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A Voucher Artifact for Bootstrapping Protocols
draft-ietf-anima-rfc8366bis-05

Document Type Active Internet-Draft (anima WG)
Authors Kent Watsen , Michael Richardson , Max Pritikin , Toerless Eckert , Qiufang Ma
Last updated 2023-01-25
Replaces draft-richardson-anima-rfc8366bis
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
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draft-ietf-anima-rfc8366bis-05
ANIMA Working Group                                            K. Watsen
Internet-Draft                                           Watsen Networks
Intended status: Standards Track                           M. Richardson
Expires: 29 July 2023                                 Sandelman Software
                                                             M. Pritikin
                                                           Cisco Systems
                                                               T. Eckert
                                                                   Q. Ma
                                                                  Huawei
                                                         25 January 2023

             A Voucher Artifact for Bootstrapping Protocols
                     draft-ietf-anima-rfc8366bis-05

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 defines an artifact format as a YANG-defined JSON or
   CBOR document that has been signed using a variety of cryptographic
   systems.

   The voucher artifact is normally generated by the pledge's
   manufacturer (i.e., the Manufacturer Authorized Signing Authority
   (MASA)).

   This document updates RFC8366, merging a number of extensions into
   the YANG.  The RFC8995 voucher request is also merged into this
   document.

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-anima-rfc8366bis/.

   Discussion of this document takes place on the anima Working Group
   mailing list (mailto:anima@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/anima/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/anima/.

   Source for this draft and an issue tracker can be found at
   https://github.com/anima-wg/voucher.

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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 29 July 2023.

Copyright Notice

   Copyright (c) 2023 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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Requirements Language . . . . . . . . . . . . . . . . . . . .   5
   4.  Survey of Voucher Types . . . . . . . . . . . . . . . . . . .   5
   5.  Changes since RFC8366 . . . . . . . . . . . . . . . . . . . .   7
   6.  Voucher Artifact  . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .   9
     6.2.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  10
     6.4.  ietf-voucher SID values . . . . . . . . . . . . . . . . .  16
     6.5.  CMS Format Voucher Artifact . . . . . . . . . . . . . . .  17
   7.  Voucher Request Artifact  . . . . . . . . . . . . . . . . . .  18
     7.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .  18
     7.2.  "ietf-voucher-request" Module . . . . . . . . . . . . . .  19
     7.3.  ietf-voucher-request SID values . . . . . . . . . . . . .  25

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   8.  Design Considerations . . . . . . . . . . . . . . . . . . . .  25
     8.1.  Renewals Instead of Revocations . . . . . . . . . . . . .  25
     8.2.  Voucher Per Pledge  . . . . . . . . . . . . . . . . . . .  26
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
     9.1.  Clock Sensitivity . . . . . . . . . . . . . . . . . . . .  27
     9.2.  Protect Voucher PKI in HSM  . . . . . . . . . . . . . . .  27
     9.3.  Test Domain Certificate Validity When Signing . . . . . .  27
     9.4.  YANG Module Security Considerations . . . . . . . . . . .  27
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28
     10.1.  The IETF XML Registry  . . . . . . . . . . . . . . . . .  28
     10.2.  The YANG Module Names Registry . . . . . . . . . . . . .  28
     10.3.  The Media Types Registry . . . . . . . . . . . . . . . .  29
     10.4.  The SMI Security for S/MIME CMS Content Type Registry  .  30
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  30
     11.2.  Informative References . . . . . . . . . . . . . . . . .  32
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  34
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  34

1.  Introduction

   This document defines a strategy to securely assign a candidate
   device (pledge) to an owner using an artifact signed, directly or
   indirectly, by the pledge's manufacturer, i.e., the Manufacturer
   Authorized Signing Authority (MASA).  This artifact is known as the
   "voucher".

   The voucher artifact is a JSON [RFC8259] document that conforms with
   a data model described by YANG [RFC7950].  It may also be serialized
   to CBOR [CBOR].  It is encoded using the rules defined in [RFC8259],
   and is signed using (by default) a CMS structure [RFC5652].

   The primary purpose of a voucher is to securely convey a certificate,
   the "pinned-domain-cert" (and constrained variations), that a pledge
   can use to authenticate subsequent interactions.  A voucher may be
   useful in several contexts, but the driving motivation herein is to
   support secure onboarding mechanisms.  Assigning ownership is
   important to device onboarding mechanisms so that the pledge can
   authenticate the network that is trying to take control of it.

   The lifetimes of vouchers may vary.  In some onboarding protocols,
   the vouchers may include a nonce restricting them to a single use,
   whereas the vouchers in other onboarding protocols may have an
   indicated lifetime.  In order to support long lifetimes, this
   document recommends using short lifetimes with programmatic renewal,
   see Section 8.1.

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   This document only defines the voucher artifact, leaving it to other
   documents to describe specialized protocols for accessing it.  Some
   onboarding protocols using the voucher artifact defined in this
   document include: [ZERO-TOUCH], [SECUREJOIN], and [BRSKI].

2.  Terminology

   This document uses the following terms:

   Artifact:  Used throughout to represent the voucher as instantiated
      in the form of a signed structure.

   Bootstrapping:  See Onboarding.

   Domain:  The set of entities or infrastructure under common
      administrative control.  The goal of the onboarding protocol is to
      enable a pledge to discover and join a domain.

   Imprint:  The process where a device obtains the cryptographic key
      material to identify and trust future interactions with a network.
      This term is taken from Konrad Lorenz's work in biology with new
      ducklings: "during a critical period, the duckling would assume
      that anything that looks like a mother duck is in fact their
      mother" [Stajano99theresurrecting].  An equivalent for a device is
      to obtain the fingerprint of the network's root certification
      authority certificate.  A device that imprints on an attacker
      suffers a similar fate to a duckling that imprints on a hungry
      wolf.  Imprinting is a term from psychology and ethology, as
      described in [imprinting].

   Join Registrar (and Coordinator):  A representative of the domain
      that is configured, perhaps autonomically, to decide whether a new
      device is allowed to join the domain.  The administrator of the
      domain interfaces with a join registrar (and Coordinator) to
      control this process.  Typically, a join registrar is "inside" its
      domain.  For simplicity, this document often refers to this as
      just "registrar".

   MASA (Manufacturer Authorized Signing Authority):  The entity that,
      for the purpose of this document, signs the vouchers for a
      manufacturer's pledges.  In some onboarding protocols, the MASA
      may have an Internet presence and be integral to the onboarding
      process, whereas in other protocols the MASA may be an offline
      service that has no active role in the onboarding process.

   Onboarding:  In previous documents the term "bootstrapping" has been

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      used to describe mechanisms such as [BRSKI].  The industry has
      however, converged upon the term "onboarding", and this document
      uses that term throughout.

   Owner:  The entity that controls the private key of the "pinned-
      domain-cert" certificate conveyed by the voucher.

   Pledge:  The prospective device attempting to find and securely join
      a domain.  When shipped, it only trusts authorized representatives
      of the manufacturer.

   Registrar:  See join registrar.

   TOFU (Trust on First Use):  Where a pledge device makes no security
      decisions but rather simply trusts the first domain entity it is
      contacted by.  Used similarly to [RFC7435].  This is also known as
      the "resurrecting duckling" model.

   Voucher:  A signed statement from the MASA service that indicates to
      a pledge the cryptographic identity of the domain it should trust.

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.  Survey of Voucher Types

   A voucher is a cryptographically protected statement to the pledge
   device authorizing a zero-touch "imprint" on the join registrar of
   the domain.  The specific information a voucher provides is
   influenced by the onboarding use case.

   The voucher can impart the following information to the join
   registrar and pledge:

   Assertion Basis:  Indicates the method that protects the imprint
      (this is distinct from the voucher signature that protects the
      voucher itself).  This might include manufacturer-asserted
      ownership verification, assured logging operations, or reliance on
      pledge endpoint behavior such as secure root of trust of
      measurement.  The join registrar might use this information.  Only
      some methods are normatively defined in this document.  Other
      methods are left for future work.

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   Authentication of Join Registrar:  Indicates how the pledge can
      authenticate the join registrar.  This document defines a
      mechanism to pin the domain certificate.  Pinning a symmetric key,
      a raw key, or "CN-ID" or "DNS-ID" information (as defined in
      [RFC6125]) is left for future work.

   Anti-Replay Protections:  Time- or nonce-based information to
      constrain the voucher to time periods or bootstrap attempts.

   A number of onboarding scenarios can be met using differing
   combinations of this information.  All scenarios address the primary
   threat of a Man-in-The-Middle (MiTM) registrar gaining control over
   the pledge device.  The following combinations are "types" of
   vouchers:

    +============+=========+========+=========+========+========+=====+
    |            |Assertion|        |Registrar|        |Validity|     |
    |            |         |        |       ID|        |        |     |
    +============+=========+========+=========+========+========+=====+
    |Voucher Type|   Logged|Verified|    Trust|CN-ID or|     RTC|Nonce|
    |            |         |        |   Anchor|  DNS-ID|        |     |
    +------------+---------+--------+---------+--------+--------+-----+
    |Audit       |        X|        |        X|        |        |    X|
    +------------+---------+--------+---------+--------+--------+-----+
    |Nonceless   |        X|        |        X|        |       X|     |
    |Audit       |         |        |         |        |        |     |
    +------------+---------+--------+---------+--------+--------+-----+
    |Owner Audit |        X|       X|        X|        |       X|    X|
    +------------+---------+--------+---------+--------+--------+-----+
    |Owner ID    |         |       X|        X|       X|       X|     |
    +------------+---------+--------+---------+--------+--------+-----+
    |Bearer out- |        X|        | wildcard|wildcard|optional|  opt|
    |of-scope    |         |        |         |        |        |     |
    +------------+---------+--------+---------+--------+--------+-----+

                                  Table 1

   NOTE: All voucher types include a 'pledge ID serial-number' (not
   shown here for space reasons).

   Audit Voucher:  An Audit Voucher is named after the logging assertion
      mechanisms that the registrar then "audits" to enforce local
      policy.  The registrar mitigates a MiTM registrar by auditing that
      an unknown MiTM registrar does not appear in the log entries.
      This does not directly prevent the MiTM but provides a response
      mechanism that ensures the MiTM is unsuccessful.  The advantage is
      that actual ownership knowledge is not required on the MASA
      service.

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   Nonceless Audit Voucher:  An Audit Voucher without a validity period
      statement.  Fundamentally, it is the same as an Audit Voucher
      except that it can be issued in advance to support network
      partitions or to provide a permanent voucher for remote
      deployments.

   Ownership Audit Voucher:  An Audit Voucher where the MASA service has
      verified the registrar as the authorized owner.  The MASA service
      mitigates a MiTM registrar by refusing to generate Audit Vouchers
      for unauthorized registrars.  The registrar uses audit techniques
      to supplement the MASA.  This provides an ideal sharing of policy
      decisions and enforcement between the vendor and the owner.

   Ownership ID Voucher:  Named after inclusion of the pledge's CN-ID or
      DNS-ID within the voucher.  The MASA service mitigates a MiTM
      registrar by identifying the specific registrar (via WebPKI)
      authorized to own the pledge.

   Bearer Voucher:  A Bearer Voucher is named after the inclusion of a
      registrar ID wildcard.  Because the registrar identity is not
      indicated, this voucher type must be treated as a secret and
      protected from exposure as any 'bearer' of the voucher can claim
      the pledge device.  Publishing a nonceless bearer voucher
      effectively turns the specified pledge into a "TOFU" device with
      minimal mitigation against MiTM registrars.  Bearer vouchers are
      out of scope.

5.  Changes since RFC8366

   [RFC8366] was published in 2018 during the development of [BRSKI],
   [ZERO-TOUCH] and other work-in-progress efforts.  Since then the
   industry has matured significantly, and the in-the-field activity
   which this document supports has become known as _onboarding_ rather
   than _bootstrapping_.

   The focus of [BRSKI] was onboarding of ISP and Enterprise owned wired
   routing and switching equipment, with IoT devices being a less
   important aspect.  [ZERO-TOUCH] has focused upon onboarding of CPE
   equipment like cable modems and other larger IoT devices, again with
   smaller IoT devices being of less import.

   Since [BRSKI] was published there is now a mature effort to do
   application-level onboarding of constrained IoT devices defined by
   The Thread and Fairhair (now OCF) consortia.  The [cBRSKI] document
   has defined a version of [BRSKI] that is useable over constrained
   802.15.4 networks using CoAP and DTLS, while
   [I-D.selander-ace-ake-authz] provides for using CoAP and EDHOC on
   even more constrained devices with very constrained networks.

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   [PRM] has created a new methodology for onboarding that does not
   depend upon a synchronous connection between the Pledge and the
   Registrar.  This mechanism uses a mobile Registrar Agent that works
   to collect and transfer signed artifacts via physical travel from one
   network to another.

   Both [cBRSKI] and [PRM] require extensions to the Voucher Request and
   the resulting Voucher.  The new attribtes are required to carry the
   additional attributes and describe the extended semantics.  In
   addition [cBRSKI] uses the serialization mechanism described in
   [YANGCBOR] to produce significantly more compact artifacts.

   When the process to define [cBRSKI] and [PRM] was started, there was
   a belief that the appropriate process was to use the [RFC8040]
   _augment_ mechanism to further extend both the voucher request
   [BRSKI] and voucher [RFC8366] artifacts.  However, [PRM] needs to
   extend an enumerated type with additional values and _augment_ can
   not do this, so that was initially the impetus for this document.

   An attempt was then made to determine what would happen if one wanted
   to have a constrained version of the [PRM] voucher artifact.  The
   result was invalid YANG, with multiple definitions of the core
   attributes from the [RFC8366] voucher artifact.  After some
   discussion, it was determined that the _augment_ mechanism did not
   work, nor did it work better when [RFC8040] yang-data was replaced
   with the [RFC8971] structure mechanisms.

   After significant discussion the decision was made to simply roll all
   of the needed extensions up into this document as "RFC8366bis".

   This document therefore represents a merge of YANG definitions from
   [RFC8366], the voucher-request from [BRSKI], and then extensions to
   each of these from [cBRSKI] and [PRM].  There are some difficulties
   with this approach: this document does not attempt to establish
   rigorous semantic definitions for how some attributes are to be used,
   referring normatively instead to the other relevant documents.

6.  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 JSON-encoded or CBOR-
   encoded instance of the YANG module defined in Section 6.3 that has
   been, by default, CMS signed. [cBRSKI] definies how to encode with
   CBOR and sign the voucher with [COSE], while [jBRSKI] explains how to
   use [JWS] to do JSON signatures.

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   This format is described here as a practical basis for some uses
   (such as in NETCONF), but more to clearly indicate what vouchers look
   like in practice.  This description also serves to validate the YANG
   data model.

   [RFC8366] defined a media type and a filename extension for the CMS-
   encoded JSON type.  Which type of voucher is expected is signaled
   (where possible) in the form of a MIME Content-Type, an HTTP Accept:
   header, or more mundane methods like use of a filename extension when
   a voucher is transferred on a USB key.

6.1.  Tree Diagram

   The following tree diagram illustrates a high-level view of a voucher
   document.  The notation used in this diagram is described in
   [RFC8340].  Each node in the diagram is fully described by the YANG
   module in Section 6.3.  Please review the YANG module for a detailed
   description of the voucher format.

   module: ietf-voucher

     structure voucher:
       +-- 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
          +-- pinned-domain-pubk?              binary
          +-- pinned-domain-pubk-sha256?       binary
          +-- last-renewal-date?               yang:date-and-time

6.2.  Examples

   This section provides voucher examples for illustration purposes.
   These examples conform to the encoding rules defined in [RFC8259].

   The following example illustrates an ephemeral voucher (uses a
   nonce).  The MASA generated this voucher using the 'logged' assertion
   type, knowing that it would be suitable for the pledge making the
   request.

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   {
     "ietf-voucher:voucher": {
       "created-on": "2016-10-07T19:31:42Z",
       "assertion": "logged",
       "serial-number": "JADA123456789",
       "idevid-issuer": "base64encodedvalue==",
       "pinned-domain-cert": "base64encodedvalue==",
       "nonce": "base64encodedvalue=="
     }
   }

   The following example illustrates a non-ephemeral voucher (no nonce).
   While the voucher itself expires after two weeks, it presumably can
   be renewed for up to a year.  The MASA generated this voucher using
   the 'verified' assertion type, which should satisfy all pledges.

   {
     "ietf-voucher:voucher": {
       "created-on": "2016-10-07T19:31:42Z",
       "expires-on": "2016-10-21T19:31:42Z",
       "assertion": "verified",
       "serial-number": "JADA123456789",
       "idevid-issuer": "base64encodedvalue==",
       "pinned-domain-cert": "base64encodedvalue==",
       "domain-cert-revocation-checks": "true",
       "last-renewal-date": "2017-10-07T19:31:42Z"
     }
   }

6.3.  YANG Module

   <CODE BEGINS>
   module ietf-voucher {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-voucher";
     prefix vch;

     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-yang-structure-ext {
       prefix sx;
     }

     organization
       "IETF ANIMA Working Group";

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     contact
       "WG Web:   <https://datatracker.ietf.org/wg/anima/>
        WG List:  <mailto:anima@ietf.org>
        Author:   Kent Watsen
                  <mailto:kwatsen@juniper.net>
        Author:   Max Pritikin
                  <mailto:pritikin@cisco.com>
        Author:   Michael Richardson
                  <mailto:mcr+ietf@sandelman.ca>
        Author:   Toerless Eckert
                  <mailto:tte+ietf@cs.fau.de>";
     description
       "This module defines the format for a voucher, which is
        produced by a pledge's manufacturer or delegate (MASA)
        to securely assign a pledge to an 'owner', so that the
        pledge may establish a secure connection to the owner's
        network infrastructure.

        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 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.

        Copyright (c) 2023 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Simplified BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC 8366; see the
        RFC itself for full legal notices.";

     revision 2023-01-10 {
       description
         "updated to support new assertion enumerated type";
       reference
         "RFC ZZZZ Voucher Profile for Bootstrapping Protocols";
     }

     // Top-level statement
     sx:structure voucher {
       uses voucher-artifact-grouping;
     }

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     // Grouping defined for future augmentations

     grouping voucher-artifact-grouping {
       description
         "Grouping to allow reuse/extensions in future work.";
       container voucher {
         description
           "A voucher assigns a pledge to an owner using
            the (pinned-domain-cert) value.";
         leaf created-on {
           type yang:date-and-time;
           mandatory false;
           description
             "A value indicating the date this voucher was created.
              This node is primarily for human consumption and auditing.
              Future work MAY create verification requirements based on
              this node.";
         }
         leaf expires-on {
           type yang:date-and-time;
           must 'not(../nonce)';
           description
             "A value indicating when this voucher expires.  The node is
              optional as not all pledges support expirations, such as
              pledges lacking a reliable clock.

              If this field exists, then the pledges MUST ensure that
              the expires-on time has not yet passed. A pledge without
              an accurate clock cannot meet this requirement.

              The expires-on value MUST NOT exceed the expiration date
              of any of the listed 'pinned-domain-cert' certificates.";
         }
         leaf assertion {
           type enumeration {
             enum verified {
               value 0;
               description
                 "Indicates that the ownership has been positively
                  verified by the MASA (e.g., through sales channel
                  integration).";
             }
             enum logged {
               value 1;
               description
                 "Indicates that the voucher has been issued after
                  minimal verification of ownership or control.  The
                  issuance has been logged for detection of

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                  potential security issues (e.g., recipients of
                  vouchers might verify for themselves that unexpected
                  vouchers are not in the log).  This is similar to
                  unsecured trust-on-first-use principles but with the
                  logging providing a basis for detecting unexpected
                  events.";
             }
             enum proximity {
               value 2;
               description
                 "Indicates that the voucher has been issued after
                  the MASA verified a proximity proof provided by the
                  device and target domain.  The issuance has been
                  logged for detection of potential security issues.
                  This is stronger than just logging, because it
                  requires some verification that the pledge and owner
                  are in communication but is still dependent on
                  analysis of the logs to detect unexpected events.";
             }
             enum agent-proximity {
               value 3;
               description
                 "Indicates that the voucher has been issued
                  after the MASA has verified a statement that
                  a registrar agent has made contact with the device.
                  This type of voucher is weaker than straight
                  proximity, but stronger than logged.";
             }
           }
         }
         leaf serial-number {
           type string;
           mandatory true;
           description
             "The serial-number of the hardware.  When processing a
              voucher, a pledge MUST ensure that its serial-number
              matches this value.  If no match occurs, then the
              pledge MUST NOT process this voucher.";
         }
         leaf idevid-issuer {
           type binary;
           description
             "The Authority Key Identifier OCTET STRING (as defined in
              Section 4.2.1.1 of RFC 5280) from the pledge's IDevID
              certificate.  Optional since some serial-numbers are
              already unique within the scope of a MASA.
              Inclusion of the statistically unique key identifier
              ensures statistically unique identification of the

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              hardware.
              When processing a voucher, a pledge MUST ensure that its
              IDevID Authority Key Identifier matches this value.  If no
              match occurs, then the pledge MUST NOT process this
              voucher.
              When issuing a voucher, the MASA MUST ensure that this
              field is populated for serial-numbers that are not
              otherwise unique within the scope of the MASA.";
         }
         leaf pinned-domain-cert {
           type binary;
           mandatory false;
           description
             "An X.509 v3 certificate structure, as specified by
              RFC 5280, using Distinguished Encoding Rules (DER)
              encoding, as defined in ITU-T X.690.

              This certificate is used by a pledge to trust a Public Key
              Infrastructure in order to verify a domain certificate
              supplied to the pledge separately by the bootstrapping
              protocol.  The domain certificate MUST have this
              certificate somewhere in its chain of certificates.
              This certificate MAY be an end-entity certificate,
              including a self-signed entity.";
           reference
             "RFC 5280:
                Internet X.509 Public Key Infrastructure Certificate
                and Certificate Revocation List (CRL) Profile.
              ITU-T X.690:
                 Information technology - ASN.1 encoding rules:
                 Specification of Basic Encoding Rules (BER),
                 Canonical Encoding Rules (CER) and Distinguished
                 Encoding Rules (DER).";
         }
         leaf domain-cert-revocation-checks {
           type boolean;
           description
             "A processing instruction to the pledge that it MUST (true)
              or MUST NOT (false) verify the revocation status for the
              pinned domain certificate.  If this field is not set, then
              normal PKIX behavior applies to validation of the domain
              certificate.";
         }
         leaf nonce {
           type binary {
             length "8..32";
           }
           must 'not(../expires-on)';

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           description
             "A value that can be used by a pledge in some bootstrapping
              protocols to enable anti-replay protection.  This node is
              optional because it is not used by all bootstrapping
              protocols.

              When present, the pledge MUST compare the provided nonce
              value with another value that the pledge randomly
              generated and sent to a bootstrap server in an earlier
              bootstrapping message.  If the value is present, but
              the values do not match, then the pledge MUST NOT process
              this voucher.";
         }
         leaf pinned-domain-pubk {
           type binary;
           description
             "The pinned-domain-pubk may replace the
                pinned-domain-cert in constrained uses of
                the voucher. The pinned-domain-pubk
                is the Raw Public Key of the Registrar.
                This field is encoded as a Subject Public Key Info block
                as specified in RFC7250, in 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 pinned-domain-pubk-sha256 {
           type binary;
           description
             "The pinned-domain-pubk-sha256 is a second
                alternative to pinned-domain-cert.  In many cases the
                public key of the domain has already been transmitted
                during the key agreement process, and it is wasteful
                to transmit the public key another two times.
                The use of a hash of public key info, at 32-bytes for
                sha256 is a significant savings compared to an RSA
                public key, but is only a minor savings compared to
                a 256-bit ECDSA public-key.
                Algorithm agility is provided by extensions to this
                specification which can define a new leaf for another
                hash type.";
         }
         leaf last-renewal-date {
           type yang:date-and-time;
           must '../expires-on';
           description

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             "The date that the MASA projects to be the last date it
              will renew a voucher on. This field is merely
              informative; it is not processed by pledges.

              Circumstances may occur after a voucher is generated that
              may alter a voucher's validity period.  For instance,
              a vendor may associate validity periods with support
              contracts, which may be terminated or extended
              over time.";
         }
       } // end voucher
     } // end voucher-grouping

   }
   <CODE ENDS>

6.4.  ietf-voucher SID values

   [RFC9148] explains how to serialize YANG into CBOR, and for this a
   series of SID values are required.  While [I-D.ietf-core-sid] defines
   the management process for these values, due to the immaturity of the
   tooling around this YANG-SID mechanisms, the following values are
   considered normative.  It is believed, however, that they will not
   change.

         SID Assigned to
   --------- --------------------------------------------------
        2451 data /ietf-voucher:voucher/voucher
        2452 data /ietf-voucher:voucher/voucher/assertion
        2453 data /ietf-voucher:voucher/voucher/created-on
        2454 data .../domain-cert-revocation-checks
        2455 data /ietf-voucher:voucher/voucher/expires-on
        2456 data /ietf-voucher:voucher/voucher/idevid-issuer
        2457 data /ietf-voucher:voucher/voucher/last-renewal-date
        2458 data /ietf-voucher:voucher/voucher/nonce
        2459 data /ietf-voucher:voucher/voucher/pinned-domain-cert
        2460 data /ietf-voucher:voucher/voucher/pinned-domain-pubk
        2461 data .../pinned-domain-pubk-sha256
        2462 data /ietf-voucher:voucher/voucher/serial-number

    WARNING, obsolete definitions

   The "assertion" attribute is an enumerated type [RFC8366], and the
   current PYANG tooling does not document the valid values for this
   attribute.  In the JSON serialization, the literal strings from the
   enumerated types are used so there is no ambiguity.  In the CBOR
   serialization, a small integer is used.  This following values are

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   documented here, but the YANG module should be considered
   authoritative.  No IANA registry is provided or necessary because the
   YANG module provides for extensions.

                       +=========+=================+
                       | Integer | Assertion Type  |
                       +=========+=================+
                       | 0       | verified        |
                       +---------+-----------------+
                       | 1       | logged          |
                       +---------+-----------------+
                       | 2       | proximity       |
                       +---------+-----------------+
                       | 3       | agent-proximity |
                       +---------+-----------------+

                           Table 2: CBOR integers
                            for the "assertion"
                               attribute enum

6.5.  CMS Format Voucher Artifact

   The IETF evolution of PKCS#7 is CMS [RFC5652].  A CMS-signed voucher,
   the default type, contains a ContentInfo structure with the voucher
   content.  An eContentType of 40 indicates that the content is a JSON-
   encoded voucher.

   The signing structure is a CMS SignedData structure, as specified by
   Section 5.1 of [RFC5652], encoded using ASN.1 Distinguished Encoding
   Rules (DER), as specified in ITU-T X.690 [ITU-T.X690.2015].

   To facilitate interoperability, Section 10.3 in this document
   registers the media type "application/voucher-cms+json" and the
   filename extension ".vcj".

   The CMS structure MUST contain a 'signerInfo' structure, as described
   in Section 5.1 of [RFC5652], containing the signature generated over
   the content using a private key trusted by the recipient.  Normally,
   the recipient is the pledge and the signer is the MASA.  Another
   possible use could be as a "signed voucher request" format
   originating from the pledge or registrar toward the MASA.  Within
   this document, the signer is assumed to be the MASA.

   Note that Section 5.1 of [RFC5652] includes a discussion about how to
   validate a CMS object, which is really a PKCS7 object (cmsVersion=1).
   Intermediate systems (such the Bootstrapping Remote Secure Key
   Infrastructures [BRSKI] registrar) that might need to evaluate the
   voucher in flight MUST be prepared for such an older format.  No

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   signaling is necessary, as the manufacturer knows the capabilities of
   the pledge and will use an appropriate format voucher for each
   pledge.

   The CMS structure SHOULD also contain all of 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 third parties cannot accurately audit the
   transaction without it.

   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 a pledge-provided nonce provides a freshness
   guarantee.

7.  Voucher Request Artifact

   [BRSKI], Section 3 defined a Voucher-Request Artifact as an augmented
   artifact from the Voucher Artifact originally defined in [RFC8366].
   That definition has been moved to this document, and translated from
   YANG-DATA [RFC8040] to the SX:STRUCTURE extension [RFC8971].

7.1.  Tree Diagram

   The following tree diagram illustrates a high-level view of a voucher
   request document.  The notation used in this diagram is described in
   [RFC8340].  Each node in the diagram is fully described by the YANG
   module in Section 7.2.

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   module: ietf-voucher-request

     structure voucher:
       +-- 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
          +-- pinned-domain-pubk?                        binary
          +-- pinned-domain-pubk-sha256?                 binary
          +-- last-renewal-date?
          |       yang:date-and-time
          +-- prior-signed-voucher-request?              binary
          +-- proximity-registrar-cert?                  binary
          +-- proximity-registrar-pubk?                  binary
          +-- proximity-registrar-pubk-sha256?           binary
          +-- agent-signed-data?                         binary
          +-- agent-provided-proximity-registrar-cert?   binary
          +-- agent-sign-cert?                           binary

7.2.  "ietf-voucher-request" Module

   The ietf-voucher-request YANG module is derived from the ietf-voucher
   module.

   <CODE BEGINS>
   =============== NOTE: '\' line wrapping per RFC 8792 ================

   module ietf-voucher-request {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-voucher-request";
     prefix vcr;

     import ietf-yang-structure-ext {
       prefix sx;
     }
     import ietf-voucher {
       prefix vch;
       description
         "This module defines the format for a voucher,
          which is produced by a pledge's manufacturer or
          delegate (MASA) to securely assign a pledge to

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          an 'owner', so that the pledge may establish a secure
          connection to the owner's network infrastructure";
       reference
         "RFC 8366: Voucher Artifact for
          Bootstrapping Protocols";
     }

     organization
       "IETF ANIMA Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/anima/>
        WG List:  <mailto:anima@ietf.org>
        Author:   Kent Watsen
                  <mailto:kent+ietf@watsen.net>
        Author:   Michael H. Behringer
                  <mailto:Michael.H.Behringer@gmail.com>
        Author:   Toerless Eckert
                  <mailto:tte+ietf@cs.fau.de>
        Author:   Max Pritikin
                  <mailto:pritikin@cisco.com>
        Author:   Michael Richardson
                  <mailto:mcr+ietf@sandelman.ca>";
     description
       "This module defines the format for a voucher request.
        It is a superset of the voucher itself.
        It provides content to the MASA for consideration
        during a voucher request.

        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 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.

        Copyright (c) 2019 IETF Trust and the persons identified as
        authors of the code. All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Simplified BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see the \
                                                                     RFC
        itself for full legal notices.";

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     revision 2023-01-10 {
       description
         "Initial version";
       reference
         "RFC XXXX: Bootstrapping Remote Secure Key Infrastructure";
     }

     // Top-level statement
     sx:structure voucher {
       uses voucher-request-grouping;
     }

     // Grouping defined for future usage

     grouping voucher-request-grouping {
       description
         "Grouping to allow reuse/extensions in future work.";
       uses vch:voucher-artifact-grouping {
         refine "voucher/created-on" {
           mandatory false;
         }
         refine "voucher/pinned-domain-cert" {
           mandatory false;
           description
             "A pinned-domain-cert field
              is not valid in a voucher request, and
              any occurrence MUST be ignored";
         }
         refine "voucher/last-renewal-date" {
           description
             "A last-renewal-date field
              is not valid in a voucher request, and
              any occurrence MUST be ignored";
         }
         refine "voucher/domain-cert-revocation-checks" {
           description
             "The domain-cert-revocation-checks field
              is not valid in a voucher request, and
              any occurrence MUST be ignored";
         }
         refine "voucher/assertion" {
           mandatory false;
           description
             "Any assertion included in registrar voucher
              requests SHOULD be ignored by the MASA.";
         }
         augment "voucher" {
           description

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             "Adds leaf nodes appropriate for requesting vouchers.";
           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 voucher request
                with a proximity-registrar-cert, and the registrar
                then includes it as the prior-signed-voucher-request
                field.  This is a simple mechanism for a chain of
                trusted parties to change a voucher request, while
                maintaining the prior signature information.

                The Registrar and MASA 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.";
           }
           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.X690.1994].

                The first certificate in the Registrar TLS server
                certificate_list sequence  (the end-entity TLS
                certificate, see [RFC8446]) presented by the Registrar
                to the Pledge.
                This MUST be populated in a Pledge's voucher request
                when a proximity assertion is requested.";
           }
           leaf proximity-registrar-pubk {
             type binary;
             description
               "The proximity-registrar-pubk replaces
                the proximity-registrar-cert in constrained uses of
                the voucher-request.
                The proximity-registrar-pubk is the

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                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, but due to
                size is discouraged.";
           }
           leaf proximity-registrar-pubk-sha256 {
             type binary;
             description
               "The proximity-registrar-pubk-sha256
                is an alternative to both
                proximity-registrar-pubk and pinned-domain-cert.
                In many cases the public key of the domain has already
                been transmitted during the key agreement protocol,
                and it is wasteful to transmit the public key another
                two times.
                The use of a hash of public key info, at 32-bytes for
                sha256 is a significant savings compared to an RSA
                public key, but is only a minor savings compared to
                a 256-bit ECDSA public-key.
                Algorithm agility is provided by extensions to this
                specification which may define a new leaf for another
                hash type.";
           }
           leaf agent-signed-data {
             type binary;
             description
               "The agent-signed-data field contains a JOSE [RFC7515]
                object provided by the Registrar-Agent to the Pledge.

                This artifact is signed by the Registrar-Agent
                and contains a copy of the pledge's serial-number.";
           }
           leaf agent-provided-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 X.690.
                The first certificate in the registrar TLS server
                certificate_list sequence (the end-entity TLS
                certificate; see RFC 8446) presented by the
                registrar to the registrar-agent and provided to
                the pledge.

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                This MUST be populated in a pledge's voucher-request
                when an agent-proximity assertion is requested.";
             reference
               "ITU X.690: Information Technology - ASN.1 encoding
                rules: Specification of Basic Encoding Rules (BER),
                Canonical Encoding Rules (CER) and Distinguished
                Encoding Rules (DER)
                RFC 5280: Internet X.509 Public Key Infrastructure
                Certificate and Certificate Revocation List (CRL)
                Profile
                RFC 8446: The Transport Layer Security (TLS)
                Protocol Version 1.3";
           }
           leaf agent-sign-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 X.690.
                This certificate can be used by the pledge,
                the registrar, and the MASA to verify the signature
                of agent-signed-data. It is an optional component
                for the pledge-voucher request.
                This MUST be populated in a registrar's
                voucher-request when an agent-proximity assertion
                is requested.";
             reference
               "ITU X.690: Information Technology - ASN.1 encoding
                rules: Specification of Basic Encoding Rules (BER),
                Canonical Encoding Rules (CER) and Distinguished
                Encoding Rules (DER)
                RFC 5280: Internet X.509 Public Key Infrastructure
                Certificate and Certificate Revocation List (CRL)
                Profile";
           }
         }
       }
     }
   }
   <CODE ENDS>

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7.3.  ietf-voucher-request SID values

   [RFC9148] explains how to serialize YANG into CBOR, and for this a
   series of SID values are required.  While [I-D.ietf-core-sid] defines
   the management process for these values, due to the immaturity of the
   tooling around this YANG-SID mechanisms, the following values are
   considered normative.  It is believed, however, that they will not
   change.

         SID Assigned to
   --------- --------------------------------------------------
        2501 data /ietf-voucher-request:voucher/voucher
        2515 data .../agent-provided-proximity-registrar-cert
        2516 data .../agent-sign-cert
        2517 data .../agent-signed-data
        2502 data /ietf-voucher-request:voucher/voucher/assertion
        2503 data /ietf-voucher-request:voucher/voucher/created-on
        2504 data .../domain-cert-revocation-checks
        2505 data /ietf-voucher-request:voucher/voucher/expires-on
        2506 data .../idevid-issuer
        2507 data .../last-renewal-date
        2508 data /ietf-voucher-request:voucher/voucher/nonce
        2509 data .../pinned-domain-cert
        2518 data .../pinned-domain-pubk
        2519 data .../pinned-domain-pubk-sha256
        2510 data .../prior-signed-voucher-request
        2511 data .../proximity-registrar-cert
        2513 data .../proximity-registrar-pubk
        2512 data .../proximity-registrar-pubk-sha256
        2514 data .../serial-number

    WARNING, obsolete definitions

   The "assertion" attribute is an enumerated type, and has values as
   defined above in Table 2.

8.  Design Considerations

8.1.  Renewals Instead of Revocations

   The lifetimes of vouchers may vary.  In some onboarding protocols,
   the vouchers may be created and consumed immediately, whereas in
   other onboarding solutions, there may be a significant time delay
   between when a voucher is created and when it is consumed.  In cases
   when there is a time delay, there is a need for the pledge to ensure
   that the assertions made when the voucher was created are still
   valid.

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   A revocation artifact is generally used to verify the continued
   validity of an assertion such as a PKIX certificate, web token, or a
   "voucher".  With this approach, a potentially long-lived assertion is
   paired with a reasonably fresh revocation status check to ensure that
   the assertion is still valid.  However, this approach increases
   solution complexity, as it introduces the need for additional
   protocols and code paths to distribute and process the revocations.

   Addressing the shortcomings of revocations, this document recommends
   instead the use of lightweight renewals of short-lived non-revocable
   vouchers.  That is, rather than issue a long-lived voucher, where the
   'expires-on' leaf is set to some distant date, the expectation is for
   the MASA to instead issue a short-lived voucher, where the 'expires-
   on' leaf is set to a relatively near date, along with a promise
   (reflected in the 'last-renewal-date' field) to reissue the voucher
   again when needed.  Importantly, while issuing the initial voucher
   may incur heavyweight verification checks ("Are you who you say you
   are?"  "Does the pledge actually belong to you?"), reissuing the
   voucher should be a lightweight process, as it ostensibly only
   updates the voucher's validity period.  With this approach, there is
   only the one artifact, and only one code path is needed to process
   it; there is no possibility of a pledge choosing to skip the
   revocation status check because, for instance, the OCSP Responder is
   not reachable.

   While this document recommends issuing short-lived vouchers, the
   voucher artifact does not restrict the ability to create long-lived
   voucher, if required; however, no revocation method is described.

   Note that a voucher may be signed by a chain of intermediate CAs
   leading up to the trust anchor certificate known by the pledge.  Even
   though the voucher itself is not revocable, it may still be revoked,
   per se, if one of the intermediate CA certificates is revoked.

8.2.  Voucher Per Pledge

   The solution described herein originally enabled a single voucher to
   apply to many pledges, using lists of regular expressions to
   represent ranges of serial-numbers.  However, it was determined that
   blocking the renewal of a voucher that applied to many devices would
   be excessive when only the ownership for a single pledge needed to be
   blocked.  Thus, the voucher format now only supports a single serial-
   number to be listed.

9.  Security Considerations

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9.1.  Clock Sensitivity

   An attacker could use an expired voucher to gain control over a
   device that has no understanding of time.  The device cannot trust
   NTP as a time reference, as an attacker could control the NTP stream.

   There are three things to defend against this: 1) devices are
   required to verify that the expires-on field has not yet passed, 2)
   devices without access to time can use nonces to get ephemeral
   vouchers, and 3) vouchers without expiration times may be used, which
   will appear in the audit log, informing the security decision.

   This document defines a voucher format that contains time values for
   expirations, which require an accurate clock in order to be processed
   correctly.  Vendors planning on issuing vouchers with expiration
   values must ensure that devices have an accurate clock when shipped
   from manufacturing facilities and take steps to prevent clock
   tampering.  If it is not possible to ensure clock accuracy, then
   vouchers with expirations should not be issued.

9.2.  Protect Voucher PKI in HSM

   Pursuant the recommendation made in Section 6.1 for the MASA to be
   deployed as an online voucher signing service, it is RECOMMENDED that
   the MASA's private key used for signing vouchers is protected by a
   hardware security module (HSM).

9.3.  Test Domain Certificate Validity When Signing

   If a domain certificate is compromised, then any outstanding vouchers
   for that domain could be used by the attacker.  The domain
   administrator is clearly expected to initiate revocation of any
   domain identity certificates (as is normal in PKI solutions).

   Similarly, they are expected to contact the MASA to indicate that an
   outstanding (presumably short lifetime) voucher should be blocked
   from automated renewal.  Protocols for voucher distribution are
   RECOMMENDED to check for revocation of domain identity certificates
   before the signing of vouchers.

9.4.  YANG Module Security Considerations

   The YANG module specified in this document defines the schema for
   data that is subsequently encapsulated by a CMS signed-data content
   type, as described in Section 5 of [RFC5652].  As such, all of the
   YANG modeled data is protected from modification.

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   Implementations should be aware that the signed data is only
   protected from external modification; the data is still visible.
   This potential disclosure of information doesn't affect security so
   much as privacy.  In particular, adversaries can glean information
   such as which devices belong to which organizations and which CRL
   Distribution Point and/or OCSP Responder URLs are accessed to
   validate the vouchers.  When privacy is important, the CMS signed-
   data content type SHOULD be encrypted, either by conveying it via a
   mutually authenticated secure transport protocol (e.g., TLS
   [RFC5246]) or by encapsulating the signed-data content type with an
   enveloped-data content type (Section 6 of [RFC5652]), though details
   for how to do this are outside the scope of this document.

   The use of YANG to define data structures, via the 'yang-data'
   statement, is relatively new and distinct from the traditional use of
   YANG to define an API accessed by network management protocols such
   as NETCONF [RFC6241] and RESTCONF [RFC8040].  For this reason, these
   guidelines do not follow template described by Section 3.7 of
   [YANG-GUIDE].

10.  IANA Considerations

10.1.  The IETF XML Registry

   This document registers two URIs in the "IETF XML Registry"
   [RFC3688].

   IANA has registered the following:

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

10.2.  The YANG Module Names Registry

   This document registers two YANG module in the "YANG Module Names"
   registry [RFC6020].

   IANA is asked to registrar the following:

      name:  ietf-voucher
      namespace:  urn:ietf:params:xml:ns:yang:ietf-voucher
      prefix:  vch

      reference: :RFC 8366

   IANA is asked to register a second YANG module as follows:

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      name:  iana-voucher-assertion-type
      namespace:  urn:ietf:params:xml:ns:yang:iana-voucher-assertion-
         type
      prefix:  ianavat
      reference:  RFC XXXX

10.3.  The Media Types Registry

   This document requests IANA to update the following "Media Types"
   entry to point to the RFC number that will be assigned to this
   document:

   Type name:  application

   Subtype name:  voucher-cms+json

   Required parameters:  none

   Optional parameters:  none

   Encoding considerations:  CMS-signed JSON vouchers are ASN.1/DER
      encoded.

   Security considerations:  See Section 9

   Interoperability considerations:  The format is designed to be
      broadly interoperable.

   Published specification:  RFC 8366

   Applications that use this media type:  ANIMA, 6tisch, and NETCONF
      zero-touch imprinting systems.

   Fragment identifier considerations:  none

   Additional information:  Deprecated alias names for this type:  none

                            Magic number(s):  None

                            File extension(s):  .vcj

                            Macintosh file type code(s):  none

   Person and email address to contact for further information:  IETF AN
      IMA WG

   Intended usage:  LIMITED

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   Restrictions on usage:  NONE

   Author:  ANIMA WG

   Change controller:  IETF

   Provisional registration? (standards tree only):  NO

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

   This document requests IANA to update this registered OID in the "SMI
   Security for S/MIME CMS Content Type (1.2.840.113549.1.9.16.1)"
   registry to point to the RFC number to be assigned to this document:

             +=========+========================+============+
             | Decimal | Description            | References |
             +=========+========================+============+
             | 40      | id-ct-animaJSONVoucher | RFC 8366   |
             +---------+------------------------+------------+

                                  Table 3

11.  References

11.1.  Normative References

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

   [cBRSKI]   Richardson, M., Van der Stok, P., Kampanakis, P., and E.
              Dijk, "Constrained Bootstrapping Remote Secure Key
              Infrastructure (BRSKI)", Work in Progress, Internet-Draft,
              draft-ietf-anima-constrained-voucher-19, 2 January 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-anima-
              constrained-voucher-19>.

   [I-D.ietf-core-sid]
              Veillette, M., Pelov, A., Petrov, I., Bormann, C., and M.
              Richardson, "YANG Schema Item iDentifier (YANG SID)", Work
              in Progress, Internet-Draft, draft-ietf-core-sid-19, 26
              July 2022, <https://datatracker.ietf.org/doc/html/draft-
              ietf-core-sid-19>.

   [ITU-T.X690.2015]
              International Telecommunication Union, "Information
              Technology - ASN.1 encoding rules: Specification of Basic

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              Encoding Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", ITU-T Recommendation
              X.690, ISO/IEC 8825-1, August 2015,
              <https://www.itu.int/rec/T-REC-X.690/>.

   [jBRSKI]   Werner, T. and M. Richardson, "JWS signed Voucher
              Artifacts for Bootstrapping Protocols", Work in Progress,
              Internet-Draft, draft-ietf-anima-jws-voucher-05, 24
              October 2022, <https://datatracker.ietf.org/doc/html/
              draft-ietf-anima-jws-voucher-05>.

   [PRM]      Fries, S., Werner, T., Lear, E., and M. Richardson, "BRSKI
              with Pledge in Responder Mode (BRSKI-PRM)", Work in
              Progress, Internet-Draft, draft-ietf-anima-brski-prm-06,
              11 January 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-anima-brski-prm-06>.

   [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/rfc/rfc2119>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/rfc/rfc5652>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/rfc/rfc6020>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/rfc/rfc7950>.

   [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/rfc/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/rfc/rfc8259>.

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   [RFC8971]  Pallagatti, S., Ed., Mirsky, G., Ed., Paragiri, S.,
              Govindan, V., and M. Mudigonda, "Bidirectional Forwarding
              Detection (BFD) for Virtual eXtensible Local Area Network
              (VXLAN)", RFC 8971, DOI 10.17487/RFC8971, December 2020,
              <https://www.rfc-editor.org/rfc/rfc8971>.

   [RFC9148]  van der Stok, P., Kampanakis, P., Richardson, M., and S.
              Raza, "EST-coaps: Enrollment over Secure Transport with
              the Secure Constrained Application Protocol", RFC 9148,
              DOI 10.17487/RFC9148, April 2022,
              <https://www.rfc-editor.org/rfc/rfc9148>.

   [ZERO-TOUCH]
              Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
              Touch Provisioning (SZTP)", RFC 8572,
              DOI 10.17487/RFC8572, April 2019,
              <https://www.rfc-editor.org/rfc/rfc8572>.

11.2.  Informative References

   [CBOR]     Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949, December 2020.

              <https://www.rfc-editor.org/info/std94>

   [COSE]     Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Structures and Process", STD 96, RFC 9052, August 2022.

              Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Countersignatures", STD 96, RFC 9338, December 2022.

              <https://www.rfc-editor.org/info/std96>

   [I-D.selander-ace-ake-authz]
              Selander, G., Mattsson, J. P., Vučinić, M., Richardson,
              M., and A. Schellenbaum, "Lightweight Authorization for
              Authenticated Key Exchange.", Work in Progress, Internet-
              Draft, draft-selander-ace-ake-authz-05, 18 April 2022,
              <https://datatracker.ietf.org/doc/html/draft-selander-ace-
              ake-authz-05>.

   [imprinting]
              Wikipedia, "Wikipedia article: Imprinting", February 2018,
              <https://en.wikipedia.org/w/
              index.php?title=Imprinting_(psychology)&oldid=825757556>.

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   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/rfc/rfc7515>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/rfc/rfc3688>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/rfc/rfc5246>.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/rfc/rfc6125>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/rfc/rfc6241>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/rfc/rfc6838>.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <https://www.rfc-editor.org/rfc/rfc7435>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8040>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8340>.

   [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/rfc/rfc8366>.

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   [SECUREJOIN]
              Richardson, M., "6tisch Secure Join protocol", Work in
              Progress, Internet-Draft, draft-ietf-6tisch-dtsecurity-
              secure-join-01, 25 February 2017,
              <https://datatracker.ietf.org/doc/html/draft-ietf-6tisch-
              dtsecurity-secure-join-01>.

   [Stajano99theresurrecting]
              Stajano, F. and R. Anderson, "The Resurrecting Duckling:
              Security Issues for Ad-Hoc Wireless Networks", 1999, <http
              s://www.cl.cam.ac.uk/research/dtg/www/files/publications/
              public/files/tr.1999.2.pdf>.

   [YANG-GUIDE]
              Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/rfc/rfc8407>.

   [YANGCBOR] Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
              C., and M. Richardson, "Encoding of Data Modeled with YANG
              in the Concise Binary Object Representation (CBOR)",
              RFC 9254, DOI 10.17487/RFC9254, July 2022,
              <https://www.rfc-editor.org/rfc/rfc9254>.

Acknowledgements

   The authors would like to thank for following for lively discussions
   on list and in the halls (ordered by last name): William Atwood,
   Toerless Eckert, and Sheng Jiang.

   Russ Housley provided the upgrade from PKCS7 to CMS (RFC 5652) along
   with the detailed CMS structure diagram.

Authors' Addresses

   Kent Watsen
   Watsen Networks
   Email: kent+ietf@watsen.net

   Michael C. Richardson
   Sandelman Software
   Email: mcr+ietf@sandelman.ca
   URI:   http://www.sandelman.ca/

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   Max Pritikin
   Cisco Systems
   Email: pritikin@cisco.com

   Toerless Eckert
   Futurewei Technologies Inc.
   2330 Central Expy
   Santa Clara,  95050
   United States of America
   Email: tte+ietf@cs.fau.de

   Qiufang Ma
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing
   210012
   China
   Email: maqiufang1@huawei.com

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