draft-ietf-dhc-pktc-kerb-tckt-03.txt   rfc3594.txt 
Internet Engineering Task Force P. Duffy Network Working Group P. Duffy
INTERNET DRAFT Cisco Systems Request for Comments: 3594 Cisco Systems
DHC Working Group June 2003 Category: Standards Track September 2003
Document: draft-ietf-dhc-pktc-kerb-tckt-03.txt
PacketCable Security Ticket Control Sub-option PacketCable Security Ticket Control Sub-Option
for the DHCP CableLabs Client Configuration Option. for the DHCP CableLabs Client Configuration (CCC) Option
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance This document specifies an Internet standards track protocol for the
with all provisions of Section 10 of RFC 2026. Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document defines a new sub-option for the DHCP CableLabs This document defines a new sub-option for the DHCP CableLabs Client
Client Configuration (CCC) Option. This new sub-option will be Configuration (CCC) Option. This new sub-option will be used to
used to direct CableLabs Client Devices (CCDs) to invalidate direct CableLabs Client Devices (CCDs) to invalidate security tickets
security tickets stored in CCD non volatile memory (i.e. locally stored in CCD non volatile memory (i.e., locally persisted security
persisted security tickets). tickets).
1. Conventions used in this document 1. Conventions used in this document
Duffy 1 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and document are to be interpreted as described in BCP 14, RFC 2119 [2].
"OPTIONAL" in this document are to be interpreted as described in
RFC 2119 [2].
2. Terminology 2. Terminology
Definitions of terms/acronyms used throughout this document: Definitions of terms/acronyms used throughout this document:
CCC - CableLabs Client Configuration option, described in [1]. CCC - CableLabs Client Configuration option, described in [1].
CCD - CableLabs Client Device. A PacketCable MTA is an example CCD - CableLabs Client Device. A PacketCable MTA is an example of a
of a CCD. CCD.
STC - Security Ticket Control. The CCC sub-option described in STC - Security Ticket Control. The CCC sub-option described in this
this document. document.
MTA - Media Terminal Adapter. The CCD specific to the PacketCable MTA - Media Terminal Adapter. The CCD specific to the PacketCable
architecture. architecture.
PacketCable - multimedia architecture developed by CableLabs. See PacketCable - multimedia architecture developed by CableLabs. See
[8] for full details. [8] for full details.
3. Introduction 3. Introduction
The CableLabs Client Configuration Option [1] defines several sub- The CableLabs Client Configuration Option [1] defines several
options used to configure devices deployed into CableLabs sub-options used to configure devices deployed into CableLabs
architectures. These architectures implement the PacketCable architectures. These architectures implement the PacketCable
Security Specification [4] (based on Kerberos V5 [5]), to Security Specification [4] (based on Kerberos V5 [5]), to support CCD
support CCD authentication and establishment of security authentication and establishment of security associations between
associations between CCDs and application servers. CCDs and application servers.
CCDs are permitted to retain security tickets in local CCDs are permitted to retain security tickets in local persistent
persistent storage. Thus a power-cycled CCD is enabled to avoid storage. Thus a power-cycled CCD is enabled to avoid expensive
expensive ticket acquisition for locally persisted, non-expired ticket acquisition for locally persisted, non-expired tickets. This
tickets. This feature greatly reduces the security overhead of feature greatly reduces the security overhead of a deployment.
a deployment.
This sub-option allows the service provider to control the This sub-option allows the service provider to control the lifetime
lifetime of tickets persisted locally on a CCD. The service of tickets persisted locally on a CCD. The service provider requires
provider requires this capability to support operational this capability to support operational functions such as forcing re-
functions such as forcing re-establishment of security establishment of security associations, remote testing, and remote
associations, remote testing, and remote diagnostic of CCDs. diagnostic of CCDs.
Duffy Expires December 2003 2 It should be noted that, although based on the Kerberos V5 RFC [5],
It should be noted that, although based on the Kerberos V5 RFC the PacketCable Security Specification is not a strict implementation
[5], the PacketCable Security Specification is not a strict of this RFC. See [4] for details of the PacketCable Security
implementation of this RFC. See [4] for details of the Specification.
PacketCable Security Specification.
4. Security Ticket Control Sub-option 4. Security Ticket Control Sub-option
This sub-option defines a Ticket Control Mask (TCM) that This sub-option defines a Ticket Control Mask (TCM) that instructs
instructs the CCD to validate/invalidate specific application the CCD to validate/invalidate specific application server tickets.
server tickets. The sub-option is encoded as follows: The sub-option is encoded as follows:
Code Len TCM Code Len TCM
+-----+-----+-----+-----+ +-----+-----+-----+-----+
| TBD | 2 | m1 | m2 | | 9 | 2 | m1 | m2 |
+-----+-----+-----+-----+ +-----+-----+-----+-----+
The length MUST be 2. The TCM field is encoded as an unsigned 16 The length MUST be 2. The TCM field is encoded as an unsigned 16 bit
bit quantity per network byte order. Each bit of the TCM is quantity per network byte order. Each bit of the TCM is assigned to
assigned to a specific server or server group. A bit value of 0 a specific server or server group. A bit value of 0 means the CCD
means the CCD MUST apply normal invalidation rules (defined in MUST apply normal invalidation rules (defined in [4]) to the locally
[4]) to the locally persisted ticket for the server/server group. persisted ticket for the server/server group. A bit value of 1 means
A bit value of 1 means the CCD MUST immediately invalidate the the CCD MUST immediately invalidate the locally persisted ticket for
locally persisted ticket for the server/server group. the server/server group.
Bit #0 is the least significant bit of the field. The bit Bit #0 is the least significant bit of the field. The bit positions
positions are assigned as follows. are assigned as follows:
Bit #0 - the PacketCable Provisioning Server used by the CCD. Bit #0 - the PacketCable Provisioning Server used by the CCD.
Bit #1 - the group of all PacketCable Call Management Servers Bit #1 - the group of all PacketCable Call Management Servers used
used by the CCD. by the CCD.
Bit #2 - #15. Reserved and MUST be set to 0. Bit #2 - #15. Reserved and MUST be set to 0.
If a CCD does not locally store tickets, it MUST ignore this sub- If a CCD does not locally store tickets, it MUST ignore this
option. Bit values not known to the CCD MUST be ignored. sub-option. Bit values not known to the CCD MUST be ignored.
5. IANA Considerations 5. IANA Considerations
IANA is requested to assign a sub-option code to this sub-option IANA has assigned a sub-option code to this sub-option from the
from the "CableLabs Client Configuration" sub-option number space "CableLabs Client Configuration" sub-option number space (maintained
(maintained within the BOOTP-DHCP Parameters Registry). within the BOOTP-DHCP Parameters Registry).
Duffy Expires December 2003 3 IANA has also set-up a new registry and will maintain a new number
IANA is also requested to maintain a new number space of space of "CableLabs Client Configuration Option Ticket Control Mask
"CableLabs Client Configuration Option Ticket Control Mask Bit Bit Definitions", located in the BOOTP-DHCP Parameters Registry. The
Definitions", located in the BOOTP-DHCP Parameters Registry. The initial bit definitions are described in section 4 of this document.
initial bit definitions are described in section 4 of this IANA will register future bit mask definitions via an "IETF
document. IANA is requested to register future bit mask Consensus" approval policy as described in RFC 2434 [3].
definitions via an "IETF Consensus" approval policy as described
in RFC 2434 [3].
6. Security Considerations 6. Security Considerations
Potential DHCP protocol attack exposure is discussed in section 7 Potential DHCP protocol attack exposure is discussed in section 7 of
of the DHCP protocol specification [6] and in Authentication for the DHCP protocol specification [6] and in Authentication for DHCP
DHCP Messages [7]. Additional CCC attack exposure is discussed Messages [7]. Additional CCC attack exposure is discussed in [1].
in [1].
The STC sub-option could be used to disrupt a CableLabs The STC sub-option could be used to disrupt a CableLabs architecture
architecture deployment. In the specific case of PacketCable deployment. In the specific case of PacketCable [8], a deployment
[8], a deployment could be disrupted if a large number of MTAs could be disrupted if a large number of MTAs are reset/power cycled,
are reset/power cycled, initiate their provisioning flow [9], and initiate their provisioning flow [9], and are instructed by a
are instructed by a malicious DHCP server to invalidate all malicious DHCP server to invalidate all security tickets. This could
security tickets. This could lead to a Denial of Service (DoS) lead to a Denial of Service (DoS) condition as this large set of MTAs
condition as this large set of MTAs simultaneously attempt to simultaneously attempt to authenticate and obtain tickets from the
authenticate and obtain tickets from the security infrastructure. security infrastructure.
However, the scenario described above is unlikely to occur. However, the scenario described above is unlikely to occur. Within
Within the cable delivery architecture required by the various the cable delivery architecture required by the various CableLabs
CableLabs projects, the DHCP client is connected to a network projects, the DHCP client is connected to a network through a cable
through a cable modem and the CMTS (head-end router). The CMTS is modem and the CMTS (head-end router). The CMTS is explicitly
explicitly configured with a set of valid DHCP server addresses configured with a set of valid DHCP server addresses to which DHCP
to which DHCP requests are forwarded. Further, a correctly requests are forwarded. Further, a correctly configured CMTS will
configured CMTS will only allow DHCP downstream traffic from only allow DHCP downstream traffic from specific DHCP server
specific DHCP server addresses. addresses.
It should be noted that the downstream filtering of DHCP packets It should be noted that the downstream filtering of DHCP packets will
will not prevent spoofed DHCP servers behind the CMTS, but the not prevent spoofed DHCP servers behind the CMTS, but the network
network infrastructure behind the CMTS is assumed to be closely infrastructure behind the CMTS is assumed to be closely controlled by
controlled by the service provider. the service provider.
7. References 7. Intellectual Property Statement
7.1. Normative The IETF takes no position regarding the validity or scope of any
intellectual property 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; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
Duffy Expires December 2003 4 The IETF invites any interested party to bring to its attention any
[1] B. Beser and P. Duffy, "DHCP Option for CableLabs Client copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
8. References
8.1. Normative
[1] Beser, B. and P. Duffy, "DHCP Option for CableLabs Client
Configuration", RFC 3495, March 2003. Configuration", RFC 3495, March 2003.
[2] S. Bradner, "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[3] T. Narten and H. Alvestrand, "Guidelines for Writing an IANA [3] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998. Considerations Section in RFCs", RFC 2434, October 1998.
[4] "PacketCable Security Specification", PKT-SP-SEC-I08-030415, [4] "PacketCable Security Specification", PKT-SP-SEC-I09-030728,
http://www.packetcable.com/specifications.html http://www.packetcable.com/downloads/specs/
PKT-SP-SEC-I09-030728.pdf
7.2. Informational 8.2. Informative
[5] J. Kohl and C. Neuman, "The Kerberos Network Authentication [5] Kohl, J. and C. Neuman, "The Kerberos Network Authentication
Service (V5)", RFC 1510, September 1993. Service (V5)", RFC 1510, September 1993.
[6] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131, [6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March
March 1997. 1997.
[7] R. Droms and W. Arbaugh, "Authentication for DHCP Messages", [7] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC
RFC 3118, June 2001 3118, June 2001
[8] "PacketCable Architecture Framework Technical Report", PKT- [8] "PacketCable 1.0 Architecture Framework Technical Report",
TR-ARCH-V01-991201, PKT-TR-ARCH-V01-991201,
http://www.packetcable.com/specifications.html http://www.packetcable.com/downloads/specs/
pkt-tr-arch-v01-991201.pdf
[9] "PacketCable MTA Device Provisioning Specification", PKT-SP- [9] "PacketCable MTA Device Provisioning Specification",
PROV-I06-030415. http://www.packetcable.com/specifications.html PKT-SP-PROV-I07-030728,
http://www.packetcable.com/downloads/specs/
PKT-SP-PROV-I07-030728.pdf
8. Acknowledgments 9. Acknowledgments
The author would like to acknowledge the effort of all those who The author would like to acknowledge the effort of all those who
contributed to the development of the PacketCable Provisioning contributed to the development of the PacketCable Provisioning
specifications: specifications:
Sumanth Channabasappa (Alopa Networks); Angela Lyda, Rick Morris, Sumanth Channabasappa (Alopa Networks); Angela Lyda, Rick Morris,
Rodney Osborne (Arris Interactive); Steven Bellovin and Chris Rodney Osborne (Arris Interactive); Steven Bellovin and Chris
Melle (AT&T); Eugene Nechamkin (Broadcom); John Berg, Maria Melle (AT&T); Eugene Nechamkin (Broadcom); John Berg, Maria
Stachelek, Matt Osman, Venkatesh Sunkad (CableLabs); Klaus Stachelek, Matt Osman, Venkatesh Sunkad (CableLabs); Klaus
Hermanns, Azita Kia, Michael Thomas, Paul Duffy (Cisco); Deepak Hermanns, Azita Kia, Michael Thomas, Paul Duffy (Cisco); Deepak
Patil (Com21); Jeff Ollis, Rick Vetter (General Patil (Com21); Jeff Ollis, Rick Vetter (General
Instrument/Motorola); Roger Loots, David Walters (Lucent); Peter Instrument/Motorola); Roger Loots, David Walters (Lucent); Peter
Duffy Expires December 2003 5
Bates (Telcordia); Patrick Meehan (Tellabs); Satish Kumar, Itay Bates (Telcordia); Patrick Meehan (Tellabs); Satish Kumar, Itay
Sherman, Roy Spitzer (Telogy/TI), Aviv Goren (Terayon); Sherman, Roy Spitzer (Telogy/TI), Aviv Goren (Terayon);
Prithivraj Narayanan (Wipro), and Burcak Beser (Juniper Prithivraj Narayanan (Wipro), and Burcak Beser (Juniper
Networks). Networks).
9. Author's Addresses 10. Author's Address
Paul Duffy Paul Duffy
Cisco Systems Cisco Systems
300 Apollo Drive 1414 Massachusetts Avenue
Chelmsford, MA, 01824 Boxborough, MA 01719
Email: paduffy@cisco.com
10. Full Copyright Statement EMail: paduffy@cisco.com
11. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
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Duffy Expires December 2003 6
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
Duffy Expires December 2003 7
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