draft-ietf-dhc-sedhcpv6-03.txt   draft-ietf-dhc-sedhcpv6-04.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: December 21, 2014 CNNIC Expires: April 2, 2015 CNNIC
D. Zhang D. Zhang
Huawei Technologies Co., Ltd Huawei Technologies Co., Ltd
T. Jinmei T. Jinmei
WIDE Project Infoblox Inc.
June 19, 2014 September 29, 2014
Secure DHCPv6 with Public Key Secure DHCPv6
draft-ietf-dhc-sedhcpv6-03 draft-ietf-dhc-sedhcpv6-04
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 being secured, DHCPv6 is
various attacks, particularly spoofing attacks. This document vulnerable to various attacks, particularly spoofing attacks. This
analyzes the security issues of DHCPv6 and specifies a Secure DHCPv6 document analyzes the security issues of DHCPv6 and specifies a
mechanism for communication between DHCPv6 clients and DHCPv6 Secure DHCPv6 mechanism for communications between DHCPv6 clients and
servers. This mechanism is based on public/private key pairs. The DHCPv6 servers. This document provides a DHCPv6 client/server
authority of the sender may depend on either pre-configuration authentication mechanism based on server's public/private key pairs
mechanism or Public Key Infrastructure. and client's certificates. The DHCPv6 message exchanges are
protected by the signature option and the timestamp option newly
defined in this document.
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
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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 December 21, 2014. This Internet-Draft will expire on April 2, 2015.
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.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language and Terminology . . . . . . . . . . . . 3 2. Requirements Language and Terminology . . . . . . . . . . . . 3
3. Security Overview of DHCPv6 . . . . . . . . . . . . . . . . . 3 3. Security Overview of DHCPv6 . . . . . . . . . . . . . . . . . 4
4. Overview of Secure DHCPv6 Mechanism with Public Key . . . . . 4 4. Overview of Secure DHCPv6 Mechanism with Public Key . . . . . 4
4.1. New Components . . . . . . . . . . . . . . . . . . . . . 6 4.1. New Components . . . . . . . . . . . . . . . . . . . . . 5
4.2. Support for algorithm agility . . . . . . . . . . . . . . 6 4.2. Support for Algorithm Agility . . . . . . . . . . . . . . 6
4.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 6
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 . . . . . . . . . . . . . . . . . . . 8 5.2. Certificate Option . . . . . . . . . . . . . . . . . . . 8
5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 9 5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 9
5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 10 5.4. Timestamp Option . . . . . . . . . . . . . . . . . . . . 10
5.5. Status Codes . . . . . . . . . . . . . . . . . . . . . . 11
6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 11 6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 11
6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 11 6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 11
6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 12 6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 12
6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 14 6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 14
6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 14 6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 15
7. Deployment Consideration . . . . . . . . . . . . . . . . . . 16 7. Deployment Consideration . . . . . . . . . . . . . . . . . . 16
7.1. Authentication on a client . . . . . . . . . . . . . . . 16 7.1. Authentication on a client . . . . . . . . . . . . . . . 16
7.2. Authentication on a server . . . . . . . . . . . . . . . 16 7.2. Authentication on a server . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17 8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19
11. Change log [RFC Editor: Please remove] . . . . . . . . . . . 20 11. Change log [RFC Editor: Please remove] . . . . . . . . . . . 20
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
12.1. Normative References . . . . . . . . . . . . . . . . . . 21 12.1. Normative References . . . . . . . . . . . . . . . . . . 21
12.2. Informative References . . . . . . . . . . . . . . . . . 22 12.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
The Dynamic Host Configuration ProtocoFl for IPv6 (DHCPv6, [RFC3315]) The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315])
enables DHCPv6 servers to pass configuration parameters. It offers enables DHCPv6 servers to pass configuration parameters and offers
configuration flexibility. If not secured, DHCPv6 is vulnerable to configuration flexibility. If not being secured, DHCPv6 is
various attacks, particularly spoofing attacks. vulnerable to 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. o anti-replay protection based on timestamps.
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 communications between relay agents, may be secured through the use
IPsec, as described in section 21.1 in [RFC3315]. of 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
generated public/private key pairs. It also integrates timestamps server's public/private key pairs and client's certificates. The
for anti-replay. The authentication procedure defined in this reason for such design and deployment consideration are discussed in
document may depend on either deployed Public Key Infrastructure Section 7. It also integrates message signatures for the integrity
(PKI, [RFC5280]) or pre-configured sender's public key. However, the and timestamps for anti-replay. The client authentication on server
deployment of PKI or pre-configuration is out of the scope. procedure defined in this document depends on deployed Public Key
Infrastructure (PKI, [RFC5280]). However, the deployment of PKI is
out of the scope.
Secure DHCPv6 is applicable in environments where physical security Secure DHCPv6 is applicable in environments where physical security
on the link is not assured (such as over wireless) and attacks on on the link is not assured (such as over wireless) and attacks on
DHCPv6 are a concern. DHCPv6 are a concern.
2. Requirements Language and Terminology 2. Requirements Language and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119] when they appear in ALL CAPS. When these words are not 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 ALL CAPS (such as "should" or "Should"), they have their usual
English meanings, and are not to be interpreted as [RFC2119] key English meanings, and are not to be interpreted as [RFC2119] key
words. words.
3. Security Overview of DHCPv6 3. Security Overview of DHCPv6
DHCPv6 is a client/server protocol that provides managed DHCPv6 is a client/server protocol that provides managed
configuration of devices. It enables DHCPv6 server to automatically configuration of devices. It enables a DHCPv6 server to
configure relevant network parameters on clients. In the basic automatically configure relevant network parameters on clients. In
DHCPv6 specification [RFC3315], security of DHCPv6 message can be the basic DHCPv6 specification [RFC3315], security of DHCPv6 messages
improved. can be improved.
The basic DHCPv6 specifications can optionally authenticate the The basic DHCPv6 specifications can optionally authenticate the
origin of messages and validate the integrity of messages using an origin of messages and validate the integrity of messages using an
authentication option with a symmetric key pair. [RFC3315] relies on authentication option with a symmetric key pair. [RFC3315] relies on
pre-established secret keys. For any kind of meaningful security, pre-established secret keys. For any kind of meaningful security,
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
skipping to change at page 4, line 27 skipping to change at page 4, line 37
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. configuration data needed at each host.
[RFC3315] provides an additional mechanism for preventing off-network [RFC3315] provides an additional mechanism for preventing off-network
timing attacks using the Reconfigure message: the Reconfigure Key timing attacks using the Reconfigure message: the Reconfigure Key
authentication method. However, this method provides no message authentication method. However, this method provides no message
integrity or source integrity check. This key is transmitted in integrity or source integrity check. This key is transmitted in
plaintext. plaintext.
In comparison, the public/private key security mechanism allows the In comparison, the security mechanism defined in this document allows
keys to be generated by the sender, and allows the public key the public key database on the client to be populated
database on the recipient to be populated opportunistically or opportunistically or manually, depending on the degree of confidence
manually, depending on the degree of confidence desired in a specific desired in a specific application. PKI security mechanism is simpler
application. PKI security mechanism is simpler in the local key 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 DHCPv6 client and a server mutually authenticate This document introduces a Secure DHCPv6 mechanism that uses
each other without previous key deployment, this document introduces signatures to secure the DHCPv6 protocol. In order to enable DHCPv6
the use of public/private key pair mechanism into DHCPv6, also with clients and DHCPv6 servers to perform mutual authentication without
timestamp. The authority of the sender may depend on either pre- previous key deployment, this solution provides a DHCPv6 client/
configuration mechanism or PKI. By combining with the signatures, server authentication mechanism based on server's public/private key
sender identity can be verified and messages protected. pairs and client's certificates: the server only accept the client
messages that are protected by the client certificate that is signed
This document introduces a Secure DHCPv6 mechanism that uses a by a trusted CA; a client can build up trust relationship with a
public/private key pair to secure the DHCPv6 protocol. In order to server for subsequent message exchanges based on leap of faith (LoF)
enable DHCPv6 clients and DHCPv6 servers to perform mutual mechanism. This purpose of this design is to simplify the
authentication, this solution provides two public key based precondition of deploying DHCPv6 authentication and provides limited
mechanisms with different security strengths. One is stronger and protection of DHCPv6 message.
only the certificate signed by a trusted CA or preconfigured public
key can be accepted. The other one, called as leap of faith (LoF)
mechanism, is relatively weak. It allows a client/server pair that
lacks essential trust relationship to build up their trust
relationship at run time for subsequent exchanges based on faith.
This design simplifies the precondition of deploying DHCPv6
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-
shared with the recipient, either opportunistically or through a
manual process. When using certificates, the sender has a
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
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 (only sent by
option and a signature option with a corresponding verification servers), a certificate option (only sent by clients), a signature
mechanism. Timestamp is integrated into signature options. A DHCPv6 option and a timestamp with corresponding verification mechanisms. A
message (from a server or a client), with either a public key or DHCPv6 message from a server is attached with a public key option,
certificate option, and carrying a digital signature, can be verified and carrying a digital signature and a timestamp option. It can be
by the recipient for both the timestamp and authentication, then verified by the client. The client processes the payload of the
process the payload of the DHCPv6 message only if the validation is DHCPv6 message only if the validation is successful. Reversely, a
successful. Because the sender can be a DHCPv6 server or a client, DHCPv6 message from a client is attached with a certificate option,
the end-to-end security protection can be from DHCPv6 servers to and also carrying a digital signature and a timestamp option. It can
clients or from clients to DHCPv6 servers. be verified by the server. The server processes the payload of the
DHCPv6 message only if the validation is successful. The end-to-end
security protection is bidirection that covers both from DHCPv6
servers to clients and from clients to DHCPv6 servers. Additionally,
the optional timestamp mechanism provides anti-replay protection.
The recipient may choose to further process the message from a sender By recording the public key that was used by the DHCPv6 server, when
for which no authentication information exists, either non-matched the first time it is seen, the DHCPv6 client can make a leap of faith
public key or certificate cannot be verified. By recording the that the server is trustworthy. If no evidence to the contrary
public key or unverifiable certificate that was used by the sender, surfaces, the client can then validate the server as trustworthy when
when the first time it is seen, the recipient can make a leap of it subsequently sees the same public key used to sign messages from
faith that the sender is trustworthy. If no evidence to the contrary the same server. In opposite, once the client has determined that it
surfaces, the recipient can then validate the sender as trustworthy is being attacked, it can either forget that server, or remember that
when it subsequently sees the same public key or certificate used to server in a blacklist and drop further packets associated with that
sign messages from the same sender. In opposite, once the recipient server.
has determined that it is being attacked, it can either forget that
sender, or remember that sender in a blacklist and drop further
packets associated with that sender.
This improves communication security of DHCPv6 messages. On the server DHCPv6 side, upon receiving the client's certificate,
the server asserts the validity of the certificate, for example
through PKI.
Secure DHCPv6 messages are commonly large. IP fragments [RFC2460] Secure DHCPv6 messages are commonly large. IPv6 fragments [RFC2460]
are highly possible. Hence, deployment of Secure DHCPv6 should also are highly possible. Hence, deployment of Secure DHCPv6 should also
consider the issues of IP fragment, PMTU, etc. Also, if there are consider the issues of IP fragment, PMTU, etc. Also, if there are
firewalls between secure DHCPv6 clients and secure DHCPv6 servers, it firewalls between secure DHCPv6 clients and secure DHCPv6 servers, it
is RECOMMENDED that the firewalls are configureed to pass ICMP Packet is RECOMMENDED that the firewalls are configured to pass ICMP Packet
Too Big messages [RFC4443]. 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 server generates a public/private key pair. A DHCPv6 option
defined that carries the public key. that carries the public key is defined.
The node may also obtain a certificate from a Certificate o The client obtains a certificate from a Certificate Authority that
Authority that can be used to establish the trustworthiness of the can be used to establish the trustworthiness with the server.
node. Another option is defined to carry the certificate. Another option is defined to carry the certificate.
Because the certificate contains the public key, there is never a
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 which is used by the
integrity of the DHCPv6 messages and authenticates the identity of receiver to verify the integrity of the DHCPv6 messages and then
the sender. the identity of the sender.
o A timestamp, to detect and prevent packet replay. The secure o A timestamp, to detect replayed packet. The secure DHCPv6 nodes
DHCPv6 nodes need to meet some accuracy requirements and be synced need to meet some accuracy requirements and be synced to global
to global time, while the timestamp checking mechanism allows a time, while the timestamp checking mechanism allows a configurable
configurable time value for clock drift. The real time provision time value for clock drift. The real time provision is out of
is out of scope. 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. A unilateral notification mechanism from sender to recipient. A
recipient MAY support various algorithms simultaneously, and the recipient MAY support various algorithms simultaneously, and the
differenet senders in a same administrative domain may be allowed to different senders in a same administrative domain may be allowed to
use various algorithms simultaneously. use various algorithms simultaneously.
If the recipient does not support the algorithm used by the sender, If the recipient does not support the algorithm used by the sender,
it cannot authenticate the message. In the client-to-server case, it cannot authenticate the message. In the client-to-server case,
the server SHOULD reply with a AlgorithmNotSupported status code the server SHOULD reply with an AlgorithmNotSupported status code
(defined in Section 5.4). Upon receiving this status code, the (defined in Section 5.5). Upon receiving this status code, the
client MAY resend the message protected with the mandatory algorithm client MAY resend the message protected with the mandatory algorithm
(defined in Section 5.3). (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
mode by sending secure DHCPv6 messages. If the recipient is secure mode by sending secure DHCPv6 messages. If the recipient is secure
DHCPv6 enabled server, their communication would be in secure mode. DHCPv6 enabled server, their communication would be in secure mode.
In the scenario where the secure DHCPv6 enabled client and server In the scenario where the secure DHCPv6 enabled client and server
fail to build up secure communication between them, the secure DHCPv6 fail to build up secure communication between them, the secure DHCPv6
enabled client MAY choose to send unsecured DHCPv6 message towards enabled client MAY choose to send unsecured DHCPv6 message towards
the server. the server according to its local policies.
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 all of does not support secure mechanism, the DHCPv6 server (for all of
known DHCPv6 implementations) would just omit or disregard unknown known DHCPv6 implementations) would just omit or disregard unknown
options (secure options defined in this document) and still process options (secure options defined in this document) and still process
the known options. The reply message would be unsecured, of course. the known options. The reply message would be unsecured, of course.
It is up to the local policy of the client whether to accept the It is up to the local policy of the client whether to accept the
messages. If the client accepts the unsecured messages from the messages. If the client accepts the unsecured messages from the
DHCPv6 server, the subsequent exchanges will be in the unsecured DHCPv6 server, the subsequent exchanges will be in the unsecured
mode. mode.
In the scenario where a legacy client sends an unsecured 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's policy requires the on the server policy. If the server's policy requires the
authentication, an UnspecFail (value 1, [RFC3315]) error status code, authentication, an UnspecFail (value 1, [RFC3315]) error status code,
SHOULD be returned. In such case, the client cannot build up the SHOULD be returned. In such case, the client cannot build up the
connection with the server. If the server has been configured to connection with the server. If the server has been configured to
support unsecured clients, the server would fall back to the support unsecured clients, the server MAY fall back to the unsecured
unsecured DHCPv6 mode, and reply unsecured messages toward the DHCPv6 mode, and reply unsecured messages toward the client;
client. The resources allocated for unsecured clients SHOULD be depending on the local policy, the server MAY continue to send the
separated and restricted. secured reply messages with the consumption of computing resource.
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 describes the extensions to DHCPv6. Four new options
The new options MUST be supported in the Secure DHCPv6 message have been defined. The new options MUST be supported in the Secure
exchange. DHCPv6 message 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 server. The
format of the Public Key option is described as follows: format of the Public Key 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_PK_PARAMETER | option-len | | OPTION_PK_PARAMETER | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. Public Key (variable length) . . Public Key (variable length) .
. . . .
skipping to change at page 8, line 31 skipping to change at page 8, line 31
(e.g., RSA, DSA, or Diffie-Hellman). The algorithm (e.g., RSA, DSA, or Diffie-Hellman). The algorithm
is identified using the AlgorithmIdentifier structure is identified using the AlgorithmIdentifier structure
specified in section 4.1.1.2, [RFC5280]. The object specified in section 4.1.1.2, [RFC5280]. The object
identifiers for the supported algorithms and the identifiers for the supported algorithms and the
methods for encoding the public key materials methods for encoding the public key materials
(public key and parameters) are specified in (public key and parameters) are specified in
[RFC3279], [RFC4055], and [RFC4491]. [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 client. 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. 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.
length of a certificate is various.
5.3. Signature Option 5.3. Signature Option
The Signature option allows public key-based signatures to be The Signature option allows a signature that is signed by the private
attached to a DHCPv6 message. The Signature option could be any key to be attached to a DHCPv6 message. The Signature option could
place within the DHCPv6 message. It protects the entire DHCPv6 be any place within the DHCPv6 message while it is logically created
header and options, including itself, except for the Authentication after the entire DHCPv6 header and options, except for the
Option. The format of the Signature option is described as follows: Authentication Option. It protects the entire DHCPv6 header and
options, including itself, except for the Authentication 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) |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
. Signature (variable length) . . Signature (variable length) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_SIGNATURE (TBA3). option-code OPTION_SIGNATURE (TBA3).
option-len 10 + Length of Signature field in octets. option-len 2 + 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
used for computing the signature result. This used for computing the signature result. This
design is adopted in order to provide signature design is adopted in order to provide signature
algorithm agility. The value is from the Signature algorithm agility. The value is from the Signature
Algorithm for Secure DHCPv6 registry in IANA. The Algorithm for Secure DHCPv6 registry in IANA. The
support of RSASSA-PKCS1-v1_5 is mandatory. A support of RSASSA-PKCS1-v1_5 is mandatory. A
registry of the initial assigned values is defined registry of the initial assigned values is defined
in Section 8. in Section 8.
Timestamp The current time of day (NTP-format timestamp
[RFC5905] in UTC (Coordinated Universal Time), a
64-bit unsigned fixed-point number, in seconds
relative to 0h on 1 January 1900.). It can reduce
the danger of replay attacks.
Signature A variable-length field containing a digital Signature A variable-length field containing a digital
signature. The signature value is computed with signature. The signature value is computed with
the hash algorithm and the signature algorithm, the hash algorithm and the signature algorithm,
as described in HA-id and SA-id. The signature as described in HA-id and SA-id. The signature
constructed by using the sender's private key constructed by using the sender's private key
protects the following sequence of octets: protects the following sequence of octets:
1. The DHCPv6 message header. 1. The DHCPv6 message header.
2. All DHCPv6 options including the Signature 2. All DHCPv6 options including the Signature
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 field 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 a
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 the Authentication Option. It signature option does not protect the Authentication Option. It
allows to be created after signature has been calculated and filled allows the Authentication Option be created after signature has been
with the valid signature. It is because both needs to apply hash calculated and filled with the valid signature. It is because both
algorithm to whole message, so there must be a clear order and there options need to apply hash algorithm to whole message, so there must
could be only one last-created option. In order to avoid update be a clear order and there could be only one last-created option. In
[RFC3315] because of changing auth option, the authors chose not order to avoid update [RFC3315] because of changing auth option, the
include authentication option in the signature. authors chose not include authentication option in the signature.
5.4. Status Codes 5.4. Timestamp Option
o AlgorithmNotSupported (TBD4): indicates that the DHCPv6 server The Timestamp option carries the current time on the sender. It adds
does not support algorithms that sender used. the anti-replay protection to the DHCPv6 messages. It is optional.
o AuthFailNotSupportLoF (TBD5): indicates that the DHCPv6 client 0 1 2 3
fails authentication check and the DHCPv6 server does not support 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
the leaf of faith mode +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_TIMESTAMP | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Timestamp (64-bit) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o AuthFailSupportLoF (TBD6): indicates that the DHCPv6 client fails option-code OPTION_TIMESTAMP (TBA4).
authentication check. Although the DHCPv6 server does support the
leaf of faith, its list that stores public keys or unverifiable option-len 8, in octets.
certificates in the leap of faith mode currently exceeds.
Timestamp The current time of day (NTP-format timestamp
[RFC5905] in UTC (Coordinated Universal Time), a
64-bit unsigned fixed-point number, in seconds
relative to 0h on 1 January 1900.). It can reduce
the danger of replay attacks.
5.5. Status Codes
o AlgorithmNotSupported (TBD5): indicates that the DHCPv6 server
does not support algorithms that sender used.
o AuthenticationFail (TBD6): indicates that the DHCPv6 client fails
authentication check.
o TimestampFail (TBD7): indicates the message from DHCPv6 client o TimestampFail (TBD7): indicates the message from DHCPv6 client
fails the timstamp check. fails the timestamp check.
o SignatureFail (TBD8): indicates the message from DHCPv6 client o SignatureFail (TBD8): indicates the message from DHCPv6 client
fails the signature check. 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
DHCPv6 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 server 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 client must have a certificate which is
signed by a CA trusted by both sender and recipient. signed by a CA trusted by both server and client.
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 Public Key or a Certificate option, messages, MUST contain either a Public Key or a Certificate option,
which MUST be constructed 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 one and only one Signature option, which MUST messages, MUST contain one and only one Signature option, which MUST
be constructed as explained in Section 5.3. It protects the message be constructed as explained in Section 5.3. It protects the message
header and 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
current time, according to sender's real time clock. A Secure DHCPv6 message, except for Relay-forward and Relay-reply
messages, MAY contain one and only one Timestamp option. The
Timestamp field SHOULD be set to the 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 or
aside from those present in the innermost encapsulated message from Timestamp Option, aside from those present in the innermost
the client or server. encapsulated messages from 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 AlgorithmNotSupported error status code, the o Upon receiving an AlgorithmNotSupported error status code, the
client MAY resend the message protected with the mandatory client SHOULD resend the message protected with the mandatory
algorithms. algorithms.
o Upon receiving an AuthFailNotSupportLoF error status code, the o Upon receiving an AuthenticationFail error status code, the client
client is not able to build up the secure communication with the
recipient. The client MAY switch to other certificate or public
key if it has. But it SHOULD NOT retry with the same certificate/
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
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 if it has.
key if it has. The client MAY retry with the same certificate/ But it SHOULD NOT retry with the same certificate. It MAY retry
public-key following normal retransmission routines defined in with the same certificate following normal retransmission routines
[RFC3315]. defined in [RFC3315].
o Upon receiving a TimestampFail error status code, the client MAY o Upon receiving a TimestampFail error status code, the client MAY
fall back to unsecured mode. fall back to unsecured mode, or resend the message without a
Timestamp option. However, the DHCP server MAY not accept the
message without a Timestamp option.
o Upon receiving a SignatureFail error status code, the client MAY o Upon receiving a SignatureFail error status code, the client MAY
resend the message following normal retransmission routines resend the message following normal retransmission routines
defined in [RFC3315]. 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, either DHCPv6 server or
SHOULD NOT process received message, and the server SHOULD reply a client SHOULD NOT process received message, and the server SHOULD
correspondent error status code, while the client does nothing. The reply a correspondent error status code, while the client does
specific behavior depends on the configured local policy. 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 any
DHCPv6 message if the Signature option is absent, or multiple DHCPv6 messages that meet any of the following conditions:
Signature option is presented, or both the Public Key and Certificate
options are absent, or both the Public Key and Certificate option are
presented. In such failure, the DHCPv6 server SHOULD reply an
UnspecFail (value 1, [RFC3315]) error status code. If all three
options are absent, the sender MAY be legacy node or in unsecured
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 algorithms that o the Signature option is absent,
sender used. If all algorithms are supported, the recipient then
checks the authority of this sender. If not, the message is dropped.
In such failure, the DHCPv6 server SHOULD reply a
AlgorithmNotSupported error status code, defined in Section 5.4, back
to the client.
If the sender uses certificate, the recipient SHOULD validate the o multiple Signature option is presented,
sender's certificate following the rules defined in [RFC5280]. An
implementation may create a local trust certificate record for a
verified certificate in order to avoid repeated verification
procedure in the future. A sender certificate that finds a match in
the local trust certificate list is treated as verified. A fast
search index may be created for this list.
If the sender uses a public key, the recipient SHOULD validate it by o the Public Key option is absent in the server-to-client message,
finding a matching public key from the local trust public key list, o the Certificate option is presented in the server-to-client
which is pre-configured or recorded from previous communications. A message,
local trust public key list is a data table maintained by the
recipient. It restores public keys from all trustworthy senders. A
fast search index may be created for this list.
The recipient may choose to further process the message from a sender o the Certificate option is absent in the client-to-server message,
for which no authentication information exists, either non-matched
public key or certificate cannot be verified. By recording the
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
faith (LoF) that the sender is trustworthy. If no evidence to the
contrary surfaces, the recipient can then validate the sender as
trustworthy for subsequent message exchanges. In opposite, once the
recipient has determined that it is being attacked, it can either
forget that key, or remember that key in a blacklist and drop further
packets associated with that key.
If recipient does not support the leap of faith mode, the message o the Public Key option is presented in the client-to-server
that fails authentication check MUST be dropped. In such failure, message.
the DHCPv6 server SHOULD reply an AuthFailNotSupportLoF error status
code, defined in Section 5.4, back to the client.
On the recipient that supports the leap of faith mode, the number of In such failure, if the recipient is a DHCPv6 server, the server
cached public keys or unverifiable certificates MAY be limited in SHOULD reply an UnspecFail (value 1, [RFC3315]) error status code.
order to protect against resource exhaustion attacks. If the If neither of the Signature, Public Key or Certificate options is
recipient's list that stores public keys or unverifiable certificates presented, the sender MAY be a legacy node or in unsecured mode,
in the leap of faith mode exceeds, the message that fails then, the recipient MAY fall back to the unsecured DHCPv6 mode if its
authentication check MUST be dropped. In such failure, the DHCPv6 local policy allows.
server SHOULD reply an AuthFailNotSupportLoF error status code,
defined in Section 5.4, back to the client. The resource releasing The recipient SHOULD first check the support of algorithms that
policy against exceeding situations is out of scope. Giving the sender used. If not pass, the message is dropped. In such failure,
complexity, the key rollover mechanism is out of scope of this if the recipient is a DHCPv6 server, the server SHOULD reply an
document. AlgorithmNotSupported error status code, defined in Section 5.5, back
to the client. If all algorithms are supported, the recipient then
checks the authority of this sender.
The DHCPv6 server SHOULD validate the client's certificate following
the rules defined in [RFC5280]. An implementation may create a local
trust certificate record for verified certificates in order to avoid
repeated verification procedure in the future. A client certificate
that finds a match in the local trust certificate list is treated as
verified. A fast search index may be created for this list.
The DHCPv6 client SHOULD validate it by finding a matching public key
from the local trust public key list, which is pre-configured or
recorded from previous communications. A local trust public key list
is a data table maintained by the recipient. It restores public keys
from all trustworthy senders. A fast search index may be created for
this list. The message that fails authentication check MUST be
dropped. In such failure, the DHCPv6 server SHOULD reply an
AuthenticationFail error status code, defined in Section 5.5, back to
the client.
The client MAY choose to further process messages from a server for
which there is no matched public key. By recording the public key,
when the first time it is seen, the client can make a leap of faith
(LoF) that the server is trustworthy. If no evidence to the contrary
surfaces, the client can then validate the server as trustworthy for
subsequent message exchanges. In opposite, once the client has
determined that it is being attacked, it can either forget that
public key, or remember that public key in a blacklist and drop
further packets associated with that public key.
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 drop the message. The recipient MUST
MUST now authenticate the sender by verifying the Signature and now authenticate the sender by verifying the signature and checking
checking timestamp (see details in Section 6.4). The order of two timestamp (see details in Section 6.4), if there is a Timestamp
procedures is left as an implementation decision. It is RECOMMENDED option. The order of two procedures is left as an implementation
to check timestamp first, because signature verification is much more decision. It is RECOMMENDED to check timestamp first, because
computationally expensive. signature verification is much more computationally expensive.
Depending on server's local policy, the message without a Timestamp
option MAY be acceptable or rejected. If the server rejects such a
message, a TimestampFail error status code, defined in Section 5.5,
should be sent back to the client.
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 (if
accepted as secured DHCPv6 messages and continue to be handled for there is a Timestamp option) are accepted as secured DHCPv6 messages
their contained DHCPv6 options as defined in [RFC3315]. Messages and continue to be handled for their contained DHCPv6 options as
that do not pass the above tests MUST be discarded or treated as defined in [RFC3315]. Messages that do not pass the above tests MUST
unsecured messages. In the case the recipient is DHCPv6 server, the be discarded or treated as unsecured messages. In the case the
DHCPv6 server SHOULD reply a SignatureFail error status code, defined recipient is DHCPv6 server, the DHCPv6 server SHOULD reply a
in Section 5.4, for the signature verification failure, or a SignatureFail error status code, defined in Section 5.5, for the
TimestampFail error status code, defined in Section 5.4, for the signature verification failure; or a TimestampFail error status code,
timestamp check failure, back to the client. defined in Section 5.5, 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
skipping to change at page 14, line 42 skipping to change at page 15, line 7
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 SHOULD 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 In order to check the Timestamp option, defined in Section 5.4,
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 roughly 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.
skipping to change at page 16, line 9 skipping to change at page 16, line 25
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. Deployment Consideration 7. Deployment Consideration
This document defines two levels of authentication: full This document defines two directions of authentication:
authentication based on certificate or pre-shared key verification authentication based on client's certificate and authentication based
and weaker authentication based on leap-of-faith (LoF). As a on leap-of-faith (LoF) to server's public key.
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 7.1. Authentication on a client
For clients, DHCP authentication generally means authenticating the For clients, DHCPv6 authentication generally means verifying whether
server (the sender of DHCP messages) and verifying message integrity. the sender of DHCP messages is a legal DHCPv6 server and verifying
whether the message has been modified during transmission. Because
This is satisfied with full authentication. Due to the configuration the client may have to validate the authentication in the condition
overhead, however, full authentication may not always be feasible. of without connectivity wider than link-local, authentication with
It would still be viable in a controlled environment with skilled certificates may not always be feasible. So, this document only
staff, such as a corporate intranet. sticks on Leaf of Faith model, to make sure the client talks to the
same previous server.
If LoF is used, message integrity is provided but there is a chance Message integrity is provided. But there is a chance for the client
for the client to incorrectly trust a malicious server at the to incorrectly trust a malicious server at the beginning of the first
beginning of the first session with the server (and therefore keep session with the server (and therefore keep trusting it thereafter).
trusting it thereafter). But LoF guarantees the subsequent messages But LoF guarantees the subsequent messages are sent by the same
are sent by the same server that sent the public key, and therefore previous server, and therefore narrows the attack scope. This may
narrows the attack scope. This may make sense if the network can be make sense if the network can be reasonably considered secure and
reasonably considered secure and requesting pre-configuration is requesting pre-configuration is deemed to be infeasible. A small
deemed to be infeasible. A small home network would be an example of home network would be an example of such cases.
such cases.
For environments that are neither controlled nor really trustworthy, For environments that are neither controlled nor really trustworthy,
such as a network cafe, full authentication wouldn't be feasible due such as a network cafe, while LoF model, i.e. silently trusting the
to configuration overhead, while pure LoF, i.e. silently trusting the server at the first time, would be too insecure. But some middle
server at the first time, would be too insecure. But some ground might be justified, such as requiring human intervention at
middleground might be justified, such as requiring human intervention the point of LoF.
at the point of LoF.
7.2. Authentication on a server 7.2. Authentication on a server
As for authentication on a server, there are several different As for authentication on a server, there are several different
scenarios to consider, each of which has different applicability scenarios to consider, each of which has different applicability
issues. issues. If the server allows LoF any malicious user can pretend to
be a new legitimate client. While the server can always be
A server may have to selectively serve a specific client or deny considered to have connectivity to validate certificate, it is
specific clients depending on the identify of the client. This will feasible to check client certificates.
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 Network administrators may wish to constrain the allocation of
be a valid past client and tries to establish a new DHCP session addresses to authorized hosts to avoid denial of service attacks in
(whether this is a real security threat may be a subject of debate, "hostile" environments where the network medium is not physically
but this is probably at least annoying). This is similar to the secured, such as wireless networks or college residence halls. A
first scenario, but full authentication may not necessarily be server may have to selectively serve a specific client or deny
required; since the purpose is to confirm a returning client has the specific clients depending on the identity of the client in a
same identify as a valid past client, the server only has to remember controlled environment, like a corporate intranet. But the support
the client's public key at the first time. So LoF can be used at the from skilled staff or administrator may be required to set up the
risk of allowing a malicious client to mount this attack before the clients.
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 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 client knows the public key of servers or the client'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 discard 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, it
new unverifiable certificate, it can make a leap of faith. If the can make a leap of faith. If the DHCPv6 server that used that public
DHCPv6 server that used that public key or unverifiable certificate key is in fact legitimate, then all future communication with that
is in fact legitimate, then all future communication with that DHCPv6 DHCPv6 server can be protected by storing the public key. This does
server can be protected by storing the public key or unverifiable not provide complete security, but it limits the opportunity to mount
certificate. This does not provide complete security, but it limits an attack on a specific DHCPv6 client to the first time it
the opportunity to mount an attack on a specific DHCPv6 client to the communicates with a new DHCPv6 server.
first time it communicates with a new DHCPv6 server. The number of
cached public keys or unverifiable certificates MUST be limited in
order to protect the DHCPv6 server against resource exhaustion
attacks.
Downgrade attacks cannot be avoided if nodes are configured to accept Downgrade attacks cannot be avoided if nodes are configured to accept
both secured and unsecured messages. A future specification may both secured and unsecured messages. A future specification may
provide a mechanism on how to treat unsecured DHCPv6 messages. provide a mechanism on how to treat unsecured DHCPv6 messages.
[RFC6273] has analyzed possible threats to the hash algorithms used [RFC6273] has analyzed possible threats to the hash algorithms used
in SEND. Since the Secure DHCPv6 defined in this document uses the in SEND. Since the Secure DHCPv6 defined in this document uses the
same hash algorithms in similar way to SEND, analysis results could same hash algorithms in similar way to SEND, analysis results could
be applied as well: current attacks on hash functions do not be applied as well: current attacks on hash functions do not
constitute any practical threat to the digital signatures used in the constitute any practical threat to the digital signatures used in the
signature algorithm in the Secure DHCPv6. signature algorithm in the Secure DHCPv6.
A server, whose local policy accepts messages without a Timestamp
option, may have to face the risk of replay attacks.
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 communicating nodes can be synchronized is out However, how the two communicating nodes can be synchronized is out
skipping to change at page 19, line 13 skipping to change at page 19, line 5
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 Timestamp Option (TBA4),described in Section 5.4.
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 DHCPv6 Parameters registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters. The two tables http://www.iana.org/assignments/dhcpv6-parameters. The two tables
are the Hash Algorithm for Secure DHCPv6 table and the Signature are the Hash Algorithm for Secure DHCPv6 table and the Signature
Algorithm for Secure DHCPv6 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.
skipping to change at page 19, line 43 skipping to change at page 19, line 37
Signature Algorithm for Secure DHCPv6. The values in this table are Signature Algorithm for Secure DHCPv6. The values in this table are
8-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
-------------------+---------+-------------- -------------------+---------+--------------
RSASSA-PKCS1-v1_5 | 0x01 | this document RSASSA-PKCS1-v1_5 | 0x01 | 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 5.5, 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 | AlgorithmNotSupported | this document TBD5 | AlgorithmNotSupported | this document
TBD5 | AuthFailNotSupportLoF | this document TBD6 | AuthenticationFail | this document
TBD6 | AuthFailSupportLoF | this document
TBD7 | TimestampFail | this document TBD7 | TimestampFail | this document
TBD8 | SignatureFail | this document TBD8 | SignatureFail | this document
10. Acknowledgments 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,
Tatuya Jinmei and other members of the IETF DHC working groups for Fred Templin and other members of the IETF DHC working groups for
their valuable comments. their valuable comments.
This document was produced using the xml2rfc tool [RFC2629]. This document was produced using the xml2rfc tool [RFC2629].
11. Change log [RFC Editor: Please remove] 11. Change log [RFC Editor: Please remove]
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 draft-ietf-dhc-sedhcpv6-03: addressed comments from WGLC. Added a
new section "Deployment Consideration". Corrected the Public Key new section "Deployment Consideration". Corrected the Public Key
Field in the Public Key Option. Added considation for large DHCPv6 Field in the Public Key Option. Added consideration for large DHCPv6
message transmission. Added TimestampFail error code. Refined the message transmission. Added TimestampFail error code. Refined the
retransmission rules. 2014-06-18. retransmission rules on clients. 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.
skipping to change at page 23, line 4 skipping to change at page 22, line 41
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 Tatuya Jinmei
WIDE Project Infoblox Inc.
Japan 3111 Coronado Drive
Santa Clara, CA
USA
Email: jinmei@wide.ad.jp Email: jinmei@wide.ad.jp
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