Network Working Group S. Krishnan Internet-Draft Ericsson Intended status: Informational N. Steinleitner Expires: April 30, 2010 University of Goettingen Y. Qiu Institute for Infocomm Research G. Bajko Nokia October 27, 2009 Guidelines for firewall administrators regarding MIPv6 traffic draft-ietf-mext-firewall-admin-02 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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 April 30, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Krishnan, et al. Expires April 30, 2010 [Page 1] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 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 and DSMIPv6 signaling and data messages to pass through. For other scenarios, the support of additional mechanisms to create pinholes required for 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. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 4 4.1. Signaling between the MN and the HA . . . . . . . . . . . 5 4.2. IKEv2 signaling between MN and HA for establishing SAs . . 5 5. Correspondent Node behind a firewall . . . . . . . . . . . . . 6 5.1. Route optimization signaling between MN and CN through HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. Route optimization signaling between MN and CN . . . . . . 7 5.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 7 5.4. Route Optimization data traffic from MN . . . . . . . . . 7 6. Mobile Node behind a firewall . . . . . . . . . . . . . . . . 8 6.1. Signaling between MN and HA . . . . . . . . . . . . . . . 8 6.2. Data packets between DSMIPv6 . . . . . . . . . . . . . . . 9 6.3. Signaling between MN and CN . . . . . . . . . . . . . . . 9 6.4. IKEv2 signaling between MN and HA for establishing SAs . . 10 7. Related documents . . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 11.1. Normative References . . . . . . . . . . . . . . . . . . . 11 11.2. Informative References . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Krishnan, et al. Expires April 30, 2010 [Page 2] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 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. Firewalls will interfere with the smooth operation of the MIPv6 protocol unless specific steps are taken to allow Mobile IPv6 signaling and data messages to pass through the firewall. 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. Some Mobile IPv6 signalling messages require the use of encryption to protect the confidentiality of the payload (e.g. the HoTI and HoT messages between the MN and the HA). The other signalling messages allow the use of encryption. If encryption is being used, it is not possible to inspect the contents of the signalling packets. For these messages to get through, a generic rule needs to be added in the firewall to let ESP packets through without further inspection. 3. Abbreviations This document uses the following abbreviations: o CN: Correspondent Node o CoA: Care of Address Krishnan, et al. Expires April 30, 2010 [Page 3] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 o CoTI: Care of Test Init o HA: Home Agent o HoA: Home Address o HoTI: Home Test Init o HoT: Home Test o MN: Mobile Node o RO: Route Optimization o RRT: Return Routability Test 4. Home Agent behind a firewall This section presents the recommendations for configuring a firewall that protects a home agent. +----------------+ +---+ | | | A | | | +---+ | +----+ | External | | HA | +----+ MN | +----+ | FW | +---+ | Home Agent +----+ | B | | of A | +---+ | | External | | Node +----------------+ Network protected by a firewall Figure 1: HA behind a firewall 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 Krishnan, et al. Expires April 30, 2010 [Page 4] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 4.1. 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) This pattern will allow the BU messages from MNs to HA to pass through. When an HA supporting DSMIPv6 clients is behind firewall, in order for DSMIPv6 signalling to reach the HA, the firewall has to allow signaling packets sent to HA's UDP port 4191 to pass through: Destination Address: IPv4 address of HA Protocol: 17 (UDP) Port: 4191 The firewall may also have a rule allowing IP-in-IP encapsulated traffic to pass through to the HA: Destination Address: IPv4 address of HA Protocol: 4 (IP-in-IP) If the above rule is not created by the firewall, IP encapsulated DSMIPv6 signalling will not reach the HA. A client compliant with , when it does not get a response to the BU, is supposed to resend the BU encapsulated into UDP, with destination port 4191. Thus, even if the above rule is not created the signaling may pass through with the (IPv4 HA, UDP 4191) rule. 4.2. 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 Krishnan, et al. Expires April 30, 2010 [Page 5] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 5. 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. +----------------+ +----+ | | | HA | | | +----+ | | Home Agent | +---+ +----+ of B | |CN | | FW | | | C | +----+ | +---+ | +---+ | | | B | | | +---+ +----------------+ External Mobile Network protected Node by a firewall Figure 2: CN behind a firewall 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 5.1. 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. When only a few priviledged nodes (like servers) are allowed to be contacted by outside nodes, then the following pattern will allow the HoTI messages to reach these nodes: Destination Address: CN Address Mobility Header Type: 1 (HoTI) where CN Address describes the address(es) of the priviledged node(s). This pinhole allows the HoTI message from the HA to the CN Krishnan, et al. Expires April 30, 2010 [Page 6] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 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. 5.2. 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. When only a few priviledged nodes (like servers) are allowed to be contacted by outside nodes, then the following pattern will allow the CoTI messages to reach these nodes: Destination Address: CN Address Mobility Header Type: 2 (CoTI) where CN Address describes the address(es) of the priviledged node(s).The CoT message from the CN to the MN can traverse the firewall without any assistance. Hence no pinhole is required. 5.3. 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.When only a few priviledged nodes (like servers) are allowed to be contacted by outside nodes, then the following pattern will allow the BU messages to reach these nodes: Destination Address: CN Address Mobility Header Type: 5 where CN Address describes the address(es) of the priviledged node(s).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. 5.4. 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 Krishnan, et al. Expires April 30, 2010 [Page 7] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 allow this traffic to pass. 6. Mobile Node behind a firewall This section presents the recommendations for configuring a firewall that protects the network a mobile node visiting. +----------------+ +----+ | | | HA | | | +----+ | | Home Agent | +---+ +----+ of A +---+ | | A | | FW | | B | | +---+ +----+ +---+ |Internal | External | MN | Node | | +----------------+ Network protected by a firewall Figure 3: MN behind a firewall 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 6.1. Signaling between MN and HA As described in Section 4.1, 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 Krishnan, et al. Expires April 30, 2010 [Page 8] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 Destination Address: Address of HA Next Header: 50 (ESP) Mobility Header Type: 5 (BU) This pattern will allow the Binding Update packets to pass through the firewall. Then the return packets (BA from HA to MN) will also able to pass through accordingly. 6.2. Data packets between DSMIPv6 In case of a DSMIPv6 client with only a v4 CoA, the dynamic rules set by the firewall to allow DSMIPv6 signalling packets pass through between the MN and the HA, may time out and be closed. If that happens, data packets sent by a CN to the MN through the HA will not reach the MN. Therefore, the firewall will need to set a static rule to allow data packets sent from the HA's IPv4 address to the MN's IPv4 CoA using either protocol number 4 (IP-in-IP encapsulation) or 17 (UDP), depending on the value of the F bit, to pass through. The UDP port numbers for the rule are to be read from the BU/BA message exchange [RFC5555]. When the firewall chooses to create static rules (without traffic based timeout) for allowing DSMIPv6 signalling pass between the MN and HA, then no further rules need to be created by the firewall, as data packets follow the same tunnel as the signaling. 6.3. 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. Krishnan, et al. Expires April 30, 2010 [Page 9] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 6.4. 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 7. Related documents There are other IETF published documents that provide recommendations for firewall configuration that can affect Mobile IPv6 messages. [RFC4890] that provides recommendations for filtering ICMPv6 messages (especially Section 4.3.2). [RFC4942] describes security issues present in IPv6 and related protocols (especially Sections 2.1.2 and 2.1.15). 8. Acknowledgements The authors would like to thank the following members of the MIPv6 firewall design team for contributing to this document: Hannes Tschofenig, Hesham Soliman, Yaron Sheffer, and Vijay Devarapalli. The authors would also like to thank William Ivancic, Ryuji Wakikawa, Jari Arkko, Henrik Levkowetz, Pasi Eronen and Noriaki Takamiya for their thorough reviews of the document and for providing comments to improve the quality of the document. 9. IANA Considerations This document does not require any IANA action. 10. 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 Krishnan, et al. Expires April 30, 2010 [Page 10] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 rules may allow the initiation of Denial of Service attacks against Mobile IPv6 capable nodes (the MNs, CNs and the HAs). 11. References 11.1. Normative References [MIP6FWVENDOR] Krishnan, S., Sheffer, Y., Steinleitner, N., and G. Bajko, "Guidelines for firewall vendors regarding MIPv6 traffic", draft-ietf-mext-firewall-vendor-0 (work in progress), October 2008. [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. [RFC5555] Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and Routers", RFC 5555, June 2009. 11.2. Informative References [RFC4890] Davies, E. and J. Mohacsi, "Recommendations for Filtering ICMPv6 Messages in Firewalls", RFC 4890, May 2007. [RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/ Co-existence Security Considerations", RFC 4942, September 2007. 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 Krishnan, et al. Expires April 30, 2010 [Page 11] Internet-Draft MIPv6 Firewall Administrator guidelines October 2009 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 Gabor Bajko Nokia Email: gabor.bajko@nokia.com Krishnan, et al. Expires April 30, 2010 [Page 12]