Internet DRAFT - draft-ietf-emu-eap-tunnel-method
draft-ietf-emu-eap-tunnel-method
EMU Working Group H. Zhou
Internet-Draft N. Cam-Winget
Intended status: Standards Track J. Salowey
Expires: July 13, 2014 Cisco Systems
S. Hanna
Juniper Networks
January 9, 2014
Tunnel EAP Method (TEAP) Version 1
draft-ietf-emu-eap-tunnel-method-10.txt
Abstract
This document defines the Tunnel Extensible Authentication Protocol
(TEAP) version 1. TEAP is a tunnel based EAP method that enables
secure communication between a peer and a server by using the
Transport Layer Security (TLS) protocol to establish a mutually
authenticated tunnel. Within the tunnel, Type-Length-Value (TLV)
objects are used to convey authentication related data between the
EAP peer and the EAP server.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on July 13, 2014.
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
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Specification Requirements . . . . . . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Architectural Model . . . . . . . . . . . . . . . . . . . 7
2.2. Protocol Layering Model . . . . . . . . . . . . . . . . . 7
3. TEAP Protocol . . . . . . . . . . . . . . . . . . . . . . . . 8
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
4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 24
4.1. TEAP Message Format . . . . . . . . . . . . . . . . . . . 24
4.2. TEAP TLV Format and Support . . . . . . . . . . . . . . . 26
4.2.1. General TLV Format . . . . . . . . . . . . . . . . . 27
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 . . . . . . . . . . . . . . . . . . . . . . 34
4.2.7. Channel-Binding TLV . . . . . . . . . . . . . . . . . 37
4.2.8. Vendor-Specific TLV . . . . . . . . . . . . . . . . . 38
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4.2.9. Request-Action TLV . . . . . . . . . . . . . . . . . 39
4.2.10. EAP-Payload TLV . . . . . . . . . . . . . . . . . . . 41
4.2.11. Intermediate-Result TLV . . . . . . . . . . . . . . . 42
4.2.12. PAC TLV Format . . . . . . . . . . . . . . . . . . . 44
4.2.12.1. Formats for PAC Attributes . . . . . . . . . . . 44
4.2.12.2. PAC-Key . . . . . . . . . . . . . . . . . . . . 45
4.2.12.3. PAC-Opaque . . . . . . . . . . . . . . . . . . . 46
4.2.12.4. PAC-Info . . . . . . . . . . . . . . . . . . . . 47
4.2.12.5. PAC-Acknowledgement TLV . . . . . . . . . . . . 49
4.2.12.6. PAC-Type TLV . . . . . . . . . . . . . . . . . . 50
4.2.13. Crypto-Binding TLV . . . . . . . . . . . . . . . . . 50
4.2.14. Basic-Password-Auth-Req TLV . . . . . . . . . . . . . 53
4.2.15. Basic-Password-Auth-Resp TLV . . . . . . . . . . . . 54
4.2.16. PKCS#7 TLV . . . . . . . . . . . . . . . . . . . . . 56
4.2.17. PKCS#10 TLV . . . . . . . . . . . . . . . . . . . . . 57
4.2.18. Trusted-Server-Root TLV . . . . . . . . . . . . . . . 58
4.3. TLV Rules . . . . . . . . . . . . . . . . . . . . . . . . 59
4.3.1. Outer TLVs . . . . . . . . . . . . . . . . . . . . . 60
4.3.2. Inner TLVs . . . . . . . . . . . . . . . . . . . . . 60
5. Cryptographic Calculations . . . . . . . . . . . . . . . . . 61
5.1. TEAP Authentication Phase 1: Key Derivations . . . . . . 61
5.2. Intermediate Compound Key Derivations . . . . . . . . . . 62
5.3. Computing the Compound MAC . . . . . . . . . . . . . . . 64
5.4. EAP Master Session Key Generation . . . . . . . . . . . . 64
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 65
7. Security Considerations . . . . . . . . . . . . . . . . . . . 69
7.1. Mutual Authentication and Integrity Protection . . . . . 70
7.2. Method Negotiation . . . . . . . . . . . . . . . . . . . 70
7.3. Separation of Phase 1 and Phase 2 Servers . . . . . . . . 71
7.4. Mitigation of Known Vulnerabilities and Protocol
Deficiencies . . . . . . . . . . . . . . . . . . . . . . 71
7.4.1. User Identity Protection and Verification . . . . . . 72
7.4.2. Dictionary Attack Resistance . . . . . . . . . . . . 73
7.4.3. Protection against Man-in-the-Middle Attacks . . . . 73
7.4.4. PAC Binding to User Identity . . . . . . . . . . . . 74
7.5. Protecting against Forged Clear Text EAP Packets . . . . 74
7.6. Server Certificate Validation . . . . . . . . . . . . . . 75
7.7. Tunnel PAC Considerations . . . . . . . . . . . . . . . . 75
7.8. Security Claims . . . . . . . . . . . . . . . . . . . . . 76
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 77
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 77
9.1. Normative References . . . . . . . . . . . . . . . . . . 77
9.2. Informative References . . . . . . . . . . . . . . . . . 78
Appendix A. Evaluation Against Tunnel Based EAP Method
Requirements . . . . . . . . . . . . . . . . . . . . 81
A.1. Requirement 4.1.1 RFC Compliance . . . . . . . . . . . . 81
A.2. Requirement 4.2.1 TLS Requirements . . . . . . . . . . . 81
A.3. Requirement 4.2.1.1.1 Cipher Suite Negotiation . . . . . 81
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A.4. Requirement 4.2.1.1.2 Tunnel Data Protection Algorithms . 81
A.5. Requirement 4.2.1.1.3 Tunnel Authentication and Key
Establishment . . . . . . . . . . . . . . . . . . . . . . 82
A.6. Requirement 4.2.1.2 Tunnel Replay Protection . . . . . . 82
A.7. Requirement 4.2.1.3 TLS Extensions . . . . . . . . . . . 82
A.8. Requirement 4.2.1.4 Peer Identity Privacy . . . . . . . . 82
A.9. Requirement 4.2.1.5 Session Resumption . . . . . . . . . 82
A.10. Requirement 4.2.2 Fragmentation . . . . . . . . . . . . . 82
A.11. Requirement 4.2.3 Protection of Data External to Tunnel . 82
A.12. Requirement 4.3.1 Extensible Attribute Types . . . . . . 83
A.13. Requirement 4.3.2 Request/Challenge Response Operation . 83
A.14. Requirement 4.3.3 Indicating Criticality of Attributes . 83
A.15. Requirement 4.3.4 Vendor Specific Support . . . . . . . . 83
A.16. Requirement 4.3.5 Result Indication . . . . . . . . . . . 83
A.17. Requirement 4.3.6 Internationalization of Display Strings 83
A.18. Requirement 4.4 EAP Channel Binding Requirements . . . . 83
A.19. Requirement 4.5.1.1 Confidentiality and Integrity . . . . 83
A.20. Requirement 4.5.1.2 Authentication of Server . . . . . . 84
A.21. Requirement 4.5.1.3 Server Certificate Revocation
Checking . . . . . . . . . . . . . . . . . . . . . . . . 84
A.22. Requirement 4.5.2 Internationalization . . . . . . . . . 84
A.23. Requirement 4.5.3 Meta-data . . . . . . . . . . . . . . . 84
A.24. Requirement 4.5.4 Password Change . . . . . . . . . . . . 84
A.25. Requirement 4.6.1 Method Negotiation . . . . . . . . . . 84
A.26. Requirement 4.6.2 Chained Methods . . . . . . . . . . . . 84
A.27. Requirement 4.6.3 Cryptographic Binding with the TLS
Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . 84
A.28. Requirement 4.6.4 Peer Initiated . . . . . . . . . . . . 85
A.29. Requirement 4.6.5 Method Meta-data . . . . . . . . . . . 85
Appendix B. Major Differences from EAP-FAST . . . . . . . . . . 85
Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 85
C.1. Successful Authentication . . . . . . . . . . . . . . . . 86
C.2. Failed Authentication . . . . . . . . . . . . . . . . . . 87
C.3. Full TLS Handshake using Certificate-based Cipher Suite . 89
C.4. Client authentication during Phase 1 with identity
privacy . . . . . . . . . . . . . . . . . . . . . . . . . 90
C.5. Fragmentation and Reassembly . . . . . . . . . . . . . . 92
C.6. Sequence of EAP Methods . . . . . . . . . . . . . . . . . 94
C.7. Failed Crypto-binding . . . . . . . . . . . . . . . . . . 96
C.8. Sequence of EAP Method with Vendor-Specific TLV Exchange 97
C.9. Peer Requests Inner Method After Server Sends Result TLV 99
C.10. Channel Binding . . . . . . . . . . . . . . . . . . . . . 101
Appendix D. Major Differences from Previous Revisions . . . . . 102
D.1. Changes from -06 . . . . . . . . . . . . . . . . . . . . 102
D.2. Changes from -05 . . . . . . . . . . . . . . . . . . . . 103
D.3. Changes from -04 . . . . . . . . . . . . . . . . . . . . 103
D.4. Changes from -03 . . . . . . . . . . . . . . . . . . . . 104
D.5. Changes from -02 . . . . . . . . . . . . . . . . . . . . 104
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D.6. Changes from -01 . . . . . . . . . . . . . . . . . . . . 105
D.7. Changes from -00 . . . . . . . . . . . . . . . . . . . . 105
1. Introduction
An Extensible Authentication Protocol (EAP) tunnel method is an EAP
method that establishes a secure tunnel and executes other EAP
methods under the protection of that secure tunnel. An EAP tunnel
method can be used in any lower layer protocol that supports EAP
authentication. There are several existing EAP tunnel methods that
use Transport Layer Security (TLS) [RFC5246] to establish the secure
tunnel. EAP methods supporting this include Protected EAP (PEAP)
[PEAP], Tunneled Transport Layer Security EAP (TTLS) [RFC5281] and
EAP Flexible Authentication via Secure Tunneling (EAP-FAST)
[RFC4851]. However, they all are either vendor specific or
informational and industry calls for a standard-track tunnel EAP
method. [RFC6678] outlines the list of requirements for a standard
tunnel based EAP method.
Since the introduction of EAP-FAST [RFC4851] a few years ago, it has
been widely adopted in variety of devices and platforms. It has been
adopted by EMU working group as the basis for the standard tunnel
based EAP method. This document describes Tunnel Extensible
Authentication Protocol (TEAP) version 1, based on EAP-FAST [RFC4851]
with some minor changes, to meet the requirements outlined in
[RFC6678] for a standard tunnel based EAP method.
1.1. Specification Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119] .
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
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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 RFC 5077
messages or using TLVs within the TEAP tunnel. Finally, a PAC may
optionally include other information that may be useful to the
peer.
Type-Length-Value (TLV)
The TEAP protocol utilizes objects in Type-Length-Value (TLV)
format. The TLV format is defined in Section 4.2.
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 Type-Length-Value objects
(TLVs) to carry out the inner authentication, results and other
information, such as channel binding information.
TEAP makes use of the TLS 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
phase 2 is used to distribute the PAC-Opaque, then the PAC-Key is
distributed along with the PAC-Opaque. TEAP implementations MUST
support the RFC 5077 mechanism for distributing a PAC-Opaque and it
is RECOMMENDED that implementations support the capability to
distribute the ticket and secret key within the TEAP tunnel.
The TEAP conversation is used to establish or resume an existing
session to typically establish network connectivity between a peer
and the network. Upon successful execution of TEAP, both EAP peer
and EAP server derive strong session key material that can then be
communicated to the network access server (NAS) for use in
establishing a link layer security association.
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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; or the
authenticator and TEAP server might be a single entity; or the
functions of the authenticator, TEAP server, and inner method server
might be combined into a single physical device. For example,
typical IEEE 802.11 deployments place the Authenticator in an access
point (AP) while a Radius server may provide the TEAP and inner
method server components. The above diagram illustrates the division
of labor among entities in a general manner and shows how a
distributed system might be constructed; however, actual systems
might be realized more simply. The security considerations
Section 7.3 provides an additional discussion of the implications of
separating the TEAP server from the inner method server.
2.2. Protocol Layering Model
TEAP packets are encapsulated within EAP; EAP in turn requires a
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:
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+---------------------------------------------------------------+
| Inner EAP Method | Other TLV information |
|---------------------------------------------------------------|
| TLV Encapsulation (TLVs) |
|---------------------------------------------------------------|
| TLS | Optional Outer TLVs |
|---------------------------------------------------------------|
| TEAP |
|---------------------------------------------------------------|
| EAP |
|---------------------------------------------------------------|
| Carrier Protocol (EAP over LAN, RADIUS, Diameter, etc.) |
+---------------------------------------------------------------+
Protocol Layering Model
The TLV layer is a payload with Type-Length-Value (TLV) Objects
defined in Section 4.2. The TLV objects are used to carry arbitrary
parameters between an EAP peer and an EAP server. All conversations
in the TEAP protected tunnel 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 establishing the TLS tunnel, but
no Inner TLVs are used. In Phase 2 of the TEAP conversation, TLS
records may encapsulate zero or more Inner TLVs, but no Outer TLVs.
Methods for encapsulating EAP within carrier protocols are already
defined. For example, IEEE 802.1X [IEEE.802-1X.2004] may be used to
transport EAP between the peer and the authenticator; RADIUS
[RFC3579] or Diameter [RFC4072] may be used to transport EAP between
the authenticator and the EAP server.
3. TEAP Protocol
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.
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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 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 a available.
3a. If the TEAP server does not support the version number
proposed by the TEAP peer, it 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 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 attack. 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, Certificate Status Request extension [RFC6066] and multiple
certificate status request extension [RFC6961] can be used to
leverage a certificate-status protocol such as 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
peer select the appropriate credential to use. Assuming that the
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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 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 cipher suite. This
allows support for protection of the peer's identity when using TLS
client authentication. An example of the exchanges using TLS
renegotiation to protect privacy is shown in Appendix C.
The following sections describe resuming a TLS session based on
server-side or client-side state.
3.2.1. TLS Session Resume Using Server State
TEAP session resumption is achieved in the same manner TLS achieves
session resume. To support session resumption, the server and peer
minimally cache the Session ID, master secret, and ciphersuite. The
peer attempts to resume a session by including a valid Session ID
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 RFC 5077. The PAC-Opaque can only be
interpreted by the EAP server to recover the required information
for the server to validate the peer's identity and
authentication. The PAC-Opaque includes the PAC-Key and other
TLS session parameters. It may contain the PAC's peer identity.
The PAC-Opaque format and contents are specific to the PAC
issuing server. The PAC-Opaque may be presented in the clear, so
an attacker MUST NOT be able to gain useful information from the
PAC-Opaque itself. The server issuing the PAC-Opaque needs to
ensure it is protected with strong cryptographic keys and
algorithms. The PAC-Opaque may be distributed using the
NewSessionTicket message defined in RFC 5077 or it may be
distributed through another mechanism such as the phase 2 TLVs
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 cipher suite from
information within the PAC-Opaque and finish with the abbreviated TLS
handshake. If the server receives a Session ID and a PAC-Opaque in
the SessionTicket extension in a ClientHello, it should place the
same Session ID in the ServerHello if it is resuming a session based
on the PAC-Opaque. The conversation then proceeds as described in
[RFC5077] until the handshake completes or a fatal error occurs.
After the abbreviated handshake completes, the peer and the server
are ready to commence Phase 2.
3.2.3. Transition between Abbreviated and Full TLS Handshake
If session resumption based on server-side or client-side state
fails, the server can gracefully fall back to a full TLS handshake.
If the ServerHello received by the peer contains an empty Session ID
or a Session ID that is different than in the ClientHello, the server
may fall back to a full handshake. The peer can distinguish the
server's intent of negotiating full or abbreviated TLS handshake by
checking the next TLS handshake messages in the server response to
the ClientHello. If ChangeCipherSpec follows the ServerHello in
response to the ClientHello, then the server has accepted the session
resumption and intends to negotiate the abbreviated handshake.
Otherwise, the server intends to negotiate the full TLS handshake. A
peer can request that a new PAC to 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 to be provisioned after the
abbreviated handshake, as requesting a new session ticket based on
resumed session is not permitted. In order to facilitate the
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fallback to a full handshake the peer SHOULD include cipher suites
that allow for a full handshake and possibly PAC provisioning so the
server can select one of these in case session resumption fails. An
example of the transition is shown in Appendix C.
3.3. TEAP Authentication Phase 2: Tunneled Authentication
The second portion of the TEAP Authentication occurs immediately
after successful completion of Phase 1. Phase 2 occurs even if both
peer and authenticator are authenticated in the Phase 1 TLS
negotiation. Phase 2 MUST NOT occur if the Phase 1 TLS handshake
fails, 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 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
Section 4.2.13 and Section 5.3. The Intermediate-Result TLVs can be
included with other TLVs such as EAP-Payload TLVs starting a new EAP
conversation or with the Result TLV used in the protected termination
exchange.
If both peer and server indicate success, then the method is
considered complete. If either indicates failure, then the method is
considered failed. The result of failure of an EAP method does not
always imply a failure of the overall authentication. If one
authentication method fails, the server may attempt to authenticate
the peer with a different method.
3.3.2. Optional Password Authentication
The use of EAP-FAST-GTC as defined in RFC 5421 [RFC5421] is NOT
RECOMMENDED with TEAPv1 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 roundtrips of password
authentication requests and responses MAY be used to support some
"housecleaning" functions such as password change, change pin, etc.
before a user is authenticated.
3.3.3. Protected Termination and Acknowledged Result Indication
A successful TEAP Phase 2 conversation MUST always end in a
successful Crypto-Binding TLV and Result TLV exchange. A TEAP server
may initiate the Crypto-Binding TLV and Result TLV exchange without
initiating any EAP conversation in TEAP Phase 2. After the final
Result TLV exchange, the TLS tunnel is terminated and a clear text
EAP-Success or EAP-Failure is sent by the server. Peers implementing
TEAP MUST NOT accept a clear-text EAP success or failure packet prior
to the peer and server reaching synchronized protected result
indication.
The Crypto-Binding TLV exchange is used to prove that both the peer
and server participated in the tunnel establishment and sequence of
authentications. It also provides verification of the TEAP type,
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version negotiated, outer TLVs exchanged before the TLS tunnel
establishment. The Crypto-Binding TLV MUST be exchanged and verified
before the final Result TLV exchange, regardless whether there is an
inner EAP method authentication or not. The Crypto-Binding TLV and
Intermediate-Result TLV MUST be included to perform Cryptographic
Binding after each successful EAP method in a sequence of one or more
EAP methods. The server may send the final Result TLV along with an
Intermediate-Result TLV and a Crypto-Binding TLV to indicate its
intention to end the conversation. If the peer requires nothing more
from the server, it will respond with a Result TLV indicating success
accompanied by a Crypto-Binding TLV and Intermediate-Result TLV if
necessary. The server then tears down the tunnel and sends a clear
text EAP-Success or EAP-Failure.
If the peer receives a Result TLV indicating success from the server,
but its authentication policies are not satisfied (for example it
requires a particular authentication mechanism be run or it wants to
request a PAC), it may request further action from the server using
the Request-Action TLV. The Request-Action TLV is sent with a Status
field indicating what EAP Success/Failure result the peer would
expect if the requested action is not granted. The value of the
Action field indicates what the peer would like to do next. The
format and values for the Request-Action TLV are defined in
Section 4.2.9.
Upon receiving the Request-Action TLV the server may process the
request or ignore it, based on its policy. If the server ignores the
request, it proceeds with termination of the tunnel and send the
clear text EAP Success or Failure message based on the Status field
of the peer's Request-Action TLV. If the server honors and processes
the request, it continues with the requested action. The
conversation completes with a Result TLV exchange. The Result TLV
may be included with the TLV that completes the requested action.
Error handling for Phase 2 is discussed in Section 3.6.3.
3.4. Determining Peer-Id and Server-Id
The Peer-Id and Server-Id [RFC5247] may be determined based on the
types of credentials used during either the TEAP tunnel creation or
authentication. In the case of multiple peer authentications, all
authenticated peer identities and their corresponding identity types
(Section 4.2.3) need to be exported. In the case of multiple server
authentications, all authenticated server identities need to be
exported.
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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 defines the Server-Id.
3.5. TEAP Session Identifier
The EAP session identifier [RFC5247] is constructed using the tls-
unique from the phase 1 outer tunnel at the beginning of phase 2 as
defined by section 3.1 of [RFC5929]. The Session-Id is defined as
follows:
Session-Id = teap_type || tls-unique
where teap_type is the EAP method type assigned to TEAP
tls-unique = tls-unique from the phase 1 outer tunnel at the
beginning of phase 2 as defined by section 3.1 of [RFC5929]
|| means concatenation
3.6. Error Handling
TEAP uses the following error handling rules summarized below:
1. Errors in the outer EAP packet layer are handled as defined in
Section 3.6.1.
2. Errors in the TLS layer are communicated via TLS alert messages
in all phases of TEAP.
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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 Crypto-Binding failed
or missing) are handled using Result TLVs and Error TLVs.
3.6.1. Outer Layer Errors
Errors on the TEAP outer packet layer are handled in the following
ways:
1. If Outer TLVs are invalid or contain unknown values, they will be
ignored.
2. 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 to allow restarts, and
if so, how many times the conversation can be restarted. Per TLS
[RFC5226], TLS restart is only allowed for non-fatal alerts. A TEAP
server implementing restart capability SHOULD impose a limit on the
number of restarts, so as to protect against denial-of-service
attacks. If the TEAP server does not allow restarts, it MUST
terminate the conversation with an EAP-Failure packet.
If the TEAP peer detects an error at any point in the TLS layer, the
TEAP peer SHOULD send a TEAP response encapsulating a TLS record
containing the appropriate TLS alert message. The server may restart
the conversation by sending an TEAP request packet encapsulating the
TLS HelloRequest handshake message. The peer may allow the TEAP
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conversation to be restarted or it may terminate the conversation by
sending an TEAP response with an 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 inner method, retransmission is not needed and SHOULD NOT be
attempted, as the outer TLS tunnel can be considered a reliable
transport. If there is a non-fatal error handling the inner method,
instead of silently dropping the inner method request or response and
not responding, the receiving side SHOULD use an Error TLV with error
code Inner Method Error to indicate error processing the current
inner method. The side receiving the Error TLV MAY decide to start a
new inner method instead or send back a Result TLV to terminate the
TEAP authentication session.
If a server receives a Result TLV of failure with a fatal Error TLV,
it MUST send a clear text EAP-Failure. If a peer receives a Result
TLV of failure, it MUST respond with a Result TLV indicating failure.
If the server has sent a Result TLV of failure, it ignores the peer
response, and it MUST send a clear text EAP-Failure.
3.7. Fragmentation
A single TLS record may be up to 16384 octets in length, but a TLS
message may span multiple TLS records, and a TLS certificate message
may in principle be as long as 16 MB. This is larger than the
maximum size for a message on most media types, therefore it is
desirable to support fragmentation. Note that in order to protect
against reassembly lockup and denial-of-service attacks, it may be
desirable for an implementation to set a maximum size for one such
group of TLS messages. Since a typical certificate chain is rarely
longer than a few thousand octets, and no other field is likely to be
anywhere near as long, a reasonable choice of maximum acceptable
message length might be 64 KB. This is still a fairly large message
packet size so an TEAP implementation MUST provide its own support
for fragmentation and reassembly. Section 3.1 of [RFC3748] discusses
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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
TLS Message Length field of four octets. Flags include the Length
included (L), More fragments (M), and TEAP Start (S) bits. The L
flag is set to indicate the presence of the four-octet TLS Message
Length field, and MUST be set for the first fragment of a fragmented
TLS message or set of messages. It MUST NOT be present for any other
message. The M flag is set on all but the last fragment. The S flag
is set only within the TEAP start message sent from the EAP server to
the peer. The TLS Message Length field is four octets, and provides
the total length of the TLS message or set of messages that is being
fragmented; this simplifies buffer allocation.
When a TEAP peer receives an EAP-Request packet with the M bit set,
it MUST respond with an EAP-Response with EAP-Type of TEAP and no
data. This serves as a fragment ACK. The EAP server MUST wait until
it receives the EAP-Response before sending another fragment. In
order to prevent errors in processing of fragments, the EAP server
MUST increment the Identifier field for each fragment contained
within an EAP-Request, and the peer MUST include this Identifier
value in the fragment ACK contained within the EAP-Response.
Retransmitted fragments will contain the same Identifier value.
Similarly, when the TEAP server receives an EAP-Response with the M
bit set, it responds with an EAP-Request with EAP-Type of TEAP and no
data. This serves as a fragment ACK. The EAP peer MUST wait until
it receives the EAP-Request before sending another fragment. In
order to prevent errors in the processing of fragments, the EAP
server MUST increment the Identifier value for each fragment ACK
contained within an EAP-Request, and the peer MUST include this
Identifier value in the subsequent fragment contained within an EAP-
Response.
3.8. Peer Services
Several TEAP services including server unauthenticated provisioning,
PAC provisioning, certificate provisioning and channel binding depend
on the peer trusting the TEAP server. Peers MUST authenticate the
server before these peer services are used. TEAP peer
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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 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 of Section 3.2 are used to resume a session in which the
the peer and server was 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
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 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 different packets. The EAP server will send the PACs
after its internal policy has been satisfied, or it MAY ignore the
request or request additional authentications if its policy dictates.
The server MAY cache the request and provision the PACs requested
after all of its internal policies have been satisfied. If a peer
receives a PAC with an unknown type, it MUST ignore it.
A PAC-TLV containing PAC-Acknowledge attribute MUST be sent by the
peer to acknowledge the receipt of the Tunnel PAC. A PAC-TLV
containing PAC-Acknowledge attribute MUST NOT be used by the peer to
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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 "certs-only"
message encoded into the body of a PKCS#7 TLV (see Section 4.2.16),
only after an authentication method has run and provided an identity
proof on the peer prior to a certificate is being issued.
In order to provide linking identity and proof-of-possession by
including information specific to the current authenticated TLS
session within the signed certification request, the peer generating
the request SHOULD obtain the tls-unique value 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 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 Channel Bindings for TLS
[RFC5929] section 3.1 interoperability notes. 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 challenge-password field ( [RFC2985], Section 5.4.1). The
challenge-password field is limited to 255 bytes (section 7.4.9 of
[RFC5246] indicates that no existing cipher suite would result in an
issue with this limitation). If tls-unique information is not
embedded within the certification request the challenge-password
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).
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
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with an Error TLV using the most descriptive error code possible; it
MAY ignore the PKCS#10 request which generated the error.
3.8.3. Server Unauthenticated Provisioning Mode
In Server Unauthenticated Provisioning Mode, an unauthenticated
tunnel is established in phase 1 and the peer and server negotiate an
EAP method in phase 2 that supports mutual authentication and key
derivation that is resistant to attacks such as Man-in-the-middle and
dictionary attacks. This provisioning mode enables the bootstrapping
of peers when the peer lacks a strong credential usable for mutual
authentication with the server during phase 1. This includes both
cases of where the cipher suite negotiated does not provide
authentication or the cipher suite negotiated provides the
authentication but the peer is unable to validate the identity of the
server for some reason.
Upon successful completion of the EAP method in phase 2, the peer and
server exchange a Crypto-Binding TLV to bind the inner method with
the outer tunnel and ensure that a man-in-the-middle attack has not
been attempted.
Support for the Server Unauthenticated Provisioning Mode is optional.
The cipher suite TLS_DH_anon_WITH_AES_128_CBC_SHA is RECOMMENDED when
using server unauthenticated mode, but other anonymous ciphersuites
MAY be supported as long as the TLS pre-master secret is generated
from contribution from both peers. Phase 2 EAP methods used in
Server Unauthenticated Provisioning Mode MUST provide mutual
authentication, key generation, and be resistant to dictionary
attack. Example inner methods include EAP-pwd [RFC5931] and EAP-EKE
[RFC6124].
3.8.4. Channel Binding
[RFC6677] defines EAP channel bindings to solve the "lying NAS" and
the "lying provider" problems, using a process in which the EAP peer
gives information about the characteristics of the service provided
by the authenticator to the AAA server protected within the EAP
method. This allows the server to verify the authenticator is
providing information to the peer that is consistent with the
information received from this authenticator as well as the
information stored about this authenticator.
TEAP supports EAP channel binding using the Channel-Binding TLV
defined in Section 4.2.7. If the TEAP server wants to request the
channel binding information from the peer, it sends an empty Channel-
Binding TLV to indicate the request. The peer responds to the
request by sending a Channel-Binding TLV containing channel binding
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message as defined in [RFC6677]. The server validates the channel
binding message and sends back a Channel-Binding TLV with a result
code. If the server didn't initiate the channel binding request and
peer still wants to send the channel binding information to the
server, it can do that by using the Request-Action TLV along with the
Channel-Binding TLV.Peer MUST only sends channel binding information
after it has 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 defined as follows:
1 Request
2 Response
Identifier
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The Identifier field is one octet and aids in matching responses
with requests. The Identifier field MUST be changed on each
Request packet. The Identifier field in the Response packet MUST
match the Identifier field from the corresponding request.
Length
The Length field is two octets and indicates the length of the
EAP packet including the Code, Identifier, Length, Type, Flags,
Ver, Message Length, TLS Data, and Outer TLVs fields. Octets
outside the range of the Length field should be treated as Data
Link Layer padding and should be ignored on reception.
Type
TBD for TEAP
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
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This field contains the version of the protocol. This document
describes version 1 (001 in binary) of TEAP.
Message Length
The Message Length field is four octets, and is present only if
the L bit is set. This field provides the total length of the
message that may be fragmented over the data fields of multiple
packets.
Outer TLV Length
The Outer TLV Length field is four octets, and is present only if
the O bit is set. This field provides the total length of the
Outer TLVs if present.
TLS Data
When the Data field is present, it consists of an encapsulated
TLS packet in TLS record format. A TEAP packet with Flags and
Version fields, but with zero length TLS data field, is used to
indicate TEAP acknowledgement for either a fragmented message, a
TLS Alert message or a TLS Finished message.
Outer TLVs
The Outer TLVs consist of the optional data used to help
establishing the TLS tunnel in TLV format. They are only allowed
in the first two messages in the TEAP protocol. That is the
first EAP server to peer message and first peer to EAP server
message. The start of the Outer TLVs can be derived from the EAP
Length field and Outer TLV Length field.
4.2. TEAP TLV Format and Support
The TLVs defined here are standard Type-Length-Value (TLV) objects.
The TLV objects could be used to carry arbitrary parameters between
EAP peer and EAP server within the protected TLS tunnel.
The EAP peer may not necessarily implement all the TLVs supported by
the EAP server. To allow for interoperability, TLVs are designed to
allow an EAP server to discover if a TLV is supported by the EAP
peer, using the NAK TLV. The mandatory bit in a TLV indicates
whether support of the TLV is required. If the peer or server does
not support a TLV marked mandatory, then it MUST send a NAK TLV in
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the response, and all the other TLVs in the message MUST be ignored.
If an EAP peer or server finds an unsupported TLV that is marked as
optional, it can ignore the unsupported TLV. It MUST NOT send an NAK
TLV for a TLV that is not marked mandatory. If all TLVs in a message
are marked optional and none are understood by the peer, then a NAK
TLV or Result TLV could be sent to the other side in order to
continue the conversation.
Note that a peer or server may support a TLV with the mandatory bit
set, but may not understand the contents. The appropriate response
to a supported TLV with content that is not understood is defined by
the individual TLV specification.
EAP implementations compliant with this specification MUST support
TLV exchanges, as well as the processing of mandatory/optional
settings on the TLV. Implementations conforming to this
specification MUST support the following TLVs:
Authority-ID TLV
Identity-Type TLV
Result TLV
NAK TLV
Error TLV
Request-Action TLV
EAP-Payload TLV
Intermediate-Result TLV
Crypto-Binding TLV
Basic-Password-Auth-Req TLV
Basic-Password-Auth-Resp TLV
4.2.1. General TLV Format
TLVs are defined as described below. The fields are transmitted from
left to right.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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)
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9 EAP-Payload TLV (Section 4.2.10)
10 Intermediate-Result TLV (Section 4.2.11)
11 PAC TLV (Section 4.2.12)
12 Crypto-Binding TLV (Section 4.2.13)
13 Basic-Password-Auth-Req TLV (Section 4.2.14)
14 Basic-Password-Auth-Resp TLV (Section 4.2.15)
15 PKCS#7 TLV (Section 4.2.16)
16 PKCS#10 TLV (Section 4.2.17)
17 Server-Trusted-Root TLV (Section 4.2.18)
Length
The length of the Value field in octets.
Value
The value of the TLV.
4.2.2. Authority-ID TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to one (1)
R
Reserved, set to zero (0)
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TLV Type
1 for Authority-ID
Length
The Length filed is two octets, which contains the length of
the ID field in octets.
ID
Hint of the identity of the server, to help the peer to match
the credentials available for the server. It should be unique
across the deployment.
4.2.3. Identity-Type TLV
The Identity-Type TLV allows an EAP server to send a hint to help the
EAP peer select the right type of identity; for example; user or
machine. TEAPv1 implementations MUST support this TLV. Only one
Identity-Type TLV SHOULD be present in the TEAP request or response
packet. The Identity-Type TLV request MUST come with an EAP-Payload
TLV or Basic-Password-Auth-Req TLV. If the EAP peer does have an
identity corresponding to the identity type requested, then the peer
SHOULD respond with an Identity-Type TLV with the requested type. If
the Identity-Type field does not contain one of the known values or
if the EAP peer does not have an identity corresponding to the
identity type requested, then the peer SHOULD respond with an
Identity-Type TLV with the one of available identity types. If the
server receives an identity type in the response that does not match
the requested type, then the peer does not possess the requested
credential type and the server SHOULD proceed with authentication for
the credential type proposed by the peer or proceed with requesting
another credential type, or simply apply the network policy based on
the configured policy, e.g., sending Result TLV with Failure.
The Identity-Type TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identity-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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M
0 (Optional)
R
Reserved, set to zero (0)
TLV Type
2 for Identity-Type TLV
Length
2
Identity-Type
The Identity-Type field is two octets. Values include:
1 User
2 Machine
4.2.4. Result TLV
The Result TLV provides support for acknowledged success and failure
messages for protected termination within TEAP. If the Status field
does not contain one of the known values, then the peer or EAP server
MUST treat this as a fatal error of Unexpected TLVs Exchanged. The
behavior of the Result TLV is further discussed in Section 3.3.3 and
Section 3.6.3. A Result TLV indicating failure MUST NOT be
accompanied by the following TLVs: NAK, EAP-Payload TLV, or Crypto-
Binding TLV. The Result TLV is defined as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
3 for Result TLV
Length
2
Status
The Status field is two octets. Values include:
1 Success
2 Failure
4.2.5. NAK TLV
The NAK TLV allows a peer to detect TLVs that are not supported by
the other peer. A TEAP packet can contain 0 or more NAK TLVs. A NAK
TLV should not be accompanied by other TLVs. A NAK TLV MUST NOT be
sent in response to a message containing a Result TLV, instead a
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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 for NAK TLV
Length
>=6
Vendor-Id
The Vendor-Id field is four octets, and contains the Vendor-Id
of the TLV that was not supported. The high-order octet is 0
and the low-order three octets are the Structure of Management
Information (SMI) Network Management Private Enterprise Code of
the Vendor in network byte order. The Vendor-Id field MUST be
zero for TLVs that are not Vendor-Specific TLVs.
NAK-Type
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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 codes 2000-2999 represent fatal errors. A
fatal Error TLV MUST be accompanied by a Result TLV indicating
failure and the conversation is terminated as described in
Section 3.6.3.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
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Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
5 for Error TLV
Length
4
Error-Code
The Error-Code field is four octets. Currently defined values
for Error-Code include:
1 User account expires soon
2 User account credential expires soon
3 User account authorisations 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 authorisation failure
1005 User account credentials unavailable
1006 User account expired
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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
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
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1030 Inner method's channel binding failed
1031 User account credentials incorrect [USAGE NOT
RECOMMENDED]
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 for Channel-Binding TLV
Length
variable
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Data
The data field contains a channel-binding message as defined in
section 5.3 of [RFC6677].
4.2.8. Vendor-Specific TLV
The Vendor-Specific TLV is available to allow vendors to support
their own extended attributes not suitable for general usage. A
Vendor-Specific TLV attribute can contain one or more TLVs, referred
to as Vendor TLVs. The TLV-type of a Vendor-TLV is defined by the
vendor. All the Vendor TLVs inside a single Vendor-Specific TLV
belong to the same vendor. There can be multiple Vendor-Specific
TLVs from different vendors in the same message. Error handling in
the Vendor TLV could use vendor's own specific error handling
mechanism or use the standard TEAP error codes defined.
Vendor TLVs may be optional or mandatory. Vendor TLVs sent with
Result TLVs MUST be marked as optional. If the Vendor-Specific TLV
is marked as mandatory, then it is expected that the receiving side
needs to recognize the vendor ID, parse all Vendor TLVs within and
deal with error handling within the Vendor-Specific TLV as defined by
the vendor.
The Vendor-Specific TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor TLVs....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
0 or 1
R
Reserved, set to zero (0)
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TLV Type
7 for Vendor Specific TLV
Length
4 + cumulative length of all included Vendor TLVs
Vendor-Id
The Vendor-Id field is four octets, and contains the Vendor-Id
of the TLV. The high-order octet is 0 and the low-order 3
octets are the SMI Network Management Private Enterprise Code
of the Vendor in network byte order.
Vendor TLVs
This field is of indefinite length. It contains vendor-
specific TLVs, in a format defined by the vendor.
4.2.9. Request-Action TLV
The Request-Action TLV MAY be sent by both the peer and the server in
response to a successful or failure Result TLV. It allows the peer
or server to request the other side to negotiate additional EAP
methods or process TLVs specified in the response packet. The
receiving side MUST process this TLV. The processing for the TLV is
as follows:
The receiving entity MAY choose to process any of the TLVs that
are included in the message.
If the receiving entity chooses NOT to process any TLV in the
list, then it sends back a Result TLV with the same code in the
Status field of the Request-Action TLV.
If multiple Request-Action TLVs are in the request, the session
can continue if any of the TLVs in any Request-Action TLV is
processed.
If multiple Request-Action TLVs are in the request and none of
them is processed, then the most fatal status should be used in
the Result TLV returned. If a status code in the Request-Action
TLV is not understood by the receiving entity, then it should be
treated as a fatal error.
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After processing the TLVs or EAP method in the request, another
round of Result TLV exchange would occur to synchronize the final
status on both sides.
The peer or the server MAY send multiple Request-Action TLVs to the
other side. Two Request-Action TLVs MUST NOT occur in the same TEAP
packet if they have the same Status value. The order of processing
multiple Request-Action TLVs is implementation dependent. If the
receiving side process the optional (non-fatal) items first, it is
possible that the fatal items will disappear at a later time. If the
receiving side processes the fatal items first, the communication
time will be shorter.
The peer or the server MAY return a new set of Request-Action TLVs
after one or more of the requested items has been processed and the
other side has signaled it wants to end the EAP conversation.
The Request-Action TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status | Action | TLVs....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-
M
Mandatory set to one (1)
R
Reserved, set to zero (0)
TLV Type
8 for Request-Action TLV
Length
2 + cumulative length of all included TLVs
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Status
The Status field is one octet. This indicates the result if the
server does not process the action requested by the peer. Values
include:
1 Success
2 Failure
Action
The Action field is one octet. Values include:
1 Process-TLV
2 Negotiate-EAP
TLVs
This field is of indefinite length. It contains TLVs that the
peer wants the server to process.
4.2.10. EAP-Payload TLV
To allow piggybacking an EAP request or response with other TLVs, the
EAP-Payload TLV is defined, which includes an encapsulated EAP packet
and a list of optional TLVs. The optional TLVs are provided for
future extensibility to provide hints about the current EAP
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...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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M
Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
9 for EAP-Payload TLV
Length
length of embedded EAP packet + cumulative length of additional
TLVs
EAP packet
This field contains a complete EAP packet, including the EAP
header (Code, Identifier, Length, Type) fields. The length of
this field is determined by the Length field of the
encapsulated EAP packet.
TLVs
This (optional) field contains a list of TLVs associated with
the EAP packet field. The TLVs MUST NOT have the mandatory bit
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:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status | TLVs...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
10 for Intermediate-Result TLV
Length
2 + cumulative length of the embedded associated TLVs
Status
The Status field is two octets. Values include:
1 Success
2 Failure
TLVs
This field is of indeterminate length, and contains zero or
more of the TLVs associated with the Intermediate Result TLV.
The TLVs in this field MUST NOT have the mandatory bit set.
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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.
4.2.12.1. Formats for PAC Attributes
Each PAC attribute in a PAC TLV is formatted as a TLV defined as
follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
4.2.12.2. PAC-Key
The PAC-Key is a secret key distributed in a PAC attribute of type
PAC-Key. The PAC-Key attribute is included within the PAC TLV
whenever the server wishes to issue or renew a PAC that is bound to a
key such as a Tunnel PAC. The key is a randomly generated octet
string, which is 48 octets in length. The generator of this key is
the issuer of the credential, which is identified by the Authority
Identifier (A-ID).
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ 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
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:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
2 - PAC-Opaque
Length
The Length filed is two octets, which contains the length of
the Value field in octets.
Value
The Value field contains the actual data for the PAC-Opaque.
It is specific to the server implementation.
4.2.12.4. PAC-Info
The PAC-Info is comprised of a set of PAC attributes as defined in
Section 4.2.12.1. The PAC-Info attribute MUST contain the A-ID, A
-ID-Info, and PAC-Type attributes. Other attributes MAY be included
in the PAC-Info to provide more information to the peer. The PAC-
Info attribute MUST NOT contain the PAC-Key, PAC-Acknowledgement,
PAC-Info, or PAC-Opaque attributes. The PAC-Info attribute is
included within the PAC TLV whenever the server wishes to issue or
renew a PAC.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attributes...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
9 - PAC-Info
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Length
2-octet Length field containing the length of the attributes
field in octets.
Attributes
The attributes field contains a list of PAC attributes. Each
mandatory and optional field type is defined as follows:
3 - PAC-LIFETIME
This is a 4-octet quantity representing the expiration time
of the credential expressed as the number of seconds,
excluding leap seconds, after midnight UTC, January 1, 1970.
This attribute MAY be provided to the peer as part of the
PAC-Info.
4 - A-ID
The A-ID is the identity of the authority that issued the
PAC. The A-ID is intended to be unique across all issuing
servers to avoid namespace collisions. The A-ID is used by
the peer to determine which PAC to employ. The A-ID is
treated as an opaque octet string. This attribute MUST be
included in the PAC-Info attribute. The A-ID MUST match the
Authority-ID the server used to establish the tunnel. One
method for generating the A-ID is to use a high-quality
random number generator to generate a random number. An
alternate method would be to take the hash of the public key
or public key certificate belonging a server represented by
the A-ID.
5 - I-ID
Initiator identifier (I-ID) is the peer identity associated
with the credential. This identity is derived from the
inner authentication or from the client-side authentication
during tunnel establishment if inner authentication is not
used. The server employs the I-ID in the TEAP phase 2
conversation to validate that the same peer identity used to
execute TEAP phase 1 is also used in at minimum one inner
authentication in TEAP phase 2. If the server is enforcing
the I-ID validation on the inner authentication, then the
I-ID MUST be included in the PAC-Info, to enable the peer to
also enforce a unique PAC for each unique user. If the I-ID
is missing from the PAC-Info, it is assumed that the Tunnel
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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
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The resulting value MUST be one of the following:
1 - Success
2 - Failure
4.2.12.6. PAC-Type TLV
The PAC-Type TLV is a TLV intended to specify the PAC type. It is
included in a PAC-TLV sent by the peer to request PAC provisioning
from the server. Its format is described below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PAC Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
10 - PAC-Type
Length
2-octet Length field with a value of 2
PAC Type
This 2-octet field defines the type of PAC being requested or
provisioned. The following values are defined:
1 - Tunnel PAC
4.2.13. Crypto-Binding TLV
The Crypto-Binding TLV is used to prove that both the peer and server
participated in the tunnel establishment and sequence of
authentications. It also provides verification of the TEAP type,
version negotiated, outer TLVs exchanged before the TLS tunnel
establishment.
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The Crypto-Binding TLV MUST be exchanged and verified before the
final Result TLV exchange, regardless whether there is an inner EAP
method authentication or not. It MUST be included with the
Intermediate-Result TLV to perform Cryptographic Binding after each
successful EAP method in a sequence of EAP methods, before proceeding
with another inner EAP method.
The Crypto-Binding TLV is valid only if the following checks pass:
o The Crypto-Binding TLV version is supported
o The MAC verifies correctly
o The received version in the Crypto-Binding TLV matches the version
sent by the receiver during the EAP version negotiation
o The subtype is set to the correct value
If any of the above checks fails, then the TLV is invalid. An
invalid Crypto-Binding TLV is a fatal error and is handled as
described in Section 3.6.3
The Crypto-Binding TLV is defined as follows:
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
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Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
12 for Crypto-Binding TLV
Length
56
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 Version
The Received Version field is a single octet and MUST be set to
the TEAP version number received during version negotiation.
Note that this field only provides protection against downgrade
attacks, where a version of EAP requiring support for this TLV
is required on both sides.
Flags
The Flags field is four bits. Defined values include
1 EMSK Compound MAC is present
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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).
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:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prompt ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
0 (Optional)
R
Reserved, set to zero (0)
TLV Type
13 for Basic-Password-Auth-Req TLV
Length
variable
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:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Userlen | Username
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Username ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Passlen | Password
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Password ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
0 (Optional)
R
Reserved, set to zero (0)
TLV Type
14 for Basic-Password-Auth-Resp TLV
Length
variable
Userlen
Length of Username field in octets
Username
Username in UTF-8 [RFC3629] format
Passlen
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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 (a)
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.
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...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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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...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
M
0 - Optional TLV
R
Reserved, set to zero (0)
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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 Server-Trusted-Root TLV.
The EAP server MAY also choose not to honor the request.
The Trusted-Server-Root TLV allows the peer to send a request to the
EAP server for a list of trusted roots. The server may respond with
one or more root certificates in PKCS#7 [RFC2315] format.
If the EAP server sets the credential format to PKCS#7-Server-
Certificate-Root, then the Trusted-Server-Root TLV should contain the
root of the certificate chain of the certificate issued to the EAP
server packaged in a PKCS#7 TLV. If the Server certificate is a
self-signed certificate, then the root is the self-signed
certificate.
If the Trusted-Server-Root TLV credential format contains a value
unknown to the peer, then the EAP peer should ignore the TLV.
The Trusted-Server-Root TLV is defined as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 the single TEAP
packet. However, multiple EAP Payload TLVs, or multiple Basic
Password Authentication TLVs, or an EAP Payload TLV with a Basic
Password Authentication TLV within one single TEAP packet, is not
supported in this version and MUST NOT be sent. If the peer or EAP
server receives multiple EAP Payload TLVs, then it MUST terminate the
connection with the Result TLV. The order of TLVs in TEAP does not
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matter, except one should always process the Identity-Type TLV before
processing the EAP TLV or Basic Password Authentication TLV as the
Identity-Type TLV is a hint to the type of identity that is to be
authenticated.
The following table defines the meaning of the table entries in the
sections below:
0 This TLV MUST NOT be present in the message.
0+ Zero or more instances of this TLV MAY be present in the message.
0-1 Zero or one instance of this TLV MAY be present in the message.
1 Exactly one instance of this TLV MUST be present in the message.
4.3.1. Outer TLVs
The following table provides a guide to which TLVs may be included in
the TEAP packet outside the TLS channel, which kind of packets, and
in what quantity:
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 [NOTE1]
0+ 0+ 0+ 0+ Request-Action
0-1 0-1 0 0 EAP-Payload
0-1 0-1 0-1 0-1 Intermediate-Result
0+ 0+ 0+ 0 PAC-TLV
0-1 0-1 0-1 0-1 Crypto-Binding
0-1 0 0 0 Basic-Password-Auth-Req
0 0-1 0 0 Basic-Password-Auth-Resp
0-1 0 0-1 0 PKCS#7
0 0-1 0 0 PKCS#10
0-1 0-1 0-1 0 Server-Trusted-Root
[NOTE1] Vendor TLVs (included in Vendor-Specific TLVs) sent with a
Result TLV MUST be marked as optional.
5. Cryptographic Calculations
For key derivation and crypto-binding, TEAP uses the PRF and MAC
algorithms negotiated in the underlying TLS session. Since these
algorithms depend on the TLS version and cipher suite, TEAP
implementations need a mechanism to determine the version and cipher
suite 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 quantities are used as they are 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 (IMSK),
IMSK1..IMSKn, corresponding to inner method 1 through n.
If an inner method supports export of an Extended Master Session Key
(EMSK), then the IMSK SHOULD be derived from the EMSK as defined in
[RFC5295]. The usage label used is "TEAPbindkey@ietf.org" and the
length is 64 octets. Optional data parameter is not used in the
derivation.
IMSK = First 32 octets of KDF(EMSK, "TEAPbindkey@ietf.org" | "\0" |
64)
where "|" denotes concatenation, "EMSK" consists of the 4 ASCII
values for the letters, "\0" = is a NULL octet (0x00 in hex),
length is the 2-octet unsigned integer in network byte order, KDF
is defined in [RFC5295].
If an inner method does not support export of an Extended Master
Session Key (EMSK), then IMSK is the MSK of the inner method. The
MSK is truncated at 32 octets if it is longer than 32 octets or
padded to a length of 32 octets with zeros if it is less than 32
octets.
However, it's possible that the peer and server sides might not have
the same capability to export EMSK. In order to maintain maximum
flexibility while prevent downgrading attack, the following mechanism
is in place:
On the sender of the Crypto-Binding TLV side:
If the EMSK is not available, then computes the Compound MAC using
MSK of the inner method.
If the EMSK is available, and the sender's policy accepts MSK based
MAC, then it computes two Compound MAC values. The first is
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computed with the EMSK. The second one is computed using the MSK.
Both MACs are then sent to the other side.
If the EMSK is available, but the sender's policy does not allow
downgrade to MSK generated MAC, then it SHOULD only send EMSK based
MAC.
On the receiver of the Crypto-Binding TLV side:
If the EMSK is not available and a MSK based Compound MAC was sent,
validates the Compound MAC and sends back a MSK based Compound MAC
response.
If the EMSK is not available and no MSK based Compound MAC was
sent, then handles like an invalid Crypto-Binding TLV with fatal
error.
If the EMSK is available and an EMSK based Compound MAC was sent,
validates it and creates a response Compound MAC using the EMSK.
If the EMSK is available, but no EMSK based Compound MAC was sent,
and its policy accepts MSK based MAC, then validates it using the
MSK and if successful, generates and returns a MSK based Compound
MAC.
If the EMSK is available, but no EMSK Compound MAC was sent, and
its policy does not accept MSK based MAC, then it handles like an
invalid Crypto-Binding TLV with fatal error.
If the ith inner method does not generate an EMSK or MSK, then IMSKi
is set to zero (e.g., MSKi = 32 octets of 0x00s). If an inner method
fails, then it is not included in this calculation. The derivations
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
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TEAP Authentication assures the master session key (MSK) and Extended
Master Session Key (EMSK) output from the EAP method are the result
of all authentication conversations by generating an Intermediate
Compound Key (IMCK). The IMCK is mutually derived by the peer and
the server as described in Section 5.2 by combining the MSKs from
inner EAP methods with key material from TEAP Phase 1. The resulting
MSK and EMSK are generated as part of the IMCKn key hierarchy as
follows:
MSK = TLS-PRF(S-IMCK[j], "Session Key Generating Function", 64)
EMSK = TLS-PRF(S-IMCK[j],
"Extended Session Key Generating Function", 64)
where j is the number of the last successfully executed inner EAP
method.
The EMSK is typically only known to the TEAP peer and server and is
not provided to a third party. The derivation of additional keys and
transportation of these keys to a third party is outside the scope of
this document.
If no EAP methods have been negotiated inside the tunnel or no EAP
methods have been successfully completed inside the tunnel, the MSK
and EMSK will be generated directly from the session_key_seed meaning
S-IMCK = session_key_seed.
6. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to the TEAP
protocol, in accordance with BCP 26, [RFC5226].
The EAP Method Type number for TEAP needs to be assigned.
The document defines a registry for TEAP TLV types, which may be
assigned by Specification Required as defined in [RFC5226].
Section 4.2 defines the TLV types that initially populate the
registry. A summary of the TEAP TLV types is given below:
0 Unassigned
1 Authority-ID TLV
2 Identity-Type TLV
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3 Result TLV
4 NAK TLV
5 Error TLV
6 Channel-Binding TLV
7 Vendor-Specific TLV
8 Request-Action TLV
9 EAP-Payload TLV
10 Intermediate-Result TLV
11 PAC TLV
12 Crypto-Binding TLV
13 Basic-Password-Auth-Req TLV
14 Basic-Password-Auth-Resp TLV
15 PKCS#7 TLV
16 PKCS#10 TLV
17 Trusted-Server-Root TLV
The Identity-Type defined in Section 4.2.3 contains an Identity Type
code which is assigned on a Specification Required basis as defined
in [RFC5226]. The initial types defined are:
1 User
2 Machine
The Result TLV defined in Section 4.2.4, Request-Action TLV defined
in Section 4.2.9, and Intermediate-Result TLV defined in
Section 4.2.11 contain a Status code which is assigned on a
Specification Required basis as defined in [RFC5226]. The initial
types defined are:
1 Success
2 Failure
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The Error-TLV defined in Section 4.2.6 requires an error-code. TEAP
Error-TLV error-codes are assigned based on Specification Required as
defined in [RFC5226]. The initial list of error codes is as follows:
1 User account expires soon
2 User account credential expires soon
3 User account authorisations 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 authorisation 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
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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]
2001 Tunnel Compromise Error
2002 Unexpected TLVs Exchanged
The Request-Action TLV defined in Section 4.2.9 contains an action
code which is assigned on a Specification Required basis as defined
in [RFC5226]. The initial actions defined are:
1 Process-TLV
2 Negotiate-EAP
The PAC Attribute defined in Section 4.2.12.1 contains a Type code
which is assigned on a Specification Required basis as defined in
[RFC5226]. The initial types defined are:
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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
The PAC-Type defined in Section 4.2.12.6 contains a Type code which
is assigned on a Specification Required basis as defined in
[RFC5226]. The initial types defined are:
1 Tunnel PAC
The Trusted-Server-Root TLV defined in Section 4.2.18 contains a
Credential-Format code which is assigned on a Specification Required
basis as defined in [RFC5226]. The initial types defined are:
1 PKCS#7-Server-Certificate-Root
The various values under Vendor-Specific TLV are assigned by Private
Use and do not need to be assigned by IANA.
TEAP registers the label "EXPORTER: teap session key seed" in the TLS
Exporter Label Registry [RFC5705]. This label is used in derivation
as defined in Section 5.1.
TEAP registers a TEAP binding usage label from the "USRK Key Labels"
name space defined in [RFC5295] with a value "TEAPbindkey@ietf.org".
7. Security Considerations
TEAP is designed with a focus on wireless media, where the medium
itself is inherent to eavesdropping. Whereas in wired media, an
attacker would have to gain physical access to the wired medium;
wireless media enables anyone to capture information as it is
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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].
7.1. Mutual Authentication and Integrity Protection
TEAP as a whole, provides message and integrity protection by
establishing a secure tunnel for protecting the authentication
method(s). The confidentiality and integrity protection is defined
by TLS and provides the same security strengths afforded by TLS
employing a strong entropy shared master secret. The integrity of
the key generating authentication methods executed within the TEAP
tunnel is verified through the calculation of the Crypto-Binding TLV.
This ensures that the tunnel endpoints are the same as the inner
method endpoints.
The Result TLV is protected and conveys the true Success or Failure
of TEAP, and should be used as the indicator of its success or
failure respectively. However, as EAP terminates with either a clear
text EAP Success or Failure, a peer will also receive a clear text
EAP Success or Failure. The received clear text EAP Success or
Failure MUST match that received in the Result TLV; the peer SHOULD
silently discard those clear text EAP success or failure messages
that do not coincide with the status sent in the protected Result
TLV.
7.2. Method Negotiation
As is true for any negotiated EAP protocol, NAK packets used to
suggest an alternate authentication method are sent unprotected and
as such, are subject to spoofing. During unprotected EAP method
negotiation, NAK packets may be interjected as active attacks to
negotiate down to a weaker form of authentication, such as EAP-MD5
(which only provides one-way authentication and does not derive a
key). Both the peer and server should have a method selection policy
that prevents them from negotiating down to weaker methods. Inner
method negotiation resists attacks because it is protected by the
mutually authenticated TLS tunnel established. Selection of TEAP as
an authentication method does not limit the potential inner
authentication methods, so TEAP should be selected when available.
An attacker cannot readily determine the inner EAP method used,
except perhaps by traffic analysis. It is also important that peer
implementations limit the use of credentials with an unauthenticated
or unauthorized server.
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7.3. Separation of Phase 1 and Phase 2 Servers
Separation of the TEAP Phase 1 from the Phase 2 conversation is NOT
RECOMMENDED. Allowing the Phase 1 conversation to be terminated at a
different server than the Phase 2 conversation can introduce
vulnerabilities if there is not a proper trust relationship and
protection for the protocol between the two servers. Some
vulnerabilities include:
o Loss of identity protection
o Offline dictionary attacks
o Lack of policy enforcement
o Man-in-the-middle attacks (as described in [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
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o Sequencing of EAP methods
o Strong mutually derived master session keys
o Acknowledged success/failure indication
o Faster re-authentications through session resumption
o Mitigation of dictionary attacks
o Mitigation of man-in-the-middle attacks
o Mitigation of some denial-of-service attacks
It should be noted that TEAP, as in many other authentication
protocols, a denial-of-service attack can be mounted by adversaries
sending erroneous traffic to disrupt the protocol. This is a problem
in many authentication or key agreement protocols and is therefore
noted for TEAP as well.
TEAP was designed with a focus on protected authentication methods
that typically rely on weak credentials, such as password-based
secrets. To that extent, the TEAP Authentication mitigates several
vulnerabilities, such as dictionary attacks, by protecting the weak
credential-based authentication method. The protection is based on
strong cryptographic algorithms in TLS to provide message
confidentiality and integrity. The keys derived for the protection
relies on strong random challenges provided by both peer and server
as well as an established key with strong entropy. Implementations
should follow the recommendation in [RFC4086] when generating random
numbers.
7.4.1. User Identity Protection and Verification
The initial identity request response exchange is sent in cleartext
outside the protection of TEAP. Typically the Network Access
Identifier (NAI) [RFC4282] in the identity response is useful only
for the realm information that is used to route the authentication
requests to the right EAP server. This means that the identity
response may contain an anonymous identity and just contain realm
information. In other cases, the identity exchange may be eliminated
altogether if there are other means for establishing the destination
realm of the request. In no case should an intermediary place any
trust in the identity information in the identity response since it
is unauthenticated and may not have any relevance to the
authenticated identity. TEAP implementations should not attempt to
compare any identity disclosed in the initial cleartext EAP Identity
response packet with those Identities authenticated in Phase 2.
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Identity request-response exchanges sent after the TEAP tunnel is
established are protected from modification and eavesdropping by
attackers.
Note that since TLS client certificates are sent in the clear, if
identity protection is required, then it is possible for the TLS
authentication to be re-negotiated after the first server
authentication. To accomplish this, the server will typically not
request a certificate in the server_hello, then after the
server_finished message is sent, and before TEAP Phase 2, the server
MAY send a TLS hello_request. This allows the peer to perform client
authentication by sending a client_hello if it wants to, or send a
no_renegotiation alert to the server indicating that it wants to
continue with TEAP Phase 2 instead. Assuming that the peer permits
renegotiation by sending a client_hello, then the server will respond
with server_hello, a certificate and certificate_request messages.
The peer replies with certificate, client_key_exchange and
certificate_verify messages. Since this re-negotiation occurs within
the encrypted TLS channel, it does not reveal client certificate
details. It is possible to perform certificate authentication using
an EAP method (for example: EAP-TLS) within the TLS session in TEAP
Phase 2 instead of using TLS handshake renegotiation.
7.4.2. Dictionary Attack Resistance
TEAP was designed with a focus on protected authentication methods
that typically rely on weak credentials, such as password-based
secrets. TEAP mitigates dictionary attacks by allowing the
establishment of a mutually authenticated encrypted TLS tunnel
providing confidentiality and integrity to protect the weak
credential based authentication method.
7.4.3. Protection against Man-in-the-Middle Attacks
Allowing methods to be executed both with and without the protection
of a secure tunnel opens up a possibility of a man-in-the-middle
attack. To avoid man-in-the-middle attacks it is recommended to
always deploy authentication methods with protection of TEAP. TEAP
provides protection from man-in-the-middle attacks even if a
deployment chooses to execute inner EAP methods both with and without
TEAP protection, TEAP prevents this attack in two ways:
1. By using the PAC-Key to mutually authenticate the peer and server
during TEAP Authentication Phase 1 establishment of a secure
tunnel.
2. By using the keys generated by the inner authentication method
(if the inner methods are key generating) in the crypto-binding
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exchange and in the generation of the key material exported by
the EAP method described in Section 5.
TEAP crypto binding does not guarantee man-in-the-middle protection
if the client does not validate the server's certificate. If the TLS
cipher suite derives the master secret solely from the contribution
of secret data from one side of the conversation (such as RSA key
transport based ciphersuites) then an attacker can insert themselves
in the conversation if the server certificate is not verified 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 Diffie-
Hellman based cipher suites) 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 Clear Text EAP Packets
EAP Success and EAP Failure packets are, in general, sent in clear
text and may be forged by an attacker without detection. Forged EAP
Failure packets can be used to attempt to convince an EAP peer to
disconnect. Forged EAP Success packets may be used to attempt to
convince a peer that authentication has succeeded, even though the
authenticator has not authenticated itself to the peer.
By providing message confidentiality and integrity, TEAP provides
protection against these attacks. Once the peer and AS initiate the
TEAP Authentication Phase 2, compliant TEAP implementations MUST
silently discard all clear text EAP messages, unless both the TEAP
peer and server have indicated success or failure using a protected
mechanism. Protected mechanisms include TLS alert mechanism and the
protected termination mechanism described in Section 3.3.3.
The success/failure decisions within the TEAP tunnel indicate the
final decision of the TEAP authentication conversation. After a
success/failure result has been indicated by a protected mechanism,
the TEAP peer can process unprotected EAP Success and EAP Failure
messages; however the peer MUST ignore any unprotected EAP success or
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failure messages where the result does not match the result of the
protected mechanism.
To abide by [RFC3748], the server sends a clear text EAP Success or
EAP Failure packet to terminate the EAP conversation. However, since
EAP Success and EAP Failure packets are not retransmitted, the final
packet may be lost. While a TEAP protected EAP Success or EAP
Failure packet should not be a final packet in a TEAP conversation,
it may occur based on the conditions stated above, so an EAP peer
should not rely upon the unprotected EAP success and failure
messages.
7.6. Server Certificate Validation
As part of the TLS negotiation, the server presents a certificate to
the peer. The peer SHOULD verify the validity of the EAP server
certificate, and SHOULD also examine the EAP server name presented in
the certificate, in order to determine whether the EAP server can be
trusted. When performing server certificate validation
implementations MUST provide support rules in [RFC5280] for
validating certificates against a known trust anchor. In addition,
implementations MUST support matching the realm portion of the peer's
NAI against a SubjectAltName of type dNSName within the server
certificate. However, in certain deployments, this might not be
turned on. Please note that in the case where the EAP authentication
is 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 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
Notes
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1. BCP 86 [RFC3766] offers advice on appropriate key sizes. The
National Institute for Standards and Technology (NIST) also
offers advice on appropriate key sizes in [NIST-SP-800-57].
[RFC3766] Section 5 advises use of the following required RSA or
DH module and DSA subgroup size in bits, for a given level of
attack resistance in bits. Based on the table below, a 2048-bit
RSA key is required to provide 128-bit equivalent key strength:
Attack Resistance RSA or DH Modulus DSA subgroup
(bits) size (bits) size (bits)
----------------- ----------------- ------------
70 947 129
80 1228 148
90 1553 167
100 1926 186
150 4575 284
200 8719 383
250 14596 482
8. Acknowledgements
The TEAP v1 design and protocol specification is based on EAP-FAST
[RFC4851], which included the ideas and hard efforts of Nancy Cam-
Winget, David McGrew, Joe Salowey, Hao Zhou, Pad Jakkahalli, Mark
Krischer, Doug Smith, and Glen Zorn of Cisco Systems, Inc.
The TLV processing was inspired from work on the Protected Extensible
Authentication Protocol version 2 (PEAPv2) with Ashwin Palekar, Dan
Smith, Sean Turner and Simon Josefsson.
Helpful review comments were provided by Russ Housley, Jari Arkko,
Ilan Frenkel, Jeremy Steiglitz, Dan Harkins, Sam Hartman, Jim Schaad,
Barry Leiba, Stephen Farrell, Chris Lonvick and Josh Howlett.
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.
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[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5295] Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri,
"Specification for the Derivation of Root Keys from an
Extended Master Session Key (EMSK)", RFC 5295, August
2008.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, March 2010.
[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
"Transport Layer Security (TLS) Renegotiation Indication
Extension", RFC 5746, February 2010.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, July 2010.
[RFC6677] Hartman, S., Clancy, T., and K. Hoeper, "Channel-Binding
Support for Extensible Authentication Protocol (EAP)
Methods", RFC 6677, July 2012.
9.2. Informative References
[IEEE.802-1X.2004]
"Local and Metropolitan Area Networks: Port-Based Network
Access Control", IEEE Standard 802.1X, December 2004.
[NIST-SP-800-57]
National Institute of Standards and Technology,
"Recommendation for Key Management", NIST Special
Publication 800-57, May 2006.
[PEAP] Microsoft Corporation, "[MS-PEAP]: Protected Extensible
Authentication Protocol (PEAP) Specification", August
2009.
[RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", RFC 2315, March 1998.
[RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
Classes and Attribute Types Version 2.0", RFC 2985,
November 2000.
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[RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986,
November 2000.
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible
Authentication Protocol (EAP)", RFC 3579, September 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For
Public Keys Used For Exchanging Symmetric Keys", BCP 86,
RFC 3766, April 2004.
[RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. 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.
[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.
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[RFC5281] Funk, P. and S. Blake-Wilson, "Extensible Authentication
Protocol Tunneled Transport Layer Security Authenticated
Protocol Version 0 (EAP-TTLSv0)", RFC 5281, August 2008.
[RFC5421] Cam-Winget, N. and H. Zhou, "Basic Password Exchange
within the Flexible Authentication via Secure Tunneling
Extensible Authentication Protocol (EAP-FAST)", RFC 5421,
March 2009.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009.
[RFC5931] Harkins, D. and G. Zorn, "Extensible Authentication
Protocol (EAP) Authentication Using Only a Password", RFC
5931, August 2010.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011.
[RFC6124] Sheffer, Y., Zorn, G., Tschofenig, H., 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.
[X.690] ITU-T, "ITU-T Recommendation X.690 ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T 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
TEAP v1 meets this requirement by being compliant to RFC 3748, RFC
4017, RFC 5247, and RFC 4962. It is also compliant with the
"cryptographic algorithm agility" requirement by leveraging TLS 1.2
for all cryptographic algorithm negotiation.
A.2. Requirement 4.2.1 TLS Requirements
Requirement 4.2.1 states:
The tunnel based method MUST support TLS version 1.2 [RFC5246] and
may support earlier versions greater than SSL 2.0 to enable the
possibility of backwards compatibility.
TEAP v1 meets this requirement by mandating TLS version 1.2 support
as defined in Section 3.2.
A.3. Requirement 4.2.1.1.1 Cipher Suite Negotiation
Requirement 4.2.1.1.1 states:
Hence, the tunnel method MUST provide integrity protected cipher
suite negotiation with secure integrity algorithms and integrity
keys.
TEAP v1 meets this requirement by using TLS to provide protected
cipher suite negotiation.
A.4. Requirement 4.2.1.1.2 Tunnel Data Protection Algorithms
Requirement 4.2.1.1.2 states:
The tunnel method MUST provide at least one mandatory to implement
cipher suite that provides the equivalent security of 128-bit AES for
encryption and message authentication.
TEAP v1 meets this requirement by mandating
TLS_RSA_WITH_AES_128_CBC_SHA as a mandatory to implement cipher suite
as defined in Section 3.2.
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A.5. Requirement 4.2.1.1.3 Tunnel Authentication and Key Establishment
TEAP v1 meets this requirement by mandating
TLS_RSA_WITH_AES_128_CBC_SHA as a mandatory to implement cipher suite
which provides certificate-based authentication of the server and is
approved by NIST. The mandatory to implement cipher suites only
include cipher suites that use strong cryptographic algorithms. They
do not include cipher suites providing mutually anonymous
authentication or static Diffie-Hellman cipher suites as defined in
Section 3.2.
A.6. Requirement 4.2.1.2 Tunnel Replay Protection
TEAP v1 meets this requirement by using TLS to provide sufficient
replay protection.
A.7. Requirement 4.2.1.3 TLS Extensions
TEAP v1 meets this requirement by allowing TLS extensions, such as
TLS Certificate Status Request extension [RFC6066] and SessionTicket
extension [RFC5077] to be used during TLS tunnel establishment.
A.8. Requirement 4.2.1.4 Peer Identity Privacy
TEAP v1 meets this requirement by establishment of the TLS tunnel and
protection of inner method specific identities. In addition, the
peer certificate can be sent confidentially (i.e. encrypted).
A.9. Requirement 4.2.1.5 Session Resumption
TEAP v1 meets this requirement by mandating support of TLS session
resumption as defined in Section 3.2.1 and TLS Session Resume Using a
PAC as defined in Section 3.2.2 .
A.10. Requirement 4.2.2 Fragmentation
TEAP v1 meets this requirement by leveraging fragmentation support
provided by TLS as defined in Section 3.7.
A.11. Requirement 4.2.3 Protection of Data External to Tunnel
TEAP v1 meets this requirement by including TEAP version number
received in the computation of crypto-binding TLV as defined in
Section 4.2.13.
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A.12. Requirement 4.3.1 Extensible Attribute Types
TEAP v1 meets this requirement by using an extensible TLV data layer
inside the tunnel as defined in Section 4.2.
A.13. Requirement 4.3.2 Request/Challenge Response Operation
TEAP v1 meets this requirement by allowing multiple TLVs to be sent
in a single EAP request or response packet, while maintaining the
half-duplex operation typical of EAP.
A.14. Requirement 4.3.3 Indicating Criticality of Attributes
TEAP v1 meets this requirement by having a mandatory bit in TLV to
indicate whether it is mandatory to support or not as defined in
Section 4.2.
A.15. Requirement 4.3.4 Vendor Specific Support
TEAP v1 meets this requirement by having a Vendor-Specific TLV to
allow vendors to define their own attributes as defined in
Section 4.2.8.
A.16. Requirement 4.3.5 Result Indication
TEAP v1 meets this requirement by having a Result TLV to exchange the
final result of the EAP authentication so both the peer and server
have a synchronized state as defined in Section 4.2.4.
A.17. Requirement 4.3.6 Internationalization of Display Strings
TEAP v1 meets this requirement by supporting UTF-8 format in Basic-
Password-Auth-Req TLV as defined in Section 4.2.14 and Basic-
Password-Auth-Resp TLV as defined in Section 4.2.15.
A.18. Requirement 4.4 EAP Channel Binding Requirements
TEAP v1 meets this requirement by having a Channel-Binding TLV to
exchange the EAP channel binding data as defined in Section 4.2.7.
A.19. Requirement 4.5.1.1 Confidentiality and Integrity
TEAP v1 meets this requirement by running the password authentication
inside a protected TLS tunnel.
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A.20. Requirement 4.5.1.2 Authentication of Server
TEAP v1 meets this requirement by mandating authentication of the
server before establishment of the protected TLS and then running
inner password authentication as defined in Section 3.2.
A.21. Requirement 4.5.1.3 Server Certificate Revocation Checking
TEAP v1 meets this requirement by supporting TLS Certificate Status
Request extension [RFC6066] during tunnel establishment.
A.22. Requirement 4.5.2 Internationalization
TEAP v1 meets this requirement by supporting UTF-8 format in Basic-
Password-Auth-Req TLV as defined in Section 4.2.14 and Basic-
Password-Auth-Resp TLV as defined in Section 4.2.15.
A.23. Requirement 4.5.3 Meta-data
TEAP v1 meets this requirement by supporting Identity-Type TLV as
defined in Section 4.2.3 to indicate whether the authentication is
for a user or a machine.
A.24. Requirement 4.5.4 Password Change
TEAP v1 meets this requirement by supporting multiple Basic-Password-
Auth-Req TLV and Basic-Password-Auth-Resp TLV exchanges within a
single EAP authentication, which allows "housekeeping"" functions
such as password change.
A.25. Requirement 4.6.1 Method Negotiation
TEAP v1 meets this requirement by supporting inner EAP method
negotiation within the protected TLS tunnel.
A.26. Requirement 4.6.2 Chained Methods
TEAP v1 meets this requirement by supporting inner EAP method
chaining within protected TLS tunnel as defined in Section 3.3.1.
A.27. Requirement 4.6.3 Cryptographic Binding with the TLS Tunnel
TEAP v1 meets this requirement by supporting cryptographic binding of
the inner EAP method keys with the keys derived from the TLS tunnel
as defined in Section 4.2.13.
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A.28. Requirement 4.6.4 Peer Initiated
TEAP v1 meets this requirement by supporting Request-Action TLV as
defined in Section 4.2.9 to allow peer to initiate another inner EAP
method.
A.29. Requirement 4.6.5 Method Meta-data
TEAP v1 meets this requirement by supporting Identity-Type TLV as
defined in Section 4.2.3 to indicate whether the authentication is
for a user or a machine.
Appendix B. Major Differences from EAP-FAST
This document is a new standard tunnel EAP method based on revision
of the EAP-FAST version 1 [RFC4851] which contains improved
flexibility, particularly for negotiation of cryptographic
algorithms. The major changes are:
1. The EAP method name have been changed from EAP-FAST to TEAP,
hence it would require a new EAP method type to be assigned.
2. This version of TEAP MUST support TLS 1.2 [RFC5246].
3. The key derivation now makes use of TLS keying material exporters
[RFC5705] and the PRF and hash function negotiated in TLS. This
is to simplify implementation and better support cryptographic
algorithm agility.
4. TEAP is in full conformance with TLS Ticket extension [RFC5077]
as described in Section 3.2.2.
5. Support of passing optional outer TLVs in the first two message
exchanges, in addition to the Authority-ID TLV data in EAP-FAST.
6. Basic password authentication on the TLV level has been added in
addition to the existing inner EAP method.
7. Additional TLV types have been defined to support EAP channel
binding and meta-data. They are Identity-Type TLV and Channel-
Binding TLVs, defined in Section 4.2.
Appendix C. Examples
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C.1. Successful Authentication
The following exchanges show a successful TEAP authentication with
basic password authentication and optional PAC refreshment, the
conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID1) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello with
PAC-Opaque in SessionTicket extension)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
(TLS change_cipher_spec,
TLS finished)
EAP-Response/
EAP-Type=TEAP, V=1 ->
(TLS change_cipher_spec,
TLS finished)
TLS channel established
(messages sent within the TLS channel)
<- Basic-Password-Auth-Req TLV, Challenge
Basic-Password-Auth-Resp TLV, Response with both
user name and password) ->
optional additional exchanges (new pin mode,
password change etc.) ...
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<- Crypto-Binding TLV (Request),
Result TLV (Success),
(Optional PAC TLV)
Crypto-Binding TLV(Response),
Result TLV (Success),
(PAC TLV Acknowledgment) ->
TLS channel torn down
(messages sent in clear text)
<- EAP-Success
C.2. Failed Authentication
The following exchanges show a failed TEAP authentication due to
wrong user credentials, the conversation will appear as follows:
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Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID1) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello with
PAC-Opaque in SessionTicket extension)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
(TLS change_cipher_spec,
TLS finished)
EAP-Response/
EAP-Type=TEAP, V=1 ->
(TLS change_cipher_spec,
TLS finished)
TLS channel established
(messages sent within the TLS channel)
<- Basic-Password-Auth-Req TLV, Challenge
Basic-Password-Auth-Resp TLV, Response with both
user name and password) ->
<- Result TLV (Failure)
Result TLV (Failure) ->
TLS channel torn down
(messages sent in clear text)
<- EAP-Failure
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C.3. Full TLS Handshake using Certificate-based Cipher Suite
In the case where an abbreviated TLS handshake is tried and failed
and falls back to certificate based full TLS handshake occurs within
TEAP Phase 1, the conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/Identity
EAP-Response/
Identity (MyID1) ->
// Identity sent in the clear. May be a hint to help route
the authentication request to EAP server, instead of the
full user identity.
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello
[PAC-Opaque extension])->
// Peer sends PAC-Opaque of Tunnel PAC along with a list of
ciphersuites supported. If the server rejects the PAC-
Opaque, if falls through to the full TLS handshake
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
EAP-Response/
EAP-Type=TEAP, V=1
([TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
EAP-Payload-TLV[EAP-Request/
Identity])
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// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload-TLV
[EAP-Response/Identity (MyID2)]->
// identity protected by TLS.
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
// Method X exchanges followed by Protected Termination
<- Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Request),
Result TLV (Success)
Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Response),
Result-TLV (Success) ->
// TLS channel torn down
(messages sent in clear text)
<- EAP-Success
C.4. Client authentication during Phase 1 with identity privacy
In the case where a certificate based TLS handshake occurs within
TEAP Phase 1, and client certificate authentication and identity
privacy is desired, therefore TLS renegotiation is being used to
transmit the peer credentials in the protected TLS tunnel, the
conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/Identity
EAP-Response/
Identity (MyID1) ->
// Identity sent in the clear. May be a hint to help route
the authentication request to EAP server, instead of the
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full user identity.
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_key_exchange,
TLS change_cipher_spec,
TLS finished) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
EAP-Payload-TLV[EAP-Request/
Identity])
// TLS channel established
(EAP Payload messages sent within the TLS channel)
// peer sends TLS client_hello to request TLS renegotiation
TLS client_hello ->
<- TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done
[TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished ->
<- TLS change_cipher_spec,
TLS finished,
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Crypto-Binding TLV (Request),
Result TLV (Success)
Crypto-Binding TLV (Response),
Result-TLV (Success)) ->
//TLS channel torn down
(messages sent in clear text)
<- EAP-Success
C.5. Fragmentation and Reassembly
In the case where TEAP fragmentation is required, the conversation
will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
(Fragment 1: L, M bits set)
EAP-Response/
EAP-Type=TEAP, V=1 ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(Fragment 2: M bit set)
EAP-Response/
EAP-Type=TEAP, V=1 ->
<- EAP-Request/
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EAP-Type=TEAP, V=1
(Fragment 3)
EAP-Response/
EAP-Type=TEAP, V=1
([TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished)
(Fragment 1: L, M bits set)->
<- EAP-Request/
EAP-Type=TEAP, V=1
EAP-Response/
EAP-Type=TEAP, V=1
(Fragment 2)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
[EAP-Payload-TLV[
EAP-Request/Identity]])
// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload-TLV
[EAP-Response/Identity (MyID2)]->
// identity protected by TLS.
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
// Method X exchanges followed by Protected Termination
<- Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Request),
Result TLV (Success)
Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Response),
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Result-TLV (Success) ->
// TLS channel torn down
(messages sent in clear text)
<- EAP-Success
C.6. Sequence of EAP Methods
When TEAP is negotiated, with a sequence of EAP method X followed by
method Y, the conversation will occur as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID1) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
EAP-Response/
EAP-Type=TEAP, V=1
([TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
Identity-Type TLV,
EAP-Payload-TLV[
EAP-Request/Identity])
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// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
Identity_Type TLV
EAP-Payload-TLV
[EAP-Response/Identity] ->
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
// Optional additional X Method exchanges...
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X]->
<- Intermediate Result TLV (Success),
Crypto-Binding TLV (Request),
Identity-Type TLV,
EAP Payload TLV [EAP-Type=Y],
// Next EAP conversation started after successful completion
of previous method X. The Intermediate-Result and Crypto-
Binding TLVs are sent in next packet to minimize round-
trips. In this example, identity request is not sent
before negotiating EAP-Type=Y.
// Compound MAC calculated using Keys generated from
EAP methods X and the TLS tunnel.
Intermediate Result TLV (Success),
Crypto-Binding TLV (Response),
EAP-Payload-TLV [EAP-Type=Y] ->
// Optional additional Y Method exchanges...
<- EAP Payload TLV [
EAP-Type=Y]
EAP Payload TLV
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[EAP-Type=Y] ->
<- Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Request),
Result TLV (Success)
Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Response),
Result-TLV (Success) ->
// Compound MAC calculated using Keys generated from EAP
methods X and Y and the TLS tunnel. Compound Keys
generated using Keys generated from EAP methods X and Y;
and the TLS tunnel.
// TLS channel torn down (messages sent in clear text)
<- EAP-Success
C.7. Failed Crypto-binding
The following exchanges show a failed crypto-binding validation. The
conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID1) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello without
PAC-Opaque extension)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS Server Key Exchange
TLS Server Hello Done)
EAP-Response/
EAP-Type=TEAP, V=1 ->
(TLS Client Key Exchange
TLS change_cipher_spec,
TLS finished)
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<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec
TLS finished)
EAP-Payload-TLV[
EAP-Request/Identity])
// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload TLV/
EAP Identity Response ->
<- EAP Payload TLV, EAP-Request,
(EAP-MSCHAPV2, Challenge)
EAP Payload TLV, EAP-Response,
(EAP-MSCHAPV2, Response) ->
<- EAP Payload TLV, EAP-Request,
(EAP-MSCHAPV2, Success Request)
EAP Payload TLV, EAP-Response,
(EAP-MSCHAPV2, Success Response) ->
<- Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Request),
Result TLV (Success)
Intermediate-Result-TLV (Success),
Result TLV (Failure)
Error TLV with
(Error Code = 2001) ->
// TLS channel torn down
(messages sent in clear text)
<- EAP-Failure
C.8. Sequence of EAP Method with Vendor-Specific TLV Exchange
When TEAP is negotiated, with a sequence of EAP method followed by
Vendor-Specific TLV exchange, the conversation will occur as follows:
Authenticating Peer Authenticator
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------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID1) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
EAP-Response/
EAP-Type=TEAP, V=1
([TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
EAP-Payload-TLV[
EAP-Request/Identity])
// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload-TLV
[EAP-Response/Identity] ->
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
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<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X]->
<- Intermediate Result TLV (Success),
Crypto-Binding TLV (Request),
Vendor-Specific TLV,
// Vendor Specific TLV exchange started after successful
completion of previous method X. The Intermediate-Result
and Crypto-Binding TLVs are sent with Vendor Specific TLV
in next packet to minimize round-trips.
// Compound MAC calculated using Keys generated from
EAP methods X and the TLS tunnel.
Intermediate Result TLV (Success),
Crypto-Binding TLV (Response),
Vendor-Specific TLV ->
// Optional additional Vendor-Specific TLV exchanges...
<- Vendor-Specific TLV
Vendor Specific TLV ->
<- Result TLV (Success)
Result-TLV (Success) ->
// TLS channel torn down (messages sent in clear text)
<- EAP-Success
C.9. Peer Requests Inner Method After Server Sends Result TLV
In the case where the peer is authenticated during Phase 1 and server
sends back result TLV, but the peers wants to request another inner
method, the conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/Identity
EAP-Response/
Identity (MyID1) ->
// Identity sent in the clear. May be a hint to help route
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the authentication request to EAP server, instead of the
full user identity.
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
EAP-Response/
EAP-Type=TEAP, V=1
[TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
Crypto-Binding TLV (Request),
Result TLV (Success))
// TLS channel established
(TLV Payload messages sent within the TLS channel)
Crypto-Binding TLV(Response),
Request-Action TLV
(Status=Failure, Action=Negotiate-EAP)->
<- EAP-Payload-TLV
[EAP-Request/Identity]
EAP-Payload-TLV
[EAP-Response/Identity] ->
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
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<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X]->
<- Intermediate Result TLV (Success),
Crypto-Binding TLV (Request),
Result TLV (Success)
Intermediate Result TLV (Success),
Crypto-Binding TLV (Response),
Result-TLV (Success)) ->
//TLS channel torn down
(messages sent in clear text)
<- EAP-Success
C.10. Channel Binding
The following exchanges show a successful TEAP authentication with
basic password authentication and channel binding using Request-
Action TLV, the conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/
Identity
EAP-Response/
Identity (MyID1) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello with
PAC-Opaque in SessionTicket extension)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
(TLS change_cipher_spec,
TLS finished)
EAP-Response/
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EAP-Type=TEAP, V=1 ->
(TLS change_cipher_spec,
TLS finished)
TLS channel established
(messages sent within the TLS channel)
<- Basic-Password-Auth-Req TLV, Challenge
Basic-Password-Auth-Resp TLV, Response with both
user name and password) ->
optional additional exchanges (new pin mode,
password change etc.) ...
<- Crypto-Binding TLV (Request),
Result TLV (Success),
Crypto-Binding TLV(Response),
Request-Action TLV
(Status=Failure, Action=Process-TLV,
TLV=Channel-Binding TLV)->
<- Channel-Binding TLV (Response),
Result TLV (Success),
Result-TLV (Success) ->
TLS channel torn down
(messages sent in clear text)
<- EAP-Success
Appendix D. Major Differences from Previous Revisions
D.1. Changes from -06
1 Removed Design Goals
2 Added restriction on ciphersuites that do not provide
confidentiality in section 3.2
3 Added clarification of TLS unique used during certificate
provisioning in section 3.8.2
4 Specified DER encoding for PKCS#7 and PKCS#10 TLVs
5 Removed details of PKCS#7 package to RFC5652
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6 Moved RFC 4851 to informative reference
7 Additional editorial changes to address Security AD review
comments.
D.2. Changes from -05
1 Section 3.3.3, clarified that Intermediate Result TLV and Crypto-
Binding TLV MUST be exchanged after each EAP method, even with a
single inner EAP method.
2 Section 3.5, clarified that tls-unique is from Phase outer TLS
tunnel before beginning of the Phase 2.
3 Section 3.6.3, added text to handle processing inner method error.
4 Section 3.8, added a section titled Peer Services, stressing
mutual authentication before rest of peer services.
5 Section 3.8,4, added a section describing channel binding flows.
6 Section 7.6, changed SHOULD to MUST for matching server
certificate realm portion.
7 Update references from I-Ds to RFCs.
D.3. Changes from -04
1 Section 3.2, clarified that requesting new PAC in abbreviated
handshake is not permitted.
2 Section 3.6.2, clarified that TLS restart is not allowed for fatal
Alerts.
3 Section 3.6.3, added text to handle processing inner method error.
4 Section 4.1, clarified Flags bit usage.
5 Section 4.2.3, clarified Identity-Type TLV usage.
6 Section 4.2.8, clarified mandatory bit in Vendor-Specific TLV.
7 Section 4.2.13, added Compound MAC presence indicator in Crypto-
Binding TLV.
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D.4. Changes from -03
1 Section 4.1, added optional Outer TLV Length field and flag in
TEAP packet format.
2 Section 4.3, added TLV processing rules and rules for outer TLVs.
3 Section 5.2, changed IMCK generation from MSK based to either EMSK
or MSK with corresponding rules.
4 Section 4.2.13, introduced two Compound MAC fields for Crypto-
Binding TLV.
5 Section 3.4, clarified that all authenticated Peer-Ids, Server-Ids
and their identity types need to be exported.
6 Section 5.1, changed TLS Keying Material Exporter label to
"EXPORTER: teap session key seed".
7 Section 4.2.9, clarified Request-Action TLV processing.
D.5. Changes from -02
1 Section 3.3.3, clarified protected termination and use of crypto-
binding TLV.
2 Section 3.5, changed Session ID to use tls-unique and added
reference to RFC5247.
3 Section 3.9, added the use of tls-unique to the certificate
enrollment request.
4 Section 4.2.9, modified Request-Action TLV to include Status code
and optional TLVs.
5 Section 3.4, clarified that all authenticated Peer-Ids need to be
exported.
6 Section 5.1, changed TLS Keying Material Exporter label to "teap
session key seed".
7 Section 5.2, changed Intermediate Compound Key Derivation from MSK
to EMSK generated by inner method.
8 Section 6, added missing IANA considerations.
9 Section 7.3, added more security considerations for separation of
Phase 1 and Phase 2 servers.
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10 Appendix C, updated examples with Request-Action TLV, channel
binding, and sending certificate after TLS renegotiation.
D.6. Changes from -01
1 In Version Negotiation section, clarified what the peer needs to
do if the supported version is higher than what the server
proposed.
2 Section 3.2, clarified the requirement for using anonymous cipher
suites.
3 Clarified that Crypto-binding TLV is always exchanged and
validated, even without inner methods.
4 Section 3.4, clarified that all authenticated Peer-Ids need to be
exported.
5 Clarified that channel-binding TLV can be used to transmit data
bidirectionally.
6 Updated obsolete RFC references
7 Renumbered TLVs to eliminate gaps
8 Updated examples with basic password authentication TLVs.
9 Added Certificate Provisioning Within the Tunnel.
10 Added Server Unauthenticated Provisioning Mode.
D.7. Changes from -00
1 Changed protocol name to TEAP: Tunnel EAP Method
2 Changed version of protocol to version 1
3 Revised introduction
4 Moved differences section to appendix
5 Revised design goals section
6 Revised PAC definition
7 Revised protocol description to be in line with RFC 5077 PAC
distribution
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8 Revised EAP Sequences Section
9 Added section on PAC provisioning within tunnel
10 Added outer TLVs to the message format
11 Renumbered TLVs
12 Included PAC TLVs
13 Added Authority ID TLV
14 Added PKCS#7 and server trust root TLV definitions
15 Added PKCS#10 TLV
16 PKCS#10 TLV
17 Added EAP-Type and outer TLVs to crypto binding compound MAC
Authors' Addresses
Hao Zhou
Cisco Systems
4125 Highlander Parkway
Richfield, OH 44286
US
EMail: hzhou@cisco.com
Nancy Cam-Winget
Cisco Systems
3625 Cisco Way
San Jose, CA 95134
US
EMail: ncamwing@cisco.com
Joseph Salowey
Cisco Systems
2901 3rd Ave
Seattle, WA 98121
US
EMail: jsalowey@cisco.com
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Stephen Hanna
Juniper Networks
79 Parsons Street
Brighton, MA 02135
US
EMail: shanna@juniper.net
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