Network Working Group S. Krishnan Internet-Draft Ericsson Intended status: Standards Track Y. Sheffer Expires:
April 11,November 19, 2009 Check Point N. Steinleitner University of Goettingen G. Bajko Nokia October 8, 2008May 18, 2009 Guidelines for firewall vendors regarding MIPv6 traffic draft-ietf-mext-firewall-vendor-00draft-ietf-mext-firewall-vendor-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 11,November 19, 2009. Abstract This document presents some recommendations for firewall vendors to help them implement their firewalls in a way that allows Mobile IPv6 signaling and data messages to pass through. This document describes how to implement stateful packet filtering capability for MIPv6. Table of Contents 1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. MIPv6 Firewall Primitives . . . . . . . . . . . . . . . . . . . 3 3.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Detecting and parsing the Mobility Header . . . . . . . . . 3 3.3. Parsing Mobility Options . . . . . . . . . . . . . . . . . 4 4. Allowing signaling response packets . . . . . . . . . . . . . . 4 5. Allowing data packets based on signaling . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 9. Normative References . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 9 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 vendors to help them implement their firewalls in a way that allows Mobile IPv6 signaling and data messags to pass through. This document describes how to implement stateful packet filtering capability for MIPv6. 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. MIPv6 Firewall Primitives 3.1. Requirements This document assumes that the firewalls are capable of deep packet inspection at least until the mobility header. It also assumes that the firewalls are capable of creating filters based on arbitrary fields based on the contents of a signaling packet. 3.2. Detecting and parsing the Mobility Header The Mobility Header is the basic primitive in all MIPv6 signaling messages. Thus the firewalls need to be able to recognize the presence of the mobility header and be able to parse the contents of the Mobility Header. The MH is described in section 6.1 of [RFC3775] and the format of the same is scribed in section 6.1.1 of [RFC3775]. Firewalls need to be able to at least understand the contents of the MH Type field that describes the type of signaling message carried. 3.3. Parsing Mobility Options The Mobility Header can carry additional information in the form of mobility options as described in section 6.2 of [RFC3775]. Some of these mobility options need to be understood for proper creation of state on the firewalls. Hence firewalls must be able to parse the mobility options defined in [RFC3775]. 4. Allowing signaling response packets The MIPv6 signalling messages are usually performed as a request- response pair. The request message is usually allowed by setting up a static firewall rule to allow the traffic to pass through. The response message on the other hand can be dynamically allowed if the firewall can automatically setup a filter for the response packets when the request packet passes through. This is not trivial, but fortunately is straightforward. There are 3 message pairs that are of importance to MIPv6 signaling. They are the BU/BA, HoTI/HoT and CoTI/CoT pairs. When the first message in the pair traverses the firewall in one direction, the firewall must setup a filter rule to allow the second message through in the other direction. Consider a packet that matches a static rule configured on a firewall Destination Address: Address of HA Next Header: 50 (ESP) Mobility Header Type: 5 (BU) This rule allows a binding update message from a MN to pass through to the HA. Once a packet that matches this rule passes through the firewall, the firewall must setup a dynamic filter for the return packet Source Address: Destination Address from Packet Destination Address: Source Address from Packet Next Header: 50 (ESP) Mobility Header Type: 6 (BA) This rule ensures that the return BA packet will pass through unhindered. The rules can be generalized as summarized in the table below. +---------------------------------+---------------------------------+ | Passing packet MH Type | Setup return filter with MH | | | Type | +---------------------------------+---------------------------------+ | Mobility Header Type:1(HoTI) | Mobility Header Type:3(HoT) | | Mobility Header Type:2(CoTI) | Mobility Header Type:4(CoT) | | Mobility Header Type:5(BU) | Mobility Header Type:6(BA) | +---------------------------------+---------------------------------+ Table 1: Message Pairs in MIPv6 Such dynamic rules can be timed out after a configurable period STATEFUL_PINHOLE_LIFETIME, unless renewed by new mobility messages. This document recommends that the default value of STATEFUL_PINHOLE_LIFETIME be set to 30 seconds. These dynamic rules MUST be immediately deleted after the return message passes through. e.g. Once a return HoT message for a HoTI passes through, the pinhole must be immediately removed. The loss of the HoT packet after passing the firewall needs to be handled by the original MN retransmitting the HoTI message. 5. Allowing data packets based on signaling Once the MIPv6 signaling completes, the data traffic can begin to flow. The traffic filters for the data traffic can be inferred from the contents of the signaling messages that setup the session. This section describes how firewalls can intelligently setup filters for data traffic based on signaling traffic.The following example describes how to setup a filter for allowing incoming route optimized messages from a CN to an MN after the MN sent a BU message to a CN. When the BU message from MN to CN (MH Type 5) traverses through the firewall the firewall extracts the home address (HoA) from the Home Address Option (section 6.3 of [RFC3775]) of the packet. The firewall adds the following rule in order to let the return traffic pass. Destination Address: Source Address of the packet (MN CoA) Source Address: Destination Address of packet (CN) Routing Header Type 2 Address: HoA This pattern allows all route optimized traffic coming from the CN to the MN to pass through. Additionally, the firewall adds a second rule in order to let the data traffic from the MN to the CN pass through. Source Address: Source Address of the packet (MN CoA) Destination Address: Destination Address of packet (CN) Next Header: IPv6 Destination Options Header(60) Home Address Dest. Option: MN HoA This pattern allows all route optimized traffic coming from the MN to the CN to pass through. A firewall protecting the HA can add the following rule on reception of a HA binding update, in order to let the incoming bi-directional tunneled traffic pass. Destination Address: Source Address of the packet (MN HoA) Source Address: Destination Address of packet (CN) 6. 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, Qiu Ying, 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. 7. IANA Considerations This document does not require any IANA action. 8. Security Considerations This document specifies recommendations for firewall vendors to allow Mobile IPv6 traffic to pass through unhindered. This document recommends a liberal setting of firewall rules so that all legitimate traffic may be allowed to 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). One of the main goals of any firewall is to prevent unsolicited traffic from entering the network. The proposed solution allows such traffic into the network, albeit with a number of restrictions. In a typical enterprise environment, an administrator cannot distinguish Mobile IPv6 capable nodes from other nodes. In such a situation any node in the protected network may end up receiving unsolicited packets from outside the firewall. The risk in this case is that such packets could trigger unknown vulnerabilities in any of these nodes, causing denial-of-service or worse attacks. This issue is compounded in a mobile service provider environment by the risks specific to such environments like endpoint battery exhaustion and spectrum misuse. 9. 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. Authors' Addresses Suresh Krishnan Ericsson 8400 Decarie Blvd. Town of Mount Royal, QC Canada Phone: +1 514 345 7900 x42871 Email: email@example.com Yaron Sheffer Check Point 5 Hasolelim St. Tel Aviv 67897 Israel Email: firstname.lastname@example.org Niklas Steinleitner University of Goettingen Lotzestr. 16-18 Goettingen Germany Email: email@example.com Gabor Bajko Nokia Email: firstname.lastname@example.org Full Copyright Statement Copyright (C) The IETF Trust (2008).(2009). 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. 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