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ANIMA WG                                                     M. Pritikin
Internet-Draft                                                     Cisco
Intended status: Informational                             M. Richardson
Expires: September 18, 2016                                          SSW
                                                            M. Behringer
                                                            S. Bjarnason
                                                                   Cisco
                                                          March 17, 2016


                   Bootstrapping Key Infrastructures
               draft-ietf-anima-bootstrapping-keyinfra-02

Abstract

   This document specifies automated bootstrapping of a key
   infrastructure (BSKI) using vendor installed IEEE 802.1AR
   manufacturing installed certificates, in combination with a vendor
   based service on the Internet.  Before being authenticated, a new
   device has only link-local connectivity, and does not require a
   routable address.  When a vendor provides an Internet based service,
   devices can be forced to join only specific domains but in limited/
   disconnected networks or legacy environments we describe a variety of
   options that allow bootstrapping to proceed.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 18, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Scope of solution . . . . . . . . . . . . . . . . . . . .   5
     1.3.  Trust bootstrap . . . . . . . . . . . . . . . . . . . . .   6
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   6
   3.  Functional Overview . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Behavior of a New Entity  . . . . . . . . . . . . . . . .  10
       3.1.1.  Discovery . . . . . . . . . . . . . . . . . . . . . .  12
       3.1.2.  Identity  . . . . . . . . . . . . . . . . . . . . . .  13
       3.1.3.  Request Join  . . . . . . . . . . . . . . . . . . . .  14
       3.1.4.  Imprint . . . . . . . . . . . . . . . . . . . . . . .  14
       3.1.5.  Enrollment  . . . . . . . . . . . . . . . . . . . . .  15
       3.1.6.  Being Managed . . . . . . . . . . . . . . . . . . . .  16
     3.2.  Behavior of a Proxy . . . . . . . . . . . . . . . . . . .  16
       3.2.1.  CoAP connection to Registrar  . . . . . . . . . . . .  16
       3.2.2.  HTTPS proxy connection to Registrar . . . . . . . . .  17
     3.3.  Behavior of the Registrar (Bootstrap Server)  . . . . . .  18
       3.3.1.  Entity Authentication . . . . . . . . . . . . . . . .  19
       3.3.2.  Entity Authorization  . . . . . . . . . . . . . . . .  19
       3.3.3.  Claiming the New Entity . . . . . . . . . . . . . . .  20
       3.3.4.  Log Verification  . . . . . . . . . . . . . . . . . .  20
       3.3.5.  Forwarding Audit Token plus Configuration . . . . . .  21
     3.4.  Behavior of the MASA Service  . . . . . . . . . . . . . .  21
       3.4.1.  Issue Authorization Token and Log the event . . . . .  21
       3.4.2.  Retrieve Audit Entries from Log . . . . . . . . . . .  22
     3.5.  Leveraging the new key infrastructure / next steps  . . .  22
       3.5.1.  Network boundaries  . . . . . . . . . . . . . . . . .  22
     3.6.  Interactions with Network Access Control  . . . . . . . .  22
   4.  Domain Operator Activities  . . . . . . . . . . . . . . . . .  23
     4.1.  Instantiating the Domain Certification Authority  . . . .  23
     4.2.  Instantiating the Registrar . . . . . . . . . . . . . . .  23
     4.3.  Accepting New Entities  . . . . . . . . . . . . . . . . .  23
     4.4.  Automatic Enrollment of Devices . . . . . . . . . . . . .  24
     4.5.  Secure Network Operations . . . . . . . . . . . . . . . .  24
   5.  Protocol Details  . . . . . . . . . . . . . . . . . . . . . .  25
     5.1.  IEEE 802.1AR as client identity . . . . . . . . . . . . .  27



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     5.2.  EST over CoAP . . . . . . . . . . . . . . . . . . . . . .  28
     5.3.  Request Audit Token . . . . . . . . . . . . . . . . . . .  28
     5.4.  Request Audit Token from MASA . . . . . . . . . . . . . .  29
     5.5.  Basic Configuration Information Package . . . . . . . . .  30
     5.6.  Request MASA authorization log  . . . . . . . . . . . . .  31
   6.  Reduced security operational modes  . . . . . . . . . . . . .  32
     6.1.  Trust Model . . . . . . . . . . . . . . . . . . . . . . .  32
     6.2.  New Entity security reductions  . . . . . . . . . . . . .  33
     6.3.  Registrar security reductions . . . . . . . . . . . . . .  33
     6.4.  MASA security reductions  . . . . . . . . . . . . . . . .  34
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  34
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  36
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  36
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  36
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  37
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  38

1.  Introduction

   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 accepted
   that the initial connections between nodes are insecure, until key
   distribution is complete, or that domain-specific keying material is
   pre-provisioned on each new device in a costly and non-scalable
   manner.  This document describes a zero-touch approach to
   bootstrapping an entity by securing the initial distribution of key
   material using third-party generic keying material, such as a
   manufacturer installed IEEE 802.1AR certificate [IDevID], and a
   corresponding third-party service on the Internet.

   The two sides of an association being bootstrapped authenticate each
   other and then determine appropriate authorization.  This process is
   described as four distinct steps between the existing domain and the
   new entity being added:

   o  New entity authentication: "Who is this?  What is its identity?"

   o  New entity authorization: "Is it mine?  Do I want it?  What are
      the chances it has been compromised?"

   o  Domain authentication: "What is this domain's claimed identity?"

   o  Domain authorization: "Should I join it?"

   A precise answer to these questions can not be obtained without
   leveraging some established key infrastructure(s).  A complexity that
   this protocol deals with are dealing with devices from a variety of



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   vendors, and a network infrastructure (the domain) that is operated
   by parties that do not have any priviledged relationship with the
   device vendors.  The domain's decisions are based on the new entity's
   authenticated identity, as established by verification of previously
   installed credentials such as a manufacturer installed IEEE 802.1AR
   certificate, and verified back-end information such as a configured
   list of purchased devices or communication with a (unidirectionally)
   trusted third-party.  The new entity's decisions are made according
   to verified communication with a trusted third-party or in a strictly
   auditable fashion.

   Optimal security is achieved with IEEE 802.1AR certificates on each
   new entity, accompanied by a third-party Internet based service for
   verification.  Bootstrapping concepts run to completion with less
   requirements, but are then less secure.  A domain can choose to
   accept lower levels of security when a trusted third-party is not
   available so that bootstrapping proceeds even at the risk of reduced
   security.  Only the domain can make these decisions based on
   administrative input and known behavior of the new entity.

   The result of bootstrapping is that a domain specific key
   infrastructure is deployed.  Since IEEE 802.1AR PKI certificates are
   used for identifying the new entity, and the public key of the domain
   identity is leveraged during communications with an Internet based
   service, which is itself authenticated using HTTPS, bootstrapping of
   a domain specific Public Key Infrastructure (PKI) is described.
   Sufficient agility to support bootstrapping alternative key
   infrastructures (such as symmetric key solutions) is considered
   although no such alternate key infrastructure is described.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [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 domain trust anchor that is
      stored by the Domain CA.  This is consistent with the RFC5280
      Certification Authority subject key identifier of the Domain CA's
      self signed root certificate.  (A string value bound to the Domain
      CA's self signed root certificate subject and issuer fields is
      often colloquially used as a humanized identity value but during
      protocol discussions the more exact term as defined here is used).




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   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 identity 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].

   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 the identity provided to
      at the factory.  Neither the device nor the network knows if the
      device yet knows if this device belongs with this network.  This
      is definition 6, according to [pledge]

   Audit Token:  A signed token from the manufacturer authorized signing
      authority indicating that the bootstrapping event has been
      successfully logged.  This has been referred to as an
      "authorization token" indicating that it authorizes bootstrapping
      to proceed.

   Ownership Voucher:  A signed voucher from the vendor vouching that a
      specific domain "owns" the new entity as defined in
      [I-D.ietf-netconf-zerotouch].

1.2.  Scope of solution

   Questions have been posed as to whether this solution is suitable in
   general for Internet of Things (IoT) networks.  In general the answer
   is no, but the terminology of [RFC7228] is best used to describe the
   boundaries.

   The entire 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 described here is not intended to be
   useable as-is by constrained devices operating on challenged networks
   (such as 802.15.4 LLNs).



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   In many target applications, the systems involved are large router
   platforms with multi-gigabit inter-connections, mounted in controlled
   access data centers.  But this solution is not exclusive to the
   large, 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 the 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.

   Specifically, there are protocol aspects described here which 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).

   Some aspects are in scope for constrained devices on challenged
   networks: the certificate contents, and the process by which the four
   questions above are resolved is in scope.  It is simply the actual
   on-the-wire imprint protocol which is likely inappropriate.

1.3.  Trust bootstrap

   The imprint protocol results in a secure relationship between the
   domain registrar and the new device.  If the new device is
   sufficiently constrained that the ACE protocol should be leveraged
   for operation, (see [I-D.ietf-ace-actors]), and the domain registrar
   is also the Client Authorization Server or the Authorization Server,
   then it may be appropriate to use this secure channel to exchange ACE
   tokens.

2.  Architectural Overview

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




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   components.  Each component is logical and may be combined with other
   components as necessary.

                                             .
                                             .+------------------------+
      +--------------Drop Ship-------------->.| Vendor Service         |
      |                                      .+------------------------+
      |                                      .| M anufacturer|         |
      |                                      .| A uthorized  |Ownership|
      |                                      .| S igning     |Tracker  |
      |                                      .| A uthority   |         |
      |                                      .+--------------+---------+
      |                                      ..............  ^
      V                                                      |
   +-------+     ............................................|...
   |       |     .                                           |  .
   |       |     .  +------------+       +-----------+       |  .
   |       |     .  |            |       |           |       |  .
   |       |     .  |            |       |           <-------+  .
   |       |     .  |   Proxy    |       | Registrar |          .
   |       <-------->            <------->           |          .
   | New   |     .  |            |       |           |          .
   | Entity|     .  +------------+       +-----+-----+          .
   |       |     .                             |                .
   |       |     .           +-----------------+----------+     .
   |       |     .           | Domain Certification       |     .
   |       |     .           | Authority                  |     .
   +-------+     .           | Management and etc         |     .
                 .           +----------------------------+     .
                 .                                              .
                 ................................................
                               "Domain" components


   Figure 1

   Domain:  The set of entities that trust a common key infrastructure
      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 the Registrar and stores
      the trust anchor that defines the domain.  Optionally, it
      certifies all elements.





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   Registrar:  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 Registrar to control this process.  Typically a Registrar
      is "inside" its domain.

   New Entity:  A new device or virtual machine or software component
      that is not yet part of the domain.

   Proxy:  A domain entity that helps the New Entity join the domain.  A
      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.  The New Entity
      is unaware that they are communicating with a proxy rather than
      directly with the Registrar.

   MASA Service:  A Manufacturer Authorized Signing Authority (MASA)
      service on the global Internet.  The MASA provides a trusted
      repository for audit log information concerning privacy protected
      bootstrapping events.

   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.

   We assume a multi-vendor network.  In such an environment there could
   be a MASA or Ownership Tracker for each vendor that supports devices
   following this document's specification, or an integrator could
   provide a MASA service for all devices.  It is unlikely that an
   integrator could provide Ownership Tracking services for multiple
   vendors.

   This document describes a secure zero-touch approach to bootstrapping
   a key infrastructure; if certain devices in a network do not support
   this approach, they can still be bootstrapped manually.  Although
   manual deployment is not scalable and is not a focus of this document
   the necessary mechanisms are called out in this document to ensure
   such edge conditions are covered by the architectural and protocol
   models.








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3.  Functional Overview

   Entities behave in an autonomic fashion.  They discover each other
   and autonomically bootstrap into a key infrastructure delineating the
   autonomic domain.  See [I-D.irtf-nmrg-autonomic-network-definitions]
   for more information.

   This section details the state machine and operational flow for each
   of the main three entities.  The New Entity, the Domain (primarily
   the Registrar) and the MASA service.

   A representative flow is shown in Figure 2:

     +--------+         +-------+      +------------+     +------------+
     | New    |         | Proxy |      | Domain     |     | Vendor     |
     | Entity |         |       |      | Registrar  |     | Service    |
     |        |         |       |      |            |     | (Internet  |
     +--------+         +-------+      +------------+     +------------+
      |                     |                   |                    |
      |<-RFC3927 IPv4 adr   |                   |                    |
    or|<-RFC4862 IPv6 adr   |                   |                    |
      |                     |                   |                    |
      |-------------------->|                   |                    |
      | optional: mDNS query|                   |                    |
      | RFC6763/RFC6762     |                   |                    |
      |                     |                   |                    |
      |<--------------------|                   |                    |
      | mDNS broadcast      |                   |                    |
      | response or periodic|                   |                    |
      |                     |                   |                    |
      |<------------------->|<----------------->|                    |
      |         (d)TLS via the Proxy            |                    |
      |<--Registrar TLS server authentication---|                    |
  [PROVISIONAL accept of server cert]           |                    |
      P---IEEE 802.1AR client authentication--->|                    |
      P                     |                   |                    |
      P---Request Audit Token (include nonce)-->|                    |
      P                     |                   |                    |
      P                     |       /--->       |                    |
      P                     |       |      [accept device?]          |
      P                     |       |      [contact Vendor]          |
      P                     |       |           |--New Entity ID---->|
      P                     |       |           |--Domain ID-------->|
      P                     |       |           |--optional:nonce--->|
      P                     |       |           |     [extract DomainID]
      P                     |       |           |                    |
      P                     |    optional:      |     [update audit log]
      P                     |       |can        |                    |



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      P                     |       |occur      |     optional: is   |
      P                     |       |in         |     an ownership   |
      P                     |       |advance    |     voucher available?
      P                     |       |           |                    |
      P                     |       |           |<-device audit log--|
      P                     |       |           |<-audit token-------|
      P                     |       |           |                    |
      P                     |       |           |<-optional: --------|
      P                     |       \---->      |  ownership voucher |
      P                     |                   |                    |
      P                     |       [verify audit log or voucher]    |
      P                     |                   |                    |
      P<--Audit token and/or ownership voucher--|                    |
  [verify response         ]|                   |                    |
  [verify provisional cert ]|                   |                    |
      |                     |                   |                    |
      |---------------------------------------->|                    |
      | Continue with RFC7030 enrollment        |                    |
      | using now bidirectionally authenticated |                    |
      | TLS session.        |                   |                    |
      |                     |                   |                    |
      |                     |                   |                    |
      |                     |                   |                    |

   Figure 2

3.1.  Behavior of a New Entity

   A New Entity that has not yet been bootstrapped attempts to find a
   local domain and join it.  A New Entity MUST NOT automatically
   initiate bootstrapping if it has already been configured.

   States of a New Entity are as follows:


















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                +--------------+
                |   Start      |
                |              |
                +------+-------+
                       |
                +------v-------+
                |  Discover    |
   +------------>              |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            |  Identity    |
   ^------------+              |
   | rejected   +------+-------+
   |                   |
   |            +------v-------+
   |            | Request      |
   |            | Join         |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            |  Imprint     |   Optional
   ^------------+              <--+Manual input
   | Bad Vendor +------+-------+
   | response          |
   |            +------v-------+
   |            |  Enroll      |
   ^------------+              |
   | Enroll     +------+-------+
   | Failure           |
   |            +------v-------+
   |            |  Being       |
   ^------------+  Managed     |
    Factory     +--------------+
    reset


   Figure 3

   State descriptions for the New Entity are as follows:

   1.  Discover a communication channel to the "closest" Registrar.

   2.  Identify itself.  This is done by presenting an IEEE 802.1AR
       credentials to the discovered Registrar (via the Proxy) in a
       (d)TLS handshake.  (Although the Registrar is also authenticated
       these credentials are only provisionally accepted at this time).




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   3.  Requests to Join the discovered Registrar.  The acceptable
       imprint methods are indicated along with a nonce ensuring that
       any responses can be associated with this particular
       bootstrapping attempt.

   4.  Imprint on the Registrar.  This requires verification of the
       vendor service "Audit Token" or the validation of the vendor
       service "Ownership Voucher".  Either of these responses contains
       sufficient information for the New Entity to complete
       authentication of the Registrar.  (The New Entity can now finish
       authentication of the Registrar (d)TLS server certificate)

   5.  Enroll by accepting the domain specific information from the
       Registrar, and by obtaining a domain certificate from the
       Registrar using a standard enrollment protocol, e.g.  Enrollment
       over Secure Transport (EST) [RFC7030].

   6.  The New Entity 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.

   The following sections describe each of these steps in more detail.

3.1.1.  Discovery

   The result of discovery is logically communication with a Proxy
   instead of a Domain Registrar but in such a case the proxy
   facilitates communication with the actual Domain Registrar in a
   manner that is transparent to the New Entity.  Therefore or clarity a
   Proxy is always assumed.

   To discover the Domain Bootstrap Server the New Entity performs the
   following actions in this order:

   a.  MUST: Obtains a local address using either IPv4 or IPv6 methods
       as described in [RFC4862] IPv6 Stateless Address
       AutoConfiguration or [RFC3927] Dynamic Configuration of IPv4
       Link-Local Addresses.

   b.  MAY: Performs DNS-based Service Discovery [RFC6763] over
       Multicast DNS [RFC6762] searching for the service
       "_bootstrapks._tcp.local."

   c.  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.




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   d.  MAY: Performs DNS-based Service Discovery [RFC6763] over normal
       DNS operations.  In this case the domain is known so the service
       searched for is "_bootstrapks._tcp.example.com".

   e.  MAY: If no local bootstrapks service is located using the DNS-
       based Service Discovery methods the New Entity contacts a well
       known vendor provided bootstrapping server by performing a DNS
       lookup using a well known URI such as "bootstrapks.vendor-
       example.com".

   Once a Registrar is discovered (technically a communication channel
   through a Proxy) the New Entity communicates with the Registrar using
   the bootstrapping protocol defined in Section 5.  The current DNS
   services returned during each query is maintained until bootstrapping
   is completed.  If bootstrapping fails and the New Entity 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 New Entity moves on to
   normal DNS-based Service Discovery.

   Once all discovered services are attempted the device SHOULD return
   to Multicast DNS and keep trying.  The New Entity may prioritize
   selection order as appropriate for the anticipated environment.

   [[EDNOTE: An appropriate backoff or rate limiting strategy should be
   defined here such that the device doesn't flood the local network
   with queries.  If the device were to eventually give up -- or at
   least have too long between attempts -- a power cycle would restart
   the backoff mechanism.]]

3.1.2.  Identity

   The New Entity identifies itself during the communication protocol
   handshake.  If the client identity is rejected the New Entity repeats
   the Discovery process using the next proxy or discovery method
   available.

   The bootstrapping protocol server is not authenticated.  Thus this
   connection is provisional and all data received is untrusted until
   sufficiently validated even though it is over a (D)TLS connection.
   This is aligned with the existing provisional mode of EST [RFC7030]
   during s4.1.1 "Bootstrap Distribution of CA Certificates".

   All security associations established are between the new device and
   the Bootstrapping server regardless of proxy operations.





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3.1.3.  Request Join

   The New Entity POSTs a request to join the domain to the
   Bootstrapping server.  This request contains a New Entity generated
   nonce and informs the Bootstrapping server which imprint methods the
   New Entity will accept.

   As indicated in EST [RFC7030] the bootstrapping server MAY redirect
   the client to an alternate server.  This is most useful in the case
   where the New Entity has resorted to a well known vendor URI and is
   communicating with the vendor's Registrar directly.  In this case the
   New Entity has authenticated the Registrar using the local Implicit
   Trust Anchor database and can therefore treat the redirect URI as a
   trusted URI which can also be validated using the Implicit Trust
   Anchor database.  Since client authentication occurs during the TLS
   handshake the bootstrapping server has sufficient information to
   apply appropriate policy concerning which server to redirect to.

   The nonce ensures the New Entity can verify that responses are
   specific to this bootstrapping attempt.  This minimizes the use of
   global time and provides a substantial benefit for devices without a
   valid clock.

3.1.4.  Imprint

   The domain trust anchor is received by the New Entity during the
   bootstrapping protocol methods in the form of either an Audit Token
   containing the domainID or an explicit ownership voucher.  The goal
   of the imprint state is to securely obtain a copy of this trust
   anchor without involving human interaction.

   The enrollment protocol EST [RFC7030] details a set of non-autonomic
   bootstrapping methods such as:

   o  using the Implicit Trust Anchor database (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).



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   This document describes additional autonomic methods:

   MASA audit token  Audit tokens are obtained by the Registrar from the
      MASA service and presented to the New Entity for validation.
      These indicate to the New Entity that joining the domain has been
      logged by a trusted logging server.

   Ownership Voucher  Ownership Vouchers are obtained by the Registrar
      from the MASA service and explicitly indicate the fully qualified
      domain name of the domain the new entity currently belongs to.
      The Ownership Voucher is defined in [I-D.ietf-netconf-zerotouch].

   Since client authentication occurs during the TLS handshake the
   bootstrapping server has sufficient information to apply appropriate
   policy concerning which method to use.

   An arbitrary basic configuration information package that is signed
   by the domain can be delivered alongside the Audit Token or ownership
   validation.  This information is signed by the domain private keys
   and is a one time delivery containing information such as which
   enrollment server to communicate with and which management system to
   communicate with.  It is intended as a limited basic configuration
   for these purposes and is not intended to deliver entire final
   configuration to the device.

   If the autonomic methods fail the New Entity returns to discovery
   state and attempts bootstrapping with the next available discovered
   Registrar.

3.1.5.  Enrollment

   As the final step of bootstrapping a Registrar helps to issue a
   domain specific credential to the New Entity.  For simplicity in this
   document, a Registrar primarily facilitates issuing a credential by
   acting as an RFC5280 Registration Authority for the Domain
   Certification Authority.

   Enrollment proceeds as described in Enrollment over Secure Transport
   (EST) [RFC7030].  The New Entity contacts the Registrar using EST as
   indicated:

   o  The New Entity is authenticated using the IEEE 802.1AR
      credentials.

   o  The EST section 4.1.3 CA Certificates Response is verified using
      either the Audit Token which provided the domain identity -or-





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   o  The EST server is authenticated by using the Ownership Voucher
      indicated fully qualified domain name to build the EST URI such
      that EST section 4.1.1 bootstrapping using the New Entity implicit
      Trust Anchor database can be used.

3.1.6.  Being Managed

   Functionality to provide generic "configuration" information is
   supported.  The parsing of this data and any subsequent use of the
   data, for example communications with a Network Management System is
   out of scope but is expected to occur after bootstrapping enrollment
   is complete.  This ensures that all communications with management
   systems which can divulge local security information (e.g. network
   topology or raw key material) is secured using the local credentials
   issued during enrollment.

   The New Entity uses bootstrapping to join only one domain.
   Management by multiple domains is out-of-scope of bootstrapping.
   After the device has successfully joined a domain and is being
   managed it is plausible that the domain can insert credentials for
   other domains depending on the device capabilities.

   See Section 3.5.

3.2.  Behavior of a Proxy

   The role of the Proxy is to facilitate communications.  The Proxy
   forwards packets between the New Entity and the Registrar that has
   been configured on the Proxy.  The Proxy does not terminate the
   (d)TLS handshake.

   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 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 of the alternative proxy methods.

3.2.1.  CoAP connection to Registrar

   The proxy MUST implement an IPIP (protocol 41) encapsulation function
   for CoAP traffic to the configured UDP port on the registrar.  The
   proxy does not terminate the CoAP DTLS connection.  [[EDNOTE: The
   choice of CoAP as the mandatory to implement protocol rather than



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   HTTP maximizes code reuse on the smallest of devices.  Unfortunately
   this means this document will have to include the EST over CoAP
   details as additional sections.  The alternative is to make 'HTTPS
   proxy' method the mandatory to implement and provide a less friendly
   environment for the smallest of devices.  This is a decision we'll
   have to see addressed by the broader team.]]

   As a result of the Proxy Discovery process in section Section 3.1.1,
   the port number exposed by the proxy does not need to be well known,
   or require an IANA allocation.  The address and port of the Registrar
   will be discovered by the GRASP protocol inside the ACP.  For the
   IPIP encapsulation methods, the port announced by the Proxy MUST be
   the same as on the registrar.

   The IPIP encapsulation allows the proxy to forward traffic which is
   otherwise not to be forwarded, as the traffic between New Node and
   Proxy use IPv6 Link Local addresses.

   If the Proxy device has more than one interface on which it offers
   the proxy function, then it must select a unique IP address per
   interface in order so that the proxy can stateless return the reply
   packets to the correct link.

3.2.2.  HTTPS proxy connection to Registrar

   The proxy SHOULD also provide one of: an IPIP encapsulation of HTTP
   traffic on TCP port TBD to the registrar, an HTTP proxy which accepts
   URLs that reach the Registrar, or a TCP circuit proxy that connects
   the New Node to the Registrar.

   In order to make the HTTP choice above transparent to the New Node,
   the New Node will always initiate an HTTP connection, and will always
   send an appropriate CONNECT message to initiate an HTTPS connection
   to the registrar.  [[EDNOTE: The CONNECT syntax is that the New
   Entity specifies the Registrar server in the CONNECT line.  See
   RFC7231 s4.3.6.  We wish the Proxy to override any value with the
   locally known-to-the-proxy Registrar address.]]

   When the Proxy provides a circuit proxy to the Registrar the
   Registrar MUST accept HTTP connections, and be willing to perform an
   HTTP proxy (CONNECT) operation to itself, and then initiate HTTPS.

   When the Proxy provides a stateless IPIP encapsulation to the
   Registrar, then the Registrar will have to perform IPIP
   decapsulation, remembering the originating outer IPIP source address
   in order to qualify the inner link-local address.  Being able to
   connect a TCP (HTTP) or UDP (CoAP) socket to a link-local address
   with an encapsulated IPIP header requires API extensions beyond



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   [RFC3542] for UDP use, and requires a form of connection latching
   (see section 4.1 of [RFC5386] and all of [RFC5660], except that a
   simple IPIP tunnel is used rather than an IPsec tunnel).

3.3.  Behavior of the Registrar (Bootstrap Server)

   Once a Registrar is established it listens for new entities and
   determines if they can join the domain.  The registrar delivers any
   necessary authorization information to the new device and facilitates
   enrollment with the domain PKI.

   Registrar behavior is as follows:

   Contacted by New Entity
           +
           |
   +-------v----------+
   | Entity           | fail?
   | Authentication   +---------+
   +-------+----------+         |
           |                    |
   +-------v----------+         |
   | Entity           | fail?   |
   | Authorization    +--------->
   +-------+----------+         |
           |                    |
   +-------v----------+         |
   | Claiming the     | fail?   |
   | Entity           +--------->
   +-------+----------+         |
           |                    |
   +-------v----------+         |
   | Log Verification | fail?   |
   |                  +--------->
   +-------+----------+         |
           |                    |
   +-------v----------+    +----v-------+
   | Forward          |    |            |
   | Audit            |    | Reject     |
   | token + config   |    | Device     |
   | to the Entity    |    |            |
   +------------------+    +------------+

   Figure 4







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3.3.1.  Entity Authentication

   The applicable authentication methods detailed in EST [RFC7030] are:

   o  the use of an IEEE 802.1AR IDevID credential,

   o  or the use of a secret that is transmitted out of band between the
      New Entity and the Registrar (this use case is not autonomic).

3.3.2.  Entity Authorization

   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 IEEE
      802.1AR device identity),

   o  allow any device from a specific vendor (as determined by the IEEE
      802.1AR identity),

   o  allow a specific device from a vendor (as determined by the IEEE
      802.1AR identity)

   Since all New Entities accept Audit Tokens the Registrar MUST use the
   vendor provided MASA service to verify that the device's history log
   does not include unexpected Registrars.  If a device had previously
   registered with another domain, the Registrar of that domain would
   show in the log.

   In order to validate the IEEE 802.1AR device identity the Registrar
   maintains a database of vendor trust anchors (e.g. vendor root
   certificates or keyIdentifiers for vendor root public keys).  For
   user interface purposes this database can be mapped to colloquial
   vendor names.  Registrars can be shipped with the trust anchors of a
   significant number of third-party vendors within the target market.

   If a device is accepted into the domain, it is expected request a
   domain certificate through a certificate enrollment process.  The
   result is a common trust anchor and device certificates for all
   autonomic devices in a domain (these certificates can subsequently be
   used to determine the boundaries of the homenet, to authenticate
   other domain nodes, and to autonomically enable services on the
   homenet).  The authorization performed during this phase MAY be




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   cached for the TLS session and applied to subsequent EST enrollment
   requests so long as the session lasts.

3.3.3.  Claiming the New Entity

   Claiming an entity establishes an audit log at the MASA server and
   provides the Registrar with proof, in the form of a MASA
   authorization token, that the log entry has been inserted.  As
   indicated in Section 3.1.4 a New Entity will only proceed with
   bootstrapping if a validated MASA authorization token has been
   received.  The New Entity therefore enforces that bootstrapping only
   occurs if the claim has been logged.  There is no requirement for the
   vendor to definitively know that the device is owned by the
   Registrar.

   Registrar's obtain the Vendor URI via static configuration or by
   extracting it from the IEEE 802.1AR credential.  The imprint method
   supported by the New Entity is known from the IEEE 802.1AR
   credential.  [[EDNOTE: An appropriate extension for indicating the
   Vendor URI and imprint method could be defined using the methods
   described in [I-D.lear-mud-framework]]].

   During initial bootstrapping the New Entity provides a nonce specific
   to the particular bootstrapping attempt.  The Registrar SHOULD
   include this nonce when claiming the New Entity from the MASA
   service.  Claims from an unauthenticated Registrar are only serviced
   by the MASA resource if a nonce is provided.

   The Registrar can claim a New Entity that is not online by forming
   the request using the entities unique identifier and not including a
   nonce in the claim request.  Audit Tokens obtained in this way do not
   have a lifetime and they provide a permanent method for the domain to
   claim the device.  Evidence of such a claim is provided in the audit
   log entries available to any future Registrar.  Such claims reduce
   the ability for future domains to secure bootstrapping and therefore
   the Registrar MUST be authenticated by the MASA service.

   An ownership voucher requires the vendor to definitively know that a
   device is owned by a specific domain.  The method used to "claim"
   this are out-of-scope.  The Registrar simply requests an ownership
   validation token and the New Entity trusts the response.

3.3.4.  Log Verification

   The Registrar requests the log information for the new entity from
   the MASA service.  The log is verified to confirm that the following
   is true to the satisfaction of the Registrar's configured policy:




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   o  Any nonceless entries in the log are associated with domainIDs
      recognized by the registrar.

   o  Any nonce'd entries are older than when the domain is known to
      have physical possession of the new entity or that the domainIDs
      are recognized by the registrar.

   If any of these criteria are unacceptable to the registrar the entity
   is rejected.  The 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.

3.3.5.  Forwarding Audit Token plus Configuration

   The Registrar forwards the received Audit Token to the New Entity.
   To simplify the message flows an initial configuration package can be
   delivered at this time which is signed by a representative of the
   domain.

   [[EDNOTE: format TBD.  The configuration package signature data must
   contain the full certificate path sufficient for the new entity to
   use the domainID information (as a trust anchor) to accept and
   validate the configuration)]]

3.4.  Behavior of the MASA Service

   The MASA service is provided by the Factory provider on the global
   Internet.  The URI of this service is well known.  The URI SHOULD
   also be provided as an IEEE 802.1AR IDevID X.509 extension (a "MASA
   Audit Token Distribution Point" extension).

   The MASA service provides the following functionalities to
   Registrars:

3.4.1.  Issue Authorization Token and Log the event

   A Registrar POSTs a claim message optionally containing the bootstrap
   nonce to the MASA server.

   If a nonce is provided the MASA service responds to all requests.
   The MASA service verifies the Registrar is representative of the
   domain and generates a privacy protected log entry before responding
   with the Audit Token.

   If a nonce is not provided then the MASA service MUST authenticate
   the Registrar as a valid customer.  This prevents denial of service
   attacks.




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3.4.2.  Retrieve Audit Entries from Log

   When determining if a New Entity should be accepted into a domain the
   Registrar retrieves a copy of the audit log from the MASA service.
   This contains a list of privacy protected domain identities that have
   previously claimed the device.  Included in the list is an indication
   of the time the entry was made and if the nonce was included.

3.5.  Leveraging the new key infrastructure / next steps

   As the devices have a common trust anchor, device identity can be
   securely established, making it possible to automatically deploy
   services across the domain in a secure manner.

   Examples of services:

   o  Device management.

   o  Routing authentication.

   o  Service discovery.

3.5.1.  Network boundaries

   When a device has joined the domain, it can validate the domain
   membership of other devices.  This makes it possible to create trust
   boundaries where domain members have higher level of trusted than
   external devices.  Using the autonomic User Interface, specific
   devices can be grouped into to sub domains and specific trust levels
   can be implemented between those.

3.6.  Interactions with Network Access Control

   The assumption is that Network Access Control (NAC) completes using
   the New Entity 802.1AR credentials and results in the device having
   sufficient connectivity to discovery and communicate with the proxy.
   Any additional connectivity or quarantine behavior by the NAC
   infrastructure is out-of-scope.  After the devices has completed
   bootstrapping the mechanism to trigger NAC to re-authenticate the
   device and provide updated network privileges is also out-of-scope.

   This achieves the goal of a bootstrap architecture that can integrate
   with NAC but does not require NAC within the network where it wasn't
   previously required.  Future optimizations can be achieved by
   integrating the bootstrapping protocol directly into an initial EAP
   exchange.





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4.  Domain Operator Activities

   This section describes how an operator interacts with a domain that
   supports the bootstrapping as described in this document.

4.1.  Instantiating the Domain Certification Authority

   This is a one time step by the domain administrator.  This is an "off
   the shelf" CA with the exception that it is designed to work as an
   integrated part of the security solution.  This precludes the use of
   3rd party certification authority services that do not provide
   support for delegation of certificate issuance decisions to a domain
   managed Registration Authority.

4.2.  Instantiating the Registrar

   This is a one time step by the domain administrator.  One or more
   devices in the domain are configured take on a Registrar function.

   A device can be configured to act as a Registrar or a device can
   auto-select itself to take on this function, using a detection
   mechanism to resolve potential conflicts and setup communication with
   the Domain Certification Authority.  Automated Registrar selection is
   outside scope for this document.

4.3.  Accepting New Entities

   For each New Entity the Registrar is informed of the unique
   identifier (e.g. serial number) along with the manufacturer's
   identifying information (e.g. manufacturer root certificate).  This
   can happen in different ways:

   1.  Default acceptance: In the simplest case, the new device asserts
       its unique identity to the registrar.  The registrar accepts all
       devices without authorization checks.  This mode does not provide
       security against intruders and is not recommended.

   2.  Per device acceptance: The new device asserts its unique identity
       to the registrar.  A non-technical human validates the identity,
       for example by comparing the identity displayed by the registrar
       (for example using a smartphone app) with the identity shown on
       the packaging of the device.  Acceptance may be triggered by a
       click on a smartphone app "accept this device", or by other forms
       of pairing.  See also [I-D.behringer-homenet-trust-bootstrap] for
       how the approach could work in a homenet.

   3.  Whitelist acceptance: In larger networks, neither of the previous
       approaches is acceptable.  Default acceptance is not secure, and



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       a manual per device methods do not scale.  Here, the registrar is
       provided a priori with a list of identifiers of devices that
       belong to the network.  This list can be extracted from an
       inventory database, or sales records.  If a device is detected
       that is not on the list of known devices, it can still be
       manually accepted using the per device acceptance methods.

   4.  Automated Whitelist: an automated process that builds the
       necessary whitelists and inserts them into the larger network
       domain infrastructure is plausible.  Once set up, no human
       intervention is required in this process.  Defining the exact
       mechanisms for this is out of scope although the registrar
       authorization checks is identified as the logical integration
       point of any future work in this area.

   None of these approaches require the network to have permanent
   Internet connectivity.  Even when the Internet based MASA service is
   used, it is possible to pre-fetch the required information from the
   MASA a priori, for example at time of purchase such that devices can
   enroll later.  This supports use cases where the domain network may
   be entirely isolated during device deployment.

   Additional policy can be stored for future authorization decisions.
   For example an expected deployment time window or that a certain
   Proxy must be used.

4.4.  Automatic Enrollment of Devices

   The approach outlined in this document provides a secure zero-touch
   method to enroll new devices without any pre-staged configuration.
   New devices communicate with already enrolled devices of the domain,
   which proxy between the new device and a Registrar.  As a result of
   this completely automatic operation, all devices obtain a domain
   based certificate.

4.5.  Secure Network Operations

   The certificate installed in the previous step can be used for all
   subsequent operations.  For example, to determine the boundaries of
   the domain: If a neighbor has a certificate from the same trust
   anchor it can be assumed "inside" the same organization; if not, as
   outside.  See also Section 3.5.1.  The certificate can also be used
   to securely establish a connection between devices and central
   control functions.  Also autonomic transactions can use the domain
   certificates to authenticate and/or encrypt direct interactions
   between devices.  The usage of the domain certificates is outside
   scope for this document.




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5.  Protocol Details

   For simplicity the bootstrapping protocol is described as extensions
   to EST [RFC7030].

   EST provides a bootstrapping mechanism for new entities that are
   configured with the URI of the EST server such that the Implicit TA
   database can be used to authenticate the EST server.  Alternatively
   EST clients can "engage a human user to authorize the CA certificate
   using out-of-band data such as a CA certificate".  EST does not
   provide a completely automated method of bootstrapping the PKI as
   both of these methods require some user input (either of the URI or
   authorizing the CA certificate).

   This section details additional EST functionality that support
   automated bootstrapping of the public key infrastructure.  These
   additions provide for fully automated bootstrapping.  These additions
   are to be optionally supported by the EST server within the same
   .well-known URI tree as the existing EST URIs.

   The "New Entity" is the EST client and the "Registrar" is the EST
   server.

   The extensions for the client are as follows:

   o  The New Entity provisionally accept the EST server certificate
      during the TLS handshake as detailed in EST section 4.1.1
      ("Bootstrap Distribution of CA Certificates").

   o  The Registrar requests and validates the Audit Token from the
      vendor authorized MASA service.

   o  The New Entity requests and validates the Audit Token as described
      below.  At this point the New Entity has sufficient information to
      validate domain credentials.

   o  The New Entity calls the EST defined /cacerts method to obtain the
      current CA certificate.  These are validated using the Audit
      Token.

   o  The New Entity completes bootstrapping as detailed in EST section
      4.1.1.

   These extensions could be implemented as an independent protocol from
   EST but since the overlap with basic enrollment is extensive,
   particularly with respect to client authorization, they are presented
   here as additions to EST.




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   In order to obtain a validated Audit Token and Audit Log the
   Registrar contacts the MASA service Service using REST calls:

              +-----------+ +----------+ +-----------+ +----------+
              | New       | |          | |           | |          |
              | Entity    | | Proxy    | | Registrar | | Vendor   |
              |           | |          | |           | |          |
              ++----------+ +--+-------+ +-----+-----+ +--------+-+
               |               |               |                |
               |               |               |                |
               | (D)TLS hello  |               |                |
   Establish   +---------------> (D)TLS hello  |                |
   (D)TLS      |               |--------------->                |
   connection  |          (forwarding)         |                |
               | Server Cert   <---------------+                |
               <---------------+               |                |
               | Client Cert   |               |                |
               +------------------------------->                |
               |               |               |                |
   HTTP REST   | POST /requestaudittoken       |                |
   Data        +--------------------nonce------>                |
               |               .               | /requestaudittoken
               |               .               +---------------->
               |                               <----------------+
               |                               | /requestauditlog
               |                               +---------------->
               | audit token or owner voucher  <----------------+
               <-------------------------------+                |
               | (optional config information) |                |
               |               .               |                |
               |               .               |                |

   Figure 5

   In some use cases the Registrar may need to contact the Vendor in
   advanced, for example when the target network is air-gapped.  The
   nonceless request format is provided for this and the resulting flow
   is slightly different.  The security differences associated with not
   knowing the nonce are discussed below:












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              +-----------+ +----------+ +-----------+ +----------+
              | New       | |          | |           | |          |
              | Entity    | | Proxy    | | Registrar | | Vendor   |
              |           | |          | |           | |          |
              ++----------+ +--+-------+ +-----+-----+ +--------+-+
               |               |               |                |
               |               |               |                |
               |               |               | /requestaudittoken
               |               |  (nonce       +---------------->
               |               |  unknown)     <----------------+
               |               |               | /requestauditlog
               |               |               +---------------->
               |               |               <----------------+
               | (D)TLS hello  |               |                |
   Establish   +---------------> (D)TLS hello  |                |
   (D)TLS      |               |--------------->                |
   connection  |          (forwarding)         |                |
               | SerVer Cert   <---------------+                |
               <---------------+               |                |
               | Client Cert   |               |                |
               +------------------------------->                |
               |               |               |                |
   HTTP REST   | POST /requestaudittoken       |                |
   Data        +----------------------nonce---->   (discard     |
               | audit token or owner Voucher  |   nonce)       |
               <-------------------------------+                |
               | (optional config information) |                |
               |               .               |                |
               |               .               |                |

   Figure 6

5.1.  IEEE 802.1AR as client identity

   The Registrar authenticates the client and performs authorization
   checks to ensure this client is expected to join the domain.  This
   require a common procedure for representing and verifying the
   identity of the client.  The methods detailed in [RFC6125] such as
   matching DNS Domain Name or Application Service Type are not directly
   applicable.

   Clients presents an IEEE 802.AR certificate complete with subject
   field identifying the device uniquely in the Distinguished Name
   serialNumber subfield.  The subjectAltName MAY contain a
   hardwareModuleName as specified in RFC4108.  The Registrar extracts
   this information and compares against a per vendor access control
   list.  (This can be implemented with a single database table so long




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   as the authority key identifier is also maintained and checked to
   ensure that no two vendors collide in their use of serialNumber's).

   When enrollment is complete and a local certificate is issued to the
   new device the local CA has complete control over the namespace.  If
   this credential is intended for RFC6125 style TLS connections where
   servers are identified by a server's DNS-ID identity the CA is likely
   to ensure the dNSName field is populated.  For Anima purposes the
   IEEE 802.1AR serialNumber and hardwareModuleName fields MUST be
   propagated to the issued certificate.

   [[EDNOTE: the above authority key identifier trick works for database
   lookups and here the inclusion of the DNS name would serve the same
   purpose.  Alternatively an Anima specified domain specific identifier
   must be indicated.]]

5.2.  EST over CoAP

   [[EDNOTE: In order to support smaller devices the above section on
   Proxy behavior introduces mandatory to implement support for CoAP
   support by the Proxy.  This implies similar support by the New Entity
   and Registrar and means that the EST protocol operation encapsulation
   into CoAP needs to be described.  EST is HTTP based and "CoaP is
   designed to easily interface with HTTP for integration" [RFC7252] so
   this section is anticipated to be relatively straightforward.  A
   complexity is that the large message sizes necessary for
   bootstrapping will require support for [draft-ietf-core-block].]]

5.3.  Request Audit Token

   When the New Entity reaches the EST section 4.1.1 "Bootstrap
   Distribution of CA Certificates" state but wishes to proceed in a
   fully automated fashion it makes a request for a MASA authorization
   token from the Registrar.

   This is done with an HTTPS POST using the operation path value of
   "/requestaudittoken".

   The request format is JSON object containing a nonce.

   Request media type: application/auditnonce

   Request format: a JSON file with the following:

   {"nonce":"<64bit nonce value>", "OwnershipValidation":boolean}

   [[EDNOTE: exact format TBD.  There is an advantage to having the
   client sign the nonce (similar to a PKI Certification Signing



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   Request) since this allows the MASA service to confirm the actual
   device identity.  It is not clear that there is a security benefit
   from this since its the New Entity that verifies the nonce.]]

   The Registrar validates the client identity as described in EST
   [RFC7030] section 3.3.2.  The registrar performs authorization as
   detailed in Section 3.3.2.  If authorization is successful the
   Registrar obtains an Audit Token from the MASA service (see
   Section 5.2).

   The received MASA authorization token is returned to the New Entity.

   As indicated in EST [RFC7030] the bootstrapping server can redirect
   the client to an alternate server.  If the New Entity authenticated
   the Registrar using the well known URI method then the New Entity
   MUST follow the redirect automatically and authenticate the new
   Registrar against the redirect URI provided.  If the New Entity had
   not yet authenticated the Registrar because it was discovered and was
   not a known-to-be-valid URI then the new Registrar must be
   authenticated using one of the two autonomic methods described in
   this document.

5.4.  Request Audit Token from MASA

   The Registrar requests the Audit Token from the MASA service using a
   REST interface.  For simplicity this is defined as an optional EST
   message between the Registrar and an EST server running on the MASA
   service although the Registrar is not required to make use of any
   other EST functionality when communicating with the MASA service.
   (The MASA service MUST properly reject any EST functionality requests
   it does not wish to service; a requirement that holds for any REST
   interface).

   This is done with an HTTP POST using the operation path value of
   "/requestaudittoken".

   The request format is a JSON object optionally containing the nonce
   value (as obtained from the bootstrap request) and the IEEE 802.1AR
   identity of the device as a serial number (the full certificate is
   not needed and no proof-of-possession information for the device
   identity is included).  The New Entity's serial number is extracted
   from the IEEE 802.1AR subject name:

   {"nonce":"<64bit nonce value>", "serialnumber", "<subjectname/
   subjectaltname serial number>"}

   The Registrar MAY exclude the nonce from the request.  Doing so
   allows the Registrar to request an authorization token when the New



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   Entity is not online, or when the target bootstrapping environment is
   not on the same network as the MASA server.  If a nonce is not
   provided the MASA server MUST authenticate the client as described in
   EST [RFC7030] section 3.3.2.  The registrar performs authorization as
   detailed in Section 3.3.2.  If authorization is successful the
   Registrar obtains an Audit Token from the MASA service (see
   Section 5.4).

   The JSON message information is encapsulated in a PKCS7 signed data
   structure that is signed by the Registrar.  The entire certificate
   chain, up to and including the Domain CA, MUST be included in the
   PKCS7.

   The MASA service checks the internal consistency of the PKCS7 but MAY
   not authenticate the domain identity information.  The domain is not
   know to the MASA server in advance and a shared trust anchor is not
   implied.  The MASA server MUST verify that the PKCS7 is signed by a
   Registrar certificate (by checking for the cmc-idRA field) that was
   issued by a the root certificate included in the PKCS7.  This ensures
   that the Registrar is in fact an authorized Registrar of the unknown
   domain.

   The domain ID (e.g. hash of the public key of the domain) is
   extracted from the root certificate and is used to populate the MASA
   authorization token and to update the audit log.  The authorization
   token consists of the nonce, if supplied, the serialnumber and the
   domain identity:

   {"nonce":"<64bit nonce value>", "serialnumber", "<subjectname/
   subjectaltname serial number>","domainID":}

   [[EDNOTE: There is a strong similarity between this and the previous
   section.  Both involve requesting the Audit Token from the upstream
   element.  Because there are differing requirements on the data
   submitted and the signing of that data they are specified in distinct
   sections.  The design team should have a meeting to discuss how to
   unify these sections or make the distinctions more clear]]

5.5.  Basic Configuration Information Package

   When the MASA authorization token is returned to the New Entity an
   arbitrary information package can be signed and delivered along side
   it.  This is signed by the Domain Registrar.  The New Entity first
   verifies the Audit Token and, if it is valid, then uses the domain's
   TA to validate the Information Package.

   [[EDNOTE: The domainID as included in the log and as sent in the
   authorization token is only a hash of the domain root certificate.



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   This is insufficient for the new entity to move out of the
   provisional state as it needs a full root certificate to validate the
   TLS certificate chain.  This information package could be used to
   deliver the full certificate or the full certificate could be
   included in the authorization token.  Lacking either the new entity
   needs to stay in the provisional state until it performs an RFC7030
   /getcacerts to obtain the full certificate chain.]]

   [[EDNOTE: The package format to be specified here.  Any signed format
   is viable and ideally one can simply be specified from netconf.  The
   Registar knows the New Entity device type from the 802.1AR credential
   and so is able to determine the proper format for the
   configuration.]]

5.6.  Request MASA authorization log

   A registrar requests the MASA authorization log from the MASA service
   using this EST extension.

   This is done with an HTTP GET using the operation path value of
   "/requestMASAlog".

   The log data returned is a file consisting of all previous log
   entries.  For example:

   "log":[
     {"date":"<date/time of the entry>"},
      "domainID":"<domainID as extracted from the root
                   certificate within the PKCS7 of the
                   audit token request>",
      "nonce":"<any nonce if supplied (or NULL)>"},

     {"date":"<date/time of the entry>"},
      "domainID":"<domainID as extracted from the root
                   certificate within the PKCS7 of the
                   audit token request>",
      "nonce":"<any nonce if supplied (or NULL)>"},
   ]

   Distribution of a large log is less than ideal.  This structure can
   be optimized as follows: All nonce-less entries for the same domainID
   can be condensed into the single most recent nonceless entry.

   The Registrar uses this log information to make an informed decision
   regarding the continued bootstrapping of the New Entity.  For example
   if the log includes unexpected domainIDs this is indicative of
   problematic imprints by the new entity.  If unexpected nonce-less
   entries exist this is indicative of the permanent ability for the



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   unknown domain to trigger a reset of the device and take over
   management of it.  Equipment that is purchased pre-owned can be
   expected to have an extensive history.

   Log entries containing the Domain's ID can be compared against local
   history logs in search of discrepancies.

   [[EDNOTE: certificate transparency style use of merkle tree hash's
   might offer an alternative log entry method]]

6.  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 New Entity, Registrar and MASA
   can be configured to run in a less secure mode for the indicated
   reasons.

6.1.  Trust Model

   +--------+         +-------+      +------------+     +------------+
   | New    |         | Proxy |      | Domain     |     | Vendor     |
   | Entity |         |       |      | Registrar  |     | Service    |
   |        |         |       |      |            |     | (Internet  |
   +--------+         +-------+      +------------+     +------------+

   Figure 7

   New Entity:  The New Entity 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.

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

   Registrar:  When interacting with a MASA server the Registrar makes
      all decisions.  When ownership vouchers are involved the Registrar
      is only a conduit and all security decisions are made on the
      vendor service.

   Vendor Service, MASA:  This form of vendor 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.  [[EDNOTE: these claims could
      be strengthened using by using cryptographic log techniques to




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      provide append only", cryptographic assured, publicly auditable
      logs.  Current text provides for a fully trusted vendor.]]

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

6.2.  New Entity security reductions

   Although New Entity can choose to run in less secure modes this is
   MUST NOT be the default state because it permanently degrades the
   security for all other uses cases.

   The device may have an operational mode where it skips Audit Token or
   Ownership Voucher validation one time.  For example if a physical
   button is depressed during the bootstrapping operation.  This can be
   useful if the vendor service is unavailable.  This behavior SHOULD be
   available via local configuration or physical presence methods to
   ensure new entities can always be deployed even when autonomic
   methods fail.  This allows for unsecure imprint.

   It is RECOMMENDED that this only be available if hardware assisted
   NEA [RFC5209] is supported.

6.3.  Registrar security reductions

   The Registrar can choose to accept devices using less secure methods.
   These methods are RECOMMENDED when low security models are needed as
   the security decisions are being made by the local administrator:

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

   2.  The registrar MAY choose to accept devices that claim a unique
       identity without the benefit of authenticating that claimed
       identity.  This could occur when the New Entity does not include
       an IEEE 802.1AR factory installed credential.

   3.  The registrar MAY request nonce-less Audit Tokens from the MASA
       service.  These tokens can then be transmitted to the Registrar
       and stored until they are needed during bootstrapping operations.
       This is for use cases where target network is protected by an air
       gap and therefore can not contact the MASA service during New
       Entity deployment.

   4.  The registrar MAY ignore unrecognized nonce-less Audit Log
       entries.  This could occur when used equipment is purchased with



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       a valid history being deployed in air gap networks that required
       permanent Audit Tokens.

   These modes are not available for devices that require a vendor
   Ownership Voucher.  The methods vendors use to determine which
   devices are owned by which domains is out-of-scope.

6.4.  MASA security reductions

   Lower security modes chosen by the MASA service effect 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 Audit Token.  This results
       in distribution of Audit Tokens that never expire and in effect
       makes the Domain an always trusted entity to the New Entity
       during any subsequent bootstrapping attempts.  That this occurred
       is captured in the log information so that the Domain registrar
       can make appropriate security decisions when a New Entity joins
       the Domain.  This is useful to support use cases where Registrars
       might not be online during actual device deployment.  Because
       this results in long lived Audit Tokens and do not require the
       proof that the device is online this is only accepted when the
       Registrar is authenticated by the MASA server and authorized to
       provide this functionality.  The MASA server is RECOMMENDED to
       use this functionality only in concert with Ownership Validation
       tracking.

   2.  Not verifying ownership before responding with an Audit Token.
       This is expected to be a common operational model because doing
       so relieves the vendor providing MASA services from having to
       tracking ownership during shipping and supply chain and allows
       for a very low overhead MASA service.  The 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).

7.  Security Considerations

   In order to support a wide variety of use cases, devices can be
   claimed by a registrar without proving possession of the device in
   question.  This would result in a nonceless, and thus always valid,
   claim.  Or would result in an invalid nonce being associated with a
   claim.  The MASA service is required to authenticate such Registrars
   but no programmatic method is provided to ensure good behavior by the



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   MASA service.  Nonceless entries into the audit log therefore
   permanently reduce the value of a device because future Registrars,
   during future bootstrap attempts, would now have to be configured
   with policy to ignore previously (and potentially unknown) domains.

   Future registrars are recommended to take the audit history of a
   device into account when deciding to join such devices into their
   network.  If the MASA server were to have allowed a significantly
   large number of claims this might become onerous to the MASA server
   which must maintain all the extra log entries.  Ensuring the
   Registrar is representative of a valid customer domain even without
   validating ownership helps to mitigate this.

   It is possible for an attacker to send an authorization request to
   the MASA service directly after the real Registrar obtains an
   authorization log.  If the attacker could also force the
   bootstrapping protocol to reset there is a theoretical opportunity
   for the attacker to use the Audit Token to take control of the New
   Entity but then proceed to enroll with the target domain.  Possible
   prevention mechanisms include:

   o  Per device rate limits on the MASA service ensure such timing
      attacks are difficult.

   o  In the advent of an unexpectedly lost bootstrapping connection the
      Registrar repeats the request for audit log information.

   As indicated in EST [RFC7030] the connection is provisional and
   untrusted until the server is successfully authorized.  If the server
   provides a redirect response the client MUST follow the redirect but
   the connection remains provisional.  If the client uses a well known
   URI for contacting a well known Registrar the EST Implicit Trust
   Anchor database is used as is described in RFC6125 to authenticate
   the well known URI.  In this case the connection is not provisional
   and RFC6125 methods can be used for each subsequent redirection.

   The MASA service could lock a claim and refuse to issue a new token
   or the MASA service could go offline (for example if a vendor went
   out of business).  This functionality provides benefits such as theft
   resistance, but it also implies an operational risk to the Domain
   that Vendor behavior could limit future bootstrapping of the device
   by the Domain.  This can be mitigated by Registrars that request
   nonce-less authorization tokens.








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8.  Acknowledgements

   We would like to thank the various reviewers for their input, in
   particular Markus Stenberg, Brian Carpenter, Fuyu Eleven.

9.  References

9.1.  Normative References

   [IDevID]   IEEE Standard, , "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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3542]  Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
              "Advanced Sockets Application Program Interface (API) for
              IPv6", RFC 3542, May 2003.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927, May
              2005.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC5386]  Williams, N. and M. Richardson, "Better-Than-Nothing
              Security: An Unauthenticated Mode of IPsec", RFC 5386,
              November 2008.

   [RFC5660]  Williams, N., "IPsec Channels: Connection Latching",
              RFC 5660, October 2009.

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

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <http://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,
              <http://www.rfc-editor.org/info/rfc7030>.



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

9.2.  Informative References

   [I-D.behringer-homenet-trust-bootstrap]
              Behringer, M., Pritikin, M., and S. Bjarnason,
              "Bootstrapping Trust on a Homenet", draft-behringer-
              homenet-trust-bootstrap-02 (work in progress), February
              2014.

   [I-D.ietf-ace-actors]
              Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
              architecture for authorization in constrained
              environments", draft-ietf-ace-actors-03 (work in
              progress), March 2016.

   [I-D.ietf-netconf-zerotouch]
              Watsen, K. and M. Abrahamsson, "Zero Touch Provisioning
              for NETCONF or RESTCONF based Management", draft-ietf-
              netconf-zerotouch-07 (work in progress), March 2016.

   [I-D.irtf-nmrg-autonomic-network-definitions]
              Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking - Definitions and Design Goals", draft-irtf-
              nmrg-autonomic-network-definitions-07 (work in progress),
              March 2015.

   [I-D.lear-mud-framework]
              Lear, E., "Manufacturer Usage Description Framework",
              draft-lear-mud-framework-00 (work in progress), January
              2016.

   [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-00 (work in progress), January 2016.

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

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




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Authors' Addresses

   Max Pritikin
   Cisco

   Email: pritikin@cisco.com


   Michael C. Richardson
   Sandelman Software Works
   470 Dawson Avenue
   Ottawa, ON  K1Z 5V7
   CA

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


   Michael H. Behringer
   Cisco

   Email: mbehring@cisco.com


   Steinthor Bjarnason
   Cisco

   Email: sbjarnas@cisco.com























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