draft-ietf-dhc-sedhcpv6-02.txt   draft-ietf-dhc-sedhcpv6-03.txt 
DHC Working Group S. Jiang, Ed. DHC Working Group S. Jiang, Ed.
Internet-Draft Huawei Technologies Co., Ltd Internet-Draft Huawei Technologies Co., Ltd
Intended status: Standards Track S. Shen Intended status: Standards Track S. Shen
Expires: October 17, 2014 CNNIC Expires: December 21, 2014 CNNIC
D. Zhang D. Zhang
Huawei Technologies Co., Ltd Huawei Technologies Co., Ltd
April 15, 2014 T. Jinmei
WIDE Project
June 19, 2014
Secure DHCPv6 with Public Key Secure DHCPv6 with Public Key
draft-ietf-dhc-sedhcpv6-02 draft-ietf-dhc-sedhcpv6-03
Abstract Abstract
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) enables The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) enables
DHCPv6 servers to pass configuration parameters. It offers DHCPv6 servers to pass configuration parameters. It offers
configuration flexibility. If not secured, DHCPv6 is vulnerable to configuration flexibility. If not secured, DHCPv6 is vulnerable to
various attacks, particularly spoofing attacks. This document various attacks, particularly spoofing attacks. This document
analyzes the security issues of DHCPv6 and specifies a Secure DHCPv6 analyzes the security issues of DHCPv6 and specifies a Secure DHCPv6
mechanism for communication between DHCPv6 client and server. This mechanism for communication between DHCPv6 clients and DHCPv6
mechanism is based on public/private key pairs. The authority of the servers. This mechanism is based on public/private key pairs. The
sender may depend on either pre-configuration mechanism or Public Key authority of the sender may depend on either pre-configuration
Infrastructure. mechanism or Public Key Infrastructure.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 17, 2014. This Internet-Draft will expire on December 21, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 18 skipping to change at page 2, line 21
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language and Terminology . . . . . . . . . . . . 3 2. Requirements Language and Terminology . . . . . . . . . . . . 3
3. Security Overview of DHCPv6 . . . . . . . . . . . . . . . . . 3 3. Security Overview of DHCPv6 . . . . . . . . . . . . . . . . . 3
4. Overview of Secure DHCPv6 Mechanism with Public Key . . . . . 4 4. Overview of Secure DHCPv6 Mechanism with Public Key . . . . . 4
4.1. New Components . . . . . . . . . . . . . . . . . . . . . 5 4.1. New Components . . . . . . . . . . . . . . . . . . . . . 6
4.2. Support for algorithm agility . . . . . . . . . . . . . . 6 4.2. Support for algorithm agility . . . . . . . . . . . . . . 6
4.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 6 4.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 7
5. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 7 5. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 7
5.1. Public Key Option . . . . . . . . . . . . . . . . . . . . 7 5.1. Public Key Option . . . . . . . . . . . . . . . . . . . . 7
5.2. Certificate Option . . . . . . . . . . . . . . . . . . . 7 5.2. Certificate Option . . . . . . . . . . . . . . . . . . . 8
5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 8 5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 9
5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 10 5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 10
6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 10 6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 11
6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 10 6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 11
6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 11 6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 12
6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 13 6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 14
6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 13 6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 7. Deployment Consideration . . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7.1. Authentication on a client . . . . . . . . . . . . . . . 16
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 7.2. Authentication on a server . . . . . . . . . . . . . . . 16
10. Change log [RFC Editor: Please remove] . . . . . . . . . . . 17 8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 18 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
11.2. Informative References . . . . . . . . . . . . . . . . . 18 11. Change log [RFC Editor: Please remove] . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
12.1. Normative References . . . . . . . . . . . . . . . . . . 21
12.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315]) The Dynamic Host Configuration ProtocoFl for IPv6 (DHCPv6, [RFC3315])
enables DHCPv6 servers to pass configuration parameters. It offers enables DHCPv6 servers to pass configuration parameters. It offers
configuration flexibility. If not secured, DHCPv6 is vulnerable to configuration flexibility. If not secured, DHCPv6 is vulnerable to
various attacks, particularly spoofing attacks. various attacks, particularly spoofing attacks.
This document analyzes the security issues of DHCPv6 in details. This document analyzes the security issues of DHCPv6 in details.
This document provides mechanisms for improving the security of This document provides mechanisms for improving the security of
DHCPv6 between client and server: DHCPv6 between client and server:
o the identity of a DHCPv6 message sender, which can be a DHCPv6 o the identity of a DHCPv6 message sender, which can be a DHCPv6
server or a client, can be verified by a recipient. server or a client, can be verified by a recipient.
o the integrity of DHCPv6 messages can be checked by the recipient o the integrity of DHCPv6 messages can be checked by the recipient
of the message. of the message.
o anti-replay protection based on timestamp checking.
Note: this secure mechanism in this document does not protect the Note: this secure mechanism in this document does not protect the
relay-relevant options, either added by a relay agent toward a server relay-relevant options, either added by a relay agent toward a server
or added by a server toward a relay agent, are considered less or added by a server toward a relay agent, are considered less
vulnerable, because they are only transported within operator vulnerable, because they are only transported within operator
networks. Communication between a server and a relay agent, and networks. Communication between a server and a relay agent, and
communication between relay agents, may be secured through the use of communication between relay agents, may be secured through the use of
IPsec, as described in section 21.1 in [RFC3315]. IPsec, as described in section 21.1 in [RFC3315].
The security mechanisms specified in this document is based on self- The security mechanisms specified in this document is based on self-
generated public/private key pairs. It also integrates timestamps generated public/private key pairs. It also integrates timestamps
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each DHCPv6 client would need to be configured with its own secret each DHCPv6 client would need to be configured with its own secret
key; [RFC3315] provides no mechanism for doing this. key; [RFC3315] provides no mechanism for doing this.
For the key of the hash function, there are two key management For the key of the hash function, there are two key management
mechanisms. Firstly, the key management is done out of band, usually mechanisms. Firstly, the key management is done out of band, usually
through some manual process. For example, operators can set up a key through some manual process. For example, operators can set up a key
database for both servers and clients which the client obtains a key database for both servers and clients which the client obtains a key
before running DHCPv6. before running DHCPv6.
Manual key distribution runs counter to the goal of minimizing the Manual key distribution runs counter to the goal of minimizing the
configuration data needed at each host. [RFC3315] provides an configuration data needed at each host.
additional mechanism for preventing off-network timing attacks using
the Reconfigure message: the Reconfigure Key authentication method. [RFC3315] provides an additional mechanism for preventing off-network
However, this method provides no message integrity or source timing attacks using the Reconfigure message: the Reconfigure Key
integrity check. This key is transmitted in plaintext. authentication method. However, this method provides no message
integrity or source integrity check. This key is transmitted in
plaintext.
In comparison, the public/private key security mechanism allows the In comparison, the public/private key security mechanism allows the
keys to be generated by the sender, and allows the public key keys to be generated by the sender, and allows the public key
database on the recipient to be populated opportunistically or database on the recipient to be populated opportunistically or
manually, depending on the degree of confidence desired in a specific manually, depending on the degree of confidence desired in a specific
application. PKI security mechanism is simpler in the local key application. PKI security mechanism is simpler in the local key
management respect. management respect.
4. Overview of Secure DHCPv6 Mechanism with Public Key 4. Overview of Secure DHCPv6 Mechanism with Public Key
In order to enable a DHCP client and a server mutually authenticate In order to enable a DHCPv6 client and a server mutually authenticate
each other without previous key deployment, this document introduces each other without previous key deployment, this document introduces
the use of public/private key pair mechanism into DHCPv6, also with the use of public/private key pair mechanism into DHCPv6, also with
timestamp. The authority of the sender may depend on either pre- timestamp. The authority of the sender may depend on either pre-
configuration mechanism or PKI. By combining with the signatures, configuration mechanism or PKI. By combining with the signatures,
sender identity can be verified and messages protected. sender identity can be verified and messages protected.
This document introduces a Secure DHCPv6 mechanism that uses a public This document introduces a Secure DHCPv6 mechanism that uses a
/private key pair to secure the DHCPv6 protocol. In order to enable public/private key pair to secure the DHCPv6 protocol. In order to
DHCP clients and servers to perform mutual authentication, this enable DHCPv6 clients and DHCPv6 servers to perform mutual
solution provides two public key based mechanisms with different authentication, this solution provides two public key based
security strengths. One is stronger and only the certificate signed mechanisms with different security strengths. One is stronger and
by a trusted CA or preconfigured public key can be accepted. The only the certificate signed by a trusted CA or preconfigured public
other one, called as leap of faith (LoF) mechanism, is relatively key can be accepted. The other one, called as leap of faith (LoF)
weak. It allows a client/server pair, that lacks essential trust mechanism, is relatively weak. It allows a client/server pair that
relationship, to build up their trust relationship at run time for lacks essential trust relationship to build up their trust
subsequent exchanges based on faith. This design simplifies the relationship at run time for subsequent exchanges based on faith.
precondition of deploying DHCPv6 authentication and provides limited
protection of DHCPv6 message.
In the proposed soltuion, both public/private key pairs or This design simplifies the precondition of deploying DHCPv6
certificates are can be used in authentication. When using public/ authentication and provides limited protection of DHCPv6 message.
In the proposed solution, either public/private key pairs or
certificates can be used in authentication. When using public/
private key pairs directly, the public key of the sender is pre- private key pairs directly, the public key of the sender is pre-
shared with the recipient, either opportunistically or through a shared with the recipient, either opportunistically or through a
manual process. When using certificates, the sender has a manual process. When using certificates, the sender has a
certificate for its public key, signed by a CA that is trusted by the certificate for its public key, signed by a CA that is trusted by the
recipient. It is possible for the same public key to be used with recipient. It is possible for the same public key to be used with
different recipients in both modes. different recipients in both modes.
In this document, we introduce a public key option, a certificate In this document, we introduce a public key option, a certificate
option and a signature option with a corresponding verification option and a signature option with a corresponding verification
mechanism. Timestamp is integrated into signature options. A DHCPv6 mechanism. Timestamp is integrated into signature options. A DHCPv6
message (from a server or a client), with either a public key or message (from a server or a client), with either a public key or
certificate option, and carrying a digital signature, can be verified certificate option, and carrying a digital signature, can be verified
by the recipient for both the timestamp and authentication, then by the recipient for both the timestamp and authentication, then
process the payload of the DHCPv6 message only if the validation is process the payload of the DHCPv6 message only if the validation is
successful. Because the sender can be a DHCPv6 server or a client, successful. Because the sender can be a DHCPv6 server or a client,
the end-to-end security protection can be from DHCPv6 servers to the end-to-end security protection can be from DHCPv6 servers to
clients, or from clients to DHCPv6 servers. clients or from clients to DHCPv6 servers.
The recipient may choose to further process the message from a sender The recipient may choose to further process the message from a sender
for which no authentication information exists, either non-matched for which no authentication information exists, either non-matched
public key or certificate cannot be verified. By recording the public key or certificate cannot be verified. By recording the
public key or unverifiable certificate that was used by the sender, public key or unverifiable certificate that was used by the sender,
when the first time it is seen, the recipient can make a leap of when the first time it is seen, the recipient can make a leap of
faith that the sender is trustworthy. If no evidence to the contrary faith that the sender is trustworthy. If no evidence to the contrary
surfaces, the recipient can then validate the sender as trustworthy surfaces, the recipient can then validate the sender as trustworthy
when it subsequently sees the same public key or certificate used to when it subsequently sees the same public key or certificate used to
sign messages from the same sender. In opposite, once the recipient sign messages from the same sender. In opposite, once the recipient
has determined that it is being attacked, it can either forget that has determined that it is being attacked, it can either forget that
sender, or remember that sender in a blacklist and drop further sender, or remember that sender in a blacklist and drop further
packets associated with that sender. packets associated with that sender.
This improves communication security of DHCPv6 messages. The This improves communication security of DHCPv6 messages.
authentication options [RFC3315] may also be used for replay
protection. Secure DHCPv6 messages are commonly large. IP fragments [RFC2460]
are highly possible. Hence, deployment of Secure DHCPv6 should also
consider the issues of IP fragment, PMTU, etc. Also, if there are
firewalls between secure DHCPv6 clients and secure DHCPv6 servers, it
is RECOMMENDED that the firewalls are configureed to pass ICMP Packet
Too Big messages [RFC4443].
4.1. New Components 4.1. New Components
The components of the solution specified in this document are as The components of the solution specified in this document are as
follows: follows:
o The node generates a public/private key pair. A DHCPv6 option is o The node generates a public/private key pair. A DHCPv6 option is
defined that carries the public key. defined that carries the public key.
The node may also obtain a certificate from a Certificate The node may also obtain a certificate from a Certificate
skipping to change at page 6, line 12 skipping to change at page 6, line 26
Because the certificate contains the public key, there is never a Because the certificate contains the public key, there is never a
need to send both options at the same time. need to send both options at the same time.
o A signature generated using the private key that protects the o A signature generated using the private key that protects the
integrity of the DHCPv6 messages and authenticates the identity of integrity of the DHCPv6 messages and authenticates the identity of
the sender. the sender.
o A timestamp, to detect and prevent packet replay. The secure o A timestamp, to detect and prevent packet replay. The secure
DHCPv6 nodes need to meet some accuracy requirements and be synced DHCPv6 nodes need to meet some accuracy requirements and be synced
to global time, while the timestamp checking mechanism allows a to global time, while the timestamp checking mechanism allows a
configurable time value for clock drift. configurable time value for clock drift. The real time provision
is out of scope.
4.2. Support for algorithm agility 4.2. Support for algorithm agility
Hash functions are used to provide message integrity checks. In Hash functions are used to provide message integrity checks. In
order to provide a means of addressing problems that may emerge in order to provide a means of addressing problems that may emerge in
the future with existing hash algorithms, as recommended in the future with existing hash algorithms, as recommended in
[RFC4270], this document provides a mechanism for negotiating the use [RFC4270], this document provides a mechanism for negotiating the use
of more secure hashes in the future. of more secure hashes in the future.
In addition to hash algorithm agility, this document also provides a In addition to hash algorithm agility, this document also provides a
mechanism for signature algorithm agility. mechanism for signature algorithm agility.
The support for algorithm agility in this document is mainly a The support for algorithm agility in this document is mainly a
unilateral notification mechanism from sender to recipient. If the unilateral notification mechanism from sender to recipient. A
recipient does not support the algorithm used by the sender, it recipient MAY support various algorithms simultaneously, and the
cannot authenticate the message. In this case, the receiver SHOULD differenet senders in a same administrative domain may be allowed to
reply with a NotSupportAlgorithm status code (defined in use various algorithms simultaneously.
Section 5.4). Upon receiving this status code, the sender MAY resend
the message protected with the mandatory algorithms (defined in If the recipient does not support the algorithm used by the sender,
Section 5.3). Therefore, the senders in a same administrative domain it cannot authenticate the message. In the client-to-server case,
may be allowed to use various algorithms simultaneously. the server SHOULD reply with a AlgorithmNotSupported status code
(defined in Section 5.4). Upon receiving this status code, the
client MAY resend the message protected with the mandatory algorithm
(defined in Section 5.3).
4.3. Applicability 4.3. Applicability
By default, a secure DHCPv6 enabled client SHOULD start with secure By default, a secure DHCPv6 enabled client SHOULD start with secure
model. It sends a DHCPv6 message with secure options. If the mode by sending secure DHCPv6 messages. If the recipient is secure
recipient is secure DHCPv6 enabled server, their communication should DHCPv6 enabled server, their communication would be in secure mode.
be in secure model. In the scenario where the secure DHCPv6 enabled In the scenario where the secure DHCPv6 enabled client and server
client and server fail to build up secure communication between them, fail to build up secure communication between them, the secure DHCPv6
they may fall back the unsecure model, if both client and server enabled client MAY choose to send unsecured DHCPv6 message towards
allow it. the server.
A secure DHCPv6 enabled server MAY also provide services for
unsecured clients. In such case, the resources allocated for
unsecured clients SHOULD be separated and restricted, in order to
protect against bidding down attacks.
In the scenario where the recipient is a legacy DHCPv6 server that In the scenario where the recipient is a legacy DHCPv6 server that
does not support secure mechanism, the DHCPv6 server (for most of does not support secure mechanism, the DHCPv6 server (for all of
known DHCPv6 implemenations) would just omit or disregard unknown known DHCPv6 implementations) would just omit or disregard unknown
options and still process the known options. The reply message would options (secure options defined in this document) and still process
be unsecured, of course. It is up to the local policy of the client the known options. The reply message would be unsecured, of course.
whether to accept the messages. If the client accept the unsecure It is up to the local policy of the client whether to accept the
messages from the DHCPv6 server. The subsequent exchanges will be in messages. If the client accepts the unsecured messages from the
unsecure model. DHCPv6 server, the subsequent exchanges will be in the unsecured
mode.
In the scenario where a legacy client sends a unsecure message to a In the scenario where a legacy client sends an unsecured message to a
secure DHCPv6 enabled server, there are two possibilities depending secure DHCPv6 enabled server, there are two possibilities depending
on the server policy. If the server mandidates the authentication, on the server policy. If the server's policy requires the
an UnspecFail (value 1, [RFC3315]) error status code, SHOULD be authentication, an UnspecFail (value 1, [RFC3315]) error status code,
returned. In such case, the client cannot build up the connection SHOULD be returned. In such case, the client cannot build up the
with the server. If the server has been configured to support connection with the server. If the server has been configured to
unsecured request, the server would fall back the unsecure DHCPv6 support unsecured clients, the server would fall back to the
model, and reply unsecure messages toward the client. unsecured DHCPv6 mode, and reply unsecured messages toward the
client. The resources allocated for unsecured clients SHOULD be
separated and restricted.
5. Extensions for Secure DHCPv6 5. Extensions for Secure DHCPv6
This section extends DHCPv6. Three new options have been defined. This section extends DHCPv6. Three new options have been defined.
The new options MUST be supported in the Secure DHCPv6 message The new options MUST be supported in the Secure DHCPv6 message
exchange. exchange.
5.1. Public Key Option 5.1. Public Key Option
The Public Key option carries the public key of the sender. The The Public Key option carries the public key of the sender. The
skipping to change at page 7, line 39 skipping to change at page 8, line 19
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. Public Key (variable length) . . Public Key (variable length) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_PK_PARAMETER (TBA1). option-code OPTION_PK_PARAMETER (TBA1).
option-len Length of public key in octets. option-len Length of public key in octets.
Public Key A variable-length field containing public key. The Public Key A variable-length field containing public key and
key MUST be represented as a lower-case hexadecimal identify the algorithm with which the key is used
string with the most significant octet of the key (e.g., RSA, DSA, or Diffie-Hellman). The algorithm
first. Typically, the length of a 2048-bit RSA is identified using the AlgorithmIdentifier structure
public key is 256 bytes. specified in section 4.1.1.2, [RFC5280]. The object
identifiers for the supported algorithms and the
methods for encoding the public key materials
(public key and parameters) are specified in
[RFC3279], [RFC4055], and [RFC4491].
5.2. Certificate Option 5.2. Certificate Option
The Certificate option carries the certificate of the sender. The The Certificate option carries the certificate of the sender. The
format of the Certificate option is described as follows: format of the Certificate option is described as follows:
0 1 2 3 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 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_CERT_PARAMETER | option-len | | OPTION_CERT_PARAMETER | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. Certificate (variable length) . . Certificate (variable length) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_CERT_PARAMETER (TBA2). option-code OPTION_CERT_PARAMETER (TBA2).
option-len Length of certificate in octets, maximum 65535. option-len Length of certificate in octets.
Certificate A variable-length field containing certificate. The Certificate A variable-length field containing certificate. The
encoding of certificate and certificate data MUST encoding of certificate and certificate data MUST
be in format as defined in Section 3.6, [RFC5996]. be in format as defined in Section 3.6, [RFC5996].
The support of X.509 certificate is mandatory. The The support of X.509 certificate is mandatory. The
length of a certificate is various. In this length of a certificate is various.
specification, typically, the maximum length is
65535 bytes.
5.3. Signature Option 5.3. Signature Option
The Signature option allows public key-based signatures to be The Signature option allows public key-based signatures to be
attached to a DHCPv6 message. The Signature option could be any attached to a DHCPv6 message. The Signature option could be any
place within the DHCPv6 message. It protects the entire DHCPv6 place within the DHCPv6 message. It protects the entire DHCPv6
header and options, except for the Authentication Option. The format header and options, including itself, except for the Authentication
of the Signature option is described as follows: Option. The format of the Signature option is described as follows:
0 1 2 3 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 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 | | OPTION_SIGNATURE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HA-id | SA-id | | HA-id | SA-id | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Timestamp (64-bit) | | Timestamp (64-bit) |
| | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
. Signature (variable length) . . Signature (variable length) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_SIGNATURE (TBA3). option-code OPTION_SIGNATURE (TBA3).
option-len 12 + Length of Signature field in octets. option-len 10 + Length of Signature field in octets.
HA-id Hash Algorithm id. The hash algorithm is used for HA-id Hash Algorithm id. The hash algorithm is used for
computing the signature result. This design is computing the signature result. This design is
adopted in order to provide hash algorithm agility. adopted in order to provide hash algorithm agility.
The value is from the Hash Algorithm for Secure The value is from the Hash Algorithm for Secure
DHCPv6 registry in IANA. The support of SHA-256 is DHCPv6 registry in IANA. The support of SHA-256 is
mandatory. A registry of the initial assigned values mandatory. A registry of the initial assigned values
is defined in Section 8. is defined in Section 8.
SA-id Signature Algorithm id. The signature algorithm is SA-id Signature Algorithm id. The signature algorithm is
skipping to change at page 9, line 48 skipping to change at page 10, line 27
option (fill the signature field with zeroes) option (fill the signature field with zeroes)
except for the Authentication Option. except for the Authentication Option.
The signature filed MUST be padded, with all 0, to The signature filed MUST be padded, with all 0, to
the next octet boundary if its size is not an even the next octet boundary if its size is not an even
multiple of 8 bits. The padding length depends on multiple of 8 bits. The padding length depends on
the signature algorithm, which is indicated in the the signature algorithm, which is indicated in the
SA-id field. SA-id field.
Note: if both signature and authentication option are presented, Note: if both signature and authentication option are presented,
signature option does not protect authentication option. It is signature option does not protect the Authentication Option. It
because both needs to apply hash algorithm to whole message, so there allows to be created after signature has been calculated and filled
must be a clear order and there could be only one last-created with the valid signature. It is because both needs to apply hash
option. In order to avoid update RFC3315 because of changing auth algorithm to whole message, so there must be a clear order and there
option, the authors chose not include authentication option in the could be only one last-created option. In order to avoid update
signature. [RFC3315] because of changing auth option, the authors chose not
include authentication option in the signature.
5.4. Status Codes 5.4. Status Codes
o NotSupportAlgorithm (TBD4): indicates that the DHCPv6 server does o AlgorithmNotSupported (TBD4): indicates that the DHCPv6 server
not support algorthims that sender used. does not support algorithms that sender used.
o AuthFailNotSupportLoF (TBD5): indicates that the DHCPv6 client o AuthFailNotSupportLoF (TBD5): indicates that the DHCPv6 client
fails authentication check and the DHCPv6 server does not support fails authentication check and the DHCPv6 server does not support
the leaf of faith model the leaf of faith mode
o AuthFailSupportLoF (TBD6): indicates that the DHCPv6 client fails o AuthFailSupportLoF (TBD6): indicates that the DHCPv6 client fails
authentication check. Although the DHCPv6 server does support the authentication check. Although the DHCPv6 server does support the
leaf of faith, its list that stores public keys or unverifiable leaf of faith, its list that stores public keys or unverifiable
certificates in the leap of faith model currently exceeds. certificates in the leap of faith mode currently exceeds.
o SignitureFail (TBD7): indicates the message from DHCPv6 client o TimestampFail (TBD7): indicates the message from DHCPv6 client
fails the signiture check. fails the timstamp check.
o SignatureFail (TBD8): indicates the message from DHCPv6 client
fails the signature check.
6. Processing Rules and Behaviors 6. Processing Rules and Behaviors
This section only covers the scenario where both DHCPv6 client and This section only covers the scenario where both DHCPv6 client and
server are secure enabled. DHCPv6 server are secure enabled.
6.1. Processing Rules of Sender 6.1. Processing Rules of Sender
The sender of a Secure DHCPv6 message could be a DHCPv6 server or a The sender of a Secure DHCPv6 message could be a DHCPv6 server or a
DHCPv6 client. DHCPv6 client.
The node must have a public/private key pair in order to create The node must have a public/private key pair in order to create
Secure DHCPv6 messages. The node may have a certificate which is Secure DHCPv6 messages. The node may have a certificate which is
signed by a CA trusted by both sender and recipient. signed by a CA trusted by both sender and recipient.
To support Secure DHCPv6, the Secure DHCPv6 enabled sender MUST To support secure DHCPv6, the secure DHCPv6 enabled sender MUST
construct the DHCPv6 message following the rules defined in construct the DHCPv6 message following the rules defined in
[RFC3315]. [RFC3315].
A Secure DHCPv6 message, except for Relay-forward and Relay-reply A Secure DHCPv6 message, except for Relay-forward and Relay-reply
messages, MUST contain either a the Public Key or Certificate option, messages, MUST contain either a Public Key or a Certificate option,
which MUST contructed as explained in Section 5.1 or Section 5.2. which MUST be constructed as explained in Section 5.1 or Section 5.2.
A Secure DHCPv6 message, except for Relay-forward and Relay-reply A Secure DHCPv6 message, except for Relay-forward and Relay-reply
messages, MUST contain the Signature option, which MUST be messages, MUST contain one and only one Signature option, which MUST
constructed as explained in Section 5.3. It protects the message be constructed as explained in Section 5.3. It protects the message
header all DHCPv6 options except for the Authentication Option. header and all DHCPv6 options except for the Authentication Option.
Within the Signature option the Timestamp field SHOULD be set to the Within the Signature option the Timestamp field SHOULD be set to the
current time, according to sender's real time clock. current time, according to sender's real time clock.
A Relay-forward and relay-reply message MUST NOT contain any A Relay-forward and relay-reply message MUST NOT contain any
additional Public Key or Certificate option or Signature Option, additional Public Key or Certificate option or Signature Option,
aside from those present in the innermost encapsulated message from aside from those present in the innermost encapsulated message from
the client or server. the client or server.
If the sender is a DHCPv6 client, in the failure cases, it receives a If the sender is a DHCPv6 client, in the failure cases, it receives a
Reply message with an error status code. The error status code Reply message with an error status code. The error status code
indicates the failure reason on the server side. According to the indicates the failure reason on the server side. According to the
received status code, the client MAY take follow-up action: received status code, the client MAY take follow-up action:
o Upon receiving a NotSupportAlgorithm error status code, the client o Upon receiving a AlgorithmNotSupported error status code, the
MAY resend the message protected with the mandatory algorithms. client MAY resend the message protected with the mandatory
algorithms.
o Upon receiving an AuthFailNotSupportLoF error status code, the o Upon receiving an AuthFailNotSupportLoF error status code, the
client is not able to build up the secure communication with the client is not able to build up the secure communication with the
recipient. The client MAY switch to other certificate or public recipient. The client MAY switch to other certificate or public
key if it has. But it SHOULD NOT retry with the same certificate/ key if it has. But it SHOULD NOT retry with the same certificate/
public-key. public-key. It MAY retry with the same certificate/public-key
following normal retransmission routines defined in [RFC3315].
o Upon receiving an AuthFailSupportLoF error status code, the client o Upon receiving an AuthFailSupportLoF error status code, the client
is not able to build up the secure communication with the is not able to build up the secure communication with the
recipient. The client MAY switch to other certificate or public recipient. The client MAY switch to other certificate or public
key if it has. The client MAY retry with the same certificate/ key if it has. The client MAY retry with the same certificate/
public-key later. public-key following normal retransmission routines defined in
[RFC3315].
o Upon receiving a SignitureFail error status code, the client MAY o Upon receiving a TimestampFail error status code, the client MAY
resend the message. fall back to unsecured mode.
o Upon receiving a SignatureFail error status code, the client MAY
resend the message following normal retransmission routines
defined in [RFC3315].
6.2. Processing Rules of Recipient 6.2. Processing Rules of Recipient
The recipient of a Secure DHCPv6 message could be a DHCPv6 server or The recipient of a Secure DHCPv6 message could be a DHCPv6 server or
a DHCPv6 client. In the failure cases, both DHCPv6 server and client a DHCPv6 client. In the failure cases, both DHCPv6 server and client
SHOULD NOT process received message, and the server SHOULD reply a SHOULD NOT process received message, and the server SHOULD reply a
correspondent error status could, while the client does nothing. correspondent error status code, while the client does nothing. The
specific behavior depends on the configured local policy.
When receiving a DHCPv6 message, except for Relay-Forward and Relay- When receiving a DHCPv6 message, except for Relay-Forward and Relay-
Reply messages, a Secure DHCPv6 enabled recipient SHOULD discard the Reply messages, a secure DHCPv6 enabled recipient SHOULD discard the
DHCPv6 message if the Signature option is absent, or both the Public DHCPv6 message if the Signature option is absent, or multiple
Key and Certificate option is absent, or both the Public Key and Signature option is presented, or both the Public Key and Certificate
Certificate option are presented. In such failure, the DHCPv6 server options are absent, or both the Public Key and Certificate option are
SHOULD reply an UnspecFail (value 1, [RFC3315]) error status code. presented. In such failure, the DHCPv6 server SHOULD reply an
If all three options are absent, the sender MAY be legacy node or in UnspecFail (value 1, [RFC3315]) error status code. If all three
unsecure model, then, the recipient MAY fall back the unsecure DHCPv6 options are absent, the sender MAY be legacy node or in unsecured
model if its local policy allows. mode, then, the recipient MAY fall back to the unsecured DHCPv6 mode
if its local policy allows.
The recipient SHOULD first check the support of algorthims that The recipient SHOULD first check the support of algorithms that
sender used. If all algorthims are supported, the recipient then sender used. If all algorithms are supported, the recipient then
checks the authority of this sender. If not, the message is dropped. checks the authority of this sender. If not, the message is dropped.
In such failure, the DHCPv6 server SHOULD reply a
In such failure, the DHCPv6 server SHOULD reply a NotSupportAlgorithm AlgorithmNotSupported error status code, defined in Section 5.4, back
error status code, defined in Section 5.4, back to the client.. to the client.
If the sender uses certificate, the recipient SHOULD validate the If the sender uses certificate, the recipient SHOULD validate the
sender's certificate following the rules defined in [RFC5280]. An sender's certificate following the rules defined in [RFC5280]. An
implementation may create a local trust certificate record for a implementation may create a local trust certificate record for a
verified certificate in order to avoid repeated verfication procedure verified certificate in order to avoid repeated verification
in the future. A sender certificate that finds a match in the local procedure in the future. A sender certificate that finds a match in
trust certificate list are treated as verified. A fast search index the local trust certificate list is treated as verified. A fast
may be created for this list. search index may be created for this list.
If the sender uses a public key, the recipient SHOULD validate it by If the sender uses a public key, the recipient SHOULD validate it by
finding a match public key from the local trust public key list, finding a matching public key from the local trust public key list,
which is pre-configured or recorded from previous communications. A which is pre-configured or recorded from previous communications. A
local trust public key list is a data table maintained by the local trust public key list is a data table maintained by the
recipient. It restores public keys from all trustworthy senders. A recipient. It restores public keys from all trustworthy senders. A
fast search index may be created for this list. fast search index may be created for this list.
The recipient may choose to further process the message from a sender The recipient may choose to further process the message from a sender
for which no authentication information exists, either non-matched for which no authentication information exists, either non-matched
public key or certificate cannot be verified. By recording the public key or certificate cannot be verified. By recording the
public key or unverifiable certificate that was used by the sender, public key or unverifiable certificate that was used by the sender,
when the first time it is seen, the recipient can make a leap of when the first time it is seen, the recipient can make a leap of
faith (LoF) that the sender is trustworthy. If no evidence to the faith (LoF) that the sender is trustworthy. If no evidence to the
contrary surfaces, the recipient can then validate the sender as contrary surfaces, the recipient can then validate the sender as
trustworthy for subsequent message exchanges. In opposite, once the trustworthy for subsequent message exchanges. In opposite, once the
recipient has determined that it is being attacked, it can either recipient has determined that it is being attacked, it can either
forget that key, or remember that key in a blacklist and drop further forget that key, or remember that key in a blacklist and drop further
packets associated with that key. packets associated with that key.
If recipient does not support the leap of faith model, the message If recipient does not support the leap of faith mode, the message
that fails authentication check MUST be dropped. In such failure, that fails authentication check MUST be dropped. In such failure,
the DHCPv6 server SHOULD reply an AuthFailNotSupportLoF error status the DHCPv6 server SHOULD reply an AuthFailNotSupportLoF error status
code, defined in Section 5.4, back to the client. code, defined in Section 5.4, back to the client.
On the recipient that supports the leap of faith model, the number of On the recipient that supports the leap of faith mode, the number of
cached public keys or unverifiable certificates MUST be limited in cached public keys or unverifiable certificates MAY be limited in
order to protect against resource exhaustion attacks. If the order to protect against resource exhaustion attacks. If the
recipient's list that stores public keys or unverifiable certificates recipient's list that stores public keys or unverifiable certificates
in the leap of faith model exceeds, the message that fails in the leap of faith mode exceeds, the message that fails
authentication check MUST be dropped. In such failure, the DHCPv6 authentication check MUST be dropped. In such failure, the DHCPv6
server SHOULD reply an AuthFailNotSupportLoF error status code, server SHOULD reply an AuthFailNotSupportLoF error status code,
defined in Section 5.4, back to the client. The resource releasing defined in Section 5.4, back to the client. The resource releasing
policy against exceeding situations is out of scope. policy against exceeding situations is out of scope. Giving the
complexity, the key rollover mechanism is out of scope of this
document.
At this point, the recipient has either recognized the authentication At this point, the recipient has either recognized the authentication
of the sender, or decided to attempt a leap of faith. The recipient of the sender, or decided to attempt a leap of faith. The recipient
MUST now authenticate the sender by verifying the Signature and MUST now authenticate the sender by verifying the Signature and
checking timestamp. The order of two procedures is left as an checking timestamp (see details in Section 6.4). The order of two
implementation decision. It is RECOMMENDED to check timestamp first, procedures is left as an implementation decision. It is RECOMMENDED
because signature verification is much more computationally to check timestamp first, because signature verification is much more
expensive. computationally expensive.
The signature field verification MUST show that the signature has The signature field verification MUST show that the signature has
been calculated as specified in Section 5.3. Only the messages that been calculated as specified in Section 5.3. Only the messages that
get through both the signature verifications and timestamp check are get through both the signature verifications and timestamp check are
accepted as secured DHCPv6 messages and continue to be handled for accepted as secured DHCPv6 messages and continue to be handled for
their contained DHCPv6 options as defined in [RFC3315]. Messages their contained DHCPv6 options as defined in [RFC3315]. Messages
that do not pass the above tests MUST be discarded or treated as that do not pass the above tests MUST be discarded or treated as
unsecure messages. In the signature verification failure case, the unsecured messages. In the case the recipient is DHCPv6 server, the
DHCPv6 server SHOULD reply a SignatureFail error status code, defined DHCPv6 server SHOULD reply a SignatureFail error status code, defined
in Section 5.4, back to the client. in Section 5.4, for the signature verification failure, or a
TimestampFail error status code, defined in Section 5.4, for the
timestamp check failure, back to the client.
Furthermore, the node that supports the verification of the Secure Furthermore, the node that supports the verification of the Secure
DHCPv6 messages MAY record the following information: DHCPv6 messages MAY record the following information:
Minbits The minimum acceptable key length for public keys. An upper Minbits The minimum acceptable key length for public keys. An upper
limit MAY also be set for the amount of computation needed when limit MAY also be set for the amount of computation needed when
verifying packets that use these security associations. The verifying packets that use these security associations. The
appropriate lengths SHOULD be set according to the signature appropriate lengths SHOULD be set according to the signature
algorithm and also following prudent cryptographic practice. For algorithm and also following prudent cryptographic practice. For
example, minimum length 1024 and upper limit 2048 may be used for example, minimum length 1024 and upper limit 2048 may be used for
RSA [RSA]. RSA [RSA].
A Relay-forward or Relay-reply message with any Public Key, A Relay-forward or Relay-reply message with any Public Key,
Certificate or the Signature option is invilad. The message MUST be Certificate or the Signature option is invalid. The message MUST be
discarded silently. discarded silently.
6.3. Processing Rules of Relay Agent 6.3. Processing Rules of Relay Agent
To support Secure DHCPv6, relay agents just need to follow the same To support Secure DHCPv6, relay agents just need to follow the same
processing rules defined in [RFC3315]. There is nothing more the processing rules defined in [RFC3315]. There is nothing more the
relay agents have to do, either verify the messages from client or relay agents have to do, either verify the messages from client or
server, or add any secure DHCPv6 options. Actually, by definition in server, or add any secure DHCPv6 options. Actually, by definition in
this document, relay agents MUST NOT add any secure DHCPv6 options. this document, relay agents SHOULD NOT add any secure DHCPv6 options.
6.4. Timestamp Check 6.4. Timestamp Check
Recipients SHOULD be configured with an allowed timestamp Delta Recipients SHOULD be configured with an allowed timestamp Delta
value, a "fuzz factor" for comparisons, and an allowed clock drift value, a "fuzz factor" for comparisons, and an allowed clock drift
parameter. The recommended default value for the allowed Delta is parameter. The recommended default value for the allowed Delta is
300 seconds (5 minutes); for fuzz factor 1 second; and for clock 300 seconds (5 minutes); for fuzz factor 1 second; and for clock
drift, 0.01 second. drift, 0.01 second.
Note: the Timestamp mechanism is based on the assumption that Note: the Timestamp mechanism is based on the assumption that
communication peers have rough synchronized clocks, with certain communication peers have roughly synchronized clocks, with certain
allowed clock drift. So, accurate clock is not necessary. If one allowed clock drift. So, accurate clock is not necessary. If one
has a clock too far from the current time, the timestamp mechanism has a clock too far from the current time, the timestamp mechanism
would not work. would not work.
To facilitate timestamp checking, each recipient SHOULD store the To facilitate timestamp checking, each recipient SHOULD store the
following information for each sender, from which at least one following information for each sender, from which at least one
accepted secure DHCPv6 message is successfully verified (for both accepted secure DHCPv6 message is successfully verified (for both
timestamp check and signature verification): timestamp check and signature verification):
o The receive time of the last received and accepted DHCPv6 message. o The receive time of the last received and accepted DHCPv6 message.
This is called RDlast. This is called RDlast.
o The timestamp in the last received and accepted DHCPv6 message. o The timestamp in the last received and accepted DHCPv6 message.
This is called TSlast. This is called TSlast.
An verified (for both timestamp check and signature verification) A verified (for both timestamp check and signature verification)
secure DHCPv6 message initiates the update of the above variables in secure DHCPv6 message initiates the update of the above variables in
the recipient's record. the recipient's record.
Recipients MUST check the Timestamp field as follows: Recipients MUST check the Timestamp field as follows:
o When a message is received from a new peer (i.e., one that is not o When a message is received from a new peer (i.e., one that is not
stored in the cache), the received timestamp, TSnew, is checked, stored in the cache), the received timestamp, TSnew, is checked,
and the message is accepted if the timestamp is recent enough to and the message is accepted if the timestamp is recent enough to
the reception time of the packet, RDnew: the reception time of the packet, RDnew:
skipping to change at page 15, line 11 skipping to change at page 16, line 7
An implementation MAY use some mechanism such as a timestamp cache to An implementation MAY use some mechanism such as a timestamp cache to
strengthen resistance to replay attacks. When there is a very large strengthen resistance to replay attacks. When there is a very large
number of nodes on the same link, or when a cache filling attack is number of nodes on the same link, or when a cache filling attack is
in progress, it is possible that the cache holding the most recent in progress, it is possible that the cache holding the most recent
timestamp per sender will become full. In this case, the node MUST timestamp per sender will become full. In this case, the node MUST
remove some entries from the cache or refuse some new requested remove some entries from the cache or refuse some new requested
entries. The specific policy as to which entries are preferred over entries. The specific policy as to which entries are preferred over
others is left as an implementation decision. others is left as an implementation decision.
7. Security Considerations 7. Deployment Consideration
This document defines two levels of authentication: full
authentication based on certificate or pre-shared key verification
and weaker authentication based on leap-of-faith (LoF). As a
mechanism, both levels can be applied on servers and clients.
Depending on the details of expected threats and other constraints,
some cases may have limited applicability. This section discusses
such details.
7.1. Authentication on a client
For clients, DHCP authentication generally means authenticating the
server (the sender of DHCP messages) and verifying message integrity.
This is satisfied with full authentication. Due to the configuration
overhead, however, full authentication may not always be feasible.
It would still be viable in a controlled environment with skilled
staff, such as a corporate intranet.
If LoF is used, message integrity is provided but there is a chance
for the client to incorrectly trust a malicious server at the
beginning of the first session with the server (and therefore keep
trusting it thereafter). But LoF guarantees the subsequent messages
are sent by the same server that sent the public key, and therefore
narrows the attack scope. This may make sense if the network can be
reasonably considered secure and requesting pre-configuration is
deemed to be infeasible. A small home network would be an example of
such cases.
For environments that are neither controlled nor really trustworthy,
such as a network cafe, full authentication wouldn't be feasible due
to configuration overhead, while pure LoF, i.e. silently trusting the
server at the first time, would be too insecure. But some
middleground might be justified, such as requiring human intervention
at the point of LoF.
7.2. Authentication on a server
As for authentication on a server, there are several different
scenarios to consider, each of which has different applicability
issues.
A server may have to selectively serve a specific client or deny
specific clients depending on the identify of the client. This will
require full authentication, since if the server allows LoF any
malicious user can pretend to be a new legitimate client. Also, the
use of certification wouldn't be feasible in this case, since it's
less likely for all such clients to have valid (and generally
different) certificates. So the applicable case may be limited, but
a controlled environment with skilled staff and a specifically
expected set of clients such as a corporate intranet may still find
it useful and viable.
A server can prevent an attack on the DHCP session with an existing
client from a malicious client, e.g., by sending a bogus Release
message: the server would remember the original client's public key
at the beginning of the DHCP session and authenticate subsequent
messages (and their sender). Neither full authentication nor LoF is
needed for this purpose, since the server does not have to trust the
public key itself. So this can be generally used for any usage of
DHCP.
A server can prevent an attack by a malicious client that pretends to
be a valid past client and tries to establish a new DHCP session
(whether this is a real security threat may be a subject of debate,
but this is probably at least annoying). This is similar to the
first scenario, but full authentication may not necessarily be
required; since the purpose is to confirm a returning client has the
same identify as a valid past client, the server only has to remember
the client's public key at the first time. So LoF can be used at the
risk of allowing a malicious client to mount this attack before the
initial session with a valid client. An uncontrolled, but reasonably
reliable network like a home network may use this defense with LoF.
8. Security Considerations
This document provides new security features to the DHCPv6 protocol. This document provides new security features to the DHCPv6 protocol.
Using public key based security mechanism and its verification Using public key based security mechanism and its verification
mechanism in DHCPv6 message exchanging provides the authentication mechanism in DHCPv6 message exchanging provides the authentication
and data integrity protection. Timestamp mechanism provides anti- and data integrity protection. Timestamp mechanism provides anti-
replay function. replay function.
The Secure DHCPv6 mechanism is based on the pre-condition that the The Secure DHCPv6 mechanism is based on the pre-condition that the
recipient knows the public key of senders or the sender's certificate recipient knows the public key of senders or the sender's certificate
can be verified through a trust CA. It prevents DHCPv6 server can be verified through a trust CA. It prevents DHCPv6 server
spoofing. The clients may decline the DHCPv6 messages from unknown/ spoofing. The clients may discard the DHCPv6 messages from unknown/
unverified servers, which may be fake servers; or may prefer DHCPv6 unverified servers, which may be fake servers; or may prefer DHCPv6
messages from known/verified servers over unsigned messages or messages from known/verified servers over unsigned messages or
messages from unknown/unverified servers. The pre-configuration messages from unknown/unverified servers. The pre-configuration
operation also needs to be protected, which is out of scope. The operation also needs to be protected, which is out of scope. The
deployment of PKI is also out of scope. deployment of PKI is also out of scope.
However, when a DHCPv6 client first encounters a new public key or a However, when a DHCPv6 client first encounters a new public key or a
new unverifiable certificate, it can make a leap of faith. If the new unverifiable certificate, it can make a leap of faith. If the
DHCPv6 server that used that public key or unverifiable certificate DHCPv6 server that used that public key or unverifiable certificate
is in fact legitimate, then all future communication with that DHCPv6 is in fact legitimate, then all future communication with that DHCPv6
skipping to change at page 16, line 14 skipping to change at page 18, line 37
A window of vulnerability for replay attacks exists until the A window of vulnerability for replay attacks exists until the
timestamp expires. Secure DHCPv6 nodes are protected against replay timestamp expires. Secure DHCPv6 nodes are protected against replay
attacks as long as they cache the state created by the message attacks as long as they cache the state created by the message
containing the timestamp. The cached state allows the node to containing the timestamp. The cached state allows the node to
protect itself against replayed messages. However, once the node protect itself against replayed messages. However, once the node
flushes the state for whatever reason, an attacker can re-create the flushes the state for whatever reason, an attacker can re-create the
state by replaying an old message while the timestamp is still valid. state by replaying an old message while the timestamp is still valid.
In addition, the effectiveness of timestamps is largely dependent In addition, the effectiveness of timestamps is largely dependent
upon the accuracy of synchronization between communicating nodes. upon the accuracy of synchronization between communicating nodes.
However, how the two communcating nodes can be synchronized is out of However, how the two communicating nodes can be synchronized is out
scope of this work. of scope of this work.
Attacks against time synchronization protocols such as NTP [RFC5905] Attacks against time synchronization protocols such as NTP [RFC5905]
may cause Secure DHCPv6 nodes to have an incorrect timestamp value. may cause Secure DHCPv6 nodes to have an incorrect timestamp value.
This can be used to launch replay attacks, even outside the normal This can be used to launch replay attacks, even outside the normal
window of vulnerability. To protect against these attacks, it is window of vulnerability. To protect against these attacks, it is
recommended that Secure DHCPv6 nodes keep independently maintained recommended that Secure DHCPv6 nodes keep independently maintained
clocks or apply suitable security measures for the time clocks or apply suitable security measures for the time
synchronization protocols. synchronization protocols.
8. IANA Considerations 9. IANA Considerations
This document defines three new DHCPv6 [RFC3315] options. The IANA This document defines three new DHCPv6 [RFC3315] options. The IANA
is requested to assign values for these three options from the DHCP is requested to assign values for these three options from the DHCPv6
Option Codes table of the DHCPv6 Parameters registry maintained in Option Codes table of the DHCPv6 Parameters registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters. The three options http://www.iana.org/assignments/dhcpv6-parameters. The three options
are: are:
The Public Key Option (TBA1), described in Section 5.1. The Public Key Option (TBA1), described in Section 5.1.
The Certificate Option (TBA2), described in Section 5.2. The Certificate Option (TBA2), described in Section 5.2.
The Signature Option (TBA3), described in Section 5.3. The Signature Option (TBA3), described in Section 5.3.
The IANA is also requested to add two new registry tables to the The IANA is also requested to add two new registry tables to the
DHCPv6 Parameters registry maintained in http://www.iana.org/ DHCPv6 Parameters registry maintained in
assignments/dhcpv6-parameters. The two tables are the Hash Algorithm http://www.iana.org/assignments/dhcpv6-parameters. The two tables
for Secure DHCPv6 table and the Signature Algorithm for Secure DHCPv6 are the Hash Algorithm for Secure DHCPv6 table and the Signature
table. Algorithm for Secure DHCPv6 table.
Initial values for these registries are given below. Future Initial values for these registries are given below. Future
assignments are to be made through Standards Action [RFC5226]. assignments are to be made through Standards Action [RFC5226].
Assignments for each registry consist of a name, a value and a RFC Assignments for each registry consist of a name, a value and a RFC
number where the registry is defined. number where the registry is defined.
Hash Algorithm for Secure DHCPv6. The values in this table are Hash Algorithm for Secure DHCPv6. The values in this table are 8-bit
16-bit unsigned integers. The following initial values are assigned unsigned integers. The following initial values are assigned for
for Hash Algorithm for Secure DHCPv6 in this document: Hash Algorithm for Secure DHCPv6 in this document:
Name | Value | RFCs Name | Value | RFCs
-------------------+---------+-------------- -------------------+---------+--------------
Reserved | 0x0000 | this document SHA-1 | 0x01 | this document
SHA-1 | 0x0001 | this document SHA-256 | 0x02 | this document
SHA-256 | 0x0002 | this document SHA-512 | 0x03 | this document
SHA-512 | 0x0003 | this document
Signature Algorithm for Secure DHCPv6. The values in this table are Signature Algorithm for Secure DHCPv6. The values in this table are
16-bit unsigned integers. The following initial values are assigned 8-bit unsigned integers. The following initial values are assigned
for Signature Algorithm for Secure DHCPv6 in this document: for Signature Algorithm for Secure DHCPv6 in this document:
Name | Value | RFCs Name | Value | RFCs
-------------------+---------+-------------- -------------------+---------+--------------
Reserved | 0x0000 | this document RSASSA-PKCS1-v1_5 | 0x01 | this document
RSASSA-PKCS1-v1_5 | 0x0001 | this document
IANA is requested to assign the following new DHCPv6 Status Codes, IANA is requested to assign the following new DHCPv6 Status Codes,
defined in Section 5.4, in the DHCPv6 Parameters registry maintained defined in Section 5.4, in the DHCPv6 Parameters registry maintained
in http://www.iana.org/assignments/dhcpv6-parameters: in http://www.iana.org/assignments/dhcpv6-parameters:
Code | Name | Reference Code | Name | Reference
---------+-----------------------+-------------- ---------+-----------------------+--------------
TBD4 | NotSupportAlgorithm | this document TBD4 | AlgorithmNotSupported | this document
TBD5 | AuthFailNotSupportLoF | this document TBD5 | AuthFailNotSupportLoF | this document
TBD6 | AuthFailSupportLoF | this document TBD6 | AuthFailSupportLoF | this document
TBD7 | SignitureFail | this document TBD7 | TimestampFail | this document
TBD8 | SignatureFail | this document
9. Acknowledgements 10. Acknowledgments
The authors would like to thank Bernie Volz, Ted Lemon, Ralph Droms, The authors would like to thank Bernie Volz, Ted Lemon, Ralph Droms,
Jari Arkko, Sean Turner, Stephen Kent, Thomas Huth, David Schumacher, Jari Arkko, Sean Turner, Stephen Kent, Thomas Huth, David Schumacher,
Francis Dupont, Tomek Mrugalski, Gang Chen, Qi Sun, Suresh Krishnan Francis Dupont, Tomek Mrugalski, Gang Chen, Qi Sun, Suresh Krishnan,
and other members of the IETF DHC working groups for their valuable Tatuya Jinmei and other members of the IETF DHC working groups for
comments. their valuable comments.
This document was produced using the xml2rfc tool [RFC2629]. This document was produced using the xml2rfc tool [RFC2629].
10. Change log [RFC Editor: Please remove] 11. Change log [RFC Editor: Please remove]
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 considation for large DHCPv6
message transmission. Added TimestampFail error code. Refined the
retransmission rules. 2014-06-18.
draft-ietf-dhc-sedhcpv6-02: addressed comments (applicability draft-ietf-dhc-sedhcpv6-02: addressed comments (applicability
statement, redesign the error codes and their logic) from IETF89 DHC statement, redesign the error codes and their logic) from IETF89 DHC
WG meeting and volunteer reviewers . 2014-04-14. WG meeting and volunteer reviewers. 2014-04-14.
draft-ietf-dhc-sedhcpv6-01: addressed comments from IETF88 DHC WG draft-ietf-dhc-sedhcpv6-01: addressed comments from IETF88 DHC WG
meeting. Moved Dacheng Zhang from acknowledgement to be co-author. meeting. Moved Dacheng Zhang from acknowledgement to be co-author.
2014-02-14 2014-02-14.
draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19. draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19.
draft-jiang-dhc-sedhcpv6-02: removed protection between relay agent draft-jiang-dhc-sedhcpv6-02: removed protection between relay agent
and server due to complexity, following the comments from Ted Lemon, and server due to complexity, following the comments from Ted Lemon,
Bernie Volz. 2013-10-16. Bernie Volz. 2013-10-16.
draft-jiang-dhc-sedhcpv6-01: update according to review comments from draft-jiang-dhc-sedhcpv6-01: update according to review comments from
Ted Lemon, Bernie Volz, Ralph Droms. Separated Public Key/ Ted Lemon, Bernie Volz, Ralph Droms. Separated Public Key/
Certificate option into two options. Refined many detailed Certificate option into two options. Refined many detailed
processes. 2013-10-08. processes. 2013-10-08.
draft-jiang-dhc-sedhcpv6-00: original version, this draft is a draft-jiang-dhc-sedhcpv6-00: original version, this draft is a
replacement of draft-ietf-dhc-secure-dhcpv6, which reached IESG and replacement of draft-ietf-dhc-secure-dhcpv6, which reached IESG and
dead because of consideration regarding to CGA. The authors followed dead because of consideration regarding to CGA. The authors followed
the suggestion from IESG making a general public key based mechanism. the suggestion from IESG making a general public key based mechanism.
2013-06-29. 2013-06-29.
11. References 12. References
11.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, April 2002.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003. IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055,
June 2005.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4491] Leontiev, S. and D. Shefanovski, "Using the GOST R
34.10-94, GOST R 34.10-2001, and GOST R 34.11-94
Algorithms with the Internet X.509 Public Key
Infrastructure Certificate and CRL Profile", RFC 4491, May
2006.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008. (CRL) Profile", RFC 5280, May 2008.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010. Specification", RFC 5905, June 2010.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)", RFC "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
5996, September 2010. 5996, September 2010.
11.2. Informative References 12.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999. June 1999.
[RFC4270] Hoffman, P. and B. Schneier, "Attacks on Cryptographic [RFC4270] Hoffman, P. and B. Schneier, "Attacks on Cryptographic
Hashes in Internet Protocols", RFC 4270, November 2005. Hashes in Internet Protocols", RFC 4270, November 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
skipping to change at page 19, line 33 skipping to change at page 23, line 4
Email: jiangsheng@huawei.com Email: jiangsheng@huawei.com
Sean Shen Sean Shen
CNNIC CNNIC
4, South 4th Street, Zhongguancun 4, South 4th Street, Zhongguancun
Beijing 100190 Beijing 100190
P.R. China P.R. China
Email: shenshuo@cnnic.cn Email: shenshuo@cnnic.cn
Dacheng Zhang Dacheng Zhang
Huawei Technologies Co., Ltd Huawei Technologies Co., Ltd
Q14, Huawei Campus, No.156 Beiqing Road Q14, Huawei Campus, No.156 Beiqing Road
Hai-Dian District, Beijing, 100095 Hai-Dian District, Beijing, 100095
P.R. China P.R. China
Email: zhangdacheng@huawei.com Email: zhangdacheng@huawei.com
Tatuya Jinmei
WIDE Project
Japan
Email: jinmei@wide.ad.jp
 End of changes. 85 change blocks. 
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