DHCP Option for The Open Group's User Authentication Protocol

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright © The Internet Society (1999). All Rights Reserved.

Abstract

This document defines a DHCP [1] option that contains a list of pointers to User Authentication Protocol servers that provide user authentication services for clients that conform to The Open Group Network Computing Client Technical Standard [2].

Introduction

The Open Group Network Computing Client Technical Standard, a product of The Open Group's Network Computing Working Group (NCWG), defines a network computing client user authentication facility named the User Authentication Protocol (UAP).

UAP provides two levels of authentication, basic and secure. Basic authentication uses the Basic Authentication mechanism defined in the HTTP 1.1 [3] specification. Secure authentication is simply basic authentication encapsulated in an SSLv3 [4] session.

In both cases, a UAP client needs to obtain the IP address and port of the UAP service. Additional path information may be required, depending on the implementation of the service. A URL [5] is an excellent mechanism for encapsulation of this information since many UAP servers will be implemented as components within legacy HTTP/SSL servers.

Most UAP clients have no local state and are configured when booted through DHCP. No existing DHCP option [6] has a data field that contains a URL. Option 72 contains a list of IP addresses for WWW servers, but it is not adequate since a port and/or path can not be specified. Hence there is a need for an option that contains a list of URLs.

User Authentication Protocol Option

This option specifies a list of URLs, each pointing to a user authentication service that is capable of processing authentication requests encapsulated in the User Authentication Protocol (UAP). UAP servers can accept either HTTP 1.1 or SSLv3 connections. If the list includes a URL that does not contain a port component, the normal default port is assumed (i.e., port 80 for http and port 443 for https). If the list includes a URL that does not contain a path component, the path /uap is assumed.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |    Length     |   URL list
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   
      Code            98
   
      Length          The length of the data field (i.e., URL list) in
                      bytes.
   
      URL list        A list of one or more URLs separated by the ASCII
                      space character (0x20).

References

   [1]  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
   
        March 1997.
   
   [2]  Technical Standard: Network Computing Client, The Open Group,
        Document Number C801, October 1998.
   
   [3]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., and T.
        Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC
        2068, January 1997.
   
   [4]  Freier, A., Karlton, P., and P. Kocher, "The SSL Protocol,
        Version 3.0", Netscape Communications Corp., November 1996.
        Standards Information Base, The Open Group,
        http://www.db.opengroup.org/sib.htm#SSL_3.
   
   [5]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
        Resource Locators (URL)", RFC 1738, December 1994.
   
   [6]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
        Extensions", RFC 2132, March 1997.

Security Considerations

DHCP currently provides no authentication or security mechanisms. Potential exposures to attack are discussed in section 7 of the DHCP protocol specification.

The User Authentication Protocol does not have a means to detect whether or not the client is communicating with a rogue authentication service that the client contacted because it received a forged or otherwise compromised UAP option from a DHCP service whose security was compromised. Even secure authentication does not provide relief from this type of attack. This security exposure is mitigated by the environmental assumptions documented in the Network Computing Client Technical Standard.

Author's Address

Steve Drach
Sun Microsystems, Inc.
901 San Antonio Road
Palo Alto, CA 94303

   Phone: (650) 960-1300
   EMail: drach@sun.com

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Copyright © The Internet Society (1999). All Rights Reserved.

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