[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits]

Versions: 00 01 02 RFC 3594

   Internet Engineering Task Force                 P. Duffy
   INTERNET DRAFT                                  Cisco Systems
   DHC Working Group                               January 2003
   Document: draft-ietf-dhc-pktc-kerb-tckt-00.txt
  
  
                    Kerberos Ticket Control Sub-option
              for the CableLabs Client Configuration Option.
  
  
   Status of this Memo
  
      This document is an Internet-Draft and is in full conformance
      with all provisions of Section 10 of RFC 2026.
  
      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.
  
   Copyright Notice
  
      Copyright (C) The Internet Society (2003).  All Rights Reserved.
  
   Abstract
  
      This document defines a new sub-option for the CableLabs Client
      Configuration (CCC) Option.  This new sub-option will be used to
      direct CableLabs Client Devices (CCDs) to invalidate locally
      persisted Kerberos tickets.
  
   1.   Conventions used in this document
  
  
  Duffy                                                             1
  Internet Draft       Kerberos Ticket Control           January 2003
  
      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 [2].
  
   2.   Terminology
  
      Definitions of terms/acronyms used throughout this document:
  
      CCC - CableLabs Client Configuration option, described in [1].
  
      CCD - CableLabs Client Device.  A PacketCable MTA is an example
      of a CCD.
  
      KTC - Kerberos Ticket Control.  The CCC sub-option described in
      this document.
  
      MTA - Media Terminal Adapter. The CCD specific to the PacketCable
      architecture.
  
      PacketCable - multimedia architecture developed by CableLabs. See
      [6] for full details.
  
  
   3.   Introduction
  
      The CableLabs Client Configuration Option [1] defines several sub-
      options used to configure devices deployed into CableLabs
      architectures. These architectures employ the Kerberos protocol
      [3] to support CCD authentication and establishment of security
      associations between CCDs and application servers.
  
      CCDs are permitted to locally persist Kerberos tickets. Thus a
      power-cycled CCD is enabled to avoid expensive ticket acquisition
      for locally persisted, non-expired tickets.  This feature greatly
      reduces the Kerberos overhead of a deployment.
  
      This sub-option allows the service provider to control the
      lifetime of Kerberos tickets persisted locally on a CCD.  The
      service provider requires this capability to support operational
      functions such as disabling a subscriber's service, forcing re-
      establishment of security associations, or for testing and remote
      diagnostic of CCDs.
  
  
  Duffy                   Expires July 2003                         2
  Internet Draft       Kerberos Ticket Control           January 2003
  
   4.   Kerberos Ticket Control Sub-option
  
      This sub-option defines a Ticket Control Mask (TCM) that
      instructs the CCD to validate/invalidate specific application
      server tickets.  The sub-option is encoded as follows:
  
       Code   Len      TCM
      +-----+-----+-----+-----+
      | TBD |  2  | m1  | m2  |
      +-----+-----+-----+-----+
  
  
      The length MUST be 2.  The TCM field is encoded as an unsigned 16
      bit quantity per network byte-ordering rules.  Each bit of the TCM
      is assigned to a specific server or server group. A bit value of 0
      means the CCD MUST NOT invalidate the locally persisted ticket for
      the server/server group. A bit value of 1 means the CCD MUST
      invalidate the locally persisted ticket for the server/server
      group.
  
      Bit #0 is the least significant bit of the field. The bit
      positions are assigned as follows.
  
         Bit #0 - the PacketCable Provisioning Server used by the CCD.
  
         Bit #1 - the group of all PacketCable Call Management Servers
         used by the CCD.
  
         Bit #2 - #15. Reserved and MUST be set to 0.
  
      If a CCD does not locally persist Kerberos tickets, it MUST
      ignore this sub-option.
  
   5.   IANA Considerations
  
      IANA is requested to assign a sub-option code to this sub-option
      from the "CableLabs Client Configuration" sub-option number space
      (maintained within the BOOTP-DHCP Parameters Registry).
  
   6.   Security Considerations
  
      Potential DHCP protocol attack exposure is discussed in section 7
      of the DHCP protocol specification [4] and in Authentication for
      DHCP Messages [5].  Additional CCC attack exposure is discussed
      in [1].
  
  Duffy                   Expires July 2003                         3
  Internet Draft       Kerberos Ticket Control           January 2003
  
  
      The KTC sub-option could be used to disrupt a CableLabs
      architecture deployment.  In the specific case of PacketCable
      [6], a deployment could be disrupted if a large number of MTAs
      are reset/power cycled, initiate their provisioning flow [7], and
      are instructed by a malicious DHCP server to invalidate all
      Kerberos tickets.  This could lead to a Denial of Service (DoS)
      condition as this large set of MTAs simultaneously attempt to
      authenticate and obtain tickets from the Kerberos infrastructure.
  
      However, the scenario described above is unlikely to occur.
      Within the cable delivery architecture required by PacketCable
      (and other CableLabs architectures), the DHCP client is connected
      to a network through a cable modem and the CMTS (head-end). The
      CMTS is explicitly configured with a set of DHCP servers to which
      DHCP requests are forwarded.  Further, a correctly configured
      CMTS will only allow downstream traffic from specific IP
      addresses/ranges.
  
   7.   References
  
   7.1.  Normative
  
      [1] B. Beser and P. Duffy, "DHCP Option for CableLabs Client
      Configuration", http://www.ietf.org/internet-drafts/draft-ietf-
      dhc-packetcable-06.txt, January 2003.
  
      [2] S. Bradner, "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
  
  
   7.2.  Informational
  
      [3] J. Kohl and C. Neuman, "The Kerberos Network Authentication
      Service (V5)", RFC 1510, September 1993.
  
      [4] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,
      March 1997.
  
      [5] R. Droms and W. Arbaugh, "Authentication for DHCP Messages",
      RFC 3118, June 2001
  
  
  Duffy                   Expires July 2003                         4
  Internet Draft       Kerberos Ticket Control           January 2003
  
      [6] "PacketCable Architecture Framework Technical Report", PKT-
      TR-ARCH-V01-991201,
      http://www.packetcable.com/specifications.html
  
      [7] "PacketCable MTA Device Provisioning Specification", PKT-SP-
      PROV-I05-021127.  http://www.packetcable.com/specifications.html
  
   8.   Acknowledgments
  
      The author would like to acknowledge the effort of all those who
      contributed to the development of the PacketCable Provisioning
      specifications:
  
      Sumanth Channabasappa (Alopa Networks); Angela Lyda, Rick Morris,
      Rodney Osborne (Arris Interactive); Steven Bellovin and Chris
      Melle (AT&T); Eugene Nechamkin (Broadcom); John Berg, Maria
      Stachelek, Matt Osman (CableLabs); Klaus Hermanns, Azita Kia,
      Michael Thomas, Paul Duffy (Cisco); Deepak Patil (Com21); Jeff
      Ollis, Rick Vetter (General Instrument/Motorola); Roger Loots,
      David Walters (Lucent); Peter Bates (Telcordia); Patrick Meehan
      (Tellabs); Satish Kumar, Itay Sherman, Roy Spitzer (Telogy/TI),
      Aviv Goren (Terayon); Prithivraj Narayanan (Wipro), and Burcak
      Beser (Juniper Networks).
  
   9.   Author's Addresses
  
      Paul Duffy
      Cisco Systems
      300 Apollo Drive
      Chelmsford, MA, 01824
      Email: paduffy@cisco.com
  
   10.  Full Copyright Statement
  
      Copyright (C) The Internet Society (2003).  All Rights Reserved.
  
      This document and translations of it may be copied and furnished
      to others, and derivative works that comment on or otherwise
      explain it or assist in its implementation may be prepared,
      copied, published and distributed, in whole or in part, without
      restriction of any kind, provided that the above copyright notice
      and this paragraph are included on all such copies and derivative
      works.  However, this document itself may not be modified in any
      way, such as by removing the copyright notice or references to
  
  Duffy                   Expires July 2003                         5
  Internet Draft       Kerberos Ticket Control           January 2003
  
      the Internet Society or other Internet organizations, except as
      needed for the purpose of developing Internet standards in which
      case the procedures for copyrights defined in the Internet
      Standards process must be followed, or as required to translate
      it into languages other than English.
  
      The limited permissions granted above are perpetual and will not
      be revoked by the Internet Society or its successors or assigns.
  
      This document and the information contained herein is provided on
      an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
      ENGINEERING TASK FORCE DISCLAIMS 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.
  
   Acknowledgement
  
      Funding for the RFC Editor function is currently provided by the
      Internet Society.
  
  
  
  
  Duffy                   Expires July 2003                         6
  

Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/