[Mip6-firewall] HA Firewall BCP draft v01
Suresh Krishnan
suresh.krishnan at ericsson.com
Thu Jul 5 18:34:47 EDT 2007
Hi Folks,
Here is v01 of the draft. Since I have not heard back from Qiu Ying
regarding my comments, I have not included the MN part yet. I will try
to wait until Sunday to submit this in case there are any comments.
Cheers
Suresh
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Network Working Group S. Krishnan
Internet-Draft Ericsson
Intended status: Informational N. Steinleitner
Expires: December 30, 2007 University of Goettingen
Q. Ying
Institute for Infocomm Research
June 28, 2007
Firewall Recommendations for MIPv6
draft-krishnan-mip6-firewall-01
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Copyright Notice
Copyright (C) The IETF Trust (2007).
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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
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 5
3.1. Signaling between the MN and the HA . . . . . . . . . . . 5
3.2. Route optimization signaling between MN and CN through
HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
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
4. Correspondent Node behind a firewall . . . . . . . . . . . . . 7
4.1. RRT signaling between MN and CN through HA . . . . . . . . 7
4.2. Route optimization signaling between MN and CN . . . . . . 7
4.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 8
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. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Normative References . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 15
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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].
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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 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.
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3. Home Agent behind a firewall
This section presents the recommendations for configuring a firewall
that is 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 Route optimization signaling between MN and CN through HA
o IKEv2 signaling between MN and HA for establishing SAs
o Data traffic from and to MN passing through the HA
3.1. Signaling between the MN and the HA
The signaling between the MN and HA is protected using IPSec ESP.
These messages are encrypted and hence are not inspectable by
firewalls. So the firewall either has to either permit all these
messages or discard all of them. But 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 pattern.
Destination Address: Address of HA
IP payload protocol number: 50 (ESP)
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
Mobility Header Type: 3
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
through the HA usually passes through the firewall without any
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problems. Hence no specific pattern is recommended.
3.3. 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. 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
3.4. 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. Since MNs do not usually provide
services, this is not usually a problem. But 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 might
cause a Denial of Service at the MN.
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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 RRT 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. RRT signaling between MN and CN through HA
Parts of the initial RRT 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 RRT, 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
IPv6 Destination Options Header
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
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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. This might cause a Denial of Service at the CN.
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5. 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 at gmx.net
Gabor Bajko Gabor.Bajko at nokia.com
Suresh Krishnan suresh.krishnan at ericsson.com
Hesham Soliman solimanhs at gmail.com
Yaron Sheffer yaronf at checkpoint.com
Qiu Ying qiuying at i2r.a-star.edu.sg
Ram Vishnu vishnu at motorola.com
Niklas Steinleitner steinleitner at cs.uni-goettingen.de
Vijay Devarapalli vijay.devarapalli at AzaireNet.com
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6. IANA Considerations
This document does not require any IANA action.
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7. 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 such as a home agent.
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8. Normative References
[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.
[RFC4487] Le, F., Faccin, S., Patil, B., and H. Tschofenig, "Mobile
IPv6 and Firewalls: Problem Statement", RFC 4487,
May 2006.
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Authors' Addresses
Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan at ericsson.com
Niklas Steinleitner
University of Goettingen
Lotzestr. 16-18
Goettingen
Germany
Email: steinleitner at cs.uni-goettingen.de
Qiu Ying
Institute for Infocomm Research
21 Heng Mui Keng Terrace
Singapore
Phone: +65-6874-6742
Email: qiuying at i2r.a-star.edu.sg
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