ANIMA WG                                                     M. Pritikin
Internet-Draft                                                     Cisco
Intended status: Standards Track                           M. Richardson
Expires: December 15, 19, 2019                                     Sandelman
                                                            M. Behringer

                                                            S. Bjarnason
                                                          Arbor Networks
                                                               K. Watsen
                                                         Watsen Networks
                                                           June 13, 17, 2019

        Bootstrapping Remote Secure Key Infrastructures (BRSKI)
               draft-ietf-anima-bootstrapping-keyinfra-21
               draft-ietf-anima-bootstrapping-keyinfra-22

Abstract

   This document specifies automated bootstrapping of an Autonomic
   Control Plane.  To do this a remote secure key infrastructure (BRSKI)
   is created using manufacturer installed X.509 certificate, in
   combination with a manufacturer's authorizing service, both online
   and offline.  Bootstrapping a new device can occur using a routable
   address and a cloud service, or using only link-local connectivity,
   or on limited/disconnected networks.  Support for lower security
   models, including devices with minimal identity, is described for
   legacy reasons but not encouraged.  Bootstrapping is complete when
   the cryptographic identity of the new key infrastructure is
   successfully deployed to the device but the established secure
   connection can be used to deploy a locally issued certificate to the
   device as well.

Status of This Memo

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   This Internet-Draft will expire on December 15, 19, 2019.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Prior Bootstrapping Approaches  . . . . . . . . . . . . .   6
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   7
     1.3.  Scope of solution . . . . . . . . . . . . . . . . . . . .  10
       1.3.1.  Support environment . . . . . . . . . . . . . . . . .  10
       1.3.2.  Constrained environments  . . . . . . . . . . . . . .  10
       1.3.3.  Network Access Controls . . . . . . . . . . . . . . .  11
       1.3.4.  Bootstrapping is not Booting  . . . . . . . . . . . .  11
     1.4.  Leveraging the new key infrastructure / next steps  . . .  11
     1.5.  Requirements for Autonomic Network Infrastructure (ANI)
           devices . . . . . . . . . . . . . . . . . . . . . . . . .  12
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .  12
     2.1.  Behavior of a Pledge  . . . . . . . . . . . . . . . . . .  14
     2.2.  Secure Imprinting using Vouchers  . . . . . . . . . . . .  15
     2.3.  Initial Device Identifier . . . . . . . . . . . . . . . .  16
       2.3.1.  Identification of the Pledge  . . . . . . . . . . . .  16
       2.3.2.  MASA URI extension  . . . . . . . . . . . . . . . . .  17
     2.4.  Protocol Flow . . . . . . . . . . . . . . . . . . . . . .  19
     2.5.  Architectural Components  . . . . . . . . . . . . . . . .  21
       2.5.1.  Pledge  . . . . . . . . . . . . . . . . . . . . . . .  21
       2.5.2.  Join Proxy  . . . . . . . . . . . . . . . . . . . . .  21
       2.5.3.  Domain Registrar  . . . . . . . . . . . . . . . . . .  21
       2.5.4.  Manufacturer Service  . . . . . . . . . . . . . . . .  21
       2.5.5.  Public Key Infrastructure (PKI) . . . . . . . . . . .  21
     2.6.  Certificate Time Validation . . . . . . . . . . . . . . .  22
       2.6.1.  Lack of realtime clock  . . . . . . . . . . . . . . .  22
       2.6.2.  Infinite Lifetime of IDevID . . . . . . . . . . . . .  22
     2.7.  Cloud Registrar . . . . . . . . . . . . . . . . . . . . .  22
     2.8.  Determining the MASA to contact . . . . . . . . . . . . .  23
   3.  Voucher-Request artifact  . . . . . . . . . . . . . . . . . .  23
     3.1.  Nonceless Voucher Requests  . . . . . . . . . . . . . . .  24
     3.2.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .  24
     3.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  25
     3.4.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  26
   4.  Proxying details (Pledge - Proxy - Registrar) . . . . . . . .  29
     4.1.  Pledge discovery of Proxy . . . . . . . . . . . . . . . .  30
       4.1.1.  Proxy GRASP announcements . . . . . . . . . . . . . .  32
     4.2.  CoAP connection to Registrar  . . . . . . . . . . . . . .  33
     4.3.  Proxy discovery and communication of Registrar  . . . . .  33
   5.  Protocol Details (Pledge - Registrar - MASA)  . . . . . . . .  34
     5.1.  BRSKI-EST TLS establishment details . . . . . . . . . . .  36
     5.2.  Pledge Requests Voucher from the Registrar  . . . . . . .  36
     5.3.  Registrar Authorization of
           Pledge  . . . . . . . . . . . . . . . . . . . . . . . . .  37
     5.4.  BRSKI-MASA TLS establishment details  . . . . . . . . . .  38
     5.5.  Registrar Requests Voucher from MASA  . . . . . . . . . .  39
       5.5.1.  MASA renewal of expired vouchers  . . . . . . . . . .  40
       5.5.2.  MASA verification of voucher-request signature
               consistency . . . . . . . . . . . . . . . . . . . . .  41
       5.5.3.  MASA authentication of registrar (certificate)  . . .  41
       5.5.4.  MASA revocation checking of registrar (certificate) .  41
       5.5.5.  MASA verification of pledge prior-signed-voucher-
               request . . . . . . . . . . . . . . . . . . . . . . .  41
       5.5.6.  MASA pinning of registrar . . . . . . . . . . . . . .  42
       5.5.7.  MASA nonce handling . . . . . . . . . . . . . . . . .  42
     5.6.  MASA and Registrar Voucher Response . . . . . . . . . . .  42
       5.6.1.  Pledge voucher verification . . . . . . . . . . . . .  45
       5.6.2.  Pledge authentication of provisional TLS connection .  45
     5.7.  Pledge BRSKI Status Telemetry . . . . . . . . . . . . . .  46
     5.8.  Registrar audit log request . . . . . . . . . . . . . . .  47
       5.8.1.  MASA audit log response . . . . . . . . . . . . . . .  48
       5.8.2.  Registrar audit log verification  . . . . . . . . . .  49
     5.9.  EST Integration for PKI bootstrapping . . . . . . . . . .  50
       5.9.1.  EST Distribution of CA Certificates . . . . . . . . .  51
       5.9.2.  EST CSR Attributes  . . . . . . . . . . . . . . . . .  51
       5.9.3.  EST Client Certificate Request  . . . . . . . . . . .  52
       5.9.4.  Enrollment Status Telemetry . . . . . . . . . . . . .  52
       5.9.5.  Multiple certificates . . . . . . . . . . . . . . . .  53
       5.9.6.  EST over CoAP . . . . . . . . . . . . . . . . . . . .  53
   6.  Clarification of transfer-encoding  . . . . . . . . . . . . .  54
   7.  Reduced security operational modes  . . . . . . . . . . . . .  54
     6.1.
     7.1.  Trust Model . . . . . . . . . . . . . . . . . . . . . . .  54
     6.2.
     7.2.  Pledge security reductions  . . . . . . . . . . . . . . .  55
     6.3.
     7.3.  Registrar security reductions . . . . . . . . . . . . . .  55
     6.4.  56
     7.4.  MASA security reductions  . . . . . . . . . . . . . . . .  56
   7.  57
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  57
     7.1.
     8.1.  Well-known EST registration . . . . . . . . . . . . . . .  57
     7.2.  58
     8.2.  PKIX Registry . . . . . . . . . . . . . . . . . . . . . .  57
     7.3.  58
     8.3.  Pledge BRSKI Status Telemetry . . . . . . . . . . . . . .  58
     7.4.
     8.4.  DNS Service Names . . . . . . . . . . . . . . . . . . . .  58
     7.5.
     8.5.  MUD File Extension for the MASA . . . . . . . . . . . . .  58
   8.  59
   9.  Applicability to the Autonomic
       Control Plane . . . . . . . . . . . . . . . . . . . . . . . .  59
   9.
   10. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  60
     9.1.
     10.1.  MASA audit log . . . . . . . . . . . . . . . . . . . . .  60
     9.2.
     10.2.  What BRSKI-MASA reveals to the manufacturer  . . . . . . .  60
     9.3.  61
     10.3.  Manufacturers and Used or Stolen Equipment . . . . . . .  62
     9.4.
     10.4.  Manufacturers and Grey market equipment  . . . . . . . . .  63
     9.5.
     10.5.  Some mitigations for meddling by manufacturers . . . . .  64
   10.
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  65
     10.1.
     11.1.  DoS against MASA . . . . . . . . . . . . . . . . . . . .  66
     10.2.
     11.2.  Freshness in Voucher-Requests  . . . . . . . . . . . . .  66
     10.3.  67
     11.3.  Trusting manufacturers . . . . . . . . . . . . . . . . .  68
     10.4.
     11.4.  Manufacturer Maintainance of trust anchors . . . . . . .  69
   11.
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  70
   12.
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  70
     12.1.
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  70
     12.2.
     13.2.  Informative References . . . . . . . . . . . . . . . . .  72  73
   Appendix A.  IPv4 and non-ANI operations  . . . . . . . . . . . .  76
     A.1.  IPv4 Link Local addresses . . . . . . . . . . . . . . . .  76
     A.2.  Use of DHCPv4 . . . . . . . . . . . . . . . . . . . . . .  76
   Appendix B.  mDNS / DNSSD proxy discovery options . . . . . . . .  76  77
   Appendix C.  MUD Extension  . . . . . . . . . . . . . . . . . . .  77
   Appendix D.  Example Vouchers . . . . . . . . . . . . . . . . . .  79  80
     D.1.  Keys involved . . . . . . . . . . . . . . . . . . . . . .  79  80
       D.1.1.  MASA key pair for voucher signatures  . . . . . . . .  79  80
       D.1.2.  Manufacturer key pair for IDevID signatures . . . . .  79  80
       D.1.3.  Registrar key pair  . . . . . . . . . . . . . . . . .  80  81
       D.1.4.  Pledge key pair . . . . . . . . . . . . . . . . . . .  82  83
     D.2.  Example process . . . . . . . . . . . . . . . . . . . . .  83  84
       D.2.1.  Pledge to Registrar . . . . . . . . . . . . . . . . .  83  84
       D.2.2.  Registrar to MASA . . . . . . . . . . . . . . . . . .  87  88
       D.2.3.  MASA to Registrar . . . . . . . . . . . . . . . . . .  92  93
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  96  97

1.  Introduction

   BRSKI provides a solution for secure zero-touch (automated) bootstrap
   of new (unconfigured) devices that are called pledges in this
   document.

   This document primarily provides for the needs of the ISP and
   Enterprise focused ANIMA Autonomic Control Plane (ACP)
   [I-D.ietf-anima-autonomic-control-plane].  Other users of the BRSKI
   protocol will need to provide separate applicability statements that
   include privacy and security considerations appropriate to that
   deployment.  Section Section 8 9 explains the details applicability for
   this the ACP usage.

   This document describes how pledges discover (or be discovered by) an
   element of the network domain to which the pledge belongs to perform
   the bootstrap.  This element (device) is called the registrar.
   Before any other operation, pledge and registrar need to establish
   mutual trust:

   1.  Registrar authenticating the pledge: "Who is this device?  What
       is its identity?"

   2.  Registrar authorizing the pledge: "Is it mine?  Do I want it?
       What are the chances it has been compromised?"

   3.  Pledge authenticating the registrar: "What is this registrar's
       identity?"

   4.  Pledge authorizing the registrar: "Should I join it?"

   This document details protocols and messages to answer the above
   questions.  It uses a TLS connection and an PKIX (X.509v3)
   certificate (an IEEE 802.1AR [IDevID] LDevID) of the pledge to answer
   points 1 and 2.  It uses a new artifact called a "voucher" that the
   registrar receives from a "Manufacturer Authorized Signing Authority"
   and passes to the pledge to answer points 3 and 4.

   A proxy provides very limited connectivity between the pledge and the
   registrar.

   The syntactic details of vouchers are described in detail in
   [RFC8366].  This document details automated protocol mechanisms to
   obtain vouchers, including the definition of a 'voucher-request'
   message that is a minor extension to the voucher format (see
   Section 3) defined by [RFC8366].

   BRSKI results in the pledge storing an X.509 root certificate
   sufficient for verifying the registrar identity.  In the process a
   TLS connection is established that can be directly used for
   Enrollment over Secure Transport (EST).  In effect BRSKI provides an
   automated mechanism for the "Bootstrap Distribution of CA
   Certificates" described in [RFC7030] Section 4.1.1 wherein the pledge
   "MUST [...] engage a human user to authorize the CA certificate using
   out-of-band" information".  With BRSKI the pledge now can automate
   this process using the voucher.  Integration with a complete EST
   enrollment is optional but trivial.

   BRSKI is agile enough to support bootstrapping alternative key
   infrastructures, such as a symmetric key solutions, but no such
   system is described in this document.

1.1.  Prior Bootstrapping Approaches

   To literally "pull yourself up by the bootstraps" is an impossible
   action.  Similarly the secure establishment of a key infrastructure
   without external help is also an impossibility.  Today it is commonly
   accepted that the initial connections between nodes are insecure,
   until key distribution is complete, or that domain-specific keying
   material (often pre-shared keys, including mechanisms like SIM cards)
   is pre-provisioned on each new device in a costly and non-scalable
   manner.  Existing automated mechanisms are known as non-secured
   'Trust on First Use' (TOFU) [RFC7435], 'resurrecting duckling'
   [Stajano99theresurrecting] or 'pre-staging'.

   Another prior approach has been to try and minimize user actions
   during bootstrapping, but not eliminate all user-actions.  The
   original EST protocol [RFC7030] does reduce user actions during
   bootstrap but does not provide solutions for how the following
   protocol steps can be made autonomic (not involving user actions):

   o  using the Implicit Trust Anchor [RFC7030] database to authenticate
      an owner specific service (not an autonomic solution because the
      URL must be securely distributed),

   o  engaging a human user to authorize the CA certificate using out-
      of-band data (not an autonomic solution because the human user is
      involved),

   o  using a configured Explicit TA database (not an autonomic solution
      because the distribution of an explicit TA database is not
      autonomic),

   o  and using a Certificate-Less TLS mutual authentication method (not
      an autonomic solution because the distribution of symmetric key
      material is not autonomic).

   These "touch" methods do not meet the requirements for zero-touch.

   There are "call home" technologies where the pledge first establishes
   a connection to a well known manufacturer service using a common
   client-server authentication model.  After mutual authentication,
   appropriate credentials to authenticate the target domain are
   transfered to the pledge.  This creates serveral problems and
   limitations:

   o  the pledge requires realtime connectivity to the manufacturer
      service,

   o  the domain identity is exposed to the manufacturer service (this
      is a privacy concern),

   o  the manufacturer is responsible for making the authorization
      decisions (this is a liability concern),

   BRSKI addresses these issues by defining extensions to the EST
   protocol for the automated distribution of vouchers.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   The following terms are defined for clarity:

   domainID:  The domain IDentity is the 160-bit SHA-1 hash of the BIT
      STRING of the subjectPublicKey of the pinned-domain-cert leaf,
      i.e. the Registrars' certificate.  This is consistent with the
      subject key identifier (Section 4.2.1.2 [RFC5280]).

   drop ship:  The physical distribution of equipment containing the
      "factory default" configuration to a final destination.  In zero-
      touch scenarios there is no staging or pre-configuration during
      drop-ship.

   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.  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.  Securely imprinting is a
      primary focus of this document [imprinting].  The analogy to
      Lorenz's work was first noted in [Stajano99theresurrecting].

   enrollment:  The process where a device presents key material to a
      network and acquires a network specific identity.  For example
      when a certificate signing request is presented to a certification
      authority and a certificate is obtained in response.

   Pledge:  The prospective device, which has an identity installed at
      the factory.

   Voucher:  A signed artifact from the MASA that indicates to a pledge
      the cryptographic identity of the registrar it should trust.
      There are different types of vouchers depending on how that trust
      is asserted.  Multiple voucher types are defined in [RFC8366]

   Domain:  The set of entities that share a common local trust anchor.
      This includes the proxy, registrar, Domain Certificate Authority,
      Management components and any existing entity that is already a
      member of the domain.

   Domain CA:  The domain Certification Authority (CA) provides
      certification functionalities to the domain.  At a minimum it
      provides certification functionalities to a registrar and manages
      the private key that defines the domain.  Optionally, it certifies
      all elements.

   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".  Within [I-D.ietf-anima-reference-model] this is
      refered to as the "join registrar autonomic service agent".  Other
      communities use the abbreviation "JRC".

   (Public) Key Infrastructure:  The collection of systems and processes
      that sustain the activities of a public key system.  The registrar
      acts as an [RFC5280] and [RFC5272] (see section 7) "Registration
      Authority".

   Join Proxy:  A domain entity that helps the pledge join the domain.
      A join proxy facilitates communication for devices that find
      themselves in an environment where they are not provided
      connectivity until after they are validated as members of the
      domain.  For simplicity this document sometimes uses the term of
      'proxy' to indicate the join proxy.  The pledge is unaware that
      they are communicating with a proxy rather than directly with a
      registrar.

   Circuit Proxy:  A stateful implementation of the join proxy.  This is
      the assumed type of proxy.

   IPIP Proxy:  A stateless proxy alternative.

   MASA Service:  A third-party Manufacturer Authorized Signing
      Authority (MASA) service on the global Internet.  The MASA signs
      vouchers.  It also provides a repository for audit log information
      of privacy protected bootstrapping events.  It does not track
      ownership.

   Ownership Tracker:  An Ownership Tracker service on the global
      internet.  The Ownership Tracker uses business processes to
      accurately track ownership of all devices shipped against domains
      that have purchased them.  Although optional, this component
      allows vendors to provide additional value in cases where their
      sales and distribution channels allow for accurately tracking of
      such ownership.  Ownership tracking information is indicated in
      vouchers as described in [RFC8366]

   IDevID:  An Initial Device Identity X.509 certificate installed by
      the vendor on new equipment.

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

   nonced:  a voucher (or request) that contains a nonce (the normal
      case).

   nonceless:  a voucher (or request) that does not contain a nonce,
      relying upon accurate clocks for expiration, or which does not
      expire.

   manufacturer:  the term manufacturer is used throughout this document
      to be the entity that created the device.  This is typically the
      "original equipment manufacturer" or OEM, but in more complex
      situations it could be a "value added retailer" (VAR), or possibly
      even a systems integrator.  In general, it a goal of BRSKI to
      eliminate small distinctions between different sales channels.
      The reason for this is that it permits a single device, with a
      uniform firmware load, to be shipped directly to all customers.
      This eliminates costs for the manufacturer.  This also reduces the
      number of products supported in the field increasing the chance
      that firmware will be more up to date.

   ANI:  The Autonomic Network Infrastructure as defined by
      [I-D.ietf-anima-reference-model].  This document details specific
      requirements for pledges, proxies and registrars when they are
      part of an ANI.

   offline:  When an architectural component cannot perform realtime
      communications with a peer, either due to network connectivity or
      because the peer is turned off, the operation is said to be
      occurring offline.

1.3.  Scope of solution

1.3.1.  Support environment

   This solution (BRSKI) can support large router platforms with multi-
   gigabit inter-connections, mounted in controlled access data centers.
   But this solution is not exclusive to large equipment: it is intended
   to scale to thousands of devices located in hostile environments,
   such as ISP provided CPE devices which are drop-shipped to the end
   user.  The situation where an order is fulfilled from distributed
   warehouse from a common stock and shipped directly to the target
   location at the request of a domain owner is explicitly supported.
   That stock ("SKU") could be provided to a number of potential domain
   owners, and the eventual domain owner will not know a-priori which
   device will go to which location.

   The bootstrapping process can take minutes to complete depending on
   the network infrastructure and device processing speed.  The network
   communication itself is not optimized for speed; for privacy reasons,
   the discovery process allows for the pledge to avoid announcing its
   presence through broadcasting.

   Nomadic or mobile devices often need to aquire credentials to access
   the network at the new location.  An example of this is mobile phone
   roaming among network operators, or even between cell towers.  This
   is usually called handoff.  BRSKI does not provide a low-latency
   handoff which is usually a requirement in such situations.  For these
   solutions BRSKI can be used to create a relationship (an LDevID) with
   the "home" domain owner.  The resulting credentials are then used to
   provide credentials more appropriate for a low-latency handoff.

1.3.2.  Constrained environments

   Questions have been posed as to whether this solution is suitable in
   general for Internet of Things (IoT) networks.  This depends on the
   capabilities of the devices in question.  The terminology of
   [RFC7228] is best used to describe the boundaries.

   The solution described in this document is aimed in general at non-
   constrained (i.e., class 2+) devices operating on a non-Challenged
   network.  The entire solution as described here is not intended to be
   useable as-is by constrained devices operating on challenged networks
   (such as 802.15.4 LLNs).

   Specifically, there are protocol aspects described here that might
   result in congestion collapse or energy-exhaustion of intermediate
   battery powered routers in an LLN.  Those types of networks SHOULD
   NOT use this solution.  These limitations are predominately related
   to the large credential and key sizes required for device
   authentication.  Defining symmetric key techniques that meet the
   operational requirements is out-of-scope but the underlying protocol
   operations (TLS handshake and signing structures) have sufficient
   algorithm agility to support such techniques when defined.

   The imprint protocol described here could, however, be used by non-
   energy constrained devices joining a non-constrained network (for
   instance, smart light bulbs are usually mains powered, and speak
   802.11).  It could also be used by non-constrained devices across a
   non-energy constrained, but challenged network (such as 802.15.4).
   The certificate contents, and the process by which the four questions
   above are resolved do apply to constrained devices.  It is simply the
   actual on-the-wire imprint protocol that could be inappropriate.

1.3.3.  Network Access Controls

   This document presumes that network access control has either already
   occurred, is not required, or is integrated by the proxy and
   registrar in such a way that the device itself does not need to be
   aware of the details.  Although the use of an X.509 Initial Device
   Identity is consistant with IEEE 802.1AR [IDevID], and allows for
   alignment with 802.1X network access control methods, its use here is
   for pledge authentication rather than network access control.
   Integrating this protocol with network access control, perhaps as an
   Extensible Authentication Protocol (EAP) method (see [RFC3748]), is
   out-of-scope.

1.3.4.  Bootstrapping is not Booting

   This document describes "bootstrapping" as the protocol used to
   obtain a local trust anchor.  It is expected that this trust anchor,
   along with any additional configuration information subsequently
   installed, is persisted on the device across system restarts
   ("booting").  Bootstrapping occurs only infrequently such as when a
   device is transfered to a new owner or has been reset to factory
   default settings.

1.4.  Leveraging the new key infrastructure / next steps

   As a result of the protocol described herein, the bootstrapped
   devices have the Domain CA trust anchor in common.  An end entity
   certificate has optionally been issued from the Domain CA.  This
   makes it possible to securely deploy functionalities across the
   domain, e.g:

   o  Device management.

   o  Routing authentication.

   o  Service discovery.

   The major beneficiary is that it possible to use the credentials
   deployed by this protocol to secure the Autonomic Control Plane (ACP)
   ([I-D.ietf-anima-autonomic-control-plane]).

1.5.  Requirements for Autonomic Network Infrastructure (ANI) devices

   The BRSKI protocol can be used in a number of environments.  Some of
   the options in this document is the result of requirements that are
   out of the ANI scope.  This section defines the base requirements for
   ANI devices.

   For devices that intend to become part of an Autonomic Network
   Infrastructure (ANI) ([I-D.ietf-anima-reference-model]) that includes
   an Autonomic Control Plane
   ([I-D.ietf-anima-autonomic-control-plane]), the BRSKI protocol MUST
   be implemented.

   The pledge must perform discovery of the proxy as described in
   Section 4.1 using GRASP M_FLOOD announcements.

   Upon successfully validating a voucher artiface, a status telemetry
   MUST be returned.  See Section 5.7.

   An ANIMA ANI pledge MUST implement the EST automation extensions
   described in Section 5.9.  They supplement the [RFC7030] EST to
   better support automated devices that do not have an end user.

   The ANI Join Registrar ASA MUST support all the BRSKI and above
   listed EST operations.

   All ANI devices SHOULD support the BRSKI proxy function, using
   circuit proxies over the ACP.  (See Section 4.3)

2.  Architectural Overview

   The logical elements of the bootstrapping framework are described in
   this section.  Figure 1 provides a simplified overview of the
   components.

                                              +------------------------+
      +--------------Drop Ship--------------->| Vendor Service         |
      |                                       +------------------------+
      |                                       | M anufacturer|         |
      |                                       | A uthorized  |Ownership|
      |                                       | S igning     |Tracker  |
      |                                       | A uthority   |         |
      |                                       +--------------+---------+
      |                                                      ^
      |                                                      |  BRSKI-
      V                                                      |   MASA
   +-------+     ............................................|...
   |       |     .                                           |  .
   |       |     .  +------------+       +-----------+       |  .
   |       |     .  |            |       |           |       |  .
   |Pledge |     .  |   Join     |       | Domain    <-------+  .
   |       |     .  |   Proxy    |       | Registrar |          .
   |       <-------->............<-------> (PKI RA)  |          .
   |       |        |        BRSKI-EST   |           |          .
   |       |     .  |            |       +-----+-----+          .
   |IDevID |     .  +------------+             | e.g. RFC7030   .
   |       |     .           +-----------------+----------+     .
   |       |     .           | Key Infrastructure         |     .
   |       |     .           | (e.g., PKI Certificate     |     .
   +-------+     .           |       Authority)           |     .
                 .           +----------------------------+     .
                 .                                              .
                 ................................................
                               "Domain" components

   Figure 1

   We assume a multi-vendor network.  In such an environment there could
   be a Manufacturer Service for each manufacturer that supports devices
   following this document's specification, or an integrator could
   provide a generic service authorized by multiple manufacturers.  It
   is unlikely that an integrator could provide Ownership Tracking
   services for multiple manufacturers due to the required sales channel
   integrations necessary to track ownership.

   The domain is the managed network infrastructure with a Key
   Infrastructure the pledge is joining.  The domain provides initial
   device connectivity sufficient for bootstrapping through a proxy.
   The domain registrar authenticates the pledge, makes authorization
   decisions, and distributes vouchers obtained from the Manufacturer
   Service.  Optionally the registrar also acts as a PKI Registration
   Authority.

2.1.  Behavior of a Pledge

   The pledge goes through a series of steps, which are outlined here at
   a high level.

                  ------------
                 /  Factory   \
                 \  default   /
                  -----+------
                       |
                +------v-------+
                | (1) Discover |
   +------------>              |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (2) Identity |
   ^------------+              |
   | rejected   +------+-------+
   |                   |
   |            +------v-------+
   |            | (3) Request  |
   |            |     Join     |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (4) Imprint  |
   ^------------+              |
   | Bad MASA   +------+-------+
   | response          |  send Voucher Status Telemetry
   |            +------v-------+
   |            | (5) Enroll   |<---+ (non-error HTTP codes  )
   ^------------+              |\___/ (e.g. 201 'Retry-After')
   | Enroll     +------+-------+
   | Failure           |
   |              -----v------
   |             /  Enrolled  \
   ^------------+             |
    Factory      \------------/
    reset

   Figure 2: pledge state diagram

   State descriptions for the pledge are as follows:

   1.  Discover a communication channel to a registrar.

   2.  Identify itself.  This is done by presenting an X.509 IDevID
       credential to the discovered registrar (via the proxy) in a TLS
       handshake.  (The registrar credentials are only provisionally
       accepted at this time).

   3.  Request to join the discovered registrar.  A unique nonce is
       included ensuring that any responses can be associated with this
       particular bootstrapping attempt.

   4.  Imprint on the registrar.  This requires verification of the
       manufacturer service provided voucher.  A voucher contains
       sufficient information for the pledge to complete authentication
       of a registrar.  This document details this step in depth.

   5.  Enroll.  After imprint an authenticated TLS (HTTPS) connection
       exists between pledge and registrar.  Enrollment over Secure
       Transport (EST) [RFC7030] is then used to obtain a domain
       certificate from a registrar.

   The pledge is now a member of, and can be managed by, the domain and
   will only repeat the discovery aspects of bootstrapping if it is
   returned to factory default settings.

   This specification details integration with EST enrollment so that
   pledges can optionally obtain a locally issued certificate, although
   any REST interface could be integrated in future work.

2.2.  Secure Imprinting using Vouchers

   A voucher is a cryptographically protected artifact (a digital
   signature) to the pledge device authorizing a zero-touch imprint on
   the registrar domain.

   The format and cryptographic mechanism of vouchers is described in
   detail in [RFC8366].

   Vouchers provide a flexible mechanism to secure imprinting: the
   pledge device only imprints when a voucher can be validated.  At the
   lowest security levels the MASA can indiscriminately issue vouchers
   and log claims of ownership by domains.  At the highest security
   levels issuance of vouchers can be integrated with complex sales
   channel integrations that are beyond the scope of this document.  The
   sales channel integration would verify actual (legal) ownership of
   the pledge by the domain.  This provides the flexibility for a number
   of use cases via a single common protocol mechanism on the pledge and
   registrar devices that are to be widely deployed in the field.  The
   MASA services have the flexibility to leverage either the currently
   defined claim mechanisms or to experiment with higher or lower
   security levels.

   Vouchers provide a signed but non-encrypted communication channel
   among the pledge, the MASA, and the registrar.  The registrar
   maintains control over the transport and policy decisions allowing
   the local security policy of the domain network to be enforced.

2.3.  Initial Device Identifier

   Pledge authentication and pledge voucher-request signing is via a
   PKIX certificate installed during the manufacturing process.  This is
   the 802.1AR Initial Device Identifier (IDevID), and it provides a
   basis for authenticating the pledge during the protocol exchanges
   described here.  There is no requirement for a common root PKI
   hierarchy.  Each device manufacturer can generate its own root
   certificate.  Specifically, the IDevID enables:

   1.  Uniquely identifying the pledge by the Distinguished Name (DN)
       and subjectAltName (SAN) parameters in the IDevID.  The unique
       identification of a pledge in the voucher objects are derived
       from those parameters as described below.

   2.  Provides a cryptographic authentication of the pledge to the
       Registrar (see Section 5.3).

   3.  Secure auto-discovery of the pledge's MASA by the registrar (see
       Section 2.8).

   4.  Signing of voucher-request by the pledge's IDevID (see
       Section 3).

   5.  Provides a cryptographic authentication of the pledge to the MASA
       (see Section 5.5.5).

   Section 7.2.13 of [IDevID] discusses keyUsage and extendedKeyUsage
   extensions in the IDevID certificate.  Any restrictions included
   reduce the utility of the IDevID and so this specification RECOMMENDS
   that no key usage restrictions be included.  Additionally, [RFC5280]
   section 4.2.1.3 does not require key usage restrictions for end
   entity certificates.

2.3.1.  Identification of the Pledge

   In the context of BRSKI, pledges are uniquely identified by a
   "serial-number".  This serial-number is used both in the "serial-
   number" field of voucher or voucher-requests (see Section 3) and in
   local policies on registrar or MASA (see Section 5).

   The following fields are defined in [IDevID] and [RFC5280]:

   o  The subject field's DN encoding MUST include the "serialNumber"
      attribute with the device's unique serial number.  (from [IDevID]
      section 7.2.8, and [RFC5280] section 4.1.2.4's list of standard
      attributes)

   o  The subject-alt field's encoding MAY include a non-critical
      version of the RFC4108 defined HardwareModuleName.  (from [IDevID]
      section 7.2.9) If the IDevID is stored in a Trusted Platform
      Module (TPM), then this field MAY contain the TPM identification
      rather than the device's serial number.  If both fields are
      present, then the subject field takes precedence.

   and they are used as follows by the pledge to build the "serial-
   number" that is placed in the voucher-request.  In order to build it,
   the fields need to be converted into a serial-number of "type
   string".  The following methods are used depending on the first
   available IDevID certificate field (attempted in this order):

   1.  [RFC4519] section 2.31 provides an example ("WI-3005") of the
       Distinguished Name "serialNumber" attribute.  [RFC4514] indicates
       this is a printable string so no encoding is necessary.

   2.  The HardwareModuleName hwSerialNum OCTET STRING.  This value is
       base64 encoded to convert it to a printable string format.

   The above process to locate the serial-number MUST be performed by
   the pledge when filling out the voucher-request.  Signed voucher-
   requests are always passed up to the MASA.

   As explained in Section 5.5 the Registrar MUST extract the serial-
   number again itself from the pledge's TLS certificate.  It can
   consult the serial-number in the pledge-request if there are any
   possible confusion about the source of the serial-number (hwSerialNum
   vs serialNumber).

2.3.2.  MASA URI extension

   This docucment defines a new PKIX non-critical certificate extension
   to carry the MASA URI.  This extension is intended to be used in the
   IDevID certificate.  The URI is represented as described in
   Section 7.4 of [RFC5280].

   Any Internationalized Resource Identifiers (IRIs) MUST be mapped to
   URIs as specified in Section 3.1 of [RFC3987] before they are placed
   in the certificate extension.  The IRI provides the authority
   information.  The BRSKI "/.well-known" tree ([RFC5785]) is described
   in Section 5.

   As explained in [RFC5280] section 7.4, a complete IRI SHOULD be in
   this extension, including the scheme, iauthority, and ipath.  As a
   consideration to constrained systems, this MAY be reduced to only the
   iauthority, in which case a scheme of "https://" and ipath of
   "/.well-known/est" is to be assumed, as explained in section
   Section 5.

   The registrary can assume that only the iauthority is present in the
   extension, if there are no slash ("/") characters in the extension.

   Section 7.4 of [RFC5280] calls out various schemes that MUST be
   supported, including ldap, http and ftp.  However, the registrar MUST
   use https for the BRSKI-MASA connection.

   The new extension is identified as follows:

   <CODE BEGINS>

   MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
   internet(1) security(5) mechanisms(5) pkix(7)
   id-mod(0) id-mod-MASAURLExtn2016(TBD) }

   DEFINITIONS IMPLICIT TAGS ::= BEGIN

   -- EXPORTS ALL --

   IMPORTS
   EXTENSION
   FROM PKIX-CommonTypes-2009
   { iso(1) identified-organization(3) dod(6) internet(1)
   security(5) mechanisms(5) pkix(7) id-mod(0)
   id-mod-pkixCommon-02(57) }

   id-pe
   FROM PKIX1Explicit-2009
   { iso(1) identified-organization(3) dod(6) internet(1)
   security(5) mechanisms(5) pkix(7) id-mod(0)
   id-mod-pkix1-explicit-02(51) } ;
   MASACertExtensions EXTENSION ::= { ext-MASAURL, ... }
   ext-MASAURL EXTENSION ::= { SYNTAX MASAURLSyntax
   IDENTIFIED BY id-pe-masa-url }

   id-pe-masa-url OBJECT IDENTIFIER ::= { id-pe TBD }

   MASAURLSyntax ::= IA5String

   END

   <CODE ENDS>

   The choice of id-pe is based on guidance found in Section 4.2.2 of
   [RFC5280], "These extensions may be used to direct applications to
   on-line information about the issuer or the subject".  The MASA URL
   is precisely that: online information about the particular subject.

2.4.  Protocol Flow

   A representative flow is shown in Figure 3:

   +--------+         +---------+    +------------+     +------------+
   | Pledge |         | Circuit |    | Domain     |     | Vendor     |
   |        |         | Join    |    | Registrar  |     | Service    |
   |        |         | Proxy   |    |  (JRC)     |     | (MASA)     |
   +--------+         +---------+    +------------+     +------------+
     |                     |                   |           Internet |
   [discover]              |                   |                    |
     |<-RFC4862 IPv6 addr  |                   |                    |
     |<-RFC3927 IPv4 addr  | Appendix A        |  Legend            |
     |-------------------->|                   |  C - circuit       |
     | optional: mDNS query| Appendix B        |      join proxy    |
     | RFC6763/RFC6762     |                   |  P - provisional   |
     |<--------------------|                   |    TLS connection  |
     | GRASP M_FLOOD       |                   |                    |
     |   periodic broadcast|                   |                    |
   [identity]              |                   |                    |
     |<------------------->C<----------------->|                    |
     |         TLS via the Join Proxy          |                    |
     |<--Registrar TLS server authentication---|                    |
   [PROVISIONAL accept of server cert]         |                    |
     P---X.509 client authentication---------->|                    |
   [request join]                              |                    |
     P---Voucher Request(w/nonce for voucher)->|                    |
     P                  /-------------------   |                    |
     P                  |                 [accept device?]          |
     P                  |                 [contact Vendor]          |
     P                  |                      |--Pledge ID-------->|
     P                  |                      |--Domain ID-------->|
     P                  |                      |--optional:nonce--->|
     P              optional:                  |     [extract DomainID]
     P        can occur in advance             |     [update audit log]
     P            if nonceleess                |                    |
     P                  |                      |<- voucher ---------|
     P                  \-------------------   | w/nonce if provided|
     P<------voucher---------------------------|                    |
   [imprint]                                   |                    |
     |-------voucher status telemetry--------->|                    |
     |                                         |<-device audit log--|
     |                             [verify audit log and voucher]   |
     |<--------------------------------------->|                    |
   [enroll]                                    |                    |
     | Continue with RFC7030 enrollment        |                    |
     | using now bidirectionally authenticated |                    |
     | TLS session.                            |                    |
   [enrolled]                                  |                    |

   Figure 3

2.5.  Architectural Components

2.5.1.  Pledge

   The pledge is the device that is attempting to join.  Until the
   pledge completes the enrollment process, it has link-local network
   connectivity only to the proxy.

2.5.2.  Join Proxy

   The join proxy provides HTTPS connectivity between the pledge and the
   registrar.  A circuit proxy mechanism is described in Section 4.
   Additional mechanisms, including a CoAP mechanism and a stateless
   IPIP mechanism are the subject of future work.

2.5.3.  Domain Registrar

   The domain's registrar operates as the BRSKI-MASA client when
   requesting vouchers from the MASA (see Section 5.4).  The registrar
   operates as the BRSKI-EST server when pledges request vouchers (see
   Section 5.1).  The registrar operates as the BRSKI-EST server
   "Registration Authority" if the pledge requests an end entity
   certificate over the BRSKI-EST connection (see Section 5.9).

   The registrar uses an Implicit Trust Anchor database for
   authenticating the BRSKI-MASA TLS connection MASA certificate.  The
   registrar uses a different Implicit Trust Anchor database for
   authenticating the BRSKI-EST TLS connection pledge client
   certificate.  Configuration or distribution of these trust anchor
   databases is out-of-scope of this specification.

2.5.4.  Manufacturer Service

   The Manufacturer Service provides two logically seperate functions:
   the Manufacturer Authorized Signing Authority (MASA) described in
   Section 5.5 and Section 5.6, and an ownership tracking/auditing
   function described in Section 5.7 and Section 5.8.

2.5.5.  Public Key Infrastructure (PKI)

   The Public Key Infrastructure (PKI) administers certificates for the
   domain of concerns, providing the trust anchor(s) for it and allowing
   enrollment of pledges with domain certificates.

   The voucher provides a method for the distribution of a single PKI
   trust anchor (as the "pinned-domain-cert").  A distribution of the
   full set of current trust anchors is possible using the optional EST
   integration.

   The domain's registrar acts as an [RFC5272] Registration Authority,
   requesting certificates for pledges from the Key Infrastructure.

   The expectations of the PKI are unchanged from EST [[RFC7030]].  This
   document does not place any additional architectural requirements on
   the Public Key Infrastructure.

2.6.  Certificate Time Validation

2.6.1.  Lack of realtime clock

   Many devices when bootstrapping do not have knowledge of the current
   time.  Mechanisms such as Network Time Protocols cannot be secured
   until bootstrapping is complete.  Therefore bootstrapping is defined
   in a method that does not require knowledge of the current time.  A
   pledge MAY ignore all time stamps in the voucher and in the
   certificate validity periods if it does not know the current time.

   The pledge is exposed to dates in the following five places:
   registrar certificate notBefore, registrar certificiate notAfter,
   voucher created-on, and voucher expires-on.  Additionally, CMS
   signatures contain a signingTime.

   If the voucher contains a nonce then the pledge MUST confirm the
   nonce matches the original pledge voucher-request.  This ensures the
   voucher is fresh.  See Section 5.2.

2.6.2.  Infinite Lifetime of IDevID

   [RFC5280] explains that long lived pledge certificates "SHOULD be
   assigned the GeneralizedTime value of 99991231235959Z".  Registrars
   MUST support such lifetimes and SHOULD support ignoring pledge
   lifetimes if they did not follow the RFC5280 recommendations.

   For example, IDevID may have incorrect lifetime of N <= 3 years,
   rendering replacement pledges from storage useless after N years
   unless registrars support ignoring such a lifetime.

2.7.  Cloud Registrar

   There exist operationally open network wherein devices gain
   unauthenticated access to the internet at large.  In these use cases
   the management domain for the device needs to be discovered within
   the larger internet.  These are less likely within the anima scope
   but may be more important in the future.

   There are additionally some greenfield situations involving an
   entirely new installation where a device may have some kind of
   management uplink that it can use (such as via 3G network for
   instance).  In such a future situation, the device might use this
   management interface to learn that it should configure itself to
   become the local registrar.

   In order to support these scenarios, the pledge MAY contact a well
   known URI of a cloud registrar if a local registrar cannot be
   discovered or if the pledge's target use cases do not include a local
   registrar.

   If the pledge uses a well known URI for contacting a cloud registrar
   an Implicit Trust Anchor database (see [RFC7030]) MUST be used to
   authenticate service as described in [RFC6125].  This is consistent
   with the human user configuration of an EST server URI in [RFC7030]
   which also depends on RFC6125.

2.8.  Determining the MASA to contact

   The registrar needs to be able to contact a MASA that is trusted by
   the pledge in order to obtain vouchers.  There are three mechanisms
   described:

   The device's Initial Device Identifier (IDevID) will normally contain
   the MASA URL as detailed in Section 2.3.  This is the RECOMMENDED
   mechanism.

   If the registrar is integrated with [I-D.ietf-opsawg-mud] and the
   pledge IDevID contains the id-pe-mud-url then the registrar MAY
   attempt to obtain the MASA URL from the MUD file.  The MUD file
   extension for the MASA URL is defined in Appendix C.

   It can be operationally difficult to ensure the necessary X.509
   extensions are in the pledge's IDevID due to the difficulty of
   aligning current pledge manufacturing with software releases and
   development.  As a final fallback the registrar MAY be manually
   configured or distributed with a MASA URL for each manufacturer.
   Note that the registrar can only select the configured MASA URL based
   on the trust anchor -- so manufacturers can only leverage this
   approach if they ensure a single MASA URL works for all pledge's
   associated with each trust anchor.

3.  Voucher-Request artifact

   Voucher-requests are how vouchers are requested.  The semantics of
   the vouchers are described below, in the YANG model.

   A pledge forms the "pledge voucher-request" and submits it to the
   registrar.

   The registrar in turn forms the "registrar voucher-request", and
   submits it to the MASA.

   The "proximity-registrar-cert" leaf is used in the pledge voucher-
   requests.  This provides a method for the pledge to assert the
   registrar's proximity.

   The "prior-signed-voucher-request" leaf is used in registrar voucher-
   requests.  If present, it is the signed pledge voucher-request.  This
   provides a method for the registrar to forward the pledge's signed
   request to the MASA.  This completes transmission of the signed
   "proximity-registrar-cert" leaf.

   Unless otherwise signaled (outside the voucher-request artifact), the
   signing structure is as defined for vouchers, see [RFC8366].

3.1.  Nonceless Voucher Requests

   A registrar MAY also retrieve nonceless vouchers by sending nonceless
   voucher-requests to the MASA in order to obtain vouchers for use when
   the registrar does not have connectivity to the MASA.  No "prior-
   signed-voucher-request" leaf would be included.  The registrar will
   also need to know the serial number of the pledge.  This document
   does not provide a mechanism for the registrar to learn that in an
   automated fashion.  Typically this will be done via scanning of bar-
   code or QR-code on packaging, or via some sales channel integration.

3.2.  Tree Diagram

   The following tree diagram illustrates a high-level view of a
   voucher-request document.  The voucher-request builds upon the
   voucher artifact described in [RFC8366].  The tree diagram is
   described in [RFC8340].  Each node in the diagram is fully described
   by the YANG module in Section 3.4.  Please review the YANG module for
   a detailed description of the voucher-request format.

   module: ietf-voucher-request

     grouping voucher-request-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
          +-- prior-signed-voucher-request?    binary
          +-- proximity-registrar-cert?        binary

3.3.  Examples

   This section provides voucher-request examples for illustration
   purposes.  For detailed examples, see Appendix D.2.  These examples
   conform to the encoding rules defined in [RFC7951].

   Example (1)  The following example illustrates a pledge voucher-
                request.  The assertion leaf is indicated as 'proximity'
                and the registrar's TLS server certificate is included
                in the 'proximity-registrar-cert' leaf.  See
                Section 5.2.

   {
       "ietf-voucher-request:voucher": {
           "nonce": "62a2e7693d82fcda2624de58fb6722e5",
           "created-on": "2017-01-01T00:00:00.000Z",
           "proximity-registrar-cert": "base64encodedvalue=="
       }
   }

   Example (2)  The following example illustrates a registrar voucher-
                request.  The 'prior-signed-voucher-request' leaf is
                populated with the pledge's voucher-request (such as the
                prior example).  The pledge's voucher-request is a
                binary object.  In the JSON encoding used here it must
                be base64 encoded.  The nonce, created-on and assertion
                is carried forward.  The serial-number is extracted from
                the pledge's Client Certificate from the TLS connection.
                See Section 5.5.

   {
       "ietf-voucher-request:voucher": {
           "nonce": "62a2e7693d82fcda2624de58fb6722e5",
           "created-on": "2017-01-01T00:00:02.000Z",
           "idevid-issuer": "base64encodedvalue=="
           "serial-number": "JADA123456789"
           "prior-signed-voucher-request": "base64encodedvalue=="
       }
   }

   Example (3)  The following example illustrates a registrar voucher-
                request.  The 'prior-signed-voucher-request' leaf is not
                populated with the pledge's voucher-request nor is the
                nonce leaf.  This form might be used by a registrar
                requesting a voucher when the pledge can not communicate
                with the registrar (such as when it is powered down, or
                still in packaging), and therefore could not submit a
                nonce.  This scenario is most useful when the registrar
                is aware that it will not be able to reach the MASA
                during deployment.  See Section 5.5.

   {
       "ietf-voucher-request:voucher": {
           "created-on":    "2017-01-01T00:00:02.000Z",
           "idevid-issuer": "base64encodedvalue=="
           "serial-number": "JADA123456789"
       }
   }

3.4.  YANG Module

   Following is a YANG [RFC7950] module formally extending the [RFC8366]
   voucher into a voucher-request.

<CODE BEGINS> file "ietf-voucher-request@2018-02-14.yang"
module ietf-voucher-request {
  yang-version 1.1;

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

  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;
    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
        conn ection to the owner's network infrastructure";

    reference "RFC YYYY: Voucher Profile for Bootstrapping Protocols";
  }

  organization
   "IETF ANIMA Working Group";

  contact
   "WG Web:   <http://tools.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 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', 'MAY', and 'OPTIONAL' in
    the module text are to be interpreted as described in RFC 2119.

    Copyright (c) 2017 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.";

  revision "2018-02-14" {
    description
     "Initial version";
    reference
     "RFC XXXX: Voucher Profile for Bootstrapping Protocols";
  }

  // Top-level statement
  rc:yang-data voucher-request-artifact {
    uses voucher-request-grouping;
  }

  // Grouping defined for future usage
  grouping voucher-request-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;
      }

      refine "voucher/domain-cert-revocation-checks" {
        description "The domain-cert-revocation-checks field
                     is not valid in a voucher request, and
                     any occurance MUST be ignored";
      }

      refine "voucher/assertion" {
        mandatory false;
        description "Any assertion included in voucher
              requests SHOULD be ignored by the MASA.";
      }

      augment "voucher"  {
        description
          "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 in 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-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 a proximity assertion is
             requested.";
        }
      }
    }
  }

}

<CODE ENDS>

4.  Proxying details (Pledge - Proxy - Registrar)

   The role of the proxy is to facilitate communications.  The proxy
   forwards packets between the pledge and a registrar that has been
   provisioned to the proxy via GRASP discovery.

   This section defines a stateful proxy mechanism which is refered to
   as a "circuit" proxy.

   The proxy does not terminate the TLS handshake: it passes streams of
   bytes onward without examination.  A proxy MUST NOT assume any
   specific TLS version.

   A Registrar can directly provide the proxy announcements described
   below, in which case the announced port can point directly to the
   Registrar itself.  In this scenario the pledge is unaware that there
   is no proxing occuring.  This is useful for Registrars servicing
   pledges on directly connected networks.

   As a result of the proxy Discovery process in Section 4.1.1, the port
   number exposed by the proxy does not need to be well known, or
   require an IANA allocation.

   During the discovery of the Registrar by the Join Proxy, the Join
   Proxy will also learn which kinds of proxy mechanisms are available.
   This will allow the Join Proxy to use the lowest impact mechanism
   which the Join Proxy and Registrar have in common.

   In order to permit the proxy functionality to be implemented on the
   maximum variety of devices the chosen mechanism SHOULD use the
   minimum amount of state on the proxy device.  While many devices in
   the ANIMA target space will be rather large routers, the proxy
   function is likely to be implemented in the control plane CPU of such
   a device, with available capabilities for the proxy function similar
   to many class 2 IoT devices.

   The document [I-D.richardson-anima-state-for-joinrouter] provides a
   more extensive analysis and background of the alternative proxy
   methods.

4.1.  Pledge discovery of Proxy

   The result of discovery is a logical communication with a registrar,
   through a proxy.  The proxy is transparent to the pledge.  The
   communication between the pledge is over IPv6 Link-Local addresses.

   To discover the proxy the pledge performs the following actions:

   1.  MUST: Obtains a local address using IPv6 methods as described in
       [RFC4862] IPv6 Stateless Address AutoConfiguration.  Use of
       [RFC4941] temporary addresses is encouraged.  To limit pervasive
       monitoring ( [RFC7258]), a new temporary address MAY use a short
       lifetime (that is, set TEMP_PREFERRED_LIFETIME to be short).
       Pledges will generally prefer use of IPv6 Link-Local addresses,
       and discovery of proxy will be by Link-Local mechanisms.  IPv4
       methods are described in Appendix A

   2.  MUST: Listen for GRASP M_FLOOD ([I-D.ietf-anima-grasp])
       announcements of the objective: "AN_Proxy".  See section
       Section 4.1.1 for the details of the objective.  The pledge MAY
       listen concurrently for other sources of information, see
       Appendix B.

   Once a proxy is discovered the pledge communicates with a registrar
   through the proxy using the bootstrapping protocol defined in
   Section 5.

   While the GRASP M_FLOOD mechanism is passive for the pledge, the
   optional other methods (mDNS, and IPv4 methods) are active.  The
   pledge SHOULD run those methods in parallel with listening to for the
   M_FLOOD.  The active methods SHOULD exponentially back-off to a
   maximum of one hour to avoid overloading the network with discovery
   attempts.  Detection of change of physical link status (ethernet
   carrier for instance) SHOULD reset the exponential back off.

   The pledge could discover more than one proxy on a given physical
   interface.  The pledge can have a multitude of physical interfaces as
   well: a layer-2/3 ethernet switch may have hundreds of physical
   ports.

   Each possible proxy offer SHOULD be attempted up to the point where a
   voucher is received: while there are many ways in which the attempt
   may fail, it does not succeed until the voucher has been validated.

   The connection attempts via a single proxy SHOULD exponentially back-
   off to a maximum of one hour to avoid overloading the network
   infrastructure.  The back-off timer for each MUST be independent of
   other connection attempts.

   Connection attempts SHOULD be run in parallel to avoid head of queue
   problems wherein an attacker running a fake proxy or registrar could
   perform protocol actions intentionally slowly.  The pledge SHOULD
   continue to listen to for additional GRASP M_FLOOD messages during
   the connection attempts.

   Once a connection to a registrar is established (e.g. establishment
   of a TLS session key) there are expectations of more timely
   responses, see Section 5.2.

   Once all discovered services are attempted (assuming that none
   succeeded) the device MUST return to listening for GRASP M_FLOOD.  It
   SHOULD periodically retry the manufacturer specific mechanisms.  The
   pledge MAY prioritize selection order as appropriate for the
   anticipated environment.

4.1.1.  Proxy GRASP announcements

   A proxy uses the DULL GRASP M_FLOOD mechanism to announce itself.
   This announcement can be within the same message as the ACP
   announcement detailed in [I-D.ietf-anima-autonomic-control-plane].
   The M_FLOOD is formatted as follows:

  [M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000,
              ["AN_Proxy", 4, 1, ""],
              [O_IPv6_LOCATOR,
                h'fe800000000000000000000000000001', IPPROTO_TCP, 4443]]

   Figure 6b: Proxy Discovery

   The formal CDDL [I-D.ietf-cbor-cddl] definition is:

 flood-message = [M_FLOOD, session-id, initiator, ttl,
                  +[objective, (locator-option / [])]]

 objective = ["AN_Proxy", objective-flags, loop-count,
                                        objective-value]

 ttl             = 180000     ; 180,000 ms (3 minutes)
 initiator = ACP address to contact Registrar
 objective-flags   = sync-only  ; as in GRASP spec
 sync-only         =  4         ; M_FLOOD only requires synchronization
 loop-count        =  1         ; one hop only
 objective-value   =  any       ; none

 locator-option    = [ O_IPv6_LOCATOR, ipv6-address,
                     transport-proto, port-number ]
 ipv6-address      = the v6 LL of the Proxy
 $transport-proto /= IPPROTO_TCP   ; note this can be any value from the
                                  ; IANA protocol registry, as per
                                  ; [GRASP] section 2.9.5.1, note 3.
 port-number      = selected by Proxy

   Figure 6c: AN_Proxy CDDL

   On a small network the Registrar MAY include the GRASP M_FLOOD
   announcements to locally connected networks.

   The $transport-proto above indicates the method that the pledge-
   proxy-registrar will use.  The TCP method described here is
   mandatory, and other proxy methods, such as CoAP methods not defined
   in this document are optional.  Other methods MUST NOT be enabled
   unless the Join Registrar ASA indicates support for them in it's own
   announcement.

4.2.  CoAP connection to Registrar

   The use of CoAP to connect from pledge to registrar is out of scope
   for this document, and is described in future work.  See
   [I-D.ietf-anima-constrained-voucher].

4.3.  Proxy discovery and communication of Registrar

   The registrar SHOULD announce itself so that proxies can find it and
   determine what kind of connections can be terminated.

   The registrar announces itself using ACP instance of GRASP using
   M_FLOOD messages.  ANI proxies MUST support GRASP discovery of
   registrars.

   The M_FLOOD is formatted as follows:

   [M_FLOOD, 12340815, h'fda379a6f6ee00000200000064000001', 180000,
               ["AN_join_registrar", 4, 255, "EST-TLS"],
               [O_IPv6_LOCATOR,
                 h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 80]]

   Figure 7a: Registrar Discovery

   The formal CDDL definition is:

   flood-message = [M_FLOOD, session-id, initiator, ttl,
                    +[objective, (locator-option / [])]]

   objective = ["AN_join_registrar", objective-flags, loop-count,
                                          objective-value]

   initiator = ACP address to contact Registrar
   objective-flags = sync-only  ; as in GRASP spec
   sync-only =  4               ; M_FLOOD only requires synchronization
   loop-count      = 255        ; mandatory maximum
   objective-value = text       ; name of the (list of) of supported
                                ; protocols: "EST-TLS" for RFC7030.

   Figure 7: AN_join_registrar CDDL

   The M_FLOOD message MUST be sent periodically.  The period is subject
   to network administrator policy (EST server configuration).  It must
   be sufficiently low that the aggregate amount of periodic M_FLOODs
   from all EST servers causes negligible traffic across the ACP.

   Here are some examples of locators for illustrative purposes.  Only
   the first one ($transport-protocol = 6, TCP) is defined in this
   document and is mandatory to implement.

   locator1  = [O_IPv6_LOCATOR, fd45:1345::6789, 6,  443]
   locator2  = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683]
   locator3  = [O_IPv6_LOCATOR, fe80::1234, 41, nil]

   A protocol of 6 indicates that TCP proxying on the indicated port is
   desired.

   Registrars MUST announce the set of protocols that they support.
   They MUST support TCP traffic.

   Registrars MUST accept HTTPS/EST traffic on the TCP ports indicated.

   Registrars MUST support ANI TLS circuit proxy and therefore BRSKI
   across HTTPS/TLS native across the ACP.

   In the ANI, the Autonomic Control Plane (ACP) secured instance of
   GRASP ([I-D.ietf-anima-grasp]) MUST be used for discovery of ANI
   registrar ACP addresses and ports by ANI proxies.  The TCP leg of the
   proxy connection between ANI proxy and ANI registrar therefore also
   runs across the ACP.

5.  Protocol Details (Pledge - Registrar - MASA)

   The pledge MUST initiate BRSKI after boot if it is unconfigured.  The
   pledge MUST NOT automatically initiate BRSKI if it has been
   configured or is in the process of being configured.

   BRSKI is described as extensions to EST [RFC7030].  The goal of these
   extensions is to reduce the number of TLS connections and crypto
   operations required on the pledge.  The registrar implements the
   BRSKI REST interface within the same "/.well-known" URI tree as the
   existing EST URIs as described in EST [RFC7030] section 3.2.2.  The
   communication channel between the pledge and the registrar is
   referred to as "BRSKI-EST" (see Figure 1).

   The communication channel between the registrar and MASA is similarly
   described as extensions to EST within the same "/.well-known" tree.
   For clarity this channel is referred to as "BRSKI-MASA".  (See
   Figure 1).

   MASA URI is "https://" iauthority "/.well-known/est".

   BRSKI uses existing CMS message formats for existing EST operations.
   BRSKI uses JSON [RFC7159] for all new operations defined here, and
   voucher formats.

   While EST section 3.2 does not insist upon use of HTTP 1.1 persistent
   connections, BRSKI-EST connections SHOULD use persistent connections.
   The intention of this guidance is to ensure the provisional TLS state
   occurs only once, and that the subsequent resolution of the provision
   state is not subject to a MITM attack during a critical phase.

   Summarized automation extensions for the BRSKI-EST flow are:

   o  The pledge either attempts concurrent connections via each
      discovered proxy, or it times out quickly and tries connections in
      series, as explained at the end of Section 5.1.

   o  The pledge provisionally accepts the registrar certificate during
      the TLS handshake as detailed in Section 5.1.

   o  The pledge requests and validates a voucher using the new REST
      calls described below.

   o  The pledge completes authentication of the server certificate as
      detailed in Section 5.6.1.  This moves the BRSKI-EST TLS
      connection out of the provisional state.

   o  Mandatory boostrap steps conclude with voucher status telemetry
      (see Section 5.7).

   The BRSKI-EST TLS connection can now be used for EST enrollment.

   The extensions for a registrar (equivalent to EST server) are:

   o  Client authentication is automated using Initial Device Identity
      (IDevID) as per the EST certificate based client authentication.
      The subject field's DN encoding MUST include the "serialNumber"
      attribute with the device's unique serial number.

   o  In the language of [RFC6125] this provides for a SERIALNUM-ID
      category of identifier that can be included in a certificate and
      therefore that can also be used for matching purposes.  The
      SERIALNUM-ID whitelist is collated according to manufacturer trust
      anchor since serial numbers are not globally unique.

   o  The registrar requests and validates the voucher from the MASA.

   o  The registrar forwards the voucher to the pledge when requested.

   o  The registrar performs log verifications in addition to local
      authorization checks before accepting optional pledge device
      enrollment requests.

5.1.  BRSKI-EST TLS establishment details

   The pledge establishes the TLS connection with the registrar through
   the circuit proxy (see Section 4) but the TLS handshake is with the
   registrar.  The BRSKI-EST pledge is the TLS client and the BRSKI-EST
   registrar is the TLS server.  All security associations established
   are between the pledge and the registrar regardless of proxy
   operations.

   Establishment of the BRSKI-EST TLS connection is as specified in EST
   [RFC7030] section 4.1.1 "Bootstrap Distribution of CA Certificates"
   [RFC7030] wherein the client is authenticated with the IDevID
   certificate, and the EST server (the registrar) is provisionally
   authenticated with an unverified server certificate.

   The pledge maintains a security paranoia concerning the provisional
   state, and all data received, until a voucher is received and
   verified as specified in Section 5.6.1

   A Pledge that can connect to multiple registries concurrently, SHOULD
   do so.  Some devices may be unable to do so for lack of threading, or
   resource issues.  Concurrent connections defeat atttempts by a
   malicious proxy from causing a TCP Slowloris-like attack (see
   [slowloris]).

   A pledge that can not maintain as many connections as there are
   eligible proxies.  If no connection is making process after 5 seconds
   then the pledge SHOULD drop the oldest connection and go on to a
   different proxy: the proxy that has been communicated with least
   recently.  If there were no other proxies discovered, the pledge MAY
   continue to wait, as long as it is concurrently listening for new
   proxy announcements.

5.2.  Pledge Requests Voucher from the Registrar

   When the pledge bootstraps it makes a request for a voucher from a
   registrar.

   This is done with an HTTPS POST using the operation path value of
   "/.well-known/est/requestvoucher".

   The pledge voucher-request Content-Type is:

   application/voucher-cms+json  The request is a "YANG-defined JSON
      document that has been signed using a CMS structure" as described
      in Section 3 using the JSON encoding described in [RFC7951].  This
      voucher media type is defined in [RFC8366] and is also used for
      the pledge voucher-request.  The pledge SHOULD sign the request
      using the Section 2.3 credential.

   Registrar impementations SHOULD anticipate future media types but of
   course will simply fail the request if those types are not yet known.

   The pledge SHOULD include an [RFC7231] section 5.3.2 "Accept" header
   indicating the acceptable media type for the voucher response.  The
   "application/voucher-cms+json" media type is defined in [RFC8366] but
   constrained voucher formats are expected in the future.  Registrar's
   and MASA's are expected to be flexible in what they accept.

   The pledge populates the voucher-request fields as follows:

   created-on:  Pledges that have a realtime clock are RECOMMENDED to
      populate this field.  This provides additional information to the
      MASA.

   nonce:  The pledge voucher-request MUST contain a cryptographically
      strong random or pseudo-random number nonce. (see [RFC4086]) Doing
      so ensures Section 2.6.1 functionality.  The nonce MUST NOT be
      reused for multiple bootstrapping attempts.  (The registrar
      voucher-request MAY omit the nonce as per Section 3.1)

   proximity-registrar-cert:  In a pledge voucher-request this is the
      first certificate in the TLS server 'certificate_list' sequence
      (see [RFC5246]) presented by the registrar to the pledge.  This
      MUST be populated in a pledge voucher-request if the "proximity"
      assertion is populated.

   All other fields MAY be omitted in the pledge voucher-request.

   An example JSON payload of a pledge voucher-request is in Section 3.3
   Example 1.

   The registrar validates the client identity as described in EST
   [RFC7030] section 3.3.2.  The registrar confirms that the 'proximity'
   assertion and associated 'proximity-registrar-cert' are correct.

5.3.  Registrar Authorization of Pledge

   In a fully automated network all devices must be securely identified
   and authorized to join the domain.

   A Registrar accepts or declines a request to join the domain, based
   on the authenticated identity presented.  Automated acceptance
   criteria include:

   o  allow any device of a specific type (as determined by the X.509
      IDevID),

   o  allow any device from a specific vendor (as determined by the
      X.509 IDevID),

   o  allow a specific device from a vendor (as determined by the X.509
      IDevID) against a domain white list.  (The mechanism for checking
      a shared white list potentially used by multiple Registrars is out
      of scope).

   If these validations fail the registrar SHOULD respond with an
   appropriate HTTP error code.

   If authorization is successful the registrar obtains a voucher from
   the MASA service (see Section 5.5) and returns that MASA signed
   voucher to the pledge as described in Section 5.6.

5.4.  BRSKI-MASA TLS establishment details

   The BRSKI-MASA TLS connection is a 'normal' TLS connection
   appropriate for HTTPS REST interfaces.  The registrar initiates the
   connection and uses the MASA URL obtained as described in Section 2.8
   for [RFC6125] authentication of the MASA.

   The primary method of registrar "authentication" by the MASA is
   detailed in Section 5.5.  As detailed in Section 10 11 the MASA might
   find it necessary to request additional registrar authentication.

   The MASA and the registrars SHOULD be prepared to support TLS client
   certificate authentication and/or HTTP Basic or Digest authentication
   as described in [RFC7030] for EST clients.  This connection MAY also
   have no client authentication at all (Section 6.4) 7.4)

   The authentication of the BRSKI-MASA connection does not affect the
   voucher-request process, as voucher-requests are already signed by
   the registrar.  Instead, this authentication provides access control
   to the audit log.

   Implementors are advised that contacting the MASA is to establish a
   secured REST connection with a web service and that there are a
   number of authentication models being explored within the industry.
   Registrars are RECOMMENDED to fail gracefully and generate useful
   administrative notifications or logs in the advent of unexpected HTTP
   401 (Unauthorized) responses from the MASA.

5.5.  Registrar Requests Voucher from MASA

   When a registrar receives a pledge voucher-request it in turn submits
   a registrar voucher-request to the MASA service via an HTTPS RESTful
   interface ([RFC7231]).

   This is done with an HTTP POST using the operation path value of
   "/.well-known/est/requestvoucher".

   The voucher media type "application/voucher-cms+json" is defined in
   [RFC8366] and is also used for the registrar voucher-request.  It is
   a JSON document that has been signed using a CMS structure.  The
   registrar MUST sign the registrar voucher-request.  The entire
   registrar certificate chain, up to and including the Domain CA, MUST
   be included in the CMS structure.

   MASA impementations SHOULD anticipate future media types but of
   course will simply fail the request if those types are not yet known.

   The Registrar SHOULD include an [RFC7231] section 5.3.2 "Accept"
   header indicating the response media types that are acceptable.  This
   list SHOULD be the entire list presented to the Registrar in the
   Pledge's original request (see Section 5.2) but MAY be a subset.
   MASA's are expected to be flexible in what they accept.

   The registrar populates the voucher-request fields as follows:

   created-on:  Registrars are RECOMMENDED to populate this field.  This
      provides additional information to the MASA.

   nonce:  This is the value from the pledge voucher-request.  The
      registrar voucher-request MAY omit the nonce as per Section 3.1)

   serial-number:  The serial number of the pledge the registrar would
      like a voucher for.  The registrar determines this value by
      parsing the authenticated pledge IDevID certificate.  See
      Section 2.3.  The registrar MUST verify that the serial number
      field it parsed matches the serial number field the pledge
      provided in its voucher-request.  This provides a sanity check
      useful for detecting error conditions and logging.  The registrar
      MUST NOT simply copy the serial number field from a pledge voucher
      request as that field is claimed but not certified.

   idevid-issuer:  The idevid-issuer value from the pledge certificate
      is included to ensure a statistically unique identity.

   prior-signed-voucher-request:  The signed pledge voucher-request
      SHOULD be included in the registrar voucher-request.  (NOTE: what
      is included is the complete pledge voucher-request, inclusive of
      the 'assertion', 'proximity-registrar-cert', etc wrapped by the
      pledge's original signature).  If a signed voucher-request was not
      recieved from the pledge then this leaf is omitted from the
      registrar voucher request.

   A nonceless registrar voucher-request MAY be submitted to the MASA.
   Doing so allows the registrar to request a voucher when the pledge is
   offline, or when the registrar anticipates not being able to connect
   to the MASA while the pledge is being deployed.  Some use cases
   require the registrar to learn the appropriate IDevID SerialNumber
   field and appropriate 'Accept header' field values from the physical
   device labeling or from the sales channel (out-of-scope for this
   document).

   All other fields MAY be omitted in the registrar voucher-request.

   Example JSON payloads of registrar voucher-requests are in
   Section 3.3 Examples 2 through 4.

   The MASA verifies that the registrar voucher-request is internally
   consistent but does not necessarily authenticate the registrar
   certificate since the registrar is not known to the MASA in advance.
   The MASA performs the actions and validation checks described in the
   following sub-sections before issuing a voucher.

5.5.1.  MASA renewal of expired vouchers

   As described in [RFC8366] vouchers are normally short lived to avoid
   revocation issues.  If the request is for a previous (expired)
   voucher using the same registrar then the request for a renewed
   voucher SHOULD be automatically authorized.  The MASA has sufficient
   information to determine this by examining the request, the registrar
   authentication, and the existing audit log.  The issuance of a
   renewed voucher is logged as detailed in Section 5.6.

   To inform the MASA that existing vouchers are not to be renewed one
   can update or revoke the registrar credentials used to authorize the
   request (see Section 5.5.3 and Section 5.5.4).  More flexible methods
   will likely involve sales channel integration and authorizations
   (details are out-of-scope of this document).

5.5.2.  MASA verification of voucher-request signature consistency

   The MASA MUST verify that the registrar voucher-request is signed by
   a registrar.  This is confirmed by verifying that the id-kp-cmcRA
   extended key usage extension field (as detailed in EST RFC7030
   section 3.6.1) exists in the certificate of the entity that signed
   the registrar voucher-request.  This verification is only a
   consistency check that the unauthenticated domain CA intended the
   voucher-request signer to be a registrar.  Performing this check
   provides value to the domain PKI by assuring the domain administrator
   that the MASA service will only respect claims from authorized
   Registration Authorities of the domain.

   The MASA verifies that the domain CA certificate is included in the
   CMS structure as detailed in Section 5.5.

5.5.3.  MASA authentication of registrar (certificate)

   If a nonceless voucher-request is submitted the MASA MUST
   authenticate the registrar as described in either EST [RFC7030]
   section 3.2, section 3.3, or by validating the registrar's
   certificate used to sign the registrar voucher-request.  Any of these
   methods reduce the risk of DDoS attacks and provide an authenticated
   identity as an input to sales channel integration and authorizations
   (details are out-of-scope of this document).

   In the nonced case, validation of the registrar MAY be omitted if the
   device policy is to accept audit-only vouchers.

5.5.4.  MASA revocation checking of registrar (certificate)

   As noted in Section 5.5.3 the MASA performs registrar authentication
   in a subset of situations (e.g. nonceless voucher requests).  Normal
   PKIX revocation checking is assumed during either EST client
   authentication or voucher-request signature validation.  Similarly,
   as noted in Section 5.5.2, the MASA performs normal PKIX revocation
   checking during signature consistency checks (a signature by a
   registrar certificate that has been revoked is an inconsistency).

5.5.5.  MASA verification of pledge prior-signed-voucher-request

   The MASA MAY verify that the registrar voucher-request includes the
   'prior-signed-voucher-request' field.  If so the prior-signed-
   voucher-request MUST include a 'proximity-registrar-cert' that is
   consistent with the certificate used to sign the registrar voucher-
   request.  Additionally the voucher-request serial-number leaf MUST
   match the pledge serial-number that the MASA extracts from the
   signing certificate of the prior-signed-voucher-request.  The MASA is
   aware of which pledges support signing of their voucher requests and
   can use this information to confirm proximity of the pledge with the
   registrar, thus ensuring that the BRSKI-EST TLS connection has no
   man-in-the-middle.

   If these checks succeed the MASA updates the voucher and audit log
   assertion leafs with the "proximity" assertion.

5.5.6.  MASA pinning of registrar

   The registrar's certificate chain is extracted from the signature
   method.  The chain includes the domain CA certificate as specified in
   Section 5.5.  This certificate is used to populate the "pinned-
   domain-cert" of the voucher being issued.  The domainID (e.g., hash
   of the root public key) is determined from the pinned-domain-cert and
   is used to update the audit log.

5.5.7.  MASA nonce handling

   The MASA does not verify the nonce itself.  If the registrar voucher-
   request contains a nonce, and the prior-signed-voucher-request is
   exist, then the MASA MUST verify that the nonce is consistent.
   (Recall from above that the voucher-request might not contain a
   nonce, see Section 5.5 and Section 5.5.3).

   The MASA MUST use the nonce from the registrar voucher-request for
   the resulting voucher and audit log.  The prior-signed-voucher-
   request nonce is ignored during this operation.

5.6.  MASA and Registrar Voucher Response

   The MASA voucher response to the registrar is forwarded without
   changes to the pledge; therefore this section applies to both the
   MASA and the registrar.  The HTTP signaling described applies to both
   the MASA and registrar responses.  A registrar either caches prior
   MASA responses or dynamically requests a new voucher based on local
   policy (it does not generate or sign a voucher).  Registrar
   evaluation of the voucher itself is purely for transparency and audit
   purposes to further inform log verification (see Section 5.8.2) and
   therefore a registrar could accept future voucher formats that are
   opaque to the registrar.

   If the voucher-request is successful, the server (MASA responding to
   registrar or registrar responding to pledge) response MUST contain an
   HTTP 200 response code.  The server MUST answer with a suitable 4xx
   or 5xx HTTP [RFC2616] error code when a problem occurs.  In this
   case, the response data from the MASA MUST be a plaintext human-
   readable (ASCII, English) error message containing explanatory
   information describing why the request was rejected.

   The registrar MAY respond with an HTTP 202 ("the request has been
   accepted for processing, but the processing has not been completed")
   as described in EST [RFC7030] section 4.2.3 wherein the client "MUST
   wait at least the specified 'Retry-After' time before repeating the
   same request".  (see [RFC7231] section 6.6.4) The pledge is
   RECOMMENDED to provide local feedback (blinked LED etc) during this
   wait cycle if mechanisms for this are available.  To prevent an
   attacker registrar from significantly delaying bootstrapping the
   pledge MUST limit the 'Retry-After' time to 60 seconds.  Ideally the
   pledge would keep track of the appropriate Retry-After header values
   for any number of outstanding registrars but this would involve a
   state table on the pledge.  Instead the pledge MAY ignore the exact
   Retry-After value in favor of a single hard coded value (a registrar
   that is unable to complete the transaction after the first 60 seconds
   has another chance a minute later).  A pledge SHOULD only maintain a
   202 retry-state for up to 4 days, which is longer than a long
   weekend, after which time the enrollment attempt fails and the pledge
   returns to discovery state.

   In order to avoid infinite redirect loops, which a malicious
   registrar might do in order to keep the pledge from discovering the
   correct registrar, the pledge MUST NOT follow more than one
   redirection (3xx code) to another web origins.  EST supports
   redirection but requires user input; this change allows the pledge to
   follow a single redirection without a user interaction.

   A 403 (Forbidden) response is appropriate if the voucher-request is
   not signed correctly, stale, or if the pledge has another outstanding
   voucher that cannot be overridden.

   A 404 (Not Found) response is appropriate when the request is for a
   device that is not known to the MASA.

   A 406 (Not Acceptable) response is appropriate if a voucher of the
   desired type or using the desired algorithms (as indicated by the
   Accept: headers, and algorithms used in the signature) cannot be
   issued such as because the MASA knows the pledge cannot process that
   type.  The registrar SHOULD use this response if it determines the
   pledge is unacceptable due to inventory control, MASA audit logs, or
   any other reason.

   A 415 (Unsupported Media Type) response is approriate for a request
   that has a voucher-request or accept encoding that is not understood.

   The voucher response format is as indicated in the submitted accept
   header or based on the MASA's prior understanding of proper format
   for this Pledge.  Only the [RFC8366] "application/voucher-cms+json"
   media type is defined at this time.  The syntactic details of
   vouchers are described in detail in [RFC8366].  For example, the
   voucher consists of:

   {
     "ietf-voucher:voucher": {
       "nonce": "62a2e7693d82fcda2624de58fb6722e5",
       "assertion": "logging"
       "pinned-domain-cert": "base64encodedvalue=="
       "serial-number": "JADA123456789"
     }
   }

   The MASA populates the voucher fields as follows:

   nonce:  The nonce from the pledge if available.  See Section 5.5.7.

   assertion:  The method used to verify assertion.  See Section 5.5.5.

   pinned-domain-cert:  The domain CA cert.  See Section 5.5.6.  This
      figure is illustrative, for an example, see Appendix D.2

   serial-number:  The serial-number as provided in the voucher-request.
      Also see Section 5.5.5.

   domain-cert-revocation-checks:  Set as appropriate for the pledge's
      capabilities and as documented in [RFC8366].  The MASA MAY set
      this field to 'false' since setting it to 'true' would require
      that revocation information be available to the pledge and this
      document does not make normative requirements for [RFC6961] or
      equivalent integrations.

   expires-on:  This is set for nonceless vouchers.  The MASA ensures
      the voucher lifetime is consistent with any revocation or pinned-
      domain-cert consistency checks the pledge might perform.  See
      section Section 2.6.1.  There are three times to consider: (a) a
      configured voucher lifetime in the MASA, (b) the expiry time for
      the registrar's certificate, (c) any certificate revocation
      information (CRL) lifetime.  The expires-on field SHOULD be before
      the earliest of these three values.  Typically (b) will be some
      significant time in the future, but (c) will typically be short
      (on the order of a week or less).  The RECOMMENDED period for (a)
      is on the order of 20 minutes, so it will typically determine the
      lifespan of the resulting voucher.  20 minutes is sufficent time
      to reach the post-provisional state in the pledge, at which point
      there is an established trust relationship between pledge and
      registrar.  The subsequent operations can take as long as required
      from that point onwards.  The lifetime of the voucher has no
      impact on the lifespan of the ownership relationship.

   Whenever a voucher is issued the MASA MUST update the audit log
   appropriately.  The internal state requirements to maintain the audit
   log are out-of-scope.  See Section 5.8.1 for a discussion of
   reporting the log to a registrar.

5.6.1.  Pledge voucher verification

   The pledge MUST verify the voucher signature using the manufacturer
   installed trust anchor(s) associated with the manufacturer's MASA
   (this is likely included in the pledge's firmware).  Management of
   the manufacter installed trust anchor(s) is out-of-scope of this
   document; this protocol does not update these trust anchor(s).

   The pledge MUST verify the serial-number field of the signed voucher
   matches the pledge's own serial-number.

   The pledge MUST verify that the voucher nonce field is accurate and
   matches the nonce the pledge submitted to this registrar, or that the
   voucher is nonceless (see Section 6.2). 7.2).

   The pledge MUST be prepared to parse and fail gracefully from a
   voucher response that does not contain a 'pinned-domain-cert' field.
   The pledge MUST be prepared to ignore additional fields that it does
   not recognize.

5.6.2.  Pledge authentication of provisional TLS connection

   The 'pinned-domain-cert' element of the voucher contains the domain
   CA's public key.  The pledge MUST use the 'pinned-domain-cert' trust
   anchor to immediately complete authentication of the provisional TLS
   connection.

   If a registrar's credentials cannot be verified using the pinned-
   domain-cert trust anchor from the voucher then the TLS connection is
   immediately discarded and the pledge abandons attempts to bootstrap
   with this discovered registrar.  The pledge SHOULD send voucher
   status telemetry (described below) before closing the TLS connection.
   The pledge MUST attempt to enroll using any other proxies it has
   found.  It SHOULD return to the same proxy again after attempting
   with other proxies.  Attempts should be attempted in the exponential
   backoff described earlier.  Attempts SHOULD be repeated as failure
   may be the result of a temporary inconsistently (an inconsistently
   rolled registrar key, or some other mis-configuration).  The
   inconsistently could also be the result an active MITM attack on the
   EST connection.

   The registrar MUST use a certificate that chains to the pinned-
   domain-cert as its TLS server certificate.

   The pledge's PKIX path validation of a registrar certificate's
   validity period information is as described in Section 2.6.1.  Once
   the PKIX path validation is successful the TLS connection is no
   longer provisional.

   The pinned-domain-cert MAY be installed as an trust anchor for future
   operations such as enrollment (e.g.  [RFC7030] as recommended) or
   trust anchor management or raw protocols that do not need full PKI
   based key management.  It can be used to authenticate any dynamically
   discovered EST server that contain the id-kp-cmcRA extended key usage
   extension as detailed in EST RFC7030 section 3.6.1; but to reduce
   system complexity the pledge SHOULD avoid additional discovery
   operations.  Instead the pledge SHOULD communicate directly with the
   registrar as the EST server.  The 'pinned-domain-cert' is not a
   complete distribution of the [RFC7030] section 4.1.3 CA Certificate
   Response, which is an additional justification for the recommendation
   to proceed with EST key management operations.  Once a full CA
   Certificate Response is obtained it is more authoritative for the
   domain than the limited 'pinned-domain-cert' response.

5.7.  Pledge BRSKI Status Telemetry

   The domain is expected to provide indications to the system
   administrators concerning device lifecycle status.  To facilitate
   this it needs telemetry information concerning the device's status.

   To indicate pledge status regarding the voucher, the pledge MUST post
   a status message.

   The posted data media type: application/json

   The client HTTP POSTs the following to the server at the EST well
   known URI "/voucher_status".  The Status field indicates if the
   voucher was acceptable.  If it was not acceptable the Reason string
   indicates why.  In the failure case this message may be sent to an
   unauthenticated, potentially malicious registrar and therefore the
   Reason string SHOULD NOT provide information beneficial to an
   attacker.  The operational benefit of this telemetry information is
   balanced against the operational costs of not recording that an
   voucher was ignored by a client the registrar expected to continue
   joining the domain.

   {
     "version":"1",
     "Status":FALSE /* TRUE=Success, FALSE=Fail"
     "Reason":"Informative human readable message"
     "reason-context": { additional JSON }
   }

   The server SHOULD respond with an HTTP 200 but MAY simply fail with
   an HTTP 404 error.  The client ignores any response.  Within the
   server logs the server SHOULD capture this telemetry information.

   The reason-context attribute is an arbitrary JSON object (literal
   value or hash of values) which provides additional information
   specific to this pledge.  The contents of this field are not subject
   to standardization.

   Additional standard JSON fields in this POST MAY be added, see
   Section 7.3. 8.3.

5.8.  Registrar audit log request

   After receiving the pledge status telemetry Section 5.7, the
   registrar SHOULD request the MASA audit log from the MASA service.

   This is done with an HTTP GET using the operation path value of
   "/.well-known/est/requestauditlog".

   The registrar SHOULD HTTP POST the same registrar voucher-request as
   it did when requesting a voucher (using the same Content-Type).  It
   is posted to the /requestauditlog URI instead.  The "idevid-issuer"
   and "serial-number" informs the MASA which log is requested so the
   appropriate log can be prepared for the response.  Using the same
   media type and message minimizes cryptographic and message operations
   although it results in additional network traffic.  The relying MASA
   implementation MAY leverage internal state to associate this request
   with the original, and by now already validated, voucher-request so
   as to avoid an extra crypto validation.

   A registrar MAY request logs at future times.  If the registrar
   generates a new request then the MASA is forced to perform the
   additional cryptographic operations to verify the new request.

   A MASA that receives a request for a device that does not exist, or
   for which the requesting owner was never an owner returns an HTTP 404
   ("Not found") code.

   Rather than returning the audit log as a response to the POST (with a
   return code 200), the MASA MAY instead return a 201 ("Created")
   RESTful response ([RFC7231] section 7.1) containing a URL to the
   prepared (and easily cachable) audit response.

   In order to avoid enumeration of device audit logs, MASA that return
   URLs SHOULD take care to make the returned URL unguessable.  For
   instance, rather than returning URLs containing a database number
   such as https://example.com/auditlog/1234 or the EUI of the device
   such https://example.com/auditlog/10-00-00-11-22-33, the MASA SHOULD
   return a randomly generated value (a "slug" in web parlance).  The
   value is used to find the relevant database entry.

   A MASA that returns a code 200 MAY also include a Location: header
   for future reference by the registrar.

5.8.1.  MASA audit log response

   A log data file is returned consisting of all log entries associated
   with the the device selected by the IDevID presented in the request.
   The audit log may be truncated of old or repeated values as explained
   below.  The returned data is in JSON format ([RFC7951]), and the
   Content-Type SHOULD be "application/json".  For example:

   {
     "version":"1",
     "events":[
       {
        "date":"<date/time of the entry>",
        "domainID":"<domainID extracted from voucher-request>",
        "nonce":"<any nonce if supplied (or the exact string 'NULL')>"
        "assertion":"<the value from the voucher assertion leaf>"
        "truncated":"<the number of domainID entries truncated>"
       },
       {
        "date":"<date/time of the entry>",
        "domainID":"<anotherDomainID extracted from voucher-request>",
        "nonce":"<any nonce if supplied (or the exact string 'NULL')>"
        "assertion":"<the value from the voucher assertion leaf>"
       }
     ],
     "truncation": {
        "nonced duplicates": "<total number of entries truncated>",
        "nonceless duplicates": "<total number of entries truncated>",
        "arbitrary": "<number of domainID entries removed entirely>"
        }
   }

   Distribution of a large log is less than ideal.  This structure can
   be optimized as follows: Nonced or Nonceless entries for the same
   domainID MAY be truncated from the log leaving only the single most
   recent nonced or nonceless entry for that domainID.  In the case of
   truncation the 'event' truncation value SHOULD contain a count of the
   number of events for this domainID that were truncated.  The log
   SHOULD NOT be further reduced but there could exist operational
   situation where maintaining the full log is not possible.  In such
   situations the log MAY be arbitrarily truncated for length, with the
   number of removed entries indicated as 'arbitrary'.

   If the truncation count exceeds 1024 then the MASA MAY use this value
   without further incrementing it.

   A log where duplicate entries for the same domain have been truncated
   ("nonced duplicates" and/or "nonceless duplicates) could still be
   acceptable for informed decisions.  A log that has had "arbitrary"
   truncations is less acceptable but manufacturer transparency is
   better than hidden truncations.

   This document specifies a simple log format as provided by the MASA
   service to the registrar.  This format could be improved by
   distributed consensus technologies that integrate vouchers with
   technologies such as block-chain or hash trees or optimized logging
   approaches.  Doing so is out of the scope of this document but is an
   anticipated improvement for future work.  As such, the registrar
   client SHOULD anticipate new kinds of responses, and SHOULD provide
   operator controls to indicate how to process unknown responses.

5.8.2.  Registrar audit log verification

   Each time the Manufacturer Authorized Signing Authority (MASA) issues
   a voucher, it places it into the audit log for that device.  The
   details are described in Section 5.8.  The contents of the audit log
   can express a variety of trust levels, and this section explains what
   kind of trust a registrar can derive from the entries.

   While the audit log provides a list of vouchers that were issued by
   the MASA, the vouchers are issued in response to voucher-requests,
   and it is the contents of the voucher-requests which determines how
   meaningful the audit log entries are.

   A registrar SHOULD use the log information to make an informed
   decision regarding the continued bootstrapping of the pledge.  The
   exact policy is out of scope of this document as it depends on the
   security requirements within the registrar domain.  Equipment that is
   purchased pre-owned can be expected to have an extensive history.
   The following dicussion is provided to help explain the value of each
   log element:

   date:  The date field provides the registrar an opportunity to divide
      the log around known events such as the purchase date.  Depending
      on context known to the registrar or administrator evens before/
      after certain dates can have different levels of importance.  For
      example for equipment that is expected to be new, and thus have no
      history, it would be a surprise to find prior entries.

   domainID:  If the log includes an unexpected domainID then the pledge
      could have imprinted on an unexpected domain.  The registrar can
      be expected to use a variety of techniques to define "unexpected"
      ranging from white lists of prior domains to anomoly detection
      (e.g. "this device was previously bound to a different domain than
      any other device deployed").  Log entries can also be compared
      against local history logs in search of discrepancies (e.g. "this
      device was re-deployed some number of times internally but the
      external audit log shows additional re-deployments our internal
      logs are unaware of").

   nonce:  Nonceless entries mean the logged domainID could
      theoretically trigger a reset of the pledge and then take over
      management by using the existing nonceless voucher.

   assertion:  The assertion leaf in the voucher and audit log indicates
      why the MASA issued the voucher.  A "verified" entry means that
      the MASA issued the associated voucher as a result of positive
      verification of ownership but this can still be problematic for
      registrar's that expected only new (not pre-owned) pledges.  A
      "logged" assertion informs the registrar that the prior vouchers
      were issued with minimal verification.  A "proximity" assertion
      assures the registrar that the pledge was truly communicating with
      the prior domain and thus provides assurance that the prior domain
      really has deployed the pledge.

   A relatively simple policy is to white list known (internal or
   external) domainIDs and to require all vouchers to have a nonce and/
   or require that all nonceless vouchers be from a subset (e.g. only
   internal) domainIDs.  A simple action is to revoke any locally issued
   credentials for the pledge in question or to refuse to forward the
   voucher.  A registrar MAY be configured to ignore the history of the
   device but it is RECOMMENDED that this only be configured if hardware
   assisted NEA [RFC5209] is supported.

5.9.  EST Integration for PKI bootstrapping

   The pledge SHOULD follow the BRSKI operations with EST enrollment
   operations including "CA Certificates Request", "CSR Attributes" and
   "Client Certificate Request" or "Server-Side Key Generation", etc.
   This is a relatively seamless integration since BRSKI REST calls
   provide an automated alternative to the manual bootstrapping method
   described in [RFC7030].  As noted above, use of HTTP 1.1 persistent
   connections simplifies the pledge state machine.

   Although EST allows clients to obtain multiple certificates by
   sending multiple CSR requests BRSKI mandates use of the CSR
   Attributes request and mandates that the registrar validate the CSR
   against the expected attributes.  This implies that client requests
   will "look the same" and therefore result in a single logical
   certificate being issued even if the client were to make multiple
   requests.  Registrars MAY contain more complex logic but doing so is
   out-of-scope of this specification.  BRSKI does not signal any
   enhancement or restriction to this capability.

5.9.1.  EST Distribution of CA Certificates

   The pledge SHOULD request the full EST Distribution of CA
   Certificates message.  See RFC7030, section 4.1.

   This ensures that the pledge has the complete set of current CA
   certificates beyond the pinned-domain-cert (see Section 5.6.1 for a
   discussion of the limitations inherent in having a single certificate
   instead of a full CA Certificates response.)  Although these
   limitations are acceptable during initial bootstrapping, they are not
   appropriate for ongoing PKIX end entity certificate validation.

5.9.2.  EST CSR Attributes

   Automated bootstrapping occurs without local administrative
   configuration of the pledge.  In some deployments it is plausible
   that the pledge generates a certificate request containing only
   identity information known to the pledge (essentially the X.509
   IDevID information) and ultimately receives a certificate containing
   domain specific identity information.  Conceptually the CA has
   complete control over all fields issued in the end entity
   certificate.  Realistically this is operationally difficult with the
   current status of PKI certificate authority deployments, where the
   CSR is submitted to the CA via a number of non-standard protocols.
   Even with all standardized protocols used, it could operationally be
   problematic to expect that service specific certificate fields can be
   created by a CA that is likely operated by a group that has no
   insight into different network services/protocols used.  For example,
   the CA could even be outsourced.

   To alleviate these operational difficulties, the pledge MUST request
   the EST "CSR Attributes" from the EST server and the EST server needs
   to be able to reply with the attributes necessary for use of the
   certificate in its intended protocols/services.  This approach allows
   for minimal CA integrations and instead the local infrastructure (EST
   server) informs the pledge of the proper fields to include in the
   generated CSR.  This approach is beneficial to automated boostrapping
   in the widest number of environments.

   If the hardwareModuleName in the X.509 IDevID is populated then it
   SHOULD by default be propagated to the LDevID along with the
   hwSerialNum.  The EST server SHOULD support local policy concerning
   this functionality.

   In networks using the BRSKI enrolled certificate to authenticate the
   ACP (Autonomic Control Plane), the EST attributes MUST include the
   "ACP information" field.  See
   [I-D.ietf-anima-autonomic-control-plane] for more details.

   The registrar MUST also confirm that the resulting CSR is formatted
   as indicated before forwarding the request to a CA.  If the registrar
   is communicating with the CA using a protocol such as full CMC, which
   provides mechanisms to override the CSR attributes, then these
   mechanisms MAY be used even if the client ignores CSR Attribute
   guidance.

5.9.3.  EST Client Certificate Request

   The pledge MUST request a new client certificate.  See RFC7030,
   section 4.2.

5.9.4.  Enrollment Status Telemetry

   For automated bootstrapping of devices, the adminstrative elements
   providing bootstrapping also provide indications to the system
   administrators concerning device lifecycle status.  This might
   include information concerning attempted bootstrapping messages seen
   by the client, MASA provides logs and status of credential
   enrollment.  [RFC7030] assumes an end user and therefore does not
   include a final success indication back to the server.  This is
   insufficient for automated use cases.

   To indicate successful enrollment the client SHOULD re-negotiate the
   EST TLS session using the newly obtained credentials.  This occurs by
   the client initiating a new TLS ClientHello message on the existing
   TLS connection.  The client MAY simply close the old TLS session and
   start a new one.  The server MUST support either model.

   In the case of a FAIL, the Reason string indicates why the most
   recent enrollment failed.  The SubjectKeyIdentifier field MUST be
   included if the enrollment attempt was for a keypair that is locally
   known to the client.  If EST /serverkeygen was used and failed then
   the field is omitted from the status telemetry.

   In the case of a SUCCESS the Reason string is omitted.  The
   SubjectKeyIdentifier is included so that the server can record the
   successful certificate distribution.

   Status media type: application/json

   The client HTTP POSTs the following to the server at the new EST well
   known URI /enrollstatus.

   {
     "version":"1",
     "Status":TRUE /* TRUE=Success, FALSE=Fail"
     "Reason":"Informative human readable message"
     "reason-context": "Additional information"
   }

   The server SHOULD respond with an HTTP 200 but MAY simply fail with
   an HTTP 404 error.

   Within the server logs the server MUST capture if this message was
   received over an TLS session with a matching client certificate.
   This allows for clients that wish to minimize their crypto operations
   to simply POST this response without renegotiating the TLS session -
   at the cost of the server not being able to accurately verify that
   enrollment was truly successful.

5.9.5.  Multiple certificates

   Pledges that require multiple certificates could establish direct EST
   connections to the registrar.

5.9.6.  EST over CoAP

   This document describes extensions to EST for the purposes of
   bootstrapping of remote key infrastructures.  Bootstrapping is
   relevant for CoAP enrollment discussions as well.  The defintion of
   EST and BRSKI over CoAP is not discussed within this document beyond
   ensuring proxy support for CoAP operations.  Instead it is
   anticipated that a definition of CoAP mappings will occur in
   subsequent documents such as [I-D.ietf-ace-coap-est] and that CoAP
   mappings for BRSKI will be discussed either there or in future work.

6.  Clarification of transfer-encoding

   [RFC7030] defines it's endpoints to include a "Content-Transfer-
   Encoding" heading, and the payloads to be [RFC4648] Base64 encoded
   DER.

   When used within BRSKI, the original RFC7030 EST endpoints remain
   Base64 encoded, but the new BRSKI end points which send and receive
   binary artifacts (specifically, ../voucherrequest) are binary.  That
   is, no encoding is used.

   In the BRSKI context, the EST "Content-Transfer-Encoding" header if
   present, SHOULD be ignored.  This header does not need to included.

7.  Reduced security operational modes

   A common requirement of bootstrapping is to support less secure
   operational modes for support specific use cases.  The following
   sections detail specific ways that the pledge, registrar and MASA can
   be configured to run in a less secure mode for the indicated reasons.

   This section is considered non-normative: use suggested methods MUST
   be detailed in specific profiles of BRSKI.  This is the subject for
   future work.

6.1.

7.1.  Trust Model

   This section explains the trust relationships detailed in
   Section 2.4:

   +--------+         +---------+    +------------+     +------------+
   | Pledge |         | Join    |    | Domain     |     |Manufacturer|
   |        |         | Proxy   |    | Registrar  |     | Service    |
   |        |         |         |    |            |     | (Internet) |
   +--------+         +---------+    +------------+     +------------+

   Figure 10

   Pledge:  The pledge could be compromised and providing an attack
      vector for malware.  The entity is trusted to only imprint using
      secure methods described in this document.  Additional endpoint
      assessment techniques are RECOMMENDED but are out-of-scope of this
      document.

   Join Proxy:  Provides proxy functionalities but is not involved in
      security considerations.

   Registrar:  When interacting with a MASA a registrar makes all
      decisions.  For Ownership Audit Vouchers (see [RFC8366]) the
      registrar is provided an opportunity to accept MASA decisions.

   Vendor Service, MASA:  This form of manufacturer service is trusted
      to accurately log all claim attempts and to provide authoritative
      log information to registrars.  The MASA does not know which
      devices are associated with which domains.  These claims could be
      strengthened by using cryptographic log techniques to provide
      append only, cryptographic assured, publicly auditable logs.
      Current text provides only for a trusted manufacturer.

   Vendor Service, Ownership Validation:  This form of manufacturer
      service is trusted to accurately know which device is owned by
      which domain.

6.2.

7.2.  Pledge security reductions

   The pledge can choose to accept vouchers using less secure methods.
   These methods enable offline and emergency (touch based) deployment
   use cases:

   1.  The pledge MUST accept nonceless vouchers.  This allows for a use
       case where the registrar can not connect to the MASA at the
       deployment time.  Logging and validity periods address the
       security considerations of supporting these use cases.

   2.  Many devices already support "trust on first use" for physical
       interfaces such as console ports.  This document does not change
       that reality.  Devices supporting this protocol MUST NOT support
       "trust on first use" on network interfaces.  This is because
       "trust on first use" over network interfaces would undermine the
       logging based security protections provided by this
       specification.

   3.  The pledge MAY have an operational mode where it skips voucher
       validation one time.  For example if a physical button is
       depressed during the bootstrapping operation.  This can be useful
       if the manufacturer service is unavailable.  This behavior SHOULD
       be available via local configuration or physical presence methods
       (such as use of a serial/craft console) to ensure new entities
       can always be deployed even when autonomic methods fail.  This
       allows for unsecured imprint.

   It is RECOMMENDED that "trust on first use" or any method of skipping
   voucher validation (including use of craft serial console) only be
   available if hardware assisted Network Endpoint Assessment [RFC5209]
   is supported.  This recommendation ensures that domain network
   monitoring can detect innappropriate use of offline or emergency
   deployment procedures when voucher-based bootstrapping is not used.

6.3.

7.3.  Registrar security reductions

   A registrar can choose to accept devices using less secure methods.
   These methods are acceptable when low security models are needed, as
   the security decisions are being made by the local administrator, but
   they MUST NOT be the default behavior:

   1.  A registrar MAY choose to accept all devices, or all devices of a
       particular type, at the administrator's discretion.  This could
       occur when informing all registrars of unique identifiers of new
       entities might be operationally difficult.

   2.  A registrar MAY choose to accept devices that claim a unique
       identity without the benefit of authenticating that claimed
       identity.  This could occur when the pledge does not include an
       X.509 IDevID factory installed credential.  New Entities without
       an X.509 IDevID credential MAY form the Section 5.2 request using
       the Section 5.5 format to ensure the pledge's serial number
       information is provided to the registrar (this includes the
       IDevID AuthorityKeyIdentifier value, which would be statically
       configured on the pledge.)  The pledge MAY refuse to provide a
       TLS client certificate (as one is not available.)  The pledge
       SHOULD support HTTP-based or certificate-less TLS authentication
       as described in EST RFC7030 section 3.3.2.  A registrar MUST NOT
       accept unauthenticated New Entities unless it has been configured
       to do so by an administrator that has verified that only expected
       new entities can communicate with a registrar (presumably via a
       physically secured perimeter.)

   3.  A registrar MAY submit a nonceless voucher-requests to the MASA
       service (by not including a nonce in the voucher-request.)  The
       resulting vouchers can then be stored by the registrar until they
       are needed during bootstrapping operations.  This is for use
       cases where the target network is protected by an air gap and
       therefore cannot contact the MASA service during pledge
       deployment.

   4.  A registrar MAY ignore unrecognized nonceless log entries.  This
       could occur when used equipment is purchased with a valid history
       being deployed in air gap networks that required permanent
       vouchers.

   5.  A registrar MAY accept voucher formats of future types that can
       not be parsed by the Registrar.  This reduces the Registrar's
       visibility into the exact voucher contents but does not change
       the protocol operations.

6.4.

7.4.  MASA security reductions

   Lower security modes chosen by the MASA service affect all device
   deployments unless bound to the specific device identities.  In which
   case these modes can be provided as additional features for specific
   customers.  The MASA service can choose to run in less secure modes
   by:

   1.  Not enforcing that a nonce is in the voucher.  This results in
       distribution of a voucher that never expires and in effect makes
       the Domain an always trusted entity to the pledge during any
       subsequent bootstrapping attempts.  That this occurred is
       captured in the log information so that the registrar can make
       appropriate security decisions when a pledge joins the Domain.
       This is useful to support use cases where registrars might not be
       online during actual device deployment.  Because this results in
       a long lived voucher and does not require the proof that the
       device is online, this is only accepted when the registrar is
       authenticated by the MASA and authorized to provide this
       functionality.  The MASA is RECOMMENDED to use this functionality
       only in concert with an enhanced level of ownership tracking
       (out-of-scope.)  If the pledge device is known to have a real-
       time-clock that is set from the factory, use of a voucher
       validity period is RECOMMENDED.

   2.  Not verifying ownership before responding with a voucher.  This
       is expected to be a common operational model because doing so
       relieves the manufacturer providing MASA services from having to
       track ownership during shipping and supply chain and allows for a
       very low overhead MASA service.  A registrar uses the audit log
       information as a defense in depth strategy to ensure that this
       does not occur unexpectedly (for example when purchasing new
       equipment the registrar would throw an error if any audit log
       information is reported.)  The MASA SHOULD verify the 'prior-
       signed-voucher-request' information for pledges that support that
       functionality.  This provides a proof-of-proximity check that
       reduces the need for ownership verification.

7.

8.  IANA Considerations

   This document requires the following IANA actions:

7.1.

8.1.  Well-known EST registration

   This document extends the definitions of "est" (so far defined via
   RFC7030) in the "https://www.iana.org/assignments/well-known-uris/
   well-known-uris.xhtml" registry as follows:

   o  add /.well-known/est/requestvoucher (see Section 5.5 )

   o  add /.well-known/est/requestauditlog (see Section 5.7)

7.2.

8.2.  PKIX Registry

   IANA is requested to register the following:

   This document requests a number for id-mod-MASAURLExtn2016(TBD) from
   the pkix(7) id-mod(0) Registry.

   This document has received an early allocation from the id-pe
   registry (SMI Security for PKIX Certificate Extension) for id-pe-
   masa-url with the value 32, resulting in an OID of
   1.3.6.1.5.5.7.1.32.

7.3.

8.3.  Pledge BRSKI Status Telemetry

   IANA is requested to create a new Registry entitled: "BRSKI
   Parameters", and within that Registry to create a table called:
   "Pledge BRSKI Status Telemetry Attributes".  New items can be added
   using the Specification Required.  The following items are to be in
   the initial registration, with this document (Section 5.7) as the
   reference:

   o  version

   o  Status

   o  Reason

   o  reason-context

7.4.

8.4.  DNS Service Names

   IANA is requested to register the following Service Names:

   Service Name: _brski-proxy
   Transport Protocol(s): tcp
   Assignee: IESG <iesg@ietf.org>.
   Contact: IESG <iesg@ietf.org>
   Description: The Bootstrapping Remote Secure Key
                Infrastructures Proxy
   Reference: [This document]

   Service Name: _brski-registrar
   Transport Protocol(s): tcp
   Assignee: IESG <iesg@ietf.org>.
   Contact: IESG <iesg@ietf.org>
   Description: The Bootstrapping Remote Secure Key
                Infrastructures Registrar
   Reference: [This document]

7.5.

8.5.  MUD File Extension for the MASA

   The IANA is requested to list the name "masa" in the MUD extensions
   registry defined in [I-D.ietf-opsawg-mud].  Its use is documented in
   Appendix C.

8.

9.  Applicability to the Autonomic Control Plane

   This document provides a solution to the requirements for secure
   bootstrap set out in Using an Autonomic Control Plane for Stable
   Connectivity of Network Operations, Administration, and Maintenance
   [RFC8368], A Reference Model for Autonomic Networking
   [I-D.ietf-anima-reference-model] and specifically the An Autonomic
   Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane], section
   3.2 (Secure Bootstrap), and section 6.1 (ACP Domain, Certificate and
   Network).

   The protocol described in this document has appeal in a number of
   other non-ANIMA use cases.  Such uses of the protocol will be
   deploying into other environments with different tradeoffs of
   privacy, security, reliability and autonomy from manufacturers.  As
   such those use cases will need to provide their own applicability
   statements, and will need to address unique privacy and security
   considerations for the environments in which they are used.

   The autonomic control plane that this document provides bootstrap for
   is typically a medium to large Internet Service Provider
   organization, or an equivalent Enterprise that has signficant layer-3
   router connectivity.  (A network consistenting of primarily layer-2
   is not excluded, but the adjacencies that the ACP will create and
   maintain will not reflect the topology until all devices participate
   in the ACP).

   As specified in the ANIMA charter, this work "..focuses on
   professionally-managed networks."  Such a network has an operator and
   can do things like like install, configure and operate the Registrar
   function.  The operator makes purchasing decisions and is aware of
   what manufacturers it expects to see on it's network.

   Such an operator also is capable of performing the traditional (craft
   serial-console) based bootstrap of devices.  The zero-touch mechanism
   presented in this and the ACP document represents a signficiant
   efficiency: in particular it reduces the need to put senior experts
   on airplanes to configure devices in person.  There is a recognition
   as the technology evolves that not every situation may work out, and
   occasionally a human still still have to visit.

   The BRSKI protocol is going into environments where there have
   already been quite a number of vendor proprietary management systems.
   Those are not expected to go away quickly, but rather to leverage the
   secure credentials that are provisioned by BRSKI.  The connectivity
   requirements of said management systems are provided by the ACP.

9.

10.  Privacy Considerations

9.1.

10.1.  MASA audit log

   The MASA audit log includes a hash of the domainID for each Registrar
   a voucher has been issued to.  This information is closely related to
   the actual domain identity, especially when paired with the anti-DDoS
   authentication information the MASA might collect.  This could
   provide sufficient information for the MASA service to build a
   detailed understanding the devices that have been provisioned within
   a domain.

   There are a number of design choices that mitigate this risk.  The
   domain can maintain some privacy since it has not necessarily been
   authenticated and is not authoritatively bound to the supply chain.

   Additionally the domainID captures only the unauthenticated subject
   key identifier of the domain.  A privacy sensitive domain could
   theoretically generate a new domainID for each device being deployed.
   Similarly a privacy sensitive domain would likely purchase devices
   that support proximity assertions from a manufacturer that does not
   require sales channel integrations.  This would result in a
   significant level of privacy while maintaining the security
   characteristics provided by Registrar based audit log inspection.

9.2.

10.2.  What BRSKI-MASA reveals to the manufacturer

   The so-called "call-home" mechanism that occurs as part of the BRSKI-
   MASA connection standardizes what has been deemed by some as a
   sinister mechanism for corporate oversight of individuals.
   ([livingwithIoT] and [IoTstrangeThings] for a small sample).

   As the Autonomic Control Plane (ACP) usage of BRSKI is not targetted
   at individual usage of IoT devices, but rather at the Enterprise and
   ISP creation of networks in a zero-touch fashion, the "call-home"
   represents a different kind of concern.

   It needs to be re-iterated that the BRSKI-MASA mechanism only occurs
   once during the comissioning of the device.  It is well defined, and
   although encrypted with TLS, it could in theory be made auditable as
   the contents are well defined.  This connection does not occur when
   the device powers on or is restarted for normal routines.  It is
   conceivable that a device could be forced to go through a full
   factory reset during an exceptional firmware update situation, after
   which enrollment would have be repeated.

   The BRSKI call-home mechanism is mediated via the owner's Registrar,
   and the information that is transmitted is directly auditable by the
   device owner.  This is in stark constrast to many "call-home"
   protocols where the device autonomously calls home and uses an
   undocumented protocol.

   While the contents of the signed part of the pledge voucher request
   can not be changed, they are not encrypted at the registrar.  The
   ability to audit the messages by the owner of the network prevents
   exfiltration of data by a nefarious pledge.  The contents of an
   unsigned voucher request are, however, completely changeable by the
   Registrar.  Both are, to re-iterate, encrypted by TLS while in
   transit.

   The BRSKI-MASA exchange reveals the following information to the
   manufacturer:

   o  the identity of the device being enrolled (down to the serial-
      number!).

   o  an identity of the domain owner in the form of the domain trust
      anchor.  However, this is not a global PKI anchored name within
      the WebPKI, so this identity could be pseudonymous.  If there is
      sales channel integration, then the MASA will have authenticated
      the domain owner, either via pinned certificate, or perhaps
      another HTTP authentication method, as per Section 5.5.3.

   o  the time the device is activated,

   o  the IP address of the domain Owner's Registrar.  For ISPs and
      Enterprises, the IP address provides very clear geolocation of the
      owner.  No amount of IP address privacy extensions ([RFC4941]) can
      do anything about this, as a simple whois lookup likely identifies
      the ISP or Enterprise from the upper bits anyway.  A passive
      attacker who observes the connection definitely may conclude that
      the given enterprise/ISP is a customer of the particular equipment
      vendor.  The precise model that is being enrolled will remain
      private.

   The above situation is to be distinguished from a residential/
   individual person who registers a device from a manufacturer: that an
   enterprise/ISP purchases routing products is hardly worth mentioning.
   Deviations would, however, be notable.

   The situation is not improved by the enterprise/ISP using
   anonymization services such as ToR [Dingledine2004], as a TLS 1.2
   connection will reveal the ClientCertificate used, clearly
   identifying the enterprise/ISP involved.  TLS 1.3 is better in this
   regard, but an active attacker can still discover the parties
   involved by performing a Man-In-The-Middle-Attack on the first
   attempt (breaking/killing it with a TCP RST), and then letting
   subsequent connection pass through.

   A manufacturer could attempt to mix the BRSKI-MASA traffic in with
   general traffic their site by hosting the MASA behind the same (set)
   of load balancers that the companies normal marketing site is hosted
   behind.  This makes lots of sense from a straight capacity planning
   point of view as the same set of services (and the same set of
   Distributed Denial of Service mitigations) may be used.
   Unfortunately, as the BRSKI-MASA connections include TLS
   ClientCertificate exchanges, this may easily be observed in TLS 1.2,
   and a traffic analysis may reveal it even in TLS 1.3.  This does not
   make such a plan irrelevant.  There may be other organizational
   reasons to keep the marketing site (which is often subject to
   frequent redesigs, outsourcing, etc.) seperate from the MASA, which
   may need to operate reliably for decades.

9.3.

10.3.  Manufacturers and Used or Stolen Equipment

   As explained above, the manufacturer receives information each time
   that a device which is in factory-default mode does a zero-touch
   bootstrap, and attempts to enroll into a domain owner's registrar.

   The manufacturer is therefore in a position to decline to issue a
   voucher if it detects that the new owner is not the same as the
   previous owner.

   1.  This can be seen as a feature if the equipment is believed to
       have been stolen.  If the legitimate owner notifies the
       manufacturer of the theft, then when the new owner brings the
       device up, if they use the zero-touch mechanism, the new
       (illegitimate) owner reveals their location and identity.

   2.  In the case of Used equipment, the initial owner could inform the
       manufacturer of the sale, or the manufacturer may just permit
       resales unless told otherwise.  In which case, the transfer of
       ownership simply occurs.

   3.  A manufacturer could however decide not to issue a new voucher in
       response to a transfer of ownership.  This is essentially the
       same as the stolen case, with the manufacturer having decided
       that the sale was not legitimate.

   4.  There is a fourth case, if the manufacturer is providing
       protection against stolen devices.  The manufacturer then has a
       responsability to protect the legitimate owner against fraudulent
       claims that the the equipment was stolen.  Such a claim would
       cause the manufacturer to refuse to issue a new voucher.  Should
       the device go through a deep factory reset (for instance,
       replacement of a damaged main board component, the device would
       not bootstrap.

   5.  Finally, there is a fifth case: the manufacturer has decided to
       end-of-line the device, or the owner has not paid a yearly
       support amount, and the manufacturer refuses to issue new
       vouchers at that point.  This last case is not new to the
       industry: many license systems are already deployed that have
       significantly worse effect.

   This section has outlined five situations in which a manufacturer
   could use the voucher system to enforce what are clearly license
   terms.  A manufacturer that attempted to enforce license terms via
   vouchers would find it rather ineffective as the terms would only be
   enforced when the device is enrolled, and this is not (to repeat), a
   daily or even monthly occurrance.

9.4.

10.4.  Manufacturers and Grey market equipment

   Manufacturers of devices often sell different products into different
   regional markets.  Which product is available in which market can be
   driven by price differentials, support issues (some markets may
   require manuals and tech-support to be done in the local language),
   government export regulation (such as whether strong crypto is
   permitted to be exported, or permitted to be used in a particular
   market).  When an domain owner obtains a device from a different
   market (they can be new) and transfers it to a different location,
   this is called a Grey Market.

   A manufacturer could decide not to issue a voucher to an enterprise/
   ISP based upon their location.  There are a number of ways which this
   could be determined: from the geolocation of the registrar, from
   sales channel knowledge about the customer, and what products are
   (un-)available in that market.  If the device has a GPS the
   coordinates of the device could even be placed into an extension of
   the voucher.

   The above actions are not illegal, and not new.  Many manufacturers
   have shipped crypto-weak (exportable) versions of firmware as the
   default on equipment for decades.  The first task of an enterprise/
   ISP has always been to login to a manufacturer system, show one's
   "entitlement" (country informatin, proof that support payments have
   been made), and receive either a new updated firmware, or a license
   key that will activate the correct firmware.

   BRSKI permits the above process to automated (in an autonomic
   fashion), and therefore perhaps encourages this kind of
   differentiation by reducing the cost of doing it.

   An issue that manufacturers will need to deal with in the above
   automated process is when a device is shipped to one country with one
   set of rules (or laws or entitlements), but the domain registry is in
   another one.  Which rules apply is something will have to be worked
   out: the manufacturer could come to believe they are dealing with
   Grey market equipment, when it is simply dealing with a global
   enterprise.

9.5.

10.5.  Some mitigations for meddling by manufacturers

   The most obvious mitigation is not to buy the product.  Pick
   manufacturers that are up-front about their policies, who do not
   change them gratutiously.

   A manufacturer could provide a mechanism to manage the trust anchors
   and built-in certificates (IDevID) as an extension.  This is a
   substantial amount of work, and may be an area for future
   standardization work.

   Replacement of the voucher validation anchors (usually pointing to
   the original manufacturer's MASA) with those of the new owner permits
   the new owner to issue vouchers to subsequent owners.  This would be
   done by having the selling (old) owner to run a MASA.

   In order to automatically find the new MASA, the mechanism describe
   in this document is to look for the MASA URL extension in the IDevID.
   A new owner could override this in their Registrar, or the
   manufacturer could provide a mechanism to update or replace the
   IDevID prior to sale.

   Once the voucher trust anchor and the IDevID is replaced, then the
   device will no longer trust the manufacturer in any way.  When a new
   owner performs a bootstrap, the device will point to a MASA that has
   been chosen, and will validate vouchers from this new entity.

   The BRSKI protocol depends upon a trust anchor on the device and an
   identity on the device.  Management of these these entities
   facilitiates a few new operatonal modes without making any changes to
   the BRSKI protocol.  Those modes include: offline modes where the
   domain owner operates an internal MASA for all devices, resell modes
   where the first domain owner becomes the MASA for the next (resold-
   to) domain owner, and services where an aggregator acquires a large
   variety of devices, and then acts as a pseudonymized MASA for a
   variety of devices from a variety of manufacturers.

   Some manufacturers may wish to consider replacement of the IDevID as
   an indication that the device's warantee is terminated.  For others,
   the privacy requiments of some deployments might consider this a
   standard operating practice.

   As discussed at the end of Section 5.8.1, new work could be done to
   use a distributed consensus technology for the audit log.  This would
   permit the audit log to continue to be useful, even when there is a
   chain of MASA due to changes of ownership.

10.

11.  Security Considerations

   This document details a protocol for bootstrapping that balances
   operational concerns against security concerns.  As detailed in the
   introduction, and touched on again in Section 6, 7, the protocol allows
   for reduced security modes.  These attempt to deliver additional
   control to the local administrator and owner in cases where less
   security provides operational benefits.  This section goes into more
   detail about a variety of specific considerations.

   To facilitate logging and administrative oversight, in addition to
   triggering Registration verification of MASA logs, the pledge reports
   on voucher parsing status to the registrar.  In the case of a
   failure, this information is informative to a potentially malicious
   registrar.  This is mandated anyway because of the operational
   benefits of an informed administrator in cases where the failure is
   indicative of a problem.  The registrar is RECOMMENDED to verify MASA
   logs if voucher status telemetry is not received.

   To facilitate truely limited clients EST RFC7030 section 3.3.2
   requirements that the client MUST support a client authentication
   model have been reduced in Section 6 7 to a statement that the
   registrar "MAY" choose to accept devices that fail cryptographic
   authentication.  This reflects current (poor) practices in shipping
   devices without a cryptographic identity that are NOT RECOMMENDED.

   During the provisional period of the connection the pledge MUST treat
   all HTTP header and content data as untrusted data.  HTTP libraries
   are regularly exposed to non-secured HTTP traffic: mature libraries
   should not have any problems.

   Pledges might chose to engage in protocol operations with multiple
   discovered registrars in parallel.  As noted above they will only do
   so with distinct nonce values, but the end result could be multiple
   vouchers issued from the MASA if all registrars attempt to claim the
   device.  This is not a failure and the pledge choses whichever
   voucher to accept based on internal logic.  The registrars verifying
   log information will see multiple entries and take this into account
   for their analytics purposes.

10.1.

11.1.  DoS against MASA

   There are uses cases where the MASA could be unavailable or
   uncooperative to the Registrar.  They include active DoS attacks,
   planned and unplanned network partitions, changes to MASA policy, or
   other instances where MASA policy rejects a claim.  These introduce
   an operational risk to the Registrar owner in that MASA behavior
   might limit the ability to bootstrap a pledge device.  For example
   this might be an issue during disaster recovery.  This risk can be
   mitigated by Registrars that request and maintain long term copies of
   "nonceless" vouchers.  In that way they are guaranteed to be able to
   bootstrap their devices.

   The issuance of nonceless vouchers themselves creates a security
   concern.  If the Registrar of a previous domain can intercept
   protocol communications then it can use a previously issued nonceless
   voucher to establish management control of a pledge device even after
   having sold it.  This risk is mitigated by recording the issuance of
   such vouchers in the MASA audit log that is verified by the
   subsequent Registrar and by Pledges only bootstrapping when in a
   factory default state.  This reflects a balance between enabling MASA
   independence during future bootstrapping and the security of
   bootstrapping itself.  Registrar control over requesting and auditing
   nonceless vouchers allows device owners to choose an appropriate
   balance.

   The MASA is exposed to DoS attacks wherein attackers claim an
   unbounded number of devices.  Ensuring a registrar is representative
   of a valid manufacturer customer, even without validating ownership
   of specific pledge devices, helps to mitigate this.  Pledge
   signatures on the pledge voucher-request, as forwarded by the
   registrar in the prior-signed-voucher-request field of the registrar
   voucher-request, significantly reduce this risk by ensuring the MASA
   can confirm proximity between the pledge and the registrar making the
   request.  This mechanism is optional to allow for constrained
   devices.  Supply chain integration ("know your customer") is an
   additional step that MASA providers and device vendors can explore.

10.2.

11.2.  Freshness in Voucher-Requests

   A concern has been raised that the pledge voucher-request should
   contain some content (a nonce) provided by the registrar and/or MASA
   in order for those actors to verify that the pledge voucher-request
   is fresh.

   There are a number of operational problems with getting a nonce from
   the MASA to the pledge.  It is somewhat easier to collect a random
   value from the registrar, but as the registrar is not yet vouched
   for, such a registrar nonce has little value.  There are privacy and
   logistical challenges to addressing these operational issues, so if
   such a thing were to be considered, it would have to provide some
   clear value.  This section examines the impacts of not having a fresh
   pledge voucher-request.

   Because the registrar authenticates the pledge, a full Man-in-the-
   Middle attack is not possible, despite the provisional TLS
   authentication by the pledge (see Section 5.)  Instead we examine the
   case of a fake registrar (Rm) that communicates with the pledge in
   parallel or in close time proximity with the intended registrar.
   (This scenario is intentionally supported as described in
   Section 4.1.)

   The fake registrar (Rm) can obtain a voucher signed by the MASA
   either directly or through arbitrary intermediaries.  Assuming that
   the MASA accepts the registrar voucher-request (either because Rm is
   collaborating with a legitimate registrar according to supply chain
   information, or because the MASA is in audit-log only mode), then a
   voucher linking the pledge to the registrar Rm is issued.

   Such a voucher, when passed back to the pledge, would link the pledge
   to registrar Rm, and would permit the pledge to end the provisional
   state.  It now trusts Rm and, if it has any security vulnerabilities
   leveragable by an Rm with full administrative control, can be assumed
   to be a threat against the intended registrar.

   This flow is mitigated by the intended registrar verifying the audit
   logs available from the MASA as described in Section 5.8.  Rm might
   chose to collect a voucher-request but wait until after the intended
   registrar completes the authorization process before submitting it.
   This pledge voucher-request would be 'stale' in that it has a nonce
   that no longer matches the internal state of the pledge.  In order to
   successfully use any resulting voucher the Rm would need to remove
   the stale nonce or anticipate the pledge's future nonce state.
   Reducing the possibility of this is why the pledge is mandated to
   generate a strong random or pseudo-random number nonce.

   Additionally, in order to successfully use the resulting voucher the
   Rm would have to attack the pledge and return it to a bootstrapping
   enabled state.  This would require wiping the pledge of current
   configuration and triggering a re-bootstrapping of the pledge.  This
   is no more likely than simply taking control of the pledge directly
   but if this is a consideration the target network is RECOMMENDED to
   take the following steps:

   o  Ongoing network monitoring for unexpected bootstrapping attempts
      by pledges.

   o  Retreival and examination of MASA log information upon the
      occurance of any such unexpected events.  Rm will be listed in the
      logs along with nonce information for analysis.

10.3.

11.3.  Trusting manufacturers

   The BRSKI extensions to EST permit a new pledge to be completely
   configured with domain specific trust anchors.  The link from built-
   in manufacturer-provided trust anchors to domain-specific trust
   anchors is mediated by the signed voucher artifact.

   If the manufacturer's IDevID signing key is not properly validated,
   then there is a risk that the network will accept a pledge that
   should not be a member of the network.  As the address of the
   manufacturer's MASA is provided in the IDevID using the extension
   from Section 2.3, the malicious pledge will have no problem
   collaborating with it's MASA to produce a completely valid voucher.

   BRSKI does not, however, fundamentally change the trust model from
   domain owner to manufacturer.  Assuming that the pledge used its
   IDevID with RFC7030 EST and BRSKI, the domain (registrar) still needs
   to trust the manufacturer.

   Establishing this trust between domain and manufacturer is outside
   the scope of BRSKI.  There are a number of mechanisms that can
   adopted including:

   o  Manually configuring each manufacturer's trust anchor.

   o  A Trust-On-First-Use (TOFU) mechanism.  A human would be queried
      upon seeing a manufacturer's trust anchor for the first time, and
      then the trust anchor would be installed to the trusted store.
      There are risks with this; even if the key to name is validated
      using something like the WebPKI, there remains the possibility
      that the name is a look alike: e.g, dem0.example. vs demO.example.

   o  scanning the trust anchor from a QR code that came with the
      packaging (this is really a manual TOFU mechanism)

   o  some sales integration process where trust anchors are provided as
      part of the sales process, probably included in a digital packing
      "slip", or a sales invoice.

   o  consortium membership, where all manufacturers of a particular
      device category (e.g, a light bulb, or a cable-modem) are signed
      by an certificate authority specifically for this.  This is done
      by CableLabs today.  It is used for authentication and
      authorization as part of TR-79: [docsisroot] and [TR069].

   The existing WebPKI provides a reasonable anchor between manufacturer
   name and public key.  It authenticates the key.  It does not provide
   a reasonable authorization for the manufacturer, so it is not
   directly useable on it's own.

10.4.

11.4.  Manufacturer Maintainance of trust anchors

   BRSKI depends upon the manufacturer building in trust anchors to the
   pledge device.  The voucher artifact which is signed by the MASA will
   be validated by the pledge using that anchor.  This implies that the
   manufacturer needs to maintain access to a signing key that the
   pledge can validate.

   The manufacturer will need to maintain the ability to make signatures
   that can be validated for the lifetime that the device could be
   onboarded.  Whether this onboarding lifetime is less than the device
   lifetime depends upon how the device is used.  An inventory of
   devices kept in a warehouse as spares might not be onboarded for many
   decades.

   There are good cryptographic hygiene reasons why a manufacturer would
   not want to maintain access to a private key for many decades.  A
   manufacturer in that situation can leverage a long-term certificate
   authority anchor, built-in to the pledge, and then a certificate
   chain may be incorporated using the normal CMS certificate set.  This
   may increase the size of the voucher artifacts, but that is not a
   significant issues in non-constrained environements.

   There are a few other operational variations that manufacturers could
   consider.  For instance, there is no reason that every device need
   have the same set of trust anchors pre-installed.  Devices built in
   different factories, or on different days, or any other consideration
   could have different trust anchors built in, and the record of which
   batch the device is in would be recorded in the asset database.  The
   manufacturer would then know which anchor to sign an artifact
   against.

   Aside from the concern about long-term access to private keys, a
   major limiting factor for the shelf-life of many devices will be the
   age of the cryptographic algorithms included.  A device produced in
   2019 will have hardware and software capable of validating algorithms
   common in 2019, and will have no defense against attacks (both
   quantum and von-neuman brute force attacks) which have not yet been
   invented.  This concern is orthogonal to the concern about access to
   private keys, but this concern likely dominates and limits the
   lifespan of a device in a warehouse.  If any update to firmware to
   support new cryptographic mechanism were possible (while the device
   was in a warehouse), updates to trust anchors would also be done at
   the same time.

11.

12.  Acknowledgements

   We would like to thank the various reviewers for their input, in
   particular William Atwood, Brian Carpenter, Toerless Eckert, Fuyu
   Eleven, Eliot Lear, Sergey Kasatkin, Anoop Kumar, Markus Stenberg,
   Peter van der Stok, and Thomas Werner

   Significant reviews were done by Jari Arko, Christian Huitema and
   Russ Housley.

12.

13.  References

12.1.

13.1.  Normative References

   [I-D.ietf-anima-autonomic-control-plane]
              Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
              Control Plane (ACP)", draft-ietf-anima-autonomic-control-
              plane-19 (work in progress), March 2019.

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-15 (work in progress), July 2017.

   [IDevID]   "IEEE 802.1AR Secure Device Identifier", December 2009,
              <http://standards.ieee.org/findstds/
              standard/802.1AR-2009.html>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
              <https://www.rfc-editor.org/info/rfc3748>.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              DOI 10.17487/RFC3927, May 2005,
              <https://www.rfc-editor.org/info/rfc3927>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <https://www.rfc-editor.org/info/rfc4086>.

   [RFC4519]  Sciberras, A., Ed., "Lightweight Directory Access Protocol
              (LDAP): Schema for User Applications", RFC 4519,
              DOI 10.17487/RFC4519, June 2006,
              <https://www.rfc-editor.org/info/rfc4519>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <https://www.rfc-editor.org/info/rfc4648>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/info/rfc4862>.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
              <https://www.rfc-editor.org/info/rfc4941>.

   [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/info/rfc5246>.

   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,
              <https://www.rfc-editor.org/info/rfc5272>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5386]  Williams, N. and M. Richardson, "Better-Than-Nothing
              Security: An Unauthenticated Mode of IPsec", RFC 5386,
              DOI 10.17487/RFC5386, November 2008,
              <https://www.rfc-editor.org/info/rfc5386>.

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

   [RFC5660]  Williams, N., "IPsec Channels: Connection Latching",
              RFC 5660, DOI 10.17487/RFC5660, October 2009,
              <https://www.rfc-editor.org/info/rfc5660>.

   [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/info/rfc6125>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <https://www.rfc-editor.org/info/rfc6762>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/rfc6763>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.

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

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,
              <https://www.rfc-editor.org/info/rfc8366>.

   [RFC8368]  Eckert, T., Ed. and M. Behringer, "Using an Autonomic
              Control Plane for Stable Connectivity of Network
              Operations, Administration, and Maintenance (OAM)",
              RFC 8368, DOI 10.17487/RFC8368, May 2018,
              <https://www.rfc-editor.org/info/rfc8368>.

12.2.

13.2.  Informative References

   [Dingledine2004]
              Dingledine, R., Mathewson, N., and P. Syverson, "Tor: the
              second-generation onion router", 2004,
              <https://spec.torproject.org/tor-spec>.

   [docsisroot]
              "CableLabs Digital Certificate Issuance Service", February
              2018, <https://www.cablelabs.com/resources/
              digital-certificate-issuance-service/>.

   [I-D.ietf-ace-coap-est]
              Stok, P., Kampanakis, P., Richardson, M., and S. Raza,
              "EST over secure CoAP (EST-coaps)", draft-ietf-ace-coap-
              est-12 (work in progress), June 2019.

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", draft-
              ietf-anima-constrained-voucher-03 (work in progress),
              March 2019.

   [I-D.ietf-anima-reference-model]
              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              and J. Nobre, "A Reference Model for Autonomic
              Networking", draft-ietf-anima-reference-model-10 (work in
              progress), November 2018.

   [I-D.ietf-anima-stable-connectivity]
              Eckert, T. and M. Behringer, "Using Autonomic Control
              Plane for Stable Connectivity of Network OAM", draft-ietf-
              anima-stable-connectivity-10 (work in progress), February
              2018.

   [I-D.ietf-cbor-cddl]
              Birkholz, H., Vigano, C., and C. Bormann, "Concise data
              definition language (CDDL): a notational convention to
              express CBOR and JSON data structures", draft-ietf-cbor-
              cddl-08 (work in progress), March 2019.

   [I-D.ietf-netconf-zerotouch]
              Watsen, K., Abrahamsson, M., and I. Farrer, "Secure Zero
              Touch Provisioning (SZTP)", draft-ietf-netconf-
              zerotouch-29 (work in progress), January 2019.

   [I-D.ietf-opsawg-mud]
              Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
              Description Specification", draft-ietf-opsawg-mud-25 (work
              in progress), June 2018.

   [I-D.richardson-anima-state-for-joinrouter]
              Richardson, M., "Considerations for stateful vs stateless
              join router in ANIMA bootstrap", draft-richardson-anima-
              state-for-joinrouter-02 (work in progress), January 2018.

   [imprinting]
              "Wikipedia article: Imprinting", July 2015,
              <https://en.wikipedia.org/wiki/Imprinting_(psychology)>.

   [IoTstrangeThings]
              "IoT of toys stranger than fiction: Cybersecurity and data
              privacy update (accessed 2018-12-02)", March 2017,
              <https://www.welivesecurity.com/2017/03/03/
              internet-of-things-security-privacy-iot-update/>.

   [livingwithIoT]
              "What is it actually like to live in a house filled with
              IoT devices? (accessed 2018-12-02)", February 2018,
              <https://www.siliconrepublic.com/machines/
              iot-smart-devices-reality>.

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
              December 1998, <https://www.rfc-editor.org/info/rfc2473>.

   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations",
              RFC 2663, DOI 10.17487/RFC2663, August 1999,
              <https://www.rfc-editor.org/info/rfc2663>.

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              DOI 10.17487/RFC5785, April 2010,
              <https://www.rfc-editor.org/info/rfc5785>.

   [RFC6960]  Santesson, S., Myers, M., Ankney, R., Malpani, A.,
              Galperin, S., and C. Adams, "X.509 Internet Public Key
              Infrastructure Online Certificate Status Protocol - OCSP",
              RFC 6960, DOI 10.17487/RFC6960, June 2013,
              <https://www.rfc-editor.org/info/rfc6960>.

   [RFC6961]  Pettersen, Y., "The Transport Layer Security (TLS)
              Multiple Certificate Status Request Extension", RFC 6961,
              DOI 10.17487/RFC6961, June 2013,
              <https://www.rfc-editor.org/info/rfc6961>.

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014,
              <https://www.rfc-editor.org/info/rfc7217>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/info/rfc7228>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <https://www.rfc-editor.org/info/rfc7258>.

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

   [RFC7575]  Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking: Definitions and Design Goals", RFC 7575,
              DOI 10.17487/RFC7575, June 2015,
              <https://www.rfc-editor.org/info/rfc7575>.

   [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/info/rfc8340>.

   [slowloris]
              "Slowloris (computer security)", February 2019,
              <https://en.wikipedia.org/wiki/
              Slowloris_(computer_security)/>.

   [Stajano99theresurrecting]
              Stajano, F. and R. Anderson, "The resurrecting duckling:
              security issues for ad-hoc wireless networks", 1999,
              <https://www.cl.cam.ac.uk/~fms27/
              papers/1999-StajanoAnd-duckling.pdf>.

   [TR069]    "TR-69: CPE WAN Management Protocol", February 2018,
              <https://www.broadband-forum.org/standards-and-software/
              technical-specifications/tr-069-files-tools>.

Appendix A.  IPv4 and non-ANI operations

   The secification of BRSKI in Section 4 intentionally only covers the
   mechanisms for an IPv6 pledge using Link-Local addresses.  This
   section describes non-normative extensions that can be used in other
   environments.

A.1.  IPv4 Link Local addresses

   Instead of an IPv6 link-local address, an IPv4 address may be
   generated using [RFC3927] Dynamic Configuration of IPv4 Link-Local
   Addresses.

   In the case that an IPv4 Link-Local address is formed, then the
   bootstrap process would continue as in the IPv6 case by looking for a
   (circuit) proxy.

A.2.  Use of DHCPv4

   The Plege MAY obtain an IP address via DHCP [RFC2131].  The DHCP
   provided parameters for the Domain Name System can be used to perform
   DNS operations if all local discovery attempts fail.

Appendix B.  mDNS / DNSSD proxy discovery options

   Pledge discovery of the proxy (Section 4.1) MAY be performed with
   DNS-based Service Discovery [RFC6763] over Multicast DNS [RFC6762] to
   discover the proxy at "_brski-proxy._tcp.local.".

   Proxy discovery of the registrar (Section 4.3) MAY be performed with
   DNS-based Service Discovery over Multicast DNS to discover registrars
   by searching for the service "_brski-registrar._tcp.local.".

   To prevent unaccceptable levels of network traffic, when using mDNS,
   the congestion avoidance mechanisms specified in [RFC6762] section 7
   MUST be followed.  The pledge SHOULD listen for an unsolicited
   broadcast response as described in [RFC6762].  This allows devices to
   avoid announcing their presence via mDNS broadcasts and instead
   silently join a network by watching for periodic unsolicited
   broadcast responses.

   Discovery of registrar MAY also be performed with DNS-based service
   discovery by searching for the service "_brski-
   registrar._tcp.example.com".  In this case the domain "example.com"
   is discovered as described in [RFC6763] section 11 (Appendix A.2
   suggests the use of DHCP parameters).

   If no local proxy or registrar service is located using the GRASP
   mechanisms or the above mentioned DNS-based Service Discovery methods
   the pledge MAY contact a well known manufacturer provided
   bootstrapping server by performing a DNS lookup using a well known
   URI such as "brski-registrar.manufacturer.example.com".  The details
   of the URI are manufacturer specific.  Manufacturers that leverage
   this method on the pledge are responsible for providing the registrar
   service.  Also see Section 2.7.

   The current DNS services returned during each query are maintained
   until bootstrapping is completed.  If bootstrapping fails and the
   pledge returns to the Discovery state, it picks up where it left off
   and continues attempting bootstrapping.  For example, if the first
   Multicast DNS _bootstrapks._tcp.local response doesn't work then the
   second and third responses are tried.  If these fail the pledge moves
   on to normal DNS-based Service Discovery.

Appendix C.  MUD Extension

   The following extension augments the MUD model to include a single
   node, as described in [I-D.ietf-opsawg-mud] section 3.6, using the
   following sample module that has the following tree structure:

   module: ietf-mud-brski-masa
   augment /ietf-mud:mud:
   +--rw masa-server?   inet:uri

   The model is defined as follows:

   <CODE BEGINS> file "ietf-mud-extension@2018-02-14.yang"
   module ietf-mud-brski-masa {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-mud-brski-masa";
     prefix ietf-mud-brski-masa;
     import ietf-mud {
       prefix ietf-mud;
     }
     import ietf-inet-types {
       prefix inet;
     }

     organization
       "IETF ANIMA (Autonomic Networking Integrated Model and
       Approach) Working Group";
       contact
       "WG Web: http://tools.ietf.org/wg/anima/
       WG List: anima@ietf.org
       ";
     description
       "BRSKI extension to a MUD file to indicate the
       MASA URL.";

     revision 2018-02-14 {
       description
       "Initial revision.";
       reference
       "RFC XXXX: Manufacturer Usage Description
       Specification";
     }

     augment "/ietf-mud:mud" {
       description
       "BRSKI extension to a MUD file to indicate the
       MASA URL.";
       leaf masa-server {
         type inet:uri;
         description
         "This value is the URI of the MASA server";
       }
     }
   }
   <CODE ENDS>

   The MUD extensions string "masa" is defined, and MUST be included in
   the extensions array of the mud container of a MUD file when this
   extension is used.

Appendix D.  Example Vouchers

   Three entities are involved in a voucher: the MASA issues (signs) it,
   the registrar's public key is mentioned in the voucher, and the
   pledge validates it.  In order to provide reproduceable examples the
   public and private keys for an example MASA and registrar are first
   listed.

D.1.  Keys involved

   The Manufacturer has a Certificate Authority that signs the pledge's
   IDevID.  In addition the Manufacturer's signing authority (the MASA)
   signs the vouchers, and that certificate must distributed to the
   devices at manufacturing time so that vouchers can be validated.

D.1.1.  MASA key pair for voucher signatures

   This private key signs vouchers:

   -----BEGIN EC PRIVATE KEY-----
   MIGkAgEBBDAgiRoYqKoEcfOfvRvmZ5P5Azn58tuI7nSnIy7OgFnCeiNo+BmbgMho
   r6lcU60gwVagBwYFK4EEACKhZANiAATZAH3Rb2FvIJOnts+vXuWW35ofyNbCHzjA
   zOi2kWZFE1ByurKImNcNMFGirGnRXIXGqWCfw5ICgJ8CuM3vV5ty9bf7KUlOkejz
   Tvv+5PV++elkP9HQ83vqTAws2WwWTxI=
   -----END EC PRIVATE KEY-----

   This public key validates vouchers:

   -----BEGIN CERTIFICATE-----
   MIIBzzCCAVagAwIBAgIBATAKBggqhkjOPQQDAjBNMRIwEAYKCZImiZPyLGQBGRYC
   Y2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xHDAaBgNVBAMME1Vuc3RydW5n
   IEhpZ2h3YXkgQ0EwHhcNMTcwMzI2MTYxOTQwWhcNMTkwMzI2MTYxOTQwWjBHMRIw
   EAYKCZImiZPyLGQBGRYCY2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xFjAU
   BgNVBAMMDVVuc3RydW5nIE1BU0EwdjAQBgcqhkjOPQIBBgUrgQQAIgNiAATZAH3R
   b2FvIJOnts+vXuWW35ofyNbCHzjAzOi2kWZFE1ByurKImNcNMFGirGnRXIXGqWCf
   w5ICgJ8CuM3vV5ty9bf7KUlOkejzTvv+5PV++elkP9HQ83vqTAws2WwWTxKjEDAO
   MAwGA1UdEwEB/wQCMAAwCgYIKoZIzj0EAwIDZwAwZAIwGb0oyM0doP6t3/LSPL5O
   DuatEwMYh7WGO+IYTHC8K7EyHBOmCYReKT2+GhV/CLWzAjBNy6UMJTt1tsxJsJqd
   MPUIFj+4wZg1AOIb/JoA6M7r33pwLQTrHRxEzVMGfWOkYUw=
   -----END CERTIFICATE-----

D.1.2.  Manufacturer key pair for IDevID signatures

   This private key signs IDevID certificates:

   -----BEGIN EC PRIVATE KEY-----
   MIGkAgEBBDAgiRoYqKoEcfOfvRvmZ5P5Azn58tuI7nSnIy7OgFnCeiNo+BmbgMho
   r6lcU60gwVagBwYFK4EEACKhZANiAATZAH3Rb2FvIJOnts+vXuWW35ofyNbCHzjA
   zOi2kWZFE1ByurKImNcNMFGirGnRXIXGqWCfw5ICgJ8CuM3vV5ty9bf7KUlOkejz
   Tvv+5PV++elkP9HQ83vqTAws2WwWTxI=
   -----END EC PRIVATE KEY-----

   This public key validates IDevID certificates:

   -----BEGIN CERTIFICATE-----
   MIIBzzCCAVagAwIBAgIBATAKBggqhkjOPQQDAjBNMRIwEAYKCZImiZPyLGQBGRYC
   Y2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xHDAaBgNVBAMME1Vuc3RydW5n
   IEhpZ2h3YXkgQ0EwHhcNMTcwMzI2MTYxOTQwWhcNMTkwMzI2MTYxOTQwWjBHMRIw
   EAYKCZImiZPyLGQBGRYCY2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xFjAU
   BgNVBAMMDVVuc3RydW5nIE1BU0EwdjAQBgcqhkjOPQIBBgUrgQQAIgNiAATZAH3R
   b2FvIJOnts+vXuWW35ofyNbCHzjAzOi2kWZFE1ByurKImNcNMFGirGnRXIXGqWCf
   w5ICgJ8CuM3vV5ty9bf7KUlOkejzTvv+5PV++elkP9HQ83vqTAws2WwWTxKjEDAO
   MAwGA1UdEwEB/wQCMAAwCgYIKoZIzj0EAwIDZwAwZAIwGb0oyM0doP6t3/LSPL5O
   DuatEwMYh7WGO+IYTHC8K7EyHBOmCYReKT2+GhV/CLWzAjBNy6UMJTt1tsxJsJqd
   MPUIFj+4wZg1AOIb/JoA6M7r33pwLQTrHRxEzVMGfWOkYUw=
   -----END CERTIFICATE-----

D.1.3.  Registrar key pair

   The registrar key (or chain) is the representative of the domain
   owner.  This key signs registrar voucher-requests:

   -----BEGIN EC PRIVATE KEY-----
   MHcCAQEEIF+obiToYYYeMifPsZvrjWJ0yFsCJwIFhpokmT/TULmXoAoGCCqGSM49
   AwEHoUQDQgAENWQOzcNMUjP0NrtfeBc0DJLWfeMGgCFdIv6FUz4DifM1ujMBec/g
   6W/P6boTmyTGdFOh/8HwKUerL5bpneK8sg==
   -----END EC PRIVATE KEY-----

   The public key is indicated in a pledge voucher-request to show
   proximity.

   -----BEGIN CERTIFICATE-----
   MIIBrjCCATOgAwIBAgIBAzAKBggqhkjOPQQDAzBOMRIwEAYKCZImiZPyLGQBGRYC
   Y2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xHTAbBgNVBAMMFFVuc3RydW5n
   IEZvdW50YWluIENBMB4XDTE3MDkwNTAxMTI0NVoXDTE5MDkwNTAxMTI0NVowQzES
   MBAGCgmSJomT8ixkARkWAmNhMRkwFwYKCZImiZPyLGQBGRYJc2FuZGVsbWFuMRIw
   EAYDVQQDDAlsb2NhbGhvc3QwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAAQ1ZA7N
   w0xSM/Q2u194FzQMktZ94waAIV0i/oVTPgOJ8zW6MwF5z+Dpb8/puhObJMZ0U6H/
   wfApR6svlumd4ryyow0wCzAJBgNVHRMEAjAAMAoGCCqGSM49BAMDA2kAMGYCMQC3
   /iTQJ3evYYcgbXhbmzrp64t3QC6qjIeY2jkDx062nuNifVKtyaara3F30AIkKSEC
   MQDi29efbTLbdtDk3tecY/rD7V77XaJ6nYCmdDCR54TrSFNLgxvt1lyFM+0fYpYR
   c3o=
   -----END CERTIFICATE-----
   The registrar public certificate as decoded by openssl's x509
   utility.  Note that the registrar certificate is marked with the
   cmcRA extension.

   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 3 (0x3)
           Signature Algorithm: ecdsa-with-SHA384
           Issuer: DC=ca, DC=sandelman, CN=Unstrung Fountain DC = ca, DC = sandelman, CN = Unstrung Fount
   ain CA
           Validity
               Not Before: Sep  5 01:12:45 2017 GMT
               Not After : Sep  5 01:12:45 2019 GMT
           Subject: DC=ca, DC=sandelman, CN=localhost DC = ca, DC = sandelman, CN = localhost
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
                   pub:
                       04:35:64:0e:cd:c3:4c:52:33:f4:36:bb:5f:7
   8:17:
                       34:0c:92:d6:7d:e3:06:80:21:5d:22:fe:85:5
   3:3e:
                       03:89:f3:35:ba:33:01:79:cf:e0:e9:6f:cf:e
   9:ba:
                       13:9b:24:c6:74:53:a1:ff:c1:f0:29:47:ab:2
   f:96:
                       e9:9d:e2:bc:b2
                   ASN1 OID: prime256v1
                   NIST CURVE: P-256
           X509v3 extensions:
               X509v3 Basic Constraints:
                   CA:FALSE
       Signature Algorithm: ecdsa-with-SHA384
            30:66:02:31:00:b7:fe:24:d0:27:77:af:61:87:20:6d:78:
   5b:
            9b:3a:e9:eb:8b:77:40:2e:aa:8c:87:98:da:39:03:c7:4e:
   b6:
            9e:e3:62:7d:52:ad:c9:a6:ab:6b:71:77:d0:02:24:29:21:
   02:
            31:00:e2:db:d7:9f:6d:32:db:76:d0:e4:de:d7:9c:63:fa:
   c3:
            ed:5e:fb:5d:a2:7a:9d:80:a6:74:30:91:e7:84:eb:48:53:
   4b:
            83:1b:ed:d6:5c:85:33:ed:1f:62:96:11:73:7a

D.1.4.  Pledge key pair

   The pledge has an IDevID key pair built in at manufacturing time:

   -----BEGIN EC PRIVATE KEY-----
   MHcCAQEEIBgR6SV+uEvWfl5zCQWZxWjYbMhXPyNqdHJ3KPh11mm4oAoGCCqGSM49
   AwEHoUQDQgAEWi/jqPpRJ0JgWghZRgeZlLKutbXVjmnHb+1AYaEF/YQjE2g5FZV8
   KjiR/bkEl+l8M4onIC7KHaXKKkuag9S6Tw==
   -----END EC PRIVATE KEY-----

   The public key is used by the registrar to find the MASA.  The MASA
   URL is in an extension described in Section 2.3.

   -----BEGIN CERTIFICATE-----
   MIICBDCCAYugAwIBAgIECe20qTAKBggqhkjOPQQDAjBNMRIwEAYKCZImiZPyLGQB
   GRYCY2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xHDAaBgNVBAMME1Vuc3Ry
   dW5nIEhpZ2h3YXkgQ0EwIBcNMTkwNDI0MDIxNjU4WhgPMjk5OTEyMzEwMDAwMDBa
   MBwxGjAYBgNVBAUMETAwLWQwLWU1LTAyLTAwLTJkMFkwEwYHKoZIzj0CAQYIKoZI
   zj0DAQcDQgAEWi/jqPpRJ0JgWghZRgeZlLKutbXVjmnHb+1AYaEF/YQjE2g5FZV8
   KjiR/bkEl+l8M4onIC7KHaXKKkuag9S6T6OBhzCBhDAdBgNVHQ4EFgQUj8KYdUoE
   OvJ0kcOIbjEWwgWdDYkwCQYDVR0TBAIwADArBgNVHREEJDAioCAGCSsGAQQBgu5S
   AaATDBEwMC1EMC1FNS0wMi0wMC0yRDArBgkrBgEEAYLuUgIEHgwcbWFzYS5ob25l
   eWR1a2VzLnNhbmRlbG1hbi5jYTAKBggqhkjOPQQDAgNnADBkAjAmvMjmNgjypDhc
   fynMV3kMuIpSKrYzRWr4g3PtTwXDsAe0oitTTj4QtU1bajhOfTkCMGMNbsW2Q41F
   z9t6PDVdtOKabBbAP1RVoFTlDQuO9nmLzb5kU+cUqCtPRFZBUXP3kg==
   -----END CERTIFICATE-----

   The pledge public certificate as decoded by openssl's x509 utility so
   that the extensions can be seen.  There is a second Custom Extension
   is included to provided to contain the EUI48/EUI64 that the pledge
   will configure as it's layer-2 address (this is non-normative).

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 166573225 (0x9edb4a9)
        Signature Algorithm: ecdsa-with-SHA256
        Issuer: DC = ca, DC = sandelman, CN = Unstrung Highway CA
        Validity
            Not Before: Apr 24 02:16:58 2019 GMT
            Not After : Dec 31 00:00:00 2999 GMT
        Subject: serialNumber = 00-d0-e5-02-00-2d
        Subject Public Key Info:
            Public Key Algorithm: id-ecPublicKey
                Public-Key: (256 bit)
                pub:
                    04:5a:2f:e3:a8:fa:51:27:42:60:5a:08:59:46:07:
                    99:94:b2:ae:b5:b5:d5:8e:69:c7:6f:ed:40:61:a1:
                    05:fd:84:23:13:68:39:15:95:7c:2a:38:91:fd:b9:
                    04:97:e9:7c:33:8a:27:20:2e:ca:1d:a5:ca:2a:4b:
                    9a:83:d4:ba:4f
                ASN1 OID: prime256v1
                NIST CURVE: P-256
        X509v3 extensions:
            X509v3 Subject Key Identifier:
                8F:C2:98:75:4A:04:3A:F2:74:91:C3:88:6E:31:16:C2:05:9D:0D:89
            X509v3 Basic Constraints:
                CA:FALSE
            X509v3 Subject Alternative Name:
                othername:<unsupported>
            1.3.6.1.4.1.46930.2:
                ..masa.honeydukes.sandelman.ca
    Signature Algorithm: ecdsa-with-SHA256
         30:64:02:30:26:bc:c8:e6:36:08:f2:a4:38:5c:7f:29:cc:57:
         79:0c:b8:8a:52:2a:b6:33:45:6a:f8:83:73:ed:4f:05:c3:b0:
         07:b4:a2:2b:53:4e:3e:10:b5:4d:5b:6a:38:4e:7d:39:02:30:
         63:0d:6e:c5:b6:43:8d:45:cf:db:7a:3c:35:5d:b4:e2:9a:6c:
         16:c0:3f:54:55:a0:54:e5:0d:0b:8e:f6:79:8b:cd:be:64:53:
         e7:14:a8:2b:4f:44:56:41:51:73:f7:92

D.2.  Example process

   RFC-EDITOR: these examples will need to be replaced with CMS versions
   once IANA has assigned the eContentType in [RFC8366].

D.2.1.  Pledge to Registrar

   As described in Section 5.2, the pledge will sign a pledge voucher-
   request containing the registrar's public key in the proximity-
   registrar-cert field.  The base64 has been wrapped at 60 characters
   for presentation reasons.

   -----BEGIN CMS-----
   MIIGtQYJKoZIhvcNAQcCoIIGpjCCBqICAQExDTALBglghkgBZQMEAgEwggNRBgkq
   hkiG9w0BBwGgggNCBIIDPnsiaWV0Zi12b3VjaGVyLXJlcXVlc3Q6dm91Y2hlciI6
   eyJhc3NlcnRpb24iOiJwcm94aW1pdHkiLCJjcmVhdGVkLW9uIjoiMjAxOS0wNS0x
   NVQxNzoyNTo1NS42NDQtMDQ6MDAiLCJzZXJpYWwtbnVtYmVyIjoiMDAtZDAtZTUt
   MDItMDAtMmQiLCJub25jZSI6IlZPVUZULVd3ckV2ME51QVFFSG9WN1EiLCJwcm94
   aW1pdHktcmVnaXN0cmFyLWNlcnQiOiJNSUlCMFRDQ0FWYWdBd0lCQWdJQkFqQUtC
   Z2dxaGtqT1BRUURBekJ4TVJJd0VBWUtDWkltaVpQeUxHUUJHUllDWTJFeEdUQVhC
   Z29Ka2lhSmsvSXNaQUVaRmdsellXNWtaV3h0WVc0eFFEQStCZ05WQkFNTU55TThV
   M2x6ZEdWdFZtRnlhV0ZpYkdVNk1IZ3dNREF3TURBd05HWTVNVEZoTUQ0Z1ZXNXpk
   SEoxYm1jZ1JtOTFiblJoYVc0Z1EwRXdIaGNOTVRjeE1UQTNNak0wTlRJNFdoY05N
   VGt4TVRBM01qTTBOVEk0V2pCRE1SSXdFQVlLQ1pJbWlaUHlMR1FCR1JZQ1kyRXhH
   VEFYQmdvSmtpYUprL0lzWkFFWkZnbHpZVzVrWld4dFlXNHhFakFRQmdOVkJBTU1D
   V3h2WTJGc2FHOXpkREJaTUJNR0J5cUdTTTQ5QWdFR0NDcUdTTTQ5QXdFSEEwSUFC
   SlpsVUhJMHVwL2wzZVpmOXZDQmIrbElub0VNRWdjN1JvK1haQ3RqQUkwQ0QxZkpm
   SlIvaEl5eURtSFd5WWlORmJSQ0g5ZnlhcmZremdYNHAwelRpenFqRFRBTE1Ba0dB
   MVVkRXdRQ01BQXdDZ1lJS29aSXpqMEVBd01EYVFBd1pnSXhBTFFNTnVyZjh0djUw
   bFJPRDVEUVhIRU9KSk5XM1FWMmc5UUVkRFNrMk1ZK0FvU3JCU21HU05qaDRvbEVP
   aEV1TGdJeEFKNG5XZk53K0JqYlptS2lJaVVFY1R3SE1oR1ZYYU1IWS9GN24zOXd3
   S2NCQlNPbmROUHFDcE9FTGw2YnEzQ1pxUT09In19oIICCDCCAgQwggGLoAMCAQIC
   BAnttKkwCgYIKoZIzj0EAwIwTTESMBAGCgmSJomT8ixkARkWAmNhMRkwFwYKCZIm
   iZPyLGQBGRYJc2FuZGVsbWFuMRwwGgYDVQQDDBNVbnN0cnVuZyBIaWdod2F5IENB
   MCAXDTE5MDQyNDAyMTY1OFoYDzI5OTkxMjMxMDAwMDAwWjAcMRowGAYDVQQFDBEw
   MC1kMC1lNS0wMi0wMC0yZDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABFov46j6
   USdCYFoIWUYHmZSyrrW11Y5px2/tQGGhBf2EIxNoORWVfCo4kf25BJfpfDOKJyAu
   yh2lyipLmoPUuk+jgYcwgYQwHQYDVR0OBBYEFI/CmHVKBDrydJHDiG4xFsIFnQ2J
   MAkGA1UdEwQCMAAwKwYDVR0RBCQwIqAgBgkrBgEEAYLuUgGgEwwRMDAtRDAtRTUt
   MDItMDAtMkQwKwYJKwYBBAGC7lICBB4MHG1hc2EuaG9uZXlkdWtlcy5zYW5kZWxt
   YW4uY2EwCgYIKoZIzj0EAwIDZwAwZAIwJrzI5jYI8qQ4XH8pzFd5DLiKUiq2M0Vq
   +INz7U8Fw7AHtKIrU04+ELVNW2o4Tn05AjBjDW7FtkONRc/bejw1XbTimmwWwD9U
   VaBU5Q0LjvZ5i82+ZFPnFKgrT0RWQVFz95IxggErMIIBJwIBATBVME0xEjAQBgoJ
   kiaJk/IsZAEZFgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRlbG1hbjEcMBoGA1UE
   AwwTVW5zdHJ1bmcgSGlnaHdheSBDQQIECe20qTALBglghkgBZQMEAgGgaTAYBgkq
   hkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xOTA1MTUyMTI1
   NTVaMC8GCSqGSIb3DQEJBDEiBCAQN2lP7aqwyhmj9qUHt6Qk/SbOTOPXFOwn1wv2
   5YGYgDAKBggqhkjOPQQDAgRHMEUCIEYQhHToU0rrhPyQv2fR0TwWePTx2Z1DEhR4
   tTl/Dr/ZAiEA47u9+bIz/p6nFJ+wctKHER+ycUzYQF56h9odMo+Ilkc=
   -----END CMS-----

   file: examples/vr_00-D0-E5-02-00-2D.pkcs

   The ASN1 decoding of the artifact:

    0:d=0  hl=4 l=1717 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData

   15:d=1  hl=4 l=1702 cons: cont [ 0 ]
   19:d=2  hl=4 l=1698 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l= 849 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l= 834 cons: cont [ 0 ]
   60:d=5  hl=4 l= 830 prim: OCTET STRING      :{"ietf-voucher-request:v
  894:d=3  hl=4 l= 520 cons: cont [ 0 ]
  898:d=4  hl=4 l= 516 cons: SEQUENCE
  902:d=5  hl=4 l= 395 cons: SEQUENCE
  906:d=6  hl=2 l=   3 cons: cont [ 0 ]
  908:d=7  hl=2 l=   1 prim: INTEGER           :02
  911:d=6  hl=2 l=   4 prim: INTEGER           :09EDB4A9
  917:d=6  hl=2 l=  10 cons: SEQUENCE
  919:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
  929:d=6  hl=2 l=  77 cons: SEQUENCE
  931:d=7  hl=2 l=  18 cons: SET
  933:d=8  hl=2 l=  16 cons: SEQUENCE
  935:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  947:d=9  hl=2 l=   2 prim: IA5STRING         :ca
  951:d=7  hl=2 l=  25 cons: SET
  953:d=8  hl=2 l=  23 cons: SEQUENCE
  955:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  967:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
  978:d=7  hl=2 l=  28 cons: SET
  980:d=8  hl=2 l=  26 cons: SEQUENCE
  982:d=9  hl=2 l=   3 prim: OBJECT            :commonName
  987:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
 1008:d=6  hl=2 l=  32 cons: SEQUENCE
 1010:d=7  hl=2 l=  13 prim: UTCTIME           :190424021658Z
 1025:d=7  hl=2 l=  15 prim: GENERALIZEDTIME   :29991231000000Z
 1042:d=6  hl=2 l=  28 cons: SEQUENCE
 1044:d=7  hl=2 l=  26 cons: SET
 1046:d=8  hl=2 l=  24 cons: SEQUENCE
 1048:d=9  hl=2 l=   3 prim: OBJECT            :serialNumber
 1053:d=9  hl=2 l=  17 prim: UTF8STRING        :00-d0-e5-02-00-2d
 1072:d=6  hl=2 l=  89 cons: SEQUENCE
 1074:d=7  hl=2 l=  19 cons: SEQUENCE
 1076:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 1085:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 1095:d=7  hl=2 l=  66 prim: BIT STRING
 1163:d=6  hl=3 l= 135 cons: cont [ 3 ]
 1166:d=7  hl=3 l= 132 cons: SEQUENCE
 1169:d=8  hl=2 l=  29 cons: SEQUENCE
 1171:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Ident
 1176:d=9  hl=2 l=  22 prim: OCTET STRING      [HEX DUMP]:04148FC298754A
 1200:d=8  hl=2 l=   9 cons: SEQUENCE
 1202:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 1207:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 1211:d=8  hl=2 l=  43 cons: SEQUENCE
 1213:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Alternati
 1218:d=9  hl=2 l=  36 prim: OCTET STRING      [HEX DUMP]:3022A02006092B
 1256:d=8  hl=2 l=  43 cons: SEQUENCE
 1258:d=9  hl=2 l=   9 prim: OBJECT            :1.3.6.1.4.1.46930.2
 1269:d=9  hl=2 l=  30 prim: OCTET STRING      [HEX DUMP]:0C1C6D6173612E
 1301:d=5  hl=2 l=  10 cons: SEQUENCE
 1303:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1313:d=5  hl=2 l= 103 prim: BIT STRING
 1418:d=3  hl=4 l= 299 cons: SET
 1422:d=4  hl=4 l= 295 cons: SEQUENCE
 1426:d=5  hl=2 l=   1 prim: INTEGER           :01
 1429:d=5  hl=2 l=  85 cons: SEQUENCE
 1431:d=6  hl=2 l=  77 cons: SEQUENCE
 1433:d=7  hl=2 l=  18 cons: SET
 1435:d=8  hl=2 l=  16 cons: SEQUENCE
 1437:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1449:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 1453:d=7  hl=2 l=  25 cons: SET
 1455:d=8  hl=2 l=  23 cons: SEQUENCE
 1457:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1469:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 1480:d=7  hl=2 l=  28 cons: SET
 1482:d=8  hl=2 l=  26 cons: SEQUENCE
 1484:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1489:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
 1510:d=6  hl=2 l=   4 prim: INTEGER           :09EDB4A9
 1516:d=5  hl=2 l=  11 cons: SEQUENCE
 1518:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 1529:d=5  hl=2 l= 105 cons: cont [ 0 ]
 1531:d=6  hl=2 l=  24 cons: SEQUENCE
 1533:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 1544:d=7  hl=2 l=  11 cons: SET
 1546:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 1557:d=6  hl=2 l=  28 cons: SEQUENCE
 1559:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 1570:d=7  hl=2 l=  15 cons: SET
 1572:d=8  hl=2 l=  13 prim: UTCTIME           :190515212555Z
 1587:d=6  hl=2 l=  47 cons: SEQUENCE
 1589:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 1600:d=7  hl=2 l=  34 cons: SET
 1602:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:1037694FEDAAB0
 1636:d=5  hl=2 l=  10 cons: SEQUENCE
 1638:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1648:d=5  hl=2 l=  71 prim: OCTET STRING      [HEX DUMP]:30450220461084

   The JSON contained in the voucher request:

{"ietf-voucher-request:voucher":{"assertion":"proximity","created-on":"2019-05-15T17:25:55.644-04:00","serial-number":"00-d0-e5-02-00-2d","nonce":"VOUFT-WwrEv0NuAQEHoV7Q","proximity-registrar-cert":"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"}}

D.2.2.  Registrar to MASA

   As described in Section 5.5 the registrar will sign a registrar
   voucher-request, and will include pledge's voucher request in the
   prior-signed-voucher-request.

   -----BEGIN CMS-----
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   hkiG9w0BBwGgggnFBIIJwXsiaWV0Zi12b3VjaGVyLXJlcXVlc3Q6dm91Y2hlciI6
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   RXpRMXB4VVQwOUluMTlvSUlDQ0RDQ0FnUXdnZ0dMb0FNQ0FRSUNCQW50dEtrd0Nn
   WUlLb1pJemowRUF3SXdUVEVTTUJBR0NnbVNKb21UOGl4a0FSa1dBbU5oTVJrd0Z3
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   R1Gkdt3S8L/1yo8wAX/4wl/T9SADRIuL8gdstKNjMGEwDwYDVR0TAQH/BAUwAwEB
   /zAOBgNVHQ8BAf8EBAMCAQYwHQYDVR0OBBYEFLml9ssR4QekSSynCMZ8ELyHs3Qm
   MB8GA1UdIwQYMBaAFLml9ssR4QekSSynCMZ8ELyHs3QmMAoGCCqGSM49BAMCA2gA
   MGUCMAviLdbfd6AZdsOxNgf7D15WFmGC1JkHeEbT/0w4UXz6q/48S71/IMbSXRWH
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   OjB4MDAwMDAwMDRmOTExYTA+IFVuc3RydW5nIEZvdW50YWluIENBAgECMAsGCWCG
   SAFlAwQCAaBpMBgGCSqGSIb3DQEJAzELBgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkF
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   zxHXLzJ5eusWplzHKqZyxNpzaR8CIQC3UtMu0QsXoUpYL016iTsbd7Eedi8IfnwQ
   akExfhh0ew==
   -----END CMS-----

   file: examples/parboiled_vr_00_D0-E5-02-00-2D.pkcs

   The ASN1 decoding of the artifact:

    0:d=0  hl=4 l=3987 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=3972 cons: cont [ 0 ]
   19:d=2  hl=4 l=3968 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l=2516 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l=2501 cons: cont [ 0 ]
   60:d=5  hl=4 l=2497 prim: OCTET STRING      :{"ietf-voucher-request:v
 2561:d=3  hl=4 l=1090 cons: cont [ 0 ]
 2565:d=4  hl=4 l= 465 cons: SEQUENCE
 2569:d=5  hl=4 l= 342 cons: SEQUENCE
 2573:d=6  hl=2 l=   3 cons: cont [ 0 ]
 2575:d=7  hl=2 l=   1 prim: INTEGER           :02
 2578:d=6  hl=2 l=   1 prim: INTEGER           :02
 2581:d=6  hl=2 l=  10 cons: SEQUENCE
 2583:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA384
 2593:d=6  hl=2 l= 113 cons: SEQUENCE
 2595:d=7  hl=2 l=  18 cons: SET
 2597:d=8  hl=2 l=  16 cons: SEQUENCE
 2599:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2611:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 2615:d=7  hl=2 l=  25 cons: SET
 2617:d=8  hl=2 l=  23 cons: SEQUENCE
 2619:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2631:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 2642:d=7  hl=2 l=  64 cons: SET
 2644:d=8  hl=2 l=  62 cons: SEQUENCE
 2646:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 2651:d=9  hl=2 l=  55 prim: UTF8STRING        :#<SystemVariable:0x00000
 2708:d=6  hl=2 l=  30 cons: SEQUENCE
 2710:d=7  hl=2 l=  13 prim: UTCTIME           :171107234528Z
 2725:d=7  hl=2 l=  13 prim: UTCTIME           :191107234528Z
 2740:d=6  hl=2 l=  67 cons: SEQUENCE
 2742:d=7  hl=2 l=  18 cons: SET
 2744:d=8  hl=2 l=  16 cons: SEQUENCE
 2746:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2758:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 2762:d=7  hl=2 l=  25 cons: SET
 2764:d=8  hl=2 l=  23 cons: SEQUENCE
 2766:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2778:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 2789:d=7  hl=2 l=  18 cons: SET
 2791:d=8  hl=2 l=  16 cons: SEQUENCE
 2793:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 2798:d=9  hl=2 l=   9 prim: UTF8STRING        :localhost
 2809:d=6  hl=2 l=  89 cons: SEQUENCE
 2811:d=7  hl=2 l=  19 cons: SEQUENCE
 2813:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 2822:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 2832:d=7  hl=2 l=  66 prim: BIT STRING
 2900:d=6  hl=2 l=  13 cons: cont [ 3 ]
 2902:d=7  hl=2 l=  11 cons: SEQUENCE
 2904:d=8  hl=2 l=   9 cons: SEQUENCE
 2906:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 2911:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 2915:d=5  hl=2 l=  10 cons: SEQUENCE
 2917:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA384
 2927:d=5  hl=2 l= 105 prim: BIT STRING
 3034:d=4  hl=4 l= 617 cons: SEQUENCE
 3038:d=5  hl=4 l= 495 cons: SEQUENCE
 3042:d=6  hl=2 l=   3 cons: cont [ 0 ]
 3044:d=7  hl=2 l=   1 prim: INTEGER           :02
 3047:d=6  hl=2 l=   1 prim: INTEGER           :03
 3050:d=6  hl=2 l=  10 cons: SEQUENCE
 3052:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3062:d=6  hl=2 l= 109 cons: SEQUENCE
 3064:d=7  hl=2 l=  18 cons: SET
 3066:d=8  hl=2 l=  16 cons: SEQUENCE
 3068:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3080:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3084:d=7  hl=2 l=  25 cons: SET
 3086:d=8  hl=2 l=  23 cons: SEQUENCE
 3088:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3100:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3111:d=7  hl=2 l=  60 cons: SET
 3113:d=8  hl=2 l=  58 cons: SEQUENCE
 3115:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3120:d=9  hl=2 l=  51 prim: UTF8STRING        :fountain-test.example.co
 3173:d=6  hl=2 l=  30 cons: SEQUENCE
 3175:d=7  hl=2 l=  13 prim: UTCTIME           :190113225444Z
 3190:d=7  hl=2 l=  13 prim: UTCTIME           :210112225444Z
 3205:d=6  hl=2 l= 109 cons: SEQUENCE
 3207:d=7  hl=2 l=  18 cons: SET
 3209:d=8  hl=2 l=  16 cons: SEQUENCE
 3211:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3223:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3227:d=7  hl=2 l=  25 cons: SET
 3229:d=8  hl=2 l=  23 cons: SEQUENCE
 3231:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3243:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3254:d=7  hl=2 l=  60 cons: SET
 3256:d=8  hl=2 l=  58 cons: SEQUENCE
 3258:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3263:d=9  hl=2 l=  51 prim: UTF8STRING        :fountain-test.example.co
 3316:d=6  hl=2 l= 118 cons: SEQUENCE
 3318:d=7  hl=2 l=  16 cons: SEQUENCE
 3320:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 3329:d=8  hl=2 l=   5 prim: OBJECT            :secp384r1
 3336:d=7  hl=2 l=  98 prim: BIT STRING
 3436:d=6  hl=2 l=  99 cons: cont [ 3 ]
 3438:d=7  hl=2 l=  97 cons: SEQUENCE
 3440:d=8  hl=2 l=  15 cons: SEQUENCE
 3442:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 3447:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 3450:d=9  hl=2 l=   5 prim: OCTET STRING      [HEX DUMP]:30030101FF
 3457:d=8  hl=2 l=  14 cons: SEQUENCE
 3459:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Key Usage
 3464:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 3467:d=9  hl=2 l=   4 prim: OCTET STRING      [HEX DUMP]:03020106
 3473:d=8  hl=2 l=  29 cons: SEQUENCE
 3475:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Ident
 3480:d=9  hl=2 l=  22 prim: OCTET STRING      [HEX DUMP]:0414B9A5F6CB11
 3504:d=8  hl=2 l=  31 cons: SEQUENCE
 3506:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Authority Key Ide
 3511:d=9  hl=2 l=  24 prim: OCTET STRING      [HEX DUMP]:30168014B9A5F6
 3537:d=5  hl=2 l=  10 cons: SEQUENCE
 3539:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3549:d=5  hl=2 l= 104 prim: BIT STRING
 3655:d=3  hl=4 l= 332 cons: SET
 3659:d=4  hl=4 l= 328 cons: SEQUENCE
 3663:d=5  hl=2 l=   1 prim: INTEGER           :01
 3666:d=5  hl=2 l= 118 cons: SEQUENCE
 3668:d=6  hl=2 l= 113 cons: SEQUENCE
 3670:d=7  hl=2 l=  18 cons: SET
 3672:d=8  hl=2 l=  16 cons: SEQUENCE
 3674:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3686:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3690:d=7  hl=2 l=  25 cons: SET
 3692:d=8  hl=2 l=  23 cons: SEQUENCE
 3694:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3706:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3717:d=7  hl=2 l=  64 cons: SET
 3719:d=8  hl=2 l=  62 cons: SEQUENCE
 3721:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3726:d=9  hl=2 l=  55 prim: UTF8STRING        :#<SystemVariable:0x00000
 3783:d=6  hl=2 l=   1 prim: INTEGER           :02
 3786:d=5  hl=2 l=  11 cons: SEQUENCE
 3788:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 3799:d=5  hl=2 l= 105 cons: cont [ 0 ]
 3801:d=6  hl=2 l=  24 cons: SEQUENCE
 3803:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 3814:d=7  hl=2 l=  11 cons: SET
 3816:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 3827:d=6  hl=2 l=  28 cons: SEQUENCE
 3829:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 3840:d=7  hl=2 l=  15 cons: SET
 3842:d=8  hl=2 l=  13 prim: UTCTIME           :190515212555Z
 3857:d=6  hl=2 l=  47 cons: SEQUENCE
 3859:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 3870:d=7  hl=2 l=  34 cons: SET
 3872:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:50508CC996CD93
 3906:d=5  hl=2 l=  10 cons: SEQUENCE
 3908:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3918:d=5  hl=2 l=  71 prim: OCTET STRING      [HEX DUMP]:3045022006D85B

D.2.3.  MASA to Registrar

   The MASA will return a voucher to the registrar, to be relayed to the
   pledge.

   -----BEGIN CMS-----
   MIIGsgYJKoZIhvcNAQcCoIIGozCCBp8CAQExDTALBglghkgBZQMEAgEwggNABgkq
   hkiG9w0BBwGgggMxBIIDLXsiaWV0Zi12b3VjaGVyOnZvdWNoZXIiOnsiYXNzZXJ0
   aW9uIjoibG9nZ2VkIiwiY3JlYXRlZC1vbiI6IjIwMTktMDUtMTZUMDI6NTE6NDIu
   Njk3KzAwOjAwIiwic2VyaWFsLW51bWJlciI6IjAwLWQwLWU1LTAyLTAwLTJkIiwi
   bm9uY2UiOiJHWmUtT2pvZXJwS0VNNFNNN1N6UzlnIiwicGlubmVkLWRvbWFpbi1j
   ZXJ0IjoiTUlJQjBUQ0NBVmFnQXdJQkFnSUJBakFLQmdncWhrak9QUVFEQXpCeE1S
   SXdFQVlLQ1pJbWlaUHlMR1FCR1JZQ1kyRXhHVEFYQmdvSmtpYUprL0lzWkFFWkZn
   bHpZVzVrWld4dFlXNHhRREErQmdOVkJBTU1OeU04VTNsemRHVnRWbUZ5YVdGaWJH
   VTZNSGd3TURBd01EQXdOR1k1TVRGaE1ENGdWVzV6ZEhKMWJtY2dSbTkxYm5SaGFX
   NGdRMEV3SGhjTk1UY3hNVEEzTWpNME5USTRXaGNOTVRreE1UQTNNak0wTlRJNFdq
   QkRNUkl3RUFZS0NaSW1pWlB5TEdRQkdSWUNZMkV4R1RBWEJnb0praWFKay9Jc1pB
   RVpGZ2x6WVc1a1pXeHRZVzR4RWpBUUJnTlZCQU1NQ1d4dlkyRnNhRzl6ZERCWk1C
   TUdCeXFHU000OUFnRUdDQ3FHU000OUF3RUhBMElBQkpabFVISTB1cC9sM2VaZjl2
   Q0JiK2xJbm9FTUVnYzdSbytYWkN0akFJMENEMWZKZkpSL2hJeXlEbUhXeVlpTkZi
   UkNIOWZ5YXJma3pnWDRwMHpUaXpxakRUQUxNQWtHQTFVZEV3UUNNQUF3Q2dZSUtv
   Wkl6ajBFQXdNRGFRQXdaZ0l4QUxRTU51cmY4dHY1MGxST0Q1RFFYSEVPSkpOVzNR
   VjJnOVFFZERTazJNWStBb1NyQlNtR1NOamg0b2xFT2hFdUxnSXhBSjRuV2ZOdytC
   amJabUtpSWlVRWNUd0hNaEdWWGFNSFkvRjduMzl3d0tjQkJTT25kTlBxQ3BPRUxs
   NmJxM0NacVE9PSJ9faCCAfUwggHxMIIBeKADAgECAgQjzIkTMAoGCCqGSM49BAMC
   ME0xEjAQBgoJkiaJk/IsZAEZFgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRlbG1h
   bjEcMBoGA1UEAwwTVW5zdHJ1bmcgSGlnaHdheSBDQTAeFw0xOTA0MjMyMzIxMDda
   Fw0xOTA1MjQwOTIxMDdaMGYxDzANBgNVBAYTBkNhbmFkYTESMBAGA1UECgwJU2Fu
   ZGVsbWFuMRMwEQYDVQQLDApob25leWR1a2VzMSowKAYDVQQDDCFtYXNhLmhvbmV5
   ZHVrZXMuc2FuZGVsbWFuLmNhIE1BU0EwdjAQBgcqhkjOPQIBBgUrgQQAIgNiAAQ1
   /2UdVp8zVmgADoBNql7LcPlJsEaaVAogYEqABikNOkoTO3oPjIQfNBxtGfRFzBXx
   gihzkTH58r8SW1L/Mej8AFqhB4SZyyjmWURdzD71Ju0M+tRritWf7T+QGaE+fcWj
   EDAOMAwGA1UdEwEB/wQCMAAwCgYIKoZIzj0EAwIDZwAwZAIwOMlNOMNYEZo4yLW4
   iRltDL8uirmjMdtVmmVYzqYHSindjP0a3pXQkQZ5LLARoSRWAjBTxsnv6ya5HpZI
   IWcspDPZGlOSDPm7nuRJSDkgWqevxLI4+9nmIhsfMBsDvz1DJhAxggFMMIIBSAIB
   ATBVME0xEjAQBgoJkiaJk/IsZAEZFgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRl
   bG1hbjEcMBoGA1UEAwwTVW5zdHJ1bmcgSGlnaHdheSBDQQIEI8yJEzALBglghkgB
   ZQMEAgGgaTAYBgkqhkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEP
   Fw0xOTA1MTYwMjUxNDJaMC8GCSqGSIb3DQEJBDEiBCCYRh4i21QjEjEk8leRLSVA
   x/EVY5g1bM40QM21oR4c2DAKBggqhkjOPQQDAgRoMGYCMQCYYOiSbIlED4nAN0iL
   e4S8ixWAZ9SXpGv77bB/G4fTTVTN35mnAeYBfeNfhC6/kOECMQDqlkCmwQJQDdEL
   asj1ISinJ/FnZjjgOMz9MXOmGNGIfw9v2VBb9mVyhsOSMcqlVig=
   -----END CMS-----

   file: examples/voucher_00-D0-E5-02-00-2D.pkcs

   The ASN1 decoding of the artifact:

    0:d=0  hl=4 l=1714 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1699 cons: cont [ 0 ]
   19:d=2  hl=4 l=1695 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l= 832 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l= 817 cons: cont [ 0 ]
   60:d=5  hl=4 l= 813 prim: OCTET STRING      :{"ietf-voucher:voucher":
  877:d=3  hl=4 l= 501 cons: cont [ 0 ]
  881:d=4  hl=4 l= 497 cons: SEQUENCE
  885:d=5  hl=4 l= 376 cons: SEQUENCE
  889:d=6  hl=2 l=   3 cons: cont [ 0 ]
  891:d=7  hl=2 l=   1 prim: INTEGER           :02
  894:d=6  hl=2 l=   4 prim: INTEGER           :23CC8913
  900:d=6  hl=2 l=  10 cons: SEQUENCE
  902:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
  912:d=6  hl=2 l=  77 cons: SEQUENCE
  914:d=7  hl=2 l=  18 cons: SET
  916:d=8  hl=2 l=  16 cons: SEQUENCE
  918:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  930:d=9  hl=2 l=   2 prim: IA5STRING         :ca
  934:d=7  hl=2 l=  25 cons: SET
  936:d=8  hl=2 l=  23 cons: SEQUENCE
  938:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
  950:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
  961:d=7  hl=2 l=  28 cons: SET
  963:d=8  hl=2 l=  26 cons: SEQUENCE
  965:d=9  hl=2 l=   3 prim: OBJECT            :commonName
  970:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
  991:d=6  hl=2 l=  30 cons: SEQUENCE
  993:d=7  hl=2 l=  13 prim: UTCTIME           :190423232107Z
 1008:d=7  hl=2 l=  13 prim: UTCTIME           :190524092107Z
 1023:d=6  hl=2 l= 102 cons: SEQUENCE
 1025:d=7  hl=2 l=  15 cons: SET
 1027:d=8  hl=2 l=  13 cons: SEQUENCE
 1029:d=9  hl=2 l=   3 prim: OBJECT            :countryName
 1034:d=9  hl=2 l=   6 prim: PRINTABLESTRING   :Canada
 1042:d=7  hl=2 l=  18 cons: SET
 1044:d=8  hl=2 l=  16 cons: SEQUENCE
 1046:d=9  hl=2 l=   3 prim: OBJECT            :organizationName
 1051:d=9  hl=2 l=   9 prim: UTF8STRING        :Sandelman
 1062:d=7  hl=2 l=  19 cons: SET
 1064:d=8  hl=2 l=  17 cons: SEQUENCE
 1066:d=9  hl=2 l=   3 prim: OBJECT            :organizationalUnitName
 1071:d=9  hl=2 l=  10 prim: UTF8STRING        :honeydukes
 1083:d=7  hl=2 l=  42 cons: SET
 1085:d=8  hl=2 l=  40 cons: SEQUENCE
 1087:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1092:d=9  hl=2 l=  33 prim: UTF8STRING        :masa.honeydukes.sandelma
 1127:d=6  hl=2 l= 118 cons: SEQUENCE
 1129:d=7  hl=2 l=  16 cons: SEQUENCE
 1131:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 1140:d=8  hl=2 l=   5 prim: OBJECT            :secp384r1
 1147:d=7  hl=2 l=  98 prim: BIT STRING
 1247:d=6  hl=2 l=  16 cons: cont [ 3 ]
 1249:d=7  hl=2 l=  14 cons: SEQUENCE
 1251:d=8  hl=2 l=  12 cons: SEQUENCE
 1253:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 1258:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 1261:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 1265:d=5  hl=2 l=  10 cons: SEQUENCE
 1267:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1277:d=5  hl=2 l= 103 prim: BIT STRING
 1382:d=3  hl=4 l= 332 cons: SET
 1386:d=4  hl=4 l= 328 cons: SEQUENCE
 1390:d=5  hl=2 l=   1 prim: INTEGER           :01
 1393:d=5  hl=2 l=  85 cons: SEQUENCE
 1395:d=6  hl=2 l=  77 cons: SEQUENCE
 1397:d=7  hl=2 l=  18 cons: SET
 1399:d=8  hl=2 l=  16 cons: SEQUENCE
 1401:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1413:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 1417:d=7  hl=2 l=  25 cons: SET
 1419:d=8  hl=2 l=  23 cons: SEQUENCE
 1421:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 1433:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 1444:d=7  hl=2 l=  28 cons: SET
 1446:d=8  hl=2 l=  26 cons: SEQUENCE
 1448:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1453:d=9  hl=2 l=  19 prim: UTF8STRING        :Unstrung Highway CA
 1474:d=6  hl=2 l=   4 prim: INTEGER           :23CC8913
 1480:d=5  hl=2 l=  11 cons: SEQUENCE
 1482:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 1493:d=5  hl=2 l= 105 cons: cont [ 0 ]
 1495:d=6  hl=2 l=  24 cons: SEQUENCE
 1497:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 1508:d=7  hl=2 l=  11 cons: SET
 1510:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 1521:d=6  hl=2 l=  28 cons: SEQUENCE
 1523:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 1534:d=7  hl=2 l=  15 cons: SET
 1536:d=8  hl=2 l=  13 prim: UTCTIME           :190516025142Z
 1551:d=6  hl=2 l=  47 cons: SEQUENCE
 1553:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 1564:d=7  hl=2 l=  34 cons: SET
 1566:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:98461E22DB5423
 1600:d=5  hl=2 l=  10 cons: SEQUENCE
 1602:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1612:d=5  hl=2 l= 104 prim: OCTET STRING      [HEX DUMP]:30660231009860

Authors' Addresses

   Max Pritikin
   Cisco

   Email: pritikin@cisco.com

   Michael C. Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca
   URI:   http://www.sandelman.ca/

   Michael H. Behringer

   Email: Michael.H.Behringer@gmail.com

   Steinthor Bjarnason
   Arbor Networks

   Email: sbjarnason@arbor.net

   Kent Watsen
   Watsen Networks

   Email: kent+ietf@watsen.net