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Versions: (draft-zhou-emu-eap-fastv2) 00 01 02 03 04 06 07 08 09 10 RFC 7170

EMU Working Group                                                H. Zhou
Internet-Draft                                             N. Cam-Winget
Intended status: Standards Track                              J. Salowey
Expires: September 23, 2013                                Cisco Systems
                                                                S. Hanna
                                                        Juniper Networks
                                                          March 22, 2013


                   Tunnel EAP Method (TEAP) Version 1
                draft-ietf-emu-eap-tunnel-method-06.txt

Abstract

   This document defines the Tunnel Extensible Authentication Protocol
   (TEAP) version 1.  TEAP is a tunnel based EAP method that enables
   secure communication between a peer and a server by using the
   Transport Layer Security (TLS) to establish a mutually authenticated
   tunnel.  Within the tunnel, Type-Length-Value (TLV) objects are used
   to convey authentication related data between the EAP peer and the
   EAP server.

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 23, 2013.

Copyright Notice

   Copyright (c) 2013 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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   6
     1.1.  Specification Requirements  . . . . . . . . . . . . . . .   6
     1.2.  Design Goals  . . . . . . . . . . . . . . . . . . . . . .   6
     1.3.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   8
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   9
     2.1.  Architectural Model . . . . . . . . . . . . . . . . . . .   9
     2.2.  Protocol Layering Model . . . . . . . . . . . . . . . . .  10
   3.  TEAP Protocol . . . . . . . . . . . . . . . . . . . . . . . .  11
     3.1.  Version Negotiation . . . . . . . . . . . . . . . . . . .  11
     3.2.  TEAP Authentication Phase 1: Tunnel Establishment . . . .  12
       3.2.1.  TLS Session Resume Using Server State . . . . . . . .  13
       3.2.2.  TLS Session Resume Using a PAC  . . . . . . . . . . .  14
       3.2.3.  Transition between Abbreviated and Full TLS
               Handshake . . . . . . . . . . . . . . . . . . . . . .  15
     3.3.  TEAP Authentication Phase 2: Tunneled Authentication  . .  16
       3.3.1.  EAP Sequences . . . . . . . . . . . . . . . . . . . .  16
       3.3.2.  Optional Password Authentication  . . . . . . . . . .  17
       3.3.3.  Protected Termination and Acknowledged Result
               Indication  . . . . . . . . . . . . . . . . . . . . .  17
     3.4.  Determining Peer-Id and Server-Id . . . . . . . . . . . .  18
     3.5.  TEAP Session Identifier . . . . . . . . . . . . . . . . .  19
     3.6.  Error Handling  . . . . . . . . . . . . . . . . . . . . .  19
       3.6.1.  Outer Layer Errors  . . . . . . . . . . . . . . . . .  20
       3.6.2.  TLS Layer Errors  . . . . . . . . . . . . . . . . . .  20
       3.6.3.  Phase 2 Errors  . . . . . . . . . . . . . . . . . . .  21
     3.7.  Fragmentation . . . . . . . . . . . . . . . . . . . . . .  21
     3.8.  Peer Services . . . . . . . . . . . . . . . . . . . . . .  22
       3.8.1.  PAC Provisioning  . . . . . . . . . . . . . . . . . .  23
       3.8.2.  Certificate Provisioning Within the Tunnel  . . . . .  24
       3.8.3.  Server Unauthenticated Provisioning Mode  . . . . . .  24
       3.8.4.  Channel Binding . . . . . . . . . . . . . . . . . . .  25
   4.  Message Formats . . . . . . . . . . . . . . . . . . . . . . .  25
     4.1.  TEAP Message Format . . . . . . . . . . . . . . . . . . .  25
     4.2.  TEAP TLV Format and Support . . . . . . . . . . . . . . .  28
       4.2.1.  General TLV Format  . . . . . . . . . . . . . . . . .  29
       4.2.2.  Authority-ID TLV  . . . . . . . . . . . . . . . . . .  31
       4.2.3.  Identity-Type TLV . . . . . . . . . . . . . . . . . .  32
       4.2.4.  Result TLV  . . . . . . . . . . . . . . . . . . . . .  33
       4.2.5.  NAK TLV . . . . . . . . . . . . . . . . . . . . . . .  34
       4.2.6.  Error TLV . . . . . . . . . . . . . . . . . . . . . .  36



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       4.2.7.  Channel-Binding TLV . . . . . . . . . . . . . . . . .  37
       4.2.8.  Vendor-Specific TLV . . . . . . . . . . . . . . . . .  38
       4.2.9.  Request-Action TLV  . . . . . . . . . . . . . . . . .  39
       4.2.10. EAP-Payload TLV . . . . . . . . . . . . . . . . . . .  41
       4.2.11. Intermediate-Result TLV . . . . . . . . . . . . . . .  43
       4.2.12. PAC TLV Format  . . . . . . . . . . . . . . . . . . .  44
         4.2.12.1.  Formats for PAC Attributes . . . . . . . . . . .  45
         4.2.12.2.  PAC-Key  . . . . . . . . . . . . . . . . . . . .  46
         4.2.12.3.  PAC-Opaque . . . . . . . . . . . . . . . . . . .  46
         4.2.12.4.  PAC-Info . . . . . . . . . . . . . . . . . . . .  47
         4.2.12.5.  PAC-Acknowledgement TLV  . . . . . . . . . . . .  49
         4.2.12.6.  PAC-Type TLV . . . . . . . . . . . . . . . . . .  50
       4.2.13. Crypto-Binding TLV  . . . . . . . . . . . . . . . . .  51
       4.2.14. Basic-Password-Auth-Req TLV . . . . . . . . . . . . .  54
       4.2.15. Basic-Password-Auth-Resp TLV  . . . . . . . . . . . .  55
       4.2.16. PKCS#7 TLV  . . . . . . . . . . . . . . . . . . . . .  56
       4.2.17. PKCS#10 TLV . . . . . . . . . . . . . . . . . . . . .  58
       4.2.18. Trusted-Server-Root TLV . . . . . . . . . . . . . . .  58
     4.3.  TLV Rules . . . . . . . . . . . . . . . . . . . . . . . .  60
       4.3.1.  Outer TLVs  . . . . . . . . . . . . . . . . . . . . .  60
       4.3.2.  Inner TLVs  . . . . . . . . . . . . . . . . . . . . .  61
   5.  Cryptographic Calculations  . . . . . . . . . . . . . . . . .  61
     5.1.  TEAP Authentication Phase 1: Key Derivations  . . . . . .  62
     5.2.  Intermediate Compound Key Derivations . . . . . . . . . .  62
     5.3.  Computing the Compound MAC  . . . . . . . . . . . . . . .  64
     5.4.  EAP Master Session Key Generation . . . . . . . . . . . .  65
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  65
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  68
     7.1.  Mutual Authentication and Integrity Protection  . . . . .  69
     7.2.  Method Negotiation  . . . . . . . . . . . . . . . . . . .  69
     7.3.  Separation of Phase 1 and Phase 2 Servers . . . . . . . .  70
     7.4.  Mitigation of Known Vulnerabilities and Protocol
           Deficiencies  . . . . . . . . . . . . . . . . . . . . . .  70
       7.4.1.  User Identity Protection and Verification . . . . . .  71
       7.4.2.  Dictionary Attack Resistance  . . . . . . . . . . . .  72
       7.4.3.  Protection against Man-in-the-Middle Attacks  . . . .  72
       7.4.4.  PAC Binding to User Identity  . . . . . . . . . . . .  73
     7.5.  Protecting against Forged Clear Text EAP Packets  . . . .  73
     7.6.  Server Certificate Validation . . . . . . . . . . . . . .  74
     7.7.  Tunnel PAC Considerations . . . . . . . . . . . . . . . .  74
     7.8.  Security Claims . . . . . . . . . . . . . . . . . . . . .  74
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  76
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  76
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  76
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  77
   Appendix A.  Evaluation Against Tunnel Based EAP Method
                Requirements . . . . . . . . . . . . . . . . . . . .  80
     A.1.  Requirement 4.1.1 RFC Compliance  . . . . . . . . . . . .  80



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     A.2.  Requirement 4.2.1 TLS Requirements  . . . . . . . . . . .  80
     A.3.  Requirement 4.2.1.1.1 Cipher Suite Negotiation  . . . . .  80
     A.4.  Requirement 4.2.1.1.2 Tunnel Data Protection Algorithms .  80
     A.5.  Requirement 4.2.1.1.3 Tunnel Authentication and Key
           Establishment . . . . . . . . . . . . . . . . . . . . . .  81
     A.6.  Requirement 4.2.1.2 Tunnel Replay Protection  . . . . . .  81
     A.7.  Requirement 4.2.1.3 TLS Extensions  . . . . . . . . . . .  81
     A.8.  Requirement 4.2.1.4 Peer Identity Privacy . . . . . . . .  81
     A.9.  Requirement 4.2.1.5 Session Resumption  . . . . . . . . .  81
     A.10. Requirement 4.2.2 Fragmentation . . . . . . . . . . . . .  81
     A.11. Requirement 4.2.3 Protection of Data External to Tunnel .  82
     A.12. Requirement 4.3.1 Extensible Attribute Types  . . . . . .  82
     A.13. Requirement 4.3.2 Request/Challenge Response Operation  .  82
     A.14. Requirement 4.3.3 Indicating Criticality of Attributes  .  82
     A.15. Requirement 4.3.4 Vendor Specific Support . . . . . . . .  82
     A.16. Requirement 4.3.5 Result Indication . . . . . . . . . . .  82
     A.17. Requirement 4.3.6 Internationalization of Display
           Strings . . . . . . . . . . . . . . . . . . . . . . . . .  82
     A.18. Requirement 4.4 EAP Channel Binding Requirements  . . . .  82
     A.19. Requirement 4.5.1.1 Confidentiality and Integrity . . . .  83
     A.20. Requirement 4.5.1.2 Authentication of Server  . . . . . .  83
     A.21. Requirement 4.5.1.3 Server Certificate Revocation
           Checking  . . . . . . . . . . . . . . . . . . . . . . . .  83
     A.22. Requirement 4.5.2  Internationalization . . . . . . . . .  83
     A.23. Requirement 4.5.3 Meta-data . . . . . . . . . . . . . . .  83
     A.24. Requirement 4.5.4 Password Change . . . . . . . . . . . .  83
     A.25. Requirement 4.6.1 Method Negotiation  . . . . . . . . . .  83
     A.26. Requirement 4.6.2 Chained Methods . . . . . . . . . . . .  83
     A.27. Requirement 4.6.3 Cryptographic Binding with the TLS
           Tunnel  . . . . . . . . . . . . . . . . . . . . . . . . .  84
     A.28. Requirement 4.6.4 Peer Initiated  . . . . . . . . . . . .  84
     A.29. Requirement 4.6.5 Method Meta-data  . . . . . . . . . . .  84
   Appendix B.  Major Differences from EAP-FAST  . . . . . . . . . .  84
   Appendix C.  Examples . . . . . . . . . . . . . . . . . . . . . .  85
     C.1.  Successful Authentication . . . . . . . . . . . . . . . .  85
     C.2.  Failed Authentication . . . . . . . . . . . . . . . . . .  86
     C.3.  Full TLS Handshake using Certificate-based Cipher Suite .  88
     C.4.  Client authentication during Phase 1 with identity
           privacy . . . . . . . . . . . . . . . . . . . . . . . . .  89
     C.5.  Fragmentation and Reassembly  . . . . . . . . . . . . . .  91
     C.6.  Sequence of EAP Methods . . . . . . . . . . . . . . . . .  93
     C.7.  Failed Crypto-binding . . . . . . . . . . . . . . . . . .  95
     C.8.  Sequence of EAP Method with Vendor-Specific TLV
           Exchange  . . . . . . . . . . . . . . . . . . . . . . . .  96
     C.9.  Peer Requests Inner Method After Server Sends Result
           TLV . . . . . . . . . . . . . . . . . . . . . . . . . . .  98
     C.10. Channel Binding . . . . . . . . . . . . . . . . . . . . . 100
   Appendix D.  Major Differences from Previous Revisions  . . . . . 101



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     D.1.  Changes from -05  . . . . . . . . . . . . . . . . . . . . 101
     D.2.  Changes from -04  . . . . . . . . . . . . . . . . . . . . 102
     D.3.  Changes from -03  . . . . . . . . . . . . . . . . . . . . 102
     D.4.  Changes from -02  . . . . . . . . . . . . . . . . . . . . 103
     D.5.  Changes from -01  . . . . . . . . . . . . . . . . . . . . 103
     D.6.  Changes from -00  . . . . . . . . . . . . . . . . . . . . 104













































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1.  Introduction

   An Extensible Authentication Protocol (EAP) tunnel method is an EAP
   method that establishes a secure tunnel and executes other EAP
   methods under the protection of that secure tunnel.  An EAP tunnel
   method can be used in any lower layer protocol that supports EAP
   authentication.  There are several existing EAP tunnel methods that
   use Transport Layer Security (TLS) [RFC5246] to establish the secure
   tunnel.  EAP methods supporting this include Protected EAP (PEAP)
   [PEAP], Tunneled Transport Layer Security EAP (TTLS) [RFC5281] and
   EAP Flexible Authentication via Secure Tunneling (EAP-FAST)
   [RFC4851].  However, they all are either vendor specific or
   informational and industry calls for a standard-track tunnel EAP
   method.  [RFC6678] outlines the list of requirements for a standard
   tunnel based EAP method.

   Since the introduction of EAP-FAST [RFC4851] a few years ago, it has
   been widely adopted in variety of devices and platforms due to its
   strong security, flexibility and ease of deployment.  It has been
   adopted by EMU working group as the basis for the standard tunnel
   based EAP method.  This document describes Tunnel Extensible
   Authentication Protocol (TEAP) version 1, based on EAP-FAST [RFC4851]
   with some minor changes, to meet the requirements outlined in
   [RFC6678] for a standard tunnel based EAP method.

1.1.  Specification Requirements

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

1.2.  Design Goals

   Network access solutions requiring user friendly and easily
   deployable secure authentication mechanisms highlight the need for
   strong mutual authentication protocols that enable the use of weaker
   user credentials.  This document defines an Extensible Authentication
   Protocol (EAP) which consists of establishing a Transport Layer
   Security (TLS) tunnel using TLS version 1.2 [RFC5246] or a successor
   version supported by both parties.  Once the tunnel is established,
   the protocol further exchanges data in the form of Type-Length-Value
   (TLV) objects to perform further authentication.  TEAP supports the
   TLS extension defined in [RFC5077] to support fast re-establishment
   of the secure tunnel without having to maintain per-session state on
   the server.

   TEAP's design motivations included:




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   o  Mutual authentication: an EAP server's ability to verify the
      identity and authenticity of the peer, and the peer's ability to
      verify the authenticity of the EAP server.

   o  Immunity to passive dictionary attacks: many authentication
      protocols require a password to be explicitly provided (either as
      cleartext or hashed) by the peer to the EAP server; at minimum,
      the communication of the weak credential (e.g., password) provides
      immunity from eavesdropping.

   o  Immunity to man-in-the-middle (MitM) attacks: in establishing a
      mutually authenticated protected tunnel, the protocol prevents
      adversaries from successfully interjecting information into the
      conversation between the peer and the EAP server.

   o  Flexibility to enable support for most password authentication
      interfaces: as many different password interfaces (e.g., Microsoft
      Challenge Handshake Authentication Protocol (MS-CHAP), Lightweight
      Directory Access Protocol (LDAP), One-Time Password (OTP), etc.)
      exist to authenticate a peer, the protocol provides this support
      for legacy password authentication seamlessly.

   o  Cryptographic algorithm agility: a cryptographic algorithm's
      strength is not perpetual, as weaknesses in an algorithm are
      discovered or increased processing power overtakes an algorithm
      over time.  Hence, the protocol does not rely on any single
      cryptographic algorithm.  Instead, it supports run-time
      negotiation to select among an extensible set of cryptographic
      algorithms and also allow users to choose the algorithm that best
      meets their needs.

   o  Sequence of chained EAP methods: Several circumstances are best
      addressed by using chained EAP methods.  For example, it may be
      desirable to authenticate the user and also authenticate the
      device being used.  The protocol supports chained EAP methods
      while including protection against attacks on method chaining.

   With these motivational goals defined, further secondary design
   criteria are imposed:

   o  Flexibility to extend the communications inside the tunnel: with
      the growing complexity in network infrastructures, the need to
      gain authentication, authorization, and accounting is also
      evolving.  For instance, there may be instances in which multiple
      existing authentication protocols are required to achieve mutual
      authentication.  Similarly, different protected conversations may
      be required to achieve the proper authorization once a peer has
      successfully authenticated.



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   o  Minimize the authentication server's per user authentication state
      requirements: with large deployments, it is typical to have
      servers authenticating many peers.  With many different
      authentication servers deployed, a peer's session state may need
      to be replicated to allow for high availability or mobility
      scenarios.  To facilitate scalable authentication server
      deployments and more efficient per user state management, it is
      desirable for a peer to cache its session state that has been
      securely encapsulated by the authentication server infrastructure.

   o  Efficiency: specifically when using wireless media, peers will be
      limited in computational and power resources.  The protocol
      enables the network access communication to be computationally
      lightweight.

   o  Channel bindings: EAP channel bindings seek to authenticate
      previously unauthenticated information provided by the
      authenticator to the EAP peer, by allowing the peer and server to
      compare their perception of network properties in a secure
      channel.  It is used to solve the lying NAS and the lying provider
      problems.  The protocol should provide support for EAP channel
      bindings as defined in [RFC6677].

1.3.  Terminology

   Much of the terminology in this document comes from [RFC3748].
   Additional terms are defined below:

   Protected Access Credential (PAC)

      Credentials distributed to a peer for future optimized network
      authentication.  The PAC consists of a minimum of two components:
      a shared secret and an opaque element.  The shared secret
      component contains the pre-shared key between the peer and the
      authentication server.  The opaque part is provided to the peer
      and is presented to the authentication server when the peer wishes
      to obtain access to network resources.  The opaque element and
      shared secret are used with TLS stateless session resumption
      defined in RFC 5077 [RFC5077] to establish a protected TLS
      session.  The secret key and opaque part may distributed using RFC
      5077 messages or using TLVs within the TEAP tunnel.  Finally, a
      PAC may optionally include other information that may be useful to
      the peer.

   Type-Length-Value (TLV)

      The TEAP protocol utilizes objects in Type Length Value (TLV)
      format.  The TLV format is defined in Section 4.2.



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2.  Protocol Overview

   TEAP authentication occurs in two phases.  In the first phase, TEAP
   employs the TLS [RFC5246] handshake to provide an authenticated key
   exchange and to establish a protected tunnel.  Once the tunnel is
   established, the second phase begins with the peer and server
   engaging in further conversations to establish the required
   authentication and authorization policies.  TEAP makes use of Type-
   Length-Value objects (TLVs) to carry out the inner authentication,
   results and other information, such as channel binding information.

   TEAP makes use of the TLS enhancements in Ticket Extension [RFC5077]
   to enable an optimized TLS tunnel session resume while minimizing
   server state.  The ticket is referred to as the Protected Access
   Credential opaque data (or PAC-Opaque).  The PAC-Opaque may be
   distributed through the use of the NewSessionTicket message or
   through a mechanism that uses TLVs within phase 2 of TEAP.  The
   secret key used to resume the session in TEAP is referred to as the
   Protected Access Credential key (or PAC-Key).  When the
   NewSessionTicket message is being used to distribute the PAC-Opaque,
   the PAC-Key is the Master Secret for the session.  If TEAP phase 2 is
   used to distribute the PAC-Opaque, then the PAC-Key is distributed
   along with the PAC-Opaque.  TEAP implementations MUST support the RFC
   5077 mechanism for distributing a PAC-Opaque and it is RECOMMENDED
   that implementations support the capability to distribute the ticket
   and secret key within the TEAP tunnel.

   The TEAP conversation is used to establish or resume an existing
   session to typically establish network connectivity between a peer
   and the network.  Upon successful execution of TEAP, both EAP peer
   and EAP server derive strong session key material that can then be
   communicated to the network access server (NAS) for use in
   establishing a link layer security association.

2.1.  Architectural Model

   The network architectural model for TEAP usage is shown below:


    +----------+      +----------+      +----------+      +----------+
    |          |      |          |      |          |      |  Inner   |
    |   Peer   |<---->|  Authen- |<---->|   TEAP   |<---->|  Method  |
    |          |      |  ticator |      |  server  |      |  server  |
    |          |      |          |      |          |      |          |
    +----------+      +----------+      +----------+      +----------+


                         TEAP Architectural Model



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   The entities depicted above are logical entities and may or may not
   correspond to separate network components.  For example, the TEAP
   server and inner method server might be a single entity; or the
   authenticator and TEAP server might be a single entity; or the
   functions of the authenticator, TEAP server, and inner method server
   might be combined into a single physical device.  For example,
   typical IEEE 802.11 deployments place the Authenticator in an access
   point (AP) while a Radius server may provide the TEAP and inner
   method server components.  The above diagram illustrates the division
   of labor among entities in a general manner and shows how a
   distributed system might be constructed; however, actual systems
   might be realized more simply.  The security considerations
   Section 7.3 provides an additional discussion of the implications of
   separating the TEAP server from the inner method server.

2.2.  Protocol Layering Model

   TEAP packets are encapsulated within EAP; EAP in turn requires a
   carrier protocol for transport.  TEAP packets encapsulate TLS, which
   is then used to encapsulate user authentication information.  Thus,
   TEAP messaging can be described using a layered model, where each
   layer encapsulates the layer above it.  The following diagram
   clarifies the relationship between protocols:


    +---------------------------------------------------------------+
    |       Inner EAP Method     |     Other TLV information        |
    |---------------------------------------------------------------|
    |                 TLV Encapsulation (TLVs)                      |
    |---------------------------------------------------------------|
    |                TLS         |     Optional Outer TLVs          |
    |---------------------------------------------------------------|
    |                         TEAP                                  |
    |---------------------------------------------------------------|
    |                         EAP                                   |
    |---------------------------------------------------------------|
    |    Carrier Protocol (EAP over LAN, RADIUS, Diameter, etc.)    |
    +---------------------------------------------------------------+


                          Protocol Layering Model

   The TLV layer is a payload with Type-Length-Value (TLV) Objects
   defined in Section 4.2.  The TLV objects are used to carry arbitrary
   parameters between an EAP peer and an EAP server.  All conversations
   in the TEAP protected tunnel MUST be encapsulated in a TLV layer.

   TEAP packets may include TLVs both inside and outside the TLS tunnel.



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   The term "Outer TLVs" is used to refer to optional TLVs outside the
   TLS tunnel, which are only allowed in the first two messages in the
   TEAP protocol.  That is the first EAP server to peer message and
   first peer to EAP server message.  If the message is fragmented, the
   whole set of messages is counted as one message.  The term "Inner
   TLVs" is used to refer to TLVs sent within the TLS tunnel.  In TEAP
   Phase 1, Outer TLVs are used to help establishing the TLS tunnel, but
   no Inner TLVs are used.  In Phase 2 of the TEAP conversation, TLS
   records may encapsulate zero or more Inner TLVs, but no Outer TLVs.

   Methods for encapsulating EAP within carrier protocols are already
   defined.  For example, IEEE 802.1X [IEEE.802-1X.2004] may be used to
   transport EAP between the peer and the authenticator; RADIUS
   [RFC3579] or Diameter [RFC4072] may be used to transport EAP between
   the authenticator and the EAP server.

3.  TEAP Protocol

   TEAP authentication occurs in two phases.  In the first phase, TEAP
   employs the TLS handshake to provide an authenticated key exchange
   and to establish a protected tunnel.  Once the tunnel is established
   the second phase begins with the peer and server engaging in further
   conversations to establish the required authentication and
   authorization policies.  The operation of the protocol, including
   Phase 1 and Phase 2, is the topic of this section.  The format of
   TEAP messages is given in Section 4 and the cryptographic
   calculations are given in Section 5.

3.1.  Version Negotiation

   TEAP packets contain a 3-bit version field, following the TLS Flags
   field, which enables future TEAP implementations to be backward
   compatible with previous versions of the protocol.  This
   specification documents the TEAP version 1 protocol; implementations
   of this specification MUST use a version field set to 1.

   Version negotiation proceeds as follows:

      In the first EAP-Request sent with EAP type=TEAP, the EAP server
      MUST set the version field to the highest supported version
      number.


      If the EAP peer supports this version of the protocol, it MUST
      respond with an EAP-Response of EAP type=TEAP, and the version
      number proposed by the TEAP server.





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      If the TEAP peer does not support this version but supports the
      version that is lower than the version proposed by the TEAP
      server, it responds with an EAP-Response of EAP type=TEAP and the
      highest supported version number.  If the TEAP peer only supports
      the version that is higher than the version proposed by the TEAP
      server, then use of TEAP will not be possible.  In this case, the
      TEAP peer should send back an EAP-Nak with other proposed EAP
      method if available.


      If the TEAP server does not support the version number proposed by
      the TEAP peer, it MAY terminate the conversation with EAP-Failure
      or negotiate for another EAP type.  Otherwise the TEAP
      conversation continues.

   The version negotiation procedure guarantees that the TEAP peer and
   server will agree to the latest version supported by both parties.
   If version negotiation fails, then use of TEAP will not be possible,
   and another mutually acceptable EAP method will need to be negotiated
   if authentication is to proceed.

   The TEAP version is not protected by TLS; and hence can be modified
   in transit.  In order to detect a modification of the TEAP version,
   the peers MUST exchange the TEAP version number received during
   version negotiation using the Crypto-Binding TLV described in
   Section 4.2.13.  The receiver of the Crypto-Binding TLV MUST verify
   that the version received in the Crypto-Binding TLV matches the
   version sent by the receiver in the TEAP version negotiation.

3.2.  TEAP Authentication Phase 1: Tunnel Establishment

   TEAP is based on the TLS handshake [RFC5246] to establish an
   authenticated and protected tunnel.  The TLS version offered by the
   peer and server MUST be TLS version 1.2 [RFC5246] or later.  This
   version of the TEAP implementation MUST support the following TLS
   ciphersuites:

      TLS_RSA_WITH_AES_128_CBC_SHA [RFC5246]

      TLS_DHE_RSA_WITH_AES_128_CBC_SHA [RFC5246]

   Other ciphersuites MAY be supported.  It is REQUIRED that anonymous
   ciphersuites such as TLS_DH_anon_WITH_AES_128_CBC_SHA [RFC5246] only
   be used in the case when the inner authentication method provides
   mutual authentication, key generation, and resistance to man-in-the-
   middle and dictionary attack.  During the TEAP Phase 1 conversation,
   the TEAP endpoints MAY negotiate TLS compression.  During TLS tunnel
   establishment, TLS extensions MAY be used.  For instance, Certificate



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   Status Request extension [RFC6066] can be used to leverage a
   certificate-status protocol such as OCSP [RFC2560] to check the
   validity of server certificates.  TLS renegotiation indications
   defined in RFC 5746 [RFC5746] MUST be supported.

   The EAP server initiates the TEAP conversation with an EAP request
   containing a TEAP/Start packet.  This packet includes a set Start (S)
   bit, the TEAP version as specified in Section 3.1, and an authority
   identity TLV.  The TLS payload in the initial packet is empty.  The
   authority identity TLV (Authority-ID TLV) is used to provide the peer
   a hint of the server's identity that may be useful in helping the
   peer select the appropriate credential to use.  Assuming that the
   peer supports TEAP, the conversation continues with the peer sending
   an EAP-Response packet with EAP type of TEAP with the Start (S) bit
   clear and the version as specified in Section 3.1.  This message
   encapsulates one or more TLS records containing the TLS handshake
   messages.  If the TEAP version negotiation is successful then the
   TEAP conversation continues until the EAP server and EAP peer are
   ready to enter Phase 2.  When the full TLS handshake is performed,
   then the first payload of TEAP Phase 2 MAY be sent along with server-
   finished handshake message to reduce the number of round trips.

   TEAP implementations MUST support peer authentication during tunnel
   establishment using the TLS ciphersuites specified in Section 3.2.
   The EAP peer does not need to authenticate as part of the TLS
   exchange, but can alternatively be authenticated through additional
   exchanges carried out in Phase 2.

   The TEAP tunnel protects peer identity information exchanged during
   phase 2 from disclosure outside the tunnel.  Implementations that
   wish to provide identity privacy for the peer identity need to
   carefully consider what information is disclosed outside the tunnel
   prior to phase 2.  TEAP implementations SHOULD support the immediate
   renegotiation of a TLS session to initiate a new handshake message
   exchange under the protection of the current cipher suite.  This
   allows support for protection of the peer's identity when using TLS
   client authentication.  An example of the exchanges using TLS
   renegotiation to protect privacy is shown in Appendix C.

   The following sections describe resuming a TLS session based on
   server-side or client-side state.

3.2.1.  TLS Session Resume Using Server State

   TEAP session resumption is achieved in the same manner TLS achieves
   session resume.  To support session resumption, the server and peer
   minimally cache the Session ID, master secret, and ciphersuite.  The
   peer attempts to resume a session by including a valid Session ID



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   from a previous handshake in its ClientHello message.  If the server
   finds a match for the Session ID and is willing to establish a new
   connection using the specified session state, the server will respond
   with the same Session ID and proceed with the TEAP Phase 1 tunnel
   establishment based on a TLS abbreviated handshake.  After a
   successful conclusion of the TEAP Phase 1 conversation, the
   conversation then continues on to Phase 2.

3.2.2.  TLS Session Resume Using a PAC

   TEAP supports the resumption of sessions based on server state being
   stored on the client side using the TLS SessionTicket extension
   techniques described in [RFC5077].  This version of TEAP supports the
   provisioning of a ticket called a Protected Access Credential (PAC)
   through the use of the NewSessionTicket handshake described in
   [RFC5077], as well as provisioning of a PAC inside the protected
   tunnel.  Implementations may provide additional ways to provision the
   PAC, such as manual configuration.  Since the PAC mentioned here is
   used for establishing the TLS Tunnel, it is more specifically
   referred to as the Tunnel PAC.  The Tunnel PAC is a security
   credential provided by the EAP server to a peer and comprised of:

   1.  PAC-Key: this is the key used by the peer as the TLS master
       secret to establish the TEAP Phase 1 tunnel.  The PAC-Key is a
       strong high-entropy at minimum 48-octet key and is typically the
       master secret from a previous TLS session.  The PAC-Key is a
       secret and MUST be treated accordingly.  In the case that a PAC-
       Key is provisioned to the peer through another means it MUST have
       its confidentiality and integrity protected by a mechanism, such
       as the TEAP phase 2 tunnel.  The PAC-Key MUST be stored securely
       by the peer.


   2.  PAC-Opaque: this is a variable length field containing the ticket
       that is sent to the EAP server during the TEAP Phase 1 tunnel
       establishment based on RFC 5077.  The PAC-Opaque can only be
       interpreted by the EAP server to recover the required information
       for the server to validate the peer's identity and
       authentication.  The PAC-Opaque includes the PAC-Key and other
       TLS session parameters.  It may contain the PAC's peer identity.
       The PAC-Opaque format and contents are specific to the PAC
       issuing server.  The PAC-Opaque may be presented in the clear, so
       an attacker MUST NOT be able to gain useful information from the
       PAC-Opaque itself.  The server issuing the PAC-Opaque needs to
       ensure it is protected with strong cryptographic keys and
       algorithms.  The PAC-Opaque may be distributed using the
       NewSessionTicket message defined in RFC 5077 or it may be
       distributed through another mechanism such as the phase 2 TLVs



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       defined in this document.


   3.  PAC-Info: this is an optional variable length field used to
       provide, at a minimum, the authority identity of the PAC issuer.
       Other useful but not mandatory information, such as the PAC-Key
       lifetime, may also be conveyed by the PAC issuing server to the
       peer during PAC provisioning or refreshment.  PAC-Info is not
       included if the NewSessionTicket message is used to provision the
       PAC.

   The use of the PAC is based on the SessionTicket extension defined in
   [RFC5077].  The EAP server initiates the TEAP conversation as normal.
   Upon receiving the Authority-ID TLV from the server, the peer checks
   to see if it has an existing valid PAC-Key and PAC-Opaque for the
   server.  If it does, then it obtains the PAC-Opaque and puts it in
   the SessionTicket extension in the ClientHello.  It is RECOMMENDED in
   TEAP that the peer include an empty Session ID in a ClientHello
   containing a PAC-Opaque.  This version of TEAP supports the
   NewSessionTicket Handshake message as described in [RFC5077] for
   distribution of a new PAC, as well as the provisioning of PAC inside
   the protected tunnel.  If the PAC-Opaque included in the
   SessionTicket extension is valid and the EAP server permits the
   abbreviated TLS handshake, it will select the cipher suite from
   information within the PAC-Opaque and finish with the abbreviated TLS
   handshake.  If the server receives a Session ID and a PAC-Opaque in
   the SessionTicket extension in a ClientHello, it should place the
   same Session ID in the ServerHello if it is resuming a session based
   on the PAC-Opaque.  The conversation then proceeds as described in
   [RFC5077] until the handshake completes or a fatal error occurs.
   After the abbreviated handshake completes, the peer and the server
   are ready to commence Phase 2.

3.2.3.  Transition between Abbreviated and Full TLS Handshake

   If session resumption based on server-side or client-side state
   fails, the server can gracefully fall back to a full TLS handshake.
   If the ServerHello received by the peer contains an empty Session ID
   or a Session ID that is different than in the ClientHello, the server
   may fall back to a full handshake.  The peer can distinguish the
   server's intent of negotiating full or abbreviated TLS handshake by
   checking the next TLS handshake messages in the server response to
   the ClientHello.  If ChangeCipherSpec follows the ServerHello in
   response to the ClientHello, then the server has accepted the session
   resumption and intends to negotiate the abbreviated handshake.
   Otherwise, the server intends to negotiate the full TLS handshake.  A
   peer can request for a new PAC to be provisioned after the full TLS
   handshake and mutual authentication of the peer and the server.  A



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   peer SHOULD NOT request for a new PAC to be provisioned after the
   abbreviated handshake, as requesting a new session ticket based on
   resumed session is not permitted.  In order to facilitate the
   fallback to a full handshake the peer SHOULD include cipher suites
   that allow for a full handshake and possibly PAC provisioning so the
   server can select one of these in case session resumption fails.  An
   example of the transition is shown in Appendix C.

3.3.  TEAP Authentication Phase 2: Tunneled Authentication

   The second portion of the TEAP Authentication occurs immediately
   after successful completion of Phase 1.  Phase 2 occurs even if both
   peer and authenticator are authenticated in the Phase 1 TLS
   negotiation.  Phase 2 MUST NOT occur if the Phase 1 TLS handshake
   fails.  Phase 2 consists of a series of requests and responses
   encapsulated in TLV objects defined in Section 4.2.  Phase 2 MUST
   always end with a Crypto-Binding TLV exchange described in
   Section 4.2.13 and a protected termination exchange described in
   Section 3.3.3.  The TLV exchange may include the execution of zero or
   more EAP methods within the protected tunnel as described in
   Section 3.3.1.  A server MAY proceed directly to the protected
   termination exchange if it does not wish to request further
   authentication from the peer.  However, the peer and server MUST NOT
   assume that either will skip inner EAP methods or other TLV
   exchanges.  The peer may have roamed to a network that requires
   conformance with a different authentication policy, or the peer may
   request the server take additional action (e.g., channel binding)
   through the use of the Request-Action TLV as defined in
   Section 4.2.9.

3.3.1.  EAP Sequences

   EAP [RFC3748] prohibits use of multiple authentication methods within
   a single EAP conversation in order to limit vulnerabilities to man-
   in-the-middle attacks.  TEAP addresses man-in-the-middle attacks
   through support for cryptographic protection of the inner EAP
   exchange and cryptographic binding of the inner authentication
   method(s) to the protected tunnel.  EAP methods are executed serially
   in a sequence.  This version of TEAP does not support initiating
   multiple EAP methods simultaneously in parallel.  The methods need
   not be distinct.  For example, EAP-TLS could be run twice as an inner
   method, first using machine credentials followed by a second instance
   using user credentials.

   EAP method messages are carried within EAP-Payload TLVs defined in
   Section 4.2.10.  If more than one method is going to be executed in
   the tunnel, then upon method completion, the server MUST send an
   Intermediate-Result TLV indicating the result.  The peer MUST respond



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   to the Intermediate-Result TLV indicating its result.  If the result
   indicates success, the Intermediate-Result TLV MUST be accompanied by
   a Crypto-Binding TLV.  The Crypto-Binding TLV is further discussed in
   Section 4.2.13 and Section 5.3.  The Intermediate-Result TLVs can be
   included with other TLVs such as EAP-Payload TLVs starting a new EAP
   conversation or with the Result TLV used in the protected termination
   exchange.

   If both peer and server indicate success, then the method is
   considered complete.  If either indicates failure, then the method is
   considered failed.  The result of failure of an EAP method does not
   always imply a failure of the overall authentication.  If one
   authentication method fails, the server may attempt to authenticate
   the peer with a different method.

3.3.2.  Optional Password Authentication

   The use of EAP-FAST-GTC as defined in RFC 5421 [RFC5421] is not
   recommended with TEAPv1.  Implementations should instead make use of
   the password authentication TLVs defined in this specification.  The
   authentication server initiates password authentication by sending a
   Basic-Password-Auth-Req TLV defined in Section 4.2.14.  If the peer
   wishes to participate in password authentication then it responds
   with a Basic-Password-Auth-Resp TLV as defined in Section 4.2.15 that
   contains the username and password.  If it does not wish to perform
   password authentication then it responds with a NAK TLV indicating
   the rejection of the Basic-Password-Auth-Req TLV.  Upon receiving the
   response, the server indicates the success or failure of the exchange
   using an Intermediate-Result TLV.  Multiple roundtrips of password
   authentication requests and responses MAY be used to support some
   "housecleaning" functions such as password change, change pin, etc.
   before a user is authenticated.

3.3.3.  Protected Termination and Acknowledged Result Indication

   A successful TEAP Phase 2 conversation MUST always end in a
   successful Crypto-Binding TLV and Result TLV exchange.  A TEAP server
   may initiate the Crypto-Binding TLV and Result TLV exchange without
   initiating any EAP conversation in TEAP Phase 2.  After the final
   Result TLV exchange, the TLS tunnel is terminated and a clear text
   EAP-Success or EAP-Failure is sent by the server.  Peers implementing
   TEAP MUST NOT accept a clear-text EAP success or failure packet prior
   to the peer and server reaching synchronized protected result
   indication.

   The Crypto-Binding TLV exchange is used to prove that both the peer
   and server participated in the tunnel establishment and sequence of
   authentications.  It also provides verification of the TEAP type,



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   version negotiated, outer TLVs exchanged before the TLS tunnel
   establishment.  The Crypto-Binding TLV MUST be exchanged and verified
   before the final Result TLV exchange, regardless whether there is an
   inner EAP method authentication or not.  The Crypto-Binding TLV and
   Intermediate-Result TLV MUST be included to perform Cryptographic
   Binding after each successful EAP method in a sequence of one or more
   EAP methods.  The server may send the final Result TLV along with an
   Intermediate-Result TLV and a Crypto-Binding TLV to indicate its
   intention to end the conversation.  If the peer requires nothing more
   from the server, it will respond with a Result TLV indicating success
   accompanied by a Crypto-Binding TLV and Intermediate-Result TLV if
   necessary.  The server then tears down the tunnel and sends a clear
   text EAP-Success or EAP-Failure.

   If the peer receives a Result TLV indicating success from the server,
   but its authentication policies are not satisfied (for example it
   requires a particular authentication mechanism be run or it wants to
   request a PAC), it may request further action from the server using
   the Request-Action TLV.  The Request-Action TLV is sent with a Status
   field indicating what EAP Success/Failure result the peer would
   expect if the requested action is not granted.  The value of the
   Action field indicates what the peer would like to do next.  The
   format and values for the Request-Action TLV are defined in
   Section 4.2.9.

   Upon receiving the Request-Action TLV the server may process the
   request or ignore it, based on its policy.  If the server ignores the
   request, it proceeds with termination of the tunnel and send the
   clear text EAP Success or Failure message based on the Status field
   of the peer's Request-Action TLV.  If the server honors and processes
   the request, it continues with the requested action.  The
   conversation completes with a Result TLV exchange.  The Result TLV
   may be included with the TLV that completes the requested action.

   Error handling for Phase 2 is discussed in Section 3.6.3.

3.4.  Determining Peer-Id and Server-Id

   The Peer-Id and Server-Id [RFC5247] may be determined based on the
   types of credentials used during either the TEAP tunnel creation or
   authentication.  In the case of multiple peer authentications, all
   authenticated peer identities and their corresponding identity types
   (Section 4.2.3) need to be exported.  In the case of multiple server
   authentications, all authenticated server identities need to be
   exported.

   When X.509 certificates are used for peer authentication, the Peer-Id
   is determined by the subject or subjectAltName fields in the peer



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   certificate.  As noted in [RFC5280]:

      The subject field identifies the entity associated with the public
      key stored in the subject public key field.  The subject name MAY
      be carried in the subject field and/or the subjectAltName
      extension....  If subject naming information is present only in
      the subjectAltName extension (e.g., a key bound only to an email
      address or URI), then the subject name MUST be an empty sequence
      and the subjectAltName extension MUST be critical.

      Where it is non-empty, the subject field MUST contain an X.500
      distinguished name (DN).

   If an inner EAP method is run, then the Peer-Id is obtained from the
   inner method.

   When the server uses an X.509 certificate to establish the TLS
   tunnel, the Server-Id is determined in a similar fashion as stated
   above for the Peer-Id; e.g., the subject or subjectAltName field in
   the server certificate defines the Server-Id.

3.5.  TEAP Session Identifier

   The EAP session identifier [RFC5247] is constructed using the tls-
   unique from the phase 1 outer tunnel at the beginning of phase 2 as
   defined by section 3.1 of [RFC5929].  The Session-Id is defined as
   follows:

      Session-Id = teap_type || tls-unique

      where teap_type is the EAP method type assigned to TEAP.

      tls-unique = tls-unique from the phase 1 outer tunnel at the
      beginning of phase 2 as defined by section 3.1 of [RFC5929].

3.6.  Error Handling

   TEAP uses the following error handling rules summarized below:

   1.  Errors in the outer EAP packet layer are handled as defined in
       Section 3.6.1.

   2.  Errors in the TLS layer are communicated via TLS alert messages
       in all phases of TEAP.

   3.  The Intermediate-Result TLVs carry success or failure indications
       of the individual EAP methods in TEAP Phase 2.  Errors within the
       EAP conversation in Phase 2 are expected to be handled by



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       individual EAP methods.

   4.  Violations of the Inner TLV rules are handled using Result TLVs
       together with Error TLVs.

   5.  Tunnel compromised errors (errors caused by Crypto-Binding failed
       or missing) are handled using Result TLVs and Error TLVs.

3.6.1.  Outer Layer Errors

   Errors on the TEAP outer packet layer are handled in the following
   ways:

   1.  If Outer TLVs are invalid or contain unknown values, they will be
       ignored.

   2.  If other fields (version, length, flags, etc.) are wrong, the
       entire TEAP packet will be ignored.

3.6.2.  TLS Layer Errors

   If the TEAP server detects an error at any point in the TLS Handshake
   or the TLS layer, the server SHOULD send a TEAP request encapsulating
   a TLS record containing the appropriate TLS alert message rather than
   immediately terminating the conversation so as to allow the peer to
   inform the user of the cause of the failure and possibly allow for a
   restart of the conversation.  The peer MUST send a TEAP response to
   an alert message.  The EAP-Response packet sent by the peer may
   encapsulate a TLS ClientHello handshake message, in which case the
   TEAP server MAY allow the TEAP conversation to be restarted, or it
   MAY contain a TEAP response with a zero-length message, in which case
   the server MUST terminate the conversation with an EAP-Failure
   packet.  It is up to the TEAP server whether to allow restarts, and
   if so, how many times the conversation can be restarted.  Per TLS
   [RFC5226], TLS restart is only allowed for non-fatal alerts.  A TEAP
   server implementing restart capability SHOULD impose a limit on the
   number of restarts, so as to protect against denial-of-service
   attacks.  If the TEAP server does not allow restarts, it MUST
   terminate the conversation with an EAP-Failure packet.

   If the TEAP peer detects an error at any point in the TLS layer, the
   TEAP peer should send a TEAP response encapsulating a TLS record
   containing the appropriate TLS alert message.  The server may restart
   the conversation by sending an TEAP request packet encapsulating the
   TLS HelloRequest handshake message.  The peer may allow the TEAP
   conversation to be restarted or it may terminate the conversation by
   sending an TEAP response with an zero-length message.




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3.6.3.  Phase 2 Errors

   Any time the peer or the server finds a fatal error outside of the
   TLS layer during Phase 2 TLV processing, it MUST send a Result TLV of
   failure and an Error TLV with the appropriate error code.  For errors
   involving the processing of the sequence of exchanges, such as a
   violation of TLV rules (e.g., multiple EAP-Payload TLVs), the error
   code is Unexpected_TLVs_Exchanged.  For errors involving a tunnel
   compromise, the error-code is Tunnel_Compromise_Error.  Upon sending
   a Result TLV with a fatal Error TLV the sender terminates the TLS
   tunnel.  Note that a server will still wait for a message from the
   peer after it sends a failure, however the server does not need to
   process the contents of the response message.

   For inner method, retransmission is not needed and SHOULD NOT be
   attempted, as the outer TLS tunnel can be considered a reliable
   transport.  If there is a non-fatal error handling the inner method,
   instead of silently dropping the inner method request or response and
   not responding, the receiving side should use an Error TLV with error
   code Inner_Method_Error to indicate error processing the current
   inner method.  The side receiving the Error TLV MAY decide to start a
   new inner method instead or send back a Result TLV to terminate the
   TEAP authentication session.

   If a server receives a Result TLV of failure with a fatal Error TLV,
   it MUST send a clear text EAP-Failure.  If a peer receives a Result
   TLV of failure, it MUST respond with a Result TLV indicating failure.
   If the server has sent a Result TLV of failure, it ignores the peer
   response, and it MUST send a clear text EAP-Failure.

3.7.  Fragmentation

   A single TLS record may be up to 16384 octets in length, but a TLS
   message may span multiple TLS records, and a TLS certificate message
   may in principle be as long as 16 MB.  This is larger than the
   maximum size for a message on most media types, therefore it is
   desirable to support fragmentation.  Note that in order to protect
   against reassembly lockup and denial-of-service attacks, it may be
   desirable for an implementation to set a maximum size for one such
   group of TLS messages.  Since a typical certificate chain is rarely
   longer than a few thousand octets, and no other field is likely to be
   anywhere near as long, a reasonable choice of maximum acceptable
   message length might be 64 KB.  This is still a fairly large message
   packet size so an TEAP implementation MUST provide its own support
   for fragmentation and reassembly.

   Since EAP is a lock-step protocol, fragmentation support can be added
   in a simple manner.  In EAP, fragments that are lost or damaged in



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   transit will be retransmitted, and since sequencing information is
   provided by the Identifier field in EAP, there is no need for a
   fragment offset field.

   TEAP fragmentation support is provided through the addition of flag
   bits within the EAP-Response and EAP-Request packets, as well as a
   TLS Message Length field of four octets.  Flags include the Length
   included (L), More fragments (M), and TEAP Start (S) bits.  The L
   flag is set to indicate the presence of the four-octet TLS Message
   Length field, and MUST be set for the first fragment of a fragmented
   TLS message or set of messages.  It MUST NOT be present for any other
   message.  The M flag is set on all but the last fragment.  The S flag
   is set only within the TEAP start message sent from the EAP server to
   the peer.  The TLS Message Length field is four octets, and provides
   the total length of the TLS message or set of messages that is being
   fragmented; this simplifies buffer allocation.

   When a TEAP peer receives an EAP-Request packet with the M bit set,
   it MUST respond with an EAP-Response with EAP-Type of TEAP and no
   data.  This serves as a fragment ACK.  The EAP server MUST wait until
   it receives the EAP-Response before sending another fragment.  In
   order to prevent errors in processing of fragments, the EAP server
   MUST increment the Identifier field for each fragment contained
   within an EAP-Request, and the peer MUST include this Identifier
   value in the fragment ACK contained within the EAP-Response.
   Retransmitted fragments will contain the same Identifier value.

   Similarly, when the TEAP server receives an EAP-Response with the M
   bit set, it responds with an EAP-Request with EAP-Type of TEAP and no
   data.  This serves as a fragment ACK.  The EAP peer MUST wait until
   it receives the EAP-Request before sending another fragment.  In
   order to prevent errors in the processing of fragments, the EAP
   server MUST increment the Identifier value for each fragment ACK
   contained within an EAP-Request, and the peer MUST include this
   Identifier value in the subsequent fragment contained within an EAP-
   Response.

3.8.  Peer Services

   Several TEAP services including server unauthenticated provisioning,
   PAC provisioning, certificate provisioning and channel binding depend
   on the peer trusting the TEAP server.  Peers MUST mutually
   authenticate the server before these peer services are used.

   TEAP peers MUST track whether mutual authentication has taken place.
   Mutual authentication results if the peer trusts the provided server
   certificate belongs to the server; typically this involves both
   validating the certificate to a trust anchor and confirming the



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   entity named by the certificate is the intended server.  Mutual
   authentication also results when the procedures of Section 3.3 are
   used to resume a session in which the server was previously mutually
   authenticated.  Alternatively, if an inner EAP method providing
   mutual authentication and an Extended Master Session Key (EMSK) is
   executed and cryptographic binding with the EMSK compound MAC present
   (Section 4.2.13), then the session is mutually authenticated and peer
   services can be used.  TEAP implementations SHOULD NOT use peer
   services by default unless the session is mutually authenticated.
   TEAP implementations SHOULD have a configuration where authentication
   fails if mutual authentication cannot be achieved.

   An additional complication arises when a tunnel method authenticates
   multiple parties such as authenticating both the peer machine and the
   peer user to the EAP server.  Depending on how mutual authentication
   is achieved, only some of these parties may have confidence in it.
   For example if a strong shared secret is used to mutually
   authenticate the user and the EAP server, the machine may not have
   confidence that the EAP server is the authenticated party if the
   machine cannot trust the user not to disclose the shared secret to an
   attacker.  In these cases, the parties who have achieved mutual
   authentication need to be considered when evaluating whether to use
   peer services.

3.8.1.  PAC Provisioning

   To request provisioning of a PAC, a peer sends a PAC TLV as defined
   in Section 4.2.12 containing a PAC Attribute as defined in
   Section 4.2.12.1 of PAC Type set to the appropriate value.  The
   request MAY be issued only after the peer has determined that it has
   successfully authenticated the EAP server and validated the Crypto-
   Binding TLV as defined in Section 4.2.13.  The peer MUST send
   separate PAC TLVs for each type of PAC it wants to be provisioned.
   Multiple PAC TLVs can be sent in the same packet or different
   packets.  The EAP server will send the PACs after its internal policy
   has been satisfied, or it MAY ignore the request or request
   additional authentications if its policy dictates.  The server MAY
   cache the request and provision the PACs requested after all of its
   internal policies have been satisfied.  If a peer receives a PAC with
   an unknown type, it MUST ignore it.

   A PAC-TLV containing PAC-Acknowledge attribute MUST be sent by the
   peer to acknowledge the receipt of the Tunnel PAC.  A PAC-TLV
   containing PAC-Acknowledge attribute MUST NOT be used by the peer to
   acknowledge the receipt of other types of PACs.  If the peer receives
   a PAC TLV with an unknown attribute, it SHOULD ignore the unknown
   attribute.




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3.8.2.  Certificate Provisioning Within the Tunnel

   Provisioning of a peer's certificate is supported in TEAP by
   performing the Simple PKI Request/Response from [RFC5272] using
   PKCS#10 and PKCS#7 TLVs, respectively.  A peer sends the Simple PKI
   Request using a PKCS#10 CertificateRequest [RFC2986] encoded into the
   body of a PKCS#10 TLV (see Section 4.2.17).  The TEAP Server issues a
   Simple PKI Response using a PKCS#7 [RFC2315] degenerate "certs-only"
   message encoded into the body of a PKCS#7 TLV (see Section 4.2.16),
   only after an authentication method has run and provided an identity
   proof on the peer prior to a certificate is being issued.

   In order to provide linking identity and proof-of-possession by
   including information specific to the current authenticated TLS
   session within the signed certification request, the peer generating
   the request SHOULD obtain the tls-unique value as defined in Channel
   Bindings for TLS [RFC5929] from the TLS subsystem, encode it using
   base64 encoding, and place the resulting string in the certification
   request challenge password field.  The tls-unique value used MUST be
   from the phase 1 outer tunnel at the beginning of phase 2 as defined
   by section 3.1 of [RFC5929].  The server SHOULD verify the tls-unique
   information.  This ensures that the authenticated TEAP peer is in
   possession of the private key used to sign the certification request.

   The Simple PKI Request/Response generation and processing rules of
   [RFC5272] SHALL apply to TEAP, with the exception of error
   conditions.  In the event of an error, the TEAP Server SHOULD respond
   with an Error TLV using the most descriptive error code possible; it
   MAY ignore the PKCS#10 request which generated the error.

3.8.3.  Server Unauthenticated Provisioning Mode

   In Server Unauthenticated Provisioning Mode, an unauthenticated
   tunnel is established in phase 1 and the peer and server negotiate an
   EAP method in phase 2 that supports mutual authentication and key
   derivation that is resistant to attacks such as Man-in-the-middle and
   dictionary attacks.  This provisioning mode enables the bootstrapping
   of peers when the peer lacks a strong credential usable for mutual
   authentication with the server during phase 1.  This includes both
   cases of where the cipher suite negotiated does not provide
   authentication or the cipher suite negotiated provides the
   authentication but the peer is unable to validate the identity of the
   server for some reason.

   Upon successful completion of the EAP method in phase 2, the peer and
   server exchange a Crypto-Binding TLV to bind the inner method with
   the outer tunnel and ensure that a man-in-the-middle attack has not
   been attempted.



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   Support for the Server Unauthenticated Provisioning Mode is optional.
   The cipher suite TLS_DH_anon_WITH_AES_128_CBC_SHA is RECOMMENDED when
   using server unauthenticated mode, but other anonymous ciphersuites
   MAY be supported as long as the TLS pre-master secret is generated
   from contribution from both peers.  Phase 2 EAP methods used in
   Server Unauthenticated Provisioning Mode MUST provide mutual
   authentication, key generation, and be resistant to dictionary
   attack.  Example inner methods include EAP-pwd [RFC5931] and EAP-EKE
   [RFC6124].

3.8.4.  Channel Binding

   [RFC6677] defines EAP channel bindings to solve the "lying NAS" and
   the "lying provider" problems, using a process in which the EAP peer
   gives information about the characteristics of the service provided
   by the authenticator to the AAA server protected within the EAP
   method.  This allows the server to verify the authenticator is
   providing information to the peer that is consistent with the
   information received from this authenticator as well as the
   information stored about this authenticator.

   TEAP supports EAP channel binding using the Channel-Binding TLV
   defined in Section 4.2.7.  If the TEAP server wants to request the
   channel binding information from the peer, it sends an empty Channel-
   Binding TLV to indicate the request.  The peer responds to the
   request by sending a Channel-Binding TLV containing channel binding
   message as defined in [RFC6677].  The server validates the channel
   binding message and sends back a Channel-Binding TLV with a result
   code.  If the server didn't initiate the channel binding request and
   peer still wants to send the channel binding information to the
   server, it can do that by using the Request-Action TLV along with the
   Channel-Binding TLV.Peer MUST only sends channel binding information
   after it has succ;essfully authenticated the server and established
   the protected tunnel.

4.  Message Formats

   The following sections describe the message formats used in TEAP.
   The fields are transmitted from left to right in network byte order.

4.1.  TEAP Message Format

   A summary of the TEAP Request/Response packet format is shown below.








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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |   Identifier  |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |   Flags | Ver |        Message Length         :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :         Message Length        |         Outer TLV Length
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :     Outer TLV Length          |         TLS Data...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Outer TLVs...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      Code

         The code field is one octet in length defined as follows:


         1  Request

         2  Response


      Identifier

         The Identifier field is one octet and aids in matching
         responses with requests.  The Identifier field MUST be changed
         on each Request packet.  The Identifier field in the Response
         packet MUST match the Identifier field from the corresponding
         request.


      Length

         The Length field is two octets and indicates the length of the
         EAP packet including the Code, Identifier, Length, Type, Flags,
         Ver, Message Length, TLS Data, and Outer TLVs fields.  Octets
         outside the range of the Length field should be treated as Data
         Link Layer padding and should be ignored on reception.


      Type

         TBD for TEAP




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      Flags

          0 1 2 3 4
         +-+-+-+-+-+
         |L M S O R|
         +-+-+-+-+-+

         L  Length included; set to indicate the presence of the four
            octet Message Length field.  It MUST be present for the
            first fragment of a fragmented message.  It MUST NOT be
            present for any other message

         M  More fragments; set on all but the last fragment

         S  TEAP start; set in a TEAP Start message sent from the server
            to the peer

         O  Outer TLV length included; set to indicate the presence of
            the four-octet Outer TLV Length field.  It MUST be present
            only in the initial request and response messages.  If the
            initial message is fragmented, then it MUST be present only
            on the first fragment

         R  Reserved (MUST be zero)


      Ver

         This field contains the version of the protocol.  This document
         describes version 1 (001 in binary) of TEAP.


      Message Length

         The Message Length field is four octets, and is present only if
         the L bit is set.  This field provides the total length of the
         message that may be fragmented over the data fields of multiple
         packets.


      Outer TLV Length

         The Outer TLV Length field is four octets, and is present only
         if the O bit is set.  This field provides the total length of
         the Outer TLVs if present.






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      TLS Data

         When the Data field is present, it consists of an encapsulated
         TLS packet in TLS record format.  A TEAP packet with Flags and
         Version fields, but with zero length TLS data field, is used to
         indicate TEAP acknowledgement for either a fragmented message,
         a TLS Alert message or a TLS Finished message.

      Outer TLVs

         The Outer TLVs consist of the optional data used to help
         establishing the TLS tunnel in TLV format.  They are only
         allowed in the first two messages in the TEAP protocol.  That
         is the first EAP server to peer message and first peer to EAP
         server message.  The start of the Outer TLVs can be derived
         from the EAP Length field and Outer TLV Length field.

4.2.  TEAP TLV Format and Support

   The TLVs defined here are standard Type-Length-Value (TLV) objects.
   The TLV objects could be used to carry arbitrary parameters between
   EAP peer and EAP server within the protected TLS tunnel.

   The EAP peer may not necessarily implement all the TLVs supported by
   the EAP server.  To allow for interoperability, TLVs are designed to
   allow an EAP server to discover if a TLV is supported by the EAP
   peer, using the NAK TLV.  The mandatory bit in a TLV indicates
   whether support of the TLV is required.  If the peer or server does
   not support a TLV marked mandatory, then it MUST send a NAK TLV in
   the response, and all the other TLVs in the message MUST be ignored.
   If an EAP peer or server finds an unsupported TLV that is marked as
   optional, it can ignore the unsupported TLV.  It MUST NOT send an NAK
   TLV for a TLV that is not marked mandatory.  If all TLVs in a message
   are marked optional and none are understood by the peer, then a NAK
   TLV or Result TLV could be sent to the other side in order to
   continue the conversation.

   Note that a peer or server may support a TLV with the mandatory bit
   set, but may not understand the contents.  The appropriate response
   to a supported TLV with content that is not understood is defined by
   the individual TLV specification.

   EAP implementations compliant with this specification MUST support
   TLV exchanges, as well as the processing of mandatory/optional
   settings on the TLV.  Implementations conforming to this
   specification MUST support the following TLVs:





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      Authority-ID TLV

      Identity-Type TLV

      Result TLV

      NAK TLV

      Error TLV

      Request-Action TLV

      EAP-Payload TLV

      Intermediate-Result TLV

      Crypto-Binding TLV

      Basic-Password-Auth-Req TLV

      Basic-Password-Auth-Resp TLV

4.2.1.  General TLV Format

   TLVs are defined as described below.  The fields are transmitted from
   left to right.

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Value...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M


         0  Optional TLV

         1  Mandatory TLV








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      R

         Reserved, set to zero (0)


      TLV Type

         A 14-bit field, denoting the TLV type.  Allocated Types
         include:


         0  Unassigned

         1  Authority-ID TLV (Section 4.2.2)

         2  Identity-Type TLV (Section 4.2.3)

         3  Result TLV (Section 4.2.4)

         4  NAK TLV (Section 4.2.5)

         5  Error TLV (Section 4.2.6)

         6  Channel-Binding TLV (Section 4.2.7)

         7  Vendor-Specific TLV (Section 4.2.8)

         8  Request-Action TLV (Section 4.2.9)

         9  EAP-Payload TLV (Section 4.2.10)

         10 Intermediate-Result TLV (Section 4.2.11)

         11 PAC TLV (Section 4.2.12)

         12 Crypto-Binding TLV (Section 4.2.13)

         13 Basic-Password-Auth-Req TLV (Section 4.2.14)

         14 Basic-Password-Auth-Resp TLV (Section 4.2.15)

         15 PKCS#7 TLV (Section 4.2.16)

         16 PKCS#10 TLV (Section 4.2.17)







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         17 Server-Trusted-Root TLV (Section 4.2.18)


      Length

         The length of the Value field in octets.


      Value

         The value of the TLV.

4.2.2.  Authority-ID TLV

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ID...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         Mandatory, set to (0)


      R

         Reserved, set to zero (0)


      TLV Type

         1 for Authority-ID


      Length

         The Length filed is two octets, which contains the length of
         the ID field in octets.








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      ID

         Hint of the identity of the server, to help the peer to match
         the credentials available for the server.  It should be unique
         across the deployment.

4.2.3.  Identity-Type TLV

   The Identity-Type TLV allows an EAP server to send a hint to help the
   EAP peer select the right type of identity; for example; user or
   machine.  TEAPv1 implementations MUST support this TLV.  Only one
   Identity-Type TLV SHOULD be present in the TEAP request or response
   packet.  The Identity-Type TLV request MUST come with an EAP-Payload
   TLV or Basic-Password-Auth-Req TLV.  If the EAP peer does have an
   identity corresponding to the identity type requested, then the peer
   SHOULD respond with an Identity-Type TLV with the requested type.  If
   the Identity-Type field does not contain one of the known values or
   if the EAP peer does not have an identity corresponding to the
   identity type requested, then the peer SHOULD respond with an
   Identity-Type TLV with the one of available identity types.  If the
   server receives an identity type in the response that does not match
   the requested type, then the peer does not possess the requested
   credential type and the server SHOULD proceed with authentication for
   the credential type proposed by the peer or proceed with requesting
   another credential type, or simply apply the network policy based on
   the configured policy, e.g., sending Result TLV with Failure.

   The Identity-Type TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Identity-Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         0 (Optional)


      R

         Reserved, set to zero (0)




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      TLV Type

         2 for Identity-Type TLV


      Length

         2


      Identity-Type

         The Identity-Type field is two octets.  Values include:


         1  User

         2  Machine


4.2.4.  Result TLV

   The Result TLV provides support for acknowledged success and failure
   messages for protected termination within TEAP.  If the Status field
   does not contain one of the known values, then the peer or EAP server
   MUST treat this as a fatal error of Unexpected_TLVs_Exchanged.  The
   behavior of the Result TLV is further discussed in Section 3.3.3 and
   Section 3.6.3.  A Result TLV indicating failure MUST NOT be
   accompanied by the following TLVs: NAK, EAP-Payload TLV, or Crypto-
   Binding TLV.  The Result TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Status            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         Mandatory, set to one (1)







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      R

         Reserved, set to zero (0)


      TLV Type

         3 for Result TLV


      Length

         2


      Status

         The Status field is two octets.  Values include:


         1  Success

         2  Failure


4.2.5.  NAK TLV

   The NAK TLV allows a peer to detect TLVs that are not supported by
   the other peer.  A TEAP packet can contain 0 or more NAK TLVs.  A NAK
   TLV should not be accompanied by other TLVs.  A NAK TLV MUST NOT be
   sent in response to a message containing a Result TLV, instead a
   Result TLV of failure should be sent indicating failure and an Error
   TLV of Unexpected_TLVs_Exchanged.  The NAK TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Vendor-Id                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            NAK-Type           |           TLVs...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+








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      M

         Mandatory, set to one (1)


      R


         Reserved, set to zero (0)


      TLV Type

         4 for NAK TLV


      Length

         >=6


      Vendor-Id

         The Vendor-Id field is four octets, and contains the Vendor-Id
         of the TLV that was not supported.  The high-order octet is 0
         and the low-order three octets are the Structure of Management
         Information (SMI) Network Management Private Enterprise Code of
         the Vendor in network byte order.  The Vendor-Id field MUST be
         zero for TLVs that are not Vendor-Specific TLVs.


      NAK-Type

         The NAK-Type field is two octets.  The field contains the Type
         of the TLV that was not supported.  A TLV of this Type MUST
         have been included in the previous packet.


      TLVs

         This field contains a list of zero or more TLVs, each of which
         MUST NOT have the mandatory bit set.  These optional TLVs are
         for future extensibility to communicate why the offending TLV
         was determined to be unsupported.





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4.2.6.  Error TLV

   The Error TLV allows an EAP peer or server to indicate errors to the
   other party.  A TEAP packet can contain 0 or more Error TLVs.  The
   Error-Code field describes the type of error.  Error Codes 1-999
   represent successful outcomes (informative messages), 1000-1999
   represent warnings, and codes 2000-2999 represent fatal errors.  A
   fatal Error TLV MUST be accompanied by a Result TLV indicating
   failure and the conversation is terminated as described in
   Section 3.6.3.  The Error TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Error-Code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         Mandatory, set to one (1)


      R

         Reserved, set to zero (0)


      TLV Type

         5 for Error TLV


      Length

         4


      Error-Code

         The Error-Code field is four octets.  Currently defined values
         for Error-Code include:





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            1001 Inner_Method_Error

            2001 Tunnel_Compromise_Error

            2002 Unexpected_TLVs_Exchanged

            2003 Unsupported_Algorithm_In_CertificateSigning_Request

            2004 Unsupported_Extension_In_CertificateSigning_Request

            2005 Bad_Identity_In_CertificateSigning_Request

            2006 Bad_CertificateSigning_Request

            2007 Internal_CA_Error

            2008 General_PKI_Error

4.2.7.  Channel-Binding TLV

   The Channel-Binding TLV provides a mechanism for carrying channel
   binding data from the peer to the EAP server and a channel binding
   response from the EAP server to the peer as described in [RFC6677].
   TEAPv1 implementations MAY support this TLV, which cannot be
   responded to with a NAK TLV.  If the Channel-Binding data field does
   not contain one of the known values or if the EAP server does not
   support this TLV, then the server MUST ignore the value.  The
   Channel-Binding TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Data ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         0 (Optional)


      R

         Reserved, set to zero (0)




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      TLV Type

         6 for Channel-Binding TLV


      Length

         variable


      Data

         The data field contains a channel-binding message as defined in
         section 5.3 of [RFC6677].


4.2.8.  Vendor-Specific TLV

   The Vendor-Specific TLV is available to allow vendors to support
   their own extended attributes not suitable for general usage.  A
   Vendor-Specific TLV attribute can contain one or more TLVs, referred
   to as Vendor TLVs.  The TLV-type of a Vendor-TLV is defined by the
   vendor.  All the Vendor TLVs inside a single Vendor-Specific TLV
   belong to the same vendor.  There can be multiple Vendor-Specific
   TLVs from different vendors in the same message.  Error handling in
   the Vendor TLV could use vendor's own specific error handling
   mechanism or use the standard TEAP error codes defined.

   Vendor TLVs may be optional or mandatory.  Vendor TLVs sent with
   Result TLVs MUST be marked as optional.  If the Vendor-Specific TLV
   is marked as mandatory, then it is expected that the receiving side
   needs to recognize the vendor ID, parse all Vendor TLVs within and
   deal with error handling within the Vendor-Specific TLV as defined by
   the vendor.

   The Vendor-Specific TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Vendor-Id                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Vendor TLVs....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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      M

         0 or 1


      R

         Reserved, set to zero (0)


      TLV Type

         7 for Vendor Specific TLV


      Length

         4 + cumulative length of all included Vendor TLVs


      Vendor-Id

         The Vendor-Id field is four octets, and contains the Vendor-Id
         of the TLV.  The high-order octet is 0 and the low-order 3
         octets are the SMI Network Management Private Enterprise Code
         of the Vendor in network byte order.


      Vendor TLVs

         This field is of indefinite length.  It contains vendor-
         specific TLVs, in a format defined by the vendor.

4.2.9.  Request-Action TLV

   The Request-Action TLV MAY be sent by both the peer and the server in
   response to a successful or failure Result TLV.  It allows the peer
   or server to request the other side to negotiate additional EAP
   methods or process TLVs specified in the response packet.  The
   receiving side MUST process this TLV.  The processing for the TLV is
   as follows:

      The receiving entity MAY choose to process any of the TLVs that
      are included in the message.





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      If the receiving entity chooses NOT to process any TLV in the
      list, then it sends back a Result TLV with the same code in the
      Status field of the Request-Action TLV.

      If multiple Request-Action TLVs are in the request, the session
      can continue if any of the TLVs in any Request-Action TLV is
      processed.

      If multiple Request-Action TLVs are in the request and none of
      them is processed, then the most fatal status should be used in
      the Result TLV returned.  If a status code in the Request-Action
      TLV is not understood by the receiving entity, then it should be
      treated as a fatal error.

      After processing the TLVs or EAP method in the request, another
      round of Result TLV exchange would occur to synchronize the final
      status on both sides.

   The peer or the server MAY send multiple Request-Action TLVs to the
   other side.  Two Request-Action TLVs MUST NOT occur in the same TEAP
   packet if they have the same Status value.  The order of processing
   multiple Request-Action TLVs is implementation dependent.  If the
   receiving side process the optional (non-fatal) items first, it is
   possible that the fatal items will disappear at a later time.  If the
   receiving side processes the fatal items first, the communication
   time will be shorter.

   The peer or the server MAY return a new set of Request-Action TLVs
   after one or more of the requested items has been processed and the
   other side has signaled it wants to end the EAP conversation.

   The Request-Action TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Status   |      Action    |                TLVs....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-



      M

         Mandatory set to one (1)





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      R

         Reserved, set to zero (0)


      TLV Type

         8 for Request-Action TLV


      Length

         2 + cumulative length of all included TLVs


      Status

         The Status field is one octet.  This indicates the result if
         the server does not process the action requested by the peer.
         Values include:


         1  Success

         2  Failure


      Action

         The Action field is one octet.  Values include:


         1  Process-TLV

         2  Negotiate-EAP


      TLVs

         This field is of indefinite length.  It contains TLVs that the
         peer wants the server to process.

4.2.10.  EAP-Payload TLV

   To allow piggybacking an EAP request or response with other TLVs, the
   EAP-Payload TLV is defined, which includes an encapsulated EAP packet
   and a list of optional TLVs.  The optional TLVs are provided for
   future extensibility to provide hints about the current EAP



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   authentication.  Only one EAP-Payload TLV is allowed in a message.
   The EAP-Payload TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          EAP packet...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             TLVs...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         Mandatory, set to (1)


      R

         Reserved, set to zero (0)


      TLV Type

         9 for EAP-Payload TLV


      Length

         length of embedded EAP packet + cumulative length of additional
         TLVs


      EAP packet

         This field contains a complete EAP packet, including the EAP
         header (Code, Identifier, Length, Type) fields.  The length of
         this field is determined by the Length field of the
         encapsulated EAP packet.


       TLVs

         This (optional) field contains a list of TLVs associated with
         the EAP packet field.  The TLVs MUST NOT have the mandatory bit



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         set.  The total length of this field is equal to the Length
         field of the EAP-Payload TLV, minus the Length field in the EAP
         header of the EAP packet field.

4.2.11.  Intermediate-Result TLV

   The Intermediate-Result TLV provides support for acknowledged
   intermediate Success and Failure messages between multiple inner EAP
   methods within EAP.  An Intermediate-Result TLV indicating success
   MUST be accompanied by a Crypto-Binding TLV.  The optional TLVs
   associated with this TLV are provided for future extensibility to
   provide hints about the current result.  The Intermediate-Result TLV
   is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Status            |        TLVs...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         Mandatory, set to (1)


      R

         Reserved, set to zero (0)


      TLV Type

         10 for Intermediate-Result TLV


      Length

         2 + cumulative length of the embedded associated TLVs


      Status

         The Status field is two octets.  Values include:




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         1  Success

         2  Failure


      TLVs

         This field is of indeterminate length, and contains zero or
         more of the TLVs associated with the Intermediate Result TLV.
         The TLVs in this field MUST NOT have the mandatory bit set.

4.2.12.  PAC TLV Format

   The PAC TLV provides support for provisioning the Protected Access
   Credential (PAC) defined within [RFC4851].  The PAC TLV carries the
   PAC and related information within PAC attribute fields.
   Additionally, the PAC TLV MAY be used by the peer to request
   provisioning of a PAC of the type specified in the PAC Type PAC
   attribute.  The PAC TLV MUST only be used in a protected tunnel
   providing encryption and integrity protection.  A general PAC TLV
   format is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        PAC Attributes...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



        M

             0 - Non-mandatory TLV
             1 - Mandatory TLV

        R

             Reserved, set to zero (0)

        TLV Type

             11 - PAC TLV







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        Length

             Two octets containing the length of the PAC attributes
             field in octets.

        PAC Attributes

             A list of PAC attributes in the TLV format.

4.2.12.1.  Formats for PAC Attributes

   Each PAC attribute in a PAC TLV is formatted as a TLV defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Value...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



        Type

             The Type field is two octets, denoting the attribute type.
             Allocated Types include:



                     1 - PAC-Key
                     2 - PAC-Opaque
                     3 - PAC-Lifetime
                     4 - A-ID
                     5 - I-ID
                     6 - Reserved
                     7 - A-ID-Info
                     8 - PAC-Acknowledgement
                     9 - PAC-Info
                     10 - PAC-Type

        Length

             Two octets containing the length of the Value field in
             octets.





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        Value

             The value of the PAC attribute.

4.2.12.2.  PAC-Key

   The PAC-Key is a secret key distributed in a PAC attribute of type
   PAC-Key.  The PAC-Key attribute is included within the PAC TLV
   whenever the server wishes to issue or renew a PAC that is bound to a
   key such as a Tunnel PAC.  The key is a randomly generated octet
   string, which is 48 octets in length.  The generator of this key is
   the issuer of the credential, which is identified by the Authority
   Identifier (A-ID).

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              Key                              ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      Type

         1 - PAC-Key

      Length

         2-octet length indicating the length of the key

      Key

         The value of the PAC-Key.

4.2.12.3.  PAC-Opaque

   The PAC-Opaque attribute is included within the PAC TLV whenever the
   server wishes to issue or renew a PAC.

   The PAC-Opaque is opaque to the peer and thus the peer MUST NOT
   attempt to interpret it.  A peer that has been issued a PAC-Opaque by
   a server stores that data and presents it back to the server
   according to its PAC Type.  The Tunnel PAC is used in the ClientHello
   SessionTicket extension field defined in [RFC5077].  If a peer has



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   opaque data issued to it by multiple servers, then it stores the data
   issued by each server separately according to the A-ID.  This
   requirement allows the peer to maintain and use each opaque datum as
   an independent PAC pairing, with a PAC-Key mapping to a PAC-Opaque
   identified by the A-ID.  As there is a one-to-one correspondence
   between the PAC-Key and PAC-Opaque, the peer determines the PAC-Key
   and corresponding PAC-Opaque based on the A-ID provided in the TEAP/
   Start message and the A-ID provided in the PAC-Info when it was
   provisioned with a PAC-Opaque.

   The PAC-Opaque attribute format is summarized 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Value ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      Type

         2 - PAC-Opaque

      Length

         The Length filed is two octets, which contains the length of
         the Value field in octets.

      Value

         The Value field contains the actual data for the PAC-Opaque.
         It is specific to the server implementation.

4.2.12.4.  PAC-Info

   The PAC-Info is comprised of a set of PAC attributes as defined in
   Section 4.2.12.1.  The PAC-Info attribute MUST contain the A-ID,
   A-ID-Info, and PAC-Type attributes.  Other attributes MAY be included
   in the PAC-Info to provide more information to the peer.  The PAC-
   Info attribute MUST NOT contain the PAC-Key, PAC-Acknowledgement,
   PAC-Info, or PAC-Opaque attributes.  The PAC-Info attribute is
   included within the PAC TLV whenever the server wishes to issue or
   renew a PAC.





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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Attributes...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      Type

         9 - PAC-Info

      Length

         2-octet Length field containing the length of the attributes
         field in octets.

      Attributes

         The attributes field contains a list of PAC attributes.  Each
         mandatory and optional field type is defined as follows:

         3 - PAC-LIFETIME

            This is a 4-octet quantity representing the expiration time
            of the credential expressed as the number of seconds,
            excluding leap seconds, after midnight UTC, January 1, 1970.
            This attribute MAY be provided to the peer as part of the
            PAC-Info.

         4 - A-ID

            The A-ID is the identity of the authority that issued the
            PAC.  The A-ID is intended to be unique across all issuing
            servers to avoid namespace collisions.  The A-ID is used by
            the peer to determine which PAC to employ.  The A-ID is
            treated as an opaque octet string.  This attribute MUST be
            included in the PAC-Info attribute.  The A-ID MUST match the
            Authority-ID the server used to establish the tunnel.  One
            method for generating the A-ID is to use a high-quality
            random number generator to generate a random number.  An
            alternate method would be to take the hash of the public key
            or public key certificate belonging a server represented by
            the A-ID.





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         5 - I-ID

            Initiator identifier (I-ID) is the peer identity associated
            with the credential.  This identity is derived from the
            inner authentication or from the client-side authentication
            during tunnel establishment if inner authentication is not
            used.  The server employs the I-ID in the TEAP phase 2
            conversation to validate that the same peer identity used to
            execute TEAP phase 1 is also used in at minimum one inner
            authentication in TEAP phase 2.  If the server is enforcing
            the I-ID validation on the inner authentication, then the
            I-ID MUST be included in the PAC-Info, to enable the peer to
            also enforce a unique PAC for each unique user.  If the I-ID
            is missing from the PAC-Info, it is assumed that the Tunnel
            PAC can be used for multiple users and the peer will not
            enforce the unique-Tunnel-PAC-per-user policy.

         7 - A-ID-Info

            Authority Identifier Information is intended to provide a
            user-friendly name for the A-ID.  It may contain the
            enterprise name and server name in a human-readable format.
            This TLV serves as an aid to the peer to better inform the
            end-user about the A-ID.  The name is encoded in UTF-8
            [RFC3629] format.  This attribute MUST be included in the
            PAC-Info.

         10 - PAC-type

            The PAC-Type is intended to provide the type of PAC.  This
            attribute SHOULD be included in the PAC-Info.  If the PAC-
            Type is not present, then it defaults to a Tunnel PAC (Type
            1).

4.2.12.5.  PAC-Acknowledgement TLV

   The PAC-Acknowledgement is used to acknowledge the receipt of the
   Tunnel PAC by the peer.  The peer includes the PAC-Acknowledgement
   TLV in a PAC-TLV sent to the server to indicate the result of the
   processing and storing of a newly provisioned Tunnel PAC.  This TLV
   is only used when Tunnel PAC is provisioned.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Result             |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      Type

         8 - PAC-Acknowledgement

      Length

         The length of this field is two octets containing a value of 2.

      Result

         The resulting value MUST be one of the following:



               1 - Success
               2 - Failure

4.2.12.6.  PAC-Type TLV

   The PAC-Type TLV is a TLV intended to specify the PAC type.  It is
   included in a PAC-TLV sent by the peer to request PAC provisioning
   from the server.  Its format is described below:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type               |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         PAC Type              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      Type

         10 - PAC-Type

      Length

         2-octet Length field with a value of 2







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      PAC Type

         This 2-octet field defines the type of PAC being requested or
         provisioned.  The following values are defined:



               1 - Tunnel PAC

4.2.13.  Crypto-Binding TLV

   The Crypto-Binding TLV is used to prove that both the peer and server
   participated in the tunnel establishment and sequence of
   authentications.  It also provides verification of the TEAP type,
   version negotiated, outer TLVs exchanged before the TLS tunnel
   establishment.

   The Crypto-Binding TLV MUST be exchanged and verified before the
   final Result TLV exchange, regardless whether there is an inner EAP
   method authentication or not.  It MUST be included with the
   Intermediate-Result TLV to perform Cryptographic Binding after each
   successful EAP method in a sequence of EAP methods, before proceeding
   with another inner EAP method.

   The Crypto-Binding TLV is valid only if the following checks pass:

   o  The Crypto-Binding TLV version is supported

   o  The MAC verifies correctly

   o  The received version in the Crypto-Binding TLV matches the version
      sent by the receiver during the EAP version negotiation

   o  The subtype is set to the correct value

   If any of the above checks fails, then the TLV is invalid.  An
   invalid Crypto-Binding TLV is a fatal error and is handled as
   described in Section 3.6.3

   The Crypto-Binding TLV is defined as follows:











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    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Reserved   |    Version    |  Received Ver.| Flags|Sub-Type|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                             Nonce                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                   EMSK Compound MAC                           ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                    MSK Compound MAC                           ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         Mandatory, set to (1)


      R

         Reserved, set to zero (0)


      TLV Type

         12 for Crypto-Binding TLV


      Length

         56


      Reserved

         Reserved, set to zero (0)






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      Version

         The Version field is a single octet, which is set to the
         version of Crypto-Binding TLV the TEAP method is using.  For an
         implementation compliant with this version of TEAP, the version
         number MUST be set to 1.


      Received Version

         The Received Version field is a single octet and MUST be set to
         the TEAP version number received during version negotiation.
         Note that this field only provides protection against downgrade
         attacks, where a version of EAP requiring support for this TLV
         is required on both sides.


      Flags

         The Flags field is four bits.  Defined values include


         1  EMSK Compound MAC is present

         2  MSK Compound MAC is present

         3  Both EMSK and MSK Compound MAC are present


      Sub-Type

         The Sub-Type field is four bits.  Defined values include


         0  Binding Request

         1  Binding Response


      Nonce

         The Nonce field is 32 octets.  It contains a 256-bit nonce that
         is temporally unique, used for compound MAC key derivation at
         each end.  The nonce in a request MUST have its least
         significant bit set to 0 and the nonce in a response MUST have
         the same value as the request nonce except the least
         significant bit MUST be set to 1.




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      EMSK Compound MAC

         The EMSK Compound MAC field is 20 octets.  This can be the
         Server MAC (B1_MAC) or the Client MAC (B2_MAC).  The
         computation of the MAC is described in Section 5.3.

      MSK Compound MAC

         The MSK Compound MAC field is 20 octets.  This can be the
         Server MAC (B1_MAC) or the Client MAC (B2_MAC).  The
         computation of the MAC is described in Section 5.3.

4.2.14.  Basic-Password-Auth-Req TLV

   The Basic-Password-Auth-Req TLV is used by the authentication server
   to request a username and password from the peer.  It contains an
   optional user prompt message for the request.  The peer is expected
   to obtain the username and password and send them in a Basic-
   Password-Auth-Resp TLV.

   The Basic-Password-Auth-Req TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Prompt ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




      M

         0 (Optional)


      R

         Reserved, set to zero (0)


      TLV Type

         13 for Basic-Password-Auth-Req TLV





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      Length

         variable


      Prompt

         optional user prompt message in UTF-8 format


4.2.15.  Basic-Password-Auth-Resp TLV

   The Basic-Password-Auth-Resp TLV is used by the peer to respond to a
   Basic-Password-Auth-Req TLV with a username and password.  The TLV
   contains a username and password.  The username and password are in
   UTF-8 format.

   The Basic-Password-Auth-Resp TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Userlen     |             Username
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         ...     Username    ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Passlen     |             Password
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         ...     Password    ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



      M

         0 (Optional)


      R

         Reserved, set to zero (0)








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      TLV Type

         14 for Basic-Password-Auth-Resp TLV


      Length

         variable


      Userlen

         Length of Username field in octets


      Username

         Username in UTF-8 format


      Passlen

         Length of Password field in octets


      Password

         Password in UTF-8 format


4.2.16.  PKCS#7 TLV

   The PKCS#7 TLV is used by the EAP server to deliver (a)
   certificate(s) to the peer.  The format consists of a certificate or
   certificate chain in a degenerate certificates-only PKCS#7 SignedData
   Content as defined in [RFC5652].  When used in response to a Trusted-
   Server-Root TLV request from the peer, the EAP server MUST send the
   PKCS#7 TLV inside a Trusted-Server-Root TLV.  When used in response
   to a PKCS#10 certificate enrollment request from the peer, the EAP
   server MUST send the PKCS#7 TLV without a Trusted-Server-Root TLV.
   The PKCS#7 TLV is always marked as optional, which cannot be
   responded to with a NAK TLV.  TEAP implementations that support the
   Trusted-Server-Root TLV or the PKCS#10 TLV MUST support this TLV.
   Peers MUST NOT assume that the certificates in a PKCS#7 TLV are in
   any order.  TEAP Servers SHOULD include all intermediate certificates
   needed to form complete certificate paths to one or more trust
   anchors, and not just return the newly issued certificate(s).  TEAP
   Servers MAY return CRLs in the CRL bag.  TEAP Servers MAY return



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   self-signed certificates.  Peers that handle self-signed certificates
   or trust anchors MUST NOT implicitly trust these certificates merely
   due to their presence in the certificate bag.  Note: Peer's are
   advised to take great care in deciding whether to use a received
   certificate as a trust anchor.  The authenticated nature of the
   tunnel in which a PKCS#7 bag is received can provide a level of
   authenticity to the certificates contained therein.  Peers are
   advised to take into account the implied authority of the EAP server
   and to constrain the trust it can achieve through the trust anchor
   received in a PKCS#7 TLV.

   The PKCS#7 TLV is defined 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 #7 Data...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-



      M

         0 - Optional TLV

      R

         Reserved, set to zero (0)

      TLV Type

         15 - PKCS#7 TLV

      Length

         The length of the PKCS #7 Data field.

      PKCS #7 Data

         This field contains the X.509 certificate or certificate chain
         in a Certificates-Only PKCS#7 SignedData message.








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4.2.17.  PKCS#10 TLV

   The PKCS#10 TLV is used by the peer to initiate the "simple PKI"
   Request/Response from [RFC5272].  The format of the request is as
   specified in Section 6.4 of [RFC4945].  The PKCS#10 TLV is always
   marked as optional, which cannot be responded to with a NAK TLV.

   The PKCS#10 TLV is defined 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...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-



      M

         0 - Optional TLV

      R

         Reserved, set to zero (0)

      TLV Type

         16 - PKCS#10 TLV

      Length

         The length of the PKCS #10 Data field.

      PKCS #10 Data

         This field contains the PKCS#10 certificate request.

4.2.18.  Trusted-Server-Root TLV

   Trusted-Server-Root TLV facilitates the request and delivery of a
   trusted server root certificate.  The Trusted-Server-Root TLV can be
   exchanged in regular TEAP authentication mode or provisioning mode.
   The Trusted-Server-Root TLV is always marked as optional, and cannot
   be responded to with a Negative Acknowledgement (NAK) TLV.  The
   Trusted-Server-Root TLV MUST only be sent as an inner TLV (inside the
   protection of the tunnel).



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   After the peer has determined that it has successfully authenticated
   the EAP server and validated the Crypto-Binding TLV, it MAY send one
   or more Trusted-Server-Root TLVs (marked as optional) to request the
   trusted server root certificates from the EAP server.  The EAP server
   MAY send one or more root certificates with a Public Key
   Cryptographic System #7 (PKCS#7) TLV inside Server-Trusted-Root TLV.
   The EAP server MAY also choose not to honor the request.

   The Trusted-Server-Root TLV allows the peer to send a request to the
   EAP server for a list of trusted roots.  The server may respond with
   one or more root certificates in PKCS#7 [RFC2315] format.

   If the EAP server sets the credential format to PKCS#7-Server-
   Certificate-Root, then the Trusted-Server-Root TLV should contain the
   root of the certificate chain of the certificate issued to the EAP
   server packaged in a PKCS#7 TLV.  If the Server certificate is a
   self-signed certificate, then the root is the self-signed
   certificate.

   If the Trusted-Server-Root TLV credential format contains a value
   unknown to the peer, then the EAP peer should ignore the TLV.

   The Trusted-Server-Root TLV is defined 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Credential-Format   |     Cred TLVs...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-



        M

             0 - Non-mandatory TLV

        R

             Reserved, set to zero (0)

        TLV Type

             17 - Trusted-Server-Root TLV [RFC4851]






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        Length

             >=2 octets

        Credential-Format

             The Credential-Format field is two octets.  Values include:

                  1 - PKCS#7-Server-Certificate-Root

        Cred TLVs

             This field is of indefinite length.  It contains TLVs
             associated with the credential format.  The peer may leave
             this field empty when using this TLV to request server
             trust roots.

4.3.  TLV Rules

   To save round trips, multiple TLVs can be sent in the single TEAP
   packet.  However, multiple EAP Payload TLVs, or multiple Basic
   Password Authentication TLVs, or an EAP Payload TLV with a Basic
   Password Authentication TLV within one single TEAP packet, is not
   supported in this version and MUST NOT be sent.  If the peer or EAP
   server receives multiple EAP Payload TLVs, then it MUST terminate the
   connection with the Result TLV.  The order of TLVs in TEAP does not
   matter, except one should always process the Identity-Type TLV before
   processing the EAP TLV or Basic Password Authentication TLV as the
   Identity-Type TLV is a hint to the type of identity that is to be
   authenticated.

   The following table defines the meaning of the table entries in the
   sections below:

   0 This TLV MUST NOT be present in the message.

   0+ Zero or more instances of this TLV MAY be present in the message.

   0-1 Zero or one instance of this TLV MAY be present in the message.

   1 Exactly one instance of this TLV MUST be present in the message.

4.3.1.  Outer TLVs

   The following table provides a guide to which TLVs may be included in
   the TEAP packet outside the TLS channel, which kind of packets, and
   in what quantity:




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   Request  Response    Success   Failure   TLVs
   0-1      0           0         0         Authority-ID
   0-1      0-1         0         0         Identity-Type
   0+       0+          0         0         Vendor-Specific

   Outer-TLVs MUST be marked as optional.  Vendor-TLVs inside Vendor-
   Specific TLV MUST be marked as optional when included in Outer TLVs.
   Outer-TLVs MUST NOT be included in messages after the first two TEAP
   messages sent by peer and EAP-server respectively.  That is the first
   EAP server to peer message and first peer to EAP server message.  If
   the message is fragmented, the whole set of messages is counted as
   one message.  If Outer-TLVs are included in messages after the first
   two TEAP messages, they MUST be ignored.

4.3.2.  Inner TLVs

   The following table provides a guide to which inner TLVs may be
   encapsulated in TLS in TEAP Phase 2, in which kind of packets, and in
   what quantity.  The messages are as follows: Request is a TEAP
   Request, Response is a TEAP Response, Success is a message containing
   a successful Result TLV, and Failure is a message containing a failed
   Result TLV.

   Request  Response    Success   Failure   TLVs
   0-1      0-1         0         0         Identity-Type
   0-1      0-1         1         1         Result
   0+       0+          0         0         NAK
   0+       0+          0+        0+        Error
   0-1      0-1         0         0         Channel-Binding
   0+       0+          0+        0+        Vendor-Specific [NOTE1]
   0+       0+          0+        0+        Request-Action
   0-1      0-1         0         0         EAP-Payload
   0-1      0-1         0-1       0-1       Intermediate-Result
   0+       0+          0+        0         PAC-TLV
   0-1      0-1         0-1       0-1       Crypto-Binding
   0-1      0           0         0         Basic-Password-Auth-Req
   0        0-1         0         0         Basic-Password-Auth-Resp
   0-1      0           0-1       0         PKCS#7
   0        0-1         0         0         PKCS#10
   0-1      0-1         0-1       0         Server-Trusted-Root

   [NOTE1] Vendor TLVs (included in Vendor-Specific TLVs) sent with a
   Result TLV MUST be marked as optional.

5.  Cryptographic Calculations






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5.1.  TEAP Authentication Phase 1: Key Derivations

   With TEAPv1, the TLS master secret is generated as specified in TLS.
   If a PAC is used then the master secret is obtained as described in
   [RFC5077].

   TEAPv1 makes use of the TLS Keying Material Exporters defined in
   [RFC5705] to derive the session_key_seed.  The Label used in the
   derivation is "EXPORTER: teap session key seed".  The length of the
   session key seed material is 40 octets.  No context data is used in
   the export process.

   The session_key_seed is used by the TEAP Authentication Phase 2
   conversation to both cryptographically bind the inner method(s) to
   the tunnel as well as generate the resulting TEAP session keys.  The
   other quantities are used as they are defined in [RFC5246].

5.2.  Intermediate Compound Key Derivations

   The session_key_seed derived as part of TEAP Phase 2 is used in TEAP
   Phase 2 to generate an Intermediate Compound Key (IMCK) used to
   verify the integrity of the TLS tunnel after each successful inner
   authentication and in the generation of Master Session Key (MSK) and
   Extended Master Session Key (EMSK) defined in [RFC3748].  Note that
   the IMCK MUST be recalculated after each successful inner EAP method.

   The first step in these calculations is the generation of the base
   compound key, IMCK[n] from the session_key_seed and any session keys
   derived from the successful execution of nth inner EAP methods.  The
   inner EAP method(s) may provide Inner Method Session Keys (IMSK),
   IMSK1..IMSKn, corresponding to inner method 1 through n.

   If an inner method supports export of an Extended Master Session Key
   (EMSK), then the IMSK SHOULD be derived from the EMSK as defined in
   [RFC5295].  The usage label used is "TEAPbindkey@ietf.org" and the
   length is 64 octets.  Optional data parameter is not used in the
   derivation.

      IMSK = First 32 octets of KDF(EMSK, "TEAPbindkey@ietf.org" | "\0"
      | 64)

      where "|" denotes concatenation, "EMSK" consists of the 4 ASCII
      values for the letters, "\0" = is a NULL octet (0x00 in hex),
      length is the 2-octet unsigned integer in network byte order, KDF
      is defined in [RFC5295].

   If an inner method does not support export of an Extended Master
   Session Key (EMSK), then IMSK is the MSK of the inner method.  The



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   MSK is truncated at 32 octets if it is longer than 32 octets or
   padded to a length of 32 octets with zeros if it is less than 32
   octets.

   However, it's possible that the peer and server sides might not have
   the same capability to export EMSK.  In order to maintain maximum
   flexibility while prevent downgrading attack, the following mechanism
   is in place:

   On the sender of the Crypto-Binding TLV side:

      If the EMSK is not available, then computes the Compound MAC using
      MSK of the inner method.

      If the EMSK is available, and the sender's policy accepts MSK
      based MAC, then it computes two Compound MAC values.  The first is
      computed with the EMSK.  The second one is computed using the MSK.
      Both MACs are then sent to the other side.

      If the EMSK is available, but the sender's policy does not allow
      downgrade to MSK generated MAC, then it SHOULD only send EMSK
      based MAC.

   On the receiver of the Crypto-Binding TLV side:

      If the EMSK is not available and a MSK based Compound MAC was
      sent, validates the Compound MAC and sends back a MSK based
      Compound MAC response.

      If the EMSK is not available and no MSK based Compound MAC was
      sent, then handles like an invalid Crypto-Binding TLV with fatal
      error.

      If the EMSK is available and an EMSK based Compound MAC was sent,
      validates it and creates a response Compound MAC using the EMSK.

      If the EMSK is available, but no EMSK based Compound MAC was sent,
      and its policy accepts MSK based MAC, then validates it using the
      MSK and if successful, generates and returns a MSK based Compound
      MAC.

      If the EMSK is available, but no EMSK Compound MAC was sent, and
      its policy does not accept MSK based MAC, then it handles like an
      invalid Crypto-Binding TLV with fatal error.

   If the ith inner method does not generate an EMSK or MSK, then IMSKi
   is set to zero (e.g., MSKi = 32 octets of 0x00s).  If an inner method
   fails, then it is not included in this calculation.  The derivations



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   of S-IMCK is as follows:

      S-IMCK[0] = session_key_seed
      For j = 1 to n-1 do
           IMCK[j] = TLS-PRF(S-IMCK[j-1], "Inner Methods Compound Keys",
                IMSK[j], 60)
           S-IMCK[j] = first 40 octets of IMCK[j]
           CMK[j] = last 20 octets of IMCK[j]

   where TLS-PRF is the PRF negotiated as part of TLS handshake
   [RFC5246].

5.3.  Computing the Compound MAC

   For authentication methods that generate keying material, further
   protection against man-in-the-middle attacks is provided through
   cryptographically binding keying material established by both TEAP
   Phase 1 and TEAP Phase 2 conversations.  After each successful inner
   EAP authentication, EAP EMSK and/or MSKs are cryptographically
   combined with key material from TEAP Phase 1 to generate a compound
   session key, CMK.  The CMK is used to calculate the Compound MAC as
   part of the Crypto-Binding TLV described in Section 4.2.13, which
   helps provide assurance that the same entities are involved in all
   communications in TEAP.  During the calculation of the Compound-MAC
   the MAC field is filled with zeros.

   The Compound MAC computation is as follows:

      CMK = CMK[j]
      Compound-MAC = MAC( CMK, BUFFER )

   where j is the number of the last successfully executed inner EAP
   method, MAC is the MAC function negotiated in TLS 1.2 [RFC5246], and
   BUFFER is created after concatenating these fields in the following
   order:

   1  The entire Crypto-Binding TLV attribute with both the EMSK and MSK
      Compound MAC fields zeroed out.

   2  The EAP Type sent by the other party in the first TEAP message.

   3  All the Outer-TLVs from the first TEAP message sent by EAP server
      to peer.  If a single TEAP message is fragmented into multiple
      TEAP packets; then the Outer-TLVs in all the fragments of that
      message MUST be included.






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   4  All the Outer-TLVs from the first TEAP message sent by the peer to
      the EAP server.  If a single TEAP message is fragmented into
      multiple TEAP packets, then the Outer-TLVs in all the fragments of
      that message MUST be included.

5.4.  EAP Master Session Key Generation

   TEAP Authentication assures the master session key (MSK) and Extended
   Master Session Key (EMSK) output from the EAP method are the result
   of all authentication conversations by generating an Intermediate
   Compound Key (IMCK).  The IMCK is mutually derived by the peer and
   the server as described in Section 5.2 by combining the MSKs from
   inner EAP methods with key material from TEAP Phase 1.  The resulting
   MSK and EMSK are generated as part of the IMCKn key hierarchy as
   follows:

      MSK  = TLS-PRF(S-IMCK[j], "Session Key Generating Function", 64)
      EMSK = TLS-PRF(S-IMCK[j],
           "Extended Session Key Generating Function", 64)

   where j is the number of the last successfully executed inner EAP
   method.

   The EMSK is typically only known to the TEAP peer and server and is
   not provided to a third party.  The derivation of additional keys and
   transportation of these keys to a third party is outside the scope of
   this document.

   If no EAP methods have been negotiated inside the tunnel or no EAP
   methods have been successfully completed inside the tunnel, the MSK
   and EMSK will be generated directly from the session_key_seed meaning
   S-IMCK = session_key_seed.

6.  IANA Considerations

   This section provides guidance to the Internet Assigned Numbers
   Authority (IANA) regarding registration of values related to the TEAP
   protocol, in accordance with BCP 26, [RFC5226].

   The EAP Method Type number for TEAP needs to be assigned.

   The document defines a registry for TEAP TLV types, which may be
   assigned by Specification Required as defined in [RFC5226].
   Section 4.2 defines the TLV types that initially populate the
   registry.  A summary of the TEAP TLV types is given below:






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      0  Unassigned

      1  Authority-ID TLV

      2  Identity-Type TLV

      3  Result TLV

      4  NAK TLV

      5  Error TLV

      6  Channel-Binding TLV

      7  Vendor-Specific TLV

      8  Request-Action TLV

      9  EAP-Payload TLV

      10 Intermediate-Result TLV

      11 PAC TLV

      12 Crypto-Binding TLV

      13 Basic-Password-Auth-Req TLV

      14 Basic-Password-Auth-Resp TLV

      15 PKCS#7 TLV

      16 PKCS#10 TLV

      17 Trusted-Server-Root TLV

   The Identity-Type defined in Section 4.2.3 contains an Identity Type
   code which is assigned on a Specification Required basis as defined
   in [RFC5226].  The initial types defined are:

   1  User

   2  Machine

   The Result TLV defined in Section 4.2.4, Request-Action TLV defined
   in Section 4.2.9, and Intermediate-Result TLV defined in



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   Section 4.2.11 contain a Status code which is assigned on a
   Specification Required basis as defined in [RFC5226].  The initial
   types defined are:

   1  Success

   2  Failure

   The Error-TLV defined in Section 4.2.6 requires an error-code.  TEAP
   Error-TLV error-codes are assigned based on Specification Required as
   defined in [RFC5226].  The initial list of error codes is as follows:

      1001 Inner_Method_Error

      2001 Tunnel_Compromise_Error

      2002 Unexpected_TLVs_Exchanged

      2003 Unsupported_Algorithm_In_CertificateSigning_Request

      2004 Unsupported_Extension_In_CertificateSigning_Request

      2005 Bad_Identity_In_CertificateSigning_Request

      2006 Bad_CertificateSigning_Request

      2007 Internal_CA_Error

      2008 General_PKI_Error

   The Request-Action TLV defined in Section 4.2.9 contains an action
   code which is assigned on a Specification Required basis as defined
   in [RFC5226].  The initial actions defined are:

   1  Process-TLV

   2  Negotiate-EAP


   The PAC Attribute defined in Section 4.2.12.1 contains a Type code
   which is assigned on a Specification Required basis as defined in
   [RFC5226].  The initial types defined are:

   1  PAC-key







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   2  PAC-Opaque

   3  PAC-Lifetime

   4  A-ID

   5  I-ID

   6  Reserved

   7  A-ID-Info

   8  PAC-Acknowledgement

   9  PAC-Info

   10 PAC-Type

   The PAC-Type defined in Section 4.2.12.6 contains a Type code which
   is assigned on a Specification Required basis as defined in
   [RFC5226].  The initial types defined are:

   1  Tunnel PAC

   The Trusted-Server-Root TLV defined in Section 4.2.18 contains a
   Credential-Format code which is assigned on a Specification Required
   basis as defined in [RFC5226].  The initial types defined are:

   1  PKCS#7-Server-Certificate-Root

   The various values under Vendor-Specific TLV are assigned by Private
   Use and do not need to be assigned by IANA.

   TEAP registers the label "EXPORTER: teap session key seed" in the TLS
   Exporter Label Registry [RFC5705].  This label is used in derivation
   as defined in Section 5.1.

   TEAP registers a TEAP binding usage label from the "USRK Key Labels"
   name space defined in [RFC5295] with a value "TEAPbindkey@ietf.org".

7.  Security Considerations

   TEAP is designed with a focus on wireless media, where the medium
   itself is inherent to eavesdropping.  Whereas in wired media, an
   attacker would have to gain physical access to the wired medium;
   wireless media enables anyone to capture information as it is
   transmitted over the air, enabling passive attacks.  Thus, physical
   security can not be assumed and security vulnerabilities are far



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   greater.  The threat model used for the security evaluation of TEAP
   is defined in the EAP [RFC3748].

7.1.  Mutual Authentication and Integrity Protection

   TEAP as a whole, provides message and integrity protection by
   establishing a secure tunnel for protecting the authentication
   method(s).  The confidentiality and integrity protection is defined
   by TLS and provides the same security strengths afforded by TLS
   employing a strong entropy shared master secret.  The integrity of
   the key generating authentication methods executed within the TEAP
   tunnel is verified through the calculation of the Crypto-Binding TLV.
   This ensures that the tunnel endpoints are the same as the inner
   method endpoints.

   The Result TLV is protected and conveys the true Success or Failure
   of TEAP, and should be used as the indicator of its success or
   failure respectively.  However, as EAP terminates with either a clear
   text EAP Success or Failure, a peer will also receive a clear text
   EAP Success or Failure.  The received clear text EAP Success or
   Failure MUST match that received in the Result TLV; the peer SHOULD
   silently discard those clear text EAP success or failure messages
   that do not coincide with the status sent in the protected Result
   TLV.

7.2.  Method Negotiation

   As is true for any negotiated EAP protocol, NAK packets used to
   suggest an alternate authentication method are sent unprotected and
   as such, are subject to spoofing.  During unprotected EAP method
   negotiation, NAK packets may be interjected as active attacks to
   negotiate down to a weaker form of authentication, such as EAP-MD5
   (which only provides one-way authentication and does not derive a
   key).  Both the peer and server should have a method selection policy
   that prevents them from negotiating down to weaker methods.  Inner
   method negotiation resists attacks because it is protected by the
   mutually authenticated TLS tunnel established.  Selection of TEAP as
   an authentication method does not limit the potential inner
   authentication methods, so TEAP should be selected when available.

   An attacker cannot readily determine the inner EAP method used,
   except perhaps by traffic analysis.  It is also important that peer
   implementations limit the use of credentials with an unauthenticated
   or unauthorized server.







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7.3.  Separation of Phase 1 and Phase 2 Servers

   Separation of the TEAP Phase 1 from the Phase 2 conversation is NOT
   RECOMMENDED.  Allowing the Phase 1 conversation to be terminated at a
   different server than the Phase 2 conversation can introduce
   vulnerabilities if there is not a proper trust relationship and
   protection for the protocol between the two servers.  Some
   vulnerabilities include:

   o  Loss of identity protection

   o  Offline dictionary attacks

   o  Lack of policy enforcement

   o  Man-in-the-middle attacks (as described in
      [I-D.ietf-emu-crypto-bind])

   There may be cases where a trust relationship exists between the
   Phase 1 and Phase 2 servers, such as on a campus or between two
   offices within the same company, where there is no danger in
   revealing the inner identity and credentials of the peer to entities
   between the two servers.  In these cases, using a proxy solution
   without end-to-end protection of TEAP MAY be used.  The TEAP
   encrypting/decrypting gateway SHOULD, at a minimum, provide support
   for IPsec or similar protection in order to provide confidentiality
   for the portion of the conversation between the gateway and the EAP
   server.  In addition, separation of the inner and outer method
   servers allows for crypto-binding based on the inner method MSK to be
   thwarted as described in [I-D.ietf-emu-crypto-bind].  Implementation
   and deployment SHOULD adopt various mitigation strategies described
   in [I-D.ietf-emu-crypto-bind].  If the inner method is deriving EMSK,
   then this threat is mitigated as TEAP utilizes the mutual crypto-
   binding based on EMSK as described in [I-D.ietf-emu-crypto-bind].

7.4.  Mitigation of Known Vulnerabilities and Protocol Deficiencies

   TEAP addresses the known deficiencies and weaknesses in the EAP
   method.  By employing a shared secret between the peer and server to
   establish a secured tunnel, TEAP enables:

   o  Per packet confidentiality and integrity protection

   o  User identity protection

   o  Better support for notification messages





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   o  Protected EAP inner method negotiation

   o  Sequencing of EAP methods

   o  Strong mutually derived master session keys

   o  Acknowledged success/failure indication

   o  Faster re-authentications through session resumption

   o  Mitigation of dictionary attacks

   o  Mitigation of man-in-the-middle attacks

   o  Mitigation of some denial-of-service attacks

   It should be noted that TEAP, as in many other authentication
   protocols, a denial-of-service attack can be mounted by adversaries
   sending erroneous traffic to disrupt the protocol.  This is a problem
   in many authentication or key agreement protocols and is therefore
   noted for TEAP as well.

   TEAP was designed with a focus on protected authentication methods
   that typically rely on weak credentials, such as password-based
   secrets.  To that extent, the TEAP Authentication mitigates several
   vulnerabilities, such as dictionary attacks, by protecting the weak
   credential-based authentication method.  The protection is based on
   strong cryptographic algorithms in TLS to provide message
   confidentiality and integrity.  The keys derived for the protection
   relies on strong random challenges provided by both peer and server
   as well as an established key with strong entropy.  Implementations
   should follow the recommendation in [RFC4086] when generating random
   numbers.

7.4.1.  User Identity Protection and Verification

   The initial identity request response exchange is sent in cleartext
   outside the protection of TEAP.  Typically the Network Access
   Identifier (NAI) [RFC4282] in the identity response is useful only
   for the realm information that is used to route the authentication
   requests to the right EAP server.  This means that the identity
   response may contain an anonymous identity and just contain realm
   information.  In other cases, the identity exchange may be eliminated
   altogether if there are other means for establishing the destination
   realm of the request.  In no case should an intermediary place any
   trust in the identity information in the identity response since it
   is unauthenticated and may not have any relevance to the
   authenticated identity.  TEAP implementations should not attempt to



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   compare any identity disclosed in the initial cleartext EAP Identity
   response packet with those Identities authenticated in Phase 2.

   Identity request-response exchanges sent after the TEAP tunnel is
   established are protected from modification and eavesdropping by
   attackers.

   Note that since TLS client certificates are sent in the clear, if
   identity protection is required, then it is possible for the TLS
   authentication to be re-negotiated after the first server
   authentication.  To accomplish this, the server will typically not
   request a certificate in the server_hello, then after the
   server_finished message is sent, and before TEAP Phase 2, the server
   MAY send a TLS hello_request.  This allows the peer to perform client
   authentication by sending a client_hello if it wants to, or send a
   no_renegotiation alert to the server indicating that it wants to
   continue with TEAP Phase 2 instead.  Assuming that the peer permits
   renegotiation by sending a client_hello, then the server will respond
   with server_hello, a certificate and certificate_request messages.
   The peer replies with certificate, client_key_exchange and
   certificate_verify messages.  Since this re-negotiation occurs within
   the encrypted TLS channel, it does not reveal client certificate
   details.  It is possible to perform certificate authentication using
   an EAP method (for example: EAP-TLS) within the TLS session in TEAP
   Phase 2 instead of using TLS handshake renegotiation.

7.4.2.  Dictionary Attack Resistance

   TEAP was designed with a focus on protected authentication methods
   that typically rely on weak credentials, such as password-based
   secrets.  TEAP mitigates dictionary attacks by allowing the
   establishment of a mutually authenticated encrypted TLS tunnel
   providing confidentiality and integrity to protect the weak
   credential based authentication method.

7.4.3.  Protection against Man-in-the-Middle Attacks

   Allowing methods to be executed both with and without the protection
   of a secure tunnel opens up a possibility of a man-in-the-middle
   attack.  To avoid man-in-the-middle attacks it is recommended to
   always deploy authentication methods with protection of TEAP.  TEAP
   provides protection from man-in-the-middle attacks even if a
   deployment chooses to execute inner EAP methods both with and without
   TEAP protection, TEAP prevents this attack in two ways:

   1.  By using the PAC-Key to mutually authenticate the peer and server
       during TEAP Authentication Phase 1 establishment of a secure
       tunnel.



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   2.  By using the keys generated by the inner authentication method
       (if the inner methods are key generating) in the crypto-binding
       exchange and in the generation of the key material exported by
       the EAP method described in Section 5.

7.4.4.  PAC Binding to User Identity

   A PAC may be bound to a user identity.  A compliant implementation of
   TEAP MUST validate that an identity obtained in the PAC-Opaque field
   matches at minimum one of the identities provided in the TEAP Phase 2
   authentication method.  This validation provides another binding to
   ensure that the intended peer (based on identity) has successfully
   completed the TEAP Phase 1 and proved identity in the Phase 2
   conversations.

7.5.  Protecting against Forged Clear Text EAP Packets

   EAP Success and EAP Failure packets are, in general, sent in clear
   text and may be forged by an attacker without detection.  Forged EAP
   Failure packets can be used to attempt to convince an EAP peer to
   disconnect.  Forged EAP Success packets may be used to attempt to
   convince a peer that authentication has succeeded, even though the
   authenticator has not authenticated itself to the peer.

   By providing message confidentiality and integrity, TEAP provides
   protection against these attacks.  Once the peer and AS initiate the
   TEAP Authentication Phase 2, compliant TEAP implementations MUST
   silently discard all clear text EAP messages, unless both the TEAP
   peer and server have indicated success or failure using a protected
   mechanism.  Protected mechanisms include TLS alert mechanism and the
   protected termination mechanism described in Section 3.3.3.

   The success/failure decisions within the TEAP tunnel indicate the
   final decision of the TEAP authentication conversation.  After a
   success/failure result has been indicated by a protected mechanism,
   the TEAP peer can process unprotected EAP Success and EAP Failure
   messages; however the peer MUST ignore any unprotected EAP success or
   failure messages where the result does not match the result of the
   protected mechanism.

   To abide by [RFC3748], the server sends a clear text EAP Success or
   EAP Failure packet to terminate the EAP conversation.  However, since
   EAP Success and EAP Failure packets are not retransmitted, the final
   packet may be lost.  While a TEAP protected EAP Success or EAP
   Failure packet should not be a final packet in a TEAP conversation,
   it may occur based on the conditions stated above, so an EAP peer
   should not rely upon the unprotected EAP success and failure
   messages.



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7.6.  Server Certificate Validation

   As part of the TLS negotiation, the server presents a certificate to
   the peer.  The peer SHOULD verify the validity of the EAP server
   certificate, and SHOULD also examine the EAP server name presented in
   the certificate, in order to determine whether the EAP server can be
   trusted.  When performing server certificate validation
   implementations MUST provide support rules in [RFC5280] for
   validating certificates against a known trust anchor.  In addition,
   implementations MUST support matching the realm portion of the peer's
   NAI against a SubjectAltName of type dNSName within the server
   certificate.  However, in certain deployments, this might not be
   turned on.  Please note that in the case where the EAP authentication
   is remoted, the EAP server will not reside on the same machine as the
   authenticator, and therefore the name in the EAP server's certificate
   cannot be expected to match that of the intended destination.  In
   this case, a more appropriate test might be whether the EAP server's
   certificate is signed by a CA controlling the intended domain and
   whether the authenticator can be authorized by a server in that
   domain.

7.7.  Tunnel PAC Considerations

   Since the Tunnel PAC is stored by the peer, special care should be
   given to the overall security of the peer.  The Tunnel PAC MUST be
   securely stored by the peer to prevent theft or forgery of any of the
   Tunnel PAC components.  In particular, the peer MUST securely store
   the PAC-Key and protect it from disclosure or modification.
   Disclosure of the PAC-Key enables an attacker to establish the TEAP
   tunnel; however, disclosure of the PAC-Key does not reveal the peer
   or server identity or compromise any other peer's PAC credentials.
   Modification of the PAC-Key or PAC-Opaque components of the Tunnel
   PAC may also lead to denial of service as the tunnel establishment
   will fail.  The PAC-Opaque component is the effective TLS ticket
   extension used to establish the tunnel using the techniques of
   [RFC5077].  Thus, the security considerations defined by [RFC5077]
   also apply to the PAC- Opaque.  The PAC-Info may contain information
   about the Tunnel PAC such as the identity of the PAC issuer and the
   Tunnel PAC lifetime for use in the management of the Tunnel PAC.  The
   PAC-Info should be securely stored by the peer to protect it from
   disclosure and modification.

7.8.  Security Claims

   This section provides the needed security claim requirement for EAP
   [RFC3748].





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   Auth. mechanism:         Certificate based, shared secret based and
                            various tunneled authentication mechanisms.

   Ciphersuite negotiation: Yes

   Mutual authentication:   Yes

   Integrity protection:    Yes, Any method executed within the TEAP
                            tunnel is integrity protected.  The
                            cleartext EAP headers outside the tunnel are
                            not integrity protected.

   Replay protection:       Yes

   Confidentiality:         Yes

   Key derivation:          Yes

   Key strength:            See Note 1 below.

   Dictionary attack prot.: Yes

   Fast reconnect:          Yes

   Cryptographic binding:   Yes

   Session independence:    Yes

   Fragmentation:           Yes

   Key Hierarchy:           Yes

   Channel binding:         Yes

   Notes

   1.  BCP 86 [RFC3766] offers advice on appropriate key sizes.  The
       National Institute for Standards and Technology (NIST) also
       offers advice on appropriate key sizes in [NIST-SP-800-57].
       [RFC3766] Section 5 advises use of the following required RSA or
       DH module and DSA subgroup size in bits, for a given level of
       attack resistance in bits.  Based on the table below, a 2048-bit
       RSA key is required to provide 128-bit equivalent key strength:








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         Attack Resistance     RSA or DH Modulus            DSA subgroup
          (bits)                  size (bits)                size (bits)
         -----------------     -----------------            ------------
            70                        947                        129
            80                       1228                        148
            90                       1553                        167
           100                       1926                        186
           150                       4575                        284
           200                       8719                        383
           250                      14596                        482

8.  Acknowledgements

   The TEAP v1 design and protocol specification is based on EAP-FAST
   [RFC4851], which included the ideas and hard efforts of Nancy Cam-
   Winget, David McGrew, Joe Salowey, Hao Zhou, Pad Jakkahalli, Mark
   Krischer, Doug Smith, and Glen Zorn of Cisco Systems, Inc.

   The TLV processing was inspired from work on the Protected Extensible
   Authentication Protocol version 2 (PEAPv2) with Ashwin Palekar, Dan
   Smith, Sean Turner and Simon Josefsson.

   Helpful review comments were provided by Russ Housley, Jari Arkko,
   Ilan Frenkel, Jeremy Steiglitz, Dan Harkins, Sam Hartman, and Jim
   Schaad.

9.  References

9.1.  Normative References

   [RFC2119]                   Bradner, S., "Key words for use in RFCs
                               to Indicate Requirement Levels", BCP 14,
                               RFC 2119, March 1997.

   [RFC3748]                   Aboba, B., Blunk, L., Vollbrecht, J.,
                               Carlson, J., and H. Levkowetz,
                               "Extensible Authentication Protocol
                               (EAP)", RFC 3748, June 2004.

   [RFC4851]                   Cam-Winget, N., McGrew, D., Salowey, J.,
                               and H. Zhou, "The Flexible Authentication
                               via Secure Tunneling Extensible
                               Authentication Protocol Method (EAP-
                               FAST)", RFC 4851, May 2007.

   [RFC5077]                   Salowey, J., Zhou, H., Eronen, P., and H.
                               Tschofenig, "Transport Layer Security
                               (TLS) Session Resumption without Server-



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                               Side State", RFC 5077, January 2008.

   [RFC5226]                   Narten, T. and H. Alvestrand, "Guidelines
                               for Writing an IANA Considerations
                               Section in RFCs", BCP 26, RFC 5226,
                               May 2008.

   [RFC5246]                   Dierks, T. and E. Rescorla, "The
                               Transport Layer Security (TLS) Protocol
                               Version 1.2", RFC 5246, August 2008.

   [RFC5295]                   Salowey, J., Dondeti, L., Narayanan, V.,
                               and M. Nakhjiri, "Specification for the
                               Derivation of Root Keys from an Extended
                               Master Session Key (EMSK)", RFC 5295,
                               August 2008.

   [RFC5705]                   Rescorla, E., "Keying Material Exporters
                               for Transport Layer Security (TLS)",
                               RFC 5705, March 2010.

   [RFC5746]                   Rescorla, E., Ray, M., Dispensa, S., and
                               N. Oskov, "Transport Layer Security (TLS)
                               Renegotiation Indication Extension",
                               RFC 5746, February 2010.

   [RFC5929]                   Altman, J., Williams, N., and L. Zhu,
                               "Channel Bindings for TLS", RFC 5929,
                               July 2010.

   [RFC6677]                   Hartman, S., Clancy, T., and K. Hoeper,
                               "Channel-Binding Support for Extensible
                               Authentication Protocol (EAP) Methods",
                               RFC 6677, July 2012.

9.2.  Informative References

   [I-D.ietf-emu-crypto-bind]  Hartman, S., Wasserman, M., and D. Zhang,
                               "EAP Mutual Cryptographic Binding",
                               draft-ietf-emu-crypto-bind-02 (work in
                               progress), February 2013.

   [IEEE.802-1X.2004]          "Local and Metropolitan Area Networks:
                               Port-Based Network Access Control",
                               IEEE Standard 802.1X, December 2004.

   [NIST-SP-800-57]            National Institute of Standards and
                               Technology, ""Recommendation for Key



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                               Management"", NIST Special Publication
                               800-57, May 2006.

   [PEAP]                      Microsoft Corporation, ""[MS-PEAP]:
                               Protected Extensible Authentication
                               Protocol (PEAP) Specification"",
                               August 2009.

   [RFC2315]                   Kaliski, B., "PKCS #7: Cryptographic
                               Message Syntax Version 1.5", RFC 2315,
                               March 1998.

   [RFC2560]                   Myers, M., Ankney, R., Malpani, A.,
                               Galperin, S., and C. Adams, "X.509
                               Internet Public Key Infrastructure Online
                               Certificate Status Protocol - OCSP",
                               RFC 2560, June 1999.

   [RFC2986]                   Nystrom, M. and B. Kaliski, "PKCS #10:
                               Certification Request Syntax
                               Specification Version 1.7", RFC 2986,
                               November 2000.

   [RFC3579]                   Aboba, B. and P. Calhoun, "RADIUS (Remote
                               Authentication Dial In User Service)
                               Support For Extensible Authentication
                               Protocol (EAP)", RFC 3579,
                               September 2003.

   [RFC3629]                   Yergeau, F., "UTF-8, a transformation
                               format of ISO 10646", STD 63, RFC 3629,
                               November 2003.

   [RFC3766]                   Orman, H. and P. Hoffman, "Determining
                               Strengths For Public Keys Used For
                               Exchanging Symmetric Keys", BCP 86,
                               RFC 3766, April 2004.

   [RFC4072]                   Eronen, P., Hiller, T., and G. Zorn,
                               "Diameter Extensible Authentication
                               Protocol (EAP) Application", RFC 4072,
                               August 2005.

   [RFC4086]                   Eastlake, D., Schiller, J., and S.
                               Crocker, "Randomness Requirements for
                               Security", BCP 106, RFC 4086, June 2005.

   [RFC4282]                   Aboba, B., Beadles, M., Arkko, J., and P.



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                               Eronen, "The Network Access Identifier",
                               RFC 4282, December 2005.

   [RFC4945]                   Korver, B., "The Internet IP Security PKI
                               Profile of IKEv1/ISAKMP, IKEv2, and
                               PKIX", RFC 4945, August 2007.

   [RFC5247]                   Aboba, B., Simon, D., and P. Eronen,
                               "Extensible Authentication Protocol (EAP)
                               Key Management Framework", RFC 5247,
                               August 2008.

   [RFC5272]                   Schaad, J. and M. Myers, "Certificate
                               Management over CMS (CMC)", RFC 5272,
                               June 2008.

   [RFC5280]                   Cooper, D., Santesson, S., Farrell, S.,
                               Boeyen, S., Housley, R., and W. Polk,
                               "Internet X.509 Public Key Infrastructure
                               Certificate and Certificate Revocation
                               List (CRL) Profile", RFC 5280, May 2008.

   [RFC5281]                   Funk, P. and S. Blake-Wilson, "Extensible
                               Authentication Protocol Tunneled
                               Transport Layer Security Authenticated
                               Protocol Version 0 (EAP-TTLSv0)",
                               RFC 5281, August 2008.

   [RFC5421]                   Cam-Winget, N. and H. Zhou, "Basic
                               Password Exchange within the Flexible
                               Authentication via Secure Tunneling
                               Extensible Authentication Protocol (EAP-
                               FAST)", RFC 5421, March 2009.

   [RFC5652]                   Housley, R., "Cryptographic Message
                               Syntax (CMS)", STD 70, RFC 5652,
                               September 2009.

   [RFC5931]                   Harkins, D. and G. Zorn, "Extensible
                               Authentication Protocol (EAP)
                               Authentication Using Only a Password",
                               RFC 5931, August 2010.

   [RFC6066]                   Eastlake, D., "Transport Layer Security
                               (TLS) Extensions: Extension Definitions",
                               RFC 6066, January 2011.

   [RFC6124]                   Sheffer, Y., Zorn, G., Tschofenig, H.,



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                               and S. Fluhrer, "An EAP Authentication
                               Method Based on the Encrypted Key
                               Exchange (EKE) Protocol", RFC 6124,
                               February 2011.

   [RFC6678]                   Hoeper, K., Hanna, S., Zhou, H., and J.
                               Salowey, "Requirements for a Tunnel-Based
                               Extensible Authentication Protocol (EAP)
                               Method", RFC 6678, July 2012.

Appendix A.  Evaluation Against Tunnel Based EAP Method Requirements

   This section evaluates all tunnel based EAP method requirements
   described in [RFC6678] against TEAP version 1.

A.1.  Requirement 4.1.1 RFC Compliance

   TEAP v1 meets this requirement by being compliant to RFC 3748, RFC
   4017, RFC 5247, and RFC 4962.  It is also compliant with the
   "cryptographic algorithm agility" requirement by leveraging TLS 1.2
   for all cryptographic algorithm negotiation.

A.2.  Requirement 4.2.1 TLS Requirements

   Requirement 4.2.1 states:

   The tunnel based method MUST support TLS version 1.2 [RFC5246] and
   may support earlier versions greater than SSL 2.0 to enable the
   possibility of backwards compatibility.

   TEAP v1 meets this requirement by mandating TLS version 1.2 support
   as defined in Section 3.2.

A.3.  Requirement 4.2.1.1.1 Cipher Suite Negotiation

   Requirement 4.2.1.1.1 states:

   Hence, the tunnel method MUST provide integrity protected cipher
   suite negotiation with secure integrity algorithms and integrity
   keys.

   TEAP v1 meets this requirement by using TLS to provide protected
   cipher suite negotiation.

A.4.  Requirement 4.2.1.1.2 Tunnel Data Protection Algorithms

   Requirement 4.2.1.1.2 states:




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   The tunnel method MUST provide at least one mandatory to implement
   cipher suite that provides the equivalent security of 128-bit AES for
   encryption and message authentication.

   TEAP v1 meets this requirement by mandating
   TLS_RSA_WITH_AES_128_CBC_SHA as a mandatory to implement cipher suite
   as defined in Section 3.2.

A.5.  Requirement 4.2.1.1.3 Tunnel Authentication and Key Establishment

   TEAP v1 meets this requirement by mandating
   TLS_RSA_WITH_AES_128_CBC_SHA as a mandatory to implement cipher suite
   which provides certificate-based authentication of the server and is
   approved by NIST.  The mandatory to implement cipher suites only
   include cipher suites that use strong cryptographic algorithms.  They
   do not include cipher suites providing mutually anonymous
   authentication or static Diffie-Hellman cipher suites as defined in
   Section 3.2.

A.6.  Requirement 4.2.1.2 Tunnel Replay Protection

   TEAP v1 meets this requirement by using TLS to provide sufficient
   replay protection.

A.7.  Requirement 4.2.1.3 TLS Extensions

   TEAP v1 meets this requirement by allowing TLS extensions, such as
   TLS Certificate Status Request extension [RFC6066] and SessionTicket
   extension [RFC5077] to be used during TLS tunnel establishment.

A.8.  Requirement 4.2.1.4 Peer Identity Privacy

   TEAP v1 meets this requirement by establishment of the TLS tunnel and
   protection of inner method specific identities.  In addition, the
   peer certificate can be sent confidentially (i.e. encrypted).

A.9.  Requirement 4.2.1.5 Session Resumption

   TEAP v1 meets this requirement by mandating support of TLS session
   resumption as defined in Section 3.2.1 and TLS Session Resume Using a
   PAC as defined in Section 3.2.2 .

A.10.  Requirement 4.2.2 Fragmentation

   TEAP v1 meets this requirement by leveraging fragmentation support
   provided by TLS as defined in Section 3.7.





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A.11.  Requirement 4.2.3 Protection of Data External to Tunnel

   TEAP v1 meets this requirement by including TEAP version number
   received in the computation of crypto-binding TLV as defined in
   Section 4.2.13.

A.12.  Requirement 4.3.1 Extensible Attribute Types

   TEAP v1 meets this requirement by using an extensible TLV data layer
   inside the tunnel as defined in Section 4.2.

A.13.  Requirement 4.3.2 Request/Challenge Response Operation

   TEAP v1 meets this requirement by allowing multiple TLVs to be sent
   in a single EAP request or response packet, while maintaining the
   half-duplex operation typical of EAP.

A.14.  Requirement 4.3.3 Indicating Criticality of Attributes

   TEAP v1 meets this requirement by having a mandatory bit in TLV to
   indicate whether it is mandatory to support or not as defined in
   Section 4.2.

A.15.  Requirement 4.3.4 Vendor Specific Support

   TEAP v1 meets this requirement by having a Vendor-Specific TLV to
   allow vendors to define their own attributes as defined in
   Section 4.2.8.

A.16.  Requirement 4.3.5 Result Indication

   TEAP v1 meets this requirement by having a Result TLV to exchange the
   final result of the EAP authentication so both the peer and server
   have a synchronized state as defined in Section 4.2.4.

A.17.  Requirement 4.3.6 Internationalization of Display Strings

   TEAP v1 meets this requirement by supporting UTF-8 format in Basic-
   Password-Auth-Req TLV as defined in Section 4.2.14 and Basic-
   Password-Auth-Resp TLV as defined in Section 4.2.15.

A.18.  Requirement 4.4 EAP Channel Binding Requirements

   TEAP v1 meets this requirement by having a Channel-Binding TLV to
   exchange the EAP channel binding data as defined in Section 4.2.7.






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A.19.  Requirement 4.5.1.1 Confidentiality and Integrity

   TEAP v1 meets this requirement by running the password authentication
   inside a protected TLS tunnel.

A.20.  Requirement 4.5.1.2 Authentication of Server

   TEAP v1 meets this requirement by mandating authentication of the
   server before establishment of the protected TLS and then running
   inner password authentication as defined in Section 3.2.

A.21.  Requirement 4.5.1.3 Server Certificate Revocation Checking

   TEAP v1 meets this requirement by supporting TLS Certificate Status
   Request extension [RFC6066] during tunnel establishment.

A.22.  Requirement 4.5.2  Internationalization

   TEAP v1 meets this requirement by supporting UTF-8 format in Basic-
   Password-Auth-Req TLV as defined in Section 4.2.14 and Basic-
   Password-Auth-Resp TLV as defined in Section 4.2.15.

A.23.  Requirement 4.5.3 Meta-data

   TEAP v1 meets this requirement by supporting Identity-Type TLV as
   defined in Section 4.2.3 to indicate whether the authentication is
   for a user or a machine.

A.24.  Requirement 4.5.4 Password Change

   TEAP v1 meets this requirement by supporting multiple Basic-Password-
   Auth-Req TLV and Basic-Password-Auth-Resp TLV exchanges within a
   single EAP authentication, which allows "housekeeping"" functions
   such as password change.

A.25.  Requirement 4.6.1 Method Negotiation

   TEAP v1 meets this requirement by supporting inner EAP method
   negotiation within the protected TLS tunnel.

A.26.  Requirement 4.6.2 Chained Methods

   TEAP v1 meets this requirement by supporting inner EAP method
   chaining within protected TLS tunnel as defined in Section 3.3.1.







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A.27.  Requirement 4.6.3 Cryptographic Binding with the TLS Tunnel

   TEAP v1 meets this requirement by supporting cryptographic binding of
   the inner EAP method keys with the keys derived from the TLS tunnel
   as defined in Section 4.2.13.

A.28.  Requirement 4.6.4 Peer Initiated

   TEAP v1 meets this requirement by supporting Request-Action TLV as
   defined in Section 4.2.9 to allow peer to initiate another inner EAP
   method.

A.29.  Requirement 4.6.5 Method Meta-data

   TEAP v1 meets this requirement by supporting Identity-Type TLV as
   defined in Section 4.2.3 to indicate whether the authentication is
   for a user or a machine.

Appendix B.  Major Differences from EAP-FAST

   This document is a new standard tunnel EAP method based on revision
   of the EAP-FAST version 1 [RFC4851] which contains improved
   flexibility, particularly for negotiation of cryptographic
   algorithms.  The major changes are:

   1.  The EAP method name have been changed from EAP-FAST to TEAP,
       hence it would require a new EAP method type to be assigned.

   2.  This version of TEAP MUST support TLS 1.2 [RFC5246].

   3.  The key derivation now makes use of TLS keying material exporters
       [RFC5705] and the PRF and hash function negotiated in TLS.  This
       is to simplify implementation and better support cryptographic
       algorithm agility.

   4.  TEAP is in full conformance with TLS Ticket extension [RFC5077]
       as described in Section 3.2.2.

   5.  Support of passing optional outer TLVs in the first two message
       exchanges, in addition to the Authority-ID TLV data in EAP-FAST.

   6.  Basic password authentication on the TLV level has been added in
       addition to the existing inner EAP method.

   7.  Additional TLV types have been defined to support EAP channel
       binding and meta-data.  They are Identity-Type TLV and Channel-
       Binding TLVs, defined in Section 4.2.




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Appendix C.  Examples

C.1.  Successful Authentication

   The following exchanges show a successful TEAP authentication with
   basic password authentication and optional PAC refreshment, the
   conversation will appear as follows:

       Authenticating Peer     Authenticator
       -------------------     -------------
                               <- EAP-Request/
                               Identity
       EAP-Response/
       Identity (MyID1) ->

                               <- EAP-Request/
                               EAP-Type=TEAP, V=1
                               (TEAP Start, S bit set, Authority-ID)

       EAP-Response/
       EAP-Type=TEAP, V=1
       (TLS client_hello with
        PAC-Opaque in SessionTicket extension)->

                               <- EAP-Request/
                               EAP-Type=TEAP, V=1
                               (TLS server_hello,
                               (TLS change_cipher_spec,
                                TLS finished)





       EAP-Response/
       EAP-Type=TEAP, V=1 ->
       (TLS change_cipher_spec,
        TLS finished)

       TLS channel established
       (messages sent within the TLS channel)

                              <- Basic-Password-Auth-Req TLV, Challenge

       Basic-Password-Auth-Resp TLV, Response with both
       user name and password) ->

       optional additional exchanges (new pin mode,



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       password change etc.) ...

                            <- Crypto-Binding TLV (Request),
                                    Result TLV (Success),
                                (Optional PAC TLV)

       Crypto-Binding TLV(Response),
       Result TLV (Success),
       (PAC TLV Acknowledgment) ->

       TLS channel torn down
       (messages sent in clear text)

                               <- EAP-Success

C.2.  Failed Authentication

   The following exchanges show a failed TEAP authentication due to
   wrong user credentials, the conversation will appear as follows:
































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       Authenticating Peer     Authenticator
       -------------------     -------------
                               <- EAP-Request/
                               Identity

       EAP-Response/
       Identity (MyID1) ->


                               <- EAP-Request/
                               EAP-Type=TEAP, V=1
                               (TEAP Start, S bit set, Authority-ID)

       EAP-Response/
       EAP-Type=TEAP, V=1
       (TLS client_hello with
        PAC-Opaque in SessionTicket extension)->

                               <- EAP-Request/
                               EAP-Type=TEAP, V=1
                               (TLS server_hello,
                               (TLS change_cipher_spec,
                                TLS finished)

       EAP-Response/
       EAP-Type=TEAP, V=1 ->
       (TLS change_cipher_spec,
        TLS finished)

       TLS channel established
       (messages sent within the TLS channel)

                              <- Basic-Password-Auth-Req TLV, Challenge

       Basic-Password-Auth-Resp TLV, Response with both
       user name and password) ->

                               <- Result TLV (Failure)

       Result TLV (Failure) ->

       TLS channel torn down
       (messages sent in clear text)

                               <- EAP-Failure






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C.3.  Full TLS Handshake using Certificate-based Cipher Suite

   In the case where an abbreviated TLS handshake is tried and failed
   and falls back to certificate based full TLS handshake occurs within
   TEAP Phase 1, the conversation will appear as follows:

      Authenticating Peer    Authenticator
      -------------------    -------------
                             <- EAP-Request/Identity
      EAP-Response/
      Identity (MyID1) ->

      // Identity sent in the clear. May be a hint to help route
         the authentication request to EAP server, instead of the
         full user identity.

                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TEAP Start, S bit set, Authority-ID)
      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_hello
      [PAC-Opaque extension])->

      // Peer sends PAC-Opaque of Tunnel PAC along with a list of
         ciphersuites supported. If the server rejects the PAC-
         Opaque, if falls through to the full TLS handshake

                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS server_hello,
                               TLS certificate,
                              [TLS server_key_exchange,]
                              [TLS certificate_request,]
                               TLS server_hello_done)
      EAP-Response/
      EAP-Type=TEAP, V=1
      ([TLS certificate,]
       TLS client_key_exchange,
      [TLS certificate_verify,]
       TLS change_cipher_spec,
       TLS finished) ->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS change_cipher_spec,
                               TLS finished,
                               EAP-Payload-TLV[EAP-Request/
                               Identity])



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      // TLS channel established
         (messages sent within the TLS channel)

      // First EAP Payload TLV is piggybacked to the TLS Finished as
         Application Data and protected by the TLS tunnel

      EAP-Payload-TLV
      [EAP-Response/Identity (MyID2)]->

      // identity protected by TLS.

                               <- EAP-Payload-TLV
                               [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X] ->

      // Method X exchanges followed by Protected Termination

                           <- Intermediate-Result-TLV (Success),
                               Crypto-Binding TLV (Request),
                               Result TLV (Success)

      Intermediate-Result-TLV (Success),
      Crypto-Binding TLV (Response),
      Result-TLV (Success) ->

      // TLS channel torn down
      (messages sent in clear text)

                              <- EAP-Success

C.4.  Client authentication during Phase 1 with identity privacy

   In the case where a certificate based TLS handshake occurs within
   TEAP Phase 1, and client certificate authentication and identity
   privacy is desired, therefore TLS renegotiation is being used to
   transmit the peer credentials in the protected TLS tunnel, the
   conversation will appear as follows:

      Authenticating Peer     Authenticator
      -------------------     -------------
                             <- EAP-Request/Identity
      EAP-Response/
      Identity (MyID1) ->

      // Identity sent in the clear. May be a hint to help route
         the authentication request to EAP server, instead of the



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         full user identity.

                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TEAP Start, S bit set, Authority-ID)
      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_hello)->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS server_hello,
                               TLS certificate,
                              [TLS server_key_exchange,]
                              [TLS certificate_request,]
                               TLS server_hello_done)
      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_key_exchange,
       TLS change_cipher_spec,
       TLS finished) ->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS change_cipher_spec,
                               TLS finished,
                               EAP-Payload-TLV[EAP-Request/
                               Identity])

      // TLS channel established
         (EAP Payload messages sent within the TLS channel)

      // peer sends TLS client_hello to request TLS renegotiation

      TLS client_hello ->


                              <- TLS server_hello,
                               TLS certificate,
                               [TLS server_key_exchange,]
                               [TLS certificate_request,]
                               TLS server_hello_done
      [TLS certificate,]
       TLS client_key_exchange,
      [TLS certificate_verify,]
       TLS change_cipher_spec,
       TLS finished ->

                              <- TLS change_cipher_spec,
                                 TLS finished,



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                                 Crypto-Binding TLV (Request),
                                 Result TLV (Success)

      Crypto-Binding TLV (Response),
      Result-TLV (Success)) ->

      //TLS channel torn down
      (messages sent in clear text)

                              <- EAP-Success


C.5.  Fragmentation and Reassembly

   In the case where TEAP fragmentation is required, the conversation
   will appear as follows:

      Authenticating Peer     Authenticator
      -------------------     -------------
                              <- EAP-Request/
                              Identity
      EAP-Response/
      Identity (MyID) ->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TEAP Start, S bit set, Authority-ID)

      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_hello)->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS server_hello,
                               TLS certificate,
                              [TLS server_key_exchange,]
                              [TLS certificate_request,]
                               TLS server_hello_done)
                              (Fragment 1: L, M bits set)

      EAP-Response/
      EAP-Type=TEAP, V=1 ->

                              <- EAP-Request/
                                 EAP-Type=TEAP, V=1
                              (Fragment 2: M bit set)
      EAP-Response/
      EAP-Type=TEAP, V=1 ->
                              <- EAP-Request/



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                              EAP-Type=TEAP, V=1
                              (Fragment 3)
      EAP-Response/
      EAP-Type=TEAP, V=1
      ([TLS certificate,]
       TLS client_key_exchange,
      [TLS certificate_verify,]
       TLS change_cipher_spec,
       TLS finished)
       (Fragment 1: L, M bits set)->

                               <- EAP-Request/
                              EAP-Type=TEAP, V=1
      EAP-Response/
      EAP-Type=TEAP, V=1
      (Fragment 2)->
                             <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS change_cipher_spec,
                               TLS finished,
                              [EAP-Payload-TLV[
                              EAP-Request/Identity]])

      // TLS channel established
         (messages sent within the TLS channel)

      // First EAP Payload TLV is piggybacked to the TLS Finished as
         Application Data and protected by the TLS tunnel

      EAP-Payload-TLV
      [EAP-Response/Identity (MyID2)]->

      // identity protected by TLS.

                               <- EAP-Payload-TLV
                               [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X] ->

      // Method X exchanges followed by Protected Termination

                           <- Intermediate-Result-TLV (Success),
                               Crypto-Binding TLV (Request),
                               Result TLV (Success)

      Intermediate-Result-TLV (Success),
      Crypto-Binding TLV (Response),



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      Result-TLV (Success) ->

      // TLS channel torn down
      (messages sent in clear text)

                              <- EAP-Success


C.6.  Sequence of EAP Methods

   When TEAP is negotiated, with a sequence of EAP method X followed by
   method Y, the conversation will occur as follows:

      Authenticating Peer     Authenticator
      -------------------     -------------
                              <- EAP-Request/
                              Identity
      EAP-Response/
      Identity (MyID1) ->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TEAP Start, S bit set, Authority-ID)

      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_hello)->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS server_hello,
                               TLS certificate,
                              [TLS server_key_exchange,]
                              [TLS certificate_request,]
                               TLS server_hello_done)
      EAP-Response/
      EAP-Type=TEAP, V=1
      ([TLS certificate,]
       TLS client_key_exchange,
      [TLS certificate_verify,]
       TLS change_cipher_spec,
       TLS finished) ->
                             <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS change_cipher_spec,
                               TLS finished,
                               Identity-Type TLV,
                              EAP-Payload-TLV[
                              EAP-Request/Identity])




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      // TLS channel established
         (messages sent within the TLS channel)

      // First EAP Payload TLV is piggybacked to the TLS Finished as
         Application Data and protected by the TLS tunnel

      Identity_Type TLV
      EAP-Payload-TLV
      [EAP-Response/Identity] ->

                              <- EAP-Payload-TLV
                            [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X] ->

             // Optional additional X Method exchanges...

                             <- EAP-Payload-TLV
                            [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X]->

                              <- Intermediate Result TLV (Success),
                               Crypto-Binding TLV (Request),
                               Identity-Type TLV,
                               EAP Payload TLV [EAP-Type=Y],

      // Next EAP conversation started after successful completion
         of previous method X. The Intermediate-Result and Crypto-
         Binding TLVs are sent in next packet to minimize round-
         trips.  In this example, identity request is not sent
         before negotiating EAP-Type=Y.

      // Compound MAC calculated using Keys generated from
         EAP methods X and the TLS tunnel.

      Intermediate Result TLV (Success),
      Crypto-Binding TLV (Response),
      EAP-Payload-TLV [EAP-Type=Y] ->

             // Optional additional Y Method exchanges...

                             <- EAP Payload TLV [
                             EAP-Type=Y]

      EAP Payload TLV



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      [EAP-Type=Y] ->

                             <- Intermediate-Result-TLV (Success),
                               Crypto-Binding TLV (Request),
                               Result TLV (Success)

      Intermediate-Result-TLV (Success),
      Crypto-Binding TLV (Response),
      Result-TLV (Success) ->

      // Compound MAC calculated using Keys generated from EAP
         methods X and Y and the TLS tunnel. Compound Keys
         generated using Keys generated from EAP methods X and Y;
         and the TLS tunnel.

      // TLS channel torn down (messages sent in clear text)

                              <- EAP-Success

C.7.  Failed Crypto-binding

   The following exchanges show a failed crypto-binding validation.  The
   conversation will appear as follows:

   Authenticating Peer     Authenticator
   -------------------     -------------
                           <- EAP-Request/
                           Identity
   EAP-Response/
   Identity (MyID1) ->
                           <- EAP-Request/
                           EAP-Type=TEAP, V=1
                           (TEAP Start, S bit set, Authority-ID)

   EAP-Response/
   EAP-Type=TEAP, V=1
   (TLS client_hello without
   PAC-Opaque extension)->
                           <- EAP-Request/
                           EAP-Type=TEAP, V=1
                           (TLS Server Key Exchange
                            TLS Server Hello Done)
   EAP-Response/
   EAP-Type=TEAP, V=1 ->
   (TLS Client Key Exchange
    TLS change_cipher_spec,
    TLS finished)




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                           <- EAP-Request/
                           EAP-Type=TEAP, V=1
                           (TLS change_cipher_spec
                            TLS finished)
                            EAP-Payload-TLV[
                            EAP-Request/Identity])

      // TLS channel established
         (messages sent within the TLS channel)

      // First EAP Payload TLV is piggybacked to the TLS Finished as
         Application Data and protected by the TLS tunnel

   EAP-Payload TLV/
   EAP Identity Response ->

                          <-  EAP Payload TLV, EAP-Request,
                              (EAP-MSCHAPV2, Challenge)

   EAP Payload TLV, EAP-Response,
   (EAP-MSCHAPV2, Response) ->

                          <-  EAP Payload TLV, EAP-Request,
                              (EAP-MSCHAPV2, Success Request)

   EAP Payload TLV, EAP-Response,
   (EAP-MSCHAPV2, Success Response) ->

                        <- Intermediate-Result-TLV (Success),
                            Crypto-Binding TLV (Request),
                               Result TLV (Success)

      Intermediate-Result-TLV (Success),
      Result TLV (Failure)
      Error TLV with
      (Error Code = 2001) ->

   // TLS channel torn down
      (messages sent in clear text)

                           <- EAP-Failure

C.8.  Sequence of EAP Method with Vendor-Specific TLV Exchange

   When TEAP is negotiated, with a sequence of EAP method followed by
   Vendor-Specific TLV exchange, the conversation will occur as follows:

      Authenticating Peer     Authenticator



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      -------------------     -------------
                              <- EAP-Request/
                              Identity
      EAP-Response/
      Identity (MyID1) ->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TEAP Start, S bit set, Authority-ID)

      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_hello)->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS server_hello,
                               TLS certificate,
                       [TLS server_key_exchange,]
                       [TLS certificate_request,]
                           TLS server_hello_done)

      EAP-Response/
      EAP-Type=TEAP, V=1
      ([TLS certificate,]
       TLS client_key_exchange,
      [TLS certificate_verify,]
       TLS change_cipher_spec,
       TLS finished) ->
                             <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS change_cipher_spec,
                               TLS finished,
                              EAP-Payload-TLV[
                              EAP-Request/Identity])

      // TLS channel established
         (messages sent within the TLS channel)

      // First EAP Payload TLV is piggybacked to the TLS Finished as
         Application Data and protected by the TLS tunnel

      EAP-Payload-TLV
      [EAP-Response/Identity] ->

                            <- EAP-Payload-TLV
                            [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X] ->



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                             <- EAP-Payload-TLV
                            [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X]->

                              <- Intermediate Result TLV (Success),
                               Crypto-Binding TLV (Request),
                               Vendor-Specific TLV,

      // Vendor Specific TLV exchange started after successful
         completion of previous method X. The Intermediate-Result
         and Crypto-Binding TLVs are sent with Vendor Specific TLV
         in next packet to minimize round-trips.

      // Compound MAC calculated using Keys generated from
         EAP methods X and the TLS tunnel.

      Intermediate Result TLV (Success),
      Crypto-Binding TLV (Response),
      Vendor-Specific TLV ->

          // Optional additional Vendor-Specific TLV exchanges...

                             <- Vendor-Specific TLV

      Vendor Specific TLV ->
                             <- Result TLV (Success)

      Result-TLV (Success) ->

      // TLS channel torn down (messages sent in clear text)

                              <- EAP-Success

C.9.  Peer Requests Inner Method After Server Sends Result TLV

   In the case where the peer is authenticated during Phase 1 and server
   sends back result TLV, but the peers wants to request another inner
   method, the conversation will appear as follows:

      Authenticating Peer    Authenticator
      -------------------    -------------
                             <- EAP-Request/Identity
      EAP-Response/
      Identity (MyID1) ->

      // Identity sent in the clear. May be a hint to help route



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         the authentication request to EAP server, instead of the
         full user identity.

                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TEAP Start, S bit set, Authority-ID)
      EAP-Response/
      EAP-Type=TEAP, V=1
      (TLS client_hello)->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS server_hello,
                               TLS certificate,
                              [TLS server_key_exchange,]
                              [TLS certificate_request,]
                               TLS server_hello_done)
      EAP-Response/
      EAP-Type=TEAP, V=1
      [TLS certificate,]
       TLS client_key_exchange,
      [TLS certificate_verify,]
       TLS change_cipher_spec,
       TLS finished ->
                              <- EAP-Request/
                              EAP-Type=TEAP, V=1
                              (TLS change_cipher_spec,
                               TLS finished,
                               Crypto-Binding TLV (Request),
                                Result TLV (Success))

      // TLS channel established
         (TLV Payload messages sent within the TLS channel)

       Crypto-Binding TLV(Response),
       Request-Action TLV
       (Status=Failure, Action=Negotiate-EAP)->

                                <- EAP-Payload-TLV
                                [EAP-Request/Identity]

      EAP-Payload-TLV
      [EAP-Response/Identity] ->

                            <- EAP-Payload-TLV
                            [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X] ->



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                             <- EAP-Payload-TLV
                            [EAP-Request/EAP-Type=X]

      EAP-Payload-TLV
      [EAP-Response/EAP-Type=X]->

                              <- Intermediate Result TLV (Success),
                                     Crypto-Binding TLV (Request),
                                 Result TLV (Success)

      Intermediate Result TLV (Success),
      Crypto-Binding TLV (Response),
      Result-TLV (Success)) ->

      //TLS channel torn down
      (messages sent in clear text)

                              <- EAP-Success

C.10.  Channel Binding

   The following exchanges show a successful TEAP authentication with
   basic password authentication and channel binding using Request-
   Action TLV, the conversation will appear as follows:

       Authenticating Peer     Authenticator
       -------------------     -------------
                               <- EAP-Request/
                               Identity
       EAP-Response/
       Identity (MyID1) ->

                               <- EAP-Request/
                               EAP-Type=TEAP, V=1
                               (TEAP Start, S bit set, Authority-ID)

       EAP-Response/
       EAP-Type=TEAP, V=1
       (TLS client_hello with
        PAC-Opaque in SessionTicket extension)->

                               <- EAP-Request/
                               EAP-Type=TEAP, V=1
                               (TLS server_hello,
                               (TLS change_cipher_spec,
                                TLS finished)

       EAP-Response/



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       EAP-Type=TEAP, V=1 ->
       (TLS change_cipher_spec,
        TLS finished)

       TLS channel established
       (messages sent within the TLS channel)

                              <- Basic-Password-Auth-Req TLV, Challenge

       Basic-Password-Auth-Resp TLV, Response with both
       user name and password) ->

       optional additional exchanges (new pin mode,
       password change etc.) ...

                            <- Crypto-Binding TLV (Request),
                                    Result TLV (Success),

       Crypto-Binding TLV(Response),
       Request-Action TLV
       (Status=Failure, Action=Process-TLV,
       TLV=Channel-Binding TLV)->

                                <- Channel-Binding TLV (Response),
                                    Result TLV (Success),

       Result-TLV (Success) ->

       TLS channel torn down
       (messages sent in clear text)

                               <- EAP-Success

Appendix D.  Major Differences from Previous Revisions

D.1.  Changes from -05

   1  Section 3.3.3, clarified that Intermediate Result TLV and Crypto-
      Binding TLV MUST be exchanged after each EAP method, even with a
      single inner EAP method.

   2  Section 3.5, clarified that tls-unique is from Phase outer TLS
      tunnel before beginning of the Phase 2.

   3  Section 3.6.3, added text to handle processing inner method error.






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   4  Section 3.8, added a section titled Peer Services, stressing
      mutual authentication before rest of peer services.

   5  Section 3.8,4, added a section describing channel binding flows.

   6  Section 7.6, changed SHOULD to MUST for matching server
      certificate realm portion.

   7  Update references from I-Ds to RFCs.

D.2.  Changes from -04

   1  Section 3.2, clarified that requesting new PAC in abbreviated
      handshake is not permitted.

   2  Section 3.6.2, clarified that TLS restart is not allowed for fatal
      Alerts.

   3  Section 3.6.3, added text to handle processing inner method error.

   4  Section 4.1, clarified Flags bit usage.

   5  Section 4.2.3, clarified Identity-Type TLV usage.

   6  Section 4.2.8, clarified mandatory bit in Vendor-Specific TLV.

   7  Section 4.2.13, added Compound MAC presence indicator in Crypto-
      Binding TLV.

D.3.  Changes from -03

   1  Section 4.1, added optional Outer TLV Length field and flag in
      TEAP packet format.

   2  Section 4.3, added TLV processing rules and rules for outer TLVs.

   3  Section 5.2, changed IMCK generation from MSK based to either EMSK
      or MSK with corresponding rules.

   4  Section 4.2.13, introduced two Compound MAC fields for Crypto-
      Binding TLV.

   5  Section 3.4, clarified that all authenticated Peer-Ids, Server-Ids
      and their identity types need to be exported.







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   6  Section 5.1, changed TLS Keying Material Exporter label to
      "EXPORTER: teap session key seed".

   7  Section 4.2.9, clarified Request-Action TLV processing.

D.4.  Changes from -02

   1  Section 3.3.3, clarified protected termination and use of crypto-
      binding TLV.

   2  Section 3.5, changed Session ID to use tls-unique and added
      reference to RFC5247.

   3  Section 3.9, added the use of tls-unique to the certificate
      enrollment request.

   4  Section 4.2.9, modified Request-Action TLV to include Status code
      and optional TLVs.

   5  Section 3.4, clarified that all authenticated Peer-Ids need to be
      exported.

   6  Section 5.1, changed TLS Keying Material Exporter label to "teap
      session key seed".

   7  Section 5.2, changed Intermediate Compound Key Derivation from MSK
      to EMSK generated by inner method.

   8  Section 6, added missing IANA considerations.

   9  Section 7.3, added more security considerations for separation of
      Phase 1 and Phase 2 servers.

   10 Appendix C, updated examples with Request-Action TLV, channel
      binding, and sending certificate after TLS renegotiation.

D.5.  Changes from -01

   1  In Version Negotiation section, clarified what the peer needs to
      do if the supported version is higher than what the server
      proposed.

   2  Section 3.2, clarified the requirement for using anonymous cipher
      suites.







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   3  Clarified that Crypto-binding TLV is always exchanged and
      validated, even without inner methods.

   4  Section 3.4, clarified that all authenticated Peer-Ids need to be
      exported.

   5  Clarified that channel-binding TLV can be used to transmit data
      bidirectionally.

   6  Updated obsolete RFC references

   7  Renumbered TLVs to eliminate gaps

   8  Updated examples with basic password authentication TLVs.

   9  Added Certificate Provisioning Within the Tunnel.

   10 Added Server Unauthenticated Provisioning Mode.

D.6.  Changes from -00

   1  Changed protocol name to TEAP: Tunnel EAP Method

   2  Changed version of protocol to version 1

   3  Revised introduction

   4  Moved differences section to appendix

   5  Revised design goals section

   6  Revised PAC definition

   7  Revised protocol description to be in line with RFC 5077 PAC
      distribution

   8  Revised EAP Sequences Section

   9  Added section on PAC provisioning within tunnel

   10 Added outer TLVs to the message format

   11 Renumbered TLVs

   12 Included PAC TLVs






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   13 Added Authority ID TLV

   14 Added PKCS#7 and server trust root TLV definitions

   15 Added PKCS#10 TLV

   16 PKCS#10 TLV

   17 Added EAP-Type and outer TLVs to crypto binding compound MAC

Authors' Addresses

   Hao Zhou
   Cisco Systems
   4125 Highlander Parkway
   Richfield, OH  44286
   US

   EMail: hzhou@cisco.com


   Nancy Cam-Winget
   Cisco Systems
   3625 Cisco Way
   San Jose, CA  95134
   US

   EMail: ncamwing@cisco.com


   Joseph Salowey
   Cisco Systems
   2901 3rd Ave
   Seattle, WA  98121
   US

   EMail: jsalowey@cisco.com


   Stephen Hanna
   Juniper Networks
   79 Parsons Street
   Brighton, MA  02135
   US

   EMail: shanna@juniper.net





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