draft-ietf-dhc-agentopt-radius-02.txt   draft-ietf-dhc-agentopt-radius-03.txt 
Network Working Group R. Droms Network Working Group R. Droms
Internet-Draft J. Schnizlein Internet-Draft J. Schnizlein
Expires: April 30, 2003 Cisco Systems Expires: April 6, 2004 Cisco Systems
October 30, 2002 October 7, 2003
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-02.txt draft-ietf-dhc-agentopt-radius-03.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). 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
RADIUS Attributes sub-option enables a network element to pass along RADIUS Attributes sub-option enables a network element to pass along
attributes for the user of a device received during RADIUS attributes for the user of a device received during RADIUS
authentication to a DHCP server. authentication to a DHCP server.
1. Introduction and Background 1. Introduction and Background
The RADIUS Attributes sub-option for the DHCP Relay Agent option The RADIUS Attributes sub-option for the DHCP Relay Agent option
provides a way through which network elements can pass information provides a way through which network elements can pass information
obtained through layer 2 authentication to a DHCP server [4]. IEEE obtained through layer 2 authentication to a DHCP server [2]. IEEE
802.1X [2] is an example of a mechanism through which a network 802.1X [3] is an example of a mechanism through which a network
access device such as a switch or a wireless LAN access point can access device such as a switch or a wireless LAN access point can
authenticate the identity of the user of a device before providing authenticate the identity of the user of a device before providing
layer 2 network access using RADIUS [3] as the Authentication Service layer 2 network access using RADIUS [4] as the Authentication Service
specified in 802.1X. In 802.1X authenticated access, a device must specified in 802.1X. In 802.1X authenticated access, a device must
first exchange some authentication credentials with the network first exchange some authentication credentials with the network
access device. The access device then supplies these credentials to access device. The access device then supplies these credentials to
a RADIUS server, which either confirms or denies the identity of the a RADIUS server, which either confirms or denies the identity of the
user of the device requesting network access. The access device, user of the device requesting network access. The access device,
based on the reply of the RADIUS server, then allows or denies based on the reply of the RADIUS server, then allows or denies
network access to the requesting device. network access to the requesting device.
Figure 1 summarizes the message exchange among the participants in Figure 1 summarizes the message exchange among the participants in
IEEE 802.1X authentication. IEEE 802.1X authentication.
skipping to change at page 3, line 33 skipping to change at page 3, line 4
| ^ | ^
| | | |
(2) Request for authentication (2) Request for authentication
| | | |
| (3) Authentication confirm/deny | (3) Authentication confirm/deny
v | v |
+-----------------+ +-----------------+
| RADIUS | | RADIUS |
| Service | | Service |
+-----------------+ +-----------------+
Figure 1
Figure 1 Figure 1
In the application described in this document, the access device acts In the application described in this document, the access device acts
as an 802.1X authenticator and adds DHCP relay agent options to DHCP as an 802.1X authenticator and adds DHCP relay agent options to DHCP
messages. During 802.1X authentication, the reply message from the messages. During 802.1X authentication, the reply message from the
RADIUS server carries additional identification information as RADIUS server carries additional identification information as
attributes to the access device. The access device stores these attributes to the access device. The access device stores these
attributes locally. When the access device subsequently forwards attributes locally. When the access device subsequently forwards DHCP
DHCP messages from the network device, the access device adds the messages from the network device, the access device adds the
identification information in an RADIUS Attributes sub-option. The identification information in an RADIUS Attributes sub-option. The
RADIUS Attributes sub-option is another suboption of the Relay Agent RADIUS Attributes sub-option is another suboption of the Relay Agent
Information option [5]. Information option [5].
This document uses IEEE 802.1X as an example to motivate the use of This document uses IEEE 802.1X as an example to motivate the use of
RADIUS by an access device. The RADIUS Attributes sub-option RADIUS by an access device. The RADIUS Attributes sub-option
described in this document is not limited to use in conjunction with described in this document is not limited to use in conjunction with
IEEE 802.1X and can be used to carry RADIUS attributes obtained by IEEE 802.1X and can be used to carry RADIUS attributes obtained by
the relay agent for any reason. the relay agent for any reason.
skipping to change at page 5, line 31 skipping to change at page 5, line 4
containing a RADIUS Attributes sub-option, it extracts the contents containing a RADIUS Attributes sub-option, it extracts the contents
of the of the sub-option and uses that information in selecting of the of the sub-option and uses that information in selecting
configuration parameters for the client. configuration parameters for the client.
6. DHCP Client Behavior 6. DHCP Client Behavior
The host need not make any special provision for the use of the The host need not make any special provision for the use of the
RADIUS Attributes sub-option. RADIUS Attributes sub-option.
7. RADIUS Server Behavior 7. RADIUS Server Behavior
The RADIUS server MUST return the User-Name and Class attributes to The RADIUS server MUST return the User-Name and Class attributes to
the access device, and MAY return other attributes. the access device, and MAY return other attributes.
8. Security Considerations 8. Security Considerations
Message authentication in DHCP for intradomain use where the out-of- Message authentication in DHCP for intradomain use where the
band exchange of a shared secret is feasible is defined in RFC 3118 out-of-band exchange of a shared secret is feasible is defined in RFC
[6]. Potential exposures to attack are discussed in section 7 of the 3118 [6]. Potential exposures to attack are discussed in section 7
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] SHOULD be deployed as well. option for relay agent options [7] or IPsec [8] SHOULD be deployed 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 this Internet Draft. If a standard relating to this subject matter is
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.
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] Institute of Electrical and Electronics Engineers, "Port based [2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[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.
[3] 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.
[4] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[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] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
RFC 3118, June 2001. RFC 3118, June 2001.
[7] Lemon, T. and M. Stapp, "The Authentication Suboption for the [7] Stapp, M., Lemon, T. and R. Droms, "The Authentication Suboption
DHCP Relay Agent Option", draft-ietf-dhc-auth-suboption-00 (work for the DHCP Relay Agent Option",
in progress), June 2002. draft-ietf-dhc-auth-suboption-01 (work in progress), November
2002.
[8] Droms, R., "Authentication of DHCP Relay Agent Options Using
IPsec", draft-ietf-dhc-relay-agent-ipsec-00 (work in progress),
September 2003.
Authors' Addresses Authors' Addresses
Ralph Droms Ralph Droms
Cisco Systems Cisco Systems
250 Apollo Drive 250 Apollo Drive
Chelmsford, MA 01824 Chelmsford, MA 01824
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
EMail: jschnizl@cisco.com EMail: jschnizl@cisco.com
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