Tunnel EAP Method (TEAP) Version 1
draft-ietf-emu-eap-tunnel-method-01
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (emu WG) | |
|---|---|---|---|
| Authors | Hao Zhou , Nancy Cam-Winget , Joseph A. Salowey , Steve Hanna | ||
| Last updated | 2011-10-20 (Latest revision 2011-05-13) | ||
| Stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-emu-eap-tunnel-method-01
EMU Working Group H. Zhou
Internet-Draft N. Cam-Winget
Intended status: Standards Track J. Salowey
Expires: April 22, 2012 Cisco Systems
S. Hanna
Juniper Networks
October 20, 2011
Tunnel EAP Method (TEAP) Version 1
draft-ietf-emu-eap-tunnel-method-01.txt
Abstract
This document defines the Tunnel Extensible Authentication Protocol
(TEAP) protocol version 1. TEAP is a tunnel based EAP method that
enables secure communication between a peer and a server by using the
Transport Layer Security (TLS) to establish a mutually authenticated
tunnel. Within the tunnel, Type-Length-Value (TLV) objects are used
to convey authentication related data between the EAP peer and the
EAP server.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 22, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Specification Requirements . . . . . . . . . . . . . . . . 5
1.2. Design Goals . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Architectural Model . . . . . . . . . . . . . . . . . . . 8
2.2. Protocol Layering Model . . . . . . . . . . . . . . . . . 9
3. TEAP Protocol . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Version Negotiation . . . . . . . . . . . . . . . . . . . 10
3.2. TEAP Authentication Phase 1: Tunnel Establishment . . . . 11
3.2.1. TLS Session Resume Using Server State . . . . . . . . 13
3.2.2. TLS Session Resume Using a PAC . . . . . . . . . . . . 13
3.2.3. Transition between Abbreviated and Full TLS
Handshake . . . . . . . . . . . . . . . . . . . . . . 14
3.3. TEAP Authentication Phase 2: Tunneled Authentication . . . 15
3.3.1. EAP Sequences . . . . . . . . . . . . . . . . . . . . 15
3.3.2. Optional Password Authentication . . . . . . . . . . . 16
3.3.3. Protected Termination and Acknowledged Result
Indication . . . . . . . . . . . . . . . . . . . . . . 16
3.4. Determining Peer-Id and Server-Id . . . . . . . . . . . . 17
3.5. TEAP Session Identifier . . . . . . . . . . . . . . . . . 18
3.6. Error Handling . . . . . . . . . . . . . . . . . . . . . . 18
3.6.1. TLS Layer Errors . . . . . . . . . . . . . . . . . . . 19
3.6.2. Phase 2 Errors . . . . . . . . . . . . . . . . . . . . 19
3.7. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 20
3.8. PAC Provisioning Within Tunnel . . . . . . . . . . . . . . 21
4. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 21
4.1. TEAP Message Format . . . . . . . . . . . . . . . . . . . 21
4.2. TEAP TLV Format and Support . . . . . . . . . . . . . . . 23
4.2.1. General TLV Format . . . . . . . . . . . . . . . . . . 24
4.2.2. Result TLV . . . . . . . . . . . . . . . . . . . . . . 26
4.2.3. NAK TLV . . . . . . . . . . . . . . . . . . . . . . . 27
4.2.4. Error TLV . . . . . . . . . . . . . . . . . . . . . . 29
4.2.5. Vendor-Specific TLV . . . . . . . . . . . . . . . . . 30
4.2.6. EAP-Payload TLV . . . . . . . . . . . . . . . . . . . 31
4.2.7. Intermediate-Result TLV . . . . . . . . . . . . . . . 32
4.2.8. PAC TLV Format . . . . . . . . . . . . . . . . . . . . 34
4.2.8.1. Formats for PAC Attributes . . . . . . . . . . . . 34
4.2.8.2. PAC-Key . . . . . . . . . . . . . . . . . . . . . 35
4.2.8.3. PAC-Opaque . . . . . . . . . . . . . . . . . . . . 36
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4.2.8.4. PAC-Info . . . . . . . . . . . . . . . . . . . . . 37
4.2.8.5. PAC-Acknowledgement TLV . . . . . . . . . . . . . 39
4.2.8.6. PAC-Type TLV . . . . . . . . . . . . . . . . . . . 40
4.2.9. Crypto-Binding TLV . . . . . . . . . . . . . . . . . . 40
4.2.10. Authority-ID TLV . . . . . . . . . . . . . . . . . . . 43
4.2.11. Request-Action TLV . . . . . . . . . . . . . . . . . . 44
4.2.12. Trusted-Server-Root TLV . . . . . . . . . . . . . . . 45
4.2.13. PKCS#7 TLV . . . . . . . . . . . . . . . . . . . . . . 46
4.2.14. PKCS#10 TLV . . . . . . . . . . . . . . . . . . . . . 47
4.2.15. Channel-Binding TLV . . . . . . . . . . . . . . . . . 48
4.2.16. Identity-Type TLV . . . . . . . . . . . . . . . . . . 49
4.2.17. Basic-Password-Auth-Req TLV . . . . . . . . . . . . . 50
4.2.18. Basic-Password-Auth-Resp TLV . . . . . . . . . . . . . 51
4.3. Table of TLVs . . . . . . . . . . . . . . . . . . . . . . 53
5. Cryptographic Calculations . . . . . . . . . . . . . . . . . . 53
5.1. TEAP Authentication Phase 1: Key Derivations . . . . . . . 53
5.2. Intermediate Compound Key Derivations . . . . . . . . . . 54
5.3. Computing the Compound MAC . . . . . . . . . . . . . . . . 54
5.4. EAP Master Session Key Generation . . . . . . . . . . . . 55
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56
7. Security Considerations . . . . . . . . . . . . . . . . . . . 57
7.1. Mutual Authentication and Integrity Protection . . . . . . 58
7.2. Method Negotiation . . . . . . . . . . . . . . . . . . . . 58
7.3. Separation of Phase 1 and Phase 2 Servers . . . . . . . . 59
7.4. Mitigation of Known Vulnerabilities and Protocol
Deficiencies . . . . . . . . . . . . . . . . . . . . . . . 59
7.4.1. User Identity Protection and Verification . . . . . . 60
7.4.2. Dictionary Attack Resistance . . . . . . . . . . . . . 61
7.4.3. Protection against Man-in-the-Middle Attacks . . . . . 61
7.4.4. PAC Binding to User Identity . . . . . . . . . . . . . 62
7.5. Protecting against Forged Clear Text EAP Packets . . . . . 62
7.6. Server Certificate Validation . . . . . . . . . . . . . . 62
7.7. Tunnel PAC Considerations . . . . . . . . . . . . . . . . 63
7.8. Security Claims . . . . . . . . . . . . . . . . . . . . . 63
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 65
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.1. Normative References . . . . . . . . . . . . . . . . . . . 65
9.2. Informative References . . . . . . . . . . . . . . . . . . 66
Appendix A. Evaluation Against Tunnel Based EAP Method
Requirements . . . . . . . . . . . . . . . . . . . . 68
A.1. Requirement 4.1.1 RFC Compliance . . . . . . . . . . . . . 68
A.2. Requirement 4.2.1 TLS Requirements . . . . . . . . . . . . 69
A.3. Requirement 4.2.1.1.1 Cipher Suite Negotiation . . . . . . 69
A.4. Requirement 4.2.1.1.2 Tunnel Data Protection Algorithms . 69
A.5. Requirement 4.2.1.1.3 Tunnel Authentication and Key
Establishment . . . . . . . . . . . . . . . . . . . . . . 69
A.6. Requirement 4.2.1.2 Tunnel Replay Protection . . . . . . . 70
A.7. Requirement 4.2.1.3 TLS Extensions . . . . . . . . . . . . 70
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A.8. Requirement 4.2.1.4 Peer Identity Privacy . . . . . . . . 70
A.9. Requirement 4.2.1.5 Session Resumption . . . . . . . . . . 70
A.10. Requirement 4.2.2 Fragmentation . . . . . . . . . . . . . 70
A.11. Requirement 4.2.3 Protection of Data External to Tunnel . 70
A.12. Requirement 4.3.1 Extensible Attribute Types . . . . . . . 70
A.13. Requirement 4.3.2 Request/Challenge Response Operation . . 70
A.14. Requirement 4.3.3 Indicating Criticality of Attributes . . 71
A.15. Requirement 4.3.4 Vendor Specific Support . . . . . . . . 71
A.16. Requirement 4.3.5 Result Indication . . . . . . . . . . . 71
A.17. Requirement 4.3.6 Internationalization of Display
Strings . . . . . . . . . . . . . . . . . . . . . . . . . 71
A.18. Requirement 4.4 EAP Channel Binding Requirements . . . . . 71
A.19. Requirement 4.5.1.1 Confidentiality and Integrity . . . . 71
A.20. Requirement 4.5.1.2 Authentication of Server . . . . . . . 71
A.21. Requirement 4.5.1.3 Server Certificate Revocation
Checking . . . . . . . . . . . . . . . . . . . . . . . . . 71
A.22. Requirement 4.5.2 Internationalization . . . . . . . . . 72
A.23. Requirement 4.5.3 Meta-data . . . . . . . . . . . . . . . 72
A.24. Requirement 4.5.4 Password Change . . . . . . . . . . . . 72
A.25. Requirement 4.6.1 Method Negotiation . . . . . . . . . . . 72
A.26. Requirement 4.6.2 Chained Methods . . . . . . . . . . . . 72
A.27. Requirement 4.6.3 Cryptographic Binding with the TLS
Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . 72
A.28. Requirement 4.6.4 Peer Initiated . . . . . . . . . . . . . 72
A.29. Requirement 4.6.5 Method Meta-data . . . . . . . . . . . . 72
Appendix B. Major Differences from EAP-FAST . . . . . . . . . . . 73
Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 73
C.1. Successful Authentication . . . . . . . . . . . . . . . . 73
C.2. Failed Authentication . . . . . . . . . . . . . . . . . . 75
C.3. Full TLS Handshake using Certificate-based Cipher Suite . 76
C.4. Client authentication during Phase 1 with identity
privacy . . . . . . . . . . . . . . . . . . . . . . . . . 78
C.5. Fragmentation and Reassembly . . . . . . . . . . . . . . . 79
C.6. Sequence of EAP Methods . . . . . . . . . . . . . . . . . 81
C.7. Failed Crypto-binding . . . . . . . . . . . . . . . . . . 83
C.8. Sequence of EAP Method with Vendor-Specific TLV
Exchange . . . . . . . . . . . . . . . . . . . . . . . . . 85
Appendix D. Major Differences from previous revisions . . . . . . 87
D.1. Changes from -00 . . . . . . . . . . . . . . . . . . . . . 87
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1. Introduction
An Extensible Authentication Protocol (EAP) tunnel method is an EAP
method that establishes a secure tunnel and executes other EAP
methods under the protection of that secure tunnel. An EAP tunnel
method can be used in any lower layer protocol that supports EAP
authentication. There are several existing EAP tunnel methods that
use Transport Layer Security (TLS) 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.
[I-D.ietf-emu-eaptunnel-req] outlines the list of requirements for a
standard tunnel based EAP method.
Since the introduction of EAP-FAST [RFC4851] a few years ago, it has
been widely adopted in variety of devices and platforms due to its
strong security, flexibility and ease of deployment. It has been
adopted by EMU working group as the basis for the standard tunnel
based EAP method. This document describes TEAP version 1, based on
EAP-FAST [RFC4851] with some minor changes, to meet the requirements
outlined in [I-D.ietf-emu-eaptunnel-req] for a standard tunnel based
EAP method.
1.1. Specification Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] .
1.2. Design Goals
Network access solutions requiring user friendly and easily
deployable secure authentication mechanisms highlight the need for
strong mutual authentication protocols that enable the use of weaker
user credentials. This document defines an Extensible Authentication
Protocol (EAP) which consists of establishing a Transport Layer
Security (TLS) tunnel using TLS 1.2 [RFC5246] or a successor version
of TLS, using the latest version supported by both parties. Once the
tunnel is established, the protocol further exchanges data in the
form of Type-Length-Value (TLV) objects to perform further
authentication. TEAP supports the TLS extension defined in [RFC5077]
to support fast re-establishment of the secure tunnel without having
to maintain per-session state on the server.
TEAP's design motivations included:
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o Mutual authentication: an EAP server must be able to verify the
identity and authenticity of the peer, and the peer must be able
to verify the authenticity of the EAP server.
o Immunity to passive dictionary attacks: many authentication
protocols require a password to be explicitly provided (either as
cleartext or hashed) by the peer to the EAP server; at minimum,
the communication of the weak credential (e.g., password) must be
immune from eavesdropping.
o Immunity to man-in-the-middle (MitM) attacks: in establishing a
mutually authenticated protected tunnel, the protocol must prevent
adversaries from successfully interjecting information into the
conversation between the peer and the EAP server.
o Flexibility to enable support for most password authentication
interfaces: as many different password interfaces (e.g., Microsoft
Challenge Handshake Authentication Protocol (MS-CHAP), Lightweight
Directory Access Protocol (LDAP), One-Time Password (OTP), etc.)
exist to authenticate a peer, the protocol must provide this
support for legacy password authentication seamlessly.
o Cryptographic algorithm agility: a cryptographic algorithm's
strength is not perpetual, as weaknesses in an algorithm are
discovered or increased processing power overtakes an algorithm
over time. Hence, the protocol must not be tied to any single
cryptographic algorithm. Instead, it MUST support run-time
negotiation to select among an extensible set of cryptographic
algorithms and also allow users to choose the algorithm that best
meets their needs.
o Sequence of chained EAP methods: Several circumstances are best
addressed by using chained EAP methods. For example, it may be
desirable to authenticate the user and also authenticate the
device being used. The protocol must support chained EAP methods
while including protection against attacks on method chaining.
With these motivational goals defined, further secondary design
criteria are imposed:
o Flexibility to extend the communications inside the tunnel: with
the growing complexity in network infrastructures, the need to
gain authentication, authorization, and accounting is also
evolving. For instance, there may be instances in which multiple
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existing authentication protocols are required to achieve mutual
authentication. Similarly, different protected conversations may
be required to achieve the proper authorization once a peer has
successfully authenticated.
o Minimize the authentication server's per user authentication state
requirements: with large deployments, it is typical to have
servers authenticating many peers. With many different
authentication servers deployed, a peer's session state may need
to be replicated to allow for high availability or mobility
scenarios. To facilitate scalable authentication server
deployments and more efficient per user state management, it is
desirable for a peer to cache its session state that has been
securely encapsulated by the authentication server infrastructure.
o Efficiency: specifically when using wireless media, peers will be
limited in computational and power resources. The protocol must
enable the network access communication to be computationally
lightweight.
o Channel bindings: EAP channel bindings seek to authenticate
previously unauthenticated information provided by the
authenticator to the EAP peer, by allowing the peer and server to
compare their perception of network properties in a secure
channel. It is used to solve the lying NAS and the lying provider
problems. The protocol should provide support for EAP channel
bindings as defined in [I-D.ietf-emu-chbind].
1.3. Terminology
Much of the terminology in this document comes from [RFC3748].
Additional terms are defined below:
Protected Access Credential (PAC)
Credentials distributed to a peer for future optimized network
authentication. The PAC consists of a minimum of two components:
a shared secret and an opaque element. The shared secret
component contains the pre-shared key between the peer and the
authentication server. The opaque part is provided to the peer
and is presented to the authentication server when the peer wishes
to obtain access to network resources. The opaque element and
shared secret are used with TLS stateless session resumption
defined in RFC 5077 [RFC5077] to establish a protected TLS
session. The secret key and opaque part may distributed using RFC
5077 messages or using TLVs within the TEAP tunnel. Finally, a
PAC may optionally include other information that may be useful to
the peer.
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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. In the first phase, TEAP
employs the TLS [RFC5246] handshake to provide an authenticated key
exchange and to establish a protected tunnel. Once the tunnel is
established, the second phase begins with the peer and server
engaging in further conversations to establish the required
authentication and authorization policies. TEAP makes use of Type-
Length-Value objects (TLVs) to carry out the inner authentication,
results and other information, such as channel binding information.
TEAP makes use of the TLS enhancements in Ticket Extension [RFC5077]
to enable an optimized TLS tunnel session resume while minimizing
server state. The ticket is referred to as the Protected Access
Credential opaque data (or PAC-Opaque). The PAC-Opaque may be
distributed through the use of the NewSessionTicket message or
through a mechanism that uses TLVs within phase 2 of TEAP. The
secret key used to resume the session in TEAP is referred to as the
Protected Access Credential key (or PAC-Key). When the
NewSessionTicket message is being used to distribute the PAC-Opaque
the PAC-Key is the Master Secret for the session. If TEAP phase 2 is
used to distribute the PAC-Opaque then the PAC-Key is distributed
along with the PAC-Opaque. TEAP implementations MUST support the RFC
5077 mechanism for distributing a PAC-Opaque and it is RECOMMENDED
that implementations support the capability to distribute the ticket
and secret key within the TEAP tunnel.
The TEAP conversation is used to establish or resume an existing
session to typically establish network connectivity between a peer
and the network. Upon successful execution of TEAP, both EAP peer
and EAP server derive strong session key material that can then be
communicated to the network access server (NAS) for use in
establishing a link layer security association.
2.1. Architectural Model
The network architectural model for TEAP usage is shown below:
+----------+ +----------+ +----------+ +----------+
| | | | | | | Inner |
| Peer |<---->| Authen- |<---->| TEAP |<---->| Method |
| | | ticator | | server | | server |
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| | | | | | | |
+----------+ +----------+ +----------+ +----------+
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
carrier protocol for transport. TEAP packets encapsulate TLS, which
is then used to encapsulate user authentication information. Thus,
TEAP messaging can be described using a layered model, where each
layer encapsulates the layer above it. The following diagram
clarifies the relationship between protocols:
+---------------------------------------------------------------+
| Inner EAP Method | Other TLV information |
|---------------------------------------------------------------|
| TLV Encapsulation (TLVs) |
|---------------------------------------------------------------|
| TLS | Optional TLVs |
|---------------------------------------------------------------|
| TEAP |
|---------------------------------------------------------------|
| EAP |
|---------------------------------------------------------------|
| Carrier Protocol (EAP over LAN, RADIUS, Diameter, etc.) |
+---------------------------------------------------------------+
Protocol Layering Model
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The TLV layer is a payload with Type-Length-Value (TLV) Objects
defined in Section 4.2. The TLV objects are used to carry arbitrary
parameters between an EAP peer and an EAP server. All conversations
in the TEAP protected tunnel must be encapsulated in a TLV layer.
TEAP packets may include TLVs both inside and outside the TLS tunnel.
The term "Outer TLVs" is used to refer to optional TLVs outside the
TLS tunnel, which are only allowed in the first two messages in the
TEAP protocol. That is the first EAP server to peer message and
first peer to EAP server message. If the message is fragmented, the
whole set of messages is counted as one message. The term "Inner
TLVs" is used to refer to TLVs sent within the TLS tunnel. In TEAP
Phase 1, Outer TLVs are used to help establishing the TLS tunnel, but
no Inner TLVs are used. In Phase 2 of the TEAP conversation, TLS
records may encapsulate zero or more Inner TLVs, but no Outer TLVs.
Methods for encapsulating EAP within carrier protocols are already
defined. For example, IEEE 802.1X [IEEE.802-1X.2004] may be used to
transport EAP between the peer and the authenticator; RADIUS
[RFC3579] or Diameter [RFC4072] may be used to transport EAP between
the authenticator and the EAP server.
3. TEAP Protocol
TEAP authentication occurs in two phases. In the first phase, TEAP
employs the TLS handshake to provide an authenticated key exchange
and to establish a protected tunnel. Once the tunnel is established
the second phase begins with the peer and server engaging in further
conversations to establish the required authentication and
authorization policies. The operation of the protocol, including
Phase 1 and Phase 2, is the topic of this section. The format of
TEAP messages is given in Section 4 and the cryptographic
calculations are given in Section 5.
3.1. Version Negotiation
TEAP packets contain a 3-bit version field, following the TLS Flags
field, which enables 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:
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In the first EAP-Request sent with EAP type=TEAP, the EAP server
must set the version field to the highest supported version
number.
If the EAP peer supports this version of the protocol, it MUST
respond with an EAP-Response of EAP type=TEAP, and the version
number proposed by the TEAP server.
If the TEAP peer does not support this version, it responds with
an EAP-Response of EAP type=TEAP and the highest supported version
number that's less than the number proposed by the TEAP server.
If the TEAP server does not support the version number proposed by
the TEAP peer, it MAY terminate the conversation with EAP-Failure
or negotiate for another EAP type. Otherwise the TEAP
conversation continues.
The version negotiation procedure guarantees that the TEAP peer and
server will agree to the latest version supported by both parties.
If version negotiation fails, then use of TEAP will not be possible,
and another mutually acceptable EAP method will need to be negotiated
if authentication is to proceed.
The TEAP version is not protected by TLS; and hence can be modified
in transit. In order to detect a modification of the TEAP version,
the peers MUST exchange the TEAP version number received during
version negotiation using the Crypto-Binding TLV described in
Section 4.2.9. The receiver of the Crypto-Binding TLV MUST verify
that the version received in the Crypto-Binding TLV matches the
version sent by the receiver in the TEAP version negotiation.
3.2. TEAP Authentication Phase 1: Tunnel Establishment
TEAP is based on the TLS handshake [RFC5246] to establish an
authenticated and protected tunnel. The TLS version offered by the
peer and server MUST be TLS version 1.2 [RFC5246] or later. This
version of the TEAP implementation MUST support the following TLS
ciphersuites:
TLS_RSA_WITH_AES_128_CBC_SHA [RFC3268]
TLS_DHE_RSA_WITH_AES_128_CBC_SHA [RFC3268]
Other ciphersuites MAY be supported. It is RECOMMENDED that
anonymous ciphersuites such as TLS_DH_anon_WITH_AES_128_CBC_SHA only
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be used in the case when the inner authentication method provides
man-in-the-middle protection [Editor's Note: The use of Anonymous
Cipher Suites is still under discussion on the list]. Care must be
taken to address potential man-in-the-middle attacks when
ciphersuites that do not provide authenticated tunnel establishment
are 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] can be used to leverage a certificate-status
protocol such as OCSP [RFC2560] to check the validity of server
certificates. TLS renegotiation indications defined in RFC 5746
[RFC5746] MUST be supported.
The EAP server initiates the TEAP conversation with an EAP request
containing an TEAP/Start packet. This packet includes a set Start
(S) bit, the TEAP version as specified in Section 3.1, and an
authority identity. The TLS payload in the initial packet is empty.
The authority identity (Authority-ID TLV) is used to provide the peer
a hint of the server's identity that may be useful in helping the
peer select the appropriate credential to use. Assuming that the
peer supports TEAP the conversation continues with the peer sending
an EAP-Response packet with EAP type of TEAP with the Start (S) bit
clear and the version as specified in Section 3.1. This message
encapsulates one or more TLS records containing the TLS handshake
messages. If the TEAP version negotiation is successful then the
TEAP conversation continues until the EAP server and EAP peer are
ready to enter Phase 2. When the full TLS handshake is performed,
then the first payload of TEAP Phase 2 MAY be sent along with server-
finished handshake message to reduce the number of round trips.
TEAP implementations MUST support client authentication during tunnel
establishment using the TLS ciphersuites specified in Section 3.2.
The EAP peer does not need to authenticate as part of the TLS
exchange, but can alternatively be authenticated through additional
EAP 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 must 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.
The following sections describe resuming a TLS session based on
server-side or client-side state.
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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
must 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 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 Authentication
Phase 1 tunnel establishment based on a TLS abbreviated handshake.
After a successful conclusion of the TEAP Authentication Phase 1
conversation, the conversation then continues on to Phase 2.
3.2.2. TLS Session Resume Using a PAC
TEAP supports the resumption of sessions based on client-side state
using the TLS SessionTicket extension techniques described in
[RFC5077]. This version of TEAP supports the provisioning of a
ticket called a Protected Access Credential (PAC) through the use of
the NewSessionTicket handshake described in [RFC5077], as well as
provisioning of a PAC inside the protected tunnel. Implementations
may provide additional ways to provision the PAC, such as manual
configuration. Since the PAC mentioned here is used for establishing
the TLS Tunnel, it is more specifically referred to as the Tunnel
PAC. The Tunnel PAC is a security credential provided by the EAP
server to a peer and comprised of:
1. PAC-Key: this is the key used by the peer as the TLS master
secret to establish the TEAP Phase 1 tunnel. The PAC-Key is a
strong high-entropy 48-octet key and is typically the master
secret from a previous TLS session. The PAC-Key is a secret and
MUST be treated accordingly. In the case that a PAC-Key is
provisioned to the client 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
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an attacker MUST NOT be able to gain useful information from the
PAC-Opaque itself. The server issuing the PAC-Opaque must 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.
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
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the ClientHello. If ChangeCipherSpec follows the ServerHello in
response to the ClientHello, then the server has accepted the session
resumption and intends to negotiate the abbreviated handshake.
Otherwise, the server intends to negotiate the full TLS handshake. A
peer can request for a new PAC to be provisioned after the full TLS
handshake and mutual authentication of the peer and the server. In
order to facilitate the fallback to a full handshake the peer SHOULD
include cipher suites that allow for a full handshake and possibly
PAC provisioning so the server can select one of these in case
session resumption fails. An example of the transition is shown in
Appendix C.
3.3. TEAP Authentication Phase 2: Tunneled Authentication
The second portion of the TEAP Authentication occurs immediately
after successful completion of Phase 1. Phase 2 occurs even if both
peer and authenticator are authenticated in the Phase 1 TLS
negotiation. Phase 2 MUST NOT occur if the Phase 1 TLS handshake
fails. Phase 2 consists of a series of requests and responses
encapsulated in TLV objects defined in Section 4.2. Phase 2 MUST
always end with a protected termination exchange described in
Section 3.3.3. The TLV exchange may include the execution of zero or
more EAP methods within the protected tunnel as described in
Section 3.3.1. A server MAY proceed directly to the protected
termination exchange if it does not wish to request further
authentication from the peer. However, the peer and server must not
assume that either will skip inner EAP methods or other TLV
exchanges. The peer may have roamed to a network that requires
conformance with a different authentication policy or the peer may
request the server take additional action through the use of the
Request-Action TLV.
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 4.2.6. If more than one method is going to be executed in
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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
a Crypto-Binding TLV. The Crypto-Binding TLV is further discussed in
Section 4.2.9 and Section 5.3. The Intermediate-Result TLVs can be
included with other TLVs such as EAP-Payload TLVs starting a new EAP
conversation or with the Result TLV used in the protected termination
exchange.
If both peer and server indicate success, then the method is
considered complete. If either indicates failure, then the method is
considered failed. The result of failure of an EAP method does not
always imply a failure of the overall authentication. If one
authentication method fails, the server may attempt to authenticate
the peer with a different method.
3.3.2. Optional Password Authentication
The use of EAP-FAST-GTC as defined in RFC 5421 [RFC5421] is not
recommended with TEAPv1. Implementations should instead make use of
the password authentication TLVs defined in this specification. The
authentication server initiates password authentication by sending a
Basic-Password-Auth-Req TLV defined in Section 4.2.17. If the peer
wishes to participate in password authentication then it responds
with a Basic-Password-Auth-Resp TLV as defined in Section 4.2.18 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 Result TLV exchange. An TEAP server may initiate the
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. The format of the Result TLV is described in Section 4.2.2.
A server initiates a successful protected termination exchange by
sending a Result TLV indicating success. The server may send the
Result TLV along with an Intermediate-Result TLV and a Crypto-Binding
TLV. If the peer requires nothing more from the server it will
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respond with a Result TLV indicating success accompanied by an
Intermediate-Result TLV and Crypto-Binding TLV if necessary. The
server then tears down the tunnel and sends a clear text EAP-Success.
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 along with
the Result TLV indicating what EAP Success/Failure result the peer
would expect if the requested action is not granted. The value of
the Request-Action TLV indicates what the peer would like to do next.
The format and values for the Request-Action TLV are defined in
Section 4.2.11.
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 value of the
peer's result 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 3.6.2.
3.4. Determining Peer-Id and Server-Id
The Peer-Id and Server-Id 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, the
Peer-ID is determined from the first peer authenticatication.
When X.509 certificates are used for peer authentication, the Peer-Id
is determined by the subject or subjectAltName fields in the peer
certificate. As noted in [RFC3280] (updated by [RFC4630]):
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.
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Where it is non-empty, the subject field MUST contain an X.500
distinguished name (DN).
If an inner EAP method is run, then the Peer-Id is obtained from the
inner method.
When the server uses an X.509 certificate to establish the TLS
tunnel, the Server-Id is determined in a similar fashion as stated
above for the Peer-Id; e.g., the subject or subjectAltName field in
the server certificate defines the Server-Id.
3.5. TEAP Session Identifier
The EAP session identifier is constructed using the random values
provided by the peer and server during the TLS tunnel establishment.
The randoms from the outermost TLS handshake are used in the case
that renegotiation is used. The Session-Id is defined as follows:
Session-Id = teap_type || client_random || server_random
type_type = EAP method type assigned to TEAP
client_random = 32 octet nonce generated by the peer for the
initial TLS handshake
server_random = 32 octet nonce generated by the server for the
initial TLS handshake
3.6. Error Handling
TEAP uses the following error handling rules summarized below:
1. Errors in the TLS layer are communicated via TLS alert messages
in all phases of TEAP.
2. 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.
3. Violations of the TLV rules are handled using Result TLVs
together with Error TLVs.
4. Tunnel compromised errors (errors caused by Crypto-Binding failed
or missing) are handled using Result TLVs and Error TLVs.
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3.6.1. 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 an 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
an 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 an 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. An 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 peer detects an error at any point in the TLS layer, the
TEAP peer should send an TEAP response encapsulating a TLS record
containing the appropriate TLS alert message. The server may restart
the conversation by sending an TEAP request packet encapsulating the
TLS HelloRequest handshake message. The peer may allow the TEAP
conversation to be restarted or it may terminate the conversation by
sending an TEAP response with an zero-length message.
3.6.2. 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.
If a server receives a Result TLV of failure with a fatal Error TLV,
it SHOULD 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 SHOULD send a clear text EAP-Failure.
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3.7. Fragmentation
A single TLS record may be up to 16384 octets in length, but a TLS
message may span multiple TLS records, and a TLS certificate message
may in principle be as long as 16 MB. This is larger than the
maximum size for a message on most media types, therefore it is
desirable to support fragmentation. Note that in order to protect
against reassembly lockup and denial-of-service attacks, it may be
desirable for an implementation to set a maximum size for one such
group of TLS messages. Since a typical certificate chain is rarely
longer than a few thousand octets, and no other field is likely to be
anywhere near as long, a reasonable choice of maximum acceptable
message length might be 64 KB. This is still a fairly large message
packet size so an TEAP implementation MUST provide its own support
for fragmentation and reassembly.
Since EAP is a lock-step protocol, fragmentation support can be added
in a simple manner. In EAP, fragments that are lost or damaged in
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. 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 an 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 must respond with an EAP-Request with EAP-Type of TEAP
and no data. This serves as a fragment ACK. The EAP peer MUST wait
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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. PAC Provisioning Within Tunnel
To request provisioning of a PAC, a peer sends a PAC TLV as defined
in Section 4.2.8 containing a PAC Attribute as defined in
Section 4.2.8.1 of PAC Type set to the appropriate value. The
request MAY be issued after the peer has determined that it has
successfully authenticated the EAP server and validated the Crypto-
Binding TLV as defined in Section 4.2.9 to ensure that the TLS
tunnel's integrity is intact. 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. 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
conatining PAC-Acknowledge attribute MUST NOT be used by the peer to
acknowledge the receipt of other types of PACs.
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 | TLS Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer TLVs...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Code
The code field is one octet in length defined as follows:
1 Request
2 Response
Identifier
The Identifier field is one octet and aids in matching
responses with requests. The Identifier field MUST be changed
on each Request packet. The Identifier field in the Response
packet MUST match the Identifier field from the corresponding
request.
Length
The Length field is two octets and indicates the length of the
EAP packet including the Code, Identifier, Length, Type, Flags,
Ver, Message Length, TLS Data, and Outer TLVs fields. Octets
outside the range of the Length field should be treated as Data
Link Layer padding and should be ignored on reception.
Type
TBD for TEAP
Flags
0 1 2 3 4
+-+-+-+-+-+
|L M S R R|
+-+-+-+-+-+
L Length included; set to indicate the presence of the four
octet Message Length field
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M More fragments; set on all but the last fragment
S TEAP start; set in an TEAP Start message
R Reserved (must be zero)
Ver
This field contains the version of the protocol. This document
describes version 1 (001 in binary) of TEAP.
Message Length
The Message Length field is four octets, and is present only if
the L bit is set. This field provides the total length of the
message that may be fragmented over the data fields of multiple
packets.
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-TLV can be derived from
the EAP Length field and Message 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
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whether support of the TLV is required. If the peer or server does
not support a TLV marked mandatory, then it MUST send a NAK TLV in
the response, and all the other TLVs in the message MUST be ignored.
If an EAP peer or server finds an unsupported TLV that is marked as
optional, it can ignore the unsupported TLV. It MUST NOT send an NAK
TLV for a TLV that is not marked mandatory. If all TLVs in a message
are marked optional and none are understood by the peer, then an
EMPTY TEAP Phase 2 message must still 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:
Result TLV
NAK TLV
Error TLV
EAP-Payload TLV
Intermediate-Result TLV
Crypto-Binding TLV
Authority-ID TLV
Request-Action TLV
4.2.1. General TLV Format
TLVs are defined as described below. The fields are transmitted from
left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 4.2.10)
2 Identity-Type TLV (Section 4.2.16)
3 Result TLV (Section 4.2.2)
4 NAK TLV (Section 4.2.3)
5 Error TLV (Section 4.2.4)
6 Channel-Binding TLV (Section 4.2.15)
7 Vendor-Specific TLV (Section 4.2.5)
8 Unassigned
9 EAP-Payload TLV (Section 4.2.6)
10 Intermediate-Result TLV (Section 4.2.7)
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11 PAC TLV (Section 4.2.8)
12 Crypto-Binding TLV (Section 4.2.9)
13 Basic-Password-Auth-Req TLV (Section 4.2.17)
14 Basic-Password-Auth-Resp TLV (Section 4.2.18)
15 PKCS#10 TLV (Section 4.2.14)
16 Unassigned
17 Unassigned
18 Server-Trusted-Root TLV (Section 4.2.12)
19 Request-Action TLV (Section 4.2.11)
20 PKCS#7 TLV (Section 4.2.13)
Length
The length of the Value field in octets.
Value
The value of the TLV.
4.2.2. 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 3.6.2. A Result TLV indicating failure MUST NOT be
accompanied by the following TLVs: NAK, EAP-Payload TLV, or Crypto-
Binding TLV. The Result TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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
4.2.3. NAK TLV
The NAK TLV allows a peer to detect TLVs that are not supported by
the other peer. An TEAP packet can contain 0 or more NAK TLVs. A
NAK TLV should not be accompanied by other TLVs. A NAK TLV MUST NOT
be sent in response to a message containing a Result TLV, instead a
Result TLV of failure should be sent indicating failure and an Error
TLV of Unexpected_TLVs_Exchanged. The NAK TLV is defined as follows:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
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.
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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.
4.2.4. Error TLV
The Error TLV allows an EAP peer or server to indicate errors to the
other party. An 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 must be terminated as described in
Section 3.6.2. The Error TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error-Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
5 for Error TLV
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Length
4
Error-Code
The Error-Code field is four octets. Currently defined values
for Error-Code include:
2001 Tunnel_Compromise_Error
2002 Unexpected_TLVs_Exchanged
4.2.5. 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.
Vendor TLVs may be optional or mandatory. Vendor TLVs sent with
Result TLVs MUST be marked as optional.
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
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R
Reserved, set to zero (0)
TLV Type
7 for Vendor Specific TLV
Length
4 + cumulative length of all included Vendor TLVs
Vendor-Id
The Vendor-Id field is four octets, and contains the Vendor-Id
of the TLV. The high-order octet is 0 and the low-order 3
octets are the SMI Network Management Private Enterprise Code
of the Vendor in network byte order.
Vendor TLVs
This field is of indefinite length. It contains vendor-
specific TLVs, in a format defined by the vendor.
4.2.6. 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 (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.
4.2.7. 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 (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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4.2.8. PAC TLV Format
The PAC TLV provides support for provisioning the Protected Access
Credential (PAC) defined within [RFC4851]. The PAC TLV carries the
PAC and related information within PAC attribute fields.
Additionally, the PAC TLV MAY be used by the peer to request
provisioning of a PAC of the type specified in the PAC Type PAC
attribute. The PAC TLV MUST only be used in a protected tunnel
providing encryption and integrity protection. A general PAC TLV
format is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PAC Attributes...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
0 - Non-mandatory TLV
1 - Mandatory TLV
R
Reserved, set to zero (0)
TLV Type
11 - PAC TLV
Length
Two octets containing the length of the PAC attributes
field in octets.
PAC Attributes
A list of PAC attributes in the TLV format.
4.2.8.1. 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...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
Two octets containing the length of the Value field in octets.
The value of the PAC attribute.
4.2.8.2. PAC-Key
The PAC-Key is a secret key distributed in a PAC attribute of type
PAC-Key. The PAC-Key attribute is included within the PAC TLV
whenever the server wishes to issue or renew a PAC that is bound to a
key such as a Tunnel PAC. The key is a randomly generated octet
string, which is 48 octets in length. The generator of this key is
the issuer of the credential, which is identified by the Authority
Identifier (A-ID).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Key ~
| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
1 - PAC-Key
Length
2-octet length indicating the length of the key
Key
The value of the PAC-Key.
4.2.8.3. 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:
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 ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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.
4.2.8.4. PAC-Info
The PAC-Info is comprised of a set of PAC attributes as defined in
Section 4.2.8.1. 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
Length
2-octet Length field containing the length of the attributes
field in octets.
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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 EAP exchange or from the client-side authentication
during tunnel establishment if inner EAP method
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 EAP method in TEAP phase 2. If the server
is enforcing the I-ID validation on the inner EAP method,
then the I-ID MUST be included in the PAC-Info, to enable
the peer to also enforce a unique PAC for each unique user.
If the I-ID is missing from the PAC-Info, it is assumed that
the Tunnel PAC can be used for multiple users and the peer
will not enforce the unique-Tunnel-PAC-per-user policy.
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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).
4.2.8.5. PAC-Acknowledgement TLV
The PAC-Acknowledgement is used to acknowledge the receipt of the
Tunnel PAC by the peer. The peer includes the PAC-Acknowledgement
TLV in a PAC-TLV sent to the server to indicate the result of the
processing and storing of a newly provisioned Tunnel PAC. This TLV
is only used when Tunnel PAC is provisioned.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
8 - PAC-Acknowledgement
Length
The length of this field is two octets containing a value of 2.
Result
The resulting value MUST be one of the following:
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1 - Success
2 - Failure
4.2.8.6. 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
4.2.9. 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 version
negotiated before TLS tunnel establishment, see Section 3.1.
The Crypto-Binding TLV MUST be included with the Intermediate-Result
TLV to perform Cryptographic Binding after each successful EAP method
in a sequence of EAP methods. The Crypto-Binding TLV can be issued
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at other times as well.
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 3.6.2
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.| Sub-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Nonce ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Compound MAC ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to (1)
R
Reserved, set to zero (0)
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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 EAP method is using. For an
implementation compliant with this version of TEAP, the version
number MUST be set to 1.
Received Version
The Received Version field is a single octet and MUST be set to
the EAP 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.
Sub-Type
The Sub-Type field is one octet. Defined values include
0 Binding Request
1 Binding Response
Nonce
The Nonce field is 32 octets. It contains a 256-bit nonce that
is temporally unique, used for compound MAC key derivation at
each end. The nonce in a request MUST have its least
significant bit set to 0 and the nonce in a response MUST have
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the same value as the request nonce except the least
significant bit MUST be set to 1.
Compound MAC
The 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.
4.2.10. Authority-ID TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to (0)
R
Reserved, set to zero (0)
Type
The Type field is two octets. It is set to 16 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 credetials avaiable for the server. It should be unique
across the deployment.
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4.2.11. Request-Action TLV
The Request-Action TLV MAY be sent by the peer along with a Result
TLV in response to a server's successful Result TLV. It allows the
peer to request the EAP server to negotiate additional EAP methods or
process TLVs specified in the response packet. The server MAY ignore
this TLV.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory set to one (1)
R
Reserved, set to zero (0)
TLV Type
19 for Request-Action TLV
Length
2
Action
The Action field is two octets. Values include:
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1 Process-TLV
2 Negotiate-EAP
4.2.12. 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:
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...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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M
0 - Non-mandatory TLV
R
Reserved, set to zero (0)
TLV Type
18 - Trusted-Server-Root TLV [RFC4851]
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.
4.2.13. PKCS#7 TLV
The PKCS#7 TLV is sent by the EAP server to the peer inside the
Server-Trusted-Root TLV. It contains PKCS#7-wrapped [RFC2315] X.509
certificates. The format consists of a certificate or certificate
chain in a Certificates-Only PKCS#7 SignedData message as defined in
[RFC2311].
The PKCS#7 TLV is always marked as optional, which cannot be
responded to with a NAK TLV. TEAP server implementations that claim
to support the dynamic provisioning defined in this document SHOULD
support this TLV. TEAP peer implementations MAY support this TLV.
If the PKCS#7 TLV contains a certificate or certificate chain that is
not acceptable to the peer, then the peer MUST ignore the TLV.
The PKCS#7 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PKCS #7 Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
M
0 - Optional TLV
R
Reserved, set to zero (0)
TLV Type
20 - PKCS#7 TLV [RFC4851]
Length
The length of the PKCS #7 Data field.
PKCS #7 Data
This field contains the X.509 certificate or certificate chain
in a Certificates-Only PKCS#7 SignedData message.
4.2.14. PKCS#10 TLV
The PKCS#10 TLV is used by the peer to initiate the "simple PKI"
Request/Response from [RFC5272]. The format of the request is as
specified in Section 6.4 of [RFC4945].
The PKCS#10 TLV is always marked as optional, which cannot be
responded to with a NAK TLV.
The PKCS#10 TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PKCS #10 Data...
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
M
0 - Optional TLV
R
Reserved, set to zero (0)
TLV Type
[tbd]
Length
The length of the PKCS #7 Data field.
PKCS #10 Data
This field contains the PKCS#10 certificate request.
4.2.15. Channel-Binding TLV
The Channel-Binding TLV allows an EAP-peer to send channel binding
data to the EAP-server as described in [I-D.ietf-emu-chbind]. 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)
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R
Reserved, set to zero (0)
TLV Type
6 for Channel-Binding TLV
Length
variable
Data
The data field contains channel binding data defined in
[I-D.ietf-emu-chbind].
4.2.16. 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. 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, then the peer SHOULD respond with a NAK TLV. The Identity-Type
TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identity-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
0 (Optional)
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R
Reserved, set to zero (0)
TLV Type
17 for Identity-Type TLV
Length
2
Identity-Type
The Identity-Type field is two octets. Values include:
1 User
2 Machine
4.2.17. Basic-Password-Auth-Req TLV
The Basic-Password-Auth-Req TLV is used by the authentication server
to request a username and password from the peer. It contains an
optional user prompt message for the request. The peer is expected
to obtain the username and password and send them in a Basic-
Password-Auth-Resp TLV.
The Basic-Password-Auth-Req TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prompt ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 format
4.2.18. Basic-Password-Auth-Resp TLV
The Basic-Password-Auth-Resp TLV is used by the peer to respond to a
Basic-Password-Auth-Req TLV with a username and password. The TLV
contains a username and password. The username and password are in
UTF-8 format and prepared as defined in SASLprep [RFC4013].
The Basic-Password-Auth-Resp TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Userlen | Username
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Username ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Passlen | Password
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Password ...
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 format
Passlen
Length of Password field in octets
Password
Password in UTF-8 format
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4.3. Table of TLVs
The following table provides a guide to which TLVs may be found in
which kinds of messages, and in what quantity. The messages are as
follows: Request is an TEAP Request, Response is an TEAP Response,
Success is a message containing a successful Result TLV, and Failure
is a message containing a failed Result TLV.
Request Response Success Failure TLVs
0-1 0-1 0-1 0-1 Intermediate-Result
0-1 0-1 0 0 EAP-Payload
0-1 0-1 1 1 Result
0-1 0-1 0-1 0-1 Crypto-Binding
0+ 0+ 0+ 0+ Error
0+ 0+ 0 0 NAK
0+ 0+ 0+ 0+ Vendor-Specific [NOTE1]
0-1 0-1 0 0 Authority-ID
0 0-1 0-1 0-1 Request-Action
0 0-1 0 0 Channel-Binding
0-1 0-1 0 0 Identity-Type
0-1 0 0 0 Basic-Password-Auth-Req
0 0-1 0 0 Basic-Password-Auth-Resp
[NOTE1] Vendor TLVs (included in Vendor-Specific TLVs) sent with a
Result TLV MUST be marked as optional.
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.
5. Cryptographic Calculations
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
RFC 5077 [RFC5077].
TEAPv1 makes use of the TLS Keying Material Exporters defined in RFC
5705 [RFC5705] to derive the session_key_seed. The Label used in the
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derivation is "EXPORTER-TEAP-SKS". The length of the session key
seed material is 40 octets. No context data is used in the export
process.
The session_key_seed is used by the TEAP Authentication Phase 2
conversation to both cryptographically bind the inner method(s) to
the tunnel as well as generate the resulting TEAP session keys. The
other quantities are used as they are defined in [RFC5246].
5.2. Intermediate Compound Key Derivations
The session_key_seed derived as part of TEAP Phase 2 is used in TEAP
Phase 2 to generate an Intermediate Compound Key (IMCK) used to
verify the integrity of the TLS tunnel after each successful inner
authentication and in the generation of Master Session Key (MSK) and
Extended Master Session Key (EMSK) defined in [RFC3748]. Note that
the IMCK must be recalculated after each successful inner EAP method.
The first step in these calculations is the generation of the base
compound key, IMCK[n] from the session_key_seed and any session keys
derived from the successful execution of n inner EAP methods. The
inner EAP method(s) may provide Master Session Keys, MSK1..MSKn,
corresponding to inner methods 1 through n. 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. If the ith inner
method does not generate an MSK, then MSKi 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",
MSK[j], 60)
S-IMCK[j] = first 40 octets of IMCK[j]
CMK[j] = last 20 octets of IMCK[j]
where TLS-PRF is the PRF negotiated as part of TLS handshake
[RFC5246].
5.3. Computing the Compound MAC
For authentication methods that generate keying material, further
protection against man-in-the-middle attacks is provided through
cryptographically binding keying material established by both TEAP
Phase 1 and TEAP Phase 2 conversations. After each successful inner
EAP authentication, EAP MSKs are cryptographically combined with key
material from TEAP Phase 1 to generate a compound session key, CMK.
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The CMK is used to calculate the Compound MAC as part of the Crypto-
Binding TLV described in Section 4.2.9, 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 = HMAC-HASH( CMK, BUFFER )
where j is the number of the last successfully executed inner EAP
method, HASH is the default hash function or the alternative hash
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 the MAC field zeroed
out.
2 The EAP Type sent by the other party in the first TEAP message.
3 All the Outer-TLVs from the first TEAP message sent by EAP server
to peer. If a single TEAP message is fragmented into multiple
TEAP packets; then the Outer-TLVs in all the fragments of that
message MUST be included.
4 All the Outer-TLVs from the first TEAP message sent by the peer to
the EAP server. If a single TEAP message is fragmented into
multiple TEAP packets, then the Outer-TLVs in all the fragments of
that message MUST be included.
5.4. EAP Master Session Key Generation
TEAP Authentication assures the master session key (MSK) and Extended
Master Session Key (EMSK) output from the EAP method are the result
of all authentication conversations by generating an Intermediate
Compound Key (IMCK). The IMCK is mutually derived by the peer and
the server as described in Section 5.2 by combining the MSKs from
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.
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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, [RFC2434].
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 [RFC2434].
Section 4.2 defines the TLV types that initially populate the
registry. A summary of the TEAP TLV types is given below:
0 Unassigned
1 Authority-ID TLV
2 Identity-Type TLV
3 Result TLV
4 NAK TLV
5 Error TLV
6 Channel-Binding TLV
7 Vendor-Specific TLV
8 Unassigned
9 EAP-Payload TLV
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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#10 TLV
16 Unassigned
17 Unassigned
18 Trusted-Server-Root TLV
19 Request-Action TLV
20 PKCS#7 TLV
The Error-TLV defined in Section 4.2.4 requires an error-code. TEAP
Error-TLV error-codes are assigned based on Specification Required as
defined in [RFC2434]. The initial list of error codes is as follows:
2001 Tunnel_Compromise_Error
2002 Unexpected_TLVs_Exchanged
The Request-Action TLV defined in section Section 4.2.11 contains an
action code which is assigned on a Specification Required basis as
defined in [RFC2434]. The initial actions defined are:
1 Process-TLV
2 Negotiate-EAP
The various values under Vendor-Specific TLV are assigned by Private
Use and do not need to be assigned by IANA.
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
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attacker would have to gain physical access to the wired medium;
wireless media enables anyone to capture information as it is
transmitted over the air, enabling passive attacks. Thus, physical
security can not be assumed and security vulnerabilities are far
greater. The threat model used for the security evaluation of TEAP
is defined in the EAP [RFC3748].
7.1. Mutual Authentication and Integrity Protection
TEAP as a whole, provides message and integrity protection by
establishing a secure tunnel for protecting the authentication
method(s). The confidentiality and integrity protection is defined
by TLS and provides the same security strengths afforded by TLS
employing a strong entropy shared master secret. The integrity of
the key generating authentication methods executed within the TEAP
tunnel is verified through the calculation of the Crypto-Binding TLV.
This ensures that the tunnel endpoints are the same as the inner
method endpoints.
The Result TLV is protected and conveys the true Success or Failure
of TEAP, and should be used as the indicator of its success or
failure respectively. However, as EAP must terminate with 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
There may be cases where a trust relationship exists between the
Phase 1 and Phase 2 servers, such as on a campus or between two
offices within the same company, where there is no danger in
revealing the inner identity and credentials of the peer to entities
between the two servers. In these cases, using a proxy solution
without end-to-end protection of TEAP MAY be used. The TEAP
encrypting/decrypting gateway SHOULD, at a minimum, provide support
for IPsec or similar protection in order to provide confidentiality
for the portion of the conversation between the gateway and the EAP
server.
7.4. Mitigation of Known Vulnerabilities and Protocol Deficiencies
TEAP addresses the known deficiencies and weaknesses in the EAP
method. By employing a shared secret between the peer and server to
establish a secured tunnel, TEAP enables:
o Per packet confidentiality and integrity protection
o User identity protection
o Better support for notification messages
o Protected EAP inner method negotiation
o Sequencing of EAP methods
o Strong mutually derived master session keys
o Acknowledged success/failure indication
o Faster re-authentications through session resumption
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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.
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
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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 client 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 client
permits renegotiation by sending a client_hello, then the server will
respond with server_hello, a certificate and certificate_request
messages. The client 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
exchange and in the generation of the key material exported by
the EAP method described in Section 5.
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7.4.4. PAC Binding to User Identity
A PAC may be bound to a user identity. A compliant implementation of
TEAP MUST validate that an identity obtained in the PAC-Opaque field
matches at minimum one of the identities provided in the TEAP Phase 2
authentication method. This validation provides another binding to
ensure that the intended peer (based on identity) has successfully
completed the TEAP Phase 1 and proved identity in the Phase 2
conversations.
7.5. Protecting against Forged Clear Text EAP Packets
EAP Success and EAP Failure packets are, in general, sent in clear
text and may be forged by an attacker without detection. Forged EAP
Failure packets can be used to attempt to convince an EAP peer to
disconnect. Forged EAP Success packets may be used to attempt to
convince a peer that authentication has succeeded, even though the
authenticator has not authenticated itself to the peer.
By providing message confidentiality and integrity, TEAP provides
protection against these attacks. Once the peer and AS initiate the
TEAP Authentication Phase 2, compliant TEAP implementations must
silently discard all clear text EAP messages, unless both the TEAP
peer and server have indicated success or failure using a protected
mechanism. Protected mechanisms include TLS alert mechanism and the
protected termination mechanism described in Section 3.3.3.
The success/failure decisions within the TEAP tunnel indicate the
final decision of the TEAP authentication conversation. After a
success/failure result has been indicated by a protected mechanism,
the TEAP peer can process unprotected EAP Success and EAP Failure
messages; however the peer MUST ignore any unprotected EAP success or
failure messages where the result does not match the result of the
protected mechanism.
To abide by [RFC3748], the server must send 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 an TEAP protected EAP Success or EAP
Failure packet should not be a final packet in an 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 MUST verify the validity of the EAP server
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certificate, and SHOULD also examine the EAP server name presented in
the certificate, in order to determine whether the EAP server can be
trusted. Please note that in the case where the EAP authentication
is remoted, the EAP server will not reside on the same machine as the
authenticator, and therefore the name in the EAP server's certificate
cannot be expected to match that of the intended destination. In
this case, a more appropriate test might be whether the EAP server's
certificate is signed by a CA controlling the intended domain and
whether the authenticator can be authorized by a server in that
domain.
7.7. Tunnel PAC Considerations
Since the Tunnel PAC is stored by the peer, special care should be
given to the overall security of the peer. The Tunnel PAC must be
securely stored by the peer to prevent theft or forgery of any of the
Tunnel PAC components. In particular, the peer must securely store
the PAC-Key and protect it from disclosure or modification.
Disclosure of the PAC-Key enables an attacker to establish the TEAP
tunnel; however, disclosure of the PAC-Key does not reveal the peer
or server identity or compromise any other peer's PAC credentials.
Modification of the PAC-Key or PAC-Opaque components of the Tunnel
PAC may also lead to denial of service as the tunnel establishment
will fail. The PAC-Opaque component is the effective TLS ticket
extension used to establish the tunnel using the techniques of
[RFC5077]. Thus, the security considerations defined by [RFC5077]
also apply to the PAC- Opaque. The PAC-Info may contain information
about the Tunnel PAC such as the identity of the PAC issuer and the
Tunnel PAC lifetime for use in the management of the Tunnel PAC. The
PAC-Info should be securely stored by the peer to protect it from
disclosure and modification.
7.8. Security Claims
This section provides the needed security claim requirement for EAP
[RFC3748].
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.
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Replay protection: Yes
Confidentiality: Yes
Key derivation: Yes
Key strength: See Note 1 below.
Dictionary attack prot.: Yes
Fast reconnect: Yes
Cryptographic binding: Yes
Session independence: Yes
Fragmentation: Yes
Key Hierarchy: Yes
Channel binding: Yes
Notes
1. BCP 86 [RFC3766] offers advice on appropriate key sizes. The
National Institute for Standards and Technology (NIST) also
offers advice on appropriate key sizes in [NIST-SP-800-57].
[RFC3766] Section 5 advises use of the following required RSA or
DH module and DSA subgroup size in bits, for a given level of
attack resistance in bits. Based on the table below, a 2048-bit
RSA key is required to provide 128-bit equivalent key strength:
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
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8. Acknowledgements
The TEAP v1 design and protocol specification is based on the ideas
and hard efforts of 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 and Simon Josefsson. Helpful review comments were provided by
Russ Housley, Jari Arkko, Ilan Frenkel and Jeremy Steiglitz.
9. References
9.1. Normative References
[I-D.ietf-emu-chbind] Hartman, S., Clancy, C., and K. Hoeper,
"Channel Binding Support for EAP
Methods", draft-ietf-emu-chbind-06
(work in progress), October 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs
to Indicate Requirement Levels",
BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand,
"Guidelines for Writing an IANA
Considerations Section in RFCs",
BCP 26, RFC 2434, October 1998.
[RFC3268] Chown, P., "Advanced Encryption
Standard (AES) Ciphersuites for
Transport Layer Security (TLS)",
RFC 3268, June 2002.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J.,
Carlson, J., and H. Levkowetz,
"Extensible Authentication Protocol
(EAP)", RFC 3748, June 2004.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep
Profile for User Names and Passwords",
RFC 4013, February 2005.
[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.
Zhou, et al. Expires April 22, 2012 [Page 65]
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[RFC5077] Salowey, J., Zhou, H., Eronen, P., and
H. Tschofenig, "Transport Layer
Security (TLS) Session Resumption
without Server-Side State", RFC 5077,
January 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The
Transport Layer Security (TLS) Protocol
Version 1.2", RFC 5246, August 2008.
[RFC5422] Cam-Winget, N., McGrew, D., Salowey,
J., and H. Zhou, "Dynamic Provisioning
Using Flexible Authentication via
Secure Tunneling Extensible
Authentication Protocol (EAP-FAST)",
RFC 5422, March 2009.
[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.
9.2. Informative References
[I-D.ietf-emu-eaptunnel-req] Hoeper, K., Hanna, S., Zhou, H., and J.
Salowey, "Requirements for a Tunnel
Based EAP Method",
draft-ietf-emu-eaptunnel-req-09 (work
in progress), December 2010.
[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.
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[RFC2311] Dusse, S., Hoffman, P., Ramsdell, B.,
Lundblade, L., and L. Repka, "S/MIME
Version 2 Message Specification",
RFC 2311, March 1998.
[RFC2315] Kaliski, B., "PKCS #7: Cryptographic
Message Syntax Version 1.5", RFC 2315,
March 1998.
[RFC2560] Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509
Internet Public Key Infrastructure
Online Certificate Status Protocol -
OCSP", RFC 2560, June 1999.
[RFC3280] Housley, R., Polk, W., Ford, W., and D.
Solo, "Internet X.509 Public Key
Infrastructure Certificate and
Certificate Revocation List (CRL)
Profile", RFC 3280, April 2002.
[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
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Identifier", RFC 4282, December 2005.
[RFC4630] Housley, R. and S. Santesson, "Update
to DirectoryString Processing in the
Internet X.509 Public Key
Infrastructure Certificate and
Certificate Revocation List (CRL)
Profile", RFC 4630, August 2006.
[RFC4945] Korver, B., "The Internet IP Security
PKI Profile of IKEv1/ISAKMP, IKEv2, and
PKIX", RFC 4945, August 2007.
[RFC5216] Simon, D., Aboba, B., and R. Hurst,
"The EAP-TLS Authentication Protocol",
RFC 5216, March 2008.
[RFC5272] Schaad, J. and M. Myers, "Certificate
Management over CMS (CMC)", RFC 5272,
June 2008.
[RFC5281] Funk, P. and S. Blake-Wilson,
"Extensible Authentication Protocol
Tunneled Transport Layer Security
Authenticated Protocol Version 0 (EAP-
TTLSv0)", RFC 5281, August 2008.
[RFC5421] Cam-Winget, N. and H. Zhou, "Basic
Password Exchange within the Flexible
Authentication via Secure Tunneling
Extensible Authentication Protocol
(EAP-FAST)", RFC 5421, March 2009.
[RFC6066] Eastlake, D., "Transport Layer Security
(TLS) Extensions: Extension
Definitions", RFC 6066, January 2011.
Appendix A. Evaluation Against Tunnel Based EAP Method Requirements
This section evaluates all tunnel based EAP method requirements
described in [I-D.ietf-emu-eaptunnel-req] 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.
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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.
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.
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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 4.2.9.
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.
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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 4.2.5.
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 4.2.2.
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 4.2.17 and Basic-
Password-Auth-Resp TLV as defined in Section 4.2.18.
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 4.2.15.
A.19. Requirement 4.5.1.1 Confidentiality and Integrity
TEAP v1 meets this requirement by running the password authentication
inside a protected TLS tunnel.
A.20. Requirement 4.5.1.2 Authentication of Server
TEAP v1 meets this requirement by mandating authentication of the
server before establishment of the protected TLS and then running
inner password authentication as defined in Section 3.2.
A.21. Requirement 4.5.1.3 Server Certificate Revocation Checking
TEAP v1 meets this requirement by supporting TLS Certificate Status
Request extension [RFC6066] during tunnel establishment.
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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 4.2.17 and Basic-
Password-Auth-Resp TLV as defined in Section 4.2.18.
A.23. Requirement 4.5.3 Meta-data
TEAP v1 meets this requirement by supporting Identity-Type TLV as
defined in Section 4.2.16 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 4.2.9.
A.28. Requirement 4.6.4 Peer Initiated
TEAP v1 meets this requirement by supporting Request-Action TLV as
defined in Section 4.2.11 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 4.2.16 to indicate whether the authentication is
for a user or a machine.
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Appendix B. Major Differences from EAP-FAST
This document is a new standard tunnel EAP method based on revision
of 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 addtion 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
C.1. Successful Authentication
The following exchanges show a successful TEAP authentication with
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)
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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)
<- EAP Payload TLV, EAP-Request,
EAP-GTC, Challenge
EAP Payload TLV, EAP-Response,
EAP-GTC, Response with both
user name and password) ->
optional additional exchanges (new pin mode,
password change etc.) ...
<- Intermediate-Result TLV (Success)
Crypto-Binding TLV (Request)
Intermediate-Result TLV (Success)
Crypto-Binding TLV(Response) ->
<- Result TLV (Success)
(Optional PAC TLV)
Result TLV (Success)
(PAC TLV Acknowledgment) ->
TLS channel torn down
(messages sent in clear text)
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<- 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:
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)
<- EAP Payload TLV, EAP-Request,
EAP-GTC, Challenge
EAP Payload TLV, EAP-Response,
EAP-GTC, Response with both
user name and password) ->
<- EAP Payload TLV, EAP-Request,
EAP-GTC, error message
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EAP Payload TLV, EAP-Response,
EAP-GTC, empty data packet to
acknowledge unrecoverable error) ->
<- Result TLV (Failure)
Result TLV (Failure) ->
TLS channel torn down
(messages sent in clear text)
<- EAP-Failure
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)
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EAP-Response/
EAP-Type=TEAP, V=1
([TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
EAP-Payload-TLV[EAP-Request/
Identity])
// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload-TLV
[EAP-Response/Identity (MyID2)]->
// identity protected by TLS.
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
// Method X exchanges followed by Protected Termination
<- Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
Result TLV (Success)
Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
Result-TLV (Success) ->
// TLS channel torn down
(messages sent in clear text)
<- EAP-Success
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C.4. Client authentication during Phase 1 with identity privacy
In the case where a certificate based TLS handshake occurs within
TEAP Phase 1, and client certificate authentication and identity
privacy is desired, the conversation will appear as follows:
Authenticating Peer Authenticator
------------------- -------------
<- EAP-Request/Identity
EAP-Response/
Identity (MyID1) ->
// Identity sent in the clear. May be a hint to help route
the authentication request to EAP server, instead of the
full user identity.
<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS server_hello,
TLS certificate,
[TLS server_key_exchange,]
[TLS certificate_request,]
TLS server_hello_done)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_key_exchange,
TLS change_cipher_spec,
TLS finished) ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,TLS Hello-Request)
// TLS channel established
(messages sent within the TLS channel)
// TLS Hello-Request is piggybacked to the TLS Finished as
Handshake Data and protected by the TLS tunnel
TLS client_hello ->
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<- 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,
Result TLV (Success)
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)
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(Fragment 1: L, M bits set)
EAP-Response/
EAP-Type=TEAP, V=1 ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(Fragment 2: M bit set)
EAP-Response/
EAP-Type=TEAP, V=1 ->
<- EAP-Request/
EAP-Type=TEAP, V=1
(Fragment 3)
EAP-Response/
EAP-Type=TEAP, V=1
([TLS certificate,]
TLS client_key_exchange,
[TLS certificate_verify,]
TLS change_cipher_spec,
TLS finished)
(Fragment 1: L, M bits set)->
<- EAP-Request/
EAP-Type=TEAP, V=1
EAP-Response/
EAP-Type=TEAP, V=1
(Fragment 2)->
<- EAP-Request/
EAP-Type=TEAP, V=1
(TLS change_cipher_spec,
TLS finished,
[EAP-Payload-TLV[
EAP-Request/Identity]])
// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload-TLV
[EAP-Response/Identity (MyID2)]->
// identity protected by TLS.
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
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EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
// Method X exchanges followed by Protected Termination
<- Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
Result TLV (Success)
Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
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
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([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] ->
// 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 (Version=1
TEAP Version=1, Nonce,
CompoundMAC),
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
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EAP methods X and the TLS tunnel.
Intermediate Result TLV (Success),
Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
EAP-Payload-TLV [EAP-Type=Y] ->
// Optional additional Y Method exchanges...
<- EAP Payload TLV [
EAP-Type=Y]
EAP Payload TLV
[EAP-Type=Y] ->
<- Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Version=1
TEAP Version=1, Nonce,
CompoundMAC),
Result TLV (Success)
Intermediate-Result-TLV (Success),
Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
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) ->
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<- EAP-Request/
EAP-Type=TEAP, V=1
(TEAP Start, S bit set, Authority-ID)
EAP-Response/
EAP-Type=TEAP, V=1
(TLS client_hello 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)
<- 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) ->
<- Crypto-Binding TLV (Version=1,
TEAP Version=1, Nonce,
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CompoundMAC),
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
------------------- -------------
<- 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,
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TLS finished,
EAP-Payload-TLV[
EAP-Request/Identity])
// TLS channel established
(messages sent within the TLS channel)
// First EAP Payload TLV is piggybacked to the TLS Finished as
Application Data and protected by the TLS tunnel
EAP-Payload-TLV
[EAP-Response/Identity] ->
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X] ->
<- EAP-Payload-TLV
[EAP-Request/EAP-Type=X]
EAP-Payload-TLV
[EAP-Response/EAP-Type=X]->
<- Intermediate Result TLV (Success),
Crypto-Binding TLV (Version=1
TEAP Version=1, Nonce,
CompoundMAC),
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 (Version=1,
TEAP Version=1, Nonce,
CompoundMAC),
Vendor-Specific TLV ->
// Optional additional Vendor-Specific TLV exchanges...
<- Vendor-Specific TLV
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Vendor Specific TLV ->
<- 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 -00
1. Changed protocol name to TEAP: Tunnel EAP Method
2. Changed version of protocol to version 1
3. Revised introduction
4. Moved differences section to appendix
5. Revised design goals section
6. Revised PAC definition
7. Revised protocol description to be in line with RFC 5077 PAC
distribution
8. Revised EAP Sequences Section
9. Added section on PAC provisioning within tunnel
10. Added outer TLVs to the message format
11. Renumbered TLVs
12. Included PAC TLVs
13. Added Authority ID TLV
14. Added PKCS#7 and server trust root TLV definitions
15. Added PKCS#10 TLV
16. Added EAP-Type and outer TLVs to crypto binding compound MAC
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Authors' Addresses
Hao Zhou
Cisco Systems
4125 Highlander Parkway
Richfield, OH 44286
US
EMail: hzhou@cisco.com
Nancy Cam-Winget
Cisco Systems
3625 Cisco Way
San Jose, CA 95134
US
EMail: ncamwing@cisco.com
Joseph Salowey
Cisco Systems
2901 3rd Ave
Seattle, WA 98121
US
EMail: jsalowey@cisco.com
Stephen Hanna
Juniper Networks
79 Parsons Street
Brighton, MA 02135
US
EMail: shanna@juniper.net
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