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Versions: (draft-mattsson-eap-tls13) 00 01 02

Network Working Group                                        J. Mattsson
Internet-Draft                                                  M. Sethi
Updates: 5216 (if approved)                                     Ericsson
Intended status: Standards Track                        October 16, 2018
Expires: April 19, 2019


                       Using EAP-TLS with TLS 1.3
                      draft-ietf-emu-eap-tls13-02

Abstract

   This document specifies the use of EAP-TLS with TLS 1.3 while
   remaining backwards compatible with existing implementations of EAP-
   TLS.  TLS 1.3 provides significantly improved security, privacy, and
   reduced latency when compared to earlier versions of TLS.  This
   document updates RFC 5216.

Status of This Memo

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

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

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

   This Internet-Draft will expire on April 19, 2019.

Copyright Notice

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

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




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements and Terminology  . . . . . . . . . . . . . .   3
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Overview of the EAP-TLS Conversation  . . . . . . . . . .   3
       2.1.1.  Base Case . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.2.  Resumption  . . . . . . . . . . . . . . . . . . . . .   6
       2.1.3.  Termination . . . . . . . . . . . . . . . . . . . . .   8
       2.1.4.  Privacy . . . . . . . . . . . . . . . . . . . . . . .  10
       2.1.5.  Fragmentation . . . . . . . . . . . . . . . . . . . .  12
     2.2.  Identity Verification . . . . . . . . . . . . . . . . . .  12
     2.3.  Key Hierarchy . . . . . . . . . . . . . . . . . . . . . .  12
     2.4.  Parameter Negotiation and Compliance Requirements . . . .  13
     2.5.  EAP State Machines  . . . . . . . . . . . . . . . . . . .  13
   3.  Detailed Description of the EAP-TLS Protocol  . . . . . . . .  14
   4.  IANA considerations . . . . . . . . . . . . . . . . . . . . .  14
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
     5.1.  Security Claims . . . . . . . . . . . . . . . . . . . . .  14
     5.2.  Peer and Server Identities  . . . . . . . . . . . . . . .  15
     5.3.  Certificate Validation  . . . . . . . . . . . . . . . . .  15
     5.4.  Certificate Revocation  . . . . . . . . . . . . . . . . .  15
     5.5.  Packet Modification Attacks . . . . . . . . . . . . . . .  15
     5.6.  Privacy Considerations  . . . . . . . . . . . . . . . . .  15
     5.7.  Pervasive Monitoring  . . . . . . . . . . . . . . . . . .  16
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     6.2.  Informative references  . . . . . . . . . . . . . . . . .  18
   Appendix A.  Updated references . . . . . . . . . . . . . . . . .  19
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   The Extensible Authentication Protocol (EAP), defined in [RFC3748],
   provides a standard mechanism for support of multiple authentication
   methods.  EAP-Transport Layer Security (EAP-TLS) [RFC5216] specifies
   an EAP authentication method with certificate-based mutual
   authentication and key derivation utilizing the TLS handshake
   protocol for cryptographic algorithms and protocol version
   negotiation, mutual authentication, and establishment of shared
   secret keying material.  EAP-TLS is widely supported for
   authentication in IEEE 802.11 [IEEE-802.11] networks (Wi-Fi) using
   IEEE 802.1X [IEEE-802.1X] and it's the default mechanism for
   certificate based authentication in MulteFire [MulteFire] and 3GPP 5G



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   [TS.33.501] networks.  EAP-TLS [RFC5216] references TLS 1.0 [RFC2246]
   and TLS 1.1 [RFC4346], but works perfectly also with TLS 1.2
   [RFC5246].

   Weaknesses found in previous versions of TLS, as well as new
   requirements for security, privacy, and reduced latency has led to
   the development of TLS 1.3 [RFC8446], which in large parts is a
   complete remodeling of the TLS handshake protocol including a
   different message flow, different handshake messages, different key
   schedule, different cipher suites, different resumption, and
   different privacy protection.  This means that significant parts of
   the normative text in the previous EAP-TLS specification [RFC5216]
   are not applicable to EAP-TLS with TLS 1.3 (or higher).  Therefore,
   aspects such as resumption, privacy handling, and key derivation need
   to be appropriately addressed for EAP-TLS with TLS 1.3 (or higher).

   This document defines how to use EAP-TLS with TLS 1.3 (or higher) and
   does not change how EAP-TLS is used with older versions of TLS.
   While this document updates EAP-TLS [RFC5216], it remains backwards
   compatible with it and existing implementations of EAP-TLS.  This
   document only describes differences compared to [RFC5216].

   In addition to the improved security and privacy offered by TLS 1.3,
   there are other significant benefits of using EAP-TLS with TLS 1.3.
   When EAP-TLS is used with support for privacy, TLS 1.3 requires two
   fewer round-trips.  TLS 1.3 also introduces more possibilities to
   reduce fragmentation when compared to earlier versions of TLS.

1.1.  Requirements and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED","MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Readers are expected to be familiar with the terms and concepts used
   in EAP-TLS [RFC5216] and TLS 1.3 [RFC8446].

2.  Protocol Overview

2.1.  Overview of the EAP-TLS Conversation

2.1.1.  Base Case

   TLS 1.3 changes both the message flow and the handshake messages
   compared to earlier versions of TLS.  Therefore, much of Section 2.1
   of RFC5216 [RFC5216] does not apply for TLS 1.3 (or higher).



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   After receiving an EAP-Request packet with EAP-Type=EAP-TLS as
   described in [RFC5216] the conversation will continue with the TLS
   handshake protocol encapsulated in the data fields of EAP-Response
   and EAP-Request packets.  When EAP-TLS is used with TLS version 1.3
   or higher, the formatting and processing of the TLS handshake SHALL
   be done as specified in that version of TLS.  This document only
   lists additional and different requirements, restrictions, and
   processing compared to [RFC8446] and [RFC5216].

   The EAP server MUST authenticate with a certificate and SHOULD
   require the EAP peer to authenticate with a certificate.
   Certificates can be of any type supported by TLS including raw public
   keys.  Pre-Shared Key (PSK) authentication SHALL NOT be used except
   for resumption.  SessionID is deprecated in TLS 1.3 and the EAP
   server SHALL ignore the legacy_session_id field if TLS 1.3 is
   negotiated.  Resumption is handled as described in Section 2.1.2.
   After the TLS handshake has completed, the EAP server sends EAP-
   Success.

   As stated in [RFC5216], the TLS cipher suite shall not be used to
   protect application data.  This applies also for early application
   data.  When EAP-TLS is used with TLS 1.3, early application data
   SHALL NOT be used.

   In the case where EAP-TLS with mutual authentication is successful,
   the conversation will appear as shown in Figure 1.  The EAP server
   commits to not send any more handshake messages by sending an empty
   TLS record, see Section 2.5.























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    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (MyID)            -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                                    (TLS ServerHello,
                                             TLS EncryptedExtensions,
                                              TLS CertificateRequest,
                                                     TLS Certificate,
                                               TLS CertificateVerify,
                                                        TLS Finished,
                               <--------            TLS empty record)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS Certificate,
    TLS CertificateVerify,
    TLS Finished)              -------->
                               <--------                 EAP-Success

                  Figure 1: EAP-TLS mutual authentication

   When using EAP-TLS with TLS 1.3, the EAP server MUST indicate support
   of resumption in the initial authentication.  To indicate support of
   resumption, the EAP server sends a NewSessionTicket message
   (containing a PSK and other parameters) after it has received the
   Finished message.

   In the case where EAP-TLS with mutual authentication and ticket
   establishment is successful, the conversation will appear as shown in
   Figure 2.












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    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (MyID)            -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                                    (TLS ServerHello,
                                             TLS EncryptedExtensions,
                                              TLS CertificateRequest,
                                                     TLS Certificate,
                                               TLS CertificateVerify,
                               <--------                TLS Finished)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS Certificate,
    TLS CertificateVerify,
    TLS Finished)              -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                               (TLS NewSessionTicket,
                               <--------            TLS empty record)
    EAP-Response/
    EAP-Type=EAP-TLS           -------->
                               <--------                 EAP-Success

                  Figure 2: EAP-TLS ticket establishment

2.1.2.  Resumption

   TLS 1.3 replaces the session resumption mechanisms in earlier
   versions of TLS with a new PSK exchange.  When EAP-TLS is used with
   TLS version 1.3 or higher, EAP-TLS SHALL use a resumption mechanism
   compatible with that version of TLS.

   For TLS 1.3, resumption is described in Section 2.2 of [RFC8446].  If
   the client has received a NewSessionTicket message from the server,
   the client can use the PSK identity received in the ticket to
   negotiate the use of the associated PSK.  If the server accepts it,
   then the security context of the new connection is tied to the
   original connection and the key derived from the initial handshake is



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   used to bootstrap the cryptographic state instead of a full
   handshake.  It is left up to the EAP peer whether to use resumption,
   but a EAP peer SHOULD use resumption as long as it has a valid ticket
   cached.  It is RECOMMENDED that the EAP server accept resumption as
   long as the ticket is valid.  However, the server MAY choose to
   require a full authentication.

   A subsequent authentication using resumption, where both sides
   authenticate successfully is shown in Figure 3.

    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (MyID)            -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                                    (TLS ServerHello,
                                             TLS EncryptedExtensions,
                                                        TLS Finished,
                               <--------            TLS empty record)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS Finished)              -------->
                               <--------                 EAP-Success

                       Figure 3: EAP-TLS resumption

   As specified in Section 2.2 of [RFC8446], the EAP peer SHOULD supply
   a "key_share" extension when offering resumption, which allows the
   EAP server to decline resumption and continue the handshake as a full
   handshake.  The message flow in this case is given by Figure 1 or
   Figure 2.  If the EAP peer did not supply a "key_share" extension
   when offering resumption, the EAP server needs to reject the
   ClientHello and the EAP peer needs to restart a full handshake.  The
   message flow in this case is given by Figure 4 followed by Figure 1
   or Figure 2.







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2.1.3.  Termination

   TLS 1.3 changes both the message flow and the handshake messages
   compared to earlier versions of TLS.  Therefore, some normative text
   in Section 2.1.3 of RFC 5216 [RFC5216] does not apply for TLS 1.3 or
   higher.  The two paragraphs below replaces the corresponding
   paragraphs in Section 2.1.3 of RFC 5216 [RFC5216] when EAP-TLS is
   used with TLS 1.3 or higher.  The other paragraphs in Section 2.1.3
   of RFC 5216 [RFC5216] still apply with the exception that SessionID
   is deprecated.

      If the EAP server authenticates successfully the EAP peer MUST
      send an EAP-Response message with EAP-Type=EAP-TLS containing TLS
      records confirming the processing in the version of TLS used.

      If the EAP peer authenticates successfully the EAP server MUST
      send an EAP-Request packet with EAP-Type=EAP-TLS containing TLS
      records confirming to the processing in the version of TLS used.
      The message flow ends with the EAP server sending a EAP-Success
      message.

   In the case where the server rejects the ClientHello, the
   conversation will appear as shown in Figure 4.

    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (MyID)            -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------          (TLS Alert Message)
    EAP-Response/
    EAP-Type=EAP-TLS           -------->
                               <--------                 EAP-Failure

             Figure 4: EAP-TLS server rejection of ClientHello

   In the case where server authentication is unsuccessful, the
   conversation will appear as shown in Figure 5.




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    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (MyID)            -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                                    (TLS ServerHello,
                                             TLS EncryptedExtensions,
                                              TLS CertificateRequest,
                                                     TLS Certificate,
                                               TLS CertificateVerify,
                                                        TLS Finished,
                               <--------            TLS empty record)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS Alert Message)
                               -------->
                               <--------                 EAP-Failure

           Figure 5: EAP-TLS unsuccessful server authentication

   In the case where the server authenticates to the peer successfully,
   but the peer fails to authenticate to the server, the conversation
   will appear as shown in Figure 6.



















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    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (MyID)            -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                                    (TLS ServerHello,
                                             TLS EncryptedExtensions,
                                              TLS CertificateRequest,
                                                     TLS Certificate,
                                               TLS CertificateVerify,
                                                        TLS Finished,
                               <--------            TLS empty record)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS Certificate,
    TLS CertificateVerify,
    TLS Finished)              -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------          (TLS Alert Message)
    EAP-Response/
    EAP-Type=EAP-TLS           -------->
                               <--------                 EAP-Failure

           Figure 6: EAP-TLS unsuccessful client authentication

2.1.4.  Privacy

   TLS 1.3 significantly improves privacy when compared to earlier
   versions of TLS by forbidding cipher suites without confidentiality
   and encrypting large parts of the TLS handshake including the
   certificate messages.

   EAP-TLS peer and server implementations supporting TLS 1.3 or higher
   MUST support anonymous NAIs (Network Access Identifiers) (Section 2.4
   in [RFC7542]) and the client MUST confidentiality protect its
   identity (e.g. using Anonymous NAIs) when the EAP-TLS server is known
   to support TLS 1.3 or higher.




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   As the certificate messages in TLS 1.3 are encrypted, there is no
   need to send an empty certificate_list or perform a second handshake
   (as needed by EAP-TLS with earlier versions of TLS).  When EAP-TLS is
   used with TLS version 1.3 or higher the EAP-TLS peer and EAP-TLS
   server SHALL follow the processing specified by the used version of
   TLS.  For TLS 1.3 this means that the EAP-TLS peer only sends an
   empty certificate_list if it does not have an appropriate certificate
   to send, and the EAP-TLS server MAY treat an empty certificate_list
   as a terminal condition.

   When EAP-TLS is used with TLS 1.3 and privacy, no extra round-trips
   are added and the message flow looks just like a normal message flow
   with the only difference that an anonymous NAI is used.  In the case
   where EAP-TLS with mutual authentication and privacy is successful,
   the conversation will appear as shown in Figure 7.

    EAP Peer                                              EAP Server

                                                         EAP-Request/
                               <--------                    Identity
    EAP-Response/
    Identity (Anonymous NAI)   -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                               <--------                  (TLS Start)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS ClientHello)           -------->
                                                         EAP-Request/
                                                    EAP-Type=EAP-TLS
                                                    (TLS ServerHello,
                                             TLS EncryptedExtensions,
                                              TLS CertificateRequest,
                                                     TLS Certificate,
                                               TLS CertificateVerify,
                                                        TLS Finished,
                               <--------            TLS empty record)
    EAP-Response/
    EAP-Type=EAP-TLS
   (TLS Certificate,
    TLS CertificateVerify,
    TLS Finished)              -------->
                               <--------                 EAP-Success

                         Figure 7: EAP-TLS privacy






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2.1.5.  Fragmentation

   Including ContentType and ProtocolVersion a single TLS record may be
   up to 16387 octets in length.  Some EAP implementations and access
   networks may limit the number of EAP packet exchanges that can be
   handled.  To avoid fragmentation, it is RECOMMENDED to keep the sizes
   of client, server, and trust anchor certificates small and the length
   of the certificate chains short.  It addition, it is RECOMMENDED to
   use mechanisms that reduce the sizes of Certificate messages.

   While Elliptic Curve Cryptography (ECC) was optional for earlier
   version of TLS, TLS 1.3 mandates support of ECC (see Section 9 of
   [RFC8446]).  To avoid fragmentation, the use of ECC in certificates,
   signature algorithms, and groups are RECOMMENDED when using EAP-TLS
   with TLS 1.3 or higher.  At a 128-bit security level, this reduces
   public key sizes from 384 bytes (RSA and DHE) to 32 bytes (ECDHE) and
   signatures from 384 bytes (RSA) to 64 bytes (ECDSA and EdDSA).  An
   EAP-TLS deployment MAY further reduce the certificate sizes by
   limiting the number of Subject Alternative Names.

   Endpoints SHOULD reduce the sizes of Certificate messages by omitting
   certificates that the other endpoint is known to possess.  When using
   TLS 1.3, all certificates that specifies a trust anchor may be
   omitted (see Section 4.4.2 of [RFC8446]).  When using TLS 1.2 or
   earlier, only the self-signed certificate that specifies the root
   certificate authority may be omitted (see Section 7.4.2 of
   [RFC5246]).  EAP-TLS peers and servers SHOULD support and use the
   Cached Information Extension as specified in [RFC7924].  EAP-TLS
   peers and servers MAY use other extensions for reducing the sizes of
   Certificate messages, e.g. certificate compression
   [I-D.ietf-tls-certificate-compression].

2.2.  Identity Verification

   No updates to [RFC5216].

2.3.  Key Hierarchy

   TLS 1.3 replaces the TLS pseudorandom function (PRF) used in earlier
   versions of TLS with HKDF and completely changes the Key Schedule.
   The key hierarchies shown in Section 2.3 of [RFC5216] are therefore
   not correct when EAP-TLS is used with TLS version 1.3 or higher.  For
   TLS 1.3 the key schedule is described in Section 7.1 of [RFC8446].

   When EAP-TLS is used with TLS version 1.3 or higher the Key_Material,
   IV, and Method-Id SHALL be derived from the exporter_master_secret
   using the TLS exporter interface [RFC5705] (for TLS 1.3 this is
   defined in Section 7.5 of [RFC8446]).



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   Key_Material = TLS-Exporter("EXPORTER_EAP_TLS_Key_Material", "", 128)
   IV           = TLS-Exporter("EXPORTER_EAP_TLS_IV", "", 64)
   Method-Id    = TLS-Exporter("EXPORTER_EAP_TLS_Method-Id", "", 64)
   Session-Id   = 0x0D || Method-Id

   By using the TLS exporter, EAP-TLS can use any TLS 1.3 implementation
   without having to extract the Master Secret, ClientHello.random, and
   ServerHello.random in a non-standard way.

   All other parameters such as MSK and EMSK are derived as specified in
   EAP-TLS [RFC5216], Section 2.3.  The use of these keys is specific to
   the lower layer, as described [RFC5247].

2.4.  Parameter Negotiation and Compliance Requirements

   TLS 1.3 cipher suites are defined differently than in earlier
   versions of TLS (see Section B.4 of [RFC8446]), and the cipher suites
   discussed in Section 2.4 of [RFC5216] can therefore not be used when
   EAP-TLS is used with TLS version 1.3 or higher.  The requirements on
   protocol version and compression given in Section 2.4 of [RFC5216]
   still apply.

   When EAP-TLS is used with TLS version 1.3 or higher, the EAP-TLS
   peers and servers MUST comply with the requirements for the TLS
   version used.  For TLS 1.3 the compliance requirements are defined in
   Section 9 of [RFC8446].

2.5.  EAP State Machines

   TLS 1.3 [RFC8446] introduces Post-Handshake messages.  These Post-
   Handshake messages use the handshake content type and can be sent
   after the main handshake.  One such Post-Handshake message is
   NewSessionTicket.  The NewSessopmTicket can be used for resumption.
   After sending TLS Finished, the EAP server may send any number of
   Post-Handshake messages in separate EAP-Requests.  To decrease the
   uncertainty for the EAP peer, the following procedure MUST be
   followed:

   When an EAP server has sent its last handshake message (Finished or a
   Post-Handshake), it commits to not sending any more handshake
   messages by appending an empty application data record (i.e. a TLS
   record with TLSPlaintext.type = application_data and
   TLSPlaintext.length = 0) to the last handshake record.  After sending
   an empty application data record, the EAP server may only send an
   EAP-Success, an EAP-Failure, or an EAP-Request with a TLS Alert
   Message.





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   Note that the use of an empty application data record does not
   violate the requirement that the TLS cipher suite shall not be used
   to protect application data, as the application data is the empty
   string, no application data is protected.

3.  Detailed Description of the EAP-TLS Protocol

   No updates to [RFC5216].

4.  IANA considerations

   This section provides guidance to the Internet Assigned Numbers
   Authority (IANA) regarding registration of values related to the EAP-
   TLS 1.3 protocol in accordance with [RFC8126].

   This memo requires IANA to add the following labels to the TLS
   Exporter Label Registry defined by [RFC5705].  These labels are used
   in derivation of Key_Material, IV and Method-Id as defined in
   Section 2.3:

   o  "EXPORTER_EAP_TLS_Key_Material"

   o  "EXPORTER_EAP_TLS_IV"

   o  "EXPORTER_EAP_TLS_Method-Id"

5.  Security Considerations

5.1.  Security Claims

   Using EAP-TLS with TLS 1.3 does not change the security claims for
   EAP-TLS as given in Section 4.1 of [RFC5216].  However, it
   strengthens several of the claims as described in the following
   updates to the notes given in Section 4.1 of [RFC5216].

   [2] Confidentiality: The TLS 1.3 handshake offers much better
   confidentiality than earlier versions of TLS by mandating cipher
   suites with confidentiality and encrypting certificates and some of
   the extensions, see [RFC8446].  When using EAP-TLS with TLS 1.3, the
   use of privacy does not cause any additional round-trips.

   [3] Key strength: TLS 1.3 forbids all algorithms with known
   weaknesses including 3DES, CBC mode, RC4, SHA-1, and MD5.  TLS 1.3
   only supports cryptographic algorithms offering at least 112-bit
   security, see [RFC8446].

   [4] Cryptographic Negotiation: TLS 1.3 increases the number of
   cryptographic parameters that are negotiated in the handshake.  When



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   EAP-TLS is used with TLS 1.3, EAP-TLS inherits the cryptographic
   negotiation of AEAD algorithm, HKDF hash algorithm, key exchange
   groups, and signature algorithm, see Section 4.1.1 of [RFC8446].

5.2.  Peer and Server Identities

   No updates to [RFC5216].

5.3.  Certificate Validation

   No updates to [RFC5216].

5.4.  Certificate Revocation

   The OCSP status handling in TLS 1.3 is different from earlier
   versions of TLS, see Section 4.4.2.1 of [RFC8446].  In TLS 1.3 the
   OCSP information is carried in the CertificateEntry containing the
   associated certificate instead of a separate CertificateStatus
   message as in [RFC4366].  This enables sending OCSP information for
   all certificates in the certificate chain.

   EAP-TLS peers and servers supporting TLS 1.3 SHOULD support
   Certificate Status Requests (OCSP stapling) as specified in [RFC6066]
   and Section 4.4.2.1 of [RFC8446].  The use of Certificate Status
   Requests to determine the current status of the EAP server's
   certificate is RECOMMENDED.

5.5.  Packet Modification Attacks

   No updates to [RFC5216].

5.6.  Privacy Considerations

   [RFC6973] suggests that the privacy considerations of IETF protocols
   be documented.

   TLS 1.3 offers much better privacy than earlier versions of TLS as
   discussed in Section 2.1.4.  In this section, we only discuss the
   privacy properties of EAP-TLS with TLS 1.3.  For privacy properties
   of TLS 1.3 itself, see [RFC8446].

   EAP-TLS sends the standard TLS 1.3 handshake messages encapsulated in
   EAP packets.  Additionally, the EAP peer sends an identity in the
   first EAP-Response.  The fields in the EAP-TLS Request and the EAP-
   TLS Response packets do not contain any cleartext privacy sensitive
   information.





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   It is strongly RECOMMENDED to confidentiality protect the identity
   (e.g. using Anonymous NAIs), as the username part of the NAI may
   otherwise enable identification and tracking of the user.  However,
   as with other EAP methods, even when privacy-friendly identifiers or
   EAP tunneling is used, the domain name (i.e. the realm) in the NAI is
   still typically visible.  How much privacy sensitive information the
   domain name leaks is highly dependent on how many other users are
   using the same domain name in the particular access network.  If all
   EAP peers have the same domain, no additional information is leaked.
   If a domain name is used by a small subset of the EAP peers, it may
   aid an attacker in tracking or identifying the user.

   An EAP peer with a policy allowing communication with EAP servers
   supporting only TLS 1.2 (or lower) without privacy and with RSA key
   exchange is vulnerable to disclosure of the peer username.  An active
   attacker can in this case make the EAP peer believe that an EAP
   server supporting TLS 1.3 does not support privacy.  The attacker can
   simply impersonate the EAP server and negotiate TLS 1.2 (or
   lower)with RSA key exchange and send an TLS alert message when the
   EAP peer tries to use privacy by sending an empty certificate
   message.  Since the attacker (impersonating the EAP server) does not
   provide a proof-of-possession of the private key until the Finished
   message when RSA key exchange is used, an EAP peer may inadvertently
   disclose its identity (username) to an attacker.  Therefore, it is
   RECOMMENDED for EAP peers to not use EAP-TLS with TLS 1.2 (or lower)
   and RSA based ciphersuites without privacy.

5.7.  Pervasive Monitoring

   As required by [RFC7258], work on IETF protocols needs to consider
   the effects of pervasive monitoring and mitigate them when possible.

   Pervasive Monitoring is widespread surveillance of users.  By
   encrypting more information, TLS 1.3 offers much better protection
   against pervasive monitoring.  In addition to the privacy attacks
   discussed above, surveillance on a large scale may enable tracking of
   a user over a wider geographical area and across different access
   networks.  Using information from EAP-TLS together with information
   gathered from other protocols increases the risk of identifying
   individual users.

6.  References

6.1.  Normative References







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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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

   [RFC5216]  Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
              Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216,
              March 2008, <https://www.rfc-editor.org/info/rfc5216>.

   [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, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5705]  Rescorla, E., "Keying Material Exporters for Transport
              Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
              March 2010, <https://www.rfc-editor.org/info/rfc5705>.

   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)
              Extensions: Extension Definitions", RFC 6066,
              DOI 10.17487/RFC6066, January 2011,
              <https://www.rfc-editor.org/info/rfc6066>.

   [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, DOI 10.17487/RFC6960, June 2013,
              <https://www.rfc-editor.org/info/rfc6960>.

   [RFC7542]  DeKok, A., "The Network Access Identifier", RFC 7542,
              DOI 10.17487/RFC7542, May 2015,
              <https://www.rfc-editor.org/info/rfc7542>.

   [RFC7924]  Santesson, S. and H. Tschofenig, "Transport Layer Security
              (TLS) Cached Information Extension", RFC 7924,
              DOI 10.17487/RFC7924, July 2016,
              <https://www.rfc-editor.org/info/rfc7924>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.



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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

6.2.  Informative references

   [I-D.ietf-tls-certificate-compression]
              Ghedini, A. and V. Vasiliev, "TLS Certificate
              Compression", draft-ietf-tls-certificate-compression-04
              (work in progress), October 2018.

   [IEEE-802.11]
              Institute of Electrical and Electronics Engineers, "IEEE
              Standard for Information technology--Telecommunications
              and information exchange between systems Local and
              metropolitan area networks--Specific requirements - Part
              11: Wireless LAN Medium Access Control (MAC) and Physical
              Layer (PHY) Specifications", IEEE Std 802.11-2016
              (Revision of IEEE Std 802.11-2012) , December 2016.

   [IEEE-802.1X]
              Institute of Electrical and Electronics Engineers, "IEEE
              Standard for Local and metropolitan area networks -- Port-
              Based Network Access Control", IEEE Standard 802.1X-2010 ,
              February 2010.

   [MulteFire]
              MulteFire, "MulteFire Release 1.0.1 specification", 2017.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, DOI 10.17487/RFC2246, January 1999,
              <https://www.rfc-editor.org/info/rfc2246>.

   [RFC2560]  Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
              Adams, "X.509 Internet Public Key Infrastructure Online
              Certificate Status Protocol - OCSP", RFC 2560,
              DOI 10.17487/RFC2560, June 1999,
              <https://www.rfc-editor.org/info/rfc2560>.

   [RFC3280]  Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
              X.509 Public Key Infrastructure Certificate and
              Certificate Revocation List (CRL) Profile", RFC 3280,
              DOI 10.17487/RFC3280, April 2002,
              <https://www.rfc-editor.org/info/rfc3280>.



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   [RFC4282]  Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
              Network Access Identifier", RFC 4282,
              DOI 10.17487/RFC4282, December 2005,
              <https://www.rfc-editor.org/info/rfc4282>.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346,
              DOI 10.17487/RFC4346, April 2006,
              <https://www.rfc-editor.org/info/rfc4346>.

   [RFC4366]  Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)
              Extensions", RFC 4366, DOI 10.17487/RFC4366, April 2006,
              <https://www.rfc-editor.org/info/rfc4366>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5247]  Aboba, B., Simon, D., and P. Eronen, "Extensible
              Authentication Protocol (EAP) Key Management Framework",
              RFC 5247, DOI 10.17487/RFC5247, August 2008,
              <https://www.rfc-editor.org/info/rfc5247>.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013,
              <https://www.rfc-editor.org/info/rfc6973>.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <https://www.rfc-editor.org/info/rfc7258>.

   [TS.33.501]
              3GPP, "Security architecture and procedures for 5G
              System", 3GPP TS 33.501 0.7.1, February 2018.

Appendix A.  Updated references

   All the following references in [RFC5216] are updated as specified
   below when EAP-TLS is used with TLS 1.3 or higher.

   All references to [RFC2560] are updated with [RFC6960].

   All references to [RFC3280] are updated with [RFC5280].




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   All references to [RFC4282] are updated with [RFC7542].

Acknowledgments

   The authors want to thank Alan DeKok, Ari Keraenen, Bernard Aboba,
   Eric Rescorla, Jari Arkko, Jim Schaad, Jouni Malinen, and Vesa
   Torvinen for comments and suggestions on the draft.

Authors' Addresses

   John Mattsson
   Ericsson
   Stockholm  164 40
   Sweden

   Email: john.mattsson@ericsson.com


   Mohit Sethi
   Ericsson
   Jorvas  02420
   Finland

   Email: mohit@piuha.net



























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