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

Versions: 00 01 02 03

CoRE Working Group                                             M. Tiloca
Internet-Draft                                                   RISE AB
Intended status: Standards Track                              C. Amsuess
Expires: January 6, 2020
                                                         P. van der Stok
                                                              Consultant
                                                           July 05, 2019


      Discovery of OSCORE Groups with the CoRE Resource Directory
                 draft-tiloca-core-oscore-discovery-03

Abstract

   Group communication over the Constrained Application Protocol (CoAP)
   can be secured by means of Object Security for Constrained RESTful
   Environments (OSCORE).  At deployment time, devices may not know the
   exact OSCORE groups to join, the respective Group Manager, or other
   information required to perform the joining process.  This document
   describes how a CoAP endpoint can use the CoRE Resource Directory to
   discover OSCORE groups and acquire information to join them through
   the respective Group Manager.  A given OSCORE group may protect
   multiple application groups, which are separately announced in the
   Resource Directory as sets of endpoints sharing a pool of resources.
   This approach is consistent with, but not limited to, the joining of
   OSCORE groups based on the ACE framework for Authentication and
   Authorization in constrained environments.

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 January 6, 2020.







Tiloca, et al.           Expires January 6, 2020                [Page 1]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


Copyright Notice

   Copyright (c) 2019 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
   (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
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Registration Resource for Group Managers  . . . . . . . . . .   5
   3.  Registration of Group Manager Endpoints . . . . . . . . . . .   6
   4.  Addition and Update of OSCORE Groups  . . . . . . . . . . . .   8
   5.  Discovery of OSCORE Groups  . . . . . . . . . . . . . . . . .   9
     5.1.  Discovery Example #1  . . . . . . . . . . . . . . . . . .  10
     5.2.  Discovery Example #2  . . . . . . . . . . . . . . . . . .  11
   6.  Use Case Example With Full Discovery  . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  Resource Types  . . . . . . . . . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  18
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   A set of CoAP endpoints constitutes an application group by sharing a
   common pool of resources.  The members of an application group may be
   members of a given security group, by sharing a common set of keying
   material to secure group communication.

   The Constrained Application Protocol (CoAP) [RFC7252] supports group
   communication over IP multicast
   [RFC7390][I-D.dijk-core-groupcomm-bis] to improve efficiency and
   latency of communication and reduce bandwidth requirements.  The
   document Object Security for Constrained RESTful Environments
   (OSCORE) [I-D.ietf-core-object-security] describes how to achieve



Tiloca, et al.           Expires January 6, 2020                [Page 2]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   end-to-end security for CoAP messages through CBOR Object Signing and
   Encryption (COSE) [RFC8152].

   In particular, [I-D.ietf-core-oscore-groupcomm] specifies how OSCORE
   protects CoAP messages in group communication contexts, so enabling
   OSCORE groups as security groups.  Typically, one application group
   relies on exactly one OSCORE group, while a same OSCORE group may be
   used by multiple application groups at the same time.

   A CoAP endpoint joins an OSCORE group via a Group Manager (GM), in
   order to get the necessary group keying material.  As in
   [I-D.ietf-ace-key-groupcomm-oscore], the joining process can be based
   on the ACE framework for Authentication and Authorization in
   constrained environments [I-D.ietf-ace-oauth-authz], with the joining
   endpoint and the GM acting as ACE Client and Resource Server,
   respectively.  That is, the joining endpoint accesses the join
   resource associated with the OSCORE group of interest and exported by
   the GM.

   Typically, devices are equipped with a static X509 IDevID certificate
   installed at manufacturing time.  This certificate is used at
   deployment time during an enrollment process that provides the device
   with an Operational Certificate, possibly updated during the device
   lifetime.  In the presence of secure group communication for CoAP,
   such an Operational Certificate may be accompanied by information
   required to join OSCORE groups.  This especially includes a reference
   to the join resources to access at the respective GMs.

   However, it is usually impossible to provide such precise information
   to freshly deployed devices as part of their (early) Operational
   Certificate.  This can be due to a number of reasons: (1) the OSCORE
   group(s) to join and the responsible GM(s) are generally unknown at
   manufacturing time; (2) an OSCORE group of interest is created, or
   the responsible GM is deployed, only after the device is enrolled and
   fully operative in the network; and (3) information related to
   existing OSCORE groups or to their GMs has been changed.  This
   requires a method for CoAP endpoints to dynamically discover OSCORE
   groups and their GM, and to retrieve valid information about deployed
   groups.

   This specification describes how CoAP endpoints can use the CoRE
   Resource Directory (RD) [I-D.ietf-core-resource-directory] for
   discovering an OSCORE group and retrieving the information required
   to join that group through a given GM.  In principle, the GM
   registers as an endpoint with the RD.  The corresponding registration
   resource includes one link for each OSCORE group under that GM,
   specifying the path to the related join resource.




Tiloca, et al.           Expires January 6, 2020                [Page 3]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   More information about the OSCORE group is stored in the target
   attributes of the respective link.  This especially includes the
   identifiers of the application groups which use that OSCORE group.
   This enables a lookup of those application groups at the Resource
   Directory, where they are separately announced by a Commissioning
   Tool (see Appendix A of [I-D.ietf-core-resource-directory]).

   When querying the RD for OSCORE groups, a CoAP endpoint can further
   benefit of the CoAP Observe Option [RFC7641].  This enables the
   reception of notifications about the creation of new OSCORE groups or
   the updates concerning existing groups.  Thus, it facilitates the
   early deployment of CoAP endpoints, i.e. even before the GM is
   deployed and OSCORE groups are created.

   The approach in this document is consistent with, but not limited to,
   the joining of OSCORE groups in [I-D.ietf-ace-key-groupcomm-oscore].

1.1.  Terminology

   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.

   This specification requires readers to be familiar with the terms and
   concepts discussed in [I-D.ietf-core-resource-directory] and
   [RFC6690].  Readers should also be familiar with the terms and
   concepts discussed in [RFC7252], [I-D.ietf-core-oscore-groupcomm] and
   [I-D.ietf-ace-key-groupcomm-oscore].

   Terminology for constrained environments, such as "constrained
   device" and "constrained-node network", is defined in [RFC7228].

   This document also refers to the following terminology.

   o  OSCORE group: a set of CoAP endpoints that share one OSCORE Common
      Security Context to protect group communication as described in
      [I-D.ietf-core-oscore-groupcomm].  Consequently, an OSCORE group
      acts as security group for all its members.

   o  Application group: a set of CoAP endpoints that share a set of
      common resources.  Application groups are announced in the RD by a
      Commissioning Tool, according to the RD-Groups usage pattern (see
      Appendix A of [I-D.ietf-core-resource-directory]).  An application
      group can be associated with a single OSCORE group, while multiple
      application groups can use the same OSCORE group.  Application
      groups share resources by definition.  Any two application groups



Tiloca, et al.           Expires January 6, 2020                [Page 4]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


      associated to the same OSCORE group do not share any same
      resource.

   o  Zeroed-epoch Group ID: this refers to the Group ID of an OSCORE
      group as stored in the RD.  The structure of such a stored Group
      ID is as per Appendix C of [I-D.ietf-core-oscore-groupcomm], with
      the "Group Epoch" part immutable and set to zero.

2.  Registration Resource for Group Managers

   With reference to Figure 3 of [I-D.ietf-core-resource-directory], a
   Group Manager (GM) registers as an endpoint with the CoRE Resource
   Directory (RD).  The registration includes the links to the "join
   resources" located at the GM, and associated to the OSCORE groups
   administrated by that GM.

   In particular, each link to a join resource includes:

   o  "target": URI of the join resource at the GM.

   o  target attributes, including:

      *  Resource Type (rt) with the value "core.osc.j" defined in
         Section 8.1 of this specification.

      *  The zeroed-epoch Group ID of the OSCORE group.

      *  One target attribute for each application group associated with
         the OSCORE group, specifying the name of that application
         group.

      *  The algorithm used to countersign messages in the OSCORE group.

      *  The elliptic curve (if applicable) for the algorithm used to
         countersign messages in the OSCORE group.

      *  The key type of countersignature keys used to countersign
         messages in the OSCORE group.

      *  The encoding of public keys used in the OSCORE group.

      *  The AEAD algorithm used in the OSCORE group.

      *  The HKDF algorithm used in the OSCORE group.







Tiloca, et al.           Expires January 6, 2020                [Page 5]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


3.  Registration of Group Manager Endpoints

   During deployment, a GM finds the RD as described in Section 4 of
   [I-D.ietf-core-resource-directory].  Afterwards, the GM registers as
   an endpoint with the RD, as described in Section 5 of
   [I-D.ietf-core-resource-directory].

   When doing so, the GM MUST also register all the join resources it
   has at that point in time, i.e. one for each of its OSCORE groups.

   For each registered join resource, the GM MUST specify the following
   parameters in the payload of the registration request.

   o  'rt' = "core.osc.j" (see Section 8.1).

   o  'oscore-gid', specifying the zeroed-epoch Group ID of the OSCORE
      group of interest.  This parameter MUST specify a single value.

   o  'app-gp', specifying the name(s) of the application group(s)
      associated to the OSCORE group of interest.  This parameter MAY be
      included multiple times, and each occurrence MUST specify the name
      of one application group.  A same application group MUST NOT be
      specified multiple times.

   Also, for each registered join resource, the GM MAY specify the
   following parameters in the payload of the registration request.

   o  'cs_alg', specifying the algorithm used to countersign messages in
      the OSCORE group.  If present, this parameter MUST specify a
      single value, which is taken from the 'Name' column of the "COSE
      Algorithms" Registry defined in [RFC8152].

   o  'cs_crv', specifying the elliptic curve (if applicable) for the
      algorithm used to countersign messages in the OSCORE group.  If
      present, this parameter MUST specify a single value, which is
      taken from the 'Name' column of the "COSE Elliptic Curve" Registry
      defined in [RFC8152].

   o  'cs_kty', specifying the key type of countersignature keys used to
      countersign messages in the OSCORE group.  If present, this
      parameter MUST specify a single value, which is taken from the
      'Name' column of the "COSE Key Types" Registry defined in
      [RFC8152].

   o  'cs_kenc', specifying the encoding of the public keys used in the
      OSCORE group.  If present, this parameter MUST specify a single
      value, which is taken from the 'Name' column of Figure 2 in
      [I-D.ietf-ace-key-groupcomm-oscore], as registered in the "ACE



Tiloca, et al.           Expires January 6, 2020                [Page 6]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


      Public Key Encoding" Registry defined in
      [I-D.ietf-ace-key-groupcomm].

   o  'alg', specifying the AEAD algorithm used in the OSCORE group.  If
      present, this parameter MUST specify a single value, which is
      taken from the 'Name' column of the "COSE Algorithms" Registry
      defined in [RFC8152].

   o  'hkdf', specifying the HKDF algorithm used in the OSCORE group.
      If present, this parameter MUST specify a single value, which is
      taken from the 'Name' column of the "COSE Algorithms" Registry
      defined in [RFC8152].

   A CoAP endpoint that queries the RD to discover OSCORE groups and
   their join resource to access (see Section 5) would benefit from the
   link target attributes above as follows.

   o  The values of 'cs_alg', 'cs_crv', 'cs_kty' and 'cs_kenc' related
      to a join resource provide an early knowledge of the format and
      encoding of public keys used in the OSCORE group.  Thus, the CoAP
      endpoint does not need to ask the GM for this information as a
      preliminary step before the join process, or to perform a trial-
      and-error exchange with the GM.  Hence, the CoAP endpoint is able
      to provide the GM with its own public key in the correct expected
      format and encoding at the very first step of the join process.

   o  The values of 'cs_alg', 'alg' and 'hkdf' related to a join
      resource provide an early knowledge of the algorithms used in the
      OSCORE group.  Thus, the CoAP endpoint is able to decide whether
      to actually proceed with the join process, depending on its
      support for the indicated algorithms.

   The GM SHOULD NOT use the Simple Registration approach described in
   Section 5.1 of [I-D.ietf-core-resource-directory].

   The example below shows a GM with endpoint name "gm1" and address
   2001:db8::ab that registers with the RD.  The GM specifies the value
   of the 'oscore-gid' parameter for accessing the OSCORE group with
   zeroed-epoch Group ID "feedca570000" and used by the application
   group with name "group1" specified with the value of the 'app-gp'
   parameter.  The countersignature algorithm used in the OSCORE group
   is EdDSA, with elliptic curve Ed25519 and keys of type OKP.  Public
   keys used in the OSCORE group are encoded as COSE Keys [RFC8152].

   Request: GM -> RD






Tiloca, et al.           Expires January 6, 2020                [Page 7]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Req: POST coap://rd.example.com/rd?ep=gm1
   Content-Format: 40
   Payload:
   </join/feedca570000>;ct=41;rt="core.osc.j";oscore-gid="feedca570000";
                        app-gp="group1";cs_alg="EdDSA";cs_crv="Ed25519";
                        cs_kty="OKP";cs_kenc="COSE_Key"

   Response: RD -> GM

   Res: 2.01 Created
   Location-Path: /rd/4521

4.  Addition and Update of OSCORE Groups

   The GM is responsible to refresh the registration of all its join
   resources in the RD.  This means that the GM has to update the
   registration within its lifetime as per Section 5.3.1 of
   [I-D.ietf-core-resource-directory], and has to change the content of
   the registration when a join resource is added/removed or if its
   target attributes have to be changed, such as in the following cases.

   o  The GM creates a new OSCORE group and starts exporting the related
      join resource.

   o  The GM dismisses an OSCORE group and stops exporting the related
      join resource.

   o  Information related to an existing OSCORE group changes, e.g. the
      list of associated application groups.

   To perform an update of its registrations, the GM can re-register
   with the RD and fully specify all links to its join resources with
   their target attributes.

   The example below shows how the GM from Section 3 re-registers with
   the RD.  When doing so, it specifies:

   o  The same previous join resource associated to the OSCORE group
      with zeroed-epoch Group ID "feedca570000".

   o  An additional join resource associated to the OSCORE group with
      zeroed-epoch Group ID "ech0ech00000" and used by the application
      group "group2".

   o  A third join resource associated with the OSCORE group with
      zeroed-epoch Group ID "abcdef120000" and used by two application
      groups, namely "group3" and "group4".




Tiloca, et al.           Expires January 6, 2020                [Page 8]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Request: GM -> RD

   Req: POST coap://rd.example.com/rd?ep=gm1
   Content-Format: 40
   Payload:
   </join/feedca570000>;ct=41;rt="core.osc.j";oscore-gid="feedca570000";
                        app-gp="group1";cs_alg="EdDSA";cs_crv="Ed25519";
                        cs_kty="OKP";cs_kenc="COSE_Key",
   </join/ech0ech00000>;ct=41;rt="core.osc.j";oscore-gid="ech0ech00000";
                        app-gp="group2";cs_alg="EdDSA";cs_crv="Ed25519";
                        cs_kty="OKP";cs_kenc="COSE_Key",
   </join/abcdef120000>;ct=41;rt="core.osc.j";oscore-gid="abcdef120000";
                        app-gp="group3";app-gp="group4";cs_alg="EdDSA";
                        cs_crv="Ed25519";cs_kty="OKP";cs_kenc="COSE_Key"

   Response: RD -> GM

   Res: 2.04 Changed
   Location-Path: /rd/4521

   Alternatively, the GM can perform a PATCH/iPATCH [RFC8132] request to
   the RD, as per Section 5.3.3 of [I-D.ietf-core-resource-directory].
   This requires new media-types to be defined in future standards, to
   apply a link-format document as a patch to an existing stored
   document.

5.  Discovery of OSCORE Groups

   A CoAP endpoint that wants to join an OSCORE group, hereafter called
   the joining node, might not have all the necessary information at
   deployment time.  Also, it might want to know about possible new
   OSCORE groups created afterwards by the respective Group Managers.

   To this end, the joining node can perform a resource lookup at the RD
   as per Section 6.1 of [I-D.ietf-core-resource-directory], to retrieve
   the missing pieces of information needed to join the OSCORE group(s)
   of interest.  The joining node can find the RD as described in
   Section 4 of [I-D.ietf-core-resource-directory].

   The joining node MUST use the following parameter values for the
   lookup filtering.

   o  'rt' = "core.osc.j" (see Section 8.1).

   The joining node MAY additionally consider the following parameters
   for the lookup filtering, depending on the information it has already
   available.




Tiloca, et al.           Expires January 6, 2020                [Page 9]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   o  'oscore-gid', specifying the zeroed-epoch Group ID of the OSCORE
      group of interest.  This parameter MUST specify a single value.

   o  'ep', specifying the registered endpoint of the GM.

   o  'app-gp', specifying the name(s) of the application group(s)
      associated with the OSCORE group of interest.  This parameter MAY
      be included multiple times, and each occurrence MUST specify the
      name of one application group.  An application group MUST be
      specified only once.

5.1.  Discovery Example #1

   Consistently with the examples in Section 3 and Section 4, the
   example below considers a joining node that wants to join the OSCORE
   group associated with the application group "group1", but that does
   not know the zeroed-epoch Group ID of the OSCORE group, the
   responsible GM and the join resource to access.

   Request: Joining node -> RD

   Req: GET coap://rd.example.com/rd-lookup/res
     ?rt=core.osc.j&app-gp=group1

   Response: RD -> Joining node

   Res: 2.05 Content
   Payload:
   <coap://[2001:db8::ab]/join/feedca570000>;rt="core.osc.j";
       oscore-gid="feedca570000";app-gp="group1";
       cs_alg="EdDSA";cs_crv="Ed25519";cs_kty="OKP";
       cs_kenc="COSE_Key";anchor="coap://[2001:db8::ab]"

   To retrieve the multicast IP address used in "group1", the joining
   node performs an endpoint lookup as shown below.  The following
   assumes that the application group "group1" had been previously
   registered as per Appendix A of [I-D.ietf-core-resource-directory],
   with ff35:30:2001:db8::23 as associated multicast IP address.

   Request: Joining node -> RD

   Req: GET coap://rd.example.com/rd-lookup/ep
     ?et=core.rd-group&ep=group1

   Response: RD -> Joining node






Tiloca, et al.           Expires January 6, 2020               [Page 10]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Res: 2.05 Content
   Payload:
   </rd/501>;ep="group1";et="core.rd-group";
             base="coap://[ff35:30:2001:db8::23]"

5.2.  Discovery Example #2

   Consistently with the examples in Section 3 and Section 4, the
   example below considers a joining node that wants to join the OSCORE
   group with zeroed-epoch Group ID "feedca570000", but that does not
   know the responsible GM, the join resource to access, and the
   associated application groups.

   The example also shows how the joining node uses CoAP observation
   [RFC7641], in order to be notified of possible changes in the join
   resource's target attributes.  This is also useful to handle the case
   where the OSCORE group of interest has not been created yet, so that
   the joining node can receive the requested information when it
   becomes available.

   Request: Joining node -> RD

   Req: GET coap://rd.example.com/rd-lookup/res
     ?rt=osc.j&oscore-gid=feedca570000
   Observe: 0

   Response: RD -> Joining node

   Res: 2.05 Content
   Observe: 24
   Payload:
   <coap://[2001:db8::ab]/join/feedca570000>;rt="osc.j";
       oscore-gid="feedca570000";app-gp="group1";
       cs_alg="EdDSA";cs_crv="Ed25519";cs_kty="OKP";
       cs_kenc="COSE_Key";anchor="coap://[2001:db8::ab]"

   Depending on the search criteria, the joining node performing the
   resource lookup can get large responses.  This can happen, for
   instance, when the lookup request targets all the join resources at a
   specified GM, or all the join resources of all the registered GMs, as
   in the example below.

   Request: Joining node -> RD

   Req: GET coap://rd.example.com/rd-lookup/res?rt=osc.j

   Response: RD -> Joining node




Tiloca, et al.           Expires January 6, 2020               [Page 11]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Res: 2.05 Content
   Payload:
   <coap://[2001:db8::ab]/join/feedca570000>;rt="osc.j";
       oscore-gid="feedca570000";app-gp="group1";
       cs_alg="EdDSA";cs_crv="Ed25519";cs_kty="OKP";
       cs_kenc="COSE_Key";anchor="coap://[2001:db8::ab]",
   <coap://[2001:db8::ab]/join/ech0ech00000>;rt="osc.j";
       oscore-gid="ech0ech00000";app-gp="group2";
       cs_alg="EdDSA";cs_crv="Ed25519";cs_kty="OKP";
       cs_kenc="COSE_Key";anchor="coap://[2001:db8::ab]",
   <coap://[2001:db8::ab]/join/abcdef120000>;rt="osc.j";
       oscore-gid="abcdef120000";app-gp="group3";
       app-gp="group4";cs_alg="EdDSA";cs_crv="Ed25519";
       cs_kty="OKP";cs_kenc="COSE_Key";anchor="coap://[2001:db8::ab]"

   Therefore, it is RECOMMENDED that a joining node which performs a
   resource lookup with the CoAP Observe option specifies the value of
   the parameter 'oscore-gid' in its GET request sent to the RD.

6.  Use Case Example With Full Discovery

   In this section, the discovery of security groups is described to
   support the installation process of a lighting installation in an
   office building.  The described process is a simplified version of
   one of many processes.

   Assume the existence of four luminaires that are members of two
   application groups.  In the first application group, the four
   luminaires receive presence messages and light intensity messages
   from sensors or their proxy.  In the second application group, the
   four luminaires and several other pieces of equipment receive
   building state schedules.

   Each of the two application groups is associated to a different
   security group and uses its own dedicated multicast IP address.

   The Fairhair Alliance describes how a new device is accepted and
   commissioned in the network [Fairhair], by means of its certificate
   stored during the manufacturing process.  When commissioning the new
   device in the installation network, the new device gets a new
   identity defined by a newly allocated certificate, following the
   BRSKI specification.

   Section 7.3 of [I-D.ietf-core-resource-directory] describes how the
   Commissioning Tool (CT) assigns an endpoint name based on the CN
   field, (CN=ACME) and the serial number of the certificate (serial
   number = 123x, with 3 < x < 8).  Corresponding ep-names ACME-1234,
   ACME-1235, ACME-1236 and ACME-1237 are also assumed.



Tiloca, et al.           Expires January 6, 2020               [Page 12]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   It is common practice that locations in the building are specified
   according to a coordinate system.  After the acceptance of the
   luminaires into the installation network, the coordinate of each
   device is communicated to the CT.  This can be done manually or
   automatically.

   The mapping between location and ep-name is calculated by the CT.
   For instance, on the basis of grouping criteria, the CT assigns: i)
   group "grp_R2-4-015" to the four luminaires; and ii) group
   "grp_schedule" to all schedule requiring devices.  Also, the device
   with ep name ACME-123x has been assigned IP address: [2001:db8:4::x].
   The RD is assigned IP address: [2001:db8:4:ff].  The used multicast
   addresses are: [ff05::5:1] and [ff05::5:2].

   *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

   The CT defines the application group "grp_R2-4-015", with resource
   /light and base address [ff05::5:1], as follows.

   Request: CT -> RD

   Req: POST coap://[2001:db8:4::ff]/rd
     ?ep=grp_R2-4-015&et=core.rd-group&base=coap://[ff05::5:1]
   Payload:
   </light>;rt="oic.d.light"

   Response: RD -> CT

   Res: 2.01 Created
   Location-Path: /rd/501

   Also, the CT defines a second application group "grp_schedule", with
   resource /schedule and base address [ff05::5:2], as follows.

   Request: CT -> RD

   Req: POST coap://[2001:db8:4::ff]/rd
     ?ep=grp_schedule&et=core.rd-group&base=coap://[ff05::5:2]
   Payload:
   </schedule>;rt="oic.r.time.period"

   Response: RD -> CT

   Res: 2.01 Created
   Location-Path: /rd/502

   *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***




Tiloca, et al.           Expires January 6, 2020               [Page 13]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Consecutively, the CT registers the four devices in the RD (IP
   address: 2001:db8:4::ff), with their endpoint names and application
   groups.

   For group "grp_R2-4-015", four endpoints are specified as follows,
   with x = 4, 5, 6, 7.

   Request: CT -> RD

   Req: POST coap://[2001:db8:4::ff]/rd
     ?ep=ACME-123x&base=coap://[2001:db8:4::x]&app-gp=grp_R2-4-015
   Payload:
   </light>;rt="oic.d.light"

   Response: RD -> CT

   Res: 2.01 Created
   Location-Path: /rd/452x

   For group "grp_schedule", four other endpoints are specified as
   follows, with x = 4, 5, 6, 7.

   Request: CT -> RD

   Req: POST coap://[2001:db8:4::ff]/rd
     ?ep=ACME-123x&base=coap://[2001:db8:4::x]&app-gp=grp_schedule
   Payload:
   </schedule>;rt="oic.r.time.period"

   Response: RD -> CT

   Res: 2.01 Created
   Location-Path: /rd/456x

   *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

   Finally, the CT defines the corresponding security groups.  In
   particular, assuming a Group Manager responsible for both security
   groups and with address [2001:db8::ab], the CT specifies:

   Request: CT -> RD

  Req: POST coap://[2001:db8:4::ff]/rd?ep=gm1&base=coap://[2001:db8::ab]
  Payload:
  </join/feedca570000>;ct=41;rt="core.osc.j";
                       oscore-gid="feedca570000";app-gp="grp_R2-4-015",
  </join/feedsc590000>;ct=41;rt="core.osc.j";
                       oscore-gid="feedsc590000";app-gp="grp_schedule"



Tiloca, et al.           Expires January 6, 2020               [Page 14]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Response: RD -> CT

   Res: 2.01 Created
   Location-Path: /rd/4521

   *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

   The device with IP address [2001:db8:4::x] can consequently learn the
   groups to which it belongs.  In particular, it first does an ep
   lookup to the RD to learn the application groups to which it belongs.

   Request: Joining node -> RD

   Req: GET coap://[2001:db8:4::ff]/rd-lookup/ep
     ?base=coap://[2001:db8:4::x]

   Response: RD -> Joining node

   Res: 2.05 Content
   Payload:
   <rd/452x>;base=coap://[2001:db8:4::x]&ep=ACME-123x&\
             app-gp=grp_R2-4-015,
   <rd/456x>;base=coap://[2001:db8:4::x]&ep=ACME-123x&\
             app-gp=grp_schedule

   To retrieve the multicast IP address used in "grp_R2-4-015", the
   device performs an endpoint lookup as shown below.

   Request: Joining node -> RD

   Req: GET coap://[2001:db8:4::ff]/rd-lookup/ep
     ?et=core.rd-group&ep=grp_R2-4-015

   Response: RD -> Joining node

   Res: 2.05 Content
   Payload:
   </rd/501>;ep="grp_R2-4-015";et="core.rd-group";
             base="coap://[ff05::5:1]"

   Similarly, to retrieve the multicast IP address used in
   "grp_schedule", the device performs an endpoint lookup as shown
   below.

   Request: Joining node -> RD

   Req: GET coap://[2001:db8:4::ff]/rd-lookup/ep
     ?et=core.rd-group&ep=grp_schedule



Tiloca, et al.           Expires January 6, 2020               [Page 15]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Response: RD -> Joining node

   Res: 2.05 Content
   Payload:
   </rd/502>;ep="grp_schedule";et="core.rd-group";
             base="coap://[ff05::5:2]"

   *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

   Having learnt the application groups to which the device belongs, the
   device learns the security groups to which it belongs.  In
   particular, it does the following for app-gp="grp_R2-4-015".

   Request: Joining node -> RD

   Req: GET coap://[2001:db8:4::ff]/rd-lookup/res
     ?rt=core.osc.j&app-gp=grp_R2-4-015

   Response: RD -> Joining Node

   Res: 2.05 Content
   Payload:
   <coap://[2001:db8::ab]/join/feedca570000>;
       rt="core.osc.j";oscore-gid="feedca570000";
       app-gp="grp_R2-4-015";anchor="coap://[2001:db8::ab]"

   Similarly, the device does the following for app-gp="grp_schedule".

   Req: GET coap://[2001:db8:4::ff]/rd-lookup/res
     ?rt=core.osc.j&app-gp=grp_schedule

   Response: RD -> Joining Node

   Res: 2.05 Content
   Payload:
   <coap://[2001:db8::ab]/join/feedsc590000>;
       rt="core.osc.j";oscore-gid="feedsc590000";
       app-gp="grp_schedule";anchor="coap://[2001:db8::ab]"

   *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

   After this last discovery step, the device can ask permission to join
   the security groups, and effectively join them through the Group
   Manager, e.g. according to [I-D.ietf-ace-key-groupcomm-oscore].







Tiloca, et al.           Expires January 6, 2020               [Page 16]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


7.  Security Considerations

   The security considerations as described in Section 8 of
   [I-D.ietf-core-resource-directory] apply here as well.

8.  IANA Considerations

   This document has the following actions for IANA.

8.1.  Resource Types

   IANA is asked to enter the following value into the Resource Type
   (rt=) Link Target Attribute Values subregistry within the Constrained
   Restful Environments (CoRE) Parameters registry defined in [RFC6690].

         +------------+----------------------+-------------------+
         | Value      | Description          | Reference         |
         +------------+----------------------+-------------------+
         |            |                      |                   |
         | core.osc.j | Join resource of an  | [[this document]] |
         |            | OSCORE Group Manager |                   |
         |            |                      |                   |
         +------------+----------------------+-------------------|

9.  References

9.1.  Normative References

   [I-D.ietf-ace-key-groupcomm]
              Palombini, F. and M. Tiloca, "Key Provisioning for Group
              Communication using ACE", draft-ietf-ace-key-groupcomm-02
              (work in progress), July 2019.

   [I-D.ietf-ace-key-groupcomm-oscore]
              Tiloca, M., Park, J., and F. Palombini, "Key Management
              for OSCORE Groups in ACE", draft-ietf-ace-key-groupcomm-
              oscore-02 (work in progress), July 2019.

   [I-D.ietf-core-oscore-groupcomm]
              Tiloca, M., Selander, G., Palombini, F., and J. Park,
              "Group OSCORE - Secure Group Communication for CoAP",
              draft-ietf-core-oscore-groupcomm-05 (work in progress),
              July 2019.

   [I-D.ietf-core-resource-directory]
              Shelby, Z., Koster, M., Bormann, C., Stok, P., and C.
              Amsuess, "CoRE Resource Directory", draft-ietf-core-
              resource-directory-22 (work in progress), July 2019.



Tiloca, et al.           Expires January 6, 2020               [Page 17]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 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>.

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

   [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>.

   [RFC8152]  Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,
              <https://www.rfc-editor.org/info/rfc8152>.

   [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>.

9.2.  Informative References

   [Fairhair]
              FairHair Alliance, "Security Architecture for the Internet
              of Things (IoT) in Commercial Buildings", White Paper, ed.
              Piotr Polak , March 2018, <https://www.fairhair-
              alliance.org/data/downloadables/1/9/
              fairhair_security_wp_march-2018.pdf>.

   [I-D.dijk-core-groupcomm-bis]
              Dijk, E., Wang, C., and M. Tiloca, "Group Communication
              for the Constrained Application Protocol (CoAP)", draft-
              dijk-core-groupcomm-bis-00 (work in progress), March 2019.

   [I-D.ietf-ace-oauth-authz]
              Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
              H. Tschofenig, "Authentication and Authorization for
              Constrained Environments (ACE) using the OAuth 2.0
              Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-24
              (work in progress), March 2019.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", draft-ietf-core-object-security-16 (work in
              progress), March 2019.



Tiloca, et al.           Expires January 6, 2020               [Page 18]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   [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>.

   [RFC7390]  Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
              the Constrained Application Protocol (CoAP)", RFC 7390,
              DOI 10.17487/RFC7390, October 2014,
              <https://www.rfc-editor.org/info/rfc7390>.

   [RFC7641]  Hartke, K., "Observing Resources in the Constrained
              Application Protocol (CoAP)", RFC 7641,
              DOI 10.17487/RFC7641, September 2015,
              <https://www.rfc-editor.org/info/rfc7641>.

   [RFC8132]  van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
              FETCH Methods for the Constrained Application Protocol
              (CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
              <https://www.rfc-editor.org/info/rfc8132>.

Acknowledgments

   The authors sincerely thank Carsten Bormann, Francesca Palombini,
   Dave Robin and Jim Schaad for their comments and feedback.

   The work on this document has been partly supported by VINNOVA and
   the Celtic-Next project CRITISEC, and by the EIT-Digital High Impact
   Initiative ACTIVE.

Authors' Addresses

   Marco Tiloca
   RISE AB
   Isafjordsgatan 22
   Kista  SE-16440 Stockholm
   Sweden

   Email: marco.tiloca@ri.se


   Christian Amsuess
   Hollandstr. 12/4
   Vienna  1020
   Austria

   Email: christian@amsuess.com





Tiloca, et al.           Expires January 6, 2020               [Page 19]


Internet-Draft   OSCORE group discovery with the CoRE RD       July 2019


   Peter van der Stok
   Consultant

   Phone: +31-492474673 (Netherlands), +33-966015248 (France)
   Email: consultancy@vanderstok.org
   URI:   www.vanderstok.org













































Tiloca, et al.           Expires January 6, 2020               [Page 20]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/