Re: [dhcwg] I-D Action: draft-ietf-dhc-sedhcpv6-18.txt

Lishan Li <lilishan48@gmail.com> Tue, 20 December 2016 17:02 UTC

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From: Lishan Li <lilishan48@gmail.com>
Date: Wed, 21 Dec 2016 01:02:31 +0800
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To: "Bernie Volz (volz)" <volz@cisco.com>
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Subject: Re: [dhcwg] I-D Action: draft-ietf-dhc-sedhcpv6-18.txt
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2016-12-19 5:57 GMT+08:00 Bernie Volz (volz) <volz@cisco.com>;:

> Hi:
>
>
>
> I read through this draft and do have extensive comments. While there are
> a lot of improvements, I think some work is needed on the document. Please
> note that I still have to re-review some of section 6 and 7, but as there
> were plenty of comments already, I figured it best to provide you these
> earlier than waiting to finish (as it may also be a bit difficult to finish
> that review over the next several weeks because of the holidays).
>
[LS]: Thanks a lot for your valuable comments. Wish you have a happy
holidays in advance. For the details, please see inline.

>
>
> I’ve included much of the draft below as that makes it easier to comment
> on the issues. My comments should start with BV>.
>
>
>
> Let me first raise a few points to consider:
>
>
>
> -          A server could have multiple algorithms and (possibly multiple
> certificates) and so when a server receives a client’s Encrypted-Query
> message how does it decrypt it (choose from its algorithms or
> certificates)? If it tries several, how can it tell when it is successful?
> I guess by verifying the signature? But this also requires the server to
> decrypt the packet and look for this option – and the decrypted packet
> could be complete junk (which the server obviously should deal with but
> there is a risk that this junk could cause the server to crash)? I’m not
> sure if the Encryption Key Tag was supposed to provide for this as
> (commented below) there are no details on how this is generated (section
> 10.1.5 does not indicate anything useful). Also, having the server have to
> try to decrypt several times seems a bit costly to me. (Again, the server
> cannot even tell who the client is so there’s no easy way for the server
> even to remember this and associate it with something in the received
> packet.) I wonder whether there should be some mechanism for the server to
> provide some “encryption-id” to the client (in the Encrypted-Response)
> which the client then sends in an option in the Encrypted-Query so the
> server knows how to decrypt the message?
>
[LS]: According to RFC 4034, for the same problem, it define the key tag
calculation algorithm.
So it is better to define a mechanism for the encryption key tag
 calculation algorithm.
There are two method. First method: Maybe we can directly add the reference
of RFC 4034. Second method: As RFC 4034, we adds a new appendix for the
description of encryption key tag calculation algorithm. The input is the
data of the public key, and the output is the fingerprint of it. And we the
calculation method is the same as RFC 4034.

>
>
> -          Is Trust on First Use (TOFU) supported? It didn’t seem so?
> (Section 6 says to “or decide[d] to drop the message”). That may be fine
> and perhaps it was dropped in recent discussions (I had not followed all of
> them carefully). Or perhaps that will be for some follow on work.
>
[LS]: After the discussion, Ted suggested that: "on the ToFU question, we
should put ToFU in a separate experimental draft, but should include
Opportunistic Security in the base document, as Stephen requested".
So in section 6, we should add some description that in some scenario, such
as coffee shop, authentication is optional.

>
>
>
>
>                             Secure DHCPv6
>
>                        draft-ietf-dhc-sedhcpv6-18
>
>
>
> 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.
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                  [Page 2]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
> 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.
>
>
>
> BV> To be consistent, should “Encryption Key Tag” be changed to
> “Encryption-Key-Tag” throughout?
>
[LS]: Will modify it.

>
>
> 2.  Requirements Language and Terminology
>
>
>
> BV> Shouldn’t this just be Requirements Language as section 3 is
> Terminology? Or, perhaps combine these sections into one?
>
[LS]: Will modify the title as "Requirement 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.
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                  [Page 3]
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
> 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.
>
>
>
> BV> There are some other abbreviations used in this document that are not
> “defined” on first use and perhaps best added here? For example, PKI and CA
> (there may be others). Or, do you want to pull in terminology from a
> security document (RFC)?
>
[LS]: Have check the process method. For most document, in the body part,
it describe in this way: Public Key Infrastructure (PKI), Certification
Authority (CA). So maybe we should add the full terminology, not only the
abbreviation in the first time.

>
>
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.
>
> BV> Not sure if it matters, but this was deprecated in 3315bis?
>
[LS]: But if we describes the mechanism of 3315bis, then we should add it
as normative reference?

>
>
>    For this approach, operators can set up a key database for both
>
>    servers and clients from which the client obtains a key before
>
>    running DHCPv6.  However, manual key distribution runs counter to the
>
>    goal of minimizing the configuration data needed at each host.
>
>    Consequently, there are no known deployments of this security
>
>    mechanism.
>
>
>
>    [RFC3315] provides an additional mechanism for preventing off-network
>
>    timing attacks using the Reconfigure message: the Reconfigure Key
>
>    authentication method.  However, this method protects only the
>
>    Reconfigure message.  The key is transmitted in plaintext to the
>
>    client in earlier exchanges and so this method is vulnerable to on-
>
>    path active attacks.
>
>
>
>    Anonymity Profile for DHCP Clients [RFC7844] explains how to generate
>
>    DHCPv4 or DHCPv6 requests that minimize the disclosure of identifying
>
>    information.  However, the anonymity profile limits the use of the
>
>    certain options.  It also cannot anticipate new options that may
>
>    contain private information is defined.  In addition, the anonymity
>
> BV> Drop “is defined”?
>
[LS]: Will modify it.

>    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.
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                  [Page 4]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>    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 secure DHCPv6 procedure.  Briefly,
>
> BV> add the (illustrates the secure)
>
[LS]: Will modify it.

>    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
>
> BV> Then should be the?
>
[LS]: Got it.

>    client and server.  The Increasing number option is defined to detect
>
>    replay attack.
>
> BV> a replay attack (or replay attacks)?
>
[LS]: Got it.

>
>
>
>
> Jiang, et al.             Expires June 7, 2017                  [Page 5]
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>            +-------------+                           +-------------+
>
>            |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
>
>       Timestamp is one of the possible implementation choices.  The
>
> BV> What is “The Timestamp”? Drop this sentence or perhaps provide more on
> what that is?
>
[LS]: Will drop this sentence. In the following, for the grammar mistakes,
I will not reply it and modify it according to your comments in the next
version.

>
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                  [Page 6]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>       Increasing-number option is defined to carry a strictly-increasing
>
>       serial number.
>
>
>
>    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.  In addition, the Server
>
>       Identifier option MUST be contained if it is contained in the
>
> BV> chain be contained to be included? Kind of odd to so contained twice?
>
      original DHCPv6 message.  The Encrypted-Query message MUST NOT
>
>       contain other options except the above options.
>
> BV> Later on page 10 it is stated that the Encrypted-Query can also
> contain the Encryption-Key-Tag option?
>

>
>    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 except it.
>
> BV> Drop “except it”? Other already makes that clear?
>
>
>
>
>
> BV> So with respect to the Encrypted-Query and the Server Identifier
> option. When the client sends a Solicit (Confirm or Rebind) and there is no
> Server-Identifier, this will go to all servers but they probably won’t be
> able to decrypt? Does that make sense? Should the Server Identifier ALSO be
> in the Encrypted-Query (I’m NOT suggesting to allow it in the Client’s
> Solicit, Confirm, Rebind!)
>
>
>
> BV> Also, given that the WG is working on Failover Protocol in parallel,
> how would seDHCPv6 work with Failover? And should we consider anything
> related to this. One possibility is that the failover partners could
> exchange some information (so we might have to define a new failover option
> eventually). But then my comment above about the Server Identifier may
> cause other issues? It may just be that once a client picks one of the
> failover partners, it will have to stick with that partner or return to the
> server discovery phase? But that would be too bad. (I had thought about
> whether the failover partners should share a Server Identifier, but that
> likely complicates other cases so not sure it is best.) Perhaps when the
> failover partners exchange the above mentioned information, that could
> include the Server Identifier which would allow them to be used.
>
[LS]: Sorry for not reviewing the draft. Will review it and reply to you
later.

>
>
> 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.  Caused change to RFC3315
>
>
>
> BV> Odd title. Perhaps “Impact on RFC3315” or something similar?
>
>
>
>    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 more wide use of secure DHCPv6, opportunistic security
>
> BV> replace more wide with wider?
>
>    [RFC7435] can be applied to secure DHCPv6 deployment, which allows
>
>    DHCPv6 encryption in environments where support for authentication is
>
>    not available.
>
> BV> perhaps “for authentication or a key distribution mechanism”?
>
>
>
>    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
>
>    don't want to be blocked from the Internet, then the DHCPv6
>
> BV> replace don’t want… with “one wants access to the Internet”?
>
>    configuration process can be encrypted without authentication.
>
>
>
>    Note that this deployment scenario based on manual operation is not
>
>    different very much from the existing, shared-secret based
>
> BV> replace different very much with “much different”?
>
>    authentication mechanisms defined in [RFC3315] in terms of
>
>    operational costs.  However, Secure DHCPv6 is still securer than the
>
>    shared-secret mechanism in that even if clients' keys stored for the
>
>    server are stolen that does not mean an immediate threat as these are
>
>    public keys.  In addition, if some kind of PKI is used with Secure
>
> BV> See earlier, but PKI not defined.
>
>    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 CA, it can generate the self-
>
> BV> See earlier, CA not defined?
>
>    signed certificate.
>
>
>
>    The secure DHCPv6 client sends Information-request message as per
>
> BV> sends an Information-request message (or sends Information-request
> messages)?
>
>    [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 client's privacy information leakage.
>
> BV> add the (the client’s)
>
>
>
>    When receiving the Reply messages from DHCPv6 servers, a secure
>
> BV> add the (the DHCPv6 servers)
>
>    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.  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.  At this
>
>    point, the client has either recognized the certificate of the
>
>    server, or decided to drop the message.
>
> BV> decided -> decide?
>
>
>
>    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
>
> BV> If this is the first message, what can client validate the Increasing
> Number against? From the flow, we are just in processing the Reply from the
> Information-Request so there is unlikely to be any information? Or is
> client expected to remember past values from a specific Server-ID?
>
[LS]: The reply message is the first message that contains the
increasing-number option. So, the
client does not verify it, but record the value of the locally stored
increasing number as the value of it.

>    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 if it is
>
>    contained.  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
>
> BV> How are these multiple DHCPv6 certs received? I think you mean if
> multiple servers responded (hence multiple certs), the client has to pick
> one? I think stating this more clearly would be good?
>
>    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
>
>    client conducts the server discovery process as per section 18.1.5 of
>
>
>
>
>
>
>
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>
>
>
>
>    [RFC3315] to avoid the packet storm.  In this way, it is difficult
>
> BV> avoid a packet storm?
>
>    for the rogue server to beat out a busy "real" server.  And then the
>
> BV> change the rogue to a rogue?
>
>    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
>
> BV> I don’t see that section 10.1.5 provides really any useful explanation
> as to how this data is constructed? Also, as I believe the server is
> supposed to use this information, how does it make sense for the client to
> generate it? If there is a clear algorithm that both the client and server
> can use to generate this (and the server has what it needs), OK. But more
> details are needed!!
>
[LS]: As stated above, the calculation algorithm is needed and will be
added.

>    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 can also contain
>
>    the Increasing-number option to defend against replay attack.
>
> BV> Might help to clarify where this Increasing-Number option goes (in the
> client’s message).
>
[LS]: Will add the explanation of it.

>
>
>    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
>
>    the Encrypted-Query message to another authenticated server(s) for
>
>
>
>
>
>
>
>
>
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>
>
>
>
>    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 DecryptionFail error status code, the client MAY
>
>       resend the message following 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].
>
>
>
> BV> I’m really not sure whether these errors are helpful. Since how can
> the server even construct these in many cases and how can the client trust
> these if they aren’t authenticated?
>
[LS]: After the server's identify is verified, then the client sends its
certificate, signature, increasing-num and then it may receive the above
error status code.

>
>
> (BV> I am still working through section 7 so may have more comments
> later). But, I did look at later sections so …
>
>
>
>
>
> 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.
>
>
>
>    Relay agent is RECOMMENDED to cache server announcements to form the
>
>    list of the available DHCPv6 server certs.  If the relay agent
>
> BV> NO! I do not think this is a wise idea at all. Please remove this!
> Relays should not do this!
>
[LS]: In the before, Ted suggested us to add this part. What is the caused
problem? Looking forward to your guidance.

>
>
>
>
>
>
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>
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>
>
>
>
>
>    receives the Information-request message, then it replies with a list
>
>    of server certs available locally.  In this way, the client can be
>
>    confident of a quick response, and therefore treat the lack of a
>
>    quick response as an indication that no authenticated DHCP servers
>
>    exist.
>
>
>
> 9.  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
>
>    information after the transaction is finished.
>
>
>
>    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
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
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>
>
>
>
> 10.1.1.  Algorithm Option
>
>
>
>    The Algorithm option carries the algorithms sets for algorithm
>
>    agility, which is sent from the client to server.
>
> BV> Might help if you indicated exactly where (in which message(s)) this
> option is in. Same goes for the other options defined later. In this case
> also, I think this is ONLY sent 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_SIGNATURE         |         option-len            |
>
> BV> Isn’t this OPTION_ALGORITHM
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    .                          EA-id List                           .
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    .                          SA-id List                           .
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    .                          HA-id List                           .
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>                         Figure 2: Algorithm Option
>
>
>
>    o  option-code: OPTION_SIGNATURE (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-num              |               EA-id           |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    .                              ...                              .
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    |               EA-id           |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>    EA-num         The number of the following EA-ids.
>
> BV> Sadly RFC 7227 never defined a case like this and I think the WG
> should consider whether this should be LENGTH or a number of items.
> Personally, I prefer this to be a length (so EA-len which is 2 * number of
> EA-ids). Same goes for SA and HA. BUT I think this is something that the
> working group needs to consider. I was going to try to review other options
> to see if we had any that might resolve this but haven’t do that review
> (though nothing obvious comes to mind).
>
[LS]: Will change EA-num into EA-len.

>
>
>    EA-id          Encryption Algorithm id. The encryption algorithm
>
>                   is used for the encrypted DHCPv6 configuration
>
>                   process. This design is adopted in order to provide
>
>                   encryption algorithm agility. The value is from the
>
>                   Encryption Algorithm for Secure DHCPv6 registry in
>
>                   IANA. A registry of the initial assigned values
>
>                   is defined in Section 12. The mandatory encryption
>
>                   algorithms MUST be included.
>
> BV> This never says that this is a 2-octet value? Please be clear about
> that. Same goes for SA and HA below.
>
> BV> I think also saying something like “The client enumerates the list of
> Encryption algorithms it supports to the server” would be extremely useful
> for the EA-List (with similar text for the SA and HA lists)?
>
>
>
>                         Figure 3: EA-id List Field
>
>
>
>
>
>
>
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>
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>
>
>
>
>
>    o  SA-id List: The format of the SA-id List field is shown in
>
>       Figure 4.
>
>
>
> 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-num              |               SA-id           |
>
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> .                              ...                              .
>
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> |               SA-id           |
>
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
> SA-num         The number of the following SA-ids.
>
>
>
> SA-id          Signature Algorithm id. 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.
>
>
>
>     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-num              |               HA-id           |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    .                              ...                              .
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    |               HA-id           |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>    HA-num         The number of the following HA-ids.
>
>
>
>    HA-id          Hash Algorithm id. 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
>
>
>
>
>
>
>
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>
>
>
>
> 10.1.2.  Certificate Option
>
>
>
>    The Certificate option carries the certificate of the client/server.
>
>    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.  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.  If the value of EA-id is 0, then the certificate is
>
>       not used for encryption.
>
> BV> This seems a bit odd … shouldn’t this just say the Encryption
> Algorithm ID used for this certificate?
>

>
>    o  SA-id: Signature Algorithm id.  The signature algorithm is used
>
>       for computing the signature result.  The value is from the
>
>       Signature Algorithm for Secure DHCPv6 registry in IANA.  A
>
>       registry of the initial assigned values is defined in Section 12.
>
>       If the value of SA-id is 0, then the certificate is not used for
>
>       signature check.
>
> BV> Same – see above for EA-id?
>
>
>
>    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 all 0, it makes no sense and MUST NOT be used.
>
> BV> Perhaps say “… are both 0 makes no sense and the client MUST discard a
> message with such values”?
>
>
>
>
>
>
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                 [Page 17]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
> 10.1.3.  Signature option
>
>
>
>    The Signature option allows a signature that is signed by the private
>
>    key to be attached to a DHCPv6 message.  The Signature option could
>
>    be in any place within the DHCPv6 message while it is logically
>
>    created after the entire DHCPv6 header and options.  It protects the
>
>    entire DHCPv6 header and options, including itself.  The format of
>
>    the Signature option is described as follows:
>
>
>
>     0                   1                   2                   3
>
>    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    |     OPTION_SIGNATURE          |        option-len             |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    |         SA-id                 |            HA-id              |
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    |                                                               |
>
>    .                    Signature (variable length)                .
>
>    .                                                               .
>
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>                         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
>
>       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
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                 [Page 18]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>       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.  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             |
>
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> |                                                               |
>
> |                  InreasingNum (64-bit)                        |
>
> BV> Increasing-Num? (also use – below?)
>
> |                                                               |
>
> |                                                               |
>
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
> option-code    OPTION_INCREASING_NUM (TBA4).
>
>
>
> option-len     8, in octets.
>
>
>
> IncreasingNum  A strictly increasing number for the replay attack detection
>
>                which is more than the local stored number.
>
>
>
>                     Figure 8: Increasing-number Option
>
>
>
> 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.
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                 [Page 19]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>       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          |
>
> BV> Earlier you placed option name – OPTION_ENCRYPTION_KEY_TAG
>
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>      |                                                               |
>
>      .                    encryption key tag                         .
>
>      .                       (variable)                              .
>
>      .                                                               .
>
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>                     Figure 9: Encryption Key Tag Option
>
>
>
>    option-code  OPTION_ENCRY_KT (TBA5).
>
> BV> I’d recommend OPTION_ENCRYPTION_KEY_TAG as it isn’t that long and more
> clear?
>
>
>
>    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.
>
>
>
> BV> This is really unclear to me? How is this calculated? I think more
> details are needed as client generates this from server’s data so server
> must know how client generated it?
>
[LS]: Will add the calculation algorithm.

>
>
> 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 format of the Encrypted-message option is:
>
>
>
>       0                   1                   2                   3
>
>       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>      |          option-code          |           option-len          |
>
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>      |                                                               |
>
>      .                  encrypted DHCPv6 message                     .
>
>      .                       (variable)                              .
>
>      .                                                               .
>
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
>
>                     Figure 10: Encrypted-message Option
>
>
>
>    option-code  OPTION_ENCRYPTED_MSG (TBA6).
>
>
>
>    option-len  Length of the encrypted DHCPv6 message.
>
>
>
>
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                 [Page 20]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>    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.
>
>
>
>    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.
>
>
>
>
>
>
>
> Jiang, et al.             Expires June 7, 2017                 [Page 21]
>
>
>
> Internet-Draft                  SeDHCPv6                   December 2016
>
>
>
>
>
>    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.
>
>
>
>    A server, whose local policy accepts messages without a Increasing-
>
>    number option, may have to face the risk of replay attacks.
>
> BV> Isn’t this also an issue for the client?
>
[LS]: Will add the client.

>
>
>    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.
>
> BV> Isn’t this related to the 2nd paragraph in this section? Perhaps move
> this as third paragraph?
>
[LS]: Will move it.

>
>
>    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.
>
> BV> Are there any recommendations we could make about this? Perhaps this
> is more related to client configuration but perhaps in some cases client
> certificates could be tied to specific server certificates by configuration?
>
[LS]: So we can adds one statement for in the end of this paragraph: For
this security item, It is RECOMMENDED that client certificates could be
tied to specific server certificates by configuration.

Best Regards,
Lishan

>
>
>
>
> *From:* dhcwg [mailto:dhcwg-bounces@ietf.org] *On Behalf Of *Lishan Li
> *Sent:* Monday, December 05, 2016 10:59 AM
> *To:* dhcwg <dhcwg@ietf.org>;
> *Subject:* Re: [dhcwg] I-D Action: draft-ietf-dhc-sedhcpv6-18.txt
>
>
>
> Dear All,
>
>
>
> We have submitted the new version of secure DHCPv6.
>
> In the new version, we made the following updates:
>
> 1. Add the Algorithm option, Encryption Key Tag option;
>
> 2. Delete the AlgorithmNotSupported error status code;
>
> 3. Delete some description on that secure DHCPv6
>
>     exchanges the server selection method;
>
> 4. Add the assumption that: For DHCPv6 client, just one
>
>     certificate is used for the DHCPv6 configuration;
>
> 5. 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;
>
> 5. For the case where the client's certificate is missed
>
>     and decryption fails, the server discards the received
>
>     message.
>
>
>
> Could you please review the current version? Looking
>
> forward to your guidance.
>
>
>
> Best Regards,
>
> Lishan
>
>
>
> 2016-12-05 16:03 GMT+08:00 <internet-drafts@ietf.org>;:
>
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> This draft is a work item of the Dynamic Host Configuration of the IETF.
>
>         Title           : Secure DHCPv6
>         Authors         : Sheng Jiang
>                           Lishan Li
>                           Yong Cui
>                           Tatuya Jinmei
>                           Ted Lemon
>                           Dacheng Zhang
>         Filename        : draft-ietf-dhc-sedhcpv6-18.txt
>         Pages           : 30
>         Date            : 2016-12-05
>
> 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.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-dhc-sedhcpv6/
>
> There's also a htmlized version available at:
> https://tools.ietf.org/html/draft-ietf-dhc-sedhcpv6-18
>
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-dhc-sedhcpv6-18
>
>
> Please note that it may take a couple of minutes from the time of
> submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
> _______________________________________________
> dhcwg mailing list
> dhcwg@ietf.org
> https://www.ietf.org/mailman/listinfo/dhcwg
>
>
>