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 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on October 20, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. 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 Vives & Palet Expires October 20, 2004 [Page 1] Internet-Draft IPv6 Security Problem Statement April 2004 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 Vives & Palet Expires October 20, 2004 [Page 2] Internet-Draft IPv6 Security Problem Statement April 2004 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 Vives & Palet Expires October 20, 2004 [Page 3] Internet-Draft IPv6 Security Problem Statement April 2004 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. Vives & Palet Expires October 20, 2004 [Page 4] Internet-Draft IPv6 Security Problem Statement April 2004 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 Vives & Palet Expires October 20, 2004 [Page 5] Internet-Draft IPv6 Security Problem Statement April 2004 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). Vives & Palet Expires October 20, 2004 [Page 6] Internet-Draft IPv6 Security Problem Statement April 2004 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 Vives & Palet Expires October 20, 2004 [Page 7] Internet-Draft IPv6 Security Problem Statement April 2004 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. Vives & Palet Expires October 20, 2004 [Page 8] Internet-Draft IPv6 Security Problem Statement April 2004 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, Vives & Palet Expires October 20, 2004 [Page 9] Internet-Draft IPv6 Security Problem Statement April 2004 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. Vives & Palet Expires October 20, 2004 [Page 10] Internet-Draft IPv6 Security Problem Statement April 2004 7. References 7.1 Normative References 7.2 Informative References [1] "IETF midcom WG", . [2] Bellovin, S., "Distributed Firewalls", November 1999, . [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 Vives & Palet Expires October 20, 2004 [Page 11] Internet-Draft IPv6 Security Problem Statement April 2004 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 Vives & Palet Expires October 20, 2004 [Page 12] Internet-Draft IPv6 Security Problem Statement April 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Vives & Palet Expires October 20, 2004 [Page 13]