draft-ietf-dhc-agentopt-radius-03.txt   draft-ietf-dhc-agentopt-radius-04.txt 
Network Working Group R. Droms Network Working Group R. Droms
Internet-Draft J. Schnizlein Internet-Draft J. Schnizlein
Expires: April 6, 2004 Cisco Systems Expires: August 4, 2004 Cisco Systems
October 7, 2003 February 4, 2004
RADIUS Attributes Sub-option for the DHCP Relay Agent Information RADIUS Attributes Sub-option for the DHCP Relay Agent Information
Option Option
draft-ietf-dhc-agentopt-radius-03.txt draft-ietf-dhc-agentopt-radius-04.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
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This Internet-Draft will expire on April 6, 2004. This Internet-Draft will expire on August 4, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
A network access device may choose to authenticate the identity of a A network access device may choose to authenticate the identity of a
device before granting that device access to the network. The IEEE device before granting that device access to the network. The IEEE
802.1X protocol is an example of a mechanism for providing 802.1X protocol is an example of a mechanism for providing
authenticated layer 2 network access. A network element using RADIUS authenticated layer 2 network access. A network element using RADIUS
as an authentication authority will receive attributes from a RADIUS as an authentication authority will receive attributes from a RADIUS
server that may be used by a DHCP server in the selection of an IP server that may be used by a DHCP server in the selection of an IP
address for assignment to the device through its DHCP client. The address for assignment to the device through its DHCP client. The
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2.2 DHCP Terminology 2.2 DHCP Terminology
The following terms are used as defined in RFC2131 and RFC3046: DHCP The following terms are used as defined in RFC2131 and RFC3046: DHCP
relay agent, DHCP server, DHCP client. relay agent, DHCP server, DHCP client.
2.3 RADIUS Terminology 2.3 RADIUS Terminology
The following terms are used in conjunction with RADIUS: The following terms are used in conjunction with RADIUS:
RADIUS server: An entity that provides RADIUS server: An entity that provides RADIUS service through the
RADIUS service through the exchange of RADIUS protocol messages exchange of RADIUS protocol messages
Attribute: Data value carried in a RADIUS protocol message Attribute: Data value carried in a RADIUS protocol message
2.4 802.1X Terminology 2.4 802.1X Terminology
The following terms are used as defined in the IEEE 802.1X protocol: The following terms are used as defined in the IEEE 802.1X protocol:
Authenticator, Supplicant. Authenticator, Supplicant.
3. RADIUS Attributes sub-option format 3. RADIUS Attributes sub-option format
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SubOpt Len RADIUS attributes SubOpt Len RADIUS attributes
code code
+-------+-----+------+------+------+------+--...-+------+ +-------+-----+------+------+------+------+--...-+------+
| TBD | N | b1 | b2 | b3 | b4 | | bN | | TBD | N | b1 | b2 | b3 | b4 | | bN |
+-------+-----+------+------+------+------+--...-+------+ +-------+-----+------+------+------+------+--...-+------+
The RADIUS attributes are encoded according to the encoding rules in The RADIUS attributes are encoded according to the encoding rules in
RFC 2865, in bytes b1...bN. RFC 2865, in bytes b1...bN.
4. DHCP Relay Agent Behavior 4. RADIUS Server Behavior
The RADIUS server MUST return the User-Name and Class attributes to
the access device, and MAY return other attributes.
To avoid dependencies between the address allocation and other state
information between the RADIUS server and the DHCP server, only the
attributes in the table below SHOULD be included in this sub-option.
Because RADIUS servers rely on the directive in section 1.1 or RFC
2865 that "A NAS MUST treat a RADIUS access-accept authorizing an
unavailable service as an access-reject instead.", a RADIUS server
SHOULD send only those attributes for which the relay agent can
ensure that either the relay agent or the DHCP server will provide
the associated service. The following table, based on the analysis
in RFC 3580 [10], lists attributes that MAY be included:
# Attribute
--- ---------
1 User-Name (RFC 2865)
4 NAS-IP-Address (RFC 2865)
6 Service-Type (RFC 2865)
25 Class (RFC 2865)
26 Vendor-Specific (RFC 2865)
27 Session-Timeout (RFC 2865)
30 Called-Station-Id (RFC 2865)
31 Calling-Station-Id (RFC 2865)
32 NAS-Identifier (RFC 2865)
44 Acct-Session-Id (RFC 2866)
50 Acct-Multi-Session-Id (RFC 2866)
87 NAS-Port-Id (RFC 2869)
88 Framed-Pool (RFC 2869)
100 Framed-IPv6-Pool (RFC 3162)
5. DHCP Relay Agent Behavior
When the DHCP relay agent receives a DHCP message from the client, it When the DHCP relay agent receives a DHCP message from the client, it
MAY append a DHCP Relay Agent Information option containing the MAY append a DHCP Relay Agent Information option containing the
RADIUS Attributes sub-option, along with any other sub-options it is RADIUS Attributes sub-option, along with any other sub-options it is
configured to supply. The RADIUS Attributes sub-option MUST contain configured to supply. The RADIUS Attributes sub-option MUST contain
the attributes received in response to the client's authentication the attributes received in response to the client's authentication
with the RADIUS service. The DHCP relay agent MUST NOT add more than with the RADIUS service. The DHCP relay agent MUST NOT add more than
one RADIUS Attributes sub-option in a message. one RADIUS Attributes sub-option in a message.
The relay agent SHOULD include the User-Name and Class attributes in The relay agent SHOULD include the User-Name and Class attributes in
the RADIUS Attributes sub-option, and MAY include other attributes. the RADIUS Attributes sub-option, and MAY include other attributes.
5. DHCP Server Behavior 6. DHCP Server Behavior
When the DHCP server receives a message from an relay agent
containing a RADIUS Attributes sub-option, it extracts the contents
of the of the sub-option and uses that information in selecting
configuration parameters for the client.
6. DHCP Client Behavior When the DHCP server receives a message from a relay agent containing
a RADIUS Attributes sub-option, it extracts the contents of the of
the sub-option and uses that information in selecting configuration
parameters for the client. Even if the relay agent forwards other
RADIUS attributes from the RADIUS server, the DHCP server SHOULD
ignore any attributes it receives for which it cannot ensure that the
associated service will be provided either by the DHCP server or the
relay agent.
The host need not make any special provision for the use of the 7. DHCP Client Behavior
RADIUS Attributes sub-option.
7. RADIUS Server Behavior Relay agent options are exchanged only between relay agents and DHCP
The RADIUS server MUST return the User-Name and Class attributes to server, so DHCP clients are never aware of their use.
the access device, and MAY return other attributes.
8. Security Considerations 8. Security Considerations
Message authentication in DHCP for intradomain use where the Message authentication in DHCP for intradomain use where the
out-of-band exchange of a shared secret is feasible is defined in RFC out-of-band exchange of a shared secret is feasible is defined in RFC
3118 [6]. Potential exposures to attack are discussed in section 7 3118 [8]. Potential exposures to attack are discussed in section 7
of the DHCP protocol specification in RFC 2131. of the DHCP protocol specification in RFC 2131.
The DHCP Relay Agent option depends on a trusted relationship between The DHCP Relay Agent option depends on a trusted relationship between
the DHCP relay agent and the server, as described in section 5 of RFC the DHCP relay agent and the server, as described in section 5 of RFC
3046. While the introduction of fraudulent relay-agent options can 3046. While the introduction of fraudulent relay-agent options can
be prevented by a perimeter defense that blocks these options unless be prevented by a perimeter defense that blocks these options unless
the relay agent is trusted, a deeper defense using the authentication the relay agent is trusted, a deeper defense using the authentication
option for relay agent options [7] or IPsec [8] SHOULD be deployed as option for relay agent options [11] or IPsec [12] SHOULD be deployed
well. as well.
9. IANA Considerations 9. IANA Considerations
IANA has assigned the value of TBD for the DHCP Relay Agent IANA has assigned the value of TBD for the DHCP Relay Agent
Information option sub-option code for this sub-option. This Information option sub-option code for this sub-option. This
document does not define any new namespaces or other constants for document does not define any new namespaces or other constants for
which IANA must maintain a registry. which IANA must maintain a registry.
10. Terms of Use 10. Terms of Use
Cisco has a pending patent which relates to the subject matter of Cisco has a pending patent which relates to the subject matter of
this Internet Draft. If a standard relating to this subject matter is this Internet Draft. If a standard relating to this subject matter is
adopted by IETF and any claims of any issued Cisco patents are adopted by IETF and any claims of any issued Cisco patents are
necessary for practicing this standard, any party will be able to necessary for practicing this standard, any party will be able to
obtain a license from Cisco to use any such patent claims under obtain a license from Cisco to use any such patent claims under
openly specified, reasonable, non-discriminatory terms to implement openly specified, reasonable, non-discriminatory terms to implement
and fully comply with the standard. and fully comply with the standard.
11. Acknowledgments
Bernard Aboba's expert advice on avoiding RADIUS entanglements is
gratefully acknowledged.
Normative References Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, [2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[3] Institute of Electrical and Electronics Engineers, "Port based [3] Institute of Electrical and Electronics Engineers, "Port based
Network Access Control", IEEE Standard 802.1X, March 2001. Network Access Control", IEEE Standard 802.1X, March 2001.
[4] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote [4] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865, June Authentication Dial In User Service (RADIUS)", RFC 2865, June
2000. 2000.
[5] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, [5] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046,
January 2001. January 2001.
Informative References Informative References
[6] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", [6] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
[7] Rigney, C., Willats, W. and P. Calhoun, "RADIUS Extensions",
RFC 2869, June 2000.
[8] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
RFC 3118, June 2001. RFC 3118, June 2001.
[7] Stapp, M., Lemon, T. and R. Droms, "The Authentication Suboption [9] Aboba, B., Zorn, G. and D. Mitton, "RADIUS and IPv6", RFC 3162,
for the DHCP Relay Agent Option", August 2001.
[10] Congdon, P., Aboba, B., Smith, A., Zorn, G. and J. Roese, "IEEE
802.1X Remote Authentication Dial In User Service (RADIUS)
Usage Guidelines", RFC 3580, September 2003.
[11] Stapp, M., Lemon, T. and R. Droms, "The Authentication
Suboption for the DHCP Relay Agent Option",
draft-ietf-dhc-auth-suboption-01 (work in progress), November draft-ietf-dhc-auth-suboption-01 (work in progress), November
2002. 2002.
[8] Droms, R., "Authentication of DHCP Relay Agent Options Using [12] Droms, R., "Authentication of DHCP Relay Agent Options Using
IPsec", draft-ietf-dhc-relay-agent-ipsec-00 (work in progress), IPsec", draft-ietf-dhc-relay-agent-ipsec-00 (work in progress),
September 2003. September 2003.
Authors' Addresses Authors' Addresses
Ralph Droms Ralph Droms
Cisco Systems Cisco Systems
250 Apollo Drive 1414 Massachusetts Avenue
Chelmsford, MA 01824 Boxborough, MA 01719
USA USA
EMail: rdroms@cisco.com EMail: rdroms@cisco.com
John Schnizlein John Schnizlein
Cisco Systems Cisco Systems
9123 Loughran Road 9123 Loughran Road
Fort Washington, MD 20744 Fort Washington, MD 20744
USA USA
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Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
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