anima Working Group M. Richardson
Internet-Draft Sandelman Software Works
Intended status: Standards Track P. van der Stok
Expires: March 15, 2019 vanderstok consultancy
P. Kampanakis
Cisco Systems
September 11, 2018

Constrained Voucher Artifacts for Bootstrapping Protocols
draft-ietf-anima-constrained-voucher-02

Abstract

This document defines a strategy to securely assign a pledge to an owner, using an artifact signed, directly or indirectly, by the pledge's manufacturer. This artifact is known as a "voucher".

This document builds upon the work in [RFC8366], encoding the resulting artifact in CBOR. Use with two signature technologies are described.

Additionally, this document explains how constrained vouchers may be transported in the [I-D.ietf-ace-coap-est] protocol.

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 March 15, 2019.

Copyright Notice

Copyright (c) 2018 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

Enrollment of new nodes into constrained networks with constrained nodes present unique challenges.

There are bandwidth and code space issues to contend. A solution such as [I-D.ietf-anima-bootstrapping-keyinfra] may be too large in terms of code space or bandwidth required.

This document defines a constrained version of [RFC8366]. Rather than serializing the YANG definition in JSON, it is serialized into CBOR ([RFC7049]).

This document follows a similar, but not identical structure as [RFC8366]. Some sections are left out entirely. Additional sections have been added concerning:

  1. Addition of voucher-request specification as defined in [I-D.ietf-anima-bootstrapping-keyinfra],
  2. Addition to [I-D.ietf-ace-coap-est] of voucher transport requests over coap.

The CBOR definitions for this constrained voucher format are defined using the mechanism describe in [I-D.ietf-core-yang-cbor] using the SID mechanism explained in [I-D.ietf-core-sid]. As the tooling to convert YANG documents into an list of SID keys is still in its infancy, the table of SID values presented here should be considered normative rather than the output of the pyang tool.

Two methods of signing the resulting CBOR object are described in this document:

  1. One is CMS [RFC5652].
  2. The other is COSE [RFC8152] signatures.

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

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

4. Survey of Voucher Types

[RFC8366] provides for vouchers that assert proximity, that authenticate the registrar and that include different amounts of anti-replay protection.

This document does not make any extensions to the types of vouchers.

Time based vouchers are included in this definition, but given that constrained devices are extremely unlikely to know the correct time, their use is very unlikely. Most users of these constrained vouchers will be online and will use live nonces to provide anti-replay protection.

[RFC8366] defined only the voucher artifact, and not the Voucher Request artifact, which was defined in [I-D.ietf-anima-bootstrapping-keyinfra].

This document defines both a constrained voucher and a constrained voucher-request. They are presented in the order voucher-request, followed by voucher response as this is the time order that they occur.

This document defines both CMS-signed voucher requests and responses, and COSE signed voucher requests and responses. The use of CMS signatures implies the use of PKIX format certificates. The pinned-domain-cert present in such a voucher, is the certificate of the Registrar.

The use of COSE signatures permits the use of both PKIX format certificates, and also raw public keys (RPK). When RPKs are used, the voucher produced by the MASA pins the raw public key of the Registrar: the pinned-domain-subject-public-key-info in such a voucher, is the raw public key of the Registrar. This is described in the YANG definition for the constrained voucher.

5. Discovery and URI

This section describes the BRSKI extensions to EST-coaps [I-D.ietf-ace-coap-est] to transport the voucher between registrar, proxy and pledge over CoAP. The extensions are targeted to low-resource networks with small packets. Saving header space is important and the EST-coaps URI is shorter than the EST URI.

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

  REQ: GET /.well-known/core?rt=ace.est

  RES: 2.05 Content
  </est>; rt="ace.est"

The EST-coaps server URIs differ from the EST URI by replacing the scheme https by coaps and by specifying shorter resource path names:

  coaps://www.example.com/est/short-name

Figure 5 in section 3.2.2 of [RFC7030] enumerates the operations and corresponding paths which are supported by EST. Table 1 provides the mapping from the BRSKI extension URI path to the EST-coaps URI path.

BRSKI path to EST-coaps path
BRSKI EST-coaps
/requestvoucher /rv
/voucher-status /vs
/enrollstatus /es
/requestauditlog /ra

/requestvoucher and /enrollstatus are needed between pledge and Registrar.

When discovering the root path for the EST resources, the server MAY return the full resource paths and the used content types. This is useful when multiple content types are specified for EST-coaps server. For example, the following more complete response is possible.

  REQ: GET /.well-known/core?rt=ace.est*

  RES: 2.05 Content
  </est>; rt="ace.est"
  </est/rv>; rt="ace.est/rv";ct=50 60 TBD2 TBD3 16
  </est/vs>; rt="ace.est/vs";ct=50 60
  </est/es>; rt="ace.est/es";ct=50 60
  </est/ra>; rt="ace.est/ra";ct=TBD2 TBD3 16

The first line MUST be returned in response to the GET, The following four lines MAY be returned to show the supported Content-Formats. The return of the content-types allows the client to choose the most appropriate one from multiple content types.

ct=16 stands for the Content-Format "application/cose", and ct=TBD2 stands for Content-Format "application/voucher-cms+cbor, and ct=TBD3 stands for Content-Format "application/voucher-cose+cbor".

Content-Formats TBD2 and TBD3 are defined in this document. The return of the content-formats allows the client to choose the most appropriate one from multiple content formats.

The Content-Format ("application/json") 50 MAY be supported. Content-Formats ("application/cbor") 60, TBD2, TBD3, and 16 MUST be supported.

6. Artifacts

This section describes the abstract (tree) definition as explained in [I-D.ietf-netmod-yang-tree-diagrams] first. This provides a high-level view of the contents of each artifact.

Then the assigned SID values are presented. These have been assigned using the rules in [I-D.ietf-core-yang-cbor], with an allocation that was made via the http://comi.space service.

6.1. Voucher Request artifact

6.1.1. Tree Diagram

The following diagram is largely a duplicate of the contents of [RFC8366], with the addition of proximity-registrar-subject-public-key-info, proximity-registrar-cert, and prior-signed-voucher-request.

prior-signed-voucher-request is only used between the Registrar and the MASA. proximity-registrar-subject-public-key-info replaces proximity-registrar-cert for the extremely constrained cases.

module: ietf-constrained-voucher-request

  grouping voucher-request-constrained-grouping
    +-- voucher
       +-- created-on?
       |       yang:date-and-time
       +-- expires-on?
       |       yang:date-and-time
       +-- assertion                                      enumeration
       +-- serial-number                                  string
       +-- idevid-issuer?                                 binary
       +-- pinned-domain-cert?                            binary
       +-- domain-cert-revocation-checks?                 boolean
       +-- nonce?                                         binary
       +-- last-renewal-date?
       |       yang:date-and-time
       +-- proximity-registrar-subject-public-key-info?   binary
       +-- proximity-registrar-cert?                      binary
       +-- prior-signed-voucher-request?                  binary

6.1.2. SID values

           
      SID Assigned to
--------- -------------------------------------------------- 
  1001154 data /ietf-constrained-voucher-request:voucher
  1001155 data .../assertion
  1001156 data .../created-on
  1001157 data .../domain-cert-revocation-checks
  1001158 data .../expires-on
  1001159 data .../idevid-issuer
  1001160 data .../last-renewal-date
  1001161 data /ietf-constrained-voucher-request:voucher/nonce
  1001162 data .../pinned-domain-cert
  1001163 data .../prior-signed-voucher-request
  1001164 data .../proximity-registrar-cert
  1001165 data .../proximity-registrar-subject-public-key-info
  1001166 data .../serial-number
           

6.1.3. YANG Module

In the constrained-voucher-request YANG module, the voucher is "augmented" within the "used" grouping statement such that one continuous set of SID values is generated for the constrained-voucher-request module name, all voucher attributes, and the constrained-voucher-request attribute. Two attributes of the voucher are "refined" to be optional.

<CODE BEGINS> file "ietf-constrained-voucher-request@2018-09-01.yang"
module ietf-constrained-voucher-request {
  yang-version 1.1;

  namespace
    "urn:ietf:params:xml:ns:yang:ietf-constrained-voucher-request";
  prefix "constrained";

  import ietf-restconf {
    prefix rc;
    description
      "This import statement is only present to access
       the yang-data extension defined in RFC 8040.";
    reference "RFC 8040: RESTCONF Protocol";
  }

  import ietf-voucher {
    prefix "v";
  }

  organization
   "IETF ANIMA Working Group";

  contact
   "WG Web:   <http://tools.ietf.org/wg/anima/>
    WG List:  <mailto:anima@ietf.org>
    Author:   Michael Richardson
              <mailto:mcr+ietf@sandelman.ca>
    Author:   Peter van der Stok
              <mailto: consultancy@vanderstok.org>
    Author:   Panos Kampanakis
              <mailto: pkampana@cisco.com>";
  description
   "This module defines the format for a voucher request,
    which is produced by a pledge to request a voucher.
    The voucher-request is sent to the potential owner's
    Registrar, which in turn sends the voucher request to
    the manufacturer or delegate (MASA).

    A voucher is then returned to the pledge, binding the
    pledge to the owner.  This is a constrained version of the
    voucher-request present in
    draft-ietf-anima-bootstrap-keyinfra.txt.

    This version provides a very restricted subset appropriate
    for very constrained devices.
    In particular, it assumes that nonce-ful operation is
    always required, that expiration dates are rather weak, as no
    clocks can be assumed, and that the Registrar is identified
    by a pinned Raw Public Key.

    The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
    'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
    and 'OPTIONAL' in the module text are to be interpreted as
    described in RFC 2119.";

  revision "2018-09-01" {
    description
     "Initial version";
    reference
     "RFC XXXX: Voucher Profile for Constrained Devices";
  }

  rc:yang-data voucher-request-constrained-artifact {
    // YANG data template for a voucher.
    uses voucher-request-constrained-grouping;
  }

  // Grouping defined for future usage
  grouping voucher-request-constrained-grouping {
    description
      "Grouping to allow reuse/extensions in future work.";

    uses v:voucher-artifact-grouping {

      refine voucher/created-on {
          mandatory  false;
      }

      refine voucher/pinned-domain-cert {
          mandatory  false;
      }


      augment "voucher" {
        description "Base the constrained voucher-request upon the
          regular one";

        leaf proximity-registrar-subject-public-key-info {
          type binary;
          description
            "The proximity-registrar-subject-public-key-info replaces
 	     the proximit-registrar-cert in constrained uses of
             the voucher-request.
             The proximity-registrar-subject-public-key-info is the
             Raw Public Key of the Registrar. This field is encoded
             as specified in RFC7250, section 3.
             The ECDSA algorithm MUST be supported.
             The EdDSA algorithm as specified in
             draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
             Support for the DSA algorithm is not recommended.
             Support for the RSA algorithm is a MAY.";
        }

        leaf proximity-registrar-cert {
          type binary;
          description
            "An X.509 v3 certificate structure as specified by
             RFC 5280,
             Section 4 encoded using the ASN.1 distinguished encoding
             rules (DER), as specified in ITU-T X.690.

             The first certificate in the Registrar TLS server
             certificate_list sequence  (see [RFC5246]) presented by
             the Registrar to the Pledge. This MUST be populated in a
             Pledge's voucher request if the proximity assertion is
             populated.";
        }

        leaf prior-signed-voucher-request {
          type binary;
          description
            "If it is necessary to change a voucher, or re-sign and
             forward a voucher that was previously provided along a
             protocol path, then the previously signed voucher
             SHOULD be included in this field.

             For example, a pledge might sign a proximity voucher,
             which an intermediate registrar then re-signs to
             make its own proximity assertion.  This is a simple
             mechanism for a chain of trusted parties to change a
             voucher, while maintaining the prior signature
             information.

             The pledge MUST ignore all prior voucher information
             when accepting a voucher for imprinting. Other
             parties MAY examine the prior signed voucher
             information for the purposes of policy decisions.
             For example this information could be useful to a
             MASA to determine that both pledge and registrar
             agree on proximity assertions. The MASA SHOULD
             remove all prior-signed-voucher-request information when
             signing a voucher for imprinting so as to minimize the
             final voucher size.";
        }
      }
    }
  }
}
<CODE ENDS>

6.1.4. Example voucher request artifact

Below a CBOR serialization of the constrained-voucher-request is shown in diagnostic CBOR notation. The enum value of the assertion field is calculated to be zero by following the algorithm described in section 9.6.4.2 of [RFC7950].

{
  1001101: {
    +2 : "2016-10-07T19:31:42Z", / SID = 1001103, created-on /
    +4 : "2016-10-21T19:31:42Z", / SID = 1001105, expires-on /
    +1 : 0,                      / SID = 1001102, assertion /
                                 /                "verified" /
    +12: "JADA123456789",        / SID = 1001113, serial-number /
    +5 : h'01020D0F',            / SID = 1001106, idevid-issuer /
    +8 : h'01020D0F',            / SID = 1001109, pinned-domain-cert/
    +3 : true,                   / SID = 1001104, domain-cert
                                                 -revocation-checks /
    +6 : "2017-10-07T19:31:42Z", / SID = 1001107, last-renewal-date /
    +11: h'01020D0F'             / SID = 1001112, proximity
                                -registrar-subject-public-key-info /
  }
}

6.2. Voucher artifact

The voucher's primary purpose is to securely assign a pledge to an owner. The voucher informs the pledge which entity it should consider to be its owner.

This document defines a voucher that is a CBOR encoded instance of the YANG module defined in Section 5.3 that has been signed with CMS or with COSE.

6.2.1. Tree Diagram

The following diagram is largely a duplicate of the contents of [RFC8366], with only the addition of pinned-domain-subject-public-key-info.

module: ietf-constrained-voucher

  grouping voucher-constrained-grouping
    +-- voucher
       +-- created-on?                              yang:date-and-time
       +-- expires-on?                              yang:date-and-time
       +-- assertion                                enumeration
       +-- serial-number                            string
       +-- idevid-issuer?                           binary
       +-- pinned-domain-cert?                      binary
       +-- domain-cert-revocation-checks?           boolean
       +-- nonce?                                   binary
       +-- last-renewal-date?                       yang:date-and-time
       +-- pinned-domain-subject-public-key-info?   binary

6.2.2. SID values


      SID Assigned to
--------- --------------------------------------------------
  1001104 data .../voucher
  1001105 data .../assertion
  1001106 data .../created-on
  1001107 data .../domain-cert-revocation-checks
  1001108 data .../expires-on
  1001109 data .../idevid-issuer
  1001110 data .../last-renewal-date
  1001111 data .../nonce
  1001112 data .../pinned-domain-cert
  1001113 data .../pinned-domain-subject-public-key-info
  1001114 data .../serial-number

6.2.3. YANG Module

In the constraine-voucher YANG module, the voucher is "augmented" within the "used" grouping statement such that one continuous set of SID values is generated for the constrained-voucher module name, all voucher attributes, and the constrained-voucher attribute. Two attributes of the voucher are "refined" to be optional.

<CODE BEGINS> file "ietf-constrained-voucher@2018-09-01.yang"
module ietf-constrained-voucher {
  yang-version 1.1;

  namespace
    "urn:ietf:params:xml:ns:yang:ietf-constrained-voucher";
  prefix "constrained";

  import ietf-restconf {
    prefix rc;
    description
      "This import statement is only present to access
       the yang-data extension defined in RFC 8040.";
    reference "RFC 8040: RESTCONF Protocol";
  }

  import ietf-voucher {
    prefix "v";
  }

  organization
   "IETF ANIMA Working Group";

  contact
   "WG Web:   <http://tools.ietf.org/wg/anima/>
    WG List:  <mailto:anima@ietf.org>
    Author:   Michael Richardson
              <mailto:mcr+ietf@sandelman.ca>
    Author:   Peter van der Stok
              <mailto: consultancy@vanderstok.org>
    Author:   Panos Kampanakis
              <mailto: pkampana@cisco.com>";
description
  "This module defines the format for a voucher, which is produced
   by a pledge's manufacturer or delegate (MASA) to securely assign
   one or more pledges to an 'owner', so that the pledges may
   establis a secure connection to the owner's network
   infrastructure.

   This version provides a very restricted subset appropriate
   for very constrained devices.
   In particular, it assumes that nonce-ful operation is
   always required, that expiration dates are rather weak, as no
   clocks can be assumed, and that the Registrar is identified
   by a pinned Raw Public Key.

   The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
   'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
   and 'OPTIONAL' in the module text are to be interpreted as
   described in RFC 2119.";

  revision "2018-09-01" {
    description
     "Initial version";
    reference
     "RFC XXXX: Voucher Profile for Constrained Devices";
  }

  rc:yang-data voucher-constrained-artifact {
    // YANG data template for a voucher.
    uses voucher-constrained-grouping;
  }

  // Grouping defined for future usage
  grouping voucher-constrained-grouping {
    description
      "Grouping to allow reuse/extensions in future work.";

    uses v:voucher-artifact-grouping {

      refine voucher/created-on {
          mandatory  false;
      }

      refine voucher/pinned-domain-cert {
          mandatory  false;
      }

      augment "voucher" {
        description "Base the constrained voucher
                                   upon the regular one";
        leaf pinned-domain-subject-public-key-info {
          type binary;
          description
            "The pinned-domain-subject-public-key-info replaces the
             pinned-domain-cert in constrained uses of
             the voucher. The pinned-domain-subject-public-key-info
             is the Raw Public Key of the Registrar.
             This field is encoded as specified in RFC7250,
             section 3.
             The ECDSA algorithm MUST be supported.
             The EdDSA algorithm as specified in
             draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
             Support for the DSA algorithm is not recommended.
             Support for the RSA algorithm is a MAY.";
        }
      }
    }
  }
}
<CODE ENDS>

6.2.4. Example voucher artifacts

Below a the CBOR serialization of the the constrained-voucher and constrained-voucher-request are shown in diagnostic CBOR notation. The enum value of the assertion field is calculated to be zero by following the algorithm described in section 9.6.4.2 of [RFC7950].

{
  1001051: {
    +2 : "2016-10-07T19:31:42Z", / SID = 1001053, created-on /
    +4 : "2016-10-21T19:31:42Z", / SID = 1001055, expires-on /
    +1 : 0,                      / SID = 1001052, assertion /
                                 /                "verified" /
    +10: "JADA123456789",        / SID = 1001061, serial-number /
    +5 : h'01020D0F',            / SID = 1001056, idevid-issuer /
    +8 : h'01020D0F',            / SID = 1001059, pinned-domain-cert/
    +3 : true,                   / SID = 1001054, domain-cert
                                                  -revocation-checks/
    +6 : "2017-10-07T19:31:42Z", / SID = 1001057, last-renewal-date /
    +9 : h'01020D0F'             / SID = 1001060, pinned-domain
                                          -subject-public-key-info /
  }
}

6.3. CMS format voucher and voucher-request artifacts

The IETF evolution of PKCS#7 is CMS [RFC5652]. The CMS signed voucher is much like the equivalent voucher defined in [RFC8366].

A different eContentType of TBD1 is used to indicate that the contents are in a different format than in [RFC8366].

The ContentInfo structure contains a payload consisting of the CBOR encoded voucher. The [I-D.ietf-core-yang-cbor] use of delta encoding creates a canonical ordering for the keys on the wire. This canonical ordering is not important as there is no expectation that the content will be reproduced during the validation process.

Normally the recipient is the pledge and the signer is the MASA.

[I-D.ietf-anima-bootstrapping-keyinfra] supports both signed and unsigned voucher requests from the pledge to the JRC. In this specification, voucher-request artifact is not signed from the pledge to the registrar. From the JRC to the MASA, the voucher-request artifact MUST be signed by the domain owner key which is requesting ownership.

The considerations of [RFC5652] section 5.1, concerning validating CMS objects which are really PKCS7 objects (cmsVersion=1) applies.

The CMS structure SHOULD also contain all the certificates leading up to and including the signer's trust anchor certificate known to the recipient. The inclusion of the trust anchor is unusual in many applications, but without it third parties can not accurately audit the transaction.

The CMS structure MAY also contain revocation objects for any intermediate certificate authorities (CAs) between the voucher-issuer and the trust anchor known to the recipient. However, the use of CRLs and other validity mechanisms is discouraged, as the pledge is unlikely to be able to perform online checks, and is unlikely to have a trusted clock source. As described below, the use of short-lived vouchers and/or pledge provided nonce provides a freshness guarantee.

6.3.1. COSE signing

The COSE-Sign1 structure discussed in section 4.2 of [RFC8152]. The CBOR object that carries the body, the signature, and the information about the body and signature is called the COSE_Sign1 structure. It is used when only one signature is used on the body. The signature algorithm is ECSDA with three curves P-256, P-384, and P-512.

Support for EdDSA is encouraged.

Unlike with the CMS structure, the COSE-Sign1 structure does not provide a standard way for the signing keys to be included in the structure. This will not, in general, be a problem for the Pledge, as the key needed to verify the signature MUST be included at manufacturing time.

A problem arises for the Registrar: to verify the voucher, the Registrar must have access to the MASA's public key. This document does not specify how to transfer the relevant key.

7. Design Considerations

The design considerations for the CBOR encoding of vouchers is much the same as for [RFC8366].

One key difference is that the names of the leaves in the YANG does not have a material effect on the size of the resulting CBOR, as the SID translation process assigns integers to the names.

8. Security Considerations

8.1. Clock Sensitivity

TBD.

8.2. Protect Voucher PKI in HSM

TBD.

8.3. Test Domain Certificate Validity when Signing

TBD.

9. IANA Considerations

9.1. Resource Type Registry

Additions to the sub-registry "CoAP Resource Type", within the "CoRE parameters" registry are specified below. These can be registered either in the Expert Review range (0-255) or IETF Review range (256-9999).

 ace.rt.rv needs registration with IANA
 ace.rt.vs needs registration with IANA
 ace.rt.es needs registration with IANA
 ace.rt.ra needs registration with IANA

9.2. The IETF XML Registry

This document registers two URIs in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registration is requested:

  URI: urn:ietf:params:xml:ns:yang:ietf-constrained-voucher
  Registrant Contact: The ANIMA WG of the IETF.
  XML: N/A, the requested URI is an XML namespace.

  URI: urn:ietf:params:xml:ns:yang:ietf-constrained-voucher-request
  Registrant Contact: The ANIMA WG of the IETF.
  XML: N/A, the requested URI is an XML namespace.

9.3. The YANG Module Names Registry

This document registers two YANG modules in the YANG Module Names registry [RFC6020]. Following the format defined in [RFC6020], the the following registration is requested:

  name:         ietf-constrained-voucher
  namespace:    urn:ietf:params:xml:ns:yang:ietf-constrained-voucher
  prefix:       vch
  reference:    RFC XXXX

  name:         ietf-constrained-voucher-request
  namespace:    urn:ietf:params:xml:ns:yang:ietf-constrained
                                           -voucher-request
  prefix:       vch
  reference:    RFC XXXX

9.4. The SMI Security for S/MIME CMS Content Type Registry

This document registers an OID in the "SMI Security for S​/​MIME CMS Content Type" registry (1.2.840.113549.1.9.16.1), with the value:

  Decimal  Description                             References
  -------  --------------------------------------  ----------
  TBD1      id-ct-animaCBORVoucher                 [ThisRFC]

EDNOTE: should a separate value be used for Voucher Requests?

9.5. The SID registry

The SID range 1001100 was allocated by comi.space to the IETF-CONSTRAINED-VOUCHER yang module.

The SID range 1001150 was allocated by comi.space to the IETF-CONSTRAINED-VOUCHER-REQUEST yang module.

EDNOTE: it is unclear if there is further IANA work required.

9.6. Media-Type Registry

This section registers the 'application/voucher-cms+cbor' media type and the 'application/voucher-cose+cbor'in the "Media Types" registry. These media types are used to indicate that the content is a CBOR voucher either signed with a cms structure or a COSE_Sign1 structure [RFC8152].

9.6.1. application/voucher-cms+cbor

Type name:  application
Subtype name:  voucher-cms+cbor
Required parameters:  none
Optional parameters:  none
Encoding considerations:  CMS-signed CBOR vouchers are CBOR
  encoded.
Security considerations:  See Security Considerations, Section
Interoperability considerations:  The format is designed to be
  broadly interoperable.
Published specification:  THIS RFC.
Applications that use this media type:  ANIMA, 6tisch, and other
  zero-touch imprinting systems
Additional information:
  Magic number(s):  None
  File extension(s):  .vch
  Macintosh file type code(s):  none
Person & email address to contact for further information:  IETF
  ANIMA WG
Intended usage:  LIMITED
Restrictions on usage:  NONE
Author:  ANIMA WG
Change controller:  IETF
Provisional registration? (standards tree only):  NO

9.6.2. application/voucher-cose+cbor

Type name:  application
Subtype name:  voucher-cose+cbor
Required parameters:  none
Optional parameters:  cose-type
Encoding considerations:  COSE_Sign1 CBOR vouchers are COSE objects
                          signed with one signer.
Security considerations:  See Security Considerations, Section
Interoperability considerations:  The format is designed to be
  broadly interoperable.
Published specification:  THIS RFC.
Applications that use this media type:  ANIMA, 6tisch, and other
  zero-touch imprinting systems
Additional information:
  Magic number(s):  None
  File extension(s):  .vch
  Macintosh file type code(s):  none
Person & email address to contact for further information:  IETF
  ANIMA WG
Intended usage:  LIMITED
Restrictions on usage:  NONE
Author:  ANIMA WG
Change controller:  IETF
Provisional registration? (standards tree only):  NO

9.7. CoAP Content-Format Registry

Additions to the sub-registry "CoAP Content-Formats", within the "CoRE Parameters" registry are needed for two media types. These can be registered either in the Expert Review range (0-255) or IETF Review range (256-9999).

Media type                    mime type    Encoding   ID  References
----------------------------  -----------  --------- ---- ----------
application/voucher-cms+cbor      - -        CBOR    TBD2  [This RFC]
application/voucher-cose+cbor "COSE-Sign1"   CBOR    TBD3  [This RFC]

10. Acknowledgements

We are very grateful to Jim Schaad for explaining COSE and CMS choices.

Michel Veillette did extensive work on pyang to extend it to support the SID allocation process, and this document was among the first users.

We are grateful for the suggestions done by Esko Dijk.

11. Changelog

-02

Example of requestvoucher with unsigned appllication/cbor is added
attributes of voucher "refined" to optional
CBOR serialization of vouchers improved

-01

application/json is optional, application/cbor is compulsory
Cms and cose mediatypes are introduced

12. References

12.1. Normative References

[I-D.ietf-ace-cbor-web-token] Jones, M., Wahlstroem, E., Erdtman, S. and H. Tschofenig, "CBOR Web Token (CWT)", Internet-Draft draft-ietf-ace-cbor-web-token-15, March 2018.
[I-D.ietf-ace-coap-est] Stok, P., Kampanakis, P., Kumar, S., Richardson, M., Furuhed, M. and S. Raza, "EST over secure CoAP (EST-coaps)", Internet-Draft draft-ietf-ace-coap-est-05, July 2018.
[I-D.ietf-anima-bootstrapping-keyinfra] Pritikin, M., Richardson, M., Behringer, M., Bjarnason, S. and K. Watsen, "Bootstrapping Remote Secure Key Infrastructures (BRSKI)", Internet-Draft draft-ietf-anima-bootstrapping-keyinfra-16, June 2018.
[I-D.ietf-core-object-security] Selander, G., Mattsson, J., Palombini, F. and L. Seitz, "Object Security for Constrained RESTful Environments (OSCORE)", Internet-Draft draft-ietf-core-object-security-14, July 2018.
[I-D.ietf-core-sid] Veillette, M. and A. Pelov, "YANG Schema Item iDentifier (SID)", Internet-Draft draft-ietf-core-sid-04, June 2018.
[I-D.ietf-core-yang-cbor] Veillette, M., Pelov, A., Somaraju, A., Turner, R. and A. Minaburo, "CBOR Encoding of Data Modeled with YANG", Internet-Draft draft-ietf-core-yang-cbor-06, February 2018.
[ieee802-1AR] IEEE Standard, ., "IEEE 802.1AR Secure Device Identifier", 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013.
[RFC7250] Wouters, P., Tschofenig, H., Gilmore, J., Weiler, S. and T. Kivinen, "Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, June 2014.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, July 2017.
[RFC8366] Watsen, K., Richardson, M., Pritikin, M. and T. Eckert, "A Voucher Artifact for Bootstrapping Protocols", RFC 8366, DOI 10.17487/RFC8366, May 2018.

12.2. Informative References

[duckling] Stajano, F. and R. Anderson, "The resurrecting duckling: security issues for ad-hoc wireless networks", 1999.
[I-D.ietf-netmod-yang-tree-diagrams] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", Internet-Draft draft-ietf-netmod-yang-tree-diagrams-06, February 2018.
[pledge] Dictionary.com, ., "Dictionary.com Unabridged", 2015.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, DOI 10.17487/RFC6690, August 2012.
[RFC7030] Pritikin, M., Yee, P. and D. Harkins, "Enrollment over Secure Transport", RFC 7030, DOI 10.17487/RFC7030, October 2013.

Appendix A. EST messages to EST-coaps

This section extends the examples from Appendix A of [I-D.ietf-ace-coap-est]. The CoAP headers are only worked out for the enrollstatus example.

A.1. enrollstatus

A coaps enrollstatus message can be :

    GET coaps://[192.0.2.1:8085]/est/es

The corresponding coap header fields are shown below.

  Ver = 1
  T = 0 (CON)
  Code = 0x01 (0.01 is GET)
  Options
   Option1 (Uri-Host)
     Option Delta = 0x3  (option nr = 3)
     Option Length = 0x9
     Option Value = 192.0.2.1
   Option2 (Uri-Port)
     Option Delta = 0x4  (option nr = 4+3=7)
     Option Length = 0x4
     Option Value = 8085
   Option3 (Uri-Path)
     Option Delta = 0x4   (option nr = 7+4= 11)
     Option Length = 0x7
     Option Value = /est/es
  Payload = [Empty]

A 2.05 Content response with an unsigned JSON voucher (ct=50) will then be:

   2.05 Content (Content-Format: application/json)
     {payload}

With CoAP fields and payload:

   Ver=1
   T=2 (ACK)
   Code = 0x45 (2.05 Content)
   Options
     Option1 (Content-Format)
     Option Delta = 0xC  (option nr 12)
     Option Length = 0x2
     Option Value = 0x32 (application/json)

     Payload =
    [EDNOTE: put here voucher payload ]

A.2. voucher_status

A coaps voucher_status message can be :

   GET coaps://[2001:db8::2:1]:61616]/est/vs

A 2.05 Content response with a non signed CBOR voucher (ct=60) will then be:

    2.05 Content (Content-Format: application/cbor)
    Payload =
    [EDNOTE: put here voucher payload ]

A.3. requestvoucher

Two request-voucher request payloads are possible from pledge to Registrar, a signed one and an unsigned one, as explained in Section 5.2 of [I-D.ietf-anima-bootstrapping-keyinfra].

A.3.1. signed requestvoucher

A coaps signed requestvoucher message from RA to MASA can be :

    POST coaps://[2001:db8::2:1]:61616]/est/rv

A 2.04 Changed response returning CBOR voucher signed with a cms structure(ct=TBD2) will then be:

    2.04 Changed (Content-Format: application/voucher-cms+cbor)
    Payload =
    [EDNOTE: put here encrypted voucher payload ]

A.3.2. unsigned requestvoucher

A coaps unsigned requestvoucher message from pledge to Registrar can be :

    POST coaps://[2001:db8::2:1]:61616]/est/rv

A 2.04 Changed response returning CBOR voucher (ct=60) will then be:

    2.04 Changed (Content-Format: application/cbor)
    Payload =
    [EDNOTE: put here encrypted voucher payload ]

A.4. requestauditing

A coaps requestauditing message can be :

    GET coaps://[2001:db8::2:1]:61616]/est/ra

A 2.05 Content response returning a COSE_Sign1 object (ct=TBD3) will then be:

    2.05 Content (Content-Format: application/voucher-cose+cbor)
    Payload =
    [EDNOTE: put here COSE_Sign1 voucher 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