draft-ietf-dhc-sedhcpv6-01.txt   draft-ietf-dhc-sedhcpv6-02.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: August 18, 2014 CNNIC Expires: October 17, 2014 CNNIC
D. Zhang D. Zhang
Huawei Technologies Co., Ltd Huawei Technologies Co., Ltd
February 14, 2014 April 15, 2014
Secure DHCPv6 with Public Key Secure DHCPv6 with Public Key
draft-ietf-dhc-sedhcpv6-01 draft-ietf-dhc-sedhcpv6-02
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 client and server. This
mechanism is based on public/private key pairs. The authority of the mechanism is based on public/private key pairs. The authority of the
skipping to change at page 1, line 41 skipping to change at page 1, line 41
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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
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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 August 18, 2014. This Internet-Draft will expire on October 17, 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
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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. Secure DHCPv6 Overview . . . . . . . . . . . . . . . . . . . 4 4. Overview of Secure DHCPv6 Mechanism with Public Key . . . . . 4
4.1. New Components . . . . . . . . . . . . . . . . . . . . . 5 4.1. New Components . . . . . . . . . . . . . . . . . . . . . 5
4.2. Support for algorithm agility . . . . . . . . . . . . . . 5 4.2. Support for algorithm agility . . . . . . . . . . . . . . 6
5. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 6 4.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Public Key Option . . . . . . . . . . . . . . . . . . . . 6 5. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 7
5.2. Certificate Option . . . . . . . . . . . . . . . . . . . 6 5.1. Public Key Option . . . . . . . . . . . . . . . . . . . . 7
5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 7 5.2. Certificate Option . . . . . . . . . . . . . . . . . . . 7
5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 9 5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 8
6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 9 5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 9 6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 10
6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 10 6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 10
6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 11 6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 11
6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 12 6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. Change log [RFC Editor: Please remove] . . . . . . . . . . . 16 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 10. Change log [RFC Editor: Please remove] . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 16 11.1. Normative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 11.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
The Dynamic Host Configuration Protocol 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. 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
skipping to change at page 3, line 45 skipping to change at page 3, line 48
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 DHCPv6 server to automatically
configure relevant network parameters on clients. In the basic configure relevant network parameters on clients. In the basic
DHCPv6 specification [RFC3315], security of DHCPv6 message can be DHCPv6 specification [RFC3315], security of DHCPv6 message can be
improved. 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 authentication option with a symmetric key pair. [RFC3315] relies on
on pre-established secret keys. For any kind of meaningful pre-established secret keys. For any kind of meaningful security,
security, each DHCPv6 client would need to be configured with its each DHCPv6 client would need to be configured with its own secret
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, mechanisms. Firstly, the key management is done out of band, usually
usually through some manual process. For example, operators can through some manual process. For example, operators can set up a key
set up a key database for both servers and clients which the database for both servers and clients which the client obtains a key
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. [RFC3315] provides an
additional mechanism for preventing off-network timing attacks additional mechanism for preventing off-network timing attacks using
using the Reconfigure message: the Reconfigure Key authentication the Reconfigure message: the Reconfigure Key authentication method.
method. However, this method provides no message integrity or However, this method provides no message integrity or source
source integrity check. This key is transmitted in plaintext. integrity check. This key is transmitted in plaintext.
In comparison, the public/private key security mechanism allows In comparison, the public/private key security mechanism allows the
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 manually, depending on the degree of confidence desired in a specific
specific application. PKI security mechanism is simpler in the application. PKI security mechanism is simpler in the local key
local key management respect. management respect.
4. Secure DHCPv6 Overview 4. Overview of Secure DHCPv6 Mechanism with Public Key
To solve the above mentioned security issues, this document In order to enable a DHCP client and a server mutually authenticate
introduces the use of public/private key pair mechanism into DHCPv6, each other without previous key deployment, this document introduces
also with timestamp. The authority of the sender may depend on the use of public/private key pair mechanism into DHCPv6, also with
either pre-configuration mechanism or PKI. By combining with the timestamp. The authority of the sender may depend on either pre-
signatures, sender identity can be verified and messages protected. configuration mechanism or PKI. By combining with the signatures,
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 public
/private key pair to secure the DHCPv6 protocol. It has two modes; /private key pair to secure the DHCPv6 protocol. In order to enable
in both modes, the sender has a public/private key pair. In the DHCP clients and servers to perform mutual authentication, this
first mode, the public key of the sender is pre-shared with the solution provides two public key based mechanisms with different
recipient, either opportunistically or through a manual process. In security strengths. One is stronger and only the certificate signed
the second mode, the sender has a certificate for its public key, by a trusted CA or preconfigured public key can be accepted. The
signed by a Certificate Authority that is trusted by the recipient. other one, called as leap of faith (LoF) mechanism, is relatively
It is possible for the same public key to be used with different weak. It allows a client/server pair, that lacks essential trust
recipients in both modes. 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 soltuion, both public/private key pairs or
certificates are 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, a certificate
option and a signature options 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 or 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
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 that the sender is trustworthy. If no evidence to the contrary
surfaces, the recipient can then validate the sender as trustworthy
when it subsequently sees the same public key or certificate used to
sign messages from the same sender. In opposite, once the recipient
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. The This improves communication security of DHCPv6 messages. The
authentication options [RFC3315] may also be used for replay authentication options [RFC3315] may also be used for replay
protection. protection.
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
Authority that can be used to establish the trustworthiness of the Authority that can be used to establish the trustworthiness of the
node. A second option is defined to carry the certificate. node. Another option is defined to carry the certificate.
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
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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. If the
recipient does not support the algorithm used by the sender, it recipient does not support the algorithm used by the sender, it
cannot authenticate the message. In this case, the receiver SHOULD cannot authenticate the message. In this case, the receiver SHOULD
reply with a NotSupportAlgorithm status code (defined in reply with a NotSupportAlgorithm status code (defined in
Section 5.4). Upon receiving this status code, the sender MAY resend Section 5.4). Upon receiving this status code, the sender MAY resend
the message protected with the mandatory algorithms (defined in the message protected with the mandatory algorithms (defined in
Section 5.3). Therefore, the senders in a same administrative domain Section 5.3). Therefore, the senders in a same administrative domain
may be allowed to use various algorithms simultaneously. may be allowed to use various algorithms simultaneously.
4.3. Applicability
By default, a secure DHCPv6 enabled client SHOULD start with secure
model. It sends a DHCPv6 message with secure options. If the
recipient is secure DHCPv6 enabled server, their communication should
be in secure model. In the scenario where the secure DHCPv6 enabled
client and server fail to build up secure communication between them,
they may fall back the unsecure model, if both client and server
allow it.
In the scenario where the recipient is a legacy DHCPv6 server that
does not support secure mechanism, the DHCPv6 server (for most of
known DHCPv6 implemenations) would just omit or disregard unknown
options and still process 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 messages. If the client accept the unsecure
messages from the DHCPv6 server. The subsequent exchanges will be in
unsecure model.
In the scenario where a legacy client sends a unsecure message to a
secure DHCPv6 enabled server, there are two possibilities depending
on the server policy. If the server mandidates the authentication,
an UnspecFail (value 1, [RFC3315]) error status code, SHOULD be
returned. In such case, the client cannot build up the connection
with the server. If the server has been configured to support
unsecured request, the server would fall back the unsecure DHCPv6
model, and reply unsecure messages toward the client.
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
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_Public_Key | option-len | | OPTION_PK_PARAMETER | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. 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. The
key MUST be represented as a lower-case hexadecimal key MUST be represented as a lower-case hexadecimal
string with the most significant octet of the key string with the most significant octet of the key
first. first. Typically, the length of a 2048-bit RSA
public key is 256 bytes.
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_Certificate | 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, maximum 65535.
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 support of X.509 certificate is mandatory. The
length of a certificate is various. In this
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, except for the Authentication Option. The format
of the Signature option is described as follows: of the Signature option is described as follows:
0 1 2 3 0 1 2 3
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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 authentication option. It is
because both needs to apply hash algorithm to whole message, so there because both needs to apply hash algorithm to whole message, so there
must be a clear order and there could be only one last-created must be a clear order and there could be only one last-created
option. In order to avoid update RFC3315 because of changing auth option. In order to avoid update RFC3315 because of changing auth
option, the authors chose not include authentication option in the option, the authors chose not include authentication option in the
signature. signature.
5.4. Status Codes 5.4. Status Codes
o NotSupportAlgorithm (TBD4): Indicates the recipient does not o NotSupportAlgorithm (TBD4): indicates that the DHCPv6 server does
support algorthims that sender used. not support algorthims that sender used.
o NotSupportFaithModel (TBD5): Indicates the recipient does not o AuthFailNotSupportLoF (TBD5): indicates that the DHCPv6 client
support the leap of faith model. fails authentication check and the DHCPv6 server does not support
the leaf of faith model
o FaithListExceed (TBD6): Indicates the recipient's list that stores o AuthFailSupportLoF (TBD6): indicates that the DHCPv6 client fails
public keys or unverifiable certificates in the leap of faith authentication check. Although the DHCPv6 server does support the
model currently exceeds. leaf of faith, its list that stores public keys or unverifiable
certificates in the leap of faith model currently exceeds.
o SignitureFail (TBD7): indicates the message from DHCPv6 client
fails the signiture check.
6. Processing Rules and Behaviors 6. Processing Rules and Behaviors
This section only covers the scenario where both DHCPv6 client and
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 the Public Key or Certificate option,
which MUST contructed as explained in Section 5.1 or Section 5.2. which MUST contructed 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 the Signature option, which MUST be
constructed as explained in Section 5.3. It protects the message constructed as explained in Section 5.3. It protects the message
header and the message payload and all DHCPv6 options except for the header all DHCPv6 options except for the Authentication Option.
Signature option itself and the Authentication Option. Within the Within the Signature option the Timestamp field SHOULD be set to the
Signature option the Timestamp field SHOULD be set to the current current time, according to sender's real time clock.
time, according to sender's real time clock.
A Relay-forward and relay-reply message MUST NOT contain any Public A Relay-forward and relay-reply message MUST NOT contain any
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
the client or server.
Upon receiving a Reply message with a NotSupportAlgorithm status If the sender is a DHCPv6 client, in the failure cases, it receives a
code, the sender MAY resend the message protected with the mandatory Reply message with an error status code. The error status code
algorithms. indicates the failure reason on the server side. According to the
received status code, the client MAY take follow-up action:
Upon receiving a Reply message with a NotSupportFaithModel or o Upon receiving a NotSupportAlgorithm error status code, the client
FaithListExceed status code, the sender is not able to build up the MAY resend the message protected with the mandatory algorithms.
connection with the recipient. The sender MAY swith to a verifiable
certificate. In the latter case, the sender MAY retry later. o Upon receiving an AuthFailNotSupportLoF error status code, the
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.
o Upon receiving an AuthFailSupportLoF error status code, the 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. The client MAY retry with the same certificate/
public-key later.
o Upon receiving a SignitureFail error status code, the client MAY
resend the message.
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
a DHCPv6 client. In the failure cases, both DHCPv6 server and client
SHOULD NOT process received message, and the server SHOULD reply a
correspondent error status could, while the client does nothing.
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 both the Public
Key and Certificate option is absent, or both the Public Key and Key and Certificate option is absent, or both the Public Key and
Certificate option are presented. If all three options are absent, Certificate option are presented. In such failure, the DHCPv6 server
the recipient MAY fall back the unsecure DHCPv6 model. SHOULD reply an UnspecFail (value 1, [RFC3315]) error status code.
If all three options are absent, the sender MAY be legacy node or in
unsecure model, then, the recipient MAY fall back the unsecure DHCPv6
model if its local policy allows.
The recipient SHOULD first check the support of algorthims that The recipient SHOULD first check the support of algorthims that
sender used. If not, an error NotSupportAlgorithm status code should sender used. If all algorthims are supported, the recipient then
be sent back to the sender, while the message is dropped siliently. checks the authority of this sender. If not, the message is dropped.
If all algorthims are supported, the recipient then checks the
authority of this sender. In such failure, the DHCPv6 server SHOULD reply a NotSupportAlgorithm
error status code, defined in Section 5.4, back 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 verfication procedure
in the future. A sender certificate that finds a match in the local in the future. A sender certificate that finds a match in the local
trust certificate list are treated as verified. A fast search index trust certificate list are treated as verified. A fast search index
may be created for this list. 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 match 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 authorization 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 (LoF) that the sender is trustworthy. If no evidence to the
surfaces, the recipient can then validate the sender as trustworthy contrary surfaces, the recipient can then validate the sender as
when it subsequently sees the same public key or certificate used to trustworthy for subsequent message exchanges. In opposite, once the
sign messages from the same sender. If the recipient does not recipient has determined that it is being attacked, it can either
support the leap of faith model, it SHOULD reply a message with an forget that key, or remember that key in a blacklist and drop further
error NotSupportFaithModel status code, defined in Section 5.4, back packets associated with that key.
to the sender.
The number of cached public keys or unverifiable certificates MUST be If recipient does not support the leap of faith model, the message
limited in order to protect the DHCPv6 server against resource that fails authentication check MUST be dropped. In such failure,
exhaustion attacks. If the recipient's list that stores public keys the DHCPv6 server SHOULD reply an AuthFailNotSupportLoF error status
or unverifiable certificates in the leap of faith model exceeds, an code, defined in Section 5.4, back to the client.
error FaithListExceed status code SHOULD be returned to the sender.
The resource releasing policy against exceeding situations is out of
scope.
At this point, the recipient has either recognized the authorization On the recipient that supports the leap of faith model, the number of
cached public keys or unverifiable certificates MUST be limited in
order to protect against resource exhaustion attacks. If the
recipient's list that stores public keys or unverifiable certificates
in the leap of faith model exceeds, the message that fails
authentication check MUST be dropped. In such failure, the DHCPv6
server SHOULD reply an AuthFailNotSupportLoF error status code,
defined in Section 5.4, back to the client. The resource releasing
policy against exceeding situations is out of scope.
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. The order of two procedures is left as an
implementation decision. It is RECOMMENDED to check timestamp first, implementation decision. It is RECOMMENDED to check timestamp first,
because signature verification is much more computationally because signature verification is much more computationally
expensive. 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. unsecure messages. In the signature verification failure case, the
DHCPv6 server SHOULD reply a SignatureFail error status code, defined
The recipient MAY record the verified public key or certificate for in Section 5.4, back to the client.
future authentications.
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 SHOULD Certificate or the Signature option is invilad. The message MUST be
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, be 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 MUST 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.
skipping to change at page 12, line 27 skipping to change at page 14, line 16
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 time stamp 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) An 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,
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After the signature verification also successes, the RDnew and After the signature verification also successes, the RDnew and
TSnew values SHOULD be stored in the cache as RDlast and TSlast. TSnew values SHOULD be stored in the cache as RDlast and TSlast.
o When a message is received from a known peer (i.e., one that o When a message is received from a known peer (i.e., one that
already has an entry in the cache), the timestamp is checked already has an entry in the cache), the timestamp is checked
against the previously received Secure DHCPv6 message: against the previously received Secure DHCPv6 message:
TSnew + fuzz > TSlast + (RDnew - RDlast) x (1 - drift) - fuzz TSnew + fuzz > TSlast + (RDnew - RDlast) x (1 - drift) - fuzz
If this inequality does not hold, the recipient SHOULD silently If this inequality does not hold or RDnew < RDlast, the recipient
discard the message. If, on the other hand, the inequality holds, SHOULD silently discard the message. If, on the other hand, the
the recipient SHOULD process the message. inequality holds, the recipient SHOULD process the message.
Moreover, if the above inequality holds and TSnew > TSlast, the Moreover, if the above inequality holds and TSnew > TSlast, the
recipient SHOULD update RDlast and TSlast after the signature recipient SHOULD update RDlast and TSlast after the signature
verification also successes. Otherwise, the recipient MUST NOT verification also successes. Otherwise, the recipient MUST NOT
update RDlast or TSlast. update RDlast or TSlast.
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
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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, the two communciating nodes can be synchronized is out of However, how the two communcating nodes can be synchronized is out of
scope of this work. 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.
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Name | Value | RFCs Name | Value | RFCs
-------------------+---------+-------------- -------------------+---------+--------------
Reserved | 0x0000 | this document Reserved | 0x0000 | this document
RSASSA-PKCS1-v1_5 | 0x0001 | 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 | NotSupportAlgorithm | this document
TBD5 | NotSupportFaithModel | this document TBD5 | AuthFailNotSupportLoF | this document
TBD6 | FaithListExceed | this document TBD6 | AuthFailSupportLoF | this document
TBD7 | SignitureFail | this document
9. Acknowledgements 9. Acknowledgements
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 and other members of the Francis Dupont, Tomek Mrugalski, Gang Chen, Qi Sun, Suresh Krishnan
IETF DHC working groups for their valuable comments. and other members of the IETF DHC working groups for 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] 10. Change log [RFC Editor: Please remove]
draft-ietf-dhc-sedhcpv6-02: addressed comments (applicability
statement, redesign the error codes and their logic) from IETF89 DHC
WG meeting and volunteer reviewers . 2014-04-14.
draft-ietf-dhc-sedhcpv6-01: addressed comments from IETF88 DHC WG
meeting. Moved Dacheng Zhang from acknowledgement to be co-author.
2014-02-14
draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19. draft-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.
 End of changes. 47 change blocks. 
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