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Versions: 00 01 draft-pritikin-anima-bootstrapping-keyinfra

Network Working Group                                        M. Pritikin
Internet-Draft                                              M. Behringer
Intended status: Informational                              S. Bjarnason
Expires: March 30, 2015                                            Cisco
                                                      September 26, 2014


                   Bootstrapping Key Infrastructures
           draft-pritikin-bootstrapping-keyinfrastructures-01

Abstract

   This document specifies automated bootstrapping of an key
   infrastructure using vendor installed IEEE 802.1AR manufacturing
   installed certificates, in combination with a vendor based cloud
   service.  Before being authenticated, a new device has only link-
   local connectivity, and does not require a routable address.  When a
   vendor cloud service is provided devices can be forced to join only
   specific domains but for contrained 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 March 30, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (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



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   4
   3.  Operational Overview  . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Instantiating the Domain Certification Authority  . . . .   7
     3.2.  Instantiating the Registrar . . . . . . . . . . . . . . .   7
     3.3.  Accepting New Entities  . . . . . . . . . . . . . . . . .   7
     3.4.  Operating the Network . . . . . . . . . . . . . . . . . .   8
   4.  Functional Overview . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Behavior of a new entity  . . . . . . . . . . . . . . . .   9
       4.1.1.  Proxy Discovery . . . . . . . . . . . . . . . . . . .  10
       4.1.2.  Receiving and accepting the Domain Identity . . . . .  11
       4.1.3.  Enrollment  . . . . . . . . . . . . . . . . . . . . .  12
       4.1.4.  After Enrollment  . . . . . . . . . . . . . . . . . .  12
     4.2.  Behavior of a proxy . . . . . . . . . . . . . . . . . . .  12
     4.3.  Behavior of the Registrar . . . . . . . . . . . . . . . .  13
       4.3.1.  Authenticating the Device . . . . . . . . . . . . . .  13
       4.3.2.  Accepting the Entity  . . . . . . . . . . . . . . . .  13
       4.3.3.  Claiming the new entity . . . . . . . . . . . . . . .  14
     4.4.  Behavior of the MASA Cloud Service  . . . . . . . . . . .  14
       4.4.1.  Issue Authorization Token and Log the event . . . . .  14
       4.4.2.  Retrieve Audit Entries from Log . . . . . . . . . . .  15
     4.5.  Leveraging the new key infrastructure / next steps  . . .  15
       4.5.1.  Network boundaries  . . . . . . . . . . . . . . . . .  15
   5.  Protocol Details  . . . . . . . . . . . . . . . . . . . . . .  15
     5.1.  EAP-EST . . . . . . . . . . . . . . . . . . . . . . . . .  16
     5.2.  Request bootstrap token . . . . . . . . . . . . . . . . .  16
     5.3.  Request MASA authorization token  . . . . . . . . . . . .  17
     5.4.  Request MASA authorization log  . . . . . . . . . . . . .  17
   6.  Reduced security operational modes  . . . . . . . . . . . . .  18
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  19
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

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



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   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 cloud service.

   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 an established key infrastructure(s).  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 trusted third-party.  The new entity's
   decisions are made according to verified communication with a trusted
   third-party or in a strictly auditable fasion.

   Optimal security is achieved with IEEE 802.1AR certificates on each
   new entity, accompanied by a third-party cloud service for
   verification.  The concept also works with less requirements, but is
   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 communiciations with a cloud service,
   which is itself authenticated using HTTPS, bootstrapping of a domain
   specific Public Key Infrastructure (PKI) is fully described.



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   Sufficient agility to support bootstrapping alternative key
   infrastructures (such as symmetric key solutions) is considered
   although no such 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:

2.  Architectural Overview

   The logical elements of the bootstrapping framework are described in
   this section.  Figure 1 provides a simplified overview of the
   components.  Each component is logical and may be combined with other
   components as necessary.
































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                                                 Factory components
                                                        .
                                                        . +------------+
                                                        . | Factory CA |
                                                        . +------------+
                                                        .        |
                                                        . +------------+
                                                        . |            |
      +--------------(provides)---------------------------|  Factory   |
      |                                       +---------->|            |
      |                                       |         . +------------+
      |                                       V         .
      |                              +---------------+  . +------------+
      |                              | Orchestrator  |  . | MASA       |
      V                              +---------------+  . | Cloud      |
   +-------+                                  |         . | Service    |
   | New   |        +------------+       +-----------+  . +------------+
   | Entity|<--L2-->|    Proxy   |<----->|           |  .......  ^
   |       |        +------------+       |           |           |
   |       |                             | Registrar |           |
   |       |                             |           |           |
   |       |<--DHCP-->(L3 bootstrap)     |           |           |
   |       |                             |           |           |
   |       |<-----L3---------------------( registrar )-----------+
   |       |                             ( may proxy )        |
   +-------+                             +-----------+
                                                   |
                             +----------------------------+
                    ^        |  Domain Certification      | ^
                    .        |      Authority             | .
                    .        +----------------------------+ .
                    .                                       .
                    .........................................
                                      |
                              "domain" components




   Figure 1

   Domain:  The set of entities that trust a common key infrastructure
      trust anchor.

   Domain CA:  The domain Certification Authority (CA) optionally
      provides certification functionalities to the domain entities.  At
      a minimum it provides certification funtionalities to the
      Registrar and stores the trust anchor that defines the domain.



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   Domain Identity:  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 colloqually used as a humanized identity value but
      during protocol discussions the more exact term as defined here is
      used).

   Orchestrator:  Although bootstrapping of an individual device is
      automated and requires zero administrative involvement
      (particularly on the New Entity) the orchestrator drives general
      operations of the domain.  In simple deployments this might be a
      single administrator ordering a new device from the Factory and
      manually inputing a serial number from the bill-of-sale into a
      Registrar.  In a more complex environment this might be an
      automated process that directs a hypervisor "Factory" to
      instantiate a new virtual machine.

   Factory:  This instantiates the New Entity.  For physical devices
      this can be representative of third-party vendor manufacturing,
      ordering and shipping process(es) that results in a physical
      hardware device with an IEEE 802.1AR identity being drop shipped
      to a destination domain for physical installation.  In a virtual
      machine environment this can be the virtual machine hypervisor
      control software that initiates a virtual machine instance, in
      which case the factory is a "virtual factory" and might be managed
      by the domain itself.

   Factory CA:  This Certification Authority is leveraged by the Factory
      to issue IEEE 802.1AR identities to each New Entity.  For a
      virtual factory it may be reasonable to assume the domain
      certification authority is directly used but in a complex
      environment it is assumed the Factory does not have direct access
      to the Domain Certification Authority.

   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.

   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




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      in an environment where they are not provided L3 connectivity
      until after they are validated as members of the domain.

   MASA Cloud Service:  A Manufacturer Authorized Signing Authority
      (MASA) cloud service on the global Internet.  At a minimum the
      MASA provides a trusted repository for audit information
      concerning privacy protected bootstrapping events.  As a service
      offering the MASA can encorporate many of the bootstrapping
      elements (such as the Registrar and the Domain CA) into the cloud
      service.

3.  Operational Overview

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

3.1.  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.

3.2.  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.  An automated Registrar selection
   processes is not detailed here.  [[EDNOTE: yet]]

3.3.  Accepting New Entities

   For each New Entity the Registrar is informed a priori the unique
   identifier (e.g. serial number).  This can be supplied automatically
   from the Orchestrator [[EDNOTE: TBD]] or inputed manually by the
   administrator.

   For each entity that will be accepted a Registrar maintains the
   Factory CA identity and the entity's unique identifier.  The Factory
   CA identity could be implemented as the Factory CA root certificate
   keyIdentifier (the 160-bit SHA-1 hash of the value of the BIT STRING
   subjectPublicKey).  For user interface purposes the keyIdentifier



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   information can be mapped to a colloquial Factory name (Registrars
   can be shipped with the keyIdentifier of a significant number of
   third-party manufacturers).

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

3.4.  Operating the Network

   Once devices are enrolled to the domain, the network operator can
   specify a policy, or otherwise configure the devices if required.
   This is outside scope for this document.

4.  Functional Overview

   Entities behave in an autonomic fashion.  They discover each other
   and autonomically establish a key infrastructure deliminating the
   autonomic domain.  See [I-D.behringer-autonomic-network-framework]
   for more information.

   The overall flow is shown in Figure 2:





























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   +---------+                +----------+                +-----------+
   |  New    |                |          |                |  Factory  |
   | Entity  |                |  Domain  |                |   Cloud   |
   |         |                |          |                |  Service  |
   +---------+                +----------+                +-----------+
       |                           |                            |
       |<-------discovery--------->|                            |
       |---802.1AR credential----->|                            |
       |                           |                            |
       |                    [ accept device? ]                  |
       |                           |                            |
       |                           |---802.1AR identity-------->|
       |                           |---Domain ID--------------->|
       |                           |                            |
       |                           |                    [device belongs]
       |                           |                    [to domain?    ]
       |                           |                            |
       |                           |                  [update audit log]
       |                           |                            |
       |                           |<---device history log------|
       |                           |<-- authorization token-----|
       |                           |                            |
       |                  [ still accept device?]               |
       |                           |                            |
       |<----authorization token---|                            |
       |<----domain information----|                            |
       |                           |                            |
  [auth token valid?]              |                            |
       |                           |                            |
       |----domain enrolment------>|                            |
       |<----domain certificate----|                            |
       |                           |


4.1.  Behavior of a new entity

   A New Entity that has not yet been bootstrapped attempts to find a
   local domain and join it.  A number of methods are attempted for
   establishing communications with the domain in a specified order.

   Client behavior is as follows:

   1.  Discover a communication channel to the "closest" Registrar by
       trying the following steps in this order:

       A.  Search for a Proxy on the local link using Neighbor
           Discovery.  If multiple local proxies are discovered attempt




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           communications with each before widening the search to other
           options.  If this fails:

       B.  Obtain an IP address using DHCP, and search for a local
           registrar using DNS service discovery.  If this fails:

       C.  Obtain an IP address using DHCP, and search for a pre-defined
           Factory provided global registrar using DNS.

   2.  Present IEEE 802.1AR credentials to the discovered Registrar (via
       a Proxy if necessary).  Included is a generated nonce that is
       specific to this attempt.

   3.  Verify the MASA cloud service generated authorization token as
       provided by the contacted Registrar.  The nonce information
       previously provided is also checked, if it was not removed by the
       Registrar.

   4.  If and only if step three is successful: Join Domain, by
       accepting the domain specific information from the registrar, and
       by enrolling a domain certificate from the registrar.

   5.  The New Entity is now a member of the domain and will only repeat
       the discovery aspects of bootstrapping if it is returned to
       factory default settings.

   [[EDNOTE: Step (1b and 1c) is similar to the vendor DNS mechanisms
   described in draft-kwatsen-netconf-zerotouch although the goal here
   is to contact a Registrar rather than a vendor supplied NMS]

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

4.1.1.  Proxy Discovery

   Existing protocols provide the appropriate functionality for both
   discovering the Proxy and facilitating communication through the
   Proxy:

   IEEE 802.1X  Where the New Entity can be cast as the "supplicant" and
      the Proxy is the "authenticator".  The bootstrapping protocol
      messages are encapsulated as EAP methods.  The "authenticator"
      reencapsulates the EAPOL frames and forwards them to the
      "Authentication Server", which provides Registrar functionalities.

   PANA [RFC5191]  [[EDNOTE: TBD]]

   ND [RFC2461] / [RFC4861]  [[EDNOTE: TBD]] NOTE: Neighbor Discovery
      protocols do not describe a mechanism for forwarding messages.



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   Each provides a method for the New Entity to discover and initiate
   communication with a local neighbor.  In each protocol methods are
   available to support encapsulation of the bootstrapping protocol
   messages described elsewhere in this document.  Other protocols for
   transporting bootstrapping messages can be added in future
   references.

   All security assocaitions established are between the new device and
   the Registrar regardless of proxy operations.

   If multiple proxies are available the New Entity tries each until a
   successful bootstrapping occurs.  The New Entity may prioritize
   proxies selection order as appropriate for the anticipated
   environment.

   If Proxy discovery fails the New Entity moves on to discovering a
   Registrar directly.

4.1.2.  Receiving and accepting the Domain Identity

   The domain trust anchor is received by the New Entity during the
   boostrapping protocol exchange.

   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  and using a configured Explicit TA database (not an autonomic
      solution because the distribution of symmetric key material is not
      autonomic).

   This document describes two additional autonomic methods:

   MASA authorization token  Authorization tokens are obtained by the
      Registrar from the MASA cloud service and presented to the New
      Entity for validation.

   URL redirect  If the New Entity discovers a well known global
      registrar using DNS then the EST protocol exchange is protected
      using an Implicit TA database, but also the MASA authorization is
      required.  The global registrar MUST claim the device with the
      MASA server to ensure the logging information is consistent.  The



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      global registrar forwards the New Entity to an alternate URI as
      described in EST [RFC7030].

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

   [[EDNOTE: move protocol discussion down into protocol section]] The
   domain trust anchor MUST be included in the TLS handshake Server
   Certificate "certificate_list" [RFC5246] or the client MUST request
   the EST Bootstrap Distribution of CA Certificates [RFC7030].  (This
   document defines an additional method for accepting the CA
   certificates).

4.1.3.  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 primarly 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
      [[EDNOTE: or in the non-autonomic case using the the out of band
      secret].

   o  The EST section 4.1.3 CA Certificates Response is verified using
      the MASA authorization token provided domain identity.

4.1.4.  After Enrollment

   Functionality to provide generic "configuration" 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.

   See Section 4.5.

4.2.  Behavior of a proxy

   The role of the Proxy is to facilitate communications.  The Proxy
   forwards messages between the New Entity and a Registrar.  Where
   existing protocols as detailed in Section 4.1.1 already provide this
   functionality nothing additional is defined.




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   [[EDNOTE: If neighbor discovery protocols are used for Proxy
   discovery then a proxy forwarding protocol is to be defined here]]

4.3.  Behavior of the Registrar

   One 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:

4.3.1.  Authenticating the Device

   The 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).

4.3.2.  Accepting the Entity

   In a fully automated nework all devices must be securely identified.

   A Registrar accepts or declines a request to join the domain, based
   on the authenticated identity presented and other policy defined
   criteria such as Proxy identity.  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 Factory (as determined by the
      IEEE 802.1AR identity),

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

   In all cases a Registrar must use the globally available MASA cloud
   service to verify the device's history log does not include
   unexpected Registrars.

   If a device is accepted into the domain, it is then invited to
   request a domain certificate through a certificate enrolment 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



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   other domain nodes, and to autonomically enable services on the
   homenet.

4.3.3.  Claiming the new entity

   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 cloud
   service.  If a nonce is provided by the Registrar then claims from an
   unauthenticated Registrar are serviced by the MASA cloud resource.

   The Registrar can claim a New Entity that is not online by forming
   the request using the entities unique identifier but not including a
   nonce in the claim request.  MASA authorization 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 cloud service.

   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 4.1.2 a New Entity will only proceed with
   bootstrapping if a validated MASA authorization token has been
   recieved.  The New Entity therefore enforces that bootstrapping only
   occurs if the claim has been logged.

4.4.  Behavior of the MASA Cloud Service

   The cloud service is provided by the Factory provider.  The URI of
   the cloud service is well known.  The URI should be provided as an
   IEEE 802.1AR IDevID X.509 extension (a "MASA authorization token
   Distribution Point" extension).

   The cloud service provides the following functionalities to
   Registrars:

4.4.1.  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 cloud service responds to all
   requests.  The MASA cloud service verifies the Registrar is
   representative of the domain and generates a privacy protected log
   entry before responding with the authorization token.



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   If a nonce is not provided the MASA cloud service MUST authenticate
   the Registrar as a valid customer.  This prevents denial of service
   attacks.  The specific level of authentication provided by the
   customer is not defined here.  An MASA Practice Statement (MPS)
   similar to the Certification Authority CPS, as defined in RFC5280, is
   provided by the Factory such that Registrar's can determine the level
   of trust they have in the Factory.

4.4.2.  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 cloud
   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.

4.5.  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.

4.5.1.  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.

5.  Protocol Details

   The bootstrapping protocol is an extension of EST [RFC7030].

   [[EDNOTE: Insert figure here]]

   EST provides a bootstrapping mechanism for new entities that are
   configured with the URI of the EST server or new entities that can



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   "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.  [[EDNOTE: This
   paragraph should be expanded to provide a detailed discussion of
   current EST functionalitites, or do we assume the reader follows the
   normative reference?]].

   The following additions provide for fully automated functionality.
   EST is extended by defining additional HTTP URIs and messages
   specific to bootstrapping.  These are 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.

5.1.  EAP-EST

   In order to support Proxy environments EAP-EST is defined.

   [[EDNOTE: TBD.  EST is TLS with some data.  EAP-TLS and other similar
   protocols provide an example framework for filling out this section]]

5.2.  Request bootstrap 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
   "/requestbootstraptoken".

   The request format is a raw nonce value.  [[EDNOTE: exact format TBD.
   There is an advantage to having the client sign the nonce (similar to
   a PKI Certification Signing Request) since this allows the MASA cloud
   service to confirm the actual device identity.  It is not clear that
   there is a security benefit from this.]]

   The Registrar validates the client identity as described in EST
   [RFC7030] section 3.3.2.  The registrar performs authorization as
   detailed in Section 4.3.2.  If authorization is successful the
   Registrar obtains a MASA authorization token from the MASA cloud
   service (see Section 5.3).

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

   [[EDNOTE: update to CMS language]]




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5.3.  Request MASA authorization token

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

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

   The request format is an optional raw 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).  This
   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, is included in the PKCS7.

   The MASA cloud service checks the internal consistency of the PKCS7
   but is unable to actually 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 verifies
   that the PKCS7 is signed by a Registrar (by checking for the cmc-idRA
   field in the Registrar certificate) certificate that was issued by
   the root certificate included in the PKCS7.

   The domain ID is extracted from the root certificate and is used to
   generate the MASA authorization token and to update the audit log.

   [[EDNOTE: update to CMS language]]

5.4.  Request MASA authorization log

   A registrar requests the MASA authorization log from the cloud
   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 each log entry.  The
   data in each entry includes:

   o  date/time of the entry

   o  domain ID (this is just a hash of the public key information and
      is thus privacy protected)

   o  nonce value

   [[EDNOTE: exact format TBD]]



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6.  Reduced security operational modes

   A common requirement of bootstrapping infrastructures is often that
   they support less secure operational modes.  To support these
   operational modes the Registrar can choose to accept devices using
   less secure methods.  For example:

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

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

   3.  A representative of the Registar (e.g. the Orchestrator) may
       request nonce-less authorization tokens from the MASA cloud
       service when network connectivity is available.  These tokens can
       then be transmitted to the Registrar and stored until they are
       needed during bootstrapping operations.  Ths may occur when: The
       target network is protected by an air gap and therefore can not
       contact the MASA cloud service during New Entity deployment.

   4.  The device may have an operational mode where it skips
       authorization token validation.  For example if a physical button
       is depressed during the bootstrapping operation.  This may occur
       when: A device Factory goes out of business or otherwise fails to
       provide a reliable MASA cloud service.

   5.  The device may not require the MASA cloud service authorization
       token.  An entity that does not validate the domain identity is
       inherently dangerous as it may contain malware.  This risk should
       be mitigated using attestation and measurement technologies.  In
       order to support an unsecured imprint the New Entity MUST support
       remote attestation technologies such as is defined by the Trusted
       Computing Group.  [[EDNOTE: How to include remote attestation
       into the boostrapping protocol exchange is TBD]].  This may occur
       when: The device Factory does not provide a MASA cloud service.

7.  Security Considerations

   In order to support a 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.  The
   MASA cloud service is required to authenticate such Registrars but no
   programatic method is provided to ensure good behavior by the MASA



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   cloud service.  Nonceless entries into the audit log therefore
   permanently reduce the value of a device because future Registrars,
   during future bootstrap attempts, must now 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.

   It is possible for an attacker to send an authorization request to
   the MASA cloud 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 authorization token to take control of
   the New Entity but then proceed to enrol with the target domain.  To
   prevent this the MASA cloud service is rate limited to only generate
   authorization tokens at a rate of 1 per minute.  The Registrar
   therefore has at least 1 minute to get the response back to the New
   Entity.  [[EDNOTE: a better solution can likely be found.  This text
   captures the issue for now.]] Also the Registar can double check the
   log information after enrolling the New Entity.

   The MASA cloud service could lock a claim and refuse to issue a new
   token.  Or the MASA cloud 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.
   This can be mitigated by Registrars that request nonce-less
   authorization tokens.

8.  References

8.1.  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, March 1997.

   [RFC7030]  Pritikin, M., Yee, P., and D. Harkins, "Enrollment over
              Secure Transport", RFC 7030, October 2013.

8.2.  Informative References







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   [I-D.behringer-autonomic-network-framework]
              Behringer, M., Pritikin, M., Bjarnason, S., and A. Clemm,
              "A Framework for Autonomic Networking", draft-behringer-
              autonomic-network-framework-01 (work in progress), October
              2013.

Authors' Addresses

   Max Pritikin
   Cisco

   Email: pritikin@cisco.com


   Michael H. Behringer
   Cisco

   Email: mbehring@cisco.com


   Steinthor Bjarnason
   Cisco

   Email: sbjarnas@cisco.com



























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