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DHC Working Group                                                  L. Li
Internet-Draft                                                    Y. Cui
Intended status: Informational                                     J. Wu
Expires: June 18, 2016                               Tsinghua University
                                                                S. Jiang
                                            Huawei Technologies Co., Ltd
                                                       December 16, 2015


                        secure DHCPv6 deployment
                draft-li-dhc-secure-dhcpv6-deployment-02

Abstract

   Secure DHCPv6 provides authentication and encryption mechanisms for
   DHCPv6.  This draft analyses the DHCPv6 threat model and provides
   guideline for secure DHCPv6 deployment.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on June 18, 2016.

Copyright Notice

   Copyright (c) 2015 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
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as



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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  DHCPv6 threat model . . . . . . . . . . . . . . . . . . . . .   2
   3.  Secure DHCPv6 mechanism deployment  . . . . . . . . . . . . .   3
     3.1.  Secure DHCPv6 Overview  . . . . . . . . . . . . . . . . .   3
     3.2.  Secure DHCPv6 Deployment Difficulties . . . . . . . . . .   3
     3.3.  Scenario with Loose Security Policy . . . . . . . . . . .   3
     3.4.  Scenario with Strict Security Policy  . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Dynamic Host Configuration Protocol for IPv6 [RFC3315] enables
   DHCPv6 servers to configure network parameters dynamically.  Due to
   the unsecured nature of DHCPv6, the various critical identifiers in
   DHCPv6 are vulnerable to several types of attacks.  Secure DHCPv6
   [I-D.ietf-dhc-sedhcpv6] provides the authentication and encryption
   mechanisms for DHCPv6.

   This document analyses the DHCPv6 threat model and provides some
   guideline for secure DHCPv6 deployment.  For the secure DHCPv6
   deployment, we mainly consider two different scenarios: public coffee
   room with loose security policy and enterprise network with strict
   security policy.

2.  DHCPv6 threat model

   DHCPv6 privacy consideration [I-D.ietf-dhc-dhcpv6-privacy] analyses
   the privacy problem for DHCPv6, listing the various DHCPv6 options
   containing the privacy information and the possible attack to the
   DHCPv6.

   Most of the privacy considerations for DHCPv6 focus on the client
   privacy protection.  As the public service infrastructures, the
   privacy protection of DHCPv6 server and relay agent is less
   important.  The attack specific to a DHCPv6 client is the possibility
   of the injection attack, spoofing attack, and rogue server.  Because
   of the above attacks, the client may be configured with the incorrect
   configuration information, such as invalid IPv6 address.  In
   addition, the client is also faced up with passive attacks, such as
   pervasive monitoring.  Pervasive monitoring may glean the privacy



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   information of the IPv6 host, which is used to find location
   information, previously visited networks and so on.  [RFC7258] claims
   that pervasive monitoring should be mitigated in the design of IETF
   protocols, where possible.

   The attack specific to a DHCPv6 server is the possibility of "denial
   of service" (Dos) attack.  Invalid clients may masquerade as valid
   clients to request IPv6 addresses continually.  The attack may cause
   the exhaustion of valid IPv6 addresses, CPU and network bandwidth.
   In addition, it also causes problem for the maintenance and
   management of the large tables on the DHCPv6 servers.

3.  Secure DHCPv6 mechanism deployment

3.1.  Secure DHCPv6 Overview

   Secure DHCPv6 [I-D.ietf-dhc-sedhcpv6] provides the authentication and
   encryption mechanisms for DHCPv6.  The Information-request and Reply
   messages are exchanged to achieve the server authentication.  Then
   the DHCPv6 client authentication is achieved through the first
   message sent from client to server, which contains the client's
   certificate information.  Once the mutual authentication, the
   following DHCPv6 messages are all encrypted with the recipient's
   public key.

   The DHCPv6 server authentication protects the DHCPv6 client from
   injection attack, spoofing attack, and rogue server.  The DHCPv6
   client authentication protects the DHCPv6 server from Dos attack.
   The DHCPv6 encryption protects the DHCPv6 from passive attack, such
   as pervasive monitoring.

3.2.  Secure DHCPv6 Deployment Difficulties

   Because of the DHCPv6's specific property, the deployment of secure
   DHCPv6 mechanism faces some specific difficulties.  The DHCPv6 server
   is always assumed to have connectivity to authorized CA and able to
   verify the client's certificate.  The difficulty of deployment is
   that it is hard for the client to obtain itself certificate signed by
   CA or verify the server's identity without access to the network.
   According to the different DHCPv6 security requirement and the
   client's pre-configured information, different schemes for secure
   DHCPv6 deployment are used.

3.3.  Scenario with Loose Security Policy

   In the scenario where the security policy is loose, such as public
   coffee room, the opportunistic security policy plays a role.
   Opportunistic security provides DHCPv6 encryption even when the



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   mutual authentication is not available.

   In such scenario, the client is mobile and connects to random
   networks.  Based on the client's capability, the DHCPv6 configuration
   process is either authenticated and encrypted, or non-authenticated
   and encrypted.

   When the client is pre-configured with the certificate signed by CA
   and the information for server's identity verification, it has the
   capability to achieve the DHCPv6 client and server authentication.
   The DHCPv6 configuration process is authenticated and encrypted,
   which protects the DHCPv6 transaction from passive and active
   attacks.

   When the client is not pre-configured with the certificate signed by
   CA or the information for server's identify verification, the
   communication is non-authenticated and encrypted.  Non-authenticated
   and encrypted communication is better than cleartext, which defends
   against pervasive monitoring and other passive attacks.  Although the
   client is not capable of verifying the server's identity, the client
   can obtain the server's public key through the server's certificate.
   For the client authentication, the client can send the self-signed
   certificate to the server if the client is not configured with the
   certificate signed by CA.  For the DHCPv6 encryption, after the
   mutual public key communication process, the DHCPv6 message is
   encrypted with the recipient's public key.

3.4.  Scenario with Strict Security Policy

   In the scenario where the security policy is strict, such as
   enterprise network, the local default security policy is that the
   DHCPv6 configuration communication must be authenticated and
   encrypted.  Then the local security policy supersedes the
   opportunistic security policy.  Besides, the client is always stable
   terminal device, which is pre-configured with the trusted servers'
   certificates or the trusted CA certificates which forms the
   certificate path.  Through the pre-configured information, the client
   achieves the server authentication locally according to the rule
   defined in [RFC5280].  For the client authentication, the client
   sends the CA signed certificate to server for client authentication.
   For the DHCPv6 encryption, the DHCPv6 message is encrypted with the
   recipient's public key contained in the certificate.

   For the byod in enterprise network, the device is not pre-configured
   with the server authentication information to verify the server's
   identity.  In this case, the trusted server's certificate can be
   obtained out of band, such as QR code and other methods.  Out of band
   method is also suitable for the public coffee shops where the DHCPv6



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   client has strict security requirement.

4.  Security Considerations

   Opportunistic encryption is used for the secure DHCPv6 deployment in
   the scenario where the security policy is loose.  The DHCPv6
   configuration process is non-authenticated but encryption if the
   client is not pre-configured with the trusted servers' certificates
   or trusted CAs' certificates.  Downgrade attacks cannot be avoided if
   the client is set the local policy that the DHCPv6 configuration
   process must be authenticated and encrypted.

5.  References

5.1.  Normative References

   [I-D.ietf-dhc-sedhcpv6]
              Jiang, S., Li, L., Cui, Y., Jinmei, T., Lemon, T., and D.
              Zhang, "Secure DHCPv6", draft-ietf-dhc-sedhcpv6-10 (work
              in progress), December 2015.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <http://www.rfc-editor.org/info/rfc7435>.

5.2.  Informative References

   [I-D.ietf-dhc-dhcpv6-privacy]
              Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
              considerations for DHCPv6", draft-ietf-dhc-
              dhcpv6-privacy-01 (work in progress), August 2015.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <http://www.rfc-editor.org/info/rfc7258>.





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Authors' Addresses

   Lishan Li
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-15201441862
   Email: lilishan9248@126.com


   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6260-3059
   Email: yong@csnet1.cs.tsinghua.edu.cn


   Jianping Wu
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6278-5983
   Email: jianping@cernet.edu.cn


   Sheng Jiang
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   CN

   Email: jiangsheng@huawei.com















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