





Internet Engineering Task Force (IETF)                           H. Zhou
Request for Comments: 7170                                 N. Cam-Winget
Category: Standards Track                                     J. Salowey
ISSN: 2070-1721                                            Cisco Systems
                                                                S. Hanna
                                                   Infineon Technologies
                                                                May 2014


       Tunnel Extensible Authentication Protocol (TEAP) Version 1

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) protocol to establish a mutually
   authenticated tunnel.  Within the tunnel, TLV objects are used to
   convey authentication-related data between the EAP peer and the EAP
   server.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7170.

















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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   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  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.  Specification Requirements  . . . . . . . . . . . . . . .   5
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   6
     2.1.  Architectural Model . . . . . . . . . . . . . . . . . . .   7
     2.2.  Protocol-Layering Model . . . . . . . . . . . . . . . . .   8
   3.  TEAP Protocol . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Version Negotiation . . . . . . . . . . . . . . . . . . .   9
     3.2.  TEAP Authentication Phase 1: Tunnel Establishment . . . .  10
       3.2.1.  TLS Session Resume Using Server State . . . . . . . .  11
       3.2.2.  TLS Session Resume Using a PAC  . . . . . . . . . . .  12
       3.2.3.  Transition between Abbreviated and Full TLS Handshake  13
     3.3.  TEAP Authentication Phase 2: Tunneled Authentication  . .  14
       3.3.1.  EAP Sequences . . . . . . . . . . . . . . . . . . . .  14
       3.3.2.  Optional Password Authentication  . . . . . . . . . .  15
       3.3.3.  Protected Termination and Acknowledged Result
               Indication  . . . . . . . . . . . . . . . . . . . . .  15
     3.4.  Determining Peer-Id and Server-Id . . . . . . . . . . . .  16
     3.5.  TEAP Session Identifier . . . . . . . . . . . . . . . . .  17
     3.6.  Error Handling  . . . . . . . . . . . . . . . . . . . . .  17
       3.6.1.  Outer-Layer Errors  . . . . . . . . . . . . . . . . .  18
       3.6.2.  TLS Layer Errors  . . . . . . . . . . . . . . . . . .  18
       3.6.3.  Phase 2 Errors  . . . . . . . . . . . . . . . . . . .  19
     3.7.  Fragmentation . . . . . . . . . . . . . . . . . . . . . .  19
     3.8.  Peer Services . . . . . . . . . . . . . . . . . . . . . .  20
       3.8.1.  PAC Provisioning  . . . . . . . . . . . . . . . . . .  21
       3.8.2.  Certificate Provisioning within the Tunnel  . . . . .  22
       3.8.3.  Server Unauthenticated Provisioning Mode  . . . . . .  23
       3.8.4.  Channel Binding . . . . . . . . . . . . . . . . . . .  23





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   4.  Message Formats . . . . . . . . . . . . . . . . . . . . . . .  24
     4.1.  TEAP Message Format . . . . . . . . . . . . . . . . . . .  24
     4.2.  TEAP TLV Format and Support . . . . . . . . . . . . . . .  26
       4.2.1.  General TLV Format  . . . . . . . . . . . . . . . . .  28
       4.2.2.  Authority-ID TLV  . . . . . . . . . . . . . . . . . .  29
       4.2.3.  Identity-Type TLV . . . . . . . . . . . . . . . . . .  30
       4.2.4.  Result TLV  . . . . . . . . . . . . . . . . . . . . .  31
       4.2.5.  NAK TLV . . . . . . . . . . . . . . . . . . . . . . .  32
       4.2.6.  Error TLV . . . . . . . . . . . . . . . . . . . . . .  33
       4.2.7.  Channel-Binding TLV . . . . . . . . . . . . . . . . .  36
       4.2.8.  Vendor-Specific TLV . . . . . . . . . . . . . . . . .  37
       4.2.9.  Request-Action TLV  . . . . . . . . . . . . . . . . .  38
       4.2.10. EAP-Payload TLV . . . . . . . . . . . . . . . . . . .  40
       4.2.11. Intermediate-Result TLV . . . . . . . . . . . . . . .  41
       4.2.12. PAC TLV Format  . . . . . . . . . . . . . . . . . . .  42
         4.2.12.1.  Formats for PAC Attributes . . . . . . . . . . .  43
         4.2.12.2.  PAC-Key  . . . . . . . . . . . . . . . . . . . .  44
         4.2.12.3.  PAC-Opaque . . . . . . . . . . . . . . . . . . .  44
         4.2.12.4.  PAC-Info . . . . . . . . . . . . . . . . . . . .  45
         4.2.12.5.  PAC-Acknowledgement TLV  . . . . . . . . . . . .  47
         4.2.12.6.  PAC-Type TLV . . . . . . . . . . . . . . . . . .  48
       4.2.13. Crypto-Binding TLV  . . . . . . . . . . . . . . . . .  48
       4.2.14. Basic-Password-Auth-Req TLV . . . . . . . . . . . . .  51
       4.2.15. Basic-Password-Auth-Resp TLV  . . . . . . . . . . . .  52
       4.2.16. PKCS#7 TLV  . . . . . . . . . . . . . . . . . . . . .  53
       4.2.17. PKCS#10 TLV . . . . . . . . . . . . . . . . . . . . .  54
       4.2.18. Trusted-Server-Root TLV . . . . . . . . . . . . . . .  55
     4.3.  TLV Rules . . . . . . . . . . . . . . . . . . . . . . . .  56
       4.3.1.  Outer TLVs  . . . . . . . . . . . . . . . . . . . . .  57
       4.3.2.  Inner TLVs  . . . . . . . . . . . . . . . . . . . . .  57
   5.  Cryptographic Calculations  . . . . . . . . . . . . . . . . .  58
     5.1.  TEAP Authentication Phase 1: Key Derivations  . . . . . .  58
     5.2.  Intermediate Compound Key Derivations . . . . . . . . . .  59
     5.3.  Computing the Compound MAC  . . . . . . . . . . . . . . .  61
     5.4.  EAP Master Session Key Generation . . . . . . . . . . . .  61
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  62
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  66
     7.1.  Mutual Authentication and Integrity Protection  . . . . .  67
     7.2.  Method Negotiation  . . . . . . . . . . . . . . . . . . .  67
     7.3.  Separation of Phase 1 and Phase 2 Servers . . . . . . . .  67
     7.4.  Mitigation of Known Vulnerabilities and Protocol
           Deficiencies  . . . . . . . . . . . . . . . . . . . . . .  68
       7.4.1.  User Identity Protection and Verification . . . . . .  69
       7.4.2.  Dictionary Attack Resistance  . . . . . . . . . . . .  70
       7.4.3.  Protection against Man-in-the-Middle Attacks  . . . .  70
       7.4.4.  PAC Binding to User Identity  . . . . . . . . . . . .  71





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     7.5.  Protecting against Forged Cleartext EAP Packets . . . . .  71
     7.6.  Server Certificate Validation . . . . . . . . . . . . . .  72
     7.7.  Tunnel PAC Considerations . . . . . . . . . . . . . . . .  72
     7.8.  Security Claims . . . . . . . . . . . . . . . . . . . . .  73
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  74
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  75
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  75
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  76
   Appendix A.  Evaluation against Tunnel-Based EAP Method
                Requirements . . . . . . . . . . . . . . . . . . . .  79
     A.1.  Requirement 4.1.1: RFC Compliance . . . . . . . . . . . .  79
     A.2.  Requirement 4.2.1: TLS Requirements . . . . . . . . . . .  79
     A.3.  Requirement 4.2.1.1.1: Ciphersuite Negotiation  . . . . .  79
     A.4.  Requirement 4.2.1.1.2: Tunnel Data Protection Algorithms   79
     A.5.  Requirement 4.2.1.1.3: Tunnel Authentication and Key
           Establishment . . . . . . . . . . . . . . . . . . . . . .  79
     A.6.  Requirement 4.2.1.2: Tunnel Replay Protection . . . . . .  79
     A.7.  Requirement 4.2.1.3: TLS Extensions . . . . . . . . . . .  80
     A.8.  Requirement 4.2.1.4: Peer Identity Privacy  . . . . . . .  80
     A.9.  Requirement 4.2.1.5: Session Resumption . . . . . . . . .  80
     A.10. Requirement 4.2.2: Fragmentation  . . . . . . . . . . . .  80
     A.11. Requirement 4.2.3: Protection of Data External to Tunnel   80
     A.12. Requirement 4.3.1: Extensible Attribute Types . . . . . .  80
     A.13. Requirement 4.3.2: Request/Challenge Response Operation .  80
     A.14. Requirement 4.3.3: Indicating Criticality of Attributes .  80
     A.15. Requirement 4.3.4: Vendor-Specific Support  . . . . . . .  81
     A.16. Requirement 4.3.5: Result Indication  . . . . . . . . . .  81
     A.17. Requirement 4.3.6: Internationalization of Display
           Strings . . . . . . . . . . . . . . . . . . . . . . . . .  81
     A.18. Requirement 4.4: EAP Channel-Binding Requirements . . . .  81
     A.19. Requirement 4.5.1.1: Confidentiality and Integrity  . . .  81
     A.20. Requirement 4.5.1.2: Authentication of Server . . . . . .  81
     A.21. Requirement 4.5.1.3: Server Certificate Revocation
           Checking  . . . . . . . . . . . . . . . . . . . . . . . .  81
     A.22. Requirement 4.5.2: Internationalization . . . . . . . . .  81
     A.23. Requirement 4.5.3: Metadata . . . . . . . . . . . . . . .  82
     A.24. Requirement 4.5.4: Password Change  . . . . . . . . . . .  82
     A.25. Requirement 4.6.1: Method Negotiation . . . . . . . . . .  82
     A.26. Requirement 4.6.2: Chained Methods  . . . . . . . . . . .  82
     A.27. Requirement 4.6.3: Cryptographic Binding with the TLS
           Tunnel  . . . . . . . . . . . . . . . . . . . . . . . . .  82
     A.28. Requirement 4.6.4: Peer-Initiated EAP Authentication  . .  82
     A.29. Requirement 4.6.5: Method Metadata  . . . . . . . . . . .  82
   Appendix B.  Major Differences from EAP-FAST  . . . . . . . . . .  83
   Appendix C.  Examples . . . . . . . . . . . . . . . . . . . . . .  83
     C.1.  Successful Authentication . . . . . . . . . . . . . . . .  83
     C.2.  Failed Authentication . . . . . . . . . . . . . . . . . .  85
     C.3.  Full TLS Handshake Using Certificate-Based Ciphersuite  .  86



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     C.4.  Client Authentication during Phase 1 with Identity
           Privacy . . . . . . . . . . . . . . . . . . . . . . . . .  88
     C.5.  Fragmentation and Reassembly  . . . . . . . . . . . . . .  89
     C.6.  Sequence of EAP Methods . . . . . . . . . . . . . . . . .  91
     C.7.  Failed Crypto-Binding . . . . . . . . . . . . . . . . . .  94
     C.8.  Sequence of EAP Method with Vendor-Specific TLV Exchange   95
     C.9.  Peer Requests Inner Method after Server Sends Result TLV   97
     C.10. Channel Binding . . . . . . . . . . . . . . . . . . . . .  99

1.  Introduction

   A tunnel-based Extensible Authentication Protocol (EAP) method is an
   EAP method that establishes a secure tunnel and executes other EAP
   methods under the protection of that secure tunnel.  A tunnel-based
   EAP method can be used in any lower-layer protocol that supports EAP
   authentication.  There are several existing tunnel-based EAP methods
   that use Transport Layer Security (TLS) [RFC5246] to establish the
   secure tunnel.  EAP methods supporting this include Protected EAP
   (PEAP) [PEAP], EAP 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 the industry calls for a Standards Track tunnel-
   based EAP method.  [RFC6678] outlines the list of requirements for a
   standard tunnel-based EAP method.

   Since its introduction, EAP-FAST [RFC4851] has been widely adopted in
   a variety of devices and platforms.  It has been adopted by the EMU
   working group as the basis for the standard tunnel-based EAP method.
   This document describes the 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", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].












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1.2.  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 [RFC5077] to establish a protected TLS session.  The
      secret key and opaque part may be distributed using [RFC5077]
      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 TLV format.  The TLV format
      is defined in Section 4.2.

2.  Protocol Overview

   TEAP authentication occurs in two phases after the initial EAP
   Identity request/response exchange.  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 TLV objects to carry out
   the inner authentication, results, and other information, such as
   channel-binding information.

   TEAP makes use of the TLS SessionTicket extension [RFC5077], which
   supports TLS session resumption without requiring session-specific
   state stored at the server.  In this document, the SessionTicket 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 used to distribute the PAC-
   Opaque, the PAC-Key is the master secret for the session.  If TEAP



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   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 [RFC5077] 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, the EAP peer and
   EAP server both 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

   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; 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 in
   Section 7.3 provide an additional discussion of the implications of
   separating the TEAP server from the inner method server.











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2.2.  Protocol-Layering Model

   TEAP packets are encapsulated within EAP; EAP in turn requires a
   transport protocol.  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 TLV objects as 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 are encapsulated in a TLV layer.

   TEAP packets may include TLVs both inside and outside the TLS tunnel.
   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 establish 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.2013] 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.





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3.  TEAP Protocol

   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:

   1.   In the first EAP-Request sent with EAP type=TEAP, the EAP server
        MUST set the Version field to the highest version it supports.

   2a.  If the EAP peer supports this version of the protocol, it
        responds with an EAP-Response of EAP type=TEAP, including the
        version number proposed by the TEAP server.

   2b.  If the TEAP peer does not support the proposed version but
        supports a lower version, it responds with an EAP-Response of
        EAP type=TEAP and sets the Version field to its highest
        supported version.

   2c.  If the TEAP peer only supports versions higher than the version
        proposed by the TEAP server, then use of TEAP will not be
        possible.  In this case, the TEAP peer sends back an EAP-Nak
        either to negotiate a different EAP type or to indicate no other
        EAP types are available.

   3a.  If the TEAP server does not support the version number proposed
        by the TEAP peer, it MUST either terminate the conversation with
        an EAP Failure or negotiate a new EAP type.

   3b.  If the TEAP server does support the version proposed by the TEAP
        peer, then the conversation continues using the version proposed
        by the TEAP peer.

   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.




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   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.  If the Crypto-Binding TLV
   fails to be validated, then it is a fatal error and is handled as
   described in Section 3.6.3.

3.2.  TEAP Authentication Phase 1: Tunnel Establishment

   TEAP relies 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]

   This version of the TEAP implementation SHOULD support the following
   TLS ciphersuite:

      TLS_RSA_WITH_AES_256_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 attacks.  TLS ciphersuites that do not provide
   confidentiality MUST NOT be used.  During the TEAP Phase 1
   conversation, the TEAP endpoints MAY negotiate TLS compression.
   During TLS tunnel establishment, TLS extensions MAY be used.  For
   instance, the Certificate Status Request extension [RFC6066] and the
   Multiple Certificate Status Request extension [RFC6961] can be used
   to leverage a certificate-status protocol such as Online Certificate
   Status Protocol (OCSP) [RFC6960] 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



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   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 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 a server-finished handshake message to
   reduce the number of round trips.

   TEAP implementations MUST support mutual peer authentication during
   tunnel establishment using the TLS ciphersuites specified in this
   section.  The TEAP 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 ciphersuite.  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
   from a previous TLS 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.







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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 MUST support the TLS Ticket extension
   [RFC5077] mechanism for distributing a PAC and 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.  Otherwise, if leaked, it
       could lead to user credentials being compromised if sent within
       the tunnel established using the PAC-Key.  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 [RFC5077].  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 [RFC5077], or it may be
       distributed through another mechanism such as the Phase 2 TLVs
       defined in this document.







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   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 ciphersuite 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 to negotiate a 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 that a new PAC be provisioned after the full TLS
   handshake and mutual authentication of the peer and the server.  A
   peer SHOULD NOT request that a new PAC be provisioned after the
   abbreviated handshake, as requesting a new session ticket based on
   resumed session is not permitted.  In order to facilitate the



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   fallback to a full handshake, the peer SHOULD include ciphersuites
   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, as that will compromise the security as the tunnel has not
   been established successfully.  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, as the other peer might have a different security policy.
   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
   to the Intermediate-Result TLV indicating its result.  If the result
   indicates success, the Intermediate-Result TLV MUST be accompanied by



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   a Crypto-Binding TLV.  The Crypto-Binding TLV is further discussed in
   Sections 4.2.13 and 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 because EAP-FAST-GTC is not compliant with
   EAP-GTC defined in [RFC3748].  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 round trips of password
   authentication requests and responses MAY be used to support some
   "housecleaning" functions such as a password or pin change 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 cleartext
   EAP Success or EAP Failure is sent by the server.  Peers implementing
   TEAP MUST NOT accept a cleartext 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, and Outer TLVs exchanged before the TLS tunnel
   establishment.  The Crypto-Binding TLV MUST be exchanged and verified
   before the final Result TLV exchange, regardless of whether or not
   there is an inner EAP method authentication.  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
   cleartext 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 sends the
   cleartext 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.






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   When X.509 certificates are used for peer authentication, the Peer-Id
   is determined by the subject and subjectAltName fields in the peer
   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 and subjectAltName fields in
   the server certificate define 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 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]

     || means concatenation

3.6.  Error Handling

   TEAP uses the 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.



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   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
       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 a failed or missing
       Crypto-Binding) 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.  The entire TEAP packet will be ignored if other fields (version,
       length, flags, etc.) are inconsistent with this specification.

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 or not to allow
   restarts, and, if allowed, how many times the conversation can be
   restarted.  Per TLS [RFC5246], 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 a TEAP request packet encapsulating the



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   TLS HelloRequest handshake message.  The peer may allow the TEAP
   conversation to be restarted, or it may terminate the conversation by
   sending a TEAP response with a zero-length message.

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 the 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 an 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 cleartext 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 cleartext 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 a TEAP implementation MUST provide its own support for



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   fragmentation and reassembly.  Section 3.1 of [RFC3748] discusses
   determining the MTU usable by EAP, and Section 4.3 discusses
   retransmissions in EAP.

   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
   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
   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 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 Message Length field is four octets and provides the
   total length of the message that may be fragmented over the data
   fields of multiple packets; 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 authenticate



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   the server before these peer services are used.  TEAP peer
   implementations MUST have a configuration where authentication fails
   if server authentication cannot be achieved.  In many cases, the
   server will want to authenticate the peer before providing these
   services as well.

   TEAP peers MUST track whether or not server authentication has taken
   place.  Server authentication results if the peer trusts the provided
   server certificate.  Typically, this involves both validating the
   certificate to a trust anchor and confirming the entity named by the
   certificate is the intended server.  Server authentication also
   results when the procedures in Section 3.2 are used to resume a
   session in which the peer and server were previously mutually
   authenticated.  Alternatively, peer services can be used if an inner
   EAP method providing mutual authentication and an Extended Master
   Session Key (EMSK) is executed and cryptographic binding with the
   EMSK Compound Message Authentication Code (MAC) is correctly
   validated (Section 4.2.13).  This is further described in
   Section 3.8.3.

   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 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 participate in the 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 peer
   MUST successfully authenticate the EAP server and validate the
   Crypto-Binding TLV as defined in Section 4.2.13 before issuing the
   request.  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 in 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.





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   A PAC TLV containing a PAC-Acknowledge attribute MUST be sent by the
   peer to acknowledge the receipt of the Tunnel PAC.  A PAC TLV
   containing a 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.

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 "Certificates
   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 from the TLS subsystem
   as defined in "Channel Bindings for TLS" [RFC5929].  The TEAP peer
   operations between obtaining the tls_unique value through generation
   of the Certification Signing Request (CSR) that contains the current
   tls_unique value and the subsequent verification of this value by the
   TEAP server are the "phases of the application protocol during which
   application-layer authentication occurs" that are protected by the
   synchronization interoperability mechanism described in the
   interoperability note in "Channel Bindings for TLS" ([RFC5929],
   Section 3.1).  When performing renegotiation, TLS
   "secure_renegotiation" [RFC5746] MUST be used.

   The tls-unique value is base-64-encoded as specified in Section 4 of
   [RFC4648], and the resulting string is placed in the certification
   request challengePassword field ([RFC2985], Section 5.4.1).  The
   challengePassword field is limited to 255 octets (Section 7.4.9 of
   [RFC5246] indicates that no existing ciphersuite would result in an
   issue with this limitation).  If tls-unique information is not
   embedded within the certification request, the challengePassword
   field MUST be empty to indicate that the peer did not include the
   optional channel-binding information (any value submitted is verified
   by the server as tls-unique information).






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   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 that 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 the ability to authenticate the server
   during Phase 1.  This includes both cases in which the ciphersuite
   negotiated does not provide authentication and in which the
   ciphersuite 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.

   Support for the Server Unauthenticated Provisioning Mode is optional.
   The ciphersuite TLS_DH_anon_WITH_AES_128_CBC_SHA is RECOMMENDED when
   using Server Unauthenticated Provisioning 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, provide 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 Authentication, Authorization, and
   Accounting (AAA) server protected within the EAP method.  This allows
   the server to verify the authenticator is providing information to





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   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 a 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
   the 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.  The peer MUST only send channel-binding
   information after it has successfully 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.

    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 and is defined as follows:

         1 Request

         2 Response



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   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

      55 for TEAP

   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 and ignored upon receipt)

   Ver

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



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   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.

   TLS Data

      When the TLS 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 establish
      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 TLV objects.  The TLV objects could be used
   to carry arbitrary parameters between an 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 a 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.



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   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:

      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




















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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

   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)



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      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)

      17 Trusted-Server-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 one (1)

   R

      Reserved, set to zero (0)

   TLV Type

      1 - Authority-ID

   Length

      The Length field is two octets and 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, 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)

   TLV Type

      2 - Identity-Type TLV



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   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 Sections 3.3.3 and
   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)

   R

      Reserved, set to zero (0)

   TLV Type

      3 - Result TLV

   Length

      2





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   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...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   M

      Mandatory, set to one (1)

   R

      Reserved, set to zero (0)

   TLV Type

      4 - 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



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      Information (SMI) Network Management Private Enterprise Number 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.

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 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.

   Many of the error codes below refer to errors in inner method
   processing that may be retrieved if made available by the inner
   method.  Implementations MUST take care that error messages do not
   reveal too much information to an attacker.  For example, the usage
   of error message 1031 (User account credentials incorrect) is NOT
   RECOMMENDED, because it allows an attacker to determine valid
   usernames by differentiating this response from other responses.  It
   should only be used for troubleshooting purposes.

   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                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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   M

      Mandatory, set to one (1)

   R

      Reserved, set to zero (0)

   TLV Type

      5 - Error TLV

   Length

      4

   Error-Code

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

      1     User account expires soon

      2     User account credential expires soon

      3     User account authorizations change soon

      4     Clock skew detected

      5     Contact administrator

      6     User account credentials change required

      1001  Inner Method Error

      1002  Unspecified authentication infrastructure problem

      1003  Unspecified authentication failure

      1004  Unspecified authorization failure

      1005  User account credentials unavailable

      1006  User account expired

      1007  User account locked: try again later

      1008  User account locked: admin intervention required



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      1009  Authentication infrastructure unavailable

      1010  Authentication infrastructure not trusted

      1011  Clock skew too great

      1012  Invalid inner realm

      1013  Token out of sync: administrator intervention required

      1014  Token out of sync: PIN change required

      1015  Token revoked

      1016  Tokens exhausted

      1017  Challenge expired

      1018  Challenge algorithm mismatch

      1019  Client certificate not supplied

      1020  Client certificate rejected

      1021  Realm mismatch between inner and outer identity

      1022  Unsupported Algorithm In Certificate Signing Request

      1023  Unsupported Extension In Certificate Signing Request

      1024  Bad Identity In Certificate Signing Request

      1025  Bad Certificate Signing Request

      1026  Internal CA Error

      1027  General PKI Error

      1028  Inner method's channel-binding data required but not
            supplied

      1029  Inner method's channel-binding data did not include required
            information

      1030  Inner method's channel binding failed

      1031  User account credentials incorrect [USAGE NOT RECOMMENDED]




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      2001  Tunnel Compromise Error

      2002  Unexpected TLVs Exchanged

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)

   TLV Type

      6 - Channel-Binding TLV

   Length

      variable

   Data

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








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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 the 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....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   M

      0 or 1

   R

      Reserved, set to zero (0)

   TLV Type

      7 - Vendor-Specific TLV

   Length

      4 + cumulative length of all included Vendor TLVs

   Vendor-Id



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      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 Number 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 failed 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.

      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 are
      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 processes 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.




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   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)

   R

      Reserved, set to zero (0)

   TLV Type

      8 - 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




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   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
   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 one (1)

   R

      Reserved, set to zero (0)

   TLV Type

      9 - 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.




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   TLVs

      This (optional) field contains a list of TLVs associated with the
      EAP packet field.  The TLVs MUST NOT have the mandatory bit 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 one (1)

   R

      Reserved, set to zero (0)

   TLV Type

      10 - Intermediate-Result TLV

   Length

      2 + cumulative length of the embedded associated TLVs

   Status

      The Status field is two octets.  Values include:

      1  Success




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      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).  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 or 1

   R

      Reserved, set to zero (0)

   TLV Type

      11 - PAC TLV

   Length

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

   PAC Attributes

      A list of PAC attributes in the TLV format.





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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.

   Value

      The value of the PAC attribute.






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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 that 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
   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



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   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 field 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.

    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...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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   Type

      9 - PAC-Info

   Length

      2-octet 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
         to a server represented by the A-ID.

      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



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         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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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



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         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 field with a value of 2.

   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, and Outer TLVs exchanged before the TLS tunnel
   establishment.

   The Crypto-Binding TLV MUST be exchanged and verified before the
   final Result TLV exchange, regardless of 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.



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   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:

    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 one (1)

   R

      Reserved, set to zero (0)

   TLV Type

      12 - Crypto-Binding TLV

   Length

      76



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   Reserved

      Reserved, set to zero (0)

   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 one (1).

   Received Ver

      The Received Ver 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 zero (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 one (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 - Basic-Password-Auth-Req TLV

   Length

      variable






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   Prompt

      optional user prompt message in UTF-8 [RFC3629] 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 [RFC3629] 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)

   TLV Type

      14 - Basic-Password-Auth-Resp TLV

   Length

      variable

   Userlen

      Length of Username field in octets





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   Username

      Username in UTF-8 [RFC3629] format

   Passlen

      Length of Password field in octets

   Password

      Password in UTF-8 [RFC3629] format

4.2.16.  PKCS#7 TLV

   The PKCS#7 TLV is used by the EAP server to deliver certificate(s) to
   the peer.  The format consists of a certificate or certificate chain
   in binary DER encoding [X.690] 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 MAY return 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: Peers 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.












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   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 DER-encoded X.509 certificate or
      certificate chain in a Certificates-Only PKCS#7 SignedData
      message.

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...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-



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   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 DER-encoded 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).

   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 the Trusted-Server-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.



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   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 - Optional TLV

   R

      Reserved, set to zero (0)

   TLV Type

      17 - Trusted-Server-Root TLV

   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 a single TEAP
   packet.  However, multiple EAP Payload TLVs, 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



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   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 define 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:

   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.



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   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
   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         Trusted-Server-Root

   NOTE: Vendor TLVs (included in Vendor-Specific TLVs) sent with a
   Result TLV MUST be marked as optional.

5.  Cryptographic Calculations

   For key derivation and crypto-binding, TEAP uses the Pseudorandom
   Function (PRF) and MAC algorithms negotiated in the underlying TLS
   session.  Since these algorithms depend on the TLS version and
   ciphersuite, TEAP implementations need a mechanism to determine the
   version and ciphersuite in use for a particular session.  The
   implementation can then use this information to determine which PRF
   and MAC algorithm to use.

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 TLS keying materials are derived and used as defined in
   [RFC5246].



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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 (IMSKs),
   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 TLS-PRF(EMSK, "TEAPbindkey@ietf.org" |
     "\0" | 64)

     where "|" denotes concatenation, EMSK is the EMSK from the inner
     method, "TEAPbindkey@ietf.org" consists the ASCII value for the
     label "TEAPbindkey@ietf.org" (without quotes), "\0" = is a NULL
     octet (0x00 in hex), length is the 2-octet unsigned integer in
     network byte order, and TLS-PRF is the PRF negotiated as part of
     TLS handshake [RFC5246].

   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
   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 the sender computes the Compound
     MAC using the MSK of the inner method.





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     If the EMSK is available and the sender's policy accepts MSK-based
     MAC, then the sender 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
     downgrading to MSK-generated MAC, then the sender SHOULD only send
     EMSK-based MAC.

   On the receiver of the Crypto-Binding TLV side:

     If the EMSK is not available and an MSK-based Compound MAC was
     sent, then the receiver validates the Compound MAC and sends back
     an MSK-based Compound MAC response.

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

     If the EMSK is available and an EMSK-based Compound MAC was sent,
     then the receiver 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 the receiver validates
     it using the MSK and, if successful, generates and returns an 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 the receiver handles
     like an invalid Crypto-Binding TLV with a 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 derivation
   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].





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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.

   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





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   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 are 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 55 has been assigned for TEAP.

   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:

   0  Unassigned

   1  Authority-ID TLV

   2  Identity-Type TLV

   3  Result TLV

   4  NAK TLV

   5  Error TLV

   6  Channel-Binding TLV




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   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 that 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
   Section 4.2.11 contain a Status code that 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 a Specification Required
   basis as defined in [RFC5226].  The initial list of error codes is as
   follows:

   1     User account expires soon

   2     User account credential expires soon



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   3     User account authorizations change soon

   4     Clock skew detected

   5     Contact administrator

   6     User account credentials change required

   1001  Inner Method Error

   1002  Unspecified authentication infrastructure problem

   1003  Unspecified authentication failure

   1004  Unspecified authorization failure

   1005  User account credentials unavailable

   1006  User account expired

   1007  User account locked: try again later

   1008  User account locked: admin intervention required

   1009  Authentication infrastructure unavailable

   1010  Authentication infrastructure not trusted

   1011  Clock skew too great

   1012  Invalid inner realm

   1013  Token out of sync: administrator intervention required

   1014  Token out of sync: PIN change required

   1015  Token revoked

   1016  Tokens exhausted

   1017  Challenge expired

   1018  Challenge algorithm mismatch

   1019  Client certificate not supplied

   1020  Client certificate rejected




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   1021  Realm mismatch between inner and outer identity

   1022  Unsupported Algorithm In Certificate Signing Request

   1023  Unsupported Extension In Certificate Signing Request

   1024  Bad Identity In Certificate Signing Request

   1025  Bad Certificate Signing Request

   1026  Internal CA Error

   1027  General PKI Error

   1028  Inner method's channel-binding data required but not supplied

   1029  Inner method's channel-binding data did not include required
         information

   1030  Inner method's channel binding failed

   1031  User account credentials incorrect [USAGE NOT RECOMMENDED]

   2001  Tunnel Compromise Error

   2002  Unexpected TLVs Exchanged

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

   1  PAC-Key

   2  PAC-Opaque

   3  PAC-Lifetime

   4  A-ID

   5  I-ID



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   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 that is
   assigned on a Specification Required basis as defined in [RFC5226].
   The initial type defined is:

   1  Tunnel PAC

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

   1  PKCS#7-Server-Certificate-Root

   The various values under the 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 "User Specific
   Root Keys (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
   greater.  The threat model used for the security evaluation of TEAP
   is defined in EAP [RFC3748].








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7.1.  Mutual Authentication and Integrity Protection

   As a whole, TEAP 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 it should be used as the indicator of its success or
   failure respectively.  However, as EAP terminates with either a
   cleartext EAP Success or Failure, a peer will also receive a
   cleartext EAP Success or Failure.  The received cleartext EAP Success
   or Failure MUST match that received in the Result TLV; the peer
   SHOULD silently discard those cleartext 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.

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



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   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 [RFC7029])

   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 MUST, at a minimum, provide support for
   IPsec, TLS, 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 [RFC7029].  Implementation and deployment
   SHOULD adopt various mitigation strategies described in [RFC7029].
   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 [RFC7029].

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

   o  Protected EAP inner method negotiation

   o  Sequencing of EAP methods

   o  Strong mutually derived MSKs

   o  Acknowledged success/failure indication




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   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 in 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 of 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
   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.





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   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 renegotiated 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, certificate, and certificate_request messages.
   The peer replies with certificate, client_key_exchange, and
   certificate_verify messages.  Since this renegotiation 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 the 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.

   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.





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   TEAP crypto binding does not guarantee man-in-the-middle protection
   if the client allows a connection to an untrusted server, such as in
   the case where the client does not properly validate the server's
   certificate.  If the TLS ciphersuite derives the master secret solely
   from the contribution of secret data from one side of the
   conversation (such as ciphersuites based on RSA key transport), then
   an attacker who can convince the client to connect and engage in
   authentication can impersonate the client to another server even if a
   strong inner method is executed within the tunnel.  If the TLS
   ciphersuite derives the master secret from the contribution of
   secrets from both sides of the conversation (such as in ciphersuites
   based on Diffie-Hellman), then crypto binding can detect an attacker
   in the conversation if a strong inner method is used.

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 Cleartext EAP Packets

   EAP Success and EAP Failure packets are, in general, sent in
   cleartext 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 authentication
   server (AS) initiate the TEAP authentication Phase 2, compliant TEAP
   implementations MUST silently discard all cleartext EAP messages,
   unless both the TEAP peer and server have indicated success or
   failure using a protected mechanism.  Protected mechanisms include
   the 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




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   or Failure messages where the result does not match the result of the
   protected mechanism.

   To abide by [RFC3748], the server sends a cleartext 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.

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 for the 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 remote, 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 certification authority
   (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]



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   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].

   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







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   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 (Diffie-Hellman) module and DSA (Digital Signature Algorithm)
       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 112-bit equivalent key strength:

       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

   This specification is based on EAP-FAST [RFC4851], which included the
   ideas and 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.

   The method for linking identity and proof-of-possession by placing
   the tls-unique value in the challengePassword field of the CSR as
   described in Section 3.8.2 was inspired by the technique described in
   "Enrollment over Secure Transport" [RFC7030].

   Helpful review comments were provided by Russ Housley, Jari Arkko,
   Ilan Frenkel, Jeremy Steiglitz, Dan Harkins, Sam Hartman, Jim Schaad,
   Barry Leiba, Stephen Farrell, Chris Lonvick, and Josh Howlett.










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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.

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











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9.2.  Informative References

   [IEEE.802-1X.2013]
              IEEE, "Local and Metropolitan Area Networks: Port-Based
              Network Access Control", IEEE Standard 802.1X, December
              2013.

   [NIST-SP-800-57]
              National Institute of Standards and Technology,
              "Recommendation for Key Management", NIST Special
              Publication 800-57, July 2012.

   [PEAP]     Microsoft Corporation, "[MS-PEAP]: Protected Extensible
              Authentication Protocol (PEAP)", February 2014.

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

   [RFC2985]  Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
              Classes and Attribute Types Version 2.0", RFC 2985,
              November 2000.

   [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.

   [RFC4017]  Stanley, D., Walker, J., and B. Aboba, "Extensible
              Authentication Protocol (EAP) Method Requirements for
              Wireless LANs", RFC 4017, March 2005.

   [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.




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   [RFC4282]  Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
              Network Access Identifier", RFC 4282, December 2005.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [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.

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

   [RFC4962]  Housley, R. and B. Aboba, "Guidance for Authentication,
              Authorization, and Accounting (AAA) Key Management", BCP
              132, RFC 4962, July 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.



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

   [RFC6960]  Santesson, S., Myers, M., Ankney, R., Malpani, A.,
              Galperin, S., and C. Adams, "X.509 Internet Public Key
              Infrastructure Online Certificate Status Protocol - OCSP",
              RFC 6960, June 2013.

   [RFC6961]  Pettersen, Y., "The Transport Layer Security (TLS)
              Multiple Certificate Status Request Extension", RFC 6961,
              June 2013.

   [RFC7029]  Hartman, S., Wasserman, M., and D. Zhang, "Extensible
              Authentication Protocol (EAP) Mutual Cryptographic
              Binding", RFC 7029, October 2013.

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

   [X.690]    ITU-T, "ASN.1 encoding rules: Specification of Basic
              Encoding Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", ITU-T Recommendation
              X.690, November 2008.























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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

   TEAPv1 meets this requirement by being compliant with RFC 3748
   [RFC3748], RFC 4017 [RFC4017], RFC 5247 [RFC5247], and RFC 4962
   [RFC4962].  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

   TEAPv1 meets this requirement by mandating TLS version 1.2 support as
   defined in Section 3.2.

A.3.  Requirement 4.2.1.1.1: Ciphersuite Negotiation

   TEAPv1 meets this requirement by using TLS to provide protected
   ciphersuite negotiation.

A.4.  Requirement 4.2.1.1.2: Tunnel Data Protection Algorithms

   TEAPv1 meets this requirement by mandating
   TLS_RSA_WITH_AES_128_CBC_SHA as a mandatory-to-implement ciphersuite
   as defined in Section 3.2.

A.5.  Requirement 4.2.1.1.3: Tunnel Authentication and Key Establishment

   TEAPv1 meets this requirement by mandating
   TLS_RSA_WITH_AES_128_CBC_SHA as a mandatory-to-implement ciphersuite
   that provides certificate-based authentication of the server and is
   approved by NIST.  The mandatory-to-implement ciphersuites only
   include ciphersuites that use strong cryptographic algorithms.  They
   do not include ciphersuites providing mutually anonymous
   authentication or static Diffie-Hellman ciphersuites as defined in
   Section 3.2.

A.6.  Requirement 4.2.1.2: Tunnel Replay Protection

   TEAPv1 meets this requirement by using TLS to provide sufficient
   replay protection.







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A.7.  Requirement 4.2.1.3: TLS Extensions

   TEAPv1 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

   TEAPv1 meets this requirement by establishment of the TLS tunnel and
   protection identities specific to the inner method.  In addition, the
   peer certificate can be sent confidentially (i.e., encrypted).

A.9.  Requirement 4.2.1.5: Session Resumption

   TEAPv1 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

   TEAPv1 meets this requirement by leveraging fragmentation support
   provided by TLS as defined in Section 3.7.

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

   TEAPv1 meets this requirement by including the TEAP version number
   received in the computation of the Crypto-Binding TLV as defined in
   Section 4.2.13.

A.12.  Requirement 4.3.1: Extensible Attribute Types

   TEAPv1 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

   TEAPv1 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

   TEAPv1 meets this requirement by having a mandatory bit in each TLV
   to indicate whether it is mandatory to support or not as defined in
   Section 4.2.






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A.15.  Requirement 4.3.4: Vendor-Specific Support

   TEAPv1 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

   TEAPv1 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

   TEAPv1 meets this requirement by supporting UTF-8 format in the
   Basic-Password-Auth-Req TLV as defined in Section 4.2.14 and the
   Basic-Password-Auth-Resp TLV as defined in Section 4.2.15.

A.18.  Requirement 4.4: EAP Channel-Binding Requirements

   TEAPv1 meets this requirement by having a Channel-Binding TLV to
   exchange the EAP channel-binding data as defined in Section 4.2.7.

A.19.  Requirement 4.5.1.1: Confidentiality and Integrity

   TEAPv1 meets this requirement by running the password authentication
   inside a protected TLS tunnel.

A.20.  Requirement 4.5.1.2: Authentication of Server

   TEAPv1 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

   TEAPv1 meets this requirement by supporting TLS Certificate Status
   Request extension [RFC6066] during tunnel establishment.

A.22.  Requirement 4.5.2: Internationalization

   TEAPv1 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.







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A.23.  Requirement 4.5.3: Metadata

   TEAPv1 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

   TEAPv1 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

   TEAPv1 meets this requirement by supporting inner EAP method
   negotiation within the protected TLS tunnel.

A.26.  Requirement 4.6.2: Chained Methods

   TEAPv1 meets this requirement by supporting inner EAP method chaining
   within protected TLS tunnels as defined in Section 3.3.1.

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

   TEAPv1 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 EAP Authentication

   TEAPv1 meets this requirement by supporting the Request-Action TLV as
   defined in Section 4.2.9 to allow a peer to initiate another inner
   EAP method.

A.29.  Requirement 4.6.5: Method Metadata

   TEAPv1 meets this requirement by supporting the Identity-Type TLV as
   defined in Section 4.2.3 to indicate whether the authentication is
   for a user or a machine.











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Appendix B.  Major Differences from EAP-FAST

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

   1.  The EAP method name has been changed from EAP-FAST to TEAP; this
       change thus requires that a new EAP Type 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 is provided for 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 metadata.  They are the Identity-Type TLV and
       Channel-Binding TLVs, defined in Section 4.2.

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) ->






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                               <- 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
       username and password) ->

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

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

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

       TLS channel torn down
       (messages sent in cleartext)

                               <- EAP-Success








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C.2.  Failed Authentication

   The following exchanges show a failed TEAP authentication due to
   wrong user credentials.  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
       username and password) ->

                               <- Result TLV (Failure)









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       Result TLV (Failure) ->

       TLS channel torn down
       (messages sent in cleartext)

                               <- EAP-Failure

C.3.  Full TLS Handshake Using Certificate-Based Ciphersuite

   In the case within TEAP Phase 1 where an abbreviated TLS handshake is
   tried, fails, and falls back to the certificate-based full TLS
   handshake, 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 with
      PAC-Opaque in SessionTicket extension)->

      // Peer sends PAC-Opaque of Tunnel PAC along with a list of
         ciphersuites supported.  If the server rejects the PAC-
         Opaque, it 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)









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      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 (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 cleartext)

                              <- EAP-Success






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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 (and 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
         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




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

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

      //TLS channel torn down
      (messages sent in cleartext)

                              <- 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)->







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                              <- 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/
                              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.





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      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 cleartext)

                              <- 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)->







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                              <- 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])

      // 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]->






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                              <- 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, an identity request is not sent
         before negotiating EAP-Type=Y.

      // Compound MAC calculated using keys generated from
         EAP method 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
      [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 are
         generated using keys generated from EAP methods X and Y
         and the TLS tunnel.

      // TLS channel torn down (messages sent in cleartext)

                              <- EAP-Success









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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 in SessionTicket 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)

                           <- 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)




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   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 cleartext)

                           <- EAP-Failure

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

   When TEAP is negotiated with a sequence of EAP methods followed by a
   Vendor-Specific TLV exchange, 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)



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      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] ->

                             <- 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 method X and the TLS tunnel.





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      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 cleartext)

                              <- 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 the
   server sends back a Result TLV but the peer 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
         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)





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      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] ->

                             <- 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)) ->





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      // TLS channel torn down
      (messages sent in cleartext)

                              <- EAP-Success

C.10.  Channel Binding

   The following exchanges show a successful TEAP authentication with
   basic password authentication and channel binding using a 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/
       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
       username and password) ->

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



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                            <- 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 cleartext)

                               <- EAP-Success


































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RFC 7170                          TEAP                          May 2014


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
   Infineon Technologies
   79 Parsons Street
   Brighton, MA  02135
   US

   EMail: steve.hanna@infineon.com















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