draft-krishnan-mip6-firewall-admin-00.txt   draft-krishnan-mip6-firewall-admin-01.txt 
Network Working Group S. Krishnan Network Working Group S. Krishnan
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Informational N. Steinleitner Intended status: Informational N. Steinleitner
Expires: May 13, 2008 University of Goettingen Expires: May 19, 2008 University of Goettingen
Y. Qiu Y. Qiu
Institute for Infocomm Research Institute for Infocomm Research
November 10, 2007 November 16, 2007
Guidelines for firewall administrators regarding MIPv6 traffic Guidelines for firewall administrators regarding MIPv6 traffic
draft-krishnan-mip6-firewall-admin-00 draft-krishnan-mip6-firewall-admin-01
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 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 messages 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.
Table of Contents Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 5 3. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 3
3.1. Signaling between the MN and the HA . . . . . . . . . . . 5 3.1. Signaling between the MN and the HA . . . . . . . . . . . 3
3.2. Route optimization signaling between MN and CN through 3.2. IKEv2 signaling between MN and HA for establishing SAs . . 4
HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.3. Data traffic from and to MN passing through the HA . . . . 4
3.3. IKEv2 signaling between MN and HA for establishing SAs . . 6 4. Correspondent Node behind a firewall . . . . . . . . . . . . . 4
3.4. Data traffic from and to MN passing through the HA . . . . 6
4. Correspondent Node behind a firewall . . . . . . . . . . . . . 7
4.1. Route optimization signaling between MN and CN through 4.1. Route optimization signaling between MN and CN through
HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Route optimization signaling between MN and CN . . . . . . 7 4.2. Route optimization signaling between MN and CN . . . . . . 5
4.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 8 4.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 6
4.4. Route Optimization data traffic from MN . . . . . . . . . 8 4.4. Route Optimization data traffic from MN . . . . . . . . . 6
4.5. Bi-directional tunnelled data traffic from the MN to 4.5. Bi-directional tunnelled data traffic from the MN to
the CN through HA . . . . . . . . . . . . . . . . . . . . 8 the CN through HA . . . . . . . . . . . . . . . . . . . . 6
5. Mobile Node behind a firewall . . . . . . . . . . . . . . . . 10 5. Mobile Node behind a firewall . . . . . . . . . . . . . . . . 7
5.1. Signaling between MN and HA . . . . . . . . . . . . . . . 10 5.1. Signaling between MN and HA . . . . . . . . . . . . . . . 7
5.2. Signaling between MN and CN . . . . . . . . . . . . . . . 10 5.2. Signaling between MN and CN . . . . . . . . . . . . . . . 7
5.3. IKEv2 signaling between MN and HA for establishing SAs . . 11 5.3. IKEv2 signaling between MN and HA for establishing SAs . . 8
5.4. Data traffic from and to the MN . . . . . . . . . . . . . 11 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 9. Normative References . . . . . . . . . . . . . . . . . . . . . 9
9. Normative References . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . . . . 11
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
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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. The static rules that need to
be configured are described in this document. The dynamic
capabilities needed for the firewalls to implement stateful filtering
of MIPv6 packers is described in a companion document [MIP6FWVENDOR].
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
that is protects a home agent. For each type of traffic that needs that protects a home agent. For each type of traffic that needs to
to pass through this firewall, recommendations are presented on how pass through this firewall, recommendations are presented on how to
to identify that traffic. The following types of traffic are identify that traffic. The following types of traffic are considered
considered
o Signaling between the MN and the HA o Signaling between the MN and the 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 critical to the MIPv6 protocol and if these
firewalls. So the firewall has to either permit all these messages messages are discarded, Mobile IPv6 as specified today will cease to
or discard all of them. But if these messages are discarded, Mobile work. In order to permit these messages through, the firewall has to
IPv6 as specified today will cease to work. In order to permit these detect the messages using the following patterns.
messages through, the firewall has to detect the messages using the
following pattern.
Destination Address: Address of HA Destination Address: Address of HA
IP payload protocol number: 50 (ESP) Next Header: 50 (ESP)
Mobility Header Type: 5 (BU)
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
the HoTI and HoT messages (related to route optimization) between the
MN and the HA to pass through.
3.2. Route optimization signaling between MN and CN through HA
Route Optimization allows direct communication of data packets
between the MN and a CN without tunneling it back through the HA. In
order for route optimization to work, part of the initial signaling
has to pass through the HA. The following pattern will allow these
messages to pass through.
Destination Address: HoA of MN Destination Address: Address of HA
Mobility Header Type: 3 Next Header: 50 (ESP)
Mobility Header Type: 1 (HoTI)
This pattern allows the HoT message from the CN to the MN's HoA to This pattern will allow the BU messages from MNs to HA to pass
pass through the firewall. The HoTI message from the MN to the CN through. It will also allow the HoTI messages (related to route
through the HA usually passes through the firewall without any optimization) between the MN and the HA to pass through.
problems. Hence no specific pattern is recommended. If the firewall
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 3.2. 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
Transport Protocol: UDP Transport Protocol: UDP
Destination UDP Port: 500 Destination UDP Port: 500
3.4. Data traffic from and to MN passing through the HA 3.3. Data traffic from and to MN passing through the HA
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
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Mobility Header Type: 5 Mobility Header Type: 5
This allows the BU to traverse the firewall and the BA can pass the This allows the BU to traverse the firewall and the BA can pass the
firewall without any assistance. Therefore, the Binding Update firewall without any assistance. Therefore, the Binding Update
sequence can be performed successfully. sequence can be performed successfully.
4.4. Route Optimization data traffic from MN 4.4. Route Optimization data traffic from MN
Also the Route Optimization data traffic from MN directly to the CN Also the Route Optimization data traffic from MN directly to the CN
can not traverse the firewall without assistance. But as we have can not traverse the firewall without assistance. The stateful
configured the firewall to allow the BU message from MN to the CN to firewall rules specified in [MIP6FWVENDOR] will open a pinhole for
traverse the firewall, the Route Optimization data traffic is able to this traffic.
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 4.5. Bi-directional tunnelled data traffic from the MN to the CN
through HA through HA
If a MN tries to initiate traffic to a CN through the HA using bi- If a MN tries to initiate traffic to a CN through the HA using bi-
directional tunnelling, a stateful firewall would prevent these directional tunnelling, a stateful firewall would prevent these
connection requests to pass through as there is no established state connection requests to pass through as there is no established state
on the firewall. This is usually a problem as CNs often provide on the firewall. This is usually a problem as CNs often provide
services. A solution is to static configure the firewall to let this services. A solution is to static configure the firewall to let this
traffic pass through. However, this is only an acceptable option if traffic pass through. However, this is only an acceptable option if
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Destination Port: Application Ports Destination Port: Application Ports
If the ports are unknown, it is necessary to install a pinhole with If the ports are unknown, it is necessary to install a pinhole with
only the Destination Address as pattern. Allowing this traffic might only the Destination Address as pattern. Allowing this traffic might
allow any kind of traffic, including malicious traffic, to traverse allow any kind of traffic, including malicious traffic, to traverse
to the CN. Allowing this traffic might allow any kind of traffic, to the CN. Allowing this traffic might allow any kind of traffic,
including malicious traffic, to pass through unfiltered to the CN. including malicious traffic, to pass through unfiltered to the CN.
This would expose the CN to any type of possibly malicious traffic, This would expose the CN to any type of possibly malicious traffic,
resulting in a denial of service or exploitation of known security resulting in a denial of service or exploitation of known security
vulnerabilities. This practice is NOT RECOMMENDED vulnerabilities. This practice is NOT RECOMMENDED.
5. Mobile Node behind a firewall 5. Mobile Node behind a firewall
This section presents the recommendations for configuring a firewall This section presents the recommendations for configuring a firewall
that protects the network a mobile node visiting. For each type of that protects the network a mobile node visiting. For each type of
traffic that needs to pass through this firewall, recommendations are traffic that needs to pass through this firewall, recommendations are
presented on how to identify that traffic. The following types of presented on how to identify that traffic. The following types of
traffic are considered traffic are considered
o Signaling between MN and HA o Signaling between MN and HA
o Route Optimization Signaling between MN and CN o Route Optimization Signaling between MN and CN
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
5.1. Signaling between MN and HA 5.1. Signaling between MN and HA
As described in Section 3.1, the signaling between the MN and HA is As described in Section 3.1, the signaling between the MN and HA is
protected using IPSec ESP. Currently, a lot of firewalls are protected using IPSec ESP. Currently, a lot of firewalls are
configured to block the incoming ESP packets. Moreover, from the configured to block the incoming ESP packets. Moreover, from the
view of the firewall, both source and destination addresses of these view of the firewall, both source and destination addresses of these
messages from/to mobile node are variable. Fortunately, for a messages from/to mobile node are variable. Fortunately, for a
stateful firewall, if the initial traffic is allowed through the stateful firewall, if the initial traffic is allowed through the
firewall, then the return traffic is also allowed. A mobile node is 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 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 known in advance, the firewall can use following patterns to permit
these messages through. these messages through.
Source Address: Visited subnet prefix Source Address: Visited subnet prefix
IP payload protocol number: 50 (ESP)
Destination Address: Address of HA
Next Header: 50 (ESP)
Mobility Header Type: 1 (HoTI)
Source Address: Visited subnet prefix
Destination Address: Address of HA
Next Header: 50 (ESP)
Mobility Header Type: 5 (BU)
This pattern will allow the initial packets (e.g. BU from MNs to HA, 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 HoTI, etc.) to pass through the firewall. Then the return packets
(BA from HA to MN, HoT) is also able to pass through accordingly. (BA from HA to MN, HoT) is also able to pass through accordingly.
5.2. Signaling between MN and CN 5.2. Signaling between MN and CN
Route Optimization allows direct communication of data packets Route Optimization allows direct communication of data packets
between the MN and a CN without tunneling it back through the HA. It 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 includes 3 pairs of messages: HoTI/HoT, CoTI/CoT and BU/BA. The
first pair can pass through the firewall using the pattern described first pair can pass through the firewall using the pattern described
in section 5.1. Here we discuss CoTI/CoT and BU/BA messages. in section 5.1. Here we discuss CoTI/CoT and BU/BA messages.
Following pattern permits these messages through the firewall. Following pattern permits these messages through the firewall.
Source Address: Visited subnet prefix Source Address: Visited subnet prefix
IP payload protocol number: 135 (Mobility Header) Mobility Header Type: 2 (CoTI)
Source Address: Visited subnet prefix
Mobility Header Type: 5 (BU)
This pattern allows the initial messages (CoTI and BU) from the MN to 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) the CN pass through the firewall. The return messages (CoT and BA)
from the CN to the MN can also passes through the firewall from the CN to the MN can also passes through the firewall
accordingly. accordingly.
5.3. IKEv2 signaling between MN and HA for establishing SAs 5.3. 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. Due to later be used for securing the mobility signaling messages. Due to
variable source/destination IP addresses and MN always as initiator, variable source/destination IP addresses and MN always as initiator,
the following pattern will let the negotiation pass. the following pattern will let the negotiation pass.
Source Address: Visited subnet prefix Source Address: Visited subnet prefix
Transport Protocol: UDP Transport Protocol: UDP
Destination UDP Port: 500 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 6. 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
Hesham Soliman solimanhs@gmail.com Hesham Soliman solimanhs@gmail.com
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
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 7. IANA Considerations
This document does not require any IANA action. This document does not require any IANA action.
8. Security Considerations 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
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8. Security Considerations 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 (the MNs, CNs and the HAs). Especially the
rules specified in Section 3.4 and Section 4.5 are broadly defined rules specified in Section 3.3 and Section 4.5 are broadly defined
and hence possess the most potential for abuse. Hence, if these and hence possess the most potential for abuse. Hence, if these
rules are implemented, the firewalls SHOULD be configured to rate- rules are implemented, the firewalls SHOULD be configured to rate-
limit such traffic on a per-destination basis. This would allow the limit such traffic on a per-destination basis. This would allow the
firewall to mitigate possible denial of service attacks on the firewall to mitigate possible denial of service attacks on the
endpoints. Please note that such measures would not mitigate other endpoints. Please note that such measures would not mitigate other
potential security issues. potential security issues.
9. Normative References 9. Normative References
[MIP6FWVENDOR]
Krishnan, S., "Guidelines for firewall vendors regarding
MIPv6 traffic", draft-krishnan-mip6-firewall-vendor-01
(work in progress), November 2007.
[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.
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