RADIUS Attributes Permitted in RADIUS Attributes DHCP Suboption

Internet-Draft	RADIUS Attributes DHCP Suboption	October 2022
Boucadair	Expires 20 April 2023	[Page]

Abstract

The RADIUS Attributes suboption, specified in RFC 4014, enables a DHCP relay agent to pass identification and authorization information received during RADIUS authentication to a DHCP server. However, RFC 4014 defines a frozen list of RADIUS attributes that can be included in such a suboption.¶

This document updates RFC 4014 by relaxing that constraint and allowing to tag additional RADIUS Attributes as permitted in the RADIUS Attributes DHCP suboption.¶

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

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This Internet-Draft will expire on 20 April 2023.¶

Copyright Notice

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1. Introduction

The RADIUS Attributes suboption ([RFC4014]) enables a network element to pass identification and authorization attributes received during RADIUS authentication [RFC2865] to a DHCP server [RFC2131]. However, [RFC4014] defines a frozen set of RADIUS attributes that can be included in such a suboption. This limitation is suboptimal in contexts where new services are deployed (e.g., support of encrypted DNS [I-D.ietf-add-dnr]).¶

Section 3 updates RFC 4014 by relaxing that constraint and allowing to tag additional RADIUS Attributes as permitted in the RADIUS Attributes DHCP suboption. To that aim, a new IANA registry is created to maintain the set of permitted attributes in the RADIUS Attributes DHCP suboption. The maintenance of such a registry is similar to the one in [RFC7037].¶

[I-D.ietf-opsawg-add-encrypted-dns] defines the DHCPv4-Options RADIUS attribute that can be used by a DHCP relay agent, collocated with a RADIUS client, to pass attributes obtained from a RADIUS server to a DHCP server. The DHCPv4-Options RADIUS attribute can, for example, include a list of encrypted DNS resolvers.¶

3. Updates to RFC4014

3.1. Section 3 of RFC4014

This document updates Section 3 of [RFC4014] as follows:¶

OLD:

To avoid dependencies between the address allocation and other state information between the RADIUS server and the DHCP server, the DHCP relay agent SHOULD include only the attributes in the table below in an instance of the RADIUS Attributes suboption. The table, based on the analysis in RFC 3580 [8], lists attributes that MAY be included:¶

           #   Attribute
         ---   ---------
           1   User-Name (RFC 2865 [3])
           6   Service-Type (RFC 2865)
          26   Vendor-Specific (RFC 2865)
          27   Session-Timeout (RFC 2865)
          88   Framed-Pool (RFC 2869)
         100   Framed-IPv6-Pool (RFC 3162 [7])

NEW:

To avoid dependencies between the address allocation and other state information between the RADIUS server and the DHCP server, the DHCP relay agent SHOULD include only the attributes in the IANA-maintained registry (Section 4) in an instance of the RADIUS Attributes suboption.¶

3.2. Section 4 of RFC4014

This document updates Section 4 of [RFC4014] as follows:¶

OLD:: If the relay agent relays RADIUS attributes not included in the table in Section 4, the DHCP server SHOULD ignore them.¶
NEW:: If the relay agent relays RADIUS attributes not included in the IANA-maintained registry (Section 4), the DHCP server SHOULD ignore them.¶

4. IANA Considerations

IANA is requested to create a new sub-registry entitled "RADIUS Attributes Permitted in RADIUS Attributes Sub-option" in the "Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters" registry [BOOTP].¶

The allocation policy of this new sub-registry is Expert Review per [RFC8126]. Designated experts should carefully consider the security implications of allowing the relay agent to include new RADIUS attributes to this registry.¶

The initial content of this sub-registry is listed in Table 1. The reference may include the document that registers or specifies the Attribute.¶

Table 1: RADIUS Attributes Permitted in RADIUS Attributes Suboption
Type Code	Attribute	Reference
1	User-Name	RFC 2865
6	Service-Type	RFC 2865
26	Vendor-Specific	RFC 2865
27	Session-Timeout	RFC 2865
88	Framed-Pool	RFC 2869
100	Framed-IPv6-Pool	RFC 3162
TBA	DHCPv4-Options	I-D.ietf-opsawg-add-encrypted-dns

Note to the RFC Editor:: Please replace "TBA" with the code assigned for the DHCPv4-Options Attribute in [I-D.ietf-opsawg-add-encrypted-dns].¶

7. References

7.1. Normative References

[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC2131]: Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, DOI 10.17487/RFC2131, March 1997, <https://www.rfc-editor.org/info/rfc2131>.
[RFC2865]: Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, DOI 10.17487/RFC2865, June 2000, <https://www.rfc-editor.org/info/rfc2865>.
[RFC4014]: Droms, R. and J. Schnizlein, "Remote Authentication Dial-In User Service (RADIUS) Attributes Suboption for the Dynamic Host Configuration Protocol (DHCP) Relay Agent Information Option", RFC 4014, DOI 10.17487/RFC4014, February 2005, <https://www.rfc-editor.org/info/rfc4014>.
[RFC8126]: Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2. Informative References

[BOOTP]: IANA, "Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters", <https://www.iana.org/assignments/bootp-dhcp-parameters/bootp-dhcp-parameters.xhtml>.
[I-D.ietf-add-dnr]: Boucadair, M., Reddy, T., Wing, D., Cook, N., and T. Jensen, "DHCP and Router Advertisement Options for the Discovery of Network-designated Resolvers (DNR)", Work in Progress, Internet-Draft, draft-ietf-add-dnr-13, 13 August 2022, <https://www.ietf.org/archive/id/draft-ietf-add-dnr-13.txt>.
[I-D.ietf-opsawg-add-encrypted-dns]: Boucadair, M. and T. Reddy.K, "RADIUS Extensions for Encrypted DNS", Work in Progress, Internet-Draft, draft-ietf-opsawg-add-encrypted-dns-03, 6 October 2022, <https://www.ietf.org/archive/id/draft-ietf-opsawg-add-encrypted-dns-03.txt>.
[RFC7037]: Yeh, L. and M. Boucadair, "RADIUS Option for the DHCPv6 Relay Agent", RFC 7037, DOI 10.17487/RFC7037, October 2013, <https://www.rfc-editor.org/info/rfc7037>.