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Forcerenew Nonce Authentication
RFC 6704

Internet Engineering Task Force (IETF)                          D. Miles
Request for Comments: 6704                                        Google
Updates: 3203                                                     W. Dec
Category: Standards Track                                  Cisco Systems
ISSN: 2070-1721                                               J. Bristow
                                                     Swisscom Schweiz AG
                                                             R. Maglione
                                                          Telecom Italia
                                                             August 2012

                    Forcerenew Nonce Authentication

Abstract

   Dynamic Host Configuration Protocol (DHCP) FORCERENEW allows for the
   reconfiguration of a single host by forcing the DHCP client into a
   Renew state on a trigger from the DHCP server.  In the Forcerenew
   Nonce Authentication protocol, the server sends a nonce to the client
   in the initial DHCP ACK that is used for subsequent validation of a
   FORCERENEW message.  This document updates RFC 3203.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6704.

Miles, et al.                Standards Track                    [Page 1]
RFC 6704                    Forcerenew Nonce                 August 2012

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................2
   2. Requirements Language ...........................................3
   3. Message Authentication ..........................................3
      3.1. Forcerenew Nonce Authentication ............................3
           3.1.1. Forcerenew Nonce Protocol Capability Option .........4
           3.1.2. Forcerenew Nonce Authentication Protocol ............6
           3.1.3. Server Considerations for Forcerenew Nonce
                  Authentication ......................................8
           3.1.4. Client Considerations for Forcerenew Nonce
                  Authentication ......................................9
   4. IANA Considerations ............................................10
   5. Security Considerations ........................................10
      5.1. Protocol Vulnerabilities ..................................11
   6. Acknowledgements ...............................................11
   7. Normative References ...........................................11

1.  Introduction

   The DHCP reconfigure extension defined in [RFC3203] is a useful
   mechanism allowing dynamic reconfiguration of a single host triggered
   by the DHCP server.  Its application is currently limited by a
   requirement that a Forcerenew message is always authenticated using
   procedures as described in [RFC3118].  Authentication for DHCP
   [RFC3118] is mandatory for FORCERENEW; however, as it is currently
   defined, [RFC3118] requires distribution of constant token or shared-
   secret out-of-band to DHCP clients.

   The motivation for making authentication mandatory in DHCP FORCERENEW
   was to prevent an off-network attacker from taking advantage of DHCP
   FORCERENEW to accurately predict the timing of a DHCP renewal.
   Without DHCP FORCERENEW, DHCP renewal timing is under the control of

Miles, et al.                Standards Track                    [Page 2]
RFC 6704                    Forcerenew Nonce                 August 2012

   the client, and an off-network attacker has no way of predicting when
   it will happen, since it doesn't have access to the exchange between

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