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Versions: (draft-jiang-dhc-sedhcpv6) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21

DHC Working Group                                               S. Jiang
Internet-Draft                              Huawei Technologies Co., Ltd
Intended status: Standards Track                                   L. Li
Expires: July 20, 2017                                            Y. Cui
                                                     Tsinghua University
                                                               T. Jinmei
                                                           Infoblox Inc.
                                                                T. Lemon
                                                           Nominum, Inc.
                                                                D. Zhang
                                                        January 16, 2017


                             Secure DHCPv6
                       draft-ietf-dhc-sedhcpv6-20

Abstract

   DHCPv6 includes no deployable security mechanism that can protect
   end-to-end communication between DHCP clients and servers.  This
   document describes a mechanism for using public key cryptography to
   provide such security.  The mechanism provides encryption in all
   cases, and can be used for authentication based on pre-sharing of
   authorized certificates.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 20, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Issues of DHCPv6 . . . . . . . . . . . . . . . . . .   4
   5.  Secure DHCPv6 Overview  . . . . . . . . . . . . . . . . . . .   5
     5.1.  Solution Overview . . . . . . . . . . . . . . . . . . . .   5
     5.2.  New Components  . . . . . . . . . . . . . . . . . . . . .   6
     5.3.  Support for Algorithm Agility . . . . . . . . . . . . . .   7
     5.4.  Impact on RFC3315 . . . . . . . . . . . . . . . . . . . .   7
     5.5.  Applicability . . . . . . . . . . . . . . . . . . . . . .   8
   6.  DHCPv6 Client Behavior  . . . . . . . . . . . . . . . . . . .   8
   7.  DHCPv6 Server Behavior  . . . . . . . . . . . . . . . . . . .  11
   8.  Relay Agent Behavior  . . . . . . . . . . . . . . . . . . . .  13
   9.  Processing Rules  . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Increasing Number Check . . . . . . . . . . . . . . . . .  13
   10. Extensions for Secure DHCPv6  . . . . . . . . . . . . . . . .  14
     10.1.  New DHCPv6 Options . . . . . . . . . . . . . . . . . . .  14
       10.1.1.  Algorithm Option . . . . . . . . . . . . . . . . . .  14
       10.1.2.  Certificate Option . . . . . . . . . . . . . . . . .  17
       10.1.3.  Signature option . . . . . . . . . . . . . . . . . .  18
       10.1.4.  Increasing-number Option . . . . . . . . . . . . . .  19
       10.1.5.  Encryption-Key-Tag Option  . . . . . . . . . . . . .  20
       10.1.6.  Encrypted-message Option . . . . . . . . . . . . . .  20
     10.2.  New DHCPv6 Messages  . . . . . . . . . . . . . . . . . .  21
     10.3.  Status Codes . . . . . . . . . . . . . . . . . . . . . .  22
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  22
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  24
   14. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  25
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  28
     15.2.  Informative References . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30






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1.  Introduction

   The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315])
   allows DHCPv6 servers to flexibly provide addressing and other
   configuration information relating to local network infrastructure to
   DHCP clients.  The protocol provides no deployable security
   mechanism, and consequently is vulnerable to various attacks.

   This document provides a brief summary of the security
   vulnerabilities of the DHCPv6 protocol and then describes a new
   extension to the protocol that provides two additional types of
   security:

   o  authentication of the DHCPv6 client and the DHCPv6 server to
      defend against active attacks, such as spoofing.

   o  encryption between the DHCPv6 client and the DHCPv6 server in
      order to protect the DHCPv6 communication from pervasive
      monitoring.

   The extension specified in this document applies only to end-to-end
   communication between DHCP servers and clients.  Options added by
   relay agents in Relay-Forward messages, and options other than the
   client message in Relay-Reply messages sent by DHCP servers, are not
   protected.  Such communications are already protected using the
   mechanism described in section 21.1 in [RFC3315].

   This extension introduces two new DHCPv6 messages: the Encrypted-
   Query and the Encrypted-Response messages.  It defines six new DHCPv6
   options: the Algorithm, Certificate, Signature, Increasing-number,
   Encryption-Key-Tag option and Encrypted-message options.  The
   Algorithm, Certificate, Signature, and Increasing-number options are
   used for authentication.  The Encryption-Query message, Encryption-
   Response message, Encrypted-message option and Encryption-Key-Tag
   option are used for encryption.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119] when they
   appear in ALL CAPS.  When these words are not in ALL CAPS (such as
   "should" or "Should"), they have their usual English meanings, and
   are not to be interpreted as [RFC2119] key words.







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3.  Terminology

   This section defines terminology specific to secure DHCPv6 used in
   this document.

   secure DHCPv6 client:  A node that initiates a DHCPv6 request on a
                   link to obtain DHCPv6 configuration parameters from
                   one or more DHCPv6 servers using the encryption and
                   optional authentication mechanisms defined in this
                   document.

   secure DHCPv6 server:  A DHCPv6 server that implements the
                   authentication and encryption mechanisms defined in
                   this document, and is configured to use them.

4.  Security Issues of DHCPv6

   [RFC3315] defines an authentication mechanism with integrity
   protection.  This mechanism uses a symmetric key that is shared by
   the client and server for authentication.  It does not provide any
   key distribution mechanism.

   For this approach, operators can set up a key database for both
   servers and clients from which the client obtains a key before
   running DHCPv6.  However, manual key distribution runs counter to the
   goal of minimizing the configuration data needed at each host.
   Consequently, there are no known deployments of this security
   mechanism.

   [RFC3315] provides an additional mechanism for preventing off-network
   timing attacks using the Reconfigure message: the Reconfigure Key
   authentication method.  However, this method protects only the
   Reconfigure message.  The key is transmitted in plaintext to the
   client in earlier exchanges and so this method is vulnerable to on-
   path active attacks.

   Anonymity Profile for DHCP Clients [RFC7844] explains how to generate
   DHCPv4 or DHCPv6 requests that minimize the disclosure of identifying
   information.  However, the anonymity profile limits the use of the
   certain options.  It also cannot anticipate new options that may
   contain private information.  In addition, the anonymity profile does
   not work in cases where the client wants to maintain anonymity from
   eavesdroppers but must identify itself to the DHCP server with which
   it intends to communicate.

   Privacy consideration for DHCPv6 [RFC7824] presents an analysis of
   the privacy issues associated with the use of DHCPv6 by Internet
   users.  No solutions are presented.



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   Current DHCPv6 messages are still transmitted in cleartext and the
   privacy information within the DHCPv6 message is not protected from
   passive attack, such as pervasive monitoring [RFC7258].  The privacy
   information of the IPv6 host, such as DUID, may be gleaned to find
   location information, previous visited networks and so on.  [RFC7258]
   claims that pervasive monitoring should be mitigated in the design of
   IETF protocol, where possible.

   To better address the problem of passive monitoring and to achieve
   authentication without requiring a symmetric key distribution
   solution for DHCP, this document defines an asymmetric key
   authentication and encryption mechanism.  This protects against both
   active attacks, such as spoofing, and passive attacks, such as
   pervasive monitoring.

5.  Secure DHCPv6 Overview

5.1.  Solution Overview

   The following figure illustrates the secure DHCPv6 procedure.
   Briefly, this extension establishes the server's identity with an
   anonymous Information-Request exchange.  Once the server's identity
   has been established, the client may either choose to communicate
   with the server or not.  Not communicating with an unknown server
   avoids revealing private information, but if there is no known server
   on a particular link, the client will be unable to communicate with a
   DHCP server.

   If the client chooses to communicate with the selected server(s), it
   uses the Encrypted-Query message to encapsulate its communications to
   the DHCP server.  The server responds with Encrypted-Response
   messages.  Normal DHCP messages are encapsulated in these two new
   messages using the new defined Encrypted-message option.  Besides the
   Encrypted-message option, the Signature option is defined to verify
   the integrity of the DHCPv6 messages and then authentication of the
   client and the server.  The Increasing number option is defined to
   detect a replay attack.














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           +-------------+                           +-------------+
           |DHCPv6 Client|                           |DHCPv6 Server|
           +-------------+                           +-------------+
                  |            Information-request           |
                  |----------------------------------------->|
                  |             Algorithm option             |
                  |           Option Request option          |
                  |                                          |
                  |                    Reply                 |
                  |<-----------------------------------------|
                  |             Certificate option           |
                  |             Signature option             |
                  |          Increasing-number option        |
                  |         Server Identifier option         |
                  |                                          |
                  |            Encryption-Query              |
                  |----------------------------------------->|
                  |          Encrypted-message option        |
                  |          Server Identifier option        |
                  |         Encryption-Key-Tag option        |
                  |                                          |
                  |            Encryption-Response           |
                  |<-----------------------------------------|
                  |          Encrypted-message option        |
                  |                                          |

                     Figure 1: Secure DHCPv6 Procedure

5.2.  New Components

   The new components of the mechanism specified in this document are as
   follows:

   o  Servers and clients that use certificates first generate a public/
      private key pair and then obtain a certificate that signs the
      public key.  The Certificate option is defined to carry the
      certificate of the sender.

   o  The algorithm option is defined to carry the algorithms lists for
      algorithm agility.

   o  The signature is generated using the private key to verify the
      integrity of the DHCPv6 messages.  The Signature option is defined
      to carry the signature.

   o  The increasing number is used to detect replayed packet.  The
      Increasing-number option is defined to carry a strictly-increasing
      serial number.



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   o  The encryption key Tag is calculated from the public key data.
      The Encryption-Key-Tag option is defined to identify the used
      public/private key pair.

   o  The Encrypted-message option is defined to contain the encrypted
      DHCPv6 message.

   o  The Encrypted-Query message is sent from the secure DHCPv6 client
      to the secure DHCPv6 server.  The Encrypted-Query message MUST
      contain the Encrypted-message option and Encryption-Key-Tag
      option.  In addition, the Server Identifier option MUST be
      included if it is contained in the original DHCPv6 message.  The
      Encrypted-Query message MUST NOT contain any other options.

   o  The Encrypted-Response message is sent from the secure DHCPv6
      server to the secure DHCPv6 client.  The Encrypted-Response
      message MUST contain the Encrypted-message option.  The Encrypted-
      Response message MUST NOT contain any other options.

5.3.  Support for Algorithm Agility

   In order to provide a means of addressing problems that may emerge
   with existing hash algorithms, signature algorithm and encryption
   algorithms in the future, this document provides a mechanism to
   support algorithm agility.  The support for algorithm agility in this
   document is mainly a algorithm notification mechanism between the
   client and the server.  The same client and server SHOULD use the
   same algorithm in a single communication session.  The sender can
   offer a set of algorithms, and then the receiver selects one
   algorithm for the future communication.

5.4.  Impact on RFC3315

   For secure DHCPv6, the Solicit and Rebind messages can be sent only
   to the selected server(s) which share one common certificate.  If the
   client doesn't like the received Advertise(s) it could restart the
   whole process and selects another certificate, but it will be more
   expensive, and there's no guarantee that other servers can provide
   better Advertise(s).

   [RFC3315] provides an additional mechanism for preventing off-network
   timing attacks using the Reconfigure message: the Reconfigure Key
   authentication method.  Secure DHCPv6 can protect the Reconfigure
   message using the encryption method.  So the Reconfigure Key
   authentication method SHOULD NOT be used if Secure DHCPv6 is applied.






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5.5.  Applicability

   In principle, secure DHCPv6 is applicable in any environment where
   physical security on the link is not assured and attacks on DHCPv6
   are a concern.  In practice, however, authenticated and encrypted
   DHCPv6 configuration will rely on some operational assumptions mainly
   regarding public key distribution and management.  In order to
   achieve the wider use of secure DHCPv6, opportunistic security
   [RFC7435] can be applied to secure DHCPv6 deployment, which allows
   DHCPv6 encryption in environments where support for authentication or
   a key distribution mechanism is not available.

   Secure DHCPv6 can achieve authentication and encryption based on pre-
   sharing of authorized certificates.  The One feasible environment in
   an early deployment stage would be enterprise networks.  In
   enterprise networks, the client is manually pre-configured with the
   trusted servers' public key and the server is also manually pre-
   configured with the trusted clients' public keys.  In some scenario,
   such as coffee shop where the certificate cannot be validated and one
   wants access to the Internet, then the DHCPv6 configuration process
   can be encrypted without authentication.

   Note that this deployment scenario based on manual operation is not
   much different from the existing, shared-secret based authentication
   mechanisms defined in [RFC3315] in terms of operational costs.
   However, Secure DHCPv6 is still securer than the shared-secret
   mechanism in that even if clients' keys stored for the server are
   stolen that does not mean an immediate threat as these are public
   keys.  In addition, if some kind of Public Key Infrastructure (PKI)
   is used with Secure DHCPv6, even if the initial installation of the
   certificates is done manually, it will help reduce operational costs
   of revocation in case a private key (especially that of the server)
   is compromised.

6.  DHCPv6 Client Behavior

   The secure DHCPv6 client is pre-configured with a certificate and its
   corresponding private key for client authentication.  If the client
   does not obtain a certificate from Certificate Authority (CA), it can
   generate the self-signed certificate.

   The secure DHCPv6 client sends an Information-request message as per
   [RFC3315].  The Information-request message is used by the DHCPv6
   client to request the server's certificate information without having
   addresses, prefixes or any non-security options assigned to it.  The
   contained Option Request option MUST carry the option code of the
   Certificate option.  In addition, the contained Algorithm option MUST
   be constructed as explained in Section 10.1.1.  The Information-



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   request message MUST NOT include any other DHCPv6 options except the
   above options to minimize the client's privacy information leakage.

   When receiving the Reply messages from the DHCPv6 servers, a secure
   DHCPv6 client discards any DHCPv6 message that meets any of the
   following conditions:

   o  the Signature option is missing,

   o  multiple Signature options are present,

   o  the Certificate option is missing.

   And then the client first checks acknowledged hash, signature and
   encryption algorithms that the server supports.  If the hash
   algorithm field is zero, then it indicates that the hash algorithm is
   fixed according to the corresponding signature algorithm.  The client
   also uses the acknowledged algorithms in the return messages.

   Then the client checks the authority of the server.  In some scenario
   where non-authenticated encryption can be accepted, such as coffee
   shop, then authentication is optional and can be skipped.  For the
   certificate check method, the client validates the certificates
   through the pre-configured local trusted certificates list or other
   methods.  A certificate that finds a match in the local trust
   certificates list is treated as verified.  If the certificate check
   fails, the Reply message is dropped.

   The client MUST now authenticate the server by verifying the
   signature and checking increasing number, if there is a Increasing-
   number option.  The order of two procedures is left as an
   implementation decision.  It is RECOMMENDED to check increasing
   number first, because signature verification is much more
   computationally expensive.  The client checks the Increasing-number
   option according to the rule defined in Section 9.1.  For the message
   without an Increasing-number option, according to the client's local
   policy, it MAY be acceptable or rejected.  The Signature field
   verification MUST show that the signature has been calculated as
   specified in Section 10.1.3.  Only the messages that get through both
   the signature verification and increasing number check (if there is a
   Increasing-number option) are accepted.  Reply message that does not
   pass the above tests MUST be discarded.

   If there are multiple authenticated DHCPv6 certs, the client selects
   one DHCPv6 cert for the following communication.  The selected
   certificate may correspond to multiple DHCPv6 servers.  If there are
   no authenticated DHCPv6 certs or existing servers fail
   authentication, the client should retry a number of times.  The



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   client conducts the server discovery process as per section 18.1.5 of
   [RFC3315] to avoid a packet storm.  In this way, it is difficult for
   a rogue server to beat out a busy "real" server.  And then the client
   takes some alternative action depending on its local policy, such as
   attempting to use an unsecured DHCPv6 server.

   Once the server has been authenticated, the DHCPv6 client sends the
   Encrypted-Query message to the DHCPv6 server.  The Encrypted-Query
   message contains the Encrypted-message option, which MUST be
   constructed as explained in Section 10.1.6.  The Encrypted-message
   option contains the encrypted DHCPv6 message using the public key
   contained in the selected cert.  In addition, the Server Identifier
   option MUST be included if it is in the original message (i.e.
   Request, Renew, Decline, Release) to avoid the need for other servers
   receiving the message to attempt to decrypt it.  The Encrypted-Query
   message MUST include the Encryption-Key-Tag option to identify the
   used public/private key pair, which is constructed as explained in
   Section 10.1.5.  The Encrypted-Query message MUST NOT contain any
   other DHCPv6 option except the Server Identifier option, Encryption-
   Key-Tag option, Encrypted-Message option.

   The first DHCPv6 message sent from the client to the server, such as
   Solicit message, MUST contain the Certificate option, Signature
   option and Increasing-number option for client authentication.  The
   encryption text SHOULD be formatted as explain in [RFC5652].  The
   Certificate option MUST be constructed as explained in
   Section 10.1.2.  In addition, one and only one Signature option MUST
   be contained, which MUST be constructed as explained in
   Section 10.1.3.  One and only one Increasing-number option SHOULD be
   contained, which MUST be constructed as explained in Section 10.1.4.
   In addition, the subsequent encrypted DHCPv6 message sent from the
   client can also contain the Increasing-number option to defend
   against replay attack.

   For the received Encrypted-Response message, the client MUST drop the
   Encrypted-Response message if other DHCPv6 option except Encrypted-
   message option is contained.  Then, the client extracts the
   Encrypted-message option and decrypts it using its private key to
   obtain the original DHCPv6 message.  In this document, it is assumed
   that the client uses only one certificate for the encrypted DHCPv6
   configuration.  So, the corresponding private key is used for
   decryption.  After the decryption, it handles the message as per
   [RFC3315].  If the decrypted DHCPv6 message contains the Increasing-
   number option, the DHCPv6 client checks it according to the rule
   defined in Section 9.1.

   If the client fails to get the proper parameters from the chosen
   server(s), it can select another authenticated certificate and send



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   the Encrypted-Query message to another authenticated server(s) for
   parameters configuration until the client obtains the proper
   parameters.

   When the decrypted message is Reply message with an error status
   code, the error status code indicates the failure reason on the
   server side.  According to the received status code, the client MAY
   take follow-up action:

   o  Upon receiving an AuthenticationFail error status code, the client
      is not able to build up the secure communication with the server.
      However, there may be other DHCPv6 servers available that
      successfully complete authentication.  The client MAY use the
      AuthenticationFail as a hint and switch to other DHCPv6 server if
      it has another one.  The client SHOULD retry with another
      authenticated certificate.  However, if the client decides to
      retransmit using the same certificate after receiving
      AuthenticationFail, it MUST NOT retransmit immediately and MUST
      follow normal retransmission routines defined in [RFC3315].

   o  Upon receiving a ReplayDetected error status code, the client MAY
      resend the message with an adjusted Increasing-number option
      according to the returned number from the DHCPv6 server.

   o  Upon receiving a SignatureFail error status code, the client MAY
      resend the message following normal retransmission routines
      defined in [RFC3315].

7.  DHCPv6 Server Behavior

   The secure DHCPv6 server is pre-configured with a certificate and its
   corresponding private key for server authentication.  If the server
   does not obtain the certificate from Certificate Authority (CA), it
   can generate the self-signed certificate.

   When the DHCPv6 server receives the Information-request message and
   the contained Option Request option identifies the request is for the
   server's certificate information, it SHOULD first check the hash,
   signature, encryption algorithms sets that the client supports.  The
   server selects one hash, signature, encryption algorithm from the
   acknowledged algorithms sets for the future communication.  And then,
   the server replies with a Reply message to the client.  The Reply
   message MUST contain the requested Certificate option, which MUST be
   constructed as explained in Section 10.1.2, and Server Identifier
   option.  In addition, the Reply message MUST contain one and only one
   Signature option, which MUST be constructed as explained in
   Section 10.1.3.  Besides, the Reply message SHOULD contain one and




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   only one Increasing-number option, which MUST be constructed as
   explained in Section 10.1.4.

   Upon the receipt of Encrypted-Query message, the server MUST drop the
   message if the other DHCPv6 option is contained except Server
   Identifier option, Encryption-Key-Tag option, Encrypted-message
   option.  Then, the server checks the Server Identifier option.  The
   DHCPv6 server drops the message that is not for it, thus not paying
   cost to decrypt messages.  If it is the target server, according to
   the Encryption-Key-Tag option, the server identifies the used public/
   private key pair and decrypts the Encrypted-message option using the
   corresponding private key.  If the decryption fails, the server
   discards the received message.

   If secure DHCPv6 server needs client authentication and decrypted
   message is a Solicit/Information-request message which contains the
   information for client authentication, the secure DHCPv6 server
   discards the received message that meets any of the following
   conditions:

   o  the Signature option is missing,

   o  multiple Signature options are present,

   o  the Certificate option is missing.

   For the signature failure, the server SHOULD send an encrypted Reply
   message with an UnspecFail (value 1, [RFC3315]) error status code to
   the client.

   The server validates the client's certificate through the local pre-
   configured trusted certificates list.  A certificate that finds a
   match in the local trust certificates list is treated as verified.
   The message that fails authentication validation MUST be dropped.  In
   such failure, the DHCPv6 server replies with an encrypted Reply
   message with an AuthenticationFail error status code, defined in
   Section 10.3, back to the client.  At this point, the server has
   either recognized the authentication of the client, or decided to
   drop the message.

   If the decrypted message contains the Increasing-number option, the
   server checks it according to the rule defined in Section 9.1.  If
   the check fails, an encrypted Reply message with a ReplayDetected
   error status code, defined in Section 10.3, should be sent back to
   the client.  In the Reply message, a Increasing-number option is
   carried to indicate the server's stored number for the client to use.
   According to the server's local policy, the message without an
   Increasing-number option MAY be acceptable or rejected.



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   The Signature field verification MUST show that the signature has
   been calculated as specified in Section 10.1.3.  If the signature
   check fails, the DHCPv6 server SHOULD send an encrypted Reply message
   with a SignatureFail error status code.  Only the clients that get
   through both the signature verification and increasing number check
   (if there is a Increasing-number option) are accepted as
   authenticated clients and continue to be handled their message as
   defined in [RFC3315].

   Once the client has been authenticated, the DHCPv6 server sends the
   Encrypted-response message to the DHCPv6 client.  The Encrypted-
   response message MUST only contain the Encrypted-message option,
   which MUST be constructed as explained in Section 10.1.6.  The
   encryption text SHOULD be formatted as explain in [RFC5652].  The
   Encrypted-message option contains the encrypted DHCPv6 message that
   is encrypted using the authenticated client's public key.  To provide
   the replay protection, the Increasing-number option can be contained
   in the encrypted DHCPv6 message.

8.  Relay Agent Behavior

   When a DHCPv6 relay agent receives an Encrypted-query or Encrypted-
   response message, it may not recognize this message.  The unknown
   messages MUST be forwarded as described in [RFC7283].

   When a DHCPv6 relay agent recognizes the Encrypted-query and
   Encrypted-response messages, it forwards the message according to
   section 20 of [RFC3315].  There is nothing more the relay agents have
   to do, it neither needs to verify the messages from client or server,
   nor add any secure DHCPv6 options.  Actually, by definition in this
   document, relay agents MUST NOT add any secure DHCPv6 options.

   Relay-forward and Relay-reply messages MUST NOT contain any
   additional Certificate option or Increasing-number option, aside from
   those present in the innermost encapsulated messages from the client
   or server.

9.  Processing Rules

9.1.  Increasing Number Check

   In order to check the Increasing-number option, defined in
   Section 10.1.4, the client/server has one stable stored number for
   replay attack detection.  The server should keep a record of the
   increasing number forever.  And the client keeps a record of the
   increasing number during the DHCPv6 configuration process with the
   DHCPv6 server.  And the client can forget the increasing number




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   information after the transaction is finished.  The client's initial
   locally stored increasing number is set to zero.

   It is essential to remember that the increasing number is finite.
   All arithmetic dealing with sequence numbers must be performed modulo
   2^64.  This unsigned arithmetic preserves the relationship of
   sequence numbers as they cycle from 2^64 - 1 to 0 again.

   In order to check the Increasing-number option, the following
   comparison is needed.

   NUM.STO = the stored number in the client/server

   NUM.REC = the acknowledged number from the received message

   The Increasing-number option in the received message passes the
   increasing number check if NUM.REC is more than NUM.STO.  And then,
   the value of NUM.STO is changed into the value of NUM.REC.

   The increasing number check fails if NUM.REC is equal with or less
   than NUM.STO.

10.  Extensions for Secure DHCPv6

   This section describes the extensions to DHCPv6.  Six new DHCPv6
   options, two new DHCPv6 messages and six new status codes are
   defined.

10.1.  New DHCPv6 Options

10.1.1.  Algorithm Option

   The Algorithm option carries the algorithms sets for algorithm
   agility, which is contained in the Information-request message.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_ALGORITHM         |         option-len            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                          EA-id List                           .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                          SA-id List                           .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                          HA-id List                           .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 2: Algorithm Option



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   o  option-code: OPTION_ALGORITHM (TBA1).

   o  option-len: length of EA-id List + length of SA-id List + length
      of HA-id List in octets.

   o  EA-id: The format of the EA-id List field is shown in Figure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           EA-len              |               EA-id           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.                              ...                              .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               EA-id           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

EA-len         The length of the following EA-ids.

EA-id          2-octets value to indicate the Encryption Algorithm id.
               The client enumerates the list of encryption algorithms it
               supports to the server. The encryption algorithm is used
               for the encrypted DHCPv6 configuration process. This design
               is adopted in order to provide encryption algorithm agility.
               The value is from the Encryption Algorithm for Secure DHCPv6
               registry in IANA. A registry of the initial assigned values
               is defined in Section 12. The mandatory encryption
               algorithms MUST be included.

                        Figure 3: EA-id List Field

   o  SA-id List: The format of the SA-id List field is shown in
      Figure 4.


















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 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           SA-len              |               SA-id           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.                              ...                              .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               SA-id           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

SA-len         The length of the following SA-ids.

SA-id          2-octets value to indicate the Signature Algorithm id.
               The client enumerates the list of signature algorithms it
               supports to the server. This design is adopted in
               order to provide signature algorithm agility. The
               value is from the Signature Algorithm for Secure
               DHCPv6 registry in IANA. The support of RSASSA-PKCS1-v1_5
               is mandatory. A registry of the initial assigned
               values is defined in Section 12. The mandatory
               signature algorithms MUST be included.

                        Figure 4: SA-id List Field

   o  HA-id List: The format of the HA-id List field is shown in
      Figure 5.

























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 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           HA-len              |               HA-id           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
.                              ...                              .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               HA-id           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

HA-len         The length of the following HA-ids.

HA-id          2-octets value to indicate the Hash Algorithm id.
               The client enumerates the list of hash algorithms it
               supports to the server. This design is adopted in order to
               provide hash algorithm agility. The value is from the
               Hash Algorithm for Secure DHCPv6 registry in IANA. The
               support of SHA-256 is mandatory. A registry of the
               initial assigned values is defined in Section 12.
               The mandatory hash algorithms MUST be included.

                        Figure 5: HA-id List Field

10.1.2.  Certificate Option

   The Certificate option carries the certificate of the client/server,
   which is contained in the Reply message.  The format of the
   Certificate option is described as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_CERTIFICATE       |         option-len            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              EA-id            |            SA-id              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .                           Certificate                         .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 6: Certificate Option

   o  option-code: OPTION_CERTIFICATE (TBA2).

   o  option-len: 4 + length of Certificate in octets.

   o  EA-id: Encryption Algorithm id which is used for the certificate.



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   o  SA-id: Signature Algorithm id which is used for the certificate.

   o  Certificate: A variable-length field containing certificates.  The
      encoding of certificate and certificate data MUST be in format as
      defined in Section 3.6, [RFC7296].  The support of X.509
      certificate is mandatory.

   It should be noticed that the scenario where the values of EA-id and
   SA-id are both 0 makes no sense and the client MUST discard a message
   with such values.

10.1.3.  Signature option

   The Signature option contains a signature that is signed by the
   private key to be attached to the Reply message.  The Signature
   option could be in any place within the DHCPv6 message while it is
   logically created after the entire DHCPv6 header and options.  It
   protects the entire DHCPv6 header and options, including itself.  The
   format of the Signature option is described as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     OPTION_SIGNATURE          |        option-len             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         SA-id                 |            HA-id              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .                    Signature (variable length)                .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 7: Signature Option

   o  option-code: OPTION_SIGNATURE (TBA3).

   o  option-len: 4 + length of Signature field in octets.

   o  SA-id: Signature Algorithm id.  The signature algorithm is used
      for computing the signature result.  This design is adopted in
      order to provide signature algorithm agility.  The value is from
      the Signature Algorithm for Secure DHCPv6 registry in IANA.  The
      support of RSASSA-PKCS1-v1_5 is mandatory.  A registry of the
      initial assigned values is defined in Section 12.

   o  HA-id: Hash Algorithm id.  The hash algorithm is used for
      computing the signature result.  This design is adopted in order
      to provide hash algorithm agility.  The value is from the Hash



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      Algorithm for Secure DHCPv6 registry in IANA.  The support of
      SHA-256 is mandatory.  A registry of the initial assigned values
      is defined in Section 12.  If the hash algorithm is fixed
      according to the corresponding signature algorithm, the HA-id
      field is set to zero.

   o  Signature: A variable-length field containing a digital signature.
      The signature value is computed with the hash algorithm and the
      signature algorithm, as described in HA-id and SA-id.  The
      Signature field MUST be padded, with all 0, to the next octet
      boundary if its size is not a multiple of 8 bits.  The padding
      length depends on the signature algorithm, which is indicated in
      the SA-id field.

   Note: If Secure DHCPv6 is used, the DHCPv6 message is encrypted in a
   way that the authentication mechanism defined in RFC3315 does not
   understand.  So the Authentication option SHOULD NOT be used if
   Secure DHCPv6 is applied.

10.1.4.  Increasing-number Option

   The Increasing-number option carries the strictly increasing number
   for anti-replay protection, which is contained in the Reply message
   and the encrypted DHCPv6 message.  It is optional.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   OPTION_INCREASING_NUM       |        option-len             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                  Increasing-Num (64-bit)                      |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code    OPTION_INCREASING_NUM (TBA4).

option-len     8, in octets.

Increasing-Num A strictly increasing number for the replay attack detection
               which is more than the local stored number.

                    Figure 8: Increasing-number Option







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10.1.5.  Encryption-Key-Tag Option

   The Encryption-Key-Tag option carries the key identifier which is
   calculated from the public key data.  The Encrypted-Query message
   MUST contain the Encryption-Key-Tag option to identify the used
   public/private key pair.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    OPTION_ENCRYPTION_KEY_TAG  |           option-len          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                    encryption key tag                         .
     .                       (variable)                              .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 9: Encryption-Key-Tag Option

   option-code  OPTION_ENCRYPTION_KEY_TAG (TBA5).

   option-len  Length of the encryption key tag.

   encryption key tag  A variable length field containing the encryption
      key tag sent from the client to server to identify the used
      public/private key pair.  The encryption key tag is calculated
      from the public key data, like fingerprint of a specific public
      key.  How to generate the encryption key tag adopts the method
      define in Appendix B in [RFC4034] and section 5.5 in [RFC6840].
      The data of the public key is used as input of the generation
      function.

10.1.6.  Encrypted-message Option

   The Encrypted-message option carries the encrypted DHCPv6 message,
   which is calculated with the recipient's public key.  The Encrypted-
   message option is contained in the Encrypted-Query message or the
   Encrypted-Response message.

   The format of the Encrypted-message option is:










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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          option-code          |           option-len          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                  encrypted DHCPv6 message                     .
     .                       (variable)                              .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 10: Encrypted-message Option

   option-code  OPTION_ENCRYPTED_MSG (TBA6).

   option-len  Length of the encrypted DHCPv6 message.

   encrypted DHCPv6 message  A variable length field containing the
      encrypted DHCPv6 message.  In Encrypted-Query message, it contains
      encrypted DHCPv6 message sent from a client to server.  In
      Encrypted-response message, it contains encrypted DHCPv6 message
      sent from a server to client.

10.2.  New DHCPv6 Messages

   Two new DHCPv6 messages are defined to achieve the DHCPv6 encryption:
   Encrypted-Query and Encrypted-Response.  Both the DHCPv6 messages
   defined in this document share the following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    msg-type   |               transaction-id                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                             options                           .
     .                           (variable)                          .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 11: The format of Encrypted-Query and Encrypted-Response
                                 Messages

   msg-type        Identifier of the message type.  It can be either
                   Encrypted-Query (TBA7) or DHCPv6-Response (TBA8).

   transaction-id  The transaction ID for this message exchange.




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   options         The Encrypted-Query message MUST contain the
                   Encrypted-message option, Encryption-Key-Tag option
                   and Server Identifier option if the message in the
                   Encrypted-message option has a Server Identifier
                   option.  The Encrypted-Response message MUST only
                   contain the Encrypted-message option.

10.3.  Status Codes

   The following new status codes, see Section 5.4 of [RFC3315] are
   defined.

   o  AuthenticationFail (TBD9): indicates that the message from the
      DHCPv6 client fails authentication check.

   o  ReplayDetected (TBD10): indicates the message from DHCPv6 client
      fails the increasing number check.

   o  SignatureFail (TBD11): indicates the message from DHCPv6 client
      fails the signature check.

11.  Security Considerations

   This document provides the authentication and encryption mechanisms
   for DHCPv6.

   [RFC6273] has analyzed possible threats to the hash algorithms used
   in SEND.  Since Secure DHCPv6 defined in this document uses the same
   hash algorithms in similar way to SEND, analysis results could be
   applied as well: current attacks on hash functions do not constitute
   any practical threat to the digital signatures used in the signature
   algorithm in Secure DHCPv6.

   There are some mandatory algorithm for encryption algorithm in this
   document.  It may be at some point that the mandatory algorithm is no
   longer safe to use.

   A server or a client, whose local policy accepts messages without a
   Increasing-number option, may have to face the risk of replay
   attacks.

   If the client tries more than one cert for client authentication, the
   server can easily get a client that implements this to enumerate its
   entire cert list and probably learn a lot about a client that way.
   For this security item, It is RECOMMENDED that client certificates
   could be tied to specific server certificates by configuration.





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12.  IANA Considerations

   This document defines six new DHCPv6 [RFC3315] options.  The IANA is
   requested to assign values for these six options from the DHCPv6
   Option Codes table of the DHCPv6 Parameters registry maintained in
   http://www.iana.org/assignments/dhcpv6-parameters.  The six options
   are:

      The Algorithm Option (TBA1), described in Section 10.1.2.

      The Certificate Option (TBA2), described in Section 10.1.2.

      The Signature Option (TBA3), described in Section 10.1.3.

      The Increasing-number Option (TBA4),described in Section 10.1.4.

      The Encryption-Key-Tag Option (TBA5),described in Section 10.1.5.

      The Encrypted-message Option (TBA6), described in Section 10.1.6.

   The IANA is also requested to assign value for these two messages
   from the DHCPv6 Message Types table of the DHCPv6 Parameters registry
   maintained in http://www.iana.org/assignments/dhcpv6-parameters.  The
   two messages are:

      The Encrypted-Query Message (TBA7), described in Section 10.2.

      The Encrypted-Response Message (TBA8), described in Section 10.2.

   The IANA is also requested to add three new registry tables to the
   DHCPv6 Parameters registry maintained in
   http://www.iana.org/assignments/dhcpv6-parameters.  The three tables
   are the Hash Algorithm for Secure DHCPv6 table, the Signature
   Algorithm for Secure DHCPv6 table and the Encryption Algorithm for
   Secure DHCPv6 table.

   Initial values for these registries are given below.  Future
   assignments are to be made through Standards Action [RFC5226].
   Assignments for each registry consist of a name, a value and a RFC
   number where the registry is defined.

   Hash Algorithm for Secure DHCPv6.  The values in this table are 8-bit
   unsigned integers.  The following initial values are assigned for
   Hash Algorithm for Secure DHCPv6 in this document:







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             Name        |  Value  |  RFCs
      -------------------+---------+--------------
         SigAlg-Combined |   ox00  | this document
            SHA-256      |   0x01  | this document
            SHA-512      |   0x02  | this document

   Signature Algorithm for Secure DHCPv6.  The values in this table are
   8-bit unsigned integers.  The following initial values are assigned
   for Signature Algorithm for Secure DHCPv6 in this document:

             Name        |  Value  |  RFCs
      -------------------+---------+--------------
         Non-SigAlg      |   0x00  | this document
       RSASSA-PKCS1-v1_5 |   0x01  | this document

   Encryption algorithm for Secure DHCPv6.  The values in this table are
   8-bit unsigned integers.  The following initial values are assigned
   for encryption algorithm for Secure DHCPv6 in this document:

             Name        |  Value  |  RFCs
      -------------------+---------+--------------
           Non-EncryAlg  |   0x00  | this document
              RSA        |   0x01  | this document

   IANA is requested to assign the following new DHCPv6 Status Codes,
   defined in Section 10.3, in the DHCPv6 Parameters registry maintained
   in http://www.iana.org/assignments/dhcpv6-parameters:

         Code  |           Name        |   Reference
      ---------+-----------------------+--------------
         TBD9  |   AuthenticationFail  | this document
         TBD10 |     ReplayDetected    | this document
         TBD11 |     SignatureFail     | this document

13.  Acknowledgements

   The authors would like to thank Tomek Mrugalski, Bernie Volz,
   Jianping Wu, Randy Bush, Yiu Lee, Sean Shen, Ralph Droms, Jari Arkko,
   Sean Turner, Stephen Farrell, Christian Huitema, Stephen Kent, Thomas
   Huth, David Schumacher, Francis Dupont, Gang Chen, Suresh Krishnan,
   Fred Templin, Robert Elz, Nico Williams, Erik Kline, Alan DeKok,
   Bernard Aboba, Sam Hartman, Zilong Liu and other members of the IETF
   DHC working group for their valuable comments.

   This document was produced using the xml2rfc tool [RFC2629].






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14.  Change log [RFC Editor: Please remove]

   draft-ietf-dhc-sedhcpv6-20: Correct a few grammar mistakes.

   draft-ietf-dhc-sedhcpv6-19: In client behavior part, we adds some
   description about opportunistic security.  In this way, in some
   scenario, authentication is optional.  Add the reference of RFC 4034
   for the encryption key tag calculation.  Delete the part that the
   relay agent cache server announcements part.  Add the assumption that
   the client's initial stored increasing number is set to zero.  In
   this way, for the first time increasing number check in the Reply
   message, the check will always succeed, and then the locally stored
   number is changed into the contained number in the Reply message.
   Correct many grammar mistakes.

   draft-ietf-dhc-sedhcpv6-18: Add the Algorithm option.  The algorithm
   option contains the EA-id List, SA-id List, HA-id List, and then the
   certificate and signature options do not contain the algorithm list;
   Add the Encryption Key Tag option to identify the used public/private
   key pair; Delete the AlgorithmNotSupported error status code; Delete
   some description on that secure DHCPv6 exchanges the server selection
   method; Delete the DecryptionFail error status code; For the case
   where the client's certificate is missed, then the server discards
   the received message.  Add the assumption that: For DHCPv6 client,
   just one certificate is used for the DHCPv6 configuration.  Add the
   statement that: For the first Encrypted-Query message, the server
   needs to try all the possible private keys and then records the
   relationship between the public key and the encryption key tag.

   draft-ietf-dhc-sedhcpv6-17: Change the format of the certificate
   option according to the comments from Bernie.

   draft-ietf-dhc-sedhcpv6-16: For the algorithm agility part, the
   provider can offer multiple EA-id, SA-id, HA-id and then receiver
   choose one from the algorithm set.

   draft-ietf-dhc-sedhcpv6-15: Increasing number option only contains
   the strictly increasing number; Add some description about why
   encryption is needed in Security Issues of DHCPv6 part;

   draft-ietf-dhc-sedhcpv6-14: For the deployment part, Tofu is out of
   scope and take Opportunistic security into consideration; Increasing
   number option is changed into 64 bits; Increasing number check is a
   separate section; IncreasingnumFail error status code is changed into
   ReplayDetected error status code; Add the section of "caused change
   to RFC3315";





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   draft-ietf-dhc-sedhcpv6-13: Change the Timestamp option into
   Increasing-number option and the corresponding check method; Delete
   the OCSP stampling part for the certificate check; Add the scenario
   where the hash and signature algorithms cannot be separated; Add the
   comparison with RFC7824 and RFC7844; Add the encryption text format
   and reference of RFC5652.  Add the consideration of scenario where
   multiple DHCPv6 servers share one common DHCPv6 server.  Add the
   statement that Encrypted-Query and Encrypted-Response messages can
   only contain certain options: Server Identifier option and Encrypted-
   message option.  Add opportunistic security for deployment
   consideration.  Besides authentication+encyrption mode, encryption-
   only mode is added.

   draft-ietf-dhc-sedhcpv6-12: Add the Signature option and timestamp
   option during server/client authentication process.  Add the hash
   function and signature algorithm.  Add the requirement: The
   Information-request message cannot contain any other options except
   ORO option.  Modify the use of "SHOULD"; Delete the reference of
   RFC5280 and modify the method of client/server cert verification; Add
   the relay agent cache function for the quick response when there is
   no authenticated server.  2016-4-24.

   draft-ietf-dhc-sedhcpv6-11: Delete the Signature option, because the
   encrypted DHCPv6 message and the Information-request message (only
   contain the Certificate option) don't need the Signature option for
   message integrity check; Rewrite the "Applicability" section; Add the
   encryption algorithm negotiation process; To support the encryption
   algorithm negotiation, the Certificate option contains the EA-
   id(encryption algorithm identifier) field; Reserve the Timestamp
   option to defend against the replay attacks for encrypted DHCPv6
   configuration process; Modify the client behavior when there is no
   authenticated DHCPv6 server; Add the DecryptionFail error code.
   2016-3-9.

   draft-ietf-dhc-sedhcpv6-10: merge DHCPv6 authentication and DHCPv6
   encryption.  The public key option is removed, because the device can
   generate the self-signed certificate if it is pre-configured the
   public key not the certificate. 2015-12-10.

   draft-ietf-dhc-sedhcpv6-09: change some texts about the deployment
   part.2015-12-10.

   draft-ietf-dhc-sedhcpv6-08: clarified what the client and the server
   should do if it receives a message using unsupported algorithm;
   refined the error code treatment regarding to AuthenticationFail and
   TimestampFail; added consideration on how to reduce the DoS attack
   when using TOFU; other general editorial cleanups. 2015-06-10.




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   draft-ietf-dhc-sedhcpv6-07: removed the deployment consideration
   section; instead, described more straightforward use cases with TOFU
   in the overview section, and clarified how the public keys would be
   stored at the recipient when TOFU is used.  The overview section also
   clarified the integration of PKI or other similar infrastructure is
   an open issue.  2015-03-23.

   draft-ietf-dhc-sedhcpv6-06: remove the limitation that only clients
   use PKI- certificates and only servers use public keys.  The new text
   would allow clients use public keys and servers use PKI-certificates.
   2015-02-18.

   draft-ietf-dhc-sedhcpv6-05: addressed comments from mail list that
   responsed to the second WGLC. 2014-12-08.

   draft-ietf-dhc-sedhcpv6-04: addressed comments from mail list.
   Making timestamp an independent and optional option.  Reduce the
   serverside authentication to base on only client's certificate.
   Reduce the clientside authentication to only Leaf of Faith base on
   server's public key. 2014-09-26.

   draft-ietf-dhc-sedhcpv6-03: addressed comments from WGLC.  Added a
   new section "Deployment Consideration".  Corrected the Public Key
   Field in the Public Key Option.  Added consideration for large DHCPv6
   message transmission.  Added TimestampFail error code.  Refined the
   retransmission rules on clients. 2014-06-18.

   draft-ietf-dhc-sedhcpv6-02: addressed comments (applicability
   statement, redesign the error codes and their logic) from IETF89 DHC
   WG meeting and volunteer reviewers. 2014-04-14.

   draft-ietf-dhc-sedhcpv6-01: addressed comments from IETF88 DHC WG
   meeting.  Moved Dacheng Zhang from acknowledgement to be co-author.
   2014-02-14.

   draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19.

   draft-jiang-dhc-sedhcpv6-02: removed protection between relay agent
   and server due to complexity, following the comments from Ted Lemon,
   Bernie Volz. 2013-10-16.

   draft-jiang-dhc-sedhcpv6-01: update according to review comments from
   Ted Lemon, Bernie Volz, Ralph Droms.  Separated Public Key/
   Certificate option into two options.  Refined many detailed
   processes.  2013-10-08.

   draft-jiang-dhc-sedhcpv6-00: original version, this draft is a
   replacement of draft-ietf-dhc-secure-dhcpv6, which reached IESG and



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   dead because of consideration regarding to CGA.  The authors followed
   the suggestion from IESG making a general public key based mechanism.
   2013-06-29.

15.  References

15.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,
              <http://www.rfc-editor.org/info/rfc3971>.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <http://www.rfc-editor.org/info/rfc4034>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", RFC 4443,
              DOI 10.17487/RFC4443, March 2006,
              <http://www.rfc-editor.org/info/rfc4443>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <http://www.rfc-editor.org/info/rfc5652>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <http://www.rfc-editor.org/info/rfc5905>.





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   [RFC6840]  Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
              Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
              DOI 10.17487/RFC6840, February 2013,
              <http://www.rfc-editor.org/info/rfc6840>.

   [RFC7283]  Cui, Y., Sun, Q., and T. Lemon, "Handling Unknown DHCPv6
              Messages", RFC 7283, DOI 10.17487/RFC7283, July 2014,
              <http://www.rfc-editor.org/info/rfc7283>.

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <http://www.rfc-editor.org/info/rfc7296>.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <http://www.rfc-editor.org/info/rfc7435>.

   [RFC7824]  Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
              Considerations for DHCPv6", RFC 7824,
              DOI 10.17487/RFC7824, May 2016,
              <http://www.rfc-editor.org/info/rfc7824>.

   [RFC7844]  Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
              Profiles for DHCP Clients", RFC 7844,
              DOI 10.17487/RFC7844, May 2016,
              <http://www.rfc-editor.org/info/rfc7844>.

15.2.  Informative References

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              DOI 10.17487/RFC2629, June 1999,
              <http://www.rfc-editor.org/info/rfc2629>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6273]  Kukec, A., Krishnan, S., and S. Jiang, "The Secure
              Neighbor Discovery (SEND) Hash Threat Analysis", RFC 6273,
              DOI 10.17487/RFC6273, June 2011,
              <http://www.rfc-editor.org/info/rfc6273>.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <http://www.rfc-editor.org/info/rfc7258>.




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   [RSA]      RSA Laboratories, "RSA Encryption Standard, Version 2.1,
              PKCS 1", November 2002.

Authors' Addresses

   Sheng Jiang
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   CN

   Email: jiangsheng@huawei.com


   Lishan Li
   Tsinghua University
   Beijing  100084
   P.R.China

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


   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6260-3059
   Email: yong@csnet1.cs.tsinghua.edu.cn


   Tatuya Jinmei
   Infoblox Inc.
   3111 Coronado Drive
   Santa Clara, CA
   US

   Email: jinmei@wide.ad.jp












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   Ted Lemon
   Nominum, Inc.
   2000 Seaport Blvd
   Redwood City, CA  94063
   USA

   Phone: +1-650-381-6000
   Email: Ted.Lemon@nominum.com


   Dacheng Zhang
   Beijing
   CN

   Email: dacheng.zhang@gmail.com




































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