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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 7037

DHC Working Group                                                 L. Yeh
Internet-Draft                                   Freelancer Technologies
Intended status: Standards Track                            M. Boucadair
Expires: January 30, 2014                                 France Telecom
                                                           July 29, 2013


                  RADIUS Option for DHCPv6 Relay Agent
                  draft-ietf-dhc-dhcpv6-radius-opt-14

Abstract

   The DHCPv6 RADIUS option provides a mechanism to exchange
   authorization and identification information between DHCPv6 relay
   agent and DHCPv6 server.  This architecture assumes that the Network
   Access Server(NAS) acts as both DHCPv6 relay agent and RADIUS client.
   When receiving messages from the DHCPv6 clients, the NAS consults the
   RADIUS server and adds the RADIUS response when forwarding the DHCPv6
   client's messages to the DHCPv6 server.  The DHCPv6 server then uses
   that additional information to generate appropriate response to the
   DHCPv6 client's requests.

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-
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 30, 2014.

Copyright Notice

   Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology and Language . . . . . . . . . . . . . . . . . . .  3
   3.  Network Scenarios  . . . . . . . . . . . . . . . . . . . . . .  4
   4.  DHCPv6 RADIUS option . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  RADIUS attributes permitted in DHCPv6 RADIUS option  . . .  8
   5.  DHCPv6 Relay Agent Behavior  . . . . . . . . . . . . . . . . .  8
   6.  DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . .  8
   7.  DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . .  8
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     11.2. Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11



























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1.  Introduction

   DHCPv6 provides a mechanism that allows the server to assign or
   delegate both stateful and stateless configuration parameters to the
   clients.  The stateful configuration parameters include IPv6 address
   [RFC3315] and IPv6 prefix [RFC3633].  The stateless configuration
   parameters [RFC3736] include, for example, DNS [RFC3646], or a FQDN
   of AFTR [RFC6334].  In the scenarios described in this document, the
   DHCPv6 server is deployed in the central part of an ISP network.

   RADIUS [RFC2865] is widely used as the centralized authentication,
   authorization and user management mechanism for service provision in
   Broadband access network.  [RFC3162], [RFC4818], [RFC6519] and
   [RFC6911] specified the attributes that support the service provision
   for IPv6-only and IPv6-transition access.  The RADIUS server
   authorizes the Network Access Server (NAS) to assign an IPv6 address
   or prefix from the indicated pool, or to assign an IPv6 address or
   prefix with an explicitly indicated value, and other configuration
   parameters as per the attributes for the subscribers.

   When the NAS acts as distributed DHCPv6 server and RADIUS client
   simultaneously, it communicates with RADIUS server after receiving
   request from DHCPv6 client.  Upon receiving the Access-Accept message
   from the RADIUS server, the NAS then responds to the DHCPv6 client's
   requests per the associated authorization information indicated by
   the RADIUS attributes in the Access-Accept message.  When NAS acts as
   DHCPv6 relay agent and RADIUS client simultaneously, and the
   centralized DHCPv6 server is co-located with the RADIUS server, they
   may share the same database of the users; but when the centralized
   DHCPv6 server is not located in the same place as the RADIUS server,
   a new communication mechanism is needed for the DHCPv6 relay agent to
   transfer the authorization information indicated by the RADIUS
   attributes to the DHCPv6 server.


2.  Terminology and Language

   This document specifies a new DHCPv6 option for the DHCPv6 Relay
   Agent to transfer the authorization information of RADIUS attributes
   received in the Access-Accept message from the RADIUS server to the
   centralized DHCPv6 server.  Definitions for terms and acronyms not
   specified in this document are defined in [RFC2865] and [RFC3315].

   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].





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3.  Network Scenarios

   Figure 1 and Figure 2 show the typical network scenarios where the
   communication mechanism introduced in this document is necessary.  In
   these scenarios, the centralized DHCPv6 server is not co-located with
   the RADIUS server, but both of them are in the same administrative
   domain.  The NAS acts as the DHCPv6 relay agent and the RADIUS client
   simultaneously.  Figure 1 shows the sequence of DHCPv6 and RADIUS
   messages for IP over Ethernet (IPoE) access model, when the access
   loop adopts the direct Ethernet encapsulation.  Figure 2 shows the
   sequence of DHCPv6 and RADIUS messages for PPP over Ethernet (PPPoE)
   access model.

   The mechanism introduced in this document is a generic mechanism, and
   might also be employed in other network scenarios where the DHCPv6
   relay agent and the RADIUS client locate in the same device.



































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   +-------+                   +-------+                    +-------+
   |DHCPv6 |   Access Model:   |  NAS  |                    |RADIUS |
   |Client |       IPoE        |       |                    |Server |
   +-------+                   +-------+                    +-------+
                      RADIUS Client/DHCPv6 Relay Agent

       |                           |                            |
       |---Solicit---------------->|                            |
       |                           |---Access-Request---------->|
       |                           |                            |
       |                           |<--Access-Accept------------|
       |                           |(e.g. Delegated-IPv6-Prefix)|
       |                           |                            |

              DHCPv6 messages             RADIUS messages

                                                            +-------+
                                                            |DHCPv6 |
                                                            |Server |
                                                            +-------+
       |                           |                            |
       |                           |---Relay-forward----------->|
       |                           |  (OPTION_RADIUS)           |
       |                           |                            |
       |                           |<--Relay-reply -------------|
       |<--Advertise---------------|                            |
       |  (e.g. IA_PD)             |                            |
       |                           |                            |
       |---Request---------------->|                            |
       |  (e.g. IA_PD)             |---Relay-forward----------->|
       |                           |  (OPTION_RADIUS)           |
       |                           |                            |
       |                           |<--Relay-reply -------------|
       |<--Reply-------------------|                            |
       |  (e.g. IA_PD)             |                            |
       |                           |                            |

              DHCPv6 messages             DHCPv6 messages

   Figure 1: Network scenario and message sequence when employing DHCPv6
                       RADIUS option in IPoE access










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   +-------+                   +-------+                    +-------+
   |DHCPv6 |   Access Model:   |  NAS  |                    |RADIUS |
   |Client |      PPPoE        |       |                    |Server |
   +-------+                   +-------+                    +-------+
                      RADIUS Client/DHCPv6 Relay Agent

       |                           |                            |
       |--PPP LCP Config-Request-->|                            |
       |                           |---Access-Request---------->|
       |                           |                            |
       |                           |<--Access-Accept------------|
       |<----PPP LCP Config-ACK----|(e.g. Delegated-IPv6-Prefix)|
       |                           |                            |

               PPP messages               RADIUS messages

                                                            +-------+
                                                            |DHCPv6 |
                                                            |Server |
                                                            +-------+
       |                           |                            |
       |---Solicit---------------->|                            |
       |                           |---Relay-forward----------->|
       |                           |  (OPTION_RADIUS)           |
       |                           |                            |
       |                           |<--Relay-reply -------------|
       |<--Advertise---------------|                            |
       |  (e.g. IA_PD)             |                            |
       |                           |                            |
       |---Request---------------->|                            |
       |  (e.g. IA_PD)             |---Relay-forward----------->|
       |                           |  (OPTION_RADIUS)
       |                           |                            |
       |                           |<--Relay-reply -------------|
       |<--Reply-------------------|                            |
       |  (e.g. IA_PD)             |                            |
       |                           |                            |

              DHCPv6 messages             DHCPv6 messages

   Figure 2: Network scenario and message sequence when employing DHCPv6
                       RADIUS option in PPPoE access

   If the authentication or the authorization through RADIUS fails, the
   associated message sequences will stop.  The NAS acting as the DHCPv6
   relay agent will not forward the message received from the client to
   the DHCPv6 server.  If the authentication or the authorization
   through RADIUS passes, the NAS MUST store the information indicated



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   in the RADIUS attributes received in the Access-Accept message from
   the RADIUS server during the whole session.  How the NAS manages
   these information during the RADIUS session is out of the scope of
   this document.

   After receiving RENEW (5) message from the DHCPv6 client, the NAS
   SHOULD NOT initiate a new Access-Request/Access-Accept message
   exchange with the RADIUS server.  After receiving REBIND (6) message
   from the DHCPv6 client, the NAS MUST initiate a new Access-Request/
   Access-Accept message exchange with the RADIUS server, unless RADIUS
   capability is disabled on the NAS.


4.  DHCPv6 RADIUS option

   The OPTION_RADIUS is a DHCPv6 option used by the DHCPv6 relay agent
   to carry the authorization information of RADIUS attributes received
   in the Access-Accept message from the RADIUS server.

   The format of the OPTION_RADIUS option 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         OPTION_RADIUS         |          option-len           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            option-data (List of RADIUS Attributes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code      TBD
   option-len       Length of the option-data in octets
   option-data      List of one or more RADIUS attributes

   The option-data of OPTION_RADIUS is a list of one or more RADIUS
   attributes received in the Access-Accept message from the RADIUS
   server.  The format of RADIUS attributes is defined in section 5 of
   [RFC2865] as well as sections 2.1 and 2.2 of [RFC6929].  If multiple
   attributes with the same type (including the Long Extended type
   defined in sections 2.2 of [RFC6929]) are present, the order of
   attributes with the same type MUST be the same as that received from
   the RADIUS server.  The OPTION_RADIUS can only contain the RADIUS
   attributes listed in the IANA Registry of 'RADIUS attributes
   permitted in DHCPv6 RADIUS option'.

   According to the network scenarios described in section 3, the
   OPTION_RADIUS should appear in the RELAY-FORW (12) message relaying
   SOLICIT (1), REQUEST (3) and REBIND (6) from the DHCPv6 client, and
   may appear in the RELAY-FORW (12) relaying any other message from the



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   DHCPv6 client.

4.1.  RADIUS attributes permitted in DHCPv6 RADIUS option

   The RADIUS attributes listed in the below table are recommended as
   the first batch of attributes in the IANA Registry of 'RADIUS
   attributes permitted in DHCPv6 RADIUS option'.  New RADIUS attributes
   can be added to this list after Expert Review [RFC5226].

   Type Code  Attribute                   Reference
   26         Vendor-Specific             [RFC2865]
   123        Delegated-IPv6-Prefix       [RFC4818]
   144        DS-Lite-Tunnel-Name         [RFC6519]
   168        Framed-IPv6-Address         [RFC6911]
   169        DNS-Server-IPv6-Address     [RFC6911]
   171        Delegated-IPv6-Prefix-Pool  [RFC6911]
   172        Stateful-IPv6-Address-Pool  [RFC6911]

   Note: The RADIUS attribute's 'Length' defined in section 5 of
   [RFC2865] includes the length of 'Type' and 'Length' fields.


5.  DHCPv6 Relay Agent Behavior

   If the Relay Agent is configured to send OPTION_RADIUS, and the
   Access-Accept message from the RADIUS server contained RADIUS
   attributes permitted for use in OPTION_RADIUS, the Relay Agent MUST
   include OPTION_RADIUS in the RELAY-FORW (12) message.  The DHCPv6
   relay agent includes the permitted RADIUS attributes into
   OPTION_RADIUS one by one; if multiple attributes with the same type
   are present, the order of attributes with the same type MUST be the
   same as that received from the RADIUS server.


6.  DHCPv6 Server Behavior

   Upon receipt of the RELAY-FORW (12) message with OPTION_RADIUS from a
   relay agent, the DHCPv6 server that supports OPTION_RADIUS SHOULD
   extract and interpret the RADIUS attributes in the OPTION_RADIUS, and
   use that information in selecting configuration parameters for the
   requesting client.  If the DHCPv6 server does not support
   OPTION_RADIUS, the DHCPv6 server MUST silently discard this option.


7.  DHCPv6 Client Behavior

   OPTION_RADIUS is only exchanged between the relay agents and the
   servers.  DHCPv6 clients are not aware of the usage of OPTION_RADIUS.



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   DHCPv6 client MUST NOT send OPTION_RADIUS, and MUST ignore
   OPTION_RADIUS if received.


8.  Security Considerations

   Known security vulnerabilities of the DHCPv6 and RADIUS protocol may
   apply to its options.  Security issues related with DHCPv6 are
   described in section 23 of [RFC3315].  Security issues related with
   RADIUS are described in section 8 of [RFC2865], section 5 of
   [RFC3162], section 11 of [RFC6929].

   The mechanism described in this document may introduce new attack
   vector against the DHCPv6 server in case the DHCPv6 relay agent is
   compromised.  By forging the RADIUS attributes contained in the
   OPTION_RADIUS of the RELAY-FORW (12) messages, the attacker may
   influence the parameter assignment on the DHCPv6 server for the
   DHCPv6 clients.  However, as those network scenarios described in the
   section 3, NAS always belongs to the same administrative domain of
   the DHCPv6 server in the real deployment.

   Network administrators should be aware that although RADIUS messages
   are encrypted, DHCPv6 messages are always not encrypted.  It is
   possible that some RADIUS vendor-specific attributes might contain
   the sensitive or confidential information.  Network administrators
   are strongly advised to prevent including such information into
   DHCPv6 messages.

   If the use of vendor-specific attributes with confidential content is
   required, administrators are advised to use IPsec with encryption to
   protect the confidentiality of the RADIUS attributes.  Relay agents
   and servers implementing this specification MUST support the use of
   IPsec ESP with encryption in transport mode according to section
   3.1.1 of [RFC4303] and section 21.1 of [RFC3315].


9.  IANA Considerations

   This document requests to assign a new DHCPv6 option code for
   OPTION_RADIUS defined in section 4, and to create a new registry on
   the same assignment page, which is entitled as 'RADIUS attributes
   permitted in DHCPv6 RADIUS option' defined in section 4.1.  The new
   registry will enumerate the RADIUS Attributes Types
   (http://www.iana.org/assignments/radius-types/radius-types.xml) that
   are permitted to be included in the DHCPv6 RADIUS option.  The
   allocation policy of this 'RADIUS attributes permitted in DHCPv6
   RADIUS option' registry is Expert Review [RFC5226].  Designated
   expert should carefully consider the security implications of



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   allowing the relay agent to include new RADIUS attribute for the
   addition to this registry.


10.  Acknowledgements

   Thanks to Tomek Mrugalski, Bernie Volz, Gaurav Halwasia and Roberta
   Maglione for their thorough review comments in the mailing list of
   DHC working group, to Ted Lemon for his continuous encouragement and
   technical guidance.


11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

   [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.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

   [RFC4818]  Salowey, J. and R. Droms, "RADIUS Delegated-IPv6-Prefix
              Attribute", RFC 4818, April 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC6519]  Maglione, R. and A. Durand, "RADIUS Extensions for Dual-
              Stack Lite", RFC 6519, February 2012.

   [RFC6911]  Dec, W., Sarikaya, B., Zorn, G., Miles, D., and B.
              Lourdelet, "RADIUS Attributes for IPv6 Access Networks",
              RFC 6911, April 2013.

   [RFC6929]  DeKok, A. and A. Lior, "Remote Authentication Dial In User
              Service (RADIUS) Protocol Extensions", RFC 6929,
              April 2013.




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11.2.  Informative References

   [RFC3162]  Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
              RFC 3162, August 2001.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC3646]  Droms, R., "DNS Configuration options for Dynamic Host
              Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              December 2003.

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, April 2004.

   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
              RFC 6334, August 2011.


Authors' Addresses

   Leaf Y. Yeh
   Freelancer Technologies
   P. R. China

   Email: leaf.yeh.sdo@gmail.com


   Mohamed Boucadair
   France Telecom
   France

   Email: mohamed.boucadair@orange.com
















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