draft-ietf-dhc-dhcpv6-unknown-msg-04.txt   draft-ietf-dhc-dhcpv6-unknown-msg-05.txt 
DHC Working Group Y. Cui DHC Working Group Y. Cui
Internet-Draft Q. Sun Internet-Draft Q. Sun
Updates: 3315 (if approved) Tsinghua University Updates: 3315 (if approved) Tsinghua University
Intended status: Standards Track T. Lemon Intended status: Standards Track T. Lemon
Expires: June 19, 2014 Nominum, Inc. Expires: August 8, 2014 Nominum, Inc.
December 16, 2013 February 4, 2014
Handling Unknown DHCPv6 Messages Handling Unknown DHCPv6 Messages
draft-ietf-dhc-dhcpv6-unknown-msg-04 draft-ietf-dhc-dhcpv6-unknown-msg-05
Abstract Abstract
DHCPv6 is not specific about handling messages with unknown types. DHCPv6 is not specific about handling messages with unknown types.
This memo describes the problems and defines how a DHCPv6 server, This memo describes the problems and defines how a DHCPv6 server,
client or relay agent should behave when receiving unknown DHCPv6 client or relay agent should behave when receiving unknown DHCPv6
messages. This document updates RFC3315. messages. This document also provides advice for authors of future
documents defining new messages sent from DHCP servers to DHCP relay
agents, and should be read by potential authors of such documents.
This document updates RFC3315.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 19, 2014. This Internet-Draft will expire on August 8, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 2 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. Relay Agent Behavior Update . . . . . . . . . . . . . . . . . 3 4. Relay Agent Behavior Update . . . . . . . . . . . . . . . . . 3
4.1. A Valid Message for Constructing a New Relay-forward 4.1. A Valid Message for Constructing a New Relay-forward
Message . . . . . . . . . . . . . . . . . . . . . . . . . 3 Message . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Relaying a Message toward Server . . . . . . . . . . . . 4 4.2. Relaying a Message toward Server . . . . . . . . . . . . 5
4.3. Relaying a Message toward Client . . . . . . . . . . . . 4 4.3. Relaying a Message toward Client . . . . . . . . . . . . 5
5. Client and Server Behavior Update . . . . . . . . . . . . . . 4 5. Client and Server Behavior Update . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Contributors List . . . . . . . . . . . . . . . . . . . . . . 5 8. Contributors List . . . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . 5 9. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
DHCPv6 [RFC3315] provides a framework for conveying IPv6 DHCPv6 [RFC3315] provides a framework for conveying IPv6
configuration information to hosts on a TCP/IP network. But configuration information to hosts on a TCP/IP network. But
[RFC3315] is not specific about how to deal with messages with [RFC3315] is not specific about how to deal with messages with
unrecognized types. This document describes the problems and defines unrecognized types. This document describes the problems and defines
the behavior of a DHCPv6 server, client or relay agent when handling the behavior of a DHCPv6 server, client or relay agent when handling
unknown DHCPv6 messages. unknown DHCPv6 messages.
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Relay-Forward messages. In this document, we specify the definition Relay-Forward messages. In this document, we specify the definition
as follows. as follows.
The message is valid for constructing a new Relay-forward message: The message is valid for constructing a new Relay-forward message:
(a) if the message is a Relay-forward message, or (a) if the message is a Relay-forward message, or
(b) if the relay agent receives the message for which it is not the (b) if the relay agent receives the message for which it is not the
target according to the message type. target according to the message type.
In the case that a new type of message is sent by the server to a New DHCP message types may be defined in future that are intended to
relay agent but the relay agent does not recognize it, the message is convey information from DHCP servers to relay agents. Relay agents
put into a Relay-forward message and sent to the server. that do not implement these messages will not recognize that such
messages are intended for them. A relay agent that implements this
specification will necessarily forward such messages to the DHCP
servers to which it is configured to relay client messages.
At this time, no messages of this variety have been specified. If
such a message is specified in the future, the specification could
include text something like the following:
DHCP servers that send this new message type MAY, when they receive
a relayed message of this type, mark the relay agent to which the
message was sent as not implementing messages of this type. In
this case, the DHCP server MAY implement a strategy of probing the
relay agent occasionally to see if it has been updated.
However, this is not strictly necessary, since DHCP does not provide
a signaling message for rejecting unexpected message types, and
therefore DHCP servers are not expected to respond to such messages.
Documents specifying new message types should use different types for
communicating *to* relay agents than are used for communicating
*from* relay agents, so that no confusion can occur where a message
sent to a relay agent is sent back to the DHCP server, which then
tries to process it as if it came from a relay agent.
4.2. Relaying a Message toward Server 4.2. Relaying a Message toward Server
If the relay agent receives a Relay-forward message, Section 20.1.2 If the relay agent receives a Relay-forward message, Section 20.1.2
of [RFC3315] defines the required behavior. If the relay agent of [RFC3315] defines the required behavior. If the relay agent
receives messages other than Relay-forward and Relay-reply and the receives messages other than Relay-forward and Relay-reply and the
relay agent does not recognize its message type, it MUST forward them relay agent does not recognize its message type, it MUST forward them
as is described in Section 20.1.1 of [RFC3315]. as is described in Section 20.1.1 of [RFC3315].
4.3. Relaying a Message toward Client 4.3. Relaying a Message toward Client
If the relay agent receives a Relay-reply message, it MUST process If the relay agent receives a Relay-reply message, it MUST process
the message as is defined in Section 20.2 of [RFC3315], regardless of the message as is defined in Section 20.2 of [RFC3315], regardless of
the type of the message encapsulated in the Relay Message Option. the type of the message encapsulated in the Relay Message Option.
5. Client and Server Behavior Update 5. Client and Server Behavior Update
There are chances that the client or server would receive DHCPv6 A client or server MUST silently discard any received DHCPv6 message
messages with unknown types. In this case, the client or server MUST with an unknown message type.
silently discard the unrecognized messages.
6. Security Considerations 6. Security Considerations
As the relay agent will forward all unknown types of DHCPv6 messages, As the relay agent will forward all unknown types of DHCPv6 messages,
a malicious attacker can interfere with the relaying function by a malicious attacker can interfere with the relaying function by
constructing fake DHCPv6 messages with arbitrary type code. The same constructing fake DHCPv6 messages with arbitrary type code. The same
problem may happen in current DHCPv4 and DHCPv6 practice where the problem may happen in current DHCPv4 and DHCPv6 practice where the
attacker constructs the fake DHCP message with a known type code. attacker constructs the fake DHCP message with a known type code.
Clients and servers that implement this specification will discard Clients and servers that implement this specification will discard
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