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rfc:rfc5192

Network Working Group L. Morand Request for Comments: 5192 France Telecom R&D Category: Standards Track A. Yegin

                                                               Samsung
                                                              S. Kumar
                                                     Tech Mahindra Ltd
                                                        S. Madanapalli
                                                               Samsung
                                                              May 2008
     DHCP Options for Protocol for Carrying Authentication for
            Network Access (PANA) Authentication Agents

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 This document defines new DHCPv4 and DHCPv6 options that contain a
 list of IP addresses to locate one or more PANA (Protocol for
 carrying Authentication for Network Access) Authentication Agents
 (PAAs).  This is one of the methods that a PANA Client (PaC) can use
 to locate PAAs.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
 2.  Specification of Requirements . . . . . . . . . . . . . . . . . 2
 3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 2
 4.  PANA Authentication Agent DHCPv4 Option . . . . . . . . . . . . 3
 5.  PANA Authentication Agent DHCPv6 Option . . . . . . . . . . . . 4
 6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
 7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
 8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
 9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
   9.2.  Informative References  . . . . . . . . . . . . . . . . . . 6

Morand, et al. Standards Track [Page 1] RFC 5192 PAA DHCP Options May 2008

1. Introduction

 The Protocol for carrying Authentication for Network Access (PANA)
 [RFC5191] defines a new Extensible Authentication Protocol (EAP)
 [RFC3748] lower layer that uses IP between the protocol end-points.
 The PANA protocol is run between a PANA Client (PaC) and a PANA
 Authentication Agent (PAA) in order to perform authentication and
 authorization for the network access service.
 This document specifies DHCPv4 [RFC2131] and DHCPv6 [RFC3315] options
 that allow PANA clients (PaCs) to discover PANA Authentication Agents
 (PAAs).  This is one of the methods for locating PAAs.
 The DHCP options defined in this document are used only as a PAA
 discovery mechanism.  These DHCP options MUST NOT be used to perform
 any negotiation of the use of PANA between the PaC and a PAA.

2. 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].

3. Terminology

 This document uses the DHCP terminology defined in [RFC2131],
 [RFC2132], and [RFC3315].
 This document uses the PANA terminology defined in [RFC5191].  In
 particular, the following terms are defined:
    PANA Client (PaC):
       The client side of the protocol that resides in the access
       device (e.g., laptop, PDA, etc.).  It is responsible for
       providing the credentials in order to prove its identity
       (authentication) for network access authorization.  The PaC and
       the EAP peer are co-located in the same access device.
    PANA Authentication Agent (PAA):
       The protocol entity in the access network whose responsibility
       it is to verify the credentials provided by a PANA client (PaC)
       and authorize network access to the access device.  The PAA and

Morand, et al. Standards Track [Page 2] RFC 5192 PAA DHCP Options May 2008

       the EAP authenticator (and optionally the EAP server) are
       colocated in the same node.

4. PANA Authentication Agent DHCPv4 Option

 This DHCPv4 option carries a list of 32-bit (binary) IPv4 addresses
 indicating PANA Authentication Agents (PAAs) available to the PANA
 client (PaC).
 The DHCPv4 option for PANA Authentication Agent has the format shown
 in Figure 1.
    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  option-code  | option-length |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               |
    +      PAA IPv4 Address         +
    |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             ...               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Figure 1: PAA DHCPv4 option
    option-code:        OPTION_PANA_AGENT (136).
    option-length:      Length of the 'options' field in octets;
                        MUST be a multiple of four (4).
    PAA IPv4 Address:   IPv4 address of a PAA for the client to use.
                        The PAAs are listed in the order of preference
                        for use by the client.
 A PaC (DHCPv4 client) SHOULD request the PAA DHCPv4 Option in a
 Parameter Request List, as described in [RFC2131] and [RFC2132].
 If configured with a (list of) PAA address(es), a DHCPv4 server
 SHOULD send a client the PAA DHCPv4 option, even if this option is
 not explicitly requested by the client.
 A PaC (DHCPv4 client) receiving the PAA DHCPv4 option SHOULD use the
 (list of) IP address(es) to locate PAA(s).
 The PaC (DHCPv4 client) MUST try the records in the order listed in
 the PAA DHCPv4 option received from the DHCPv4 server.

Morand, et al. Standards Track [Page 3] RFC 5192 PAA DHCP Options May 2008

5. PANA Authentication Agent DHCPv6 Option

 This DHCPv6 option carries a list of 128-bit (binary) IPv6 addresses
 indicating PANA Authentication Agents (PAAs) available to the PANA
 client (PaC).
 The DHCPv6 option for PANA Authentication Agent has the format shown
 in Figure 2.
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       option-code             |       option-length           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                                                               +
    |                                                               |
    +                         PAA IPv6 Address                      +
    |                                                               |
    +                                                               +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          ....                                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 2: PAA DHCPv6 option
    option-code:        OPTION_PANA_AGENT (40).
    option-length:      Length of the 'options' field in octets;
                        MUST be a multiple of sixteen (16).
    PAA IPv6 Address:   IPv6 address of a PAA for the client to use.
                        The PAAs are listed in the order of preference
                        for use by the client.
 A PaC DHCPv6 client SHOULD request the PAA DHCPv6 option in an
 Options Request Option (ORO) as described in the DHCPv6 specification
 [RFC3315].
 If configured with a (list of) PAA address(es), a DHCPv6 server
 SHOULD send a client the PAA DHCPv6 option, even if this option is
 not explicitly requested by the client.
 A PaC (DHCPv6 client) receiving the PAA DHCPv6 option SHOULD use the
 (list of) IP address(es) to locate PAA(s).
 The PaC (DHCPv6 client) MUST try the records in the order listed in
 the PAA DHCPv6 option received from the DHCPv6 server.

Morand, et al. Standards Track [Page 4] RFC 5192 PAA DHCP Options May 2008

6. IANA Considerations

 The following DHCPv4 option code for PANA Authentication Agent
 options has been assigned by IANA:
    Option  Name           Value       Described in
    -----------------------------------------------
    OPTION_PANA_AGENT       136         Section 4
 The following DHCPv6 option code for PANA Authentication Agent
 options has been assigned by IANA:
    Option  Name            Value       Described in
    ------------------------------------------------
    OPTION_PANA_AGENT        40         Section 5

7. Security Considerations

 The security considerations in [RFC2131], [RFC2132], and [RFC3315]
 apply.  If an adversary manages to modify the response from a DHCP
 server or insert its own response, a PANA Client could be led to
 contact a rogue PANA Authentication Agent, possibly one that then
 intercepts authentication requests and/or denies network access to
 the access device.
 In most networks, the DHCP exchange that delivers the options prior
 to network access authentication is neither integrity protected nor
 origin authenticated.  Therefore, the options defined in this
 document MUST NOT be used to perform any negotiation on the use of
 PANA between the PANA Client and a PANA Authentication Agent.  Using
 the presence (or absence) of these DHCP options as an indication of
 network mandating PANA authentication (or not) is an example of such
 a negotiation mechanism.  This negotiation would allow bidding-down
 attacks by making the clients choose to use a lower-grade security
 mechanism (or even no security at all).

8. Acknowledgements

 We would like to thank Ralph Droms, Stig Venaas, Ted Lemon, Andre
 Kostur and Bernie Volz for their valuable comments.  We would also
 like to thank Jari Arkko, Thomas Narten and Bernard Aboba that
 provided several reviews, as well as all members of the PANA and DHC
 working groups that contribute to improve this document.

Morand, et al. Standards Track [Page 5] RFC 5192 PAA DHCP Options May 2008

9. References

9.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
            RFC 2131, March 1997.
 [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
            Extensions", RFC 2132, March 1997.
 [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
            and M. Carney, "Dynamic Host Configuration Protocol for
            IPv6 (DHCPv6)", RFC 3315, July 2003.
 [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

 [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
            Levkowetz, "Extensible Authentication Protocol (EAP)",
            RFC 3748, June 2004.

Morand, et al. Standards Track [Page 6] RFC 5192 PAA DHCP Options May 2008

Authors' Addresses

 Lionel Morand
 France Telecom R&D
 EMail: lionel.morand@orange-ftgroup.com
 Alper E. Yegin
 Samsung
 EMail: a.yegin@partner.samsung.com
 Suraj Kumar
 Tech Mahindra Ltd
 EMail: surajk@techmahindra.com
 Syam Madanapalli
 Samsung
 EMail: syam@samsung.com

Morand, et al. Standards Track [Page 7] RFC 5192 PAA DHCP Options May 2008

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 contained in BCP 78, and except as set forth therein, the authors
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Morand, et al. Standards Track [Page 8]

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