Network Working Group Sheng Jiang
Sean Shen
Internet Draft Huawei Technologies Co., Ltd
Expires: April 2009 October 27th, 2008
DHCPv6 and CGA Interaction: Problem Statement
draft-jiang-csi-dhcpv6-cga-ps-00.txt
Status of this Memo
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
becomes aware will be disclosed, in accordance with Section 6 of
BCP 79.
This document may only be posted in an Internet-Draft.
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 April 25, 2009.
Abstract
This document presents a problem statement for the possible
interactions between DHCPv6 and CGA. Firstly, in order to support the
co-existing scenarios of DHCPv6 and CGA, Some operations are
clarified for the interaction of DHCPv6 servers and CGA-associated
hosts. Then, some extended scenarios are also discussed in this
document, including using CGAs in DHCPv6 operations to enhance the
security features and using DHCPv6 to serve the CGA generation.
Jiang & Shen Expires April 25, 2009 [Page 1]
Internet-Draft draft-jiang-csi-dhcpv6-cga-ps-00.txt October 2008
Table of Contents
1. Introduction................................................2
2. Terminology.................................................2
3. Co-existing of DHCPv6 and CGA................................3
4. What DHCPv6 can do for CGA...................................3
5. What CGA can do for DHCPv6...................................4
6. Security Considerations......................................5
7. IANA Considerations.........................................5
8. References..................................................5
8.1. Normative References....................................5
8.2. Informative References..................................5
Author's Addresses.............................................6
Intellectual Property Statement.................................6
Disclaimer of Validity.........................................7
Copyright Statement............................................7
1. Introduction
Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315] can
assign addresses statefully. Although there are other ways to assign
IPv6 address [RFC4339], DHCPv6 is still useful when administrator
desire more control over addressing. Besides, DHCPv6 also be used to
distribute other information when dialog state is critical [RFC4242].
Cryptographically Generated Addresses (CGA) [RFC3972] are IPv6
addresses for which the interface identifiers are generated by
computing a cryptographic one-way hash function from a public key and
auxiliary parameters. By using the associate public & private keys as
described in SEcure Neighbor Discovery (SEND) [RFC3971], CGA can
protect Neighbor Discovery Protocol (NDP) [RFC4861], i.e. it provides
address validation and integrity protection for NDP messages.
This document presents a problem statement for the possible
interactions between DHCPv6 and CGA. Firstly, in order to support the
co-existing scenarios of DHCPv6 and CGA, Some operations are
clarified for the interaction of DHCPv6 servers and CGA-associated
hosts. Then, some extended scenarios are also discussed in this
document, including using CGAs in DHCPv6 operations to enhance the
security features and using DHCPv6 to serve the CGA generation.
2. Terminology
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].
Jiang & Shen Expires April 25, 2009 [Page 2]
Internet-Draft draft-jiang-csi-dhcpv6-cga-ps-00.txt October 2008
3. Co-existing of DHCPv6 and CGA
As an important IPv6 technique, CGA is used efficiently on the
stateless address configuration of IPv6 address. The public key
system associated with CGA address provides message origin validation
and integrity protection without negotiation and transportation of
key materials. {more}
The current CGA specifications does not mandate which device
generates a CGA address. In many cases, a CGA address is generated by
the associated key pair owner, which normally is also the host that
will use the CGA address.
However, in a DHCPv6-managed network, hosts should obtain IPv6
addresses only from a DHCPv6 server. This difference of roles needs
to be carefully considered during the interaction of CGA and DHCPv6.
Operations, as clarified in the next paragraph, support the co-
existing of CGA's host self-generate address mechanism and DHCPv6
managed address mechanism.
This can be solved by validation procedure, which has been defined in
the current DHCPv6. A node requests DHCPv6 server to grant a CGA
generated by the node itself, listing the CGA addresses in IA options,
which has been defined in [RFC3315]. According to whether the CGA
matches the CGA-related configuration parameters of the network, the
DHCPv6 server sends an acknowledgement to the node, grant the usage
of the CGA or indicate the node that it must generate a new CGA with
the CGA-related configuration parameters of the network. In the
meantime, the DHCPv6 server has had the opportunity to log the
address/host combination.
4. What DHCPv6 can do for CGA
In the current CGA specifications, there is a lack of procedures to
enable proper management of CGA generation. Administrators should be
able to configure parameters used to generate CGA. For example,
DHCPv6 server should be able to assign subnet prefix or certificates
to CGA address owner. In some scenarios, the administrator may
further want to enforce some parameters, particularly, the demanded
security related parameters such as SEC value.
In the CGA generation procedure, the large computational consumption
is needed to generate the Modifier field. This CPU intensive
operation can represent time and/or battery consumption problems for
Jiang & Shen Expires April 25, 2009 [Page 3]
Internet-Draft draft-jiang-csi-dhcpv6-cga-ps-00.txt October 2008
end hosts (i.e. mobile devices) with limited computing ability and/or
restricted battery power. In these cases, a mechanism to delegate the
computation of the modifier should be provided.
DHCPv6 can help on these issues by providing more relevant functions.
New DHCPv6 options may be defined to carry management parameters from
DHCPv6 server to the client. A new DHCPv6 prefix assignment option
may be define to propagate a subnet prefix. More DHCPv6 options may
be defined to propagate more CGA-relevant configuration information,
such as SEC value, certification information, SEND proxy information,
etc.
New interaction behavior between DHCPv6 server and client with a set
of new DHCPv6 options may be defined to allow computation delegation.
A node may initiate a DHCPv6 request to the DHCPv6 server for the
computation of the Modifier. The server either computes the Modifier
value, or redirects the computation require to another server. Once
the server obtains the modifier, it computes the CGA and responds to
the node with the resulting address and the corresponding CGA
Parameters Data Structure.
5. What CGA can do for DHCPv6
DHCPv6 is vulnerable to various attacks particularly fake attack. In
the basic DHCPv6 specifications, regular IPv6 addresses are used. It
is possible for a malicious attacker to use a fake address to spoof
or launch an attack. A malicious fake DHCPv6 server can provide
incorrect configuration to the client in order to divert the client
to communicate with malicious services, like DNS or NTP. It may also
mount a denial of service attack through mis-configuration of the
client that causes all network communication from the client to fail.
Fake DHCPv6 server may also collect some critical information from
the client. Attackers may be able to gain unauthorized access to some
resources, such as network access.
The usage of CGA can efficiently improve the security of DHCPv6. Thus
the address of a DHCP message sender, which can be a DHCP server, a
reply agent or a client, can be verified by a receiver. It improves
communication security of DHCPv6 interaction. This mechanism is
applicable in environments where physical security on the link is not
assured (such as over wireless) or where available security
mechanisms are not sufficient, and attacks on DHCPv6 are a concern.
Of course, as an assumption, the advantage of CGA can be taken only
when CGA addresses are used in DHCPv6 communications.
Jiang & Shen Expires April 25, 2009 [Page 4]
Internet-Draft draft-jiang-csi-dhcpv6-cga-ps-00.txt October 2008
6. Security Considerations
This whole draft is discussing security relevant problems. CGA and
DHCPv6 can provide additional service or security features for each
other. The IPv6 protocols can take advantages of each other when they
coexist online.
7. IANA Considerations
There are no IANA considerations in this document.
8. References
8.1. Normative References
[RFC2462] S. Thomson, T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC2462, December 1998.
[RFC3315] R. Droms, et al., "Dynamic Host Configure Protocol for
IPv6", RFC3315, July 2003.
[RFC3971] J. Arkko, J. Kempf, B. Zill, P. Nikander, "SEcure Neighbor
Discovery (SEND) ", RFC 3971, March 2005.
[RFC3972] T. Aura, "Cryptographically Generated Address", RFC3972,
March 2005.
[RFC4242] S. Venaas, T. Chown, B. Volz, "Information Refresh Time
Option for Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC4242, November 2005.
[RFC4339] J. Jeong, Ed., "IPv6 Host Configuration of DNS Server
Information Approaches", RFC4339, February 2006.
[RFC4861] T. Narten, E. Nordmark, W. Simpson, H. Soliman, "Neighbor
Discovery for IP version 6 (IPv6)", RFC4861, September 2007.
8.2. Informative References
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC2119, March 1997.
Jiang & Shen Expires April 25, 2009 [Page 5]
Internet-Draft draft-jiang-csi-dhcpv6-cga-ps-00.txt October 2008
Author's Addresses
Sheng Jiang
Huawei Technologies
QuiKe Bld., No.6 Rd, Xinxi St.,
Shang-Di Information Industry Base,
Hai-Dian District, Beijing, P.R. China
100085
Phone: 86-10-82836774
Email: shengjiang@huawei.com
Sean Shen
Huawei Technologies Co., Ltd
QuiKe Building, No.9 Xinxi Rd.,
Shang-Di Information Industry Base,
Hai-Dian District, Beijing, P.R. China
100085
Phone: 86-10-82836072
Email: sshen@huawei.com
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. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Jiang & Shen Expires April 25, 2009 [Page 6]
Internet-Draft draft-jiang-csi-dhcpv6-cga-ps-00.txt October 2008
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, THE IETF TRUST 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 IETF Trust (2008).
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.
Jiang & Shen Expires April 25, 2009 [Page 7]