Internet DRAFT - draft-ietf-dhc-dhcpv6-radius-opt
draft-ietf-dhc-dhcpv6-radius-opt
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
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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
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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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