draft-ietf-dhc-agentopt-radius-04.txt   draft-ietf-dhc-agentopt-radius-05.txt 
Network Working Group R. Droms Network Working Group R. Droms
Internet-Draft J. Schnizlein Internet-Draft J. Schnizlein
Expires: August 4, 2004 Cisco Systems Expires: September 30, 2004 Cisco Systems
February 4, 2004 April 1, 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-04.txt draft-ietf-dhc-agentopt-radius-05.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.
skipping to change at page 1, line 32 skipping to change at page 1, line 32
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt. www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 4, 2004. This Internet-Draft will expire on September 30, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). 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 NAS (network access server) may choose to authenticate the identity
device before granting that device access to the network. The IEEE of a device before granting that device access to the network. The
802.1X protocol is an example of a mechanism for providing IEEE 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
address for assignment to the device through its DHCP client. The configuration parameters to be delivered to the device through its
RADIUS Attributes sub-option enables a network element to pass along DHCP client. The RADIUS Attributes sub-option enables a network
attributes for the user of a device received during RADIUS element to pass along attributes for the user of a device received
authentication to a DHCP server. during RADIUS 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 in which network elements can pass information
obtained through layer 2 authentication to a DHCP server [2]. IEEE obtained through layer 2 authentication to a DHCP server [2]. IEEE
802.1X [3] is an example of a mechanism through which a network 802.1X is an example of a mechanism through which a NAS such as a
access device such as a switch or a wireless LAN access point can switch or a wireless LAN access point can authenticate the identity
authenticate the identity of the user of a device before providing of the user of a device before providing layer 2 network access using
layer 2 network access using RADIUS [4] as the Authentication Service RADIUS as the Authentication Service specified in RFC3580 [9]. In
specified in 802.1X. In 802.1X authenticated access, a device must 802.1X authenticated access, a device must first exchange some
first exchange some authentication credentials with the network authentication credentials with the NAS. The NAS then supplies these
access device. The access device then supplies these credentials to credentials to a RADIUS server, which either confirms or denies the
a RADIUS server, which either confirms or denies the identity of the identity of the user of the device requesting network access. The
user of the device requesting network access. The access device, NAS, 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.
+-----------------+ +-----------------+
|Device requesting| |Device requesting|
| network access | | network access |
+-----------------+ +-----------------+
| ^ | ^
| | | |
(1) Request for access (1) Request for access
| | | |
| (4) Access granted | (4) Success/Failure
v | v |
+-----------------+ +-----------------+
| Access Device | | NAS |
|(802.1X and DHCP | |(802.1X and DHCP |
| relay agent} | | relay agent} |
+-----------------+ +-----------------+
| ^ | ^
| | | |
(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. At the successful conclusion of IEEE 802.1X authentication,
RADIUS server carries additional identification information as a RADIUS Access-Accept provides attributes for service authorizations
attributes to the access device. The access device stores these to the NAS. The NAS stores these attributes locally. When the NAS
attributes locally. When the access device subsequently forwards DHCP subsequently forwards DHCP messages from the network device, the NAS
messages from the network device, the access device adds the adds these attributes in a RADIUS Attributes sub-option. The RADIUS
identification information in an RADIUS Attributes sub-option. The Attributes sub-option is another suboption of the Relay Agent
RADIUS Attributes sub-option is another suboption of the Relay Agent Information option [4].
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 a NAS. The RADIUS Attributes sub-option described in this
described in this document is not limited to use in conjunction with document is not limited to use in conjunction with IEEE 802.1X and
IEEE 802.1X and can be used to carry RADIUS attributes obtained by can be used to carry RADIUS attributes obtained by the relay agent
the relay agent for any reason. for any reason.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]. document are to be interpreted as described in RFC 2119 [1].
2.1 General Terminology 2.1 DHCP Terminology
Access device: A network element providing network access to a host
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 2.2 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 service through the RADIUS server: An entity that provides 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
NAS: Network access server; unlike traditional dial NAS, the NAS
considered here may not have a protocol like PPP through which it
can pass configuration information from the RADIUS attributes to
the client
2.4 802.1X Terminology 2.3 802.1X 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
The RADIUS Attributes Sub-option is a new sub-option for the DHCP The RADIUS Attributes Sub-option is a new sub-option for the DHCP
Relay Agent option. Relay Agent option.
The format of the RADIUS Attributes sub-option is: The format of the RADIUS Attributes sub-option is:
skipping to change at page 4, line 28 skipping to change at page 4, line 18
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. RADIUS Server Behavior 4. RADIUS Server Behavior
The RADIUS server MUST return the User-Name and Class attributes to The RADIUS server that implements this specification MUST be
the access device, and MAY return other attributes. configured to return the User-Name and Class attributes to the NAS,
and MAY return other attributes.
To avoid dependencies between the address allocation and other state To avoid dependencies between the address allocation and other state
information between the RADIUS server and the DHCP server, only the information between the RADIUS server and the DHCP server, only the
attributes in the table below SHOULD be included in this sub-option. 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 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 2865 that "A NAS MUST treat a RADIUS access-accept authorizing an
unavailable service as an access-reject instead.", a RADIUS server unavailable service as an access-reject instead.", a RADIUS server
SHOULD send only those attributes for which the relay agent can SHOULD send only those attributes for which the relay agent can
ensure that either the relay agent or the DHCP server will provide ensure that either the relay agent or the DHCP server will provide
the associated service. The following table, based on the analysis the associated service. The following table, based on the analysis
in RFC 3580 [10], lists attributes that MAY be included: in RFC 3580 [9], lists attributes that MAY be included:
# Attribute # Attribute
--- --------- --- ---------
1 User-Name (RFC 2865) 1 User-Name (RFC 2865 [3])
4 NAS-IP-Address (RFC 2865) 4 NAS-IP-Address (RFC 2865)
6 Service-Type (RFC 2865) 6 Service-Type (RFC 2865)
25 Class (RFC 2865) 25 Class (RFC 2865)
26 Vendor-Specific (RFC 2865) 26 Vendor-Specific (RFC 2865)
27 Session-Timeout (RFC 2865) 27 Session-Timeout (RFC 2865)
30 Called-Station-Id (RFC 2865) 30 Called-Station-Id (RFC 2865)
31 Calling-Station-Id (RFC 2865) 31 Calling-Station-Id (RFC 2865)
32 NAS-Identifier (RFC 2865) 32 NAS-Identifier (RFC 2865)
44 Acct-Session-Id (RFC 2866) 44 Acct-Session-Id (RFC 2866 [5])
50 Acct-Multi-Session-Id (RFC 2866) 50 Acct-Multi-Session-Id (RFC 2866)
87 NAS-Port-Id (RFC 2869) 87 NAS-Port-Id (RFC 2869 [6])
88 Framed-Pool (RFC 2869) 88 Framed-Pool (RFC 2869)
100 Framed-IPv6-Pool (RFC 3162) 100 Framed-IPv6-Pool (RFC 3162 [8])
5. DHCP Relay Agent Behavior 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 only
the attributes received in response to the client's authentication contain the attributes provided in the RADIUS Access/Accept message.
with the RADIUS service. The DHCP relay agent MUST NOT add more than The DHCP relay agent MUST NOT add more than one RADIUS Attributes
one RADIUS Attributes sub-option in a message. 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 if available, and MAY include other
attributes.
6. DHCP Server Behavior 6. DHCP Server Behavior
When the DHCP server receives a message from a relay agent containing When the DHCP server receives a message from a relay agent containing
a RADIUS Attributes sub-option, it extracts the contents of the of a RADIUS Attributes sub-option, it extracts the contents of the
the sub-option and uses that information in selecting configuration sub-option and uses that information in selecting configuration
parameters for the client. Even if the relay agent forwards other parameters for the client. Even if the relay agent forwards other
RADIUS attributes from the RADIUS server, the DHCP server SHOULD RADIUS attributes from the RADIUS server, the DHCP server SHOULD
ignore any attributes it receives for which it cannot ensure that the ignore any attributes it receives for which it cannot ensure that the
associated service will be provided either by the DHCP server or the associated service will be provided either by the DHCP server or the
relay agent. relay agent. If the DHCP server uses attributes not specified here,
it might result in side effects not anticipated in the existing
RADIUS specifications.
7. DHCP Client Behavior 7. DHCP Client Behavior
Relay agent options are exchanged only between relay agents and DHCP Relay agent options are exchanged only between relay agents and DHCP
server, so DHCP clients are never aware of their use. server, so DHCP clients are never aware of their use.
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 [8]. Potential exposures to attack are discussed in section 7 3118 [7]. 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 [11] or IPsec [12] SHOULD be deployed option for relay agent options [10] or IPsec [11] SHOULD be deployed
as 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. Acknowledgments
Cisco has a pending patent which relates to the subject matter of
this Internet Draft. If a standard relating to this subject matter is
adopted by IETF and any claims of any issued Cisco patents are
necessary for practicing this standard, any party will be able to
obtain a license from Cisco to use any such patent claims under
openly specified, reasonable, non-discriminatory terms to implement
and fully comply with the standard.
11. Acknowledgments
Bernard Aboba's expert advice on avoiding RADIUS entanglements is Bernard Aboba's expert advice on avoiding RADIUS entanglements is
gratefully acknowledged. 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] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
Network Access Control", IEEE Standard 802.1X, March 2001.
[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, [4] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046,
January 2001. January 2001.
Informative References Informative References
[6] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. [5] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
[7] Rigney, C., Willats, W. and P. Calhoun, "RADIUS Extensions", [6] Rigney, C., Willats, W. and P. Calhoun, "RADIUS Extensions",
RFC 2869, June 2000. RFC 2869, June 2000.
[8] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", [7] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
RFC 3118, June 2001. RFC 3118, June 2001.
[9] Aboba, B., Zorn, G. and D. Mitton, "RADIUS and IPv6", RFC 3162, [8] Aboba, B., Zorn, G. and D. Mitton, "RADIUS and IPv6", RFC 3162,
August 2001. August 2001.
[10] Congdon, P., Aboba, B., Smith, A., Zorn, G. and J. Roese, "IEEE [9] Congdon, P., Aboba, B., Smith, A., Zorn, G. and J. Roese, "IEEE
802.1X Remote Authentication Dial In User Service (RADIUS) 802.1X Remote Authentication Dial In User Service (RADIUS)
Usage Guidelines", RFC 3580, September 2003. Usage Guidelines", RFC 3580, September 2003.
[11] Stapp, M., Lemon, T. and R. Droms, "The Authentication [10] Stapp, M. and T. Lemon, "The Authentication Suboption for the
Suboption for the DHCP Relay Agent Option", DHCP Relay Agent Option", draft-ietf-dhc-auth-suboption-02
draft-ietf-dhc-auth-suboption-01 (work in progress), November (work in progress), October 2003.
2002.
[12] Droms, R., "Authentication of DHCP Relay Agent Options Using [11] 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
1414 Massachusetts Avenue 1414 Massachusetts Avenue
Boxborough, MA 01719 Boxborough, MA 01719
USA USA
skipping to change at page 8, line 26 skipping to change at page 8, line 26
licenses to be made available, or the result of an attempt made to licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat. be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights.
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/