Radius Extensions R. Moskowitz Internet-Draft ICSAlabs a Division of Cybertrust Expires: August 18, 2005 Corporation February 14, 2005 RADIUS Security Roadmap draft-moskowitz-radius-sec-roadmap-00.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 20, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract RADIUS has become the defacto protocol between network edge devices (e,g, dial NAS or Wireless AP) and a backend Authentication Server. In this environment the backend Server is often called a (RADIUS Server). RADIUS is gaining very broad penetration, even into homes, because of its use with wireless authentication. Because of the amount of deployed infrastructure already in place, we believe that Moskowitz Expires August 20, 2005 [Page 1] Internet-Draft RADIUS Security Roadmap February 2005 RADIUS will not be supplanted by another authentication service in the foreseeable future. Because the widespread deployment in wireless has different infrastructure requirements than what is required for dialup, RADIUS requirements, especially trust between Edge devices and RADIUS Servers needs to be addressed. This document sets the requirements for RADIUS security and then sets forth technologies that will satisfy those requirements. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. RADIUS as a simple Client/Server environment . . . . . . . . . 3 3. RADIUS security requirements . . . . . . . . . . . . . . . . . 3 4. RADIUS identity credentials . . . . . . . . . . . . . . . . . 4 5. Establishment of Session keys . . . . . . . . . . . . . . . . 4 6. Communication Integrity and Privacy . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . 6 Moskowitz Expires August 20, 2005 [Page 2] Internet-Draft RADIUS Security Roadmap February 2005 1. Introduction The RADIUS [RFC2865] protocol carries sensitive user authentication information and various keys. When this protocol traverses networks that should be considered hostile such as when carried over a wireless link, the confidentiality of generic information in messages is not protected. There is also the risk of malicious RADIUS clients and servers that can act as Man-in-the-Middle (MITM) attack points, or allow malicious devices onto a network. The original security services in RADIUS are inadequate and incomplete as is evident in the wireless infrastructure case. This document sets forth the security requirements that is needed for RADIUS, and defines the services that can meet those requirements. Separate documents will provide full specifications for those services. 2. RADIUS as a simple Client/Server environment RADIUS consists of a set of clients and one or more servers. The clients are generically called Network Access Servers (NAS) and include most managed infrastructure platforms that provide network connectivity. RADIUS has a fairly straightforward stateless request/response protocol. It uses UDP as its transport. Although the protocol is stateless, a number of security requirements that are common to many such Client/Server environments can be defined. 3. RADIUS security requirements There are three principal security requirements for RADIUS that are standard for Client/Server Environments: o Creation and maintenance of identity credentials o Establishment of session keys o Communication Integrity and Privacy In the RADIUS environment it is desirable that these requirements are met: o Within the RADIUS protocol. That is without requiring services or additional infrastructure beyond RADIUS [e.g. IPsec, or either SSL or SNMPv3 for Identity management] o Simplicity in design, use, and user interfaces Moskowitz Expires August 20, 2005 [Page 3] Internet-Draft RADIUS Security Roadmap February 2005 4. RADIUS identity credentials The identity credentials SHALL be a 128-bit secret and the names of the RADIUS client and server. The names MUST NOT be IP addresses. The names can be any or no meaning, e.g. FQDNs, NAIs, randomly selected characters. This credential MAY be set manually on the client and server. There MUST be a mechanism within RADIUS to deploy and maintain this credential. It MUST support credentials for high availability RADIUS configurations (i.e. multiple servers accessible by the client with the same information. There MAY be a mechanism outside of RADIUS for the deployment and maintenance of this credential (e.g. SNMP). 5. Establishment of Session keys A session in RADIUS SHALL defined as commencing from the time of starting either the client or server service until either the client or server service terminates. The client is responsible for maintaining the session key. That is it will establish the session key on start up. If the server responds with a error of client key not known, the client will establish a new session key. Since this is a significant Denial of Service attack, this process MUST take steps to mitigate this attack. The session key is not used directly for protecting RADIUS datagrams. It is used to derive a set of keys that will be used. 6. Communication Integrity and Privacy Five 128-bit keys are needed: o Legacy use -- Used for the original RADIUS secret o Client Integrity -- Used by the client in a new message integrity attribute o Server Integrity -- Used by the server in a new message integrity attribute o Client Privacy -- Used by the client to encrypt attributes that require privacy o Server Privacy -- Used by the server to encrypt attributes that require privacy These keys will be derived from the session key through a key expansion function. A new message integrity attribute and a standard encrypt function will also be provided. Moskowitz Expires August 20, 2005 [Page 4] Internet-Draft RADIUS Security Roadmap February 2005 7. IANA Considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. 8. Security Considerations All in band keying methods that can be used to create the Identity credentials are subject to MITM attacks. This risk must either be accepted, or an out of band validation process SHALL be included. For example, if a Diffie-Hellman key exchange is used, then either party could validate the other party's public key by comparing a fingerprint of it to an externally obtained copy. This could be done at the server if the client has a manufacturer key pair and the fingerprint is included in the packing literature. 9. Acknowledgements This roadmap was developed with the able assistance of John Vollbrecht of Merit Networks and ????. 10. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2865] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. Author's Address Robert Moskowitz ICSAlabs a Division of Cybertrust Corporation 1000 Bent Creek Blvd, Suite 200 Mechanicsburg, PA 22222 USA Email: rgm@icsalabs.com Moskowitz Expires August 20, 2005 [Page 5] Internet-Draft RADIUS Security Roadmap February 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Moskowitz Expires August 20, 2005 [Page 6]