contact.  In that situation, the Join Proxy must know the
   (configured or discovered) IP address of a BRSKI 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) as in the previous case by modifying both the source and
   destination addresses to forward the message to the intended EST
   Server.  The Join Proxy maintains a 4-tuple array to translate the
   DTLS messages received from the EST Server 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:















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   +------------+------------+-------------+--------------------------+
   | EST Client | Join Proxy | EST Server  |          Message         |
   |    (P)     |     (J)    |    (E)      | Src_IP:port | Dst_IP:port|
   +------------+------------+-------------+-------------+------------+
   |      --ClientHello-->                 |   IP_P:p_P  | IP_Ja:5684 |
   |                    --ClientHello-->   |   IP_Jb:p_Jb| IP_E:5684  |
   |                                       |             |            |
   |                    <--ServerHello--   |   IP_E: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_E:5684  |
   |                                       |             |            |
   |                      <--Finished--    |   IP_E: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_E:5684 = Global IP address and coaps port of EST Server
   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 EST
                    server address known to Join Proxy.

5.2.  Stateless Join Proxy

   The Join Proxy is stateless 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 joining device as a client attempts a DTLS connection to the
   EST server, 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 joining device 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 DTLS Client that can only use link-local addressing
   wants to contact a trusted end-point 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:

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

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

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

   The BRSKI server transiently stores the Header field information.
   The Registrar server uses the Contents field to execute the Registrar
   server 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 DTLS Client from the transient state stored
   earlier (which can now be discarded) 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 |    EST server |        Message        |
   |     (P)      |     (J)    |      (E)      |Src_IP:port|Dst_IP:port|
   +--------------+------------+---------------+-----------+-----------+
   |      --ClientHello-->                     | IP_P:p_P  |IP_Ja:5684 |
   |                    --JPY[H(IP_P:p_P),-->  | IP_Jb:p_Jb|IP_E:5684  |
   |                          C(ClientHello)]  |           |           |
   |                    <--JPY[H(IP_P:p_P),--  | IP_E:5684 |IP_Jb:p_Jb |
   |                         C(ServerHello)]   |           |           |
   |      <--ServerHello--                     | IP_Ja:5684|IP_P:p_P   |
   |              :                            |           |           |
   |              :                            |     :     |    :      |
   |                                           |     :     |    :      |
   |      --Finished-->                        | IP_P:p_P  |IP_Ja:5684 |
   |                    --JPY[H(IP_P:p_P),-->  | IP_Jb:p_Jb|IP_E:5684  |
   |                          C(Finished)]     |           |           |
   |                    <--JPY[H(IP_P:p_P),--  | IP_E:5684 |IP_Jb:p_Jb |
   |                         C(Finished)]      |           |           |
   |      <--Finished--                        | IP_Ja:5684|IP_P:p_P   |
   |              :                            |     :     |    :      |
   +-------------------------------------------+-----------+-----------+
   IP_P:p_P = Link-local IP address and port of the Pledge
   IP_E:5684 = Global IP address and coaps port of EST Server
   IP_Ja:5684 = Link-local IP address and coaps 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 media-type
   application/multipart-core specified in [I-D.ietf-core-multipart-ct].

   Header and Contents fields use different media formats:

   1.  header field: application/cbor containing a CBOR array [RFC7049]
       with the pledge IPv6 Link Local address as a 16-byte binary
       value, the pledge's UDP port number, if different from 5684, as a
       CBOR integer, and the proxy's ifindex or other identifier for the
       physical port on which the pledge is connected.  Header is not
       DTLS encrypted.

   2.  Content field: Any of the media types specified in
       [I-D.ietf-ace-coap-est] and [I-D.ietf-anima-constrained-voucher]
       dependent on the function that is requested:




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    * application/pkcs7-mime; smime-type=server-generated-key
    * application/pkcs7-mime; smime-type=certs-only
    * application/voucher-cms+cbor
    * application/voucher-cose+cbor
    * application/pkcs8
    * application/csrattrs
    * application/pkcs10
    * application/pkix-cert

   (XXX- add CDDL for CBOR array above)

   The content fields are DTLS encrypted.  In CBOR diagnostic notation
   the payload JPY[H(IP_P:p_P), with cf is content-format of DTLS-
   content, will look like:

         [ 60: [IP_p, p_P, ident]
           cf: 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                  |
   |             |the address and port number |                        |
   |             |of the pledge and those     |                        |
   |             |of the EST-server.          |                        |
   +-------------+----------------------------+------------------------+
   |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 EST server          |
   |             |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 4: Comparison between stateful and stateless mode

7.  Discovery

   It is assumed that Join Proxy seamlessly provides a coaps connection
   between Pledge and coaps EST-server.  An additional Registrar is
   needed to connect the Pledge to an http EST server, see section 8 of
   [I-D.ietf-ace-coap-est].  In particular this section replaces section
   4.2 of [I-D.ietf-anima-bootstrapping-keyinfra].

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

7.1.  Pledge discovery of Join Proxy

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

7.1.1.  CoAP discovery

   The discovery of the coaps EST server, using coap discovery, by the
   Join Proxy follows section 6 of [I-D.ietf-ace-coap-est].




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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 EST-server as decribed in section 4.3 of
   [I-D.ietf-anima-bootstrapping-keyinfra] .

7.1.3.  6tisch discovery

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

7.2.  Join Proxy discovers EST server

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.

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
     </jp>; rt="brski-proxy";ct=62





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   Port numbers, not returned in the example, are assumed to be the
   default numbers 5683 and 5684 for coap and coaps respectively
   (sections 12.6 and 12.7 of [RFC7252].  Discoverable port numbers MAY
   be returned 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
   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 EST resource is used to query and return
     the supported EST resource of a Join Proxy placed between Pledge
     and EST server.

10.  Acknowledgements

   Many thanks for the comments by Brian Carpenter.




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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.  01 to 02

   *  extended the discovery section

   *  removed inconsistencies from the the flow diagrams

   *  Improved readability of the examples.

   *  stateful configurations reduced to one

12.2.  00 to 01

   *  Added Contributors section

   *  Adapted content-formats to est-coaps formats

   *  Aligned examples with est-coaps examples

   *  Added statefull Proxy to stateless proxy

12.3.  00 to 00

   *  added payload examples in appendix

   *  discovery for three cases: AN, 6tisch and coaps

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", Work in Progress, Internet-Draft, draft-
              ietf-6tisch-enrollment-enhanced-beacon-14, 21 February
              2020, <http://www.ietf.org/internet-drafts/draft-ietf-
              6tisch-enrollment-enhanced-beacon-14.txt>.





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   [I-D.ietf-ace-coap-est]
              Stok, P., Kampanakis, P., Richardson, M., and S. Raza,
              "EST over secure CoAP (EST-coaps)", Work in Progress,
              Internet-Draft, draft-ietf-ace-coap-est-18, 6 January
              2020, <http://www.ietf.org/internet-drafts/draft-ietf-ace-
              coap-est-18.txt>.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
              and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", Work in Progress, Internet-
              Draft, draft-ietf-anima-bootstrapping-keyinfra-44, 21
              September 2020, <http://www.ietf.org/internet-drafts/
              draft-ietf-anima-bootstrapping-keyinfra-44.txt>.

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", Work in
              Progress, Internet-Draft, draft-ietf-anima-constrained-
              voucher-08, 13 July 2020, <http://www.ietf.org/internet-
              drafts/draft-ietf-anima-constrained-voucher-08.txt>.

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", Work in Progress,
              Internet-Draft, draft-ietf-anima-grasp-15, 13 July 2017,
              <http://www.ietf.org/internet-drafts/draft-ietf-anima-
              grasp-15.txt>.

   [I-D.ietf-core-multipart-ct]
              Fossati, T., Hartke, K., and C. Bormann, "Multipart
              Content-Format for CoAP", Work in Progress, Internet-
              Draft, draft-ietf-core-multipart-ct-04, 21 August 2019,
              <http://www.ietf.org/internet-drafts/draft-ietf-core-
              multipart-ct-04.txt>.

   [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>.



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   [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

   [duckling] Stajano, F. and R. Anderson, "The resurrecting duckling:
              security issues for ad-hoc wireless networks", 1999,
              <https://www.cl.cam.ac.uk/~fms27/papers/1999-StajanoAnd-
              duckling.pdf>.

   [I-D.kumar-dice-dtls-relay]
              Kumar, S., Keoh, S., and O. Garcia-Morchon, "DTLS Relay
              for Constrained Environments", Work in Progress, Internet-
              Draft, draft-kumar-dice-dtls-relay-02, 20 October 2014,
              <http://www.ietf.org/internet-drafts/draft-kumar-dice-
              dtls-relay-02.txt>.

   [I-D.richardson-anima-state-for-joinrouter]
              Richardson, M., "Considerations for stateful vs stateless
              join router in ANIMA bootstrap", Work in Progress,
              Internet-Draft, draft-richardson-anima-state-for-
              joinrouter-02, 25 January 2018, <http://www.ietf.org/
              internet-drafts/draft-richardson-anima-state-for-
              joinrouter-02.txt>.

   [pledge]   Dictionary.com, ., "Dictionary.com Unabridged", 2015,
              <http://dictionary.reference.com/browse/pledge>.

   [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>.





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   [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>.

   [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

   Examples are extensions of two examples shown in
   [I-D.ietf-ace-coap-est].  The following content formats are used:

   *  60: application/cbor

   *  62: application/multipart

   *  281: application/pkcs7-mime; smime-type=certs-only

   *  284: application/pkcs8

   *  286: application/pkcs10

   For presentation purposes the payloads are abbreviated as follows:

   cacrts request payload:

      <cacrts request payload> = <empty>

   cacrts response payload:








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      <cacrts response payload> =
      DTLS_encrypt(
      3082027b06092a864886f70d010702a082026c308202680201013100300b
      06092a864886f70d010701a082024e3082024a308201f0a0030201020209
      009189bcdf9c99244b300a06082a8648ce3d0403023067310b3009060355
      040613025553310b300906035504080c024341310b300906035504070c02
      4c4131143012060355040a0c0b4578616d706c6520496e63311630140603
      55040b0c0d63657274696669636174696f6e3110300e06035504030c0752
      6f6f74204341301e170d3139303130373130343034315a170d3339303130
      323130343034315a3067310b3009060355040613025553310b3009060355
      04080c024341310b300906035504070c024c4131143012060355040a0c0b
      4578616d706c6520496e6331163014060355040b0c0d6365727469666963
      6174696f6e3110300e06035504030c07526f6f742043413059301306072a
      8648ce3d020106082a8648ce3d03010703420004814994082b6e8185f3df
      53f5e0bee698973335200023ddf78cd17a443ffd8ddd40908769c55652ac
      2ccb75c4a50a7c7ddb7c22dae6c85cca538209fdbbf104c9a38184308181
      301d0603551d0e041604142495e816ef6ffcaaf356ce4adffe33cf492abb
      a8301f0603551d230418301680142495e816ef6ffcaaf356ce4adffe33cf
      492abba8300f0603551d130101ff040530030101ff300e0603551d0f0101
      ff040403020106301e0603551d1104173015811363657274696679406578
      616d706c652e636f6d300a06082a8648ce3d0403020348003045022100da
      e37c96f154c32ec0b4af52d46f3b7ecc9687ddf267bcec368f7b7f135327
      2f022047a28ae5c7306163b3c3834bab3c103f743070594c089aaa0ac870
      cd13b902caa1003100
      )

   serverkeygen request payload:

      <serverkeygen request payload> =
      DTLS_encrypt(
      3081cf3078020100301631143012060355040a0c0b736b67206578616d70
      6c653059301306072a8648ce3d020106082a8648ce3d030107034200041b
      b8c1117896f98e4506c03d70efbe820d8e38ea97e9d65d52c8460c5852c5
      1dd89a61370a2843760fc859799d78cd33f3c1846e304f1717f8123f1a28
      4cc99fa000300a06082a8648ce3d04030203470030440220387cd4e9cf62
      8d4af77f92ebed4890d9d141dca86cd2757dd14cbd59cdf6961802202f24
      5e828c77754378b66660a4977f113cacdaa0cc7bad7d1474a7fd155d090d
      )

   serverkeygen response payload:











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      <serverkeygen response payload> =
      DTLS_encrypt(
      84                                   # array(4)
      19 011C                              # unsigned(284)
      58 8A                                # bytes(138)
      308187020100301306072a8648ce3d020106082a8648ce3d030107046d30
      6b02010104200b9a67785b65e07360b6d28cfc1d3f3925c0755799deeca7
      45372b01697bd8a6a144034200041bb8c1117896f98e4506c03d70efbe82
      0d8e38ea97e9d65d52c8460c5852c51dd89a61370a2843760fc859799d78
      cd33f3c1846e304f1717f8123f1a284cc99f
      19 0119                              # unsigned(281)
      59 01D3                              # bytes(467)
      308201cf06092a864886f70d010702a08201c0308201bc0201013100300b
      06092a864886f70d010701a08201a23082019e30820143a0030201020208
      126de8571518524b300a06082a8648ce3d04030230163114301206035504
      0a0c0b736b67206578616d706c65301e170d313930313039303835373038
      5a170d3339303130343038353730385a301631143012060355040a0c0b73
      6b67206578616d706c653059301306072a8648ce3d020106082a8648ce3d
      030107034200041bb8c1117896f98e4506c03d70efbe820d8e38ea97e9d6
      5d52c8460c5852c51dd89a61370a2843760fc859799d78cd33f3c1846e30
      4f1717f8123f1a284cc99fa37b307930090603551d1304023000302c0609
      6086480186f842010d041f161d4f70656e53534c2047656e657261746564
      204365727469666963617465301d0603551d0e04160414494be598dc8dbc
      0dbc071c486b777460e5cce621301f0603551d23041830168014494be598
      dc8dbc0dbc071c486b777460e5cce621300a06082a8648ce3d0403020349
      003046022100a4b167d0f9add9202810e6bf6a290b8cfdfc9b9c9fea2cc1
      c8fc3a464f79f2c202210081d31ba142751a7b4a34fd1a01fcfb08716b9e
      b53bdaadc9ae60b08f52429c0fa1003100
      )

A.1.  cacerts

   The request from Join Proxy to EST-server looks like:

       Get coaps://192.0.2.1/est/crts
       (Accept: 62)
       (Content-format: 62)
       payload =
       82                    # array(2)
       18 3C                 # unsigned(60)
       83                    # array(3)
       69                    # text(9)
            464538303A3A414238 # "FE80::AB8"
       19 237D               # unsigned(9085)
       65                    # text(5)
            6964656E74       # "ident"

   In CBOR Diagnostic:



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       payload = [60, ["FE80::AB8", 9085, "ident"]]

   The response will then be:

        2.05 Content
        (Content-format: 62)
          Payload =
        84                                # array(4)
        18 3C                             # unsigned(60)
        83                                # array(3)
        69                                # text(9)
            464538303A3A414238            # "FE80::AB8"
        19 237D                           # unsigned(9085)
        65                                # text(5)
            6964656E74                    # "ident"
        19 0119                           # unsigned(281)
        59 027F                           # bytes(639)
        <cacrts response payload>
        ]

   In CBOR diagnostic:

       payload = [60, ["FE80::AB8", 9085, "ident"],
                  62, h'<cacrts response payload>']

A.2.  serverkeygen

   The request from Join Proxy to EST-server looks like:

       Get coaps://192.0.2.1/est/skg
       (Accept: 62)
       (Content-Format: 62)
         Payload =
       83                                # array(4)
       18 3C                             # unsigned(60)
       83                                # array(3)
       69                                # text(9)
            464538303A3A414238           # "FE80::AB8"
       19 237D                           # unsigned(9085)
       65                                # text(5)
            6964656E74                   # "ident"
       19 011E                           # unsigned(286)
       58 D2                             # bytes(210)
       <serverkeygen request payload>

   In CBOR diagnostic:





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       payload = [60, ["FE80::AB8", 9085, "ident"],
                  286, h'<serverkeygen request payload>']

   The response will then be:

        2.05 Content
        (Content-format: 62)
          Payload =
        83                                # array(4)
        18 3C                             # unsigned(60)
        83                                # array(3)
        69                                # text(9)
            464538303A3A414238            # "FE80::AB8"
        19 237D                           # unsigned(9085)
        65                                # text(5)
            6964656E74                    # "ident"
        19 011E                           # unsigned(286)
        59 0269                           # bytes(617)
        <serverkeygen response payload>

   In CBOR diagnostic:

       payload = [60, ["FE80::AB8", 9085, "ident"],
                  286, h'<serverkeygen response payload>']

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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