One document matched: draft-vives-v6ops-ipv6-security-ps-00.txt
Internet Engineering Task Force A. Vives
Internet-Draft J. Palet
Expires: October 20, 2004 Consulintel
April 21, 2004
IPv6 Security Problem Statement
draft-vives-v6ops-ipv6-security-ps-00.txt
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Abstract
Today, each network is often secured by a unique device (i.e.
security gateway or firewall), that becomes a bottleneck for the
end-to-end security model with IPv6. The deployment of IPv6 enabled
devices and networks bring some issues, which must be addressed by
security administrators in order to guarantee at least the same level
of security obtained nowadays with IPv4 and perimeter security
schemes, allowing at the same time all the IPv6 advantages.
The most important issues are the rediscovery of end-to-end
communications, the availability of IPsec in all IPv6 stacks, the
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increase in the number and type of IP devices and also the increase
in the number of "nomadic" devices, meaning devices that will be
connected to different networks (that could have different security
policies).
The security policies and architectures currently applied in Internet
with IPv4, does not longer apply for end-to-end security models which
IPv6 will need. This document outlines the advantages and drawbacks
of both security schemes: perimeter and distributed.
This document aims to identify IPv6 issues that justify the need of a
distributed security model for IPv6, that is, simply to show that a
security problem will arise with the deployment of IPv6 networks if
nothing is done.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Perimeter versus Host-based Security . . . . . . . . . . . . . 4
2.1 Perimeter Security . . . . . . . . . . . . . . . . . . . . 4
2.2 Host-based Security . . . . . . . . . . . . . . . . . . . 5
3. IPv6 Issues . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 End-to-End . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 IPsec-encrypted ESP-traffic in transport mode . . . . . . 8
3.3 Mobility . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.4 Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
3.5 Neighbor Discovery Weakness . . . . . . . . . . . . . . . 9
4. Other Issues . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1 Normative References . . . . . . . . . . . . . . . . . . . . 11
7.2 Informative References . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . 13
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1. Introduction
This document will cope only with IPv6 issues related to security,
i.e., will try to answer the following question: How would affect the
security of a network the deployment of IPv6? This network would be
an existent IPv4 one which will have also IPv6 traffic from IPv6
capable nodes, or an IPv6 only network.
As the deployment of IPv6 enabled devices and networks come, some
points must be taken in account by the security administrator:
o The rediscovery of end-to-end communications.
o The availability of IPsec in all IPv6 stacks.
o The increase in the number and type of IP devices.
o The increase in the number of "nomadic" devices, meaning devices
that will be connected to different networks and moving.
The security policies and architectures currently applied in Internet
with IPv4, does not longer apply for end-to-end security models which
IPv6 will enable. This document will outline the advantages and
drawbacks of both security schemes: perimeter and distributed.
Also IPv6 issues will be identified that justify the need of
distributed security for IPv6, that is, simply to show that a
security problem will arise with the deployment of IPv6 networks if
traditional schemes are used.
The following issues are out of scope of this document and will be
addressed elsewhere:
o State the security requirements for the addressed IPv6 scenario.
o Propose a solution or architecture to address the problem stated
in this document.
o To address security problems derived from the use of transition
mechanisms.
Last but not least, this document contains a brief definition of what
we understand by "security". We use security in the "big sense" of
the word, trying to include as much as possible. In other words, a
host, a network or some information, will be secure when no threats
could succeed against them, by mean of different kinds of attacks. A
success will mean compromise of availability, integrity,
confidentiality or authenticity. The realistic objective is to be as
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much secure as possible in a precise moment. It will be part of the
requirements to establish which kind of security is given using a
number of mechanisms.
2. Perimeter versus Host-based Security
In this section two different approaches are analyzed to be used
later in the rationale about the security problems that IPv6 could
introduce
2.1 Perimeter Security
The perimeter scheme is the most common one and is based in the
topology of the network, i.e., host's security will depend on where
it is connected to. The security policy is enforced in a central host
or firewall (FW), which provides secure network connectivity to one
or more network segments. The FW will be what an "outside" host sees
when tries to attack the network. Attacks coming from the same LAN
segment are not protected by the FW.
/-------\
/ \
| Internet |
\ /
\---+---/
|
| Policy Enforcement Point
+---+---+
LAN-1 | | DMZ-1
----+---------+ FW +-------+----
| | | |
+----+ +---+---+ +----+
| H1 | | | S1 |
+----+ |LAN-2 +----+
|
+----+ |
| H2 |--+
+----+ |
Figure 1: Perimeter Security
This model is based on the following assumptions:
o The threats come from "outside" the FW, basically the Internet.
o Everybody from "inside" the FW is trustable.
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o The protected nodes won't go "outside" where FW won't be able to
protect them.
o There are no backdoors on the network (modem, WLAN, other
connections).
o The hosts will not need to be accessed directly from outside (at
least in a general manner, i.e., all ports on all hosts).
The main advantage of this scheme is its simplicity and easiness as
the elements and points of configuration are reduced to the minimum,
requiring few/none protocols and mechanisms to implement the
security.
The drawbacks of this model are:
o This is a centralized model: Single point of failure for both
performance and availability. If the FW fails, then all the
networks connected to it loose network connectivity.
o A big percentage of the threats come from inside the FW, and are
not addressed by this security model.
o The most dangerous threats come from inside the FW.
o The FW usually acts as NAT and/or proxy box, interfering or even
disallowing end-to-end communications.
o Transport mode secured communications (using IPsec ESP for
example) need special solutions ([1]).
o The same security policy is enforced for all the nodes of each
network connected to the FW. Consequently an error in the FW will
equally expose all hosts in a network.
o Virtual organizations, for example those using GRID models, don't
work with traditional centralized security models.
o The lack of secure end-to-end prevents innovation.
2.2 Host-based Security
Host based security model, already introduced by [2], is based on the
idea of enforcing the security policy in each network host from a
central control point.
The three main elements identified in the distributed security model
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are:
o Policy Specification Language.
o Policy Exchange Protocol.
o Authentication of Entities.
The basic idea is simple, the Security Policy is centrally defined
using the Policy Specification Language and distributed to each host
by means of the Policy Exchange Protocol. The Network Entities need
to be authenticated in order to be trusted, for example to allow an
incoming connection or to trust on the received Security Policy.
/-------\
/ \
| Internet |
+------+ \ /
|Sec. | \---+---/
|Policy| |
+------+ |
| /---\ LAN-3
| | \ / |-------+--
-+---+------+ x + |
LAN-1 | (*) | / \ | | (*)Policy Enforcement Point
+----+ \---/ +----+
| H1 | | LAN-2 | H3 |
+----+ | +----+
| (*)
+----+
| H2 |
+----+
Figure 2: Host-based Security
This model is based on the following assumptions:
o Each host can be unique and securely identified.
o The security policy could be applied in one or more of the
following levels: network, transport and application.
o The threat comes from anywhere in the network.
o The intruder has no physical access to the protected network hosts
(what about malicious users? See other topics section).
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o "Outside" hosts can access all hosts "Inside".
The advantages of this model are:
o The security policy can be host-defined.
o A host can take better decisions as it knows what it is doing or
trying to do, that means it can better detect strange packets. For
example, can allow mail traffic to only one application on the
system.
o Enables the usage of end-to-end applications level security (i.e.
web services security standards).
o Can protect a host not depending on the topology, i.e., wherever
the host is connected.
o Do not need specific devices to secure a host (consider the case
of single host with a CPE).
o Can control the outgoing attempts from each host, avoiding local
network misbehavior or malicious practices.
o The collection of audit information could be more complete in a
distributed model, despite the processing of that information is
done distributed or centralized.
o It maintains the centralized control of the security policies,
from where they are distributed to each host (central decisions,
local enforcement).
The drawbacks of this model are:
o It is more complex than the perimeter one.
o The uniqueness and secured identification of hosts is not trivial,
for example using certificates ([2]).
3. IPv6 Issues
When IPv6 is deployed, either in an existing IPv4 network or in a new
IPv6-only network, the security administrator must take into account
that IPv6 traffic will be different from the IPv4 one.
IPv6 enabled nodes will have global addresses, which means they are
reachable from any other IPv6 node in the Internet. A security
administrator can avoid this but, if so, it makes no sense to use
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IPv6.
3.1 End-to-End
As stated in [3], section 6, there is a problem with end-to-end
communications, which means that every host must be reachable from
any other host, included the ones from "outside". This is a problem
in the perimeter security model.
This kind of communications provides the required framework for
further innovation, where technologies like P2P or GRID can widely
spread with no problems.
In [4] some possible solutions are outlined, one of them being a host
firewall.
3.2 IPsec-encrypted ESP-traffic in transport mode
As stated in [3], section 5, there is a problem with the IPv6
encrypted traffic (IPsec ESP mechanism in transport mode, for
example) and the perimeter security model.
The idea is that a host inside the network can establish an encrypted
communication channel with other host outside of the network, for
example. A middlebox (for example the perimeter firewall) won't be
able to inspect the content of such a communication.
In [4] some possible solutions are outlined, one of them being a host
firewall.
3.3 Mobility
In parallel to the increase in the number of devices, IPv6
facilitates that those devices are "mobile", that is, can easily move
from one network to another using Mobile IPv6 or just disconnecting
from one and connecting to another (sometimes called micro- and macro
mobility respectively).
Because of the amount of addresses available and the facilities given
by Autoconfiguration mechanisms together with the mentioned rise of
the number of IP devices, this kind of behavior should be taken into
account by the security administrator, as these devices will be
connected to networks where they have no control and consequently, no
responsibility.
A possible solution for these devices is the use of host based
security, enabled in every network it is connected. The policies and
mechanisms should be described elsewhere.
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3.4 Addresses
Regarding the addresses in IPv6 must be taken into account that:
o The amount of addresses is much bigger for a given network.
o Each host will have more than one address, one ore more of them
globally routable.
o An IPv6 node can use randomly generated addresses [5].
That means:
o To scan a given network whole range of addresses and ports will
take a really big effort [6]. It would be easier to do that
sniffing a LAN segment looking for existent addresses.
o The common way of identify a host by means of its IP address will
be more difficult to use.
o If a host uses randomly generated addresses [5], it could be
problematic to identify a host using its IP address for security
policy matching purposes.
Regarding the scan of addresses, [6] demonstrates that the "brute
force" scanning would make no sense for an IPv6 address range,
typically a minimum of /64.
So an attacker would change the scanning method reducing the range as
much as possible and when a host is found, the attacker should try to
compromise this one, as then the scanning could continue from the
compromised host, from where the success would be greater. If the
found host could not be compromised, then the first "brute force"
scanning could continue until the next host is found.
A host based security scheme would protect the other hosts from the
compromised one.
The idea behind all this is that the new IPv6 address scheme and
mechanisms will somehow protect from existent attack techniques but
we can be sure that they will adapt themselves to the new scheme and
we have to act consequently being prepared.
3.5 Neighbor Discovery Weakness
As said above, one of the assumptions of the host-based security
model is that all hosts in the network are non trusted, the possible
threats coming from the same LAN segment must be taken into account,
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in this case the ones coming from Neighbour Discovery (ND) [7][8].
Note that this is not possible within the perimeter security model,
although some detection mechanism could be implemented, nothing can
be done to protect the hosts.
As described in [4] there are some threats over ND.
There are some ways to interfere in the normal behavior of the
autoconfiguration process, causing redirection of traffic and/or DoS
(Denial of Service).
Special attention must be put on Router Advertisement (RA), Router
Solicitation (RS), Neighbour Solicitation (NS), Neighbour
Advertisement (NA) and Redirect messages. See [4] for a detailed
explanation of possible threats.
The possibility of using host firewalls and/or IDS (Intrusion
Detection Systems) for protecting hosts against these threats must be
studied.
It seems straightforward that if the hosts sending packets must be
authenticated against the rule-set configured in the host firewall
[2], that protects the host against most of the threats described in
[4].
4. Other Issues
Further elaboration is required (TBD) on:
o Malicious users: We can't protect the network from malicious users
that have physical access to network hosts in the protected
network. The objective is to minimize the danger they can cause.
o In the host based security, the host that stores and distributes
the security policies seems to be the best option to be the one
that acts as IDS.
5. Security Considerations
This document is concerned entirely with security.
6. Acknowledgements
The authors would like to acknowledge the inputs of Brian Carpenter
and the European Commission support in the co-funding of the Euro6IX
project, where this work is being developed.
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7. References
7.1 Normative References
7.2 Informative References
[1] "IETF midcom WG", <http://www.ietf.org/html.charters/
midcom-charter.html>.
[2] Bellovin, S., "Distributed Firewalls", November 1999, <http://
www.research.att.com/~smb/papers/distfw.pdf>.
[3] Savola, P., "Firewalling Considerations for IPv6",
draft-savola-v6ops-firewalling-02 (work in progress), October
2003.
[4] Nikander, P., "IPv6 Neighbor Discovery trust models and
threats", draft-ietf-send-psreq-04 (work in progress), October
2003.
[5] Narten, T. and R. Draves, "Privacy Extensions for Stateless
Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[6] Chown, T., "IPv6 Implications for TCP/UDP Port Scanning",
draft-chown-v6ops-port-scanning-implications-00 (work in
progress), October 2003.
[7] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for
IP Version 6 (IPv6)", RFC 2461, December 1998.
[8] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
Authors' Addresses
Alvaro Vives Martinez
Consulintel
San Jose Artesano, 1
Alcobendas - Madrid
E-28108 - Spain
Phone: +34 91 151 81 99
Fax: +34 91 151 81 98
EMail: alvaro.vives@consulintel.es
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Jordi Palet Martinez
Consulintel
San Jose Artesano, 1
Alcobendas - Madrid
E-28108 - Spain
Phone: +34 91 151 81 99
Fax: +34 91 151 81 98
EMail: jordi.palet@consulintel.es
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