PANA Working Group Y. Ohba
Internet-Draft Toshiba
Intended status: Standards Track June 28, 2009
Expires: December 30, 2009
Pre-authentication Support for PANA
draft-ietf-pana-preauth-06
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Abstract
This document defines an extension to the Protocol for carrying
Authentication for Network Access (PANA) for proactively establishing
a PANA security association between a PANA client in one access
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network and a PANA authentication agent in another access network to
which the PANA client may move.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Specification of Requirements . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Pre-authentication Procedure . . . . . . . . . . . . . . . . . 4
4. PANA Extensions . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
The Protocol for carrying Authentication for Network Access (PANA)
[RFC5191] carries EAP messages between a PaC (PANA Client) and a PAA
(PANA Authentication Agent) in the access network. If the PaC is a
mobile device and is capable of moving from one access network to
another while running its applications, it is critical for the PaC to
perform a handover seamlessly without degrading the performance of
the applications during the handover period. When the handover
requires the PaC to establish a PANA session with the PAA in the new
access network, the signaling to establish the PANA session should be
completed as fast as possible. See [I-D.ietf-hokey-preauth-ps] for
the handover latency requirements.
This document defines an extension to the PANA protocol [RFC5191]
used for proactively executing EAP authentication and establishing a
PANA SA (Security Association) between a PaC in an access network and
a PAA in another access network to which the PaC may move. The
extension to the PANA protocol is designed to realize direct pre-
authentication defined in [I-D.ietf-hokey-preauth-ps]. How to
realize authorization and accounting with the use of the pre-
authentication extension is out of the scope of this document.
1.1. Specification of Requirements
In this document, several words are used to signify the requirements
of the specification. These words are often capitalized. 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].
2. Terminology
The following terms are used in this document in addition to the
terms defined in [RFC5191].
Serving Network: The access network to which the host is currently
attached.
Candidate Network: An access network that is a potential target of
host's handover.
Serving PAA (SPAA): A PAA that resides in the serving network and
provides network access authentication for a particular PaC.
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Candidate PAA (CPAA): A PAA that resides in a candidate network to
which the PaC may move. A CPAA for a particular PaC may be a SPAA
for another PaC.
Pre-authentication: Pre-authentication refers to EAP pre-
authentication and defined as the utilization of EAP to pre-
establish EAP keying material on an authenticator prior to arrival
of the peer at the access network served by that authenticator
[I-D.ietf-hokey-preauth-ps]. In this draft, EAP pre-
authentication is performed between a PaC and a CPAA.
3. Pre-authentication Procedure
A PaC that supports pre-authentication may establish a PANA session
for each CPAA.
There may be several mechanisms for a PaC and a CPAA to discover each
other. For example, IEEE 802.21 [802.21] Information Service and
Command Service can be used for the PaC to discover the CPAA and the
CPAA to discover the PaC, respectively.
There may be a number of criteria for CPAA selection, the timing to
start pre-authentication and the timing as to when the CPAA becomes
the SPAA. Such criteria can be implementation specific and thus are
outside the scope of this document.
Pre-authentication may be initiated by both a PaC and a CPAA in a
similar way as normal authentication. A new 'E' (prE-authentication)
bit is defined in the PANA header. When pre-authentication is
performed, the 'E' (prE-authentication) bit of PANA messages is set
in order to indicate that this PANA run is for pre-authentication.
Use of pre-authentication is negotiated as follows.
o When a PaC initiates pre-authentication, it sends a PANA-Client-
Initiation (PCI) message with the 'E' (prE-authentication) bit
set. The CPAA responds with a PANA-Auth-Request (PAR) message
with the 'S' (Start) and 'E' (prE-authentication) bits set only if
it supports pre-authentication. Otherwise, the 'E' (prE-
authentication) bit of the PAR message will be cleared according
to Section 6.2 of [RFC5191], which results in a negotiation
failure.
o When a CPAA initiates pre-authentication, it sends a PAR message
with the 'S' (Start) and 'E' (prE-authentication) bits set. The
PaC responds with a PANA-Auth-Answer (PAN) message with the 'S'
(Start) and 'E' (prE-authentication) bits set only if it supports
pre-authentication. Otherwise, the 'E' (prE-authentication) bit
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of the PAN message will be cleared according to Section 6.2 of
[RFC5191], which results in a negotiation failure.
o Once the PaC and CPAA have successfully negotiated on performing
pre-authentication using the 'S' (Start) and 'E' (prE-
authentication) bits, the subsequent PANA messages exchanged
between them MUST have the 'E' (prE-authentication) bit set until
CPAA becomes SPAA of the PaC. The PaC may conduct this exchange
with more than one CPAA. If the PaC and CPAA have failed to
negotiate on performing pre-authentication, the PaC or CPAA that
sent a message with both the 'S' (Start) and 'E' (prE-
authentication) bits set MUST discard the message received from
the peer with 'S' (Start) bit set and the 'E' (prE-authentication)
bit cleared, which will eventually result in PANA session
termination.
When a CPAA of the PaC becomes the SPAA due to, e.g., movement of the
PaC, the PaC informs the PAA of the change using PANA-Notification-
Request (PNR) and PANA-Notification-Answer (PNA) messages with the
'P' (Ping) bit set and the 'E' (prE-authentication) bit cleared. The
'E' (prE-authentication) bit MUST be cleared in subsequent PANA
messages.
The PANA session between the PaC and a CPAA is deleted by entering
the termination phase of the PANA protocol.
Example call flows for PaC-initiated pre-authentication and PAA-
initiated pre-authentication are shown in Figure 1 and Figure 2,
respectively. Note that EAP authentication is performed over PAR and
PAN exchanges.
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PaC CPAA
| |
+------------------+ |
|Pre-authentication| |
|trigger | |
+------------------+ |
| PCI w/'E' bit set |
|------------------------------------------------>|
| PAR w/'S' and 'E' bits set |
|<------------------------------------------------|
| PAN w/'S' and 'E' bits set |
|------------------------------------------------>|
| PAR-PAN exchange w/'E' bit set |
|<----------------------------------------------->|
| PAR w/'C' and 'E' bits set |
|<------------------------------------------------|
| PAN w/'C' and 'E' bits set |
|------------------------------------------------>|
. . .
. . .
+----------+ |
| Movement | |
+----------+ |
| PNR w/ 'P' bit set and w/o 'E' bit set |
|------------------------------------------------>|
| +-----------------+
| |CPAA becomes SPAA|
| +-----------------+
| PNA w/ 'P' bit set and w/o 'E' bit set |
|<------------------------------------------------|
| |
Figure 1: PaC-initiated Pre-authentication Call Flow
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PaC CPAA
| |
| +------------------+
| |Pre-authentication|
| |trigger |
| +------------------+
| PAR w/'S' and 'E' bits set |
|<------------------------------------------------|
| PAN w/'S' and 'E' bits set |
|------------------------------------------------>|
| PAR-PAN exchange w/'E' bit set |
|<----------------------------------------------->|
| PAR w/'C' and 'E' bits set |
|<------------------------------------------------|
| PAN w/'C' and 'E' bits set |
|------------------------------------------------>|
. . .
. . .
+----------+ |
| Movement | |
+----------+ |
| PNR w/ 'P' bit set and w/o 'E' bit set |
|------------------------------------------------>|
| +-----------------+
| |CPAA becomes SPAA|
| +-----------------+
| PNA w/ 'P' bit set and w/o 'E' bit set |
|<------------------------------------------------|
| |
Figure 2: PAA-initiated Pre-authentication Call Flow
4. PANA Extensions
A new 'E' (prE-authentication) bit is defined in Flags field of PANA
header as follows.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R S C A P I E r r r r r r r r r|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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E(PrE-authentication) When pre-authentication is performed, the 'E'
(prE-authentication) bit of PANA messages is set in order to
indicate whether this PANA run is for pre-authentication. The
exact usage of this bit is described in Section 3. This bit is to
be assigned by IANA.
5. Backward Compatibility
Backward compatibility between a PANA entity that does not support
the pre-authentication extension and another PANA entity that
supports the pre-authentication extension is maintained as follows.
When a PaC that supports the pre-authentication extension initiates
PANA pre-authentication by sending a PCI message with the 'E' (prE-
authentication) bit set to a PAA that does not support the pre-
authentication extension, the PAA will ignore the E-bit according to
Section 6.2 of [RFC5191], and try to process the message as a normal
authentication attempt. As a result, the PaC will receive a PAR
message with the 'E' (prE-authentication) bit cleared.
Similarly, when a PAA that supports the pre-authentication extension
initiates PANA pre-authentication by sending a PAR message with the
'E' (prE-authentication) bit set to a PaC that does not support the
pre-authentication extension, the PaC will ignore the E-bit, and try
to process the message as a normal authentication attempt. As a
result, the PAA will receive a PAN message with the 'E' (prE-
authentication) bit cleared.
In both cases, the negotiation on the use of pre-authentication will
fail and eventually the PANA session will be terminated as described
in Section Section 3.
6. Security Considerations
Since the mechanism described in this document is designed to work
across multiple access networks, an access network may be configured
to allow or disallow PANA messages from a set of access networks.
When pre-authentication is initiated by CPAA, it is possible that
multiple CPAAs simultaneously initiate pre-authentication for the
same PaC. In order to avoid possible resource consumption attacks on
the PaC caused by an attacker initiating pre-authentication for the
PaC by changing source addresses, the PaC SHOULD limit the maximum
number of CPAAs allowed to communicate.
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7. IANA Considerations
As described in Section 4, bit 6 of the Flags field of the PANA
Header needs to be assigned by IANA for the 'E' (prE-authentication)
bit.
8. Acknowledgments
The author would like to thank Alper Yegin, Basavaraj Patil, Ashutosh
Dutta, Julien Bournelle, Sasikanth Bharadwaj, Subir Das, Rafa Marin
Lopez, Lionel Morand, Victor Fajardo, Glen Zorn and Qin Wu for their
support and valuable feedback.
9. References
9.1. Normative References
[RFC5191] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
Yegin, "Protocol for Carrying Authentication for Network
Access (PANA)", RFC 5191, May 2008.
9.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-hokey-preauth-ps]
Ohba, Y. and G. Zorn, "Extensible Authentication Protocol
(EAP) Early Authentication Problem Statement",
draft-ietf-hokey-preauth-ps-08 (work in progress),
June 2009.
[802.21] IEEE, "Standard for Local and Metropolitan Area Networks:
Media Independent Handover Services", LAN MAN Standards
Committee of the IEEE Computer Society 802.21 2008.
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Author's Address
Yoshihiro Ohba
Toshiba America Research, Inc.
1 Telcordia Drive
Piscateway, NJ 08854
USA
Phone: +1 732 699 5305
Email: yohba@tari.toshiba.com
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