DHC Working Group S. Jiang
Internet-Draft Huawei Technologies Co., Ltd
Intended status: Standards Track L. Li
Expires: January 9, 2017 Y. Cui
Tsinghua University
T. Jinmei
Infoblox Inc.
T. Lemon
Nominum, Inc.
D. Zhang
July 8, 2016
Secure DHCPv6
draft-ietf-dhc-sedhcpv6-13
Abstract
DHCPv6 includes no deployable security mechanism that can protect
end-to-end communication between DHCP clients and servers. This memo
describes a mechanism for using public key cryptography to provide
such security. The mechanism provides encryption in all cases, and
can be used for authentication based either on pre-sharing of
authorized certificates, or else using trust-on-first-use.
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 January 9, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language and Terminology . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Issues of DHCPv6 . . . . . . . . . . . . . . . . . . 4
5. Secure DHCPv6 Overview . . . . . . . . . . . . . . . . . . . 5
5.1. Solution Overview . . . . . . . . . . . . . . . . . . . . 5
5.2. New Components . . . . . . . . . . . . . . . . . . . . . 6
5.3. Support for Algorithm Agility . . . . . . . . . . . . . . 6
5.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 7
6. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . 8
7. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . 11
8. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . 13
9. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 14
9.1. New DHCPv6 Options . . . . . . . . . . . . . . . . . . . 14
9.1.1. Certificate Option . . . . . . . . . . . . . . . . . 14
9.1.2. Signature option . . . . . . . . . . . . . . . . . . 15
9.1.3. Increasing-number Option . . . . . . . . . . . . . . 17
9.1.4. Encrypted-message Option . . . . . . . . . . . . . . 17
9.2. New DHCPv6 Messages . . . . . . . . . . . . . . . . . . . 18
9.3. Status Codes . . . . . . . . . . . . . . . . . . . . . . 18
10. Security Considerations . . . . . . . . . . . . . . . . . . . 19
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
13. Change log [RFC Editor: Please remove] . . . . . . . . . . . 21
14. Open Issues [RFC Editor: Please remove] . . . . . . . . . . . 23
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
15.1. Normative References . . . . . . . . . . . . . . . . . . 23
15.2. Informative References . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315])
allows DHCPv6 servers to flexibly provide addressing and other
configuration information relating to local network infrastructure to
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DHCP clients. The protocol provides no deployable security
mechanism, and consequently is vulnerable to various attacks.
This document provides a brief summary of the security
vulnerabilities of the DHCPv6 protocol and then describes a new
extension to the protocol that provides two additional types of
security:
o authentication of the DHCPv6 client and the DHCPv6 server to
defend against active attacks, such as spoofing.
o encryption between the DHCPv6 client and the DHCPv6 server in
order to protect the DHCPv6 from pervasive monitoring.
The extension specified in this document applies only to end-to-end
communication between DHCP servers and clients. Options added by
relay agents in Relay-Forward messages, and options other than the
client message in Relay-Reply messages sent by DHCP servers, are not
protected. Such communications are already protected using the
mechanism described described in section 21.1 in [RFC3315].
This extension introduces two new DHCPv6 messages: the Encrypted-
Query and the Encrypted-Response messages. It defines four new
DHCPv6 options: the Certificate, the Signature, the Increasing-
number, and the Encrypted-message options. The Certificate,
Signature, and Increasing-number options are used for authentication.
The Encryption-Query message, Encryption-Response message and
Encrypted-message option are used for encryption.
2. Requirements Language and 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 [RFC2119] when they
appear in ALL CAPS. When these words are not in ALL CAPS (such as
"should" or "Should"), they have their usual English meanings, and
are not to be interpreted as [RFC2119] key words.
3. Terminology
This section defines terminology specific to secure DHCPv6 used in
this document.
secure DHCPv6 client: A node that initiates a DHCPv6 request on a
link to obtain DHCPv6 configuration parameters from
one or more DHCPv6 servers using the encryption and
optional authentication mechanisms defined in this
document.
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secure DHCPv6 server: A DHCPv6 server that implements the
authentication and encryption mechanisms defined in
this document, and is configured to use them.
4. Security Issues of DHCPv6
[RFC3315] defines an authentication mechanism with integrity
protection. This mechanism uses a symmetric key that is shared by
the client and server for authentication. It does not provide any
key distribution mechanism.
For this approach, operators can set up a key database for both
servers and clients from which the client obtains a key before
running DHCPv6. However, manual key distribution runs counter to the
goal of minimizing the configuration data needed at each host.
Consequently, there are no known deployments of this security
mechanism.
[RFC3315] provides an additional mechanism for preventing off-network
timing attacks using the Reconfigure message: the Reconfigure Key
authentication method. However, this method protects only the
Reconfigure message. The key is transmitted in plaintext to the
client in earlier exchanges and so this method is vulnerable to on-
path active attacks.
Anonymity Profile for DHCP Clients [RFC7844] explains how to generate
DHCPv4 or DHCPv6 requests that minimize the disclosure of identifying
information. However, the anonymity profile limits the use of the
certain options. It also cannot anticipate new options that may
contain private information is defined. In addition, the anonymity
profile does not work in cases where the client wants to maintain
anonymity from eavesdroppers but must identify itself to the DHCP
server with which it intends to communicate.
Privacy consideration for DHCPv6 [RFC7824] presents an analysis of
the privacy issues associated with the use of DHCPv6 by Internet
users. No solutions are presented.
Current DHCPv6 messages are still transmitted in cleartext and the
privacy information within the DHCPv6 message is not protected from
passive attack, such as pervasive monitoring [RFC7258].
To better address the problem of passive monitoring and to achieve
authentication without requiring a symmetric key distribution
solution for DHCP, this document defines an asymmetric key
authentication and encryption mechanism. This protects against both
active attacks, such as spoofing, and passive attacks, such as
pervasive monitoring.
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5. Secure DHCPv6 Overview
5.1. Solution Overview
The following figure illustrated secure DHCPv6 procedure. Briefly,
this extension establishes the server's identity with an anonymous
Information-Request exchange. Once the server's identity has been
established, the client may either choose to communicate with the
server or not. Not communicating with an unknown server avoids
revealing private information, but if there is no known server on a
particular link, the client will be unable to communicate with a DHCP
server.
If the client chooses to communicate with a server, it uses the
Encrypted-Query message to encapsulate its communications to the DHCP
server. The server responds with Encrypted-Response messages.
Normal DHCP messages are encapsulated in these two new messages using
the new defined Encrypted-message option. Besides the Encrypted-
message option, the Signature option is defined to verify the
integrity of the DHCPv6 messages and then authentication of client
and server. The Increasing number is defined to detect replay
attack.
+-------------+ +-------------+
|DHCPv6 Client| |DHCPv6 Server|
+-------------+ +-------------+
| Information-request |
|----------------------------------------->|
| Option Request option |
| |
| Reply |
|<-----------------------------------------|
| Certificate option |
| Signature option |
| Increasing-number option |
| Server Identifier option |
| |
| Encryption-Query |
|----------------------------------------->|
| Encrypted-message option |
| Server Identifier option |
| |
| Encryption-Response |
|<-----------------------------------------|
| Encrypted-message option |
| |
Secure DHCPv6 Procedure
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5.2. New Components
The new components of the mechanism specified in this document are as
follows:
o Servers and clients that use certificates first generate a public/
private key pair and then obtain a certificate that signs the
public key. The Certificate option is defined to carry the
certificate of the sender.
o A signature generated using the private key which is used by the
receiver to verify the integrity of the DHCPv6 messages and then
authentication of the client/server. The Signature option is
defined to carry the signature.
o A Increasing-number that can be used to detect replayed packet.
The Increasing-number option is defined to carry a strictly-
increasing serial number. Timestamp is one of the possible
implementation choice.
o The Encrypted-message option that contains the encrypted DHCPv6
message.
o The Encrypted-Query message that is sent from the secure DHCPv6
client to the secure DHCPv6 server. The Encrypted-Query message
MUST contain the Encrypted-message option. In addition, the
Server Identifier option MUST be contained if it is contained in
the original DHCPv6 message. The Encrypted-Query message MUST NOT
contain other options except the Server Identifier option and
Encrypted-message option.
o The Encrypted-Response message that is sent from the secure DHCPv6
server to the secure DHCPv6 client. The Encrypted-Response
message contains the Encrypted-message option. The Encrypted-
Response message MUST NOT contain other options except Encrypted-
message option.
5.3. Support for Algorithm Agility
In order to provide a means of addressing problems that may emerge
with existing hash algorithms, signature algorithm and encryption
algorithms in the future, this document provides a mechanism to
support algotirhm agility. The support for algorithm agility in this
document is mainly a algorithm notification mechanism between the
client and the server. The same client and server SHOULD use the
various algorithm in a single communication session.
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If the server does not support the algorithm used by the client, the
server SHOULD reply with an AlgorithmNotSupported status code
(defined in Section 9.3) to the client. Upon receiving this status
code, the client MAY resend the message protected with the mandatory
algorithm.
5.4. Applicability
In principle, secure DHCPv6 is applicable in any environment where
physical security on the link is not assured and attacks on DHCPv6
are a concern. In practice, however, authenticated and encrypted
DHCPv6 configuration will rely on some operational assumptions mainly
regarding public key distribution and management. In order to
achieve the more wide use of secure DHCPv6, opportunistic security
[RFC7435] can be applied for secure DHCPv6 deployment, which allows
DHCPv6 encryption in environments where support for authentication is
not available.
In some scenario where authentication is not available, secure DHCPv6
provides encryption without authentication to achieve the wide
deployment of secure DHCPv6.
Secure DHCPv6 provides authentication and encryption based either on
pre-sharing of authorized certificates, or else using trust-on-first-
use. The One feasible environment in an early deployment stage would
be enterprise networks. In such networks the security policy tends
to be strict and it will be easier to manage client hosts. One
trivial deployment scenario is therefore to manually pre-configure
client with the trusted servers' public key and manually register
clients' public keys for the server. It may also be possible to
deploy an internal PKI to make this less reliant on manual
operations, although it is currently subject to future study
specifically how to integrate such a PKI into the DHCPv6 service for
the network.
Note that this deployment scenario based on manual operation is not
different very much from the existing, shared-secret based
authentication mechanisms defined in [RFC3315] in terms of
operational costs. However, Secure DHCPv6 is still securer than the
shared-secret mechanism in that even if clients' keys stored for the
server are stolen that does not mean an immediate threat as these are
public keys. In addition, if some kind of PKI is used with Secure
DHCPv6, even if the initial installation of the certificates is done
manually, it will help reduce operational costs of revocation in case
a private key (especially that of the server) is compromised.
It is believed that Secure DHCPv6 could be more widely applicable
with integration of generic PKI so that it will be more easily
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deployed. But such a deployment requires more general issues with
PKI deployment be addressed, and it is currently unknown whether we
can find practical deployment scenarios. It is subject to future
study and experiments, and out of scope of this document.
6. DHCPv6 Client Behavior
For the secure DHCPv6 client, a certificate is needed for client
authentication. The client is pre-configured with a certificate and
its corresponding private key. If the client is pre-configured with
public key but not with a certificate, it can generate the self-
signed certificate for client authentication.
The secure DHCPv6 client sends Information-request message as per
[RFC3315]. The Information-request message is used by the DHCPv6
client to request the server's identity verification information
without having addresses, prefixes or any non-security options
assigned to it. The Information-request message MUST NOT include any
DHCPv6 options except ORO option to minimize client's privacy
information leakage. The Option Request option in the Information-
request message MUST contain the option code of the Certificate
option.
When receiving the Reply messages from DHCPv6 servers, a secure
DHCPv6 client discards any DHCPv6 messages that meet any of the
following conditions:
o the Signature option is missing,
o multiple Signature options are present,
o the Certificate option is missing.
And then the client first checks the support of the hash algorithm,
signature algorithm and encryption algorithm that the server used.
If the check fails, the Reply message is dropped. If the hash
algorithm field is zero, the signature algorithm and hash algorithm
are not separated. The corresponding hash algorithm is fixed
according the signature algorithm. If all the algorithms are
supported, the client then checks the authority of this server. The
client also uses the same algorithms in the return messages.
The client validates the certificates through the pre-configured
local trusted certificates list or other methods. A certificate that
finds a match in the local trust certificates list is treated as
verified. The message transaction-id is used as the identifier of
the authenticated server's public key for further message encryption.
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At this point, the client has either recognized the certificate of
the server, or decided to drop the message.
The client MUST now authenticate the server by verifying the
signature and checking increasing number, if there is a Increasing-
number option. The order of two procedures is left as an
implementation decision. It is RECOMMENDED to check increasing
number first, because signature verification is much more
computationally expensive. If the decrypted message contains the
Increasing-number option, the client checks it by comparing it with
the stored number on the client. The client has one stable stored
number for replay attack detection. The initial value of the stable
stored number is zero. If the contained number is higher than the
stored number, then the DHCPv6 message passes the increasing-number
check and the value of the stored number is changed into the value of
the Increasing-number option. If contained number is lower than the
stored number on the server, the server MUST drop the DHCPv6 message.
The Signature field verification MUST show that the signature has
been calculated as specified in Section 9.1.2. Only the messages
that get through both the signature verification and increasing
number check (if there is a Increasing-number option) are accepted.
Reply message that does not pass the above tests MUST be discarded.
If there are multiple authenticated DHCPv6 certs, the client selects
one DHCPv6 cert for the following network parameters configuration.
The selected DHCPv6 cert may corresponds to multiple DHCPv6 servers.
The client can also choose other implementation method depending on
the client's local policy if the defined protocol can also run
normally. For example, the client can try multiple transactions
(each encrypted with different public key) at the "same" time.
If there are no authenticated DHCPv6 certs or existing servers fail
authentication, the client should retry a number of times. The
client conducts the server discovery process as per section 18.1.5 of
[RFC3315] to avoid the packet storm. In this way, it is difficult
for the rogue server to beat out a busy "real" server. And then the
client takes some alternative action depending on its local policy,
such as attempting to use an unsecured DHCPv6 server. In some
scenario, such as laptops in coffee room, clients are always not pre-
configured the sufficient information for server authentication and
can accept DHCPv6 encryption without DHCPv6 authentication. In such
scenario, if some DHCPv6 servers fail authentication because the
server's certificate is not in the trusted certs' list, and then the
client selects one DHCPv6 server and record the server's public key
for the future encrypted DHCPv6 configuration process.
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Once the server has been authenticated, the DHCPv6 client sends the
Encrypted-Query message to the DHCPv6 server. The Encrypted-Query
message contains the Encrypted-message option, which MUST be
constructed as explained in Section 9.1.4. In addition, the Server
Identifier option MUST be contained if it is in the original message
(i.e. Request, Renew, Decline, Release) to avoid the extra
decryption for the DHCPv6 servers not for it. The Encrypted-message
option contains the DHCPv6 message that is encrypted using the public
key contained in the selected cert. The Server Identifier option is
externally visible to avoid decryption cost by those unselected
servers. The Encrypted-Query message MUST NOT contain other DHCPv6
option except the Server Identifier option and Encrypted-Message
option.
If the received Reply message indicates the request of the client's
certificate information through the Option Request option, the first
DHCPv6 message sent from the client to the server, such as Solicit
message, MUST contain the Certificate option, Signature option and
Increasing-number option for client authentication. The encryption
text SHOULD be formatted as explain in [RFC5652]. The Certificate
option MUST be constructed as explained in Section 9.1.1. In
addition, one and only one Signature option MUST be contained, which
MUST be constructed as explained in Section 9.1.2. One and only one
Increasing-number option SHOULD be contained, which MUST be
constructed as explained in Section 9.1.3.
If the client has multiple certificates with different public/private
key pairs, the message transaction-id is used as the identifier of
the client's private key for decryption. In addition, the subsequent
encrypted DHCPv6 message can contain the Increasing-number option to
defend against replay attack.
For the received Encrypted-Response message, the client MUST drop the
Encrypted-Response message if other DHCPv6 option except Encrypted-
message option is contained. Then, the client extracts the
Encrypted-message option and decrypts it using its private key to
obtain the original DHCPv6 message. Then it handles the message as
per [RFC3315]. If the decrypted DHCPv6 message contains the
Increasing-number option, the DHCPv6 client MUST drop the DHCPv6
message with the lower number. If the client fails to get the proper
parameters from the chosen server, it sends the Encrypted-Query
message to another authenticated server for parameters configuration
until the client obtains the proper parameters.
When the client receives a Reply message with an error status code,
the error status code indicates the failure reason on the server
side. According to the received status code, the client MAY take
follow-up action:
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o Upon receiving an AlgorithmNotSupported error status code, the
client SHOULD resend the message protected with one of the
mandatory algorithms.
o Upon receiving an AuthenticationFail error status code, the client
is not able to build up the secure communication with the server.
However, there may be other DHCPv6 servers available that
successfully complete authentication. The client MAY use the
AuthenticationFail as a hint and switch to other certificate if it
has another one; but otherwise treat the message containing the
status code as if it had not been received. But it SHOULD NOT
retry with the same certificate. However, if the client decides
to retransmit using the same certificate after receiving
AuthenticationFail, it MUST NOT retransmit immediately and MUST
follow normal retransmission routines defined in [RFC3315].
o Upon receiving a DecryptionFail error status code, the client MAY
resend the message following normal retransmission routines
defined in [RFC3315].
o Upon receiving a IncreasingnumFail error status code, the client
MAY resend the message with an adjusted Increasing-number option
according to the returned clock from the DHCPv6 server.
o Upon receiving a SignatureFail error status code, the client MAY
resend the message following normal retransmission routines
defined in [RFC3315].
7. DHCPv6 Server Behavior
For the secure DHCPv6 server, a certificate is needed for server
authentication. The server is pre-configured with a certificate and
its corresponding private key. If the server is pre-configured with
public key but not with a certificate, it can generate the self-
signed certificate for server authentication.
When the DHCPv6 server receives the Information-request message and
the contained Option Request option identifies the request is for the
server certificate information, it replies with a Reply message to
the client. The Reply message MUST contain the requested Certificate
option, which MUST be constructed as explained in Section 9.1.1, and
Server Identifier option. In addition, the Reply message MUST
contain one and only one Signature option, which MUST be constructed
as explained in Section 9.1.2. Besides, the Reply message SHOULD
contain one and only one Increasing-number option, which MUST be
constructed as explained in Section 9.1.3. In addition, if client
authentication is needed, then the ORO option in the Reply message
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contains the code of the certificate option to indicate the request
of the client certificate information.
Upon the receipt of Encrypted-Query message, the server MUST drop the
message if the other DHCPv6 option except Server Identifier option
and Encrypted-message option is contained. Then, the server checks
the Server Identifier option if the Encrypted-Query message contains
the Server Identifier option. The DHCPv6 server drops the message
that is not for it, thus not paying cost to decrypt messages not for
it. It decrypts the Encrypted-message option using its private key
if it is the target server.
If the secure DHPCv6 need client authentication and decrypted message
is a Solicit/Information-request message which contains the
information for client authentication, the secure DHCPv6 server
discards the received message that meets any of the following
conditions:
o the Signature option is missing,
o multiple Signature options are present,
o the Certificate option is missing.
In such failure, the server replies with an UnspecFail (value 1,
[RFC3315]) error status code.
The server SHOULD first check the support of the hash function,
signature algorithm, encryption algorithm that the client used. If
the hash algorithm field is zero, then the signature algorithm and
hash algorithm are not separated. The corresponding hash algorithm
is fixed according the signature algorithm. If the check fails, the
server SHOULD reply with an AlgorithmNotSupported error status code,
defined in Section 9.3, back to the client. If all the algorithms
are supported, the server then checks the authority of this client.
The server validates the client's certificate through the local pre-
configured trusted certificates list. A certificate that finds a
match in the local trust certificates list is treated as verified.
The message that fails authentication validation MUST be dropped. In
such failure, the DHCPv6 server replies with an AuthenticationFail
error status code, defined in Section 9.3, back to the client. At
this point, the server has either recognized the authentication of
the client, or decided to drop the message.
If the decrypted message contains the Increasing-number option, the
server checks it by comparing it with the stored number on the
server. The server has one stable stored number for replay attack
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detection. The initial value of the stable stored number is zero.
If the contained number is higher than the stored number, the value
of the stored number is changed into the value of the Increasing-
number option. If contained number is lower than the stored number
on the server, the server MUST drop the DHCPv6 message and a
IncreasingnumFail error status code, defined in Section 9.3, should
be sent back to the client. Depending on server's local policy, the
message without a Increasing-number option MAY be acceptable or
rejected. If the server rejects such a message, a IncreasingnumFail
error status code should be sent back to the client. The Reply
message that carries the IncreasingnumFail error status code carries
a Increasing-number option, which indicates the server's storage
number for the client to use.
The Signature field verification MUST show that the signature has
been calculated as specified in Section 9.1.2. Only the clients that
get through both the signature verification and increasing number
check (if there is a Increasing-number option) are accepted as
authenticated clients and continue to be handled their message as
defined in [RFC3315]. Clients that do not pass the above tests MUST
be treated as unauthenticated clients. The DHCPv6 server SHOULD
reply a SignatureFail error status code, defined in Section 9.3, for
the signature verification failure.
Once the client has been authenticated, the DHCPv6 server sends the
Encrypted-response message to the DHCPv6 client. The Encrypted-
response message MUST only contain the Encrypted-message option,
which MUST be constructed as explained in Section 9.1.4. The
encryption text SHOULD be formatted as explain in [RFC5652]. The
Encrypted-message option contains the encrypted DHCPv6 message that
is encrypted using the authenticated client's public key. To provide
the replay protection, the Increasing-number option can be contained
in the encrypted DHCPv6 message.
8. Relay Agent Behavior
When a DHCPv6 relay agent receives an Encrypted-query or Encrypted-
response message, it may not recognize this message. The unknown
messages MUST be forwarded as described in [RFC7283].
When a DHCPv6 relay agent recognizes the Encrypted-query and
Encrypted-response messages, it forwards the message according to
section 20 of [RFC3315]. There is nothing more the relay agents have
to do, it neither needs to verify the messages from client or server,
nor add any secure DHCPv6 options. Actually, by definition in this
document, relay agents MUST NOT add any secure DHCPv6 options.
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Relay-forward and Relay-reply messages MUST NOT contain any
additional Certificate option or Increasing-number option, aside from
those present in the innermost encapsulated messages from the client
or server.
Relay agent is RECOMMENDED to cache server announcements to form the
list of the available DHCPv6 server certs. If the relay agent
receives the Information-request message, then it replies with a list
of server certs available locally. In this way, the client can be
confident of a quick response, and therefore treat the lack of a
quick response as an indication that no authenticated DHCP servers
exist.
9. Extensions for Secure DHCPv6
This section describes the extensions to DHCPv6. Four new DHCPv6
options, two new DHCPv6 messages and five new status codes are
defined.
9.1. New DHCPv6 Options
9.1.1. Certificate Option
The Certificate option carries the certificate of the client/server.
The format of the Certificate option is described as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CERTIFICATE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EA-id | |
+-+-+-+-+-+-+-+-+ .
. Certificate (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_CERTIFICATE (TBA1).
option-len 1 + Length of certificate in octets.
EA-id Encryption Algorithm id. The encryption algorithm
is used for the encrypted DHCPv6 configuration
process. This design is adopted in order to provide
encryption algorithm agility. The value is from the
Encryption Algorithm for Secure DHCPv6 registry in
IANA. A registry of the initial assigned values
is defined in Section 12.
Certificate A variable-length field containing certificate. The
encoding of certificate and certificate data MUST
be in format as defined in Section 3.6, [RFC7296].
The support of X.509 certificate is mandatory.
9.1.2. Signature option
The Signature option allows a signature that is signed by the private
key to be attached to a DHCPv6 message. The Signature option could
be in any place within the DHCPv6 message while it is logically
created after the entire DHCPv6 header and options. It protects the
entire DHCPv6 header and options, including itself. The format of
the Signature option is described as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIGNATURE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SA-id | HA-id | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
. Signature (variable length) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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option-code OPTION_SIGNATURE (TBA2).
option-len 2 + Length of Signature field in octets.
SA-id Signature Algorithm id. The signature algorithm is
used for computing the signature result. This
design is adopted in order to provide signature
algorithm agility. The value is from the Signature
Algorithm for Secure DHCPv6 registry in IANA. The
support of RSASSA-PKCS1-v1_5 is mandatory. A
registry of the initial assigned values is defined
in Section 12.
HA-id Hash Algorithm id. The hash algorithm is used for
computing the signature result. This design is
adopted in order to provide hash algorithm agility.
The value is from the Hash Algorithm for Secure
DHCPv6 registry in IANA. The support of SHA-256 is
mandatory. A registry of the initial assigned values
is defined in Section 12. If the signature algorithm
and hash algorithm cannot be separated, the HA-id
field is zero. The hash algorithm is decided by the
corresponding signature algorithm.
Signature A variable-length field containing a digital
signature. The signature value is computed with
the hash algorithm and the signature algorithm,
as described in HA-id and SA-id. The signature
constructed by using the sender's private key
protects the following sequence of octets:
1. The DHCPv6 message header.
2. All DHCPv6 options including the Signature
option (fill the Signature field with zeroes).
The Signature field MUST be padded, with all 0, to
the next octet boundary if its size is not a
multiple of 8 bits. The padding length depends on
the signature algorithm, which is indicated in the
SA-id field.
Note: If Secure DHCPv6 is used, the DHCPv6 message is encrypted in a
way that the authentication mechanism defined in RFC3315 does not
understand. So the Authentication option SHOULD NOT be used if
Secure DHCPv6 is applied.
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9.1.3. Increasing-number Option
The Increasing-number option carries the number which is higher than
the local stored number on the client/server. It adds the anti-
replay protection to the DHCPv6 messages. It is optional.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_INCREASINGNUM | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| InreasingNum (32-bit) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_INCREASINGNUM (TBA3).
option-len 4, in octets.
IncreasingNum A number which is higher than the local stored number on the
client/server for the replay attack detection.
9.1.4. Encrypted-message Option
The Encrypted-message option carries the encrypted DHCPv6 message
with the recipient's public key.
The format of the Encrypted-message option is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. encrypted DHCPv6 message .
. (variable) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Encrypted-message Option Format
option-code OPTION_ENCRYPTED_MSG (TBA4).
option-len Length of the encrypted DHCPv6 message.
encrypted DHCPv6 message A variable length field containing the
encrypted DHCPv6 message sent by the client or the server. In
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Encrypted-Query message, it contains encrypted DHCPv6 message sent
by a client. In Encrypted-response message, it contains encrypted
DHCPv6 message sent by a server.
9.2. New DHCPv6 Messages
Two new DHCPv6 messages are defined to achieve the DHCPv6 encryption:
Encrypted-Query and Encrypted-Response. Both the DHCPv6 messages
defined in this document share the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type | transaction-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. options .
. (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The format of Encrypted-Query and Encrypted-Response
Messages
msg-type Identifier of the message type. It can be either
Encrypted-Query (TBA5) or DHCPv6-Response (TBA6).
transaction-id The transaction ID for this message exchange.
options The Encrypted-Query message MUST only contain the
Server Identifier option or Encrypted-message option.
The Encrypted-Response message MUST only contain the
Encrypted-message option.
9.3. Status Codes
The following new status codes, see Section 5.4 of [RFC3315] are
defined.
o AlgorithmNotSupported (TBD7): indicates that the DHCPv6 server
does not support algorithms that sender used.
o AuthenticationFail (TBD8): indicates that the message from the
DHCPv6 client fails authentication check.
o IncreasingnumFail (TBD9): indicates the message from DHCPv6 client
fails the increasing number check.
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o SignatureFail (TBD10): indicates the message from DHCPv6 client
fails the signature check.
o DecryptionFail (TBD11): indicates the message from DHCPv6 client
fails the DHCPv6 message decryption.
10. Security Considerations
This document provides the authentication and encryption mechanisms
for DHCPv6.
[RFC6273] has analyzed possible threats to the hash algorithms used
in SEND. Since Secure DHCPv6 defined in this document uses the same
hash algorithms in similar way to SEND, analysis results could be
applied as well: current attacks on hash functions do not constitute
any practical threat to the digital signatures used in the signature
algorithm in Secure DHCPv6.
A server, whose local policy accepts messages without a Increasing-
number option, may have to face the risk of replay attacks.
There are some mandatory algorithm for encryption algorithm in this
document. It may be at some point that the mandatory algorithm is no
longer safe to use.
If the client tries more than one cert for client authentication, the
server can easily get a client that implements this to enumerate its
entire cert list and probably learn a lot about a client that way.
11. IANA Considerations
This document defines four new DHCPv6 [RFC3315] options. The IANA is
requested to assign values for these four options from the DHCPv6
Option Codes table of the DHCPv6 Parameters registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters. The four options
are:
The Certificate Option (TBA1), described in Section 9.1.1.
The Signature Option (TBA2), described in Section 9.1.2.
The Increasing-number Option (TBA3),described in Section 9.1.3.
The Encrypted-message Option (TBA4), described in Section 9.1.4.
The IANA is also requested to assign value for these two messages
from the DHCPv6 Message Types table of the DHCPv6 Parameters registry
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maintained in http://www.iana.org/assignments/dhcpv6-parameters. The
two messages are:
The Encrypted-Query Message (TBA5), described in Section 9.2.
The Encrypted-Response Message (TBA6), described in Section 9.2.
The IANA is also requested to add three new registry tables to the
DHCPv6 Parameters registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters. The three tables
are the Hash Algorithm for Secure DHCPv6 table, the Signature
Algorithm for Secure DHCPv6 table and the Encryption Algorithm for
Secure DHCPv6 table.
Initial values for these registries are given below. Future
assignments are to be made through Standards Action [RFC5226].
Assignments for each registry consist of a name, a value and a RFC
number where the registry is defined.
Hash Algorithm for Secure DHCPv6. The values in this table are 8-bit
unsigned integers. The following initial values are assigned for
Hash Algorithm for Secure DHCPv6 in this document:
Name | Value | RFCs
-------------------+---------+--------------
SigAlg-Combined | ox00 | this document
SHA-256 | 0x01 | this document
SHA-512 | 0x02 | this document
Signature Algorithm for Secure DHCPv6. The values in this table are
8-bit unsigned integers. The following initial values are assigned
for Signature Algorithm for Secure DHCPv6 in this document:
Name | Value | RFCs
-------------------+---------+--------------
RSASSA-PKCS1-v1_5 | 0x01 | this document
Encryption algorithm for Secure DHCPv6. The values in this table are
8-bit unsigned integers. The following initial values are assigned
for encryption algorithm for Secure DHCPv6 in this document:
Name | Value | RFCs
-------------------+---------+--------------
RSA | 0x01 | this document
IANA is requested to assign the following new DHCPv6 Status Codes,
defined in Section 9.3, in the DHCPv6 Parameters registry maintained
in http://www.iana.org/assignments/dhcpv6-parameters:
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Code | Name | Reference
---------+-----------------------+--------------
TBD7 | AlgorithmNotSupported | this document
TBD8 | AuthenticationFail | this document
TBD9 | IncreasingnumFail | this document
TBD10 | SignatureFail | this document
TBD11 | DecryptionFail | this document
12. Acknowledgements
The authors would like to thank Tomek Mrugalski, Bernie Volz,
Jianping Wu, Randy Bush, Yiu Lee, Sean Shen, Ralph Droms, Jari Arkko,
Sean Turner, Stephen Farrell, Christian Huitema, Stephen Kent, Thomas
Huth, David Schumacher, Francis Dupont, Gang Chen, Suresh Krishnan,
Fred Templin, Robert Elz, Nico Williams, Erik Kline, Alan DeKok,
Bernard Aboba, Sam Hartman, Qi Sun, Zilong Liu and other members of
the IETF DHC working group for their valuable comments.
This document was produced using the xml2rfc tool [RFC2629].
13. Change log [RFC Editor: Please remove]
draft-ietf-dhc-sedhcpv6-13: Change the Timestamp option into
Increasing-number option and the corresponding check method; Delete
the OCSP stampling part for the certificate check; Add the scenario
where the hash and signature algorithms cannot be separated; Add the
comparison with RFC7824 and RFC7844; Add the encryption text format
and reference of RFC5652. Add the consideration of scenario where
multiple DHCPv6 servers share one common DHCPv6 server. Add the
statement that Encrypted-Query and Encrypted-Response messages can
only contain certain options: Server Identifier option and Encrypted-
message option. Add opportunistic security for deployment
consideration. Besides authentication+encyrption mode, encryption-
only mode is added.
draft-ietf-dhc-sedhcpv6-12: Add the Signature option and timestamp
option during server/client authentication process. Add the hash
function and signature algorithm. Add the requirement: The
Information-request message cannot contain any other options except
ORO option. Modify the use of "SHOULD"; Delete the reference of
RFC5280 and modify the method of client/server cert verification; Add
the relay agent cache function for the quick response when there is
no authenticated server. 2016-4-24.
draft-ietf-dhc-sedhcpv6-11: Delete the Signature option, because the
encrypted DHCPv6 message and the Information-request message (only
contain the Certificate option) don't need the Signature option for
message integrity check; Rewrite the "Applicability" section; Add the
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encryption algorithm negotiation process; To support the encryption
algorithm negotiation, the Certificate option contains the EA-
id(encryption algorithm identifier) field; Reserve the Timestamp
option to defend against the replay attacks for encrypted DHCPv6
configuration process; Modify the client behavior when there is no
authenticated DHCPv6 server; Add the DecryptionFail error code.
2016-3-9.
draft-ietf-dhc-sedhcpv6-10: merge DHCPv6 authentication and DHCPv6
encryption. The public key option is removed, because the device can
generate the self-signed certificate if it is pre-configured the
public key not the certificate. 2015-12-10.
draft-ietf-dhc-sedhcpv6-09: change some texts about the deployment
part.2015-12-10.
draft-ietf-dhc-sedhcpv6-08: clarified what the client and the server
should do if it receives a message using unsupported algorithm;
refined the error code treatment regarding to AuthenticationFail and
TimestampFail; added consideration on how to reduce the DoS attack
when using TOFU; other general editorial cleanups. 2015-06-10.
draft-ietf-dhc-sedhcpv6-07: removed the deployment consideration
section; instead, described more straightforward use cases with TOFU
in the overview section, and clarified how the public keys would be
stored at the recipient when TOFU is used. The overview section also
clarified the integration of PKI or other similar infrastructure is
an open issue. 2015-03-23.
draft-ietf-dhc-sedhcpv6-06: remove the limitation that only clients
use PKI- certificates and only servers use public keys. The new text
would allow clients use public keys and servers use PKI-certificates.
2015-02-18.
draft-ietf-dhc-sedhcpv6-05: addressed comments from mail list that
responsed to the second WGLC. 2014-12-08.
draft-ietf-dhc-sedhcpv6-04: addressed comments from mail list.
Making timestamp an independent and optional option. Reduce the
serverside authentication to base on only client's certificate.
Reduce the clientside authentication to only Leaf of Faith base on
server's public key. 2014-09-26.
draft-ietf-dhc-sedhcpv6-03: addressed comments from WGLC. Added a
new section "Deployment Consideration". Corrected the Public Key
Field in the Public Key Option. Added consideration for large DHCPv6
message transmission. Added TimestampFail error code. Refined the
retransmission rules on clients. 2014-06-18.
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draft-ietf-dhc-sedhcpv6-02: addressed comments (applicability
statement, redesign the error codes and their logic) from IETF89 DHC
WG meeting and volunteer reviewers. 2014-04-14.
draft-ietf-dhc-sedhcpv6-01: addressed comments from IETF88 DHC WG
meeting. Moved Dacheng Zhang from acknowledgement to be co-author.
2014-02-14.
draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19.
draft-jiang-dhc-sedhcpv6-02: removed protection between relay agent
and server due to complexity, following the comments from Ted Lemon,
Bernie Volz. 2013-10-16.
draft-jiang-dhc-sedhcpv6-01: update according to review comments from
Ted Lemon, Bernie Volz, Ralph Droms. Separated Public Key/
Certificate option into two options. Refined many detailed
processes. 2013-10-08.
draft-jiang-dhc-sedhcpv6-00: original version, this draft is a
replacement of draft-ietf-dhc-secure-dhcpv6, which reached IESG and
dead because of consideration regarding to CGA. The authors followed
the suggestion from IESG making a general public key based mechanism.
2013-06-29.
14. Open Issues [RFC Editor: Please remove]
The Reply message with the error status code may contain the client
identifier option, then the client's privacy information may be
disclosed. The possible way is that we encrypts the Reply message.
But if the error is AlogorithmNotSupported, then the server cannot
encrypt the message with the algorithm used by client.
We need to add some explanation on why TOFU is out of scope
currently. TOFU is tricky to get it right. If it is included, then
operator may skip necessary setup for security. TOFU may be included
in the future work.
15. References
15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[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>.
[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971,
DOI 10.17487/RFC3971, March 2005,
<http://www.rfc-editor.org/info/rfc3971>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", RFC 4443,
DOI 10.17487/RFC4443, March 2006,
<http://www.rfc-editor.org/info/rfc4443>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://www.rfc-editor.org/info/rfc5652>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<http://www.rfc-editor.org/info/rfc5905>.
[RFC7283] Cui, Y., Sun, Q., and T. Lemon, "Handling Unknown DHCPv6
Messages", RFC 7283, DOI 10.17487/RFC7283, July 2014,
<http://www.rfc-editor.org/info/rfc7283>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[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>.
[RFC7824] Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
Considerations for DHCPv6", RFC 7824,
DOI 10.17487/RFC7824, May 2016,
<http://www.rfc-editor.org/info/rfc7824>.
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[RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
Profiles for DHCP Clients", RFC 7844,
DOI 10.17487/RFC7844, May 2016,
<http://www.rfc-editor.org/info/rfc7844>.
15.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
DOI 10.17487/RFC2629, June 1999,
<http://www.rfc-editor.org/info/rfc2629>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6273] Kukec, A., Krishnan, S., and S. Jiang, "The Secure
Neighbor Discovery (SEND) Hash Threat Analysis", RFC 6273,
DOI 10.17487/RFC6273, June 2011,
<http://www.rfc-editor.org/info/rfc6273>.
[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>.
[RSA] RSA Laboratories, "RSA Encryption Standard, Version 2.1,
PKCS 1", November 2002.
Authors' Addresses
Sheng Jiang
Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road
Hai-Dian District, Beijing, 100095
CN
Email: jiangsheng@huawei.com
Lishan Li
Tsinghua University
Beijing 100084
P.R.China
Phone: +86-15201441862
Email: lilishan48@gmail.com
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Yong Cui
Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-6260-3059
Email: yong@csnet1.cs.tsinghua.edu.cn
Tatuya Jinmei
Infoblox Inc.
3111 Coronado Drive
Santa Clara, CA
US
Email: jinmei@wide.ad.jp
Ted Lemon
Nominum, Inc.
2000 Seaport Blvd
Redwood City, CA 94063
USA
Phone: +1-650-381-6000
Email: Ted.Lemon@nominum.com
Dacheng Zhang
Beijing
CN
Email: dacheng.zhang@gmail.com
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