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DHC Working Group L. Li
Internet-Draft Y. Cui
Intended status: Informational J. Wu
Expires: September 7, 2016 Tsinghua University
S. Jiang
Huawei Technologies Co., Ltd
March 6, 2016


secure DHCPv6 deployment
draft-li-dhc-secure-dhcpv6-deployment-03

Abstract

Secure DHCPv6 provides authentication and encryption mechanisms for
DHCPv6. This draft analyses 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
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This Internet-Draft will expire on September 7, 2016.

Copyright Notice

Copyright (c) 2016 IETF Trust and the persons identified as the
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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 . . . . . . . . . . 4
3.3. Roaming Client with Loose Security Policy . . . . . . . . 4
3.4. Static Client with Strict Security Policy . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 6
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 authentication and encryption
mechanisms for DHCPv6.

This document analyses DHCPv6 threat model and provides some
guideline for secure DHCPv6 deployment. For secure DHCPv6
deployment, we mainly consider two different scenarios: roaming
client with loose security policy and static client 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 attacks to
DHCPv6.

Most of the privacy considerations for DHCPv6 focus on the client
privacy protection. As the public service infrastructures, the
privacy protection of the DHCPv6 server and relay agent is less
important.

The attack specific to a DHCPv6 client is the possibility of the
injection attack, MitM attack, spoofing attack. Because of the above
attacks, the client may be configured with the incorrect
configuration information, such as invalid IPv6 address. In



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addition, the client is also faced up with passive attacks, such as
pervasive monitoring. Pervasive monitoring may glean the privacy
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.

For the static clients, such as the devices in enterprise network,
they are always assumed to connect to exactly one network. The
static client can be easily pre-configured with the certificates of
the local DHCPv6 servers. According to the pre-configured
information, the static client can detect the spoofing attack. The
typical attack is MitM attack. An intruder connects to the network
and uses DHCP spoofing to install itself as a MitM. Because of the
MitM attack, the client's privacy information may be modified or
gleaned by the MitM. For the roaming clients, the typical attack is
spoofing attack. Because of the rogue server which masquerades as
valid server, the client is configured with the incorrect
configuration information.

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 DHCPv6 server authentication. Then
the DHCPv6 client authentication is achieved through the first
encrypted DHCPv6 message sent from the client to the server, which
contains the client's certificate information. Once the mutual
authentication, the subsequent DHCPv6 messages are all encrypted with
the recipient's public key.

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






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3.2. Secure DHCPv6 Deployment Difficulties

Because of DHCPv6's specific property, the deployment of Secure
DHCPv6 mechanism is faced with some specific difficulties. The
DHCPv6 server is always assumed to be pre-configured with the trusted
clients' certificates or the trusted CAs' certificates to verify the
clients' identity. The difficulty of Secure DHCPv6 deployment is
that it is hard for the client to verify the server's identity
without access to the network. According to the client's capability
and security requirement, different schemes for secure DHCPv6
deployment are applied.

3.3. Roaming Client with Loose Security Policy

In the scenario where the DHCPv6 clients are roaming and have loose
security requirement, opportunistic security plays a role.
Opportunistic security provides DHCPv6 encryption even when the
mutual authentication is not available. Based on the roaming
client's capability, the DHCPv6 configuration process is either
authenticated and encrypted, or non-authenticated and encrypted.

If the client is pre-configured with the trusted servers'
certificates or the trusted CAs' certificates, it has the capability
to achieve server authentication. If the client is pre-configured
with its own CA-signed certificate, it sends the CA-signed
certificate to the DHCPv6 server for client authentication. When the
client has been pre-configured with these certificate information,
the DHCPv6 configuration process is authenticated and encrypted,
which protects the DHCPv6 transaction from passive and active
attacks.

If the client is not pre-configured with these certificate
information, 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 CA-signed certificate. For the
DHCPv6 encryption, after the mutual public key communication process,
the DHCPv6 message is encrypted with the recipient's public key.

3.4. Static Client with Strict Security Policy

In the scenario where the DHCPv6 clients are static and have strict
security requirement, the PKI plays a role. Then the default
security policy is that DHCPv6 configuration communication must be



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authenticated and encrypted. The static clients, such as the desktop
in enterprise network, are pre-configured with the trusted servers'
certificates or the trusted CAs' certificates which form the
certificate path. Through the pre-configured information, the client
has the capability to achieve server authentication locally according
to the rule defined in [RFC5280]. For client authentication, the
client sends the CA-signed certificate to the server for client
authentication. For DHCPv6 encryption, the DHCPv6 message is
encrypted with the recipient's public key contained in the
certificate.

In some scenarios, the roaming client may also have strict security
requirement, such as the byod in enterprise network. Because of the
strict security policy, the DHCPv6 configuration process is
authenticated and encrypted. Although the roaming client is not pre-
configured with the certificates information, the trusted server's
certificate and its own certificate can be obtained out of band, such
as by scanning a QR code. Through the obtained certificate
information, the DHCPv6 client and the DHCPv6 server can achieve the
mutual authentication. And then the subsequent DHCPv6 messages are
encrypted with the recipient's public key.

4. Security Considerations

Opportunistic encryption is used for secure DHCPv6 deployment in the
scenario where the security policy is loose. Downgrade attacks
cannot be avoided if nodes can accept the un-authenticated and
encrypted DHCPv6 configuration.

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, .

[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,
.



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[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, .

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-05 (work in progress), February 2016.

[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, .

Authors' Addresses

Lishan Li
Tsinghua University
Beijing 100084
P.R.China

Phone: +86-15201441862
Email: lilishan48@gmail.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









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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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