Network Working Group N. Cam-Winget
Internet-Draft H. Zhou
Intended status: Standards Track Cisco Systems
Expires: July 9, 2010 January 5, 2010
EAP Type-Length-Value Container
draft-cam-winget-eap-tlv-00
Abstract
The Extensible Authentication Protocol (EAP), defined in RFC 3748,
facilitates multiple authentication methods that are widely deployed
today. As tunnel mechanisms become more prevalent, there has been
interest in carrying other types of data between the EAP Peer and the
EAP server. Existing tunnel EAP methods have already defined generic
data structures to carry such information.
This document defines a generic TLV "container" that can be used
within an EAP method.
Status of this Memo
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Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specification Requirements . . . . . . . . . . . . . . . . . . 3
3. EAP Type-Length-Value Format and Support . . . . . . . . . . . 3
4. EAP TLV Format . . . . . . . . . . . . . . . . . . . . . . . . 4
5. NAK TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Error TLV . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Vendor-Specific TLV . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
Different authentication systems use the Extensible Authentication
Protocol (EAP) framework to define tunnel authentication methods for
establishing strong mutual authentication through the use of
different authentication schemes including smart cards, One Time
Passwords, cleartext passwords and others. Tunnel EAP methods whose
requirements are defined in [I-D.salowey-emu-eaptunnel-req] carry EAP
methods and other authorization information such as channel binding
that need an inner tunnel transport mechanism. Other IETF groups
have also expressed the need to carry other types of data between the
EAP Peer and EAP Server.
Tunnel EAP methods such as EAP-FAST [RFC4851] and EAP-TTLS [RFC5281]
already use TLV structures to carry data. EAP-TTLS overloads the
Diameter AVP attribute type space, while EAP-FAST and other previous
work, such as the one presented in "draft-hiller-eap-tlv" use a
separate attribute type namespace. This memo takes the approach of
using the separate namespace used in EAP-FAST.
2. 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] .
3. EAP Type-Length-Value Format and Support
To allow for interoperability, the EAP Type-Length-Value (EAP-TLV)
defines a container format used to carry arbitrary data between the
EAP peer and the EAP server. It is intended that this container be
used only inside a protected EAP tunnel.
The mandatory bit in an EAP-TLV indicates whether support of the EAP-
TLV is required. If the EAP Peer or Server does not support an EAP-
TLV marked mandatory, then it MUST send a NAK TLV in the response,
and all the other EAP-TLVs in the message MUST be ignored. If an EAP
Peer or Server finds an unsupported TLV which is marked as optional,
it can ignore the unsupported EAP-TLV. It MUST NOT send a NAK TLV
for an EAP-TLV that is not marked mandatory.
Note that an EAP Peer or Server may support an EAP-TLV with the
mandatory bit set, but may not understand the contents. The
appropriate response to a supported EAP-TLV with content that is not
understood is defined by the individual EAP-TLV specification.
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EAP implementations compliant with this specification MUST support
EAP-TLV exchanges, as well as processing of mandatory/optional
settings on the EAP-TLV. Implementations conforming to this
specification MUST support the following subset of EAP-TLVs defined
in this document:
NAK TLV
4. EAP TLV Format
EAP-TLVs are defined as described below. The fields are transmitted
from left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
0 Optional TLV
1 Mandatory TLV
R
Reserved, set to zero (0)
TLV Type
A 14-bit field, denoting the TLV type. Allocated Types
include:
0 Reserved
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1 Reserved
2 Reserved
3 Reserved
4 NAK TLV
5 Error TLV
7 Vendor Specific TLV
Length
The length of the Value field in octets.
Value
The value of the TLV.
5. NAK TLV
The NAK TLV allows an EAP Peer or Server to detect TLVs that are not
supported by the other party. An EAP packet can contain 0 or more
NAK TLVs. The NAK TLV is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAK-Type | TLVs....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to one (1)
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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 EAP-TLV that was not supported. 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.
The Vendor-Id field MUST be zero for EAP-TLVs that are not
Vendor-Specific TLVs.
NAK-Type
The NAK-Type field is two octets. The field contains the Type
of the TLV that was not supported. A TLV of this Type MUST
have been included in the previous packet.
TLVs
This field contains a list of 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.
6. Error TLV
The Error TLV allows an EAP Peer or Server to indicate errors to the
other party. For example, an error may occur if the EAP TLV contains
information that can not be parsed or if the EAP Peer or Server
received an unexpected EAP TLV. An EAP packet can contain 0 or more
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Error TLVs. The appropriate response to an Error TLV is defined by
the individual EAP method or EAP-TLV specification. The Error TLV is
defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error-Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M
Mandatory, set to one (1)
R
Reserved, set to zero (0)
TLV Type
5 for Error TLV
Length
4
Error-Code
The Error-Code field is four octets. Allocated Error Types
include:
0 Reserved
1 EAP-TLV could not be processed
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2 Unexpected EAP-TLV
7. 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. The 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
R
Reserved, set to zero (0)
TLV Type
7 for Vendor Specific TLV
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Length
>=4
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.
8. Security Considerations
The EAP-TLV container can carry arbitrary data between an EAP Peer
and the EAP server. It is expected that the EAP TLVs defined in this
document are carried by an EAP method that provides the required
protection, such as an EAP tunnel method.
9. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of EAP-TLV related values, in
accordance with BCP 26, [RFC2434].
The document defines a registry for EAP-TLV types, which may be
assigned by Specification Required as defined in [RFC2434].
Section 4 defines the TLV types that initially populate the registry.
10. Acknowledgements
The TLVs defined in this draft borrow from the work done in EAP-FAST.
The authors would also like to recognize Tom Hiller, Ashwin Palekar
and Glen Zorn for introducing this concept to the EAP WG back in
2002.
11. References
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11.1. Normative References
[I-D.salowey-emu-eaptunnel-req]
Hoeper, K., Hanna, S., Zhou, H., and J. Salowey,
"Requirements for an Tunnel Based EAP Method",
draft-salowey-emu-eaptunnel-req-01 (work in progress),
June 2008.
[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.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[RFC4851] Cam-Winget, N., McGrew, D., Salowey, J., and H. Zhou, "The
Flexible Authentication via Secure Tunneling Extensible
Authentication Protocol Method (EAP-FAST)", RFC 4851,
May 2007.
11.2. Informative References
[RFC5281] Funk, P. and S. Blake-Wilson, "Extensible Authentication
Protocol Tunneled Transport Layer Security Authenticated
Protocol Version 0 (EAP-TTLSv0)", RFC 5281, August 2008.
Authors' Addresses
Nancy Cam-Winget
Cisco Systems
80 West Tasman Drive
San Jose, CA 95134
US
Email: ncamwing@cisco.com
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Hao Zhou
Cisco Systems
4125 Highlander Parkway
Richfield, OH 44286
US
Email: hzhou@cisco.com
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