draft-krishnan-mip6-firewall-01.txt		draft-krishnan-mip6-firewall-00.txt
	Network Working Group S. Krishnan		Network Working Group S. Krishnan
	Internet-Draft Ericsson		Internet-Draft Ericsson
	Intended status: Informational N. Steinleitner		Intended status: Standards Track June 28, 2007
	Expires: January 7, 2008 University of Goettingen		Expires: December 30, 2007
	Y. Qiu
	Institute for Infocomm Research
	July 6, 2007
	Firewall Recommendations for MIPv6		Firewall Recommendations for MIPv6
	draft-krishnan-mip6-firewall-01		draft-krishnan-mip6-firewall-00
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	Abstract		Abstract
	This document presents some recommendations for firewall
	administrators to help them configure their firewalls in a way that
	allows Mobile IPv6 signaling and data messags to pass through. This
	document assumes that the firewalls in question include some kind of
	stateful packet filtering capability.
	Table of Contents		Table of Contents
	1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3		1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
	2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 5		3. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 5
	3.1. Signaling between the MN and the HA . . . . . . . . . . . 5		3.1. Signaling between the MN and the HA . . . . . . . . . . . 5
	3.2. Route optimization signaling between MN and CN through		3.2. Route optimization signaling between MN and CN through
	HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5		HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	3.3. IKEv2 signaling between MN and HA for establishing SAs . . 6		3.3. IKEv2 signaling between MN and HA for establishing SAs . . 6
	3.4. Data traffic from and to MN passing through the HA . . . . 6		3.4. Data traffic from and to MN passing through the HA . . . . 6
	4. Correspondent Node behind a firewall . . . . . . . . . . . . . 7		4. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 7
	4.1. Route optimization signaling between MN and CN through		5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7		6. Normative References . . . . . . . . . . . . . . . . . . . . . 9
	4.2. Route optimization signaling between MN and CN . . . . . . 7		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
	4.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 8		Intellectual Property and Copyright Statements . . . . . . . . . . 11
	4.4. Route Optimization data traffic from MN . . . . . . . . . 8
	4.5. Bi-directional tunnelled data traffic from the MN to
	the CN through HA . . . . . . . . . . . . . . . . . . . . 8
	5. Mobile Node behind a firewall . . . . . . . . . . . . . . . . 10
	5.1. Signaling between MN and HA . . . . . . . . . . . . . . . 10
	5.2. Signaling between MN and CN . . . . . . . . . . . . . . . 10
	5.3. IKEv2 signaling between MN and HA for establishing SAs . . 11
	5.4. Data traffic from and to the MN . . . . . . . . . . . . . 11
	6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
	9. Normative References . . . . . . . . . . . . . . . . . . . . . 15
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
	Intellectual Property and Copyright Statements . . . . . . . . . . 17
	1. Requirements notation		1. Requirements notation
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Introduction		2. Introduction
	Network elements such as firewalls are an integral aspect of a		Network elements such as firewalls are an integral aspect of a
	majority of IP networks today, given the state of security in the		majority of IP networks today, given the state of security in the
	Internet, threats, and vulnerabilities to data networks. MIPv6		Internet, threats, and vulnerabilities to data networks. MIPv6
	[RFC3775] defines mobility support for IPv6 nodes. Since firewalls		[RFC3775] defines mobility support for IPv6 nodes. Since firewalls
	are not aware of MIPv6 protocol details, they will probably interfere		are not aware of MIPv6 protocol details, they will probably interfere
	with the smooth operation of the protocol. The problems caused by		with the smooth operation of the protocol. The problems caused by
	firewalls to Mobile IPv6 are documented in [RFC4487].		firewalls to Mobile IPv6 are documented in [RFC4487]
	This document presents some recommendations for firewall		This document presents some recommendations for firewall
	administrators to help them configure their firewalls in a way that		administrators to help them configure their firewalls in a way that
	allows Mobile IPv6 signaling and data messags to pass through. This		allows Mobile IPv6 signaling and data messags to pass through. This
	document assumes that the firewalls in question include some kind of		document assumes that the firewalls in question include some kind of
	stateful packet filtering capability.		stateful packet filtering capability.
	3. Home Agent behind a firewall		3. Home Agent behind a firewall
	This section presents the recommendations for configuring a firewall		This section presents the recommendations for configuring a firewall
	skipping to change at page 5, line 25		skipping to change at page 5, line 25
	o Route optimization signaling between MN and CN through HA		o Route optimization signaling between MN and CN through HA
	o IKEv2 signaling between MN and HA for establishing SAs		o IKEv2 signaling between MN and HA for establishing SAs
	o Data traffic from and to MN passing through the HA		o Data traffic from and to MN passing through the HA
	3.1. Signaling between the MN and the HA		3.1. Signaling between the MN and the HA
	The signaling between the MN and HA is protected using IPSec ESP.		The signaling between the MN and HA is protected using IPSec ESP.
	These messages are encrypted and hence are not inspectable by		These messages are encrypted and hence are not inspectable by
	firewalls. So the firewall has to either permit all these messages		firewalls. So the firewall either has to either permit all these
	or discard all of them. But if these messages are discarded, Mobile		messages or discard all of them. But if these messages are
	IPv6 as specified today will cease to work. In order to permit these		discarded, Mobile IPv6 as specified today will cease to work. In
	messages through, the firewall has to detect the messages using the		order to permit these messages through, the firewall has to detect
	following pattern.		the messages using the following pattern.
	Destination Address: Address of HA		Destination Address: Address of HA
	IP payload protocol number: 50 (ESP)		IP payload protocol number: 50 (ESP)
	This pattern will allow the BU messages from MNs to HA and BA		This pattern will allow the BU messages from MNs to HA and BA
	messages from the HA to the MNs to pass through. It will also allow		messages from the HA to the MNs to pass through. It will also allow
	the HoTI and HoT messages (related to route optimization) between the		the HoTI and HoT messages (related to route optimization) between the
	MN and the HA to pass through.		MN and the HA to pass through.
	3.2. Route optimization signaling between MN and CN through HA		3.2. Route optimization signaling between MN and CN through HA
	skipping to change at page 6, line 4		skipping to change at page 6, line 4
	order for route optimization to work, part of the initial signaling		order for route optimization to work, part of the initial signaling
	has to pass through the HA. The following pattern will allow these		has to pass through the HA. The following pattern will allow these
	messages to pass through.		messages to pass through.
	Destination Address: HoA of MN		Destination Address: HoA of MN
	Mobility Header Type: 3		Mobility Header Type: 3
	This pattern allows the HoT message from the CN to the MN's HoA to		This pattern allows the HoT message from the CN to the MN's HoA to
	pass through the firewall. The HoTI message from the MN to the CN		pass through the firewall. The HoTI message from the MN to the CN
	through the HA usually passes through the firewall without any		through the HA usually passes through the firewall without any
	problems. Hence no specific pattern is recommended. If the firewall		problems. Hence no specific pattern is recommended.
	does not have the capability to recognize the mobility header type,
	it needs to at least filter on the IP payload protocol type 135
	(Mobility Header) in order to limit the scope of this filter rule.
	3.3. IKEv2 signaling between MN and HA for establishing SAs		3.3. IKEv2 signaling between MN and HA for establishing SAs
	The MN and HA exchange IKEv2 signaling in order to establish the		The MN and HA exchange IKEv2 signaling in order to establish the
	security associations. The security associations so established will		security associations. The security associations so established will
	later be used for securing the mobility signaling messages. Hence		later be used for securing the mobility signaling messages. Hence
	these messages need to be permitted to pass through the firewalls.		these messages need to be permitted to pass through the firewalls.
	The following pattern will detect these messages.		The following pattern will detect these messages.
	Destination Address: Address of HA		Destination Address: Address of HA
	skipping to change at page 6, line 32		skipping to change at page 6, line 29
	If a CN tries to initiate traffic to an MN, a stateful firewall would		If a CN tries to initiate traffic to an MN, a stateful firewall would
	prevent these connection requests to pass through as there is no		prevent these connection requests to pass through as there is no
	established state on the firewall. Since MNs do not usually provide		established state on the firewall. Since MNs do not usually provide
	services, this is not usually a problem. But if this is necessary to		services, this is not usually a problem. But if this is necessary to
	do, the pattern to look for is		do, the pattern to look for is
	Destination Address: MN HoA		Destination Address: MN HoA
	Allowing this traffic might allow any kind of traffic, including		Allowing this traffic might allow any kind of traffic, including
	malicious traffic, to pass through unfiltered to the MN. This would		malicious traffic, to pass through unfiltered to the MN. This might
	expose the MN to any type of possibly malicious traffic, resulting in		cause a Denial of Service at the MN.
	a denial of service or exploitation of known security
	vulnerabilities. This practice is NOT RECOMMENDED.
	4. Correspondent Node behind a firewall
	This section presents the recommendations for configuring a firewall
	if a node behind it should be able to act as Mobile IPv6 CN. For
	each type of traffic that needs to pass through this firewall,
	recommendations are presented on how to identify that traffic. The
	following types of traffic are considered
	o Route optimization signaling between MN and CN through HA
	o Route optimization signaling between MN and CN
	o Binding Update from MN to CN
	o Route Optimization data traffic from MN
	o Bi-directional tunnelled data traffic from the MN to the CN
	through HA
	4.1. Route optimization signaling between MN and CN through HA
	Parts of the initial route optimization signaling has to pass through
	the HA, namely the HoTI and the HoT messages. Without assistance,
	the HoTI message from the HA to the CN is not able to traverse the
	firewall. The following pattern will allow these messages to
	traverse.
	Destination Address: CN Address
	Mobility Header Type: 1
	This pinhole allows the HoTI message from the HA to the CN to
	traverse the firewall. The HoT message from the CN to the MN through
	the HA can traverse the firewall without any assistance. Hence no
	pinhole is required.
	4.2. Route optimization signaling between MN and CN
	Route Optimization allows direct communication of data packets
	between the MN and a CN without tunnelling it back through the HA.
	To get route optimization work, the MN has to send a CoTI message
	directly to the CN, which response with a CoT message. However, a
	stateful firewall would prevent the CoTI message to pass through as
	there is no established state on the firewall. The following pinhole
	will allow the CoTI message to traverse.
	Destination Address: CN Address
	Mobility Header Type: 2
	The CoT message from the CN to the MN can traverse the firewall
	without any assistance. Hence no pinhole is required.
	4.3. Binding Update from MN to CN
	After successfully performing the return routability procedure, the
	MN sends the BU to the CN and expects the BA. Since this BU does not
	match any previous installed pinhole rules, an additional pinhole
	with the following format is required.
	Destination Address: CN Address
	Mobility Header Type: 5
	This allows the BU to traverse the firewall and the BA can pass the
	firewall without any assistance. Therefore, the Binding Update
	sequence can be performed successfully.
	4.4. Route Optimization data traffic from MN
	Also the Route Optimization data traffic from MN directly to the CN
	can not traverse the firewall without assistance. But as we have
	configured the firewall to allow the BU message from MN to the CN to
	traverse the firewall, the Route Optimization data traffic is able to
	pass through as it also matches the pinhole installed for the BU.
	Therefore, no additional pinhole rules are required.
	4.5. Bi-directional tunnelled data traffic from the MN to the CN
	through HA
	If a MN tries to initiate traffic to a CN through the HA using bi-
	directional tunnelling, a stateful firewall would prevent these
	connection requests to pass through as there is no established state
	on the firewall. This is usually a problem as CNs often provide
	services. A solution is to static configure the firewall to let this
	traffic pass through. However, this is only an acceptable option if
	it is not necessary to open an all-embracing pinhole, e.g. if the
	destination ports are well-known. In this case, the pinhole has to
	look like
	Destination Address: CN Address
	Destination Port: Application Ports
	If the ports are unknown, it is necessary to install a pinhole with
	only the Destination Address as pattern. Allowing this traffic might
	allow any kind of traffic, including malicious traffic, to traverse
	to the CN. Allowing this traffic might allow any kind of traffic,
	including malicious traffic, to pass through unfiltered to the CN.
	This would expose the CN to any type of possibly malicious traffic,
	resulting in a denial of service or exploitation of known security
	vulnerabilities. This practice is NOT RECOMMENDED
	5. Mobile Node behind a firewall
	This section presents the recommendations for configuring a firewall
	that protects the network a mobile node visiting. For each type of
	traffic that needs to pass through this firewall, recommendations are
	presented on how to identify that traffic. The following types of
	traffic are considered
	o Signaling between MN and HA
	o Route Optimization Signaling between MN and CN
	o IKEv2 signaling between MN and HA for establishing SAs
	o Data traffic from and to MN
	5.1. Signaling between MN and HA
	As described in Section 3.1, the signaling between the MN and HA is
	protected using IPSec ESP. Currently, a lot of firewalls are
	configured to block the incoming ESP packets. Moreover, from the
	view of the firewall, both source and destination addresses of these
	messages from/to mobile node are variable. Fortunately, for a
	stateful firewall, if the initial traffic is allowed through the
	firewall, then the return traffic is also allowed. A mobile node is
	always the initiator for the BU. Since MN's CoA is not able to be
	known in advance, the firewall can use following pattern to permit
	these messages through.
	Source Address: Visited subnet prefix
	IP payload protocol number: 50 (ESP)
	This pattern will allow the initial packets (e.g. BU from MNs to HA,
	HoTI, etc.) to pass through the firewall. Then the return packets
	(BA from HA to MN, HoT) is also able to pass through accordingly.
	5.2. Signaling between MN and CN
	Route Optimization allows direct communication of data packets
	between the MN and a CN without tunneling it back through the HA. It
	includes 3 pairs of messages: HoTI/HoT, CoTI/CoT and BU/BA. The
	first pair can pass through the firewall using the pattern described
	in section 5.1. Here we discuss CoTI/CoT and BU/BA messages.
	Following pattern permits these messages through the firewall.
	Source Address: Visited subnet prefix
	IP payload protocol number: 135 (Mobility Header)
	This pattern allows the initial messages (CoTI and BU) from the MN to
	the CN pass through the firewall. The return messages (CoT and BA)
	from the CN to the MN can also passes through the firewall
	accordingly.
	5.3. IKEv2 signaling between MN and HA for establishing SAs
	The MN and HA exchange IKEv2 signaling in order to establish the
	security associations. The security associations so established will
	later be used for securing the mobility signaling messages. Due to
	variable source/destination IP addresses and MN always as initiator,
	the following pattern will let the negotiation pass.
	Source Address: Visited subnet prefix
	Transport Protocol: UDP
	Destination UDP Port: 500
	5.4. Data traffic from and to the MN
	After sending the home binding update, every traffic packet between
	MN and HA will be encapsulated by ESP. As described in section 5.1,
	the firewall allows theses packets pass through. However, if a CN
	tries to initiate traffic to an MN, a stateful firewall would prevent
	these connection requests to pass through as there is no established
	state on the firewall. We may use following steps to establish a
	channel state between MN and CN:
	1. When detecting BU message from MN to CN with protocol number 135
	and mobility header type 5, the firewall extracts the home
	address from the destination option.
	2. Firewall adds a security rule to its table with following
	pattern.
	Destination Address: CoA
	Source Address: CN
	Routing Header Type 2 Address: HoA
	Thereafter any packets to MN will be filtered by above pattern.
	6. Contributors		4. Contributors
	This document is one of the deliverables of the MIPv6 firewall		This document is one of the deliverables of the MIPv6 firewall
	design. The following members of the team were involved in the		design. The following members of the team were involved in the
	creation of this document.		creation of this document.
	Hannes Tschofenig Hannes.Tschofenig@gmx.net		Hannes Tschofenig Hannes.Tschofenig@gmx.net
	Gabor Bajko Gabor.Bajko@nokia.com		Gabor Bajko Gabor.Bajko@nokia.com
	Suresh Krishnan suresh.krishnan@ericsson.com		Suresh Krishnan suresh.krishnan@ericsson.com
	skipping to change at page 13, line 5		skipping to change at page 8, line 5
	Yaron Sheffer yaronf@checkpoint.com		Yaron Sheffer yaronf@checkpoint.com
	Qiu Ying qiuying@i2r.a-star.edu.sg		Qiu Ying qiuying@i2r.a-star.edu.sg
	Ram Vishnu vishnu@motorola.com		Ram Vishnu vishnu@motorola.com
	Niklas Steinleitner steinleitner@cs.uni-goettingen.de		Niklas Steinleitner steinleitner@cs.uni-goettingen.de
	Vijay Devarapalli vijay.devarapalli@AzaireNet.com		Vijay Devarapalli vijay.devarapalli@AzaireNet.com
	7. IANA Considerations		5. Security Considerations
	This document does not require any IANA action.
	8. Security Considerations
	This document specifies recommendations for firewall administrators		This document specifies recommendations for firewall administrators
	to allow Mobile IPv6 traffic to pass through unhindered. Since some		to allow Mobile IPv6 traffic to pass through unhindered. Since some
	of this traffic is encrypted it is not possible for firewalls to		of this traffic is encrypted it is not possible for firewalls to
	discern whether it is safe or not. This document recommends a		discern whether it is safe or not. This document recommends a
	liberal setting so that all legitimate traffic can pass. This means		liberal setting so that all legitimate traffic can pass. This means
	that some malicious traffic may be permitted by these rules. These		that some malicious traffic may be permitted by these rules. These
	rules may allow the initiation of Denial of Service attacks against		rules may allow the initiation of Denial of Service attacks against
	Mobile IPv6 capable nodes (the MNs, CNs and the HAs). Especially the		Mobile IPv6 capable nodes such as a home agent.
	rules specified in Section 3.4 and Section 4.5 are broadly defined
	and hence possess the most potential for abuse. Hence, if these
	rules are implemented, the firewalls SHOULD be configured to rate-
	limit such traffic on a per-destination basis. This would allow the
	firewall to mitigate possible denial of service attacks on the
	endpoints. Please note that such measures would not mitigate other
	potential security issues.
	9. Normative References		6. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support		[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
	in IPv6", RFC 3775, June 2004.		in IPv6", RFC 3775, June 2004.
	[RFC4487] Le, F., Faccin, S., Patil, B., and H. Tschofenig, "Mobile		[RFC4487] Le, F., Faccin, S., Patil, B., and H. Tschofenig, "Mobile
	IPv6 and Firewalls: Problem Statement", RFC 4487,		IPv6 and Firewalls: Problem Statement", RFC 4487,
	May 2006.		May 2006.
	Authors' Addresses		Author's Address
	Suresh Krishnan		Suresh Krishnan
	Ericsson		Ericsson
	8400 Decarie Blvd.		8400 Decarie Blvd.
	Town of Mount Royal, QC		Town of Mount Royal, QC
	Canada		Canada
	Phone: +1 514 345 7900 x42871		Phone: +1 514 345 7900 x42871
	Email: suresh.krishnan@ericsson.com		Email: suresh.krishnan@ericsson.com
	Niklas Steinleitner
	University of Goettingen
	Lotzestr. 16-18
	Goettingen
	Germany
	Email: steinleitner@cs.uni-goettingen.de
	Ying Qiu
	Institute for Infocomm Research
	21 Heng Mui Keng Terrace
	Singapore
	Phone: +65-6874-6742
	Email: qiuying@i2r.a-star.edu.sg
	Full Copyright Statement		Full Copyright Statement
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	This document is subject to the rights, licenses and restrictions		This document is subject to the rights, licenses and restrictions
	contained in BCP 78, and except as set forth therein, the authors		contained in BCP 78, and except as set forth therein, the authors
	retain all their rights.		retain all their rights.
	This document and the information contained herein are provided on an		This document and the information contained herein are provided on an
	"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS		"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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