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Versions: 00

Network Working Group                                            E. Lear
Internet-Draft                                                  O. Friel
Intended status: Standards Track                           N. Cam-Winget
Expires: December 31, 2018                                 Cisco Systems
                                                           June 29, 2018


               Bootstrapping Key Infrastructure over EAP
                      draft-lear-eap-teap-brski-00

Abstract

   In certain environments, in order for a device to establish any layer
   three communications, it is necessary for that device to be properly
   credentialed.  This is a relatively easy problem to solve when a
   device is associated with a human being and has both input and
   display functions.  It is less easy when the human, input, and
   display functions are not present.  To address this case, this memo
   specifies extensions to the Tunnel Extensible Authentication Protocol
   (TEAP) method that leverages Bootstrapping Remote Secure Key
   Infrastructures (BRSKI) in order to provide a credential to a device
   at layer two.

Status of This Memo

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

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

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

   This Internet-Draft will expire on December 31, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  TEAP BRSKI Architecture . . . . . . . . . . . . . . . . . . .   3
   3.  BRSKI Bootstrap and Enroll Operation  . . . . . . . . . . . .   4
     3.1.  Executing BRSKI in a TEAP Tunnel  . . . . . . . . . . . .   5
   4.  PKI Certificate Authority Considerations  . . . . . . . . . .   8
     4.1.  TEAP Tunnel Establishment . . . . . . . . . . . . . . . .   8
     4.2.  BRSKI Trust Establishment . . . . . . . . . . . . . . . .   9
   5.  Channel and Crypto Binding  . . . . . . . . . . . . . . . . .  10
   6.  Protocol Flows  . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  TEAP Server Grants Access . . . . . . . . . . . . . . . .  11
     6.2.  TEAP Server Instructs Client to Perform BRSKI Flow  . . .  12
     6.3.  TEAP Server Instructs Client to Reenroll  . . . . . . . .  13
     6.4.  Out of Band Reenroll  . . . . . . . . . . . . . . . . . .  14
   7.  TEAP TLV Formats  . . . . . . . . . . . . . . . . . . . . . .  15
     7.1.  BRSKI TLVs  . . . . . . . . . . . . . . . . . . . . . . .  15
       7.1.1.  BRSKI-RequestVoucher TLV  . . . . . . . . . . . . . .  15
       7.1.2.  BRSKI-Voucher TLV . . . . . . . . . . . . . . . . . .  15
       7.1.3.  BRSKI-VoucherStatus TLV . . . . . . . . . . . . . . .  15
       7.1.4.  EnrollmentStatus TLV  . . . . . . . . . . . . . . . .  15
       7.1.5.  CSR-Attributes TLV  . . . . . . . . . . . . . . . . .  15
     7.2.  Existing TEAP TLV Specifications  . . . . . . . . . . . .  15
       7.2.1.  PKCS#10 TLV . . . . . . . . . . . . . . . . . . . . .  16
   8.  Fragmentation . . . . . . . . . . . . . . . . . . . . . . . .  16
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  16
   12. Informative References  . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  Changes from Earlier Versions  . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   [I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) specifies a means to
   provision credentials to be used as credentials to operationally
   access networks.  It was designed as a standalone means where some
   limited access to an IP network is already available.  This is not
   always the case.  For example, IEEE 802.11 networks generally require
   authentication prior to any form of address assignment.  While it is



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   possible to assign an IP address to a device on some form of an open
   network, or to accept some sort of default credential to establish
   initial IP connectivity, the steps that would then follow might well
   require that the device is placed on a new network, requiring
   reseting all layer three parameters.

   A more natural approach in such cases is to more tightly bind the
   provisioning of credentials with the authentication mechanism.  One
   such way to do this is to make use of the Extensible Authentication
   Protocol (EAP) [RFC3748] and the Tunnel Extensible Authentication
   Protocol (TEAP) method [RFC7170].  Thus we define new TEAP Type-
   Length-Value (TLV) objects that can be used to transport the BRSKI
   protocol messages within the context of a TEAP TLS tunnel.

   [RFC7170] discusses the notion of provisioning peers.  Several
   different mechanisms are available.  Section 3.8 of that document
   acknowledges the concept of not initially authenticating the outer
   TLS session so that provisioning may occur.  In addition, exchange of
   multiple TLV messages between client and EAP server permits multiple
   provisioning steps.

1.1.  Terminology

   The reader is presumed to be familiar with EAP terminology as stated
   in [RFC3748].  In addition, the following terms are commonly used in
   this document.

   o  BRSKI: Bootstrapping Remote Secure Key Infrastructures, as defined
      in [I-D.ietf-anima-bootstrapping-keyinfra].  The term is also used
      to refer to the flow described in that document.

   o  EST: Enrollment over Secure Transport, as defined in [RFC7030].

   o  voucher: a signed json object as defined in [RFC8366].

2.  TEAP BRSKI Architecture

   The TEAP BRSKI architecture is illustrated in Section 3.  The device
   talks to the TEAP server via the Authenticator as per any normal EAP
   exchange.  There is no need for an inner EAP method server, and there
   is no explicit EAP method type defined for BRSKI.

   The architecture illustrated shows the TEAP server and Registrar
   function as being two logically separate entities, however the BRSKI
   Registrar functionality may be integrated into the TEAP server.  The
   device is not explicitly aware of where the Registrar functionality
   is deployed when executing BRSKI inside a TEAP tunnel.  Note that the
   device may connect directly to the Registrar for the purposes of



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   certificate reenrollment, but this happens outside the context to
   801.1X and TEAP authentication.

   The Registrar in turn communicates with the BRSKI MASA service for
   the purposes of getting signed vouchers.  [[TODO: I guess we should
   mention TEAP server talking to vendor default Registrar in the
   cloud]]

   The Registrar also comunicates with a Certificate Authority in order
   to issue LDevIDs.  The architecture shows the Registrar and CA as
   being two logically separate entities, however the CA may be
   integrated into the Registrar.  The device is not explicitly aware of
   whether the CA and Registrar functions are integrated.

  +--------+     +---------+     +--------+     +---------+     +------+
  |        |     |         |     |        |     |         |<--->| MASA |
  |        |     | Authen- |     |  TEAP  |     | BRSKI   |     +------+
  | Device |<--->| ticator |<--->| server |<--->|Registrar|
  |        |     |         |     |        |     |         |     +------+
  |        |     |         |     |        |     |         |<--->|  CA  |
  +--------+     +---------+     +--------+     +---------+     +------+


3.  BRSKI Bootstrap and Enroll Operation

   This section summarises the current BRSKI operation.  The BRSKI flow
   assumes the device has an IDevID and has a manufacturer installed
   trust anchor that can be used to validate the BRSKI voucher.  The
   BRSKI flow compromises serveral main steps from the perspective of
   the device:

   o  Step 1: Device discovers the Registrar

   o  Step 2: Device establishes provisional TLS connection to Registrar

   o  Step 3: Device sends voucher request message and receives signed
      voucher response

   o  Step 4: Device validates voucher and validates provisional TLS
      connection to Registrar

   o  Step 5: Device sends Voucher Status Telemetry message

   o  Step 6: Device downloads additional local domain CA information

   o  Step 7: Device downloads Certificate Signing Reqeust (CSR)
      attributes




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   o  Step 8: Device does an EST enroll to obtain an LDevID

   o  Step 9: Device sends Enrollment Status Telemetry message

   o  Step 10: Device periodically reenrolls via EST to refresh its
      LDevID

   Most of the operational steps require the device, and thus its
   internal state machine, to automatically complete the next step
   without being explicitly instructed to do so by the Registrar.  For
   example, the Registrar does not explicitly tell the device to
   download additional local domain CA information, or to do an EST
   enroll to obtain an LDevID.

3.1.  Executing BRSKI in a TEAP Tunnel

   This section outlines how the main BRSKI steps outlined above map to
   TEAP, and how BRSKI and enrollment can be accomplished inside a TEAP
   TLS tunnel.  The following new TEAP TLVs are introduced:

   o  BRSKI-VoucherRequest

   o  BRSKI-Voucher

   o  BRSKI-VoucherStatus

   o  EnrollmentStatus

   o  CSR-Attributes

   The following steps outline how the above BRSKI flow maps to TEAP.

   o  Step 1: Device discovers the Registrar

   When BRSKI is executed in a TEAP tunnel, the device exchanges BRSKI
   TLVs with the TEAP server.  The discovery process for devices is
   therefore the standard wired or wireless LAN EAP server discovery
   process.  The discovery processes outlined in section 4 of
   [I-D.ietf-anima-bootstrapping-keyinfra] are not required for initial
   discovery of the Registrar.

   o  Step 2: Device establishes provisional TLS connection to Registrar

   The device establishes an outer TEAP tunnel with the TEAP server and
   does not validate the server certificate.  The device presents its
   LDevID as its identity certificate if it has a valid LDevID,
   otherwise it presents its IDevID.  Server policy may also be used to




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   control which certificate the device is allowed present, as described
   in section Section 4.

   If the presented credential is sufficient to grant access, the TEAP
   server can return an EAP-Success immediately.  The device may still
   send a BRSKI-RequestVoucher TLV in response to the EAP-Success if it
   does not have, but requires, trust anchors for validating the TEAP
   server certificate.

   If the TEAP server requires that the device execute a BRSKI flow, it
   sends a Request-Action TLV that includes a BRSKI-VoucherRequest TLV.
   For example, if the device presented its IDevID but the TEAP server
   requires an LDevID.

   The TEAP server may also require the device to reenroll, for example,
   if the device presented a valid LDevID that is very closed to
   expiration.  The server may instruct a device to reenroll by sending
   a Request-Action TLV that includes a zero byte length PKCS#10 TLV.

   o  Step 3: Device sends voucher request message and receives signed
      voucher response

   The device sends a BRSKI-RequestVoucher TLV to the TEAP server.  The
   TEAP server forwards the RequestVoucher message to the MASA server,
   and the MASA server replies with a signed voucher.  The TEAP server
   sends a BRSKI-Voucher TLV to the device.

   If the MASA server does not issue a signed voucher, the TEAP server
   sends an EAP-Error TLV with a suitable error code to the device.

   o  Step 4: Device validates voucher and validates provisional TLS
      connection to Registrar

   The device validates the signed voucher using its manufacturer
   installed trust anchor, and uses the CA information in the voucher to
   validate the outer TEAP TLS connection to the TEAP server.

   If the device fails to validate the voucher, or fails to validate the
   outer TEAP TLS connection, then it sends a BRSKI-VoucherStatus TLV
   indicating failure to the TEAP server.

   o  Step 5: Device sends Voucher Status Telemetry message

   On successfully validating the voucher and outer TEAP TLS connection,
   the device sends a BRSKI-VoucherStatus TLV to the TEAP server.

   Once step 5 is complete, the device has completed the BRSKI flow and
   has established trust with the network.



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   o  Step 6: Device downloads additional local domain CA information

   On completion of the BRSKI flow, the device SHOULD send a Trusted-
   Server-Root TLV to the TEAP server in order to discover additional
   local domain CAs.

   o  Step 7: Device downloads CSR attributes

   On completion of step 6, the device MUST send a CSR-Attributes TLV to
   the TEAP server in order to discover the correct fields to include
   when it enrolls to get an LDevID.

   o  Step 8: Device does an EST enroll to obtain an LDevID

   When executing the BRSKI flow inside a TEAP tunnel, the device does
   not directly leverage EST when doing its initial enroll.  Instead,
   the device uses the existing TEAP PKCS#10 and PCKS#7 TEAP mechanisms.

   Once the BRSKI flow is complete, the device can now send a PKCS#10
   TLV to enroll and request an LDevID.  If the TEAP server instructed
   the device to start the BRSKI flow via a Request-Action TLV that
   includes a BRSKI-RequestVoucher TLV, then the device MUST send a
   PKCS#10 in order to start the enroll process.  The TEAP server will
   handle the PKCS#10 and ultimately return a PKCS#7 including an LDevID
   to the device.

   If the TEAP server granted the device access on completion of the
   outer TEAP TLS tunnel in step 2 without sending a Request-Action TLV,
   the device does not have to send a PKCS#10 to enroll.

   o  Step 9: Device sends Enrollment Status Telemetry message

   On completion of certificate enrollment, the device sends an
   EnrollmentStatus TLV to the TEAP server.

   o  Step 10: Device periodically reenrolls to refresh its LDevID

   When a device's LDevID is close to expiration, there are two options
   for re-enrollment in order to obtain a fresh LDevID.  As outlined in
   Step 2 above, the TEAP server may instruct the device to reenroll by
   sending a Request-Action TLV including a PKCS#10 TLV.  If the TEAP
   server explicilty instructs the device to reenroll via these TLV
   exchange, then the device MUST send a PKCS#10 to reenroll and request
   a fresh LDevID.

   However, the device should be capabale of autonomic reenrollment if
   it determines that its LDevID is close to expiration wihtout waiting




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   for explicit instruction from the TEAP server.  There are two options
   to do this.

   Option 1: The device reenrolls for a new LDevID directly with the EST
   CA outside the context of the 802.1X TEAP authentication flow.  The
   device uses the Registrar discovery mechanisms oulined in
   [I-D.ietf-anima-bootstrapping-keyinfra] to discover the Registrar and
   the device sends the EST reenroll messages to the discovered
   Registrar endpoint.  No new TEAP TLVs are defined to facilitate
   discover of the Registrar or EST endpoints inside the context of the
   TEAP tunnel.

   Option 2: When the device is perfroming a periodic 802.1X
   authentication using its current LDevID, it reenrolls for a new
   LDevID by sending a PKCS#10 TLV inside the TEAP TLS tunnel.

4.  PKI Certificate Authority Considerations

   Careful consideration must be given to PKI certificate authority
   handling when:

   o  Establishing the TEAP tunnel

   o  Establishing trust using BRSKI

   These are described in more detail here.

4.1.  TEAP Tunnel Establishment

   The client sends its ClientHello to initiate TLS tunnel
   establishment.  It is possible for the TEAP server to restrict the
   certificates that the client can use for tunnel establishment by
   including a list of CA distinguished names in the
   certificate_authorities field in the CertificateRequest message.
   Network operators may want to do this in order to restrict netwok
   access to clients that have a certificate signed by one of a small
   set of trusted manufacturer/supplier CAs.  If the client has both an
   IDevID and an LDevID, the client should present the LDevID in
   preference to its IDevID if allowed by server policy.

   In practice, network operators will likely want to onboard devices
   from a large number of device manufacturers, with each manufacturer
   using a different root CA when issuing IDevIDs.  If the number of
   different manufacturer root CAs is large, this could result in very
   large TLS handshake messages.  Operators may prefer to include no CAs
   in the certificate_authorities field thus allowing devices to present
   IDevIDs signed by any CA when establishing the TEAP tunnel, and
   instead enforce policy at LDevID enrollment time.



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   It is recommended that the client validate the certificate presented
   by the server in the server's Certificate message, but this may not
   be possible for bootstrapping clients that do not have appropriate
   trust anchors installed yet.  If the client is bootstrapping and has
   not yet completed a BRSKI flow, it will not have trust anchors
   installed yet, and thus will not be able to validate the server's
   certificate.  The client must however note the certificate presented
   by the server for (i) inclusion in the BRSKI-RequestVoucher TLV and
   for (ii) validation once the client has discovered the local domain
   trust anchors.

   If the client does not present a suitable certificate to the server,
   the server MUST terminate the connection and fail the EAP request.

   On establishment of the outer TLS tunnel, the TEAP server will make a
   policy decision on next steps.  Possible policy decisions include:

   o  Option 1: Server grants client full network access and returns
      EAP-Success.  This will typically happen when the client presents
      a valid LDevID.  Network policy may grant client network access
      based on IDevID without requiring the device to enroll to obtain
      an LDevID.

   o  Option 2: Server requires that client perform a full BRSKI flow,
      and then enroll to get an LDevID.  This will typically happen when
      the client presents a valid IDevID and network policy requires all
      clients to have LDevIDs.  The server sends a Request-Action TLV
      that includes a BRSKI-RequestVoucher TLV to the client to instruct
      it to start the BRSKI flow.

   o  Option 3: Server requires that the client reenroll to obtain a new
      LDevID.  This could happen when the client presents a valid LDevID
      that is very close to expiration time, or the server's policy
      requires an LDevID update.  The server sends an Action-Request TLV
      including a PKCS#10 TLV to the client to instruct it to reenroll.

4.2.  BRSKI Trust Establishment

   If the server requires that client perform a full BRSKI flow, it
   sends a Request-Action TLV that includes a zero byte length BRSKI-
   RequestVoucher TLV to the client.  The client sends a new BRSKI-
   RequestVoucher TLV to the server, which contains all data specified
   in [I-D.ietf-anima-bootstrapping-keyinfra] section 5.2.  The client
   includes the server certificate it received in the server's
   Certificate message during outer TLS tunnel establishment in the
   proximity-registrar-cert field.  The client signs the request using
   its IDevID.




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   The server includes all additional information as required by
   [I-D.ietf-anima-bootstrapping-keyinfra] section 5.4 and signs the
   request prior to forwarding to the MASA.

   The MASA responds as per [I-D.ietf-anima-bootstrapping-keyinfra]
   section 5.5.  The response may indicate failure and the server should
   react accordingly to failures by sending a failure response to the
   client, and failing the TEAP method.

   If the MASA replies with a signed voucher and a successful result,
   the server then forwards this response to the client in a BRSKI-
   Voucher TLV.

   When the client receives the signed voucher, it validates the
   signature using its built in trust anchor list, and extracts the
   pinned-domain-cert field.  The client must use the CA included in the
   pinned-domain-cert to validate the certificate that was presented by
   the server when establishing the outer TLS tunnel.  If this
   certificate validation fails, the client must fail the TEAP request
   and not connect to the network.

   If the client successfully validates the server certificate, then it
   must send voucher status telemetry, as required by
   [I-D.ietf-anima-bootstrapping-keyinfra] section 5.6 to the server, in
   a new BRSKI-VoucherTelemetry TLV.

5.  Channel and Crypto Binding

   As the TEAP BRSKI flow does not define or require an inner EAP
   method, there is no explicit need for exchange of Channel-Binding
   TLVs between the device and the TEAP server.

   The TEAP BRSKI TLVs are expected to occur at the beginning of the
   TEAP Phase 2 and MUST occur before the final Crypto-Binding TLV.
   This draft does not exclude the possibility of having other EAP
   methods occur following the TEAP BRSKI TLVs and as such, the Crypto-
   Binding TLV process rules as defined in [RFC7170] apply.

6.  Protocol Flows

   This section outlines protocol flows that map to the 3 server policy
   options described in section Section 4.1.  The protocol flows
   illustrate a TLS1.2 exchange.

   [[TODO]] MISSING EAP Start/identity/Crypto binding, etc.  Flows
   illustrative, but not 100% accurate.





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6.1.  TEAP Server Grants Access

   +--------+             +-------------+     +------+
   | Client |             | TEAP-Server |     | MASA |
   +--------+             +-------------+     +------+
       |                         |                |
       |  ClientHello            |                |
       |------------------------>|                |
       |  ServerHello,           |                |
       |  Certificate(1),        |                |
       |  ServerKeyExchange,     |                |
       |  CertificateRequest(2), |                |
       |  ServerHelloDone,       |                |
       |<------------------------|                |
       |  Certificate(3),        |                |
       |  ClientKeyExchange,     |                |
       |  CertificateVerify,     |                |
       |  ChangeCipherSpec,      |                |
       |  Finished               |                |
       |------------------------>|                |
       |  ChangeCipherSpec,      |                |
       |  Finished               |                |
       |<------------------------|                |
       |  Crypto-Binding TLV     |                |
       |<------------------------|                |
       |  Crypto-Binding TLV     |                |
       |------------------------>|                |
       |  Result TLV             |                |
       |<------------------------|                |
       |  Result TLV             |                |
       |------------------------>|                |
       |      EAP-Success        |                |
       |<------------------------|                |


                    Figure 1: TEAP Server Grants Access

   Notes:

   (1) If the client has completed the BRSKI flow yet, it must validate
   the Certificate received from the server.  If the client has not yet
   completed the BRSKI flow, then it provisionally accepts the server
   Certificate and must validate it later once BRSKI is complete.

   (2) The server may include certificate_authorities field in the
   CertificateRequest message in order to restrict the identity
   certificates that the device is allowed present.




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   (3) The device will present its LDevID, if it has one, in preference
   to its IDevID, if allowed by server policy.

6.2.  TEAP Server Instructs Client to Perform BRSKI Flow

   +--------+             +-------------+     +------+
   | Client |             | TEAP-Server |     | MASA |
   +--------+             +-------------+     +------+
       |                         |                |
       |      ClientHello        |                |
       |------------------------>|                |
       |   ServerHello, etc.(1)  |                |
       |<------------------------|                |
       |     etc., Finished      |                |
       |------------------------>|                |
       |     etc., Finished      |                |
       |<------------------------|                |
       | BRSKI-RequestAction(2)  |                |
       |<------------------------|                |
       | BRSKI-RequestVoucher(3) |                |
       |------------------------>| RequestVoucher |
       |                         |--------------->|
       |                         |    Voucher     |
       |     BRSKI-Voucher(4)    |<---------------|
       |<------------------------|                |
       |  BRSKI-VoucherStatus    |                |
       |------------------------>|                |
       |  Trusted-Server-Root    |                |
       |------------------------>|                |
       |  Trusted-Server-Root    |                |
       |<------------------------|                |
       |     CSR-Attributes      |                |
       |------------------------>|                |
       |     CSR-Attributes      |                |
       |<------------------------|                |
       |         PKCS#10         |                |
       |------------------------>|                |
       |         PKCS#7          |                |
       |<------------------------|                |
       |    EnrollmentStatus     |                |
       |------------------------>|                |
       |  Crypto-Binding TLV     |                |
       |<------------------------|                |
       |  Crypto-Binding TLV     |                |
       |------------------------>|                |
       |  Result TLV             |                |
       |<------------------------|                |
       |  Result TLV             |                |



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       |------------------------>|                |
       |      EAP-Success        |                |
       |<------------------------|                |


       Figure 2: TEAP Server Instructs Client to Perform BRSKI Flow

   Notes:

   (1) If the client has not yet completed the BRSKI flow, then it
   provisionally accepts the server certificate and must validate it
   later once BRSKI is complete.

   (2) The server instructs the client to start the BRSKI flow by
   sending a RequestAction TLV that includes a BRSKI-RequestVoucher TLV.

   (3) The client includes the certificate it received from the server
   in the RequestVoucher message.

   (4) Once the client receives and validates the voucher signed by the
   MASA, it must verify the certificate it previously received from the
   server.

6.3.  TEAP Server Instructs Client to Reenroll



























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   +--------+            +-------------+     +------+
   | Client |            | TEAP-Server |     | MASA |
   +--------+            +-------------+     +------+
       |                        |                |
       |      ClientHello       |                |
       |----------------------->|                |
       |   ServerHello, etc.    |                |
       |<-----------------------|                |
       |     etc., Finished     |                |
       |----------------------->|                |
       |     etc., Finished     |                |
       |<-----------------------|                |
       | RequestAction: PKCS#10 |                |
       |<-----------------------|                |
       |     CSR-Attributes     |                |
       |----------------------->|                |
       |     CSR-Attributes     |                |
       |<-----------------------|                |
       |         PKCS#10        |                |
       |----------------------->|                |
       |         PKCS#7         |                |
       |<-----------------------|                |
       |    EnrollmentStatus    |                |
       |----------------------->|                |
       |  Crypto-Binding TLV    |                |
       |<-----------------------|                |
       |  Crypto-Binding TLV    |                |
       |----------------------->|                |
       |  Result TLV            |                |
       |<-----------------------|                |
       |  Result TLV            |                |
       |----------------------->|                |
       |      EAP-Success       |                |
       |<-----------------------|                |


            Figure 3: TEAP Server Instructs Client to Reenroll

   [[TODO: Hmm, as BRSKI mandates client requests CSR-Attributes, should
   the server send a RequestAction and include two TLVs: one CSR-
   Attributes and one PKCS#10 ? ]]

6.4.  Out of Band Reenroll

   This section shows how the device does a reenroll to refresh its
   LDEvID directly against the Registrar outside the context of the TEAP
   tunnel.




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7.  TEAP TLV Formats

7.1.  BRSKI TLVs

   BRSKI defines 6 new TEAP TLVs.  The following table indicates whether
   the TLVs can be included in Request messages from TEAP server to
   device, or Response messages from device to TEAP server.

   +------------------------+----------+
   | TLV                    | Message  |
   +------------------------+----------+
   | BRSKI-VoucherRequest   | Response |
   | BRSKI-Voucher          | Request  |
   | BRSKI-VoucherStatus    | Response |
   | EnrollmentStatus       | Response |
   | CSR-Attributes         | Response |
   +------------------------+----------+


   These new TLVs are detailed in this section.

7.1.1.  BRSKI-RequestVoucher TLV

   To be completed.

7.1.2.  BRSKI-Voucher TLV

   To be completed.

7.1.3.  BRSKI-VoucherStatus TLV

   To be completed.

7.1.4.  EnrollmentStatus TLV

   To be completed.

7.1.5.  CSR-Attributes TLV

   To be completed.

7.2.  Existing TEAP TLV Specifications

   This section documents allowed usage of existing TEAP TLVs.  The
   definition of the TLV is not changed, however clarifications on
   allowed values for the TLV fields is documented.





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7.2.1.  PKCS#10 TLV

   [RFC7170] defines the PKCS#10 TLV as follows:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |M|R|         TLV Type          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           PKCS#10 Data...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-


   [RFC7170] does not explicitly allow a Length value of zero.

   A Length value of zero is allowed for this TLV when the TEAP server
   sends a Request-Action TLV with a child PKCS#10 TLV to the client.
   In this scenario, there is no PKCS#10 Data included in the TLV.
   Clients MUST NOT send a zero length PKCS#10 TLV to the server.

8.  Fragmentation

   TLS is expected to provide fragmentation support.  Thus EAP-TEAP-
   BRSKI does not specifically provide any, as it is only expected to be
   used as an inner method to TEAP.

9.  IANA Considerations

   TBD.

10.  Security Considerations

   There will be many.

11.  Acknowledgments

   The authors would like to thank Brian Weis for his assistance.

12.  Informative References

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
              S., and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-16 (work in progress), June 2018.






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

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

   [RFC7170]  Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna,
              "Tunnel Extensible Authentication Protocol (TEAP) Version
              1", RFC 7170, DOI 10.17487/RFC7170, May 2014,
              <https://www.rfc-editor.org/info/rfc7170>.

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

Appendix A.  Changes from Earlier Versions

   Draft -00:

   o  Initial revision

Authors' Addresses

   Eliot Lear
   Cisco Systems
   Richtistrasse 7
   Wallisellen  CH-8304
   Switzerland

   Phone: +41 44 878 9200
   Email: lear@cisco.com


   Owen Friel
   Cisco Systems
   170 W. Tasman Dr.
   San Jose, CA  95134
   United States

   Email: ofriel@cisco.com






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   Nancy Cam-Winget
   Cisco Systems
   170 W. Tasman Dr.
   San Jose, CA  95134
   United States

   Email: ncamwing@cisco.com












































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