One document matched: draft-krishnan-mip6-firewall-admin-02.txt
Differences from draft-krishnan-mip6-firewall-admin-01.txt
Network Working Group S. Krishnan
Internet-Draft Ericsson
Intended status: Informational N. Steinleitner
Expires: May 21, 2008 University of Goettingen
Y. Qiu
Institute for Infocomm Research
November 18, 2007
Guidelines for firewall administrators regarding MIPv6 traffic
draft-krishnan-mip6-firewall-admin-02
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document presents some recommendations for firewall
administrators to help them configure their existing firewalls in a
way that allows in certain deployment scenarios the Mobile IPv6
signaling and data messages to pass through. For other scenarios,
the support of additional mechanisms to create pinholes required for
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MIPv6 will be necessary. This document assumes that the firewalls in
question include some kind of stateful packet filtering capability.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 3
3.1. Signaling between the MN and the HA . . . . . . . . . . . 4
3.2. IKEv2 signaling between MN and HA for establishing SAs . . 4
3.3. Data traffic from and to MN passing through the HA . . . . 4
4. Correspondent Node behind a firewall . . . . . . . . . . . . . 5
4.1. Route optimization signaling between MN and CN through
HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Route optimization signaling between MN and CN . . . . . . 5
4.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 6
4.4. Route Optimization data traffic from MN . . . . . . . . . 6
4.5. Bi-directional tunnelled data traffic from the MN to
the CN through HA . . . . . . . . . . . . . . . . . . . . 6
5. Mobile Node behind a firewall . . . . . . . . . . . . . . . . 7
5.1. Signaling between MN and HA . . . . . . . . . . . . . . . 7
5.2. Signaling between MN and CN . . . . . . . . . . . . . . . 8
5.3. IKEv2 signaling between MN and HA for establishing SAs . . 8
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . . . 11
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1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction
Network elements such as firewalls are an integral aspect of a
majority of IP networks today, given the state of security in the
Internet, threats, and vulnerabilities to data networks. MIPv6
[RFC3775] defines mobility support for IPv6 nodes. Since firewalls
are not aware of MIPv6 protocol details, they will probably interfere
with the smooth operation of the protocol. The problems caused by
firewalls to Mobile IPv6 are documented in [RFC4487].
This document presents some recommendations for firewall
administrators to help them configure their firewalls in a way that
allows the Mobile IPv6 signaling and data messages to pass through.
This document assumes that the firewalls in question include some
kind of stateful packet filtering capability. The static rules that
need to be configured are described in this document. In some
scenarios, the support of additional mechanisms to create pinholes
required for MIPv6 signalling and data traffic to pass through will
be necessary. A possible solution, describing the dynamic
capabilities needed for the firewalls to create pinholes based on
MIPv6 signalling traffic is described in a companion document
[MIP6FWVENDOR]. Other solutions may also be possible.
3. Home Agent behind a firewall
This section presents the recommendations for configuring a firewall
that protects a home agent. 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 the MN and the HA
o IKEv2 signaling between MN and HA for establishing SAs
o Data traffic from and to MN passing through the HA
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3.1. Signaling between the MN and the HA
The signaling between the MN and HA is protected using IPSec ESP.
These messages are critical to the MIPv6 protocol and if these
messages are discarded, Mobile IPv6 as specified today will cease to
work. In order to permit these messages through, the firewall has to
detect the messages using the following patterns.
Destination Address: Address of HA
Next Header: 50 (ESP)
Mobility Header Type: 5 (BU)
Destination Address: Address of HA
Next Header: 50 (ESP)
Mobility Header Type: 1 (HoTI)
This pattern will allow the BU messages from MNs to HA to pass
through. It will also allow the HoTI messages (related to route
optimization) between the MN and the HA to pass through.
3.2. 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. Hence
these messages need to be permitted to pass through the firewalls.
The following pattern will detect these messages.
Destination Address: Address of HA
Transport Protocol: UDP
Destination UDP Port: 500
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
prevent these connection requests to pass through as there is no
established state on the firewall. If this is necessary to do, the
pattern to look for is
Destination Address: MN HoA
Allowing this traffic might allow any kind of traffic, including
malicious traffic, to pass through unfiltered to the MN. This would
expose the MN to any type of possibly malicious traffic, resulting in
a denial of service or exploitation of known security
vulnerabilities. This practice is NOT RECOMMENDED. Instead, a
dynamically created pinhole like the one specified in [MIP6FWVENDOR]
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can be used to allow this traffic.
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.
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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. A dynamically
created pinhole such as the one specified in [MIP6FWVENDOR] will
allow this traffic to pass.
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
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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
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 patterns to permit
these messages through.
Source Address: Visited subnet prefix
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,
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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
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
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
6. Contributors
This document is one of the deliverables of the MIPv6 firewall
design. The following members of the team were involved in the
creation of this document.
Hannes Tschofenig Hannes.Tschofenig@gmx.net
Gabor Bajko Gabor.Bajko@nokia.com
Suresh Krishnan suresh.krishnan@ericsson.com
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Hesham Soliman solimanhs@gmail.com
Yaron Sheffer yaronf@checkpoint.com
Qiu Ying qiuying@i2r.a-star.edu.sg
Niklas Steinleitner steinleitner@cs.uni-goettingen.de
Vijay Devarapalli vijay.devarapalli@AzaireNet.com
7. IANA Considerations
This document does not require any IANA action.
8. Security Considerations
This document specifies recommendations for firewall administrators
to allow Mobile IPv6 traffic to pass through unhindered. Since some
of this traffic is encrypted it is not possible for firewalls to
discern whether it is safe or not. This document recommends a
liberal setting so that all legitimate traffic can pass. This means
that some malicious traffic may be permitted by these rules. These
rules may allow the initiation of Denial of Service attacks against
Mobile IPv6 capable nodes (the MNs, CNs and the HAs). Especially the
rules specified in Section 3.3 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
[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
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
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[RFC4487] Le, F., Faccin, S., Patil, B., and H. Tschofenig, "Mobile
IPv6 and Firewalls: Problem Statement", RFC 4487,
May 2006.
Authors' Addresses
Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
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
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