Internet DRAFT - draft-wkumari-dhc-addr-notification
draft-wkumari-dhc-addr-notification
Dynamic Host Configuration W. Kumari
Internet-Draft Google, LLC
Intended status: Standards Track S. Krishnan
Expires: 1 October 2023 R. Asati
Cisco Systems, Inc.
L. Colitti
J. Linkova
Google, LLC
30 March 2023
Registering Self-generated IPv6 Addresses using DHCPv6
draft-wkumari-dhc-addr-notification-07
Abstract
This document defines a method to inform a DHCPv6 server that a
device has a self-generated or statically configured address.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://wkumari.github.io/draft-wkumari-dhc-addr-notification/draft-
wkumari-dhc-addr-notification.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-
wkumari-dhc-addr-notification/.
Discussion of this document takes place on the Dynamic Host
Configuration Working Group mailing list (mailto:dhcwg@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/dhcwg/.
Subscribe at https://www.ietf.org/mailman/listinfo/dhcwg/.
Source for this draft and an issue tracker can be found at
https://github.com/wkumari/draft-wkumari-dhc-addr-notification.
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
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working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on 1 October 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Description of Mechanism . . . . . . . . . . . . . . . . . . 3
4. DHCPv6 ADDR-REG-INFORM Message . . . . . . . . . . . . . . . 4
5. DHCPv6 ADDR-REG-REPLY Message . . . . . . . . . . . . . . . . 5
6. DHCPv6 Address Registration Procedure . . . . . . . . . . . . 6
6.1. DHCPv6 Address Registration Request . . . . . . . . . . . 6
6.2. DHCPv6 Address Registration Acknowledgement . . . . . . . 7
6.3. Registration Expiry and Refresh . . . . . . . . . . . . . 7
6.4. Retransmission . . . . . . . . . . . . . . . . . . . . . 8
7. Host configuration . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Normative References . . . . . . . . . . . . . . . . . . . . 9
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
It is very common operational practice, especially in enterprise
networks, to use IPv4 DHCP logs for troubleshooting or security
purposes. Examples of this include a helpdesk dealing with a ticket
such as "The CEO's laptop cannot connect to the printer"; if the MAC
address of the printer is known (for example from an inventory
system), the IPv4 address can be retrieved from the DHCP logs and the
printer pinged to determine if it is reachable. Another common
example is a Security Operations team discovering suspicious events
in outbound firewall logs and then consulting DHCP logs to determine
which employee's laptop had that IPv4 address at that time so that
they can quarantine it and remove the malware.
This operational practice relies on the DHCP server knowing the IP
address assignments. Therefore, the practice does not work if static
IP addresses are manually configured on devices or self-assigned
addresses (such as when self-configuring an IPv6 address using SLAAC
[RFC4862]) are used.
The lack of this parity with IPv4 is one of the reasons that some
enterprise networks are unwilling to deploy IPv6.
This document provides a mechanism for a device to inform the DHCPv6
server that it has a self-configured IPv6 address (or has a
statically configured address), and thus provides parity with IPv4 in
this aspect.
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Description of Mechanism
After successfully assigning a self-generated IPv6 address on one of
its interfaces, an end-host implementing this specification SHOULD
multicast an ADDR-REG-INFORM message in order to inform the DHCPv6
server that this address is in use.
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+----+ +----------------+ +---------------+
|Host| |First-hop router| |Addr-Reg Server|
+----+ +----------------+ +---------------+
| SLAAC | |
|<--------->| |
| | |
| | ADDR-REG-INFORM |
|------------------------------------------------->|
| | |Register / log
| | ADDR-REG-REPLY |address
|<-------------------------------------------------
Figure 1: Address Registration Procedure
4. DHCPv6 ADDR-REG-INFORM Message
The DHCPv6 client sends an ADDR-REG-INFORM message to inform that an
IPv6 address is in use. The format of the ADDR-REG-INFORM message 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type | transaction-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. options .
. (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
msg-type Identifies the DHCPv6 message type;
Set to ADDR-REG-INFORM (TBA1).
transaction-id The transaction ID for this message exchange.
options Options carried in this message.
Figure 2: DHCPv6 ADDR-REG-INFORM message
The ADDR-REG-INFORM message MUST NOT contain server-identifier option
and MUST contain the IA Address option. The ADDR-REG-INFORM message
is dedicated for clients to initiate an address registration request
toward an address registration server. Consequently, clients MUST
NOT put any Option Request Option(s) in the ADDR-REG-INFORM message.
Clients MAY include other options, such as the Client FQDN Option
[RFC4704].
Clients MUST discard any received ADDR-REG-INFORM messages.
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Servers MUST discard any ADDR-REG-INFORM messages that meet any of
the following conditions:
* the address is not appropriate for the link;
* the message does not include a Client Identifier option;
* the message includes a Server Identifier option;
* the message does not include the IA Address option;
* the message includes an Option Request Option.
5. DHCPv6 ADDR-REG-REPLY Message
The DHCPv6 server sends an ADDR-REG-REPLY message in response to a
valid ADDR-REG-INFORM message. The format of the ADDR-REG-REPLY
message 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type | transaction-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. options .
. (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
msg-type Identifies the DHCPv6 message type;
Set to ADDR-REG-REPLY (TBA2).
transaction-id The transaction ID for this message exchange.
options Options carried in this message.
Figure 3: DHCPv6 ADDR-REG-REPLY message
The ADDR-REG-INFORM message MUST contain an IA Address option for the
address being registered.
Servers MUST ignore any received ADDR-REG-REPLY messages.
The IPv6 destination address of the packet is the address being
registered.
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6. DHCPv6 Address Registration Procedure
The DHCPv6 protocol is used as the address registration protocol when
a DHCPv6 server performs the role of an address registration server.
The DHCPv6 IA Address option [RFC8415] is adopted in order to fulfill
the address registration interactions.
6.1. DHCPv6 Address Registration Request
The end-host sends a DHCPv6 ADDR-REG-INFORM message to the address
registration server to the All_DHCP_Relay_Agents_and_Servers
multicast address (ff02::1:2). The host MUST only send the packet on
the network interface that has the address being registered (i.e. if
the host has multiple interfaces with different addresses, it should
only send the packet on the interface with the address being
registered). The host MUST send the packet from the address being
registered. This is primarily for "fate sharing" purposes - for
example, if the network implements some form of L2 security to
prevent a client from spoofing other clients' addresses this prevents
an attacker from spoofing ADDR-REG-INFORM messages. The host MUST
send separate messages for each address being registered.
The end-host MUST include a Client Identifier option in the ADDR-REG-
INFORM message.
The host MUST only send the ADDR-REG-INFORM message for valid
([RFC4862]) addresses of global scope ([RFC4007]). The host MUST NOT
send the ADDR-REG-INFORM message for addresses configured by DHCPv6.
The host MUST NOT send the ADDR-REG-INFORM message if it has not
received any Router Advertisement message with either M or O flags
set to 1.
After receiving this ADDR-REG-INFORM message, the address
registration server SHOULD verify that the address being registered
is "appropriate to the link" as defined by [RFC8415]. If the server
believes that address being registered is not appropriate to the
link [RFC8415], it MUST drop the message, and SHOULD log this fact.
If the address is appropriate, the server:
* SHOULD register or update a binding between the provided Client
Identifier and IPv6 address in its database;
* SHOULD log the address registration information (as is done
normally for clients which have requested an address), unless
configured not to do so;
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* SHOULD mark the address as unavailable for use and not include it
in future ADVERTISE messages.
* SHOULD send back an ADDR-REG-REPLY message.
If the DHCPv6 server does not support the address registration
function, it MUST drop the message, and SHOULD log this fact.
DHCPv6 relay agents and switches that relay address registration
messages directly from clients SHOULD include the client's link-layer
address in the relayed message using the Client Link-Layer Address
option ([RFC6939])
6.2. DHCPv6 Address Registration Acknowledgement
The server SHOULD acknowledge receipt of an ADDR-REG-INFORM message
by sending a ADDR-REG-REPLY message back. The ADDR-REG-REPLY message
only indicates that the ADDR-REG-INFORM message has been received.
It MUST NOT be considered as any indication of the address validity
and MUST NOT be required for the address to be usable. DHCPv6
relays, or other devices that snoop ADDR-REG-REPLY messages, MUST NOT
add or alter any forwarding or security state based on the ADDR-REG-
REPLY message.
6.3. Registration Expiry and Refresh
The client MUST refresh the registration every AddrRegRefresh
seconds, where AddrRegRefresh is min(1/3 of the Valid Lifetime filed
in the very first PIO received to form the address; 4 hours ).
Registration refresh packets SHOULD be retransmitted using the same
logic as described in the 'Retransmission' section below. In
particular, retransmissions SHOULD be jittered to avoid
synchronization causing a large number of registrations to expire at
the same time.
If the address registration server does not receive such a refresh
after the preferred lifetime has passed, it SHOULD remove the record
of the Client-Identifier-to-IPv6-address binding.
The client MAY choose to notify the server when an address is no
longer being used (the client is disconnecting from the network, the
address lifetime expired or the address is being removed from the
interface). To indicate that the address is not being used anymore
the client MUST set the preferred-lifetime and valid-lifetime fields
of the IA Address option to zero.
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6.4. Retransmission
To reduce the effects of packet loss on registration, the client
SHOULD retransmit the registration message. Retransmissions SHOULD
follow the standard retransmission logic specified by section 15 of
[RFC8415] with the following default parameters:
* IRT 1 sec
* MRC 3
The client SHOULD allow these parameters to be configured by the
administrator.
If an ADDR-REG-REPLY message is received for the address being
registered, the client MUST stop retransmission. However, the client
can not rely on the server acknowledging receipt of the registration
message, because the server might not support address registration.
7. Host configuration
DHCP clients SHOULD allow the administrator to disable sending ADDR-
REG-INFORM messages. This could be used, for example, to reduce
network traffic on networks where the servers are known not to
support the message type. Sending the messages SHOULD be enabled by
default.
8. Security Considerations
An attacker may attempt to register a large number of addresses in
quick succession in order to overwhelm the address registration
server and / or fill up log files. These attacks may be mitigated by
using generic DHCPv6 protection such as the AUTH option [RFC8415].
The similar attack vector exist today, e.g. an attacker can DoS the
server with messages contained spoofed DUIDs.
If a network is using FCFS SAVI [RFC6620], then the DHCPv6 server can
trust that the ADDR-REG-INFORM message was sent by the legitimate
owner of the address. This prevents a host from registering an
address owned by another host.
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One of the use-cases for the mechanism described in this document is
to identify sources of malicious traffic after the fact. Note,
however, that as the device itself is responsible for informing the
DHCPv6 server that it is using an address, a malicious or compromised
device can simply not send the ADDR-REG-INFORM message. This is an
informational, optional mechanism, and is designed to aid in
troubleshooting and forensics. On its own, it is not intended to be
a strong security access mechanism.
9. IANA Considerations
This document defines a new DHCPv6 message, the ADDR-REG-INFORM
message (TBA1) described in Section 4, that requires an allocation
out of the registry of Message Types defined at
http://www.iana.org/assignments/dhcpv6-parameters/
10. 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,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
DOI 10.17487/RFC4007, March 2005,
<https://www.rfc-editor.org/rfc/rfc4007>.
[RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for
IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
Option", RFC 4704, DOI 10.17487/RFC4704, October 2006,
<https://www.rfc-editor.org/rfc/rfc4704>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/rfc/rfc4862>.
[RFC6939] Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer
Address Option in DHCPv6", RFC 6939, DOI 10.17487/RFC6939,
May 2013, <https://www.rfc-editor.org/rfc/rfc6939>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
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[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/rfc/rfc8415>.
Acknowledgments
Much thanks to Bernie Volz for significant review and feedback, as
well as Stuart Cheshire, Alan DeKok, Ryan Globus, Erik Kline, Ted
Lemon, Eric Levy-Abegnoli, Mark Smith, Eric Vynke, Timothy Winter for
their feedback, comments and guidance.
This document borrows heavily from a previous document, draft-ietf-
dhc-addr-registration, which defined "a mechanism to register self-
generated and statically configured addresses in DNS through a DHCPv6
server". That document was written Sheng Jiang, Gang Chen, Suresh
Krishnan, and Rajiv Asati.
Contributors
Gang Chen
China Mobile
53A, Xibianmennei Ave.
Xuanwu District
Beijing
P.R. China
Email: phdgang@gmail.com
Authors' Addresses
Warren Kumari
Google, LLC
Email: warren@kumari.net
Suresh Krishnan
Cisco Systems, Inc.
Email: suresh.krishnan@gmail.com
Rajiv Asati
Cisco Systems, Inc.
7025 Kit Creek road
Research Triangle Park, 27709-4987
United States of America
Email: rajiva@cisco.com
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Lorenzo Colitti
Google, LLC
Shibuya 3-21-3,
Japan
Email: lorenzo@google.com
Jen Linkova
Google, LLC
1 Darling Island Rd
Pyrmont 2009
Australia
Email: furry@google.com
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