Dynamic Host Configuration W. Kumari
Internet-Draft Google, LLC
Intended status: Experimental S. Krishnan
Expires: 8 September 2022 Kaloom
S. Jiang
R. Asati
Cisco Systems, Inc.
7 March 2022
Registering Self-generated IPv6 Addresses using DHCPv6
draft-wkumari-dhc-addr-notification-00
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/.
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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Description of Mechanism . . . . . . . . . . . . . . . . . . 4
4. DHCPv6 ADDR-REG-NOTIFICATION Message . . . . . . . . . . . . 4
5. DHCPv6 Address Registration Procedure . . . . . . . . . . . . 5
5.1. DHCPv6 Address Registration Request . . . . . . . . . . . 6
5.2. Registration Expiry and Refresh . . . . . . . . . . . . . 6
5.3. Acknowledging Registration and Retransmission . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7.1. Value Description Reference . . . . . . . . . . . . . . . 8
7.2. Code Name Reference . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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.
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".
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.
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3. Description of Mechanism
After successfully assigning a self-generated IPv6 address on one of
its interfaces, an end-host implementing this specification SHOULD
send an ADDR-REG-NOTIFICATION message to a DHCPv6 address
registration server. After receiving the address registration
request, the DHCPv6 server records and logs the IPv6 address. An
acknowledgement MUST be sent back to the end host to indicate whether
or not the registration operation succeeded.
+----+ +-----------+ +---------------+
|Host| |Edge router| |Addr-Reg Server|
+----+ +-----------+ +---------------+
| SLAAC | |
|<--------->| |
| | |
| | ADDR-REG-NOTIFICATION |
|-------------------------------------------->|
| | |Register / log
| | |address
| | Acknowledgment |
|<--------------------------------------------|
Figure 1: Address Registration ProcedureAddress Registration
Procedure
The registration server MAY apply certain filter/accept criteria for
address registration requests (for example to deny registration of
addresses that are not appropriate for the link, etc.)
4. DHCPv6 ADDR-REG-NOTIFICATION Message
The DHCPv6 client sends an ADDR-REG-NOTIFICATION message to a server
to request that the use of this address be registered and logged.
The format of the ADDR-REG-NOTIFICATION message is described as
follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type | transaction-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. options .
. (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
msg-type Identifies the DHCPv6 message type;
Set to ADDR-REG-NOTIFICATION (TBA1).
transaction-id The transaction ID for this message exchange.
options Options carried in this message.
Figure 2: DHCPv6 ADDR-REG-NOTIFICATION message
The ADDR-REG-NOTIFICATION message MUST NOT contain server-identifier
option and MUST contain the IA Address option. The ADDR-REG-
NOTIFICATION 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-NOTIFICATION message.
Clients MUST discard any received ADDR-REG-NOTIFICATION messages.
Servers MUST discard any ADDR-REG-NOTIFICATION messages that meet any
of the following conditions:
* the message does not include a Client Identifier option;
* the message includes a Server Identifier option;
* the message does not include at least one IA Address option;
* the message includes an Option Request Option.
5. 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 [RFC3315]is adopted in order to fulfill
the address registration interactions.
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5.1. DHCPv6 Address Registration Request
The end-host sends a DHCPv6 ADDR-REG-NOTIFICATION message to the
address registration server to the All_DHCP_Relay_Agents_and_Servers
multicast address (ff02::1:2). The host SHOULD send the packet from
the address being registered.
The end-host MUST include a Client Identifier option and at least one
IA Address option in the ADDR-REG-NOTIFICATION message. The host
SHOULD send separate messages for each address (so each message
include only one IA Address option) but MAY send a single packet
containing multiple options.
The host MUST NOT send the ADDR-REG-NOTIFICATION message for
addresses which are not in "preferred" (RFC4862) state.
{TODO (WK): DHCPv6 uses "DHCP Unique Identifier (DUID)" to identify
clients. This doesn't really meet our design goal of "what IP does
the printer have?!". One of the DUID types is "DUID Based on Link-
layer Address (DUID-LL)", but this is "any one network interface(s)"
- this is probably good enough for the inventory use case, but still
not ideal}
After receiving this ADDR-REG-NOTIFICATION message, the address
registration server MUST register the binding between the provided
Client Identifier and IPv6 address. If the DHCPv6 server does not
support the address registration function, it MUST drop the message
(and may log the event).
5.2. Registration Expiry and Refresh
For every successful binding registration, the address registration
server MUST record the Client-Identifier-to-IPv6-address bindings and
associated valid-lifetimes in its storage, and SHOULD log this
information in a manner similar to if it had performed the
assignment.
If a ADDR-REG-NOTIFICATION message updates the existing Client-
Identifier-to-IPv6-address binding the server MAY log the event.
The address registration client MUST refresh the registration before
it expires (i.e. before the preferred lifetime of the IA address
elapses) by sending a new ADDR-REG-NOTIFICATION to the address
registration server. 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.
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It is RECOMMENDED that clients initiate a refresh at about 85% of the
preferred lifetime. Because RAs may periodically 'reset' the
preferred- lifetime, the refresh timer MUST be independently
maintained from the address valid-lifetime. Clients SHOULD set a
refresh timer to 85% of the preferred lifetime when they complete a
registration operation and only update this timer if 85% of any
updated preferred lifetime would be sooner than the timer.
{TODO: is the preferred lifetime a good idea? The default value is 7
days which seems rather long. Indeed we might say that it's an
administrator's job to configure non-default lifetime... Also, what
about statically assigned addresses or PIOs with the inifinite
lifetime??}
5.3. Acknowledging Registration and Retransmission
After an address registration server accepts an address registration
request, it MUST send a Reply message as the response to the client.
The acceptance reply only means that the server has taken
responsibility to remember and log the client, not that it has yet
done so.
The server generates a Reply message and includes a Status Code
option with value Success, a Server Identifier option with the
server's DUID, and a Client Identifier option with the client's DUID.
If there is no reply received within some interval, the client SHOULD
retransmit the message according to section 14 of [RFC3315], using
the following parameters:
* IRT ADDR_REG_TIMEOUT
* MRT ADDR_REG_MAX_RT
* MRC ADDR_REG_MAX_RC
* MRD 0
The below presents a table of values used to describe the message
transmission behavior of clients and servers:
Parameter Default Description
---------------------------------------------------------------------
ADDR_REG_TIMEOUT 1 secs Initial Addr Registration Request timeout
ADDR_REG_MAX_RT 60 secs Max Addr Registration Request timeout value
ADDR_REG_MAX_RC 5 Max Request retry attempts
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For each IA Address option in the ADDR-REG-NOTIFICATION message for
which the server does not accept its associated registration request,
the server adds an IA Address option with the associated IPv6
address, and includes a Status Code option with the value
RegistrationDenied (TBA2) in the IA Address option. No other options
are included in the IA Address option.
Upon receiving a RegistrationDenied error status code, the client MAY
also resend the message following normal retransmission routines
defined in [RFC3315] with above parameters. The client MUST wait out
the retransmission time before retrying.
6. 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 [RFC3315].
One of the primary use-cases for the mechanism described in this
document is to identify which device is infected with malware (or is
otherwise doing bad things) so that it can be blocked from accessing
the network. As the device itself is responsible for informing the
DHCPv6 server that it is using an address, malware (or a malicious
client) can simply not send the ADDR-REG-NOTIFICATION message. This
is an informational, optional mechanism, and is designed to aid in
debugging. It is not intended to be a strong security access
mechanism.
7. IANA Considerations
This document defines a new DHCPv6 message, the ADDR-REG-NOTIFICATION
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/
7.1. Value Description Reference
TBA1 ADDR-REG-NOTIFICATION this document
This document defines a new DHCPv6 Status code, the
RegistrationDenied (TBA2) described in Section 5, that requires an
allocation out of the registry of Status Codes defined at
http://www.iana.org/assignments/dhcpv6-parameters/
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7.2. Code Name Reference
TBA2 RegistrationDenied this document
8. References
8.1. 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,
<https://www.rfc-editor.org/rfc/rfc2119>.
[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, <https://www.rfc-editor.org/rfc/rfc3315>.
[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>.
8.2. Informative References
[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>.
Acknowledgments
"We've Been Trying To Reach You About Your Car's Extended Warranty"
Much thanks to Jen Linkova for additional text on client behavior.
Also, much thanks to Erik Kline and Lorenzo Colitti for significant
discussion and feedback.
Contributors
Gang Chen
China Mobile
53A, Xibianmennei Ave.
Xuanwu District
Beijing
P.R. China
Email: phdgang@gmail.com
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Authors' Addresses
Warren Kumari
Google, LLC
Email: warren@kumari.net
Suresh Krishnan
Kaloom
Email: suresh@kaloom.com
Sheng Jiang
Beijing
P.R. China
Email: jiangsheng@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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