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Checking references for intended status: Informational ---------------------------------------------------------------------------- -- No information found for draft-ietf-mext-firewall-vendor-0 - is the name correct? ** Obsolete normative reference: RFC 3775 (Obsoleted by RFC 6275) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Krishnan 3 Internet-Draft Ericsson 4 Intended status: Informational N. Steinleitner 5 Expires: December 29, 2010 University of Goettingen 6 Y. Qiu 7 Institute for Infocomm Research 8 G. Bajko 9 Nokia 10 June 27, 2010 12 Guidelines for firewall administrators regarding MIPv6 traffic 13 draft-ietf-mext-firewall-admin-03 15 Abstract 17 This document presents some recommendations for firewall 18 administrators to help them configure their existing firewalls in a 19 way that allows in certain deployment scenarios the Mobile IPv6 and 20 DSMIPv6 signaling and data messages to pass through. For other 21 scenarios, the support of additional mechanisms to create pinholes 22 required for MIPv6 will be necessary. This document assumes that the 23 firewalls in question include some kind of stateful packet filtering 24 capability. 26 Status of this Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on December 29, 2010. 43 Copyright Notice 45 Copyright (c) 2010 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 61 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 3 63 4. Home Agent behind a firewall . . . . . . . . . . . . . . . . . 4 64 4.1. Signaling between the MN and the HA . . . . . . . . . . . 5 65 4.2. IKEv2 signaling between MN and HA for establishing SAs . . 5 66 5. Correspondent Node behind a firewall . . . . . . . . . . . . . 6 67 5.1. Route optimization signaling between MN and CN through 68 HA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 69 5.2. Route optimization signaling between MN and CN . . . . . . 7 70 5.3. Binding Update from MN to CN . . . . . . . . . . . . . . . 7 71 5.4. Route Optimization data traffic from MN . . . . . . . . . 7 72 6. Mobile Node behind a firewall . . . . . . . . . . . . . . . . 8 73 6.1. Signaling between MN and HA . . . . . . . . . . . . . . . 8 74 6.2. Data packets between DSMIPv6 . . . . . . . . . . . . . . . 9 75 6.3. Signaling between MN and CN . . . . . . . . . . . . . . . 9 76 6.4. IKEv2 signaling between MN and HA for establishing SAs . . 10 77 7. Related documents . . . . . . . . . . . . . . . . . . . . . . 10 78 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 79 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 80 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 81 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 82 11.1. Normative References . . . . . . . . . . . . . . . . . . . 11 83 11.2. Informative References . . . . . . . . . . . . . . . . . . 11 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 86 1. Requirements notation 88 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 89 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 90 document are to be interpreted as described in [RFC2119]. 92 2. Introduction 94 Network elements such as firewalls are an integral aspect of a 95 majority of IP networks today, given the state of security in the 96 Internet, threats, and vulnerabilities to data networks. MIPv6 97 [RFC3775] defines mobility support for IPv6 nodes. Firewalls will 98 interfere with the smooth operation of the MIPv6 protocol unless 99 specific steps are taken to allow Mobile IPv6 signaling and data 100 messages to pass through the firewall. The problems caused by 101 firewalls to Mobile IPv6 are documented in [RFC4487]. 103 This document presents some recommendations for firewall 104 administrators to help them configure their firewalls in a way that 105 allows the Mobile IPv6 signaling and data messages to pass through. 106 This document assumes that the firewalls in question include some 107 kind of stateful packet filtering capability. The static rules that 108 need to be configured are described in this document. In some 109 scenarios, the support of additional mechanisms to create pinholes 110 required for MIPv6 signalling and data traffic to pass through will 111 be necessary. A possible solution, describing the dynamic 112 capabilities needed for the firewalls to create pinholes based on 113 MIPv6 signalling traffic is described in a companion document 114 [MIP6FWVENDOR]. Other solutions may also be possible. 116 Some Mobile IPv6 signalling messages require the use of encryption to 117 protect the confidentiality of the payload (e.g. the HoTI and HoT 118 messages between the MN and the HA). The other signalling messages 119 allow the use of encryption. If encryption is being used, it is not 120 possible to inspect the contents of the signalling packets. For 121 these messages to get through, a generic rule needs to be added in 122 the firewall to let ESP packets through without further inspection. 124 3. Abbreviations 126 This document uses the following abbreviations: 128 o CN: Correspondent Node 130 o CoA: Care of Address 131 o CoTI: Care of Test Init 133 o HA: Home Agent 135 o HoA: Home Address 137 o HoTI: Home Test Init 139 o HoT: Home Test 141 o MN: Mobile Node 143 o RO: Route Optimization 145 o RRT: Return Routability Test 147 4. Home Agent behind a firewall 149 This section presents the recommendations for configuring a firewall 150 that protects a home agent. 152 +----------------+ +---+ 153 | | | A | 154 | | +---+ 155 | +----+ | External 156 | | HA | +----+ MN 157 | +----+ | FW | +---+ 158 | Home Agent +----+ | B | 159 | of A | +---+ 160 | | External 161 | | Node 162 +----------------+ 163 Network protected 164 by a firewall 166 Figure 1: HA behind a firewall 168 For each type of traffic that needs to pass through this firewall, 169 recommendations are presented on how to identify that traffic. The 170 following types of traffic are considered 172 o Signaling between the MN and the HA 174 o IKEv2 signaling between MN and HA for establishing SAs 176 4.1. Signaling between the MN and the HA 178 The signaling between the MN and HA is protected using IPSec ESP. 179 These messages are critical to the MIPv6 protocol and if these 180 messages are discarded, Mobile IPv6 as specified today will cease to 181 work. In order to permit these messages through, the firewall has to 182 detect the messages using the following patterns. 184 Destination Address: Address of HA 185 Next Header: 50 (ESP) 186 Mobility Header Type: 5 (BU) 188 This pattern will allow the BU messages from MNs to HA to pass 189 through. 191 When an HA supporting DSMIPv6 clients is behind firewall, in order 192 for DSMIPv6 signalling to reach the HA, the firewall has to allow 193 signaling packets sent to HA's UDP port 4191 to pass through: 195 Destination Address: IPv4 address of HA 196 Protocol: 17 (UDP) 197 Port: 4191 199 The firewall may also have a rule allowing IP-in-IP encapsulated 200 traffic to pass through to the HA: 202 Destination Address: IPv4 address of HA 203 Protocol: 4 (IP-in-IP) 205 If the above rule is not created by the firewall, IP encapsulated 206 DSMIPv6 signalling will not reach the HA. A client compliant with , 207 when it does not get a response to the BU, is supposed to resend the 208 BU encapsulated into UDP, with destination port 4191. Thus, even if 209 the above rule is not created the signaling may pass through with the 210 (IPv4 HA, UDP 4191) rule. 212 4.2. IKEv2 signaling between MN and HA for establishing SAs 214 The MN and HA exchange IKEv2 signaling in order to establish the 215 security associations. The security associations so established will 216 later be used for securing the mobility signaling messages. Hence 217 these messages need to be permitted to pass through the firewalls. 218 The following pattern will detect these messages. 220 Destination Address: Address of HA 221 Transport Protocol: UDP 222 Destination UDP Port: 500 224 5. Correspondent Node behind a firewall 226 This section presents the recommendations for configuring a firewall 227 if a node behind it should be able to act as Mobile IPv6 CN. 229 +----------------+ +----+ 230 | | | HA | 231 | | +----+ 232 | | Home Agent 233 | +---+ +----+ of B 234 | |CN | | FW | 235 | | C | +----+ 236 | +---+ | +---+ 237 | | | B | 238 | | +---+ 239 +----------------+ External Mobile 240 Network protected Node 241 by a firewall 243 Figure 2: CN behind a firewall 245 For each type of traffic that needs to pass through this firewall, 246 recommendations are presented on how to identify that traffic. The 247 following types of traffic are considered 249 o Route optimization signaling between MN and CN through HA 251 o Route optimization signaling between MN and CN 253 o Binding Update from MN to CN 255 o Route Optimization data traffic from MN 257 5.1. Route optimization signaling between MN and CN through HA 259 Parts of the initial route optimization signaling has to pass through 260 the HA, namely the HoTI and the HoT messages. Without assistance, 261 the HoTI message from the HA to the CN is not able to traverse the 262 firewall. When only a few priviledged nodes (like servers) are 263 allowed to be contacted by outside nodes, then the following pattern 264 will allow the HoTI messages to reach these nodes: 266 Destination Address: CN Address 268 Mobility Header Type: 1 (HoTI) 270 where CN Address describes the address(es) of the priviledged 271 node(s). This pinhole allows the HoTI message from the HA to the CN 272 to traverse the firewall. The HoT message from the CN to the MN 273 through the HA can traverse the firewall without any assistance. 274 Hence no pinhole is required. 276 5.2. Route optimization signaling between MN and CN 278 Route Optimization allows direct communication of data packets 279 between the MN and a CN without tunnelling it back through the HA. 280 To get route optimization work, the MN has to send a CoTI message 281 directly to the CN, which response with a CoT message. However, a 282 stateful firewall would prevent the CoTI message to pass through as 283 there is no established state on the firewall. When only a few 284 priviledged nodes (like servers) are allowed to be contacted by 285 outside nodes, then the following pattern will allow the CoTI 286 messages to reach these nodes: 288 Destination Address: CN Address 290 Mobility Header Type: 2 (CoTI) 292 where CN Address describes the address(es) of the priviledged 293 node(s).The CoT message from the CN to the MN can traverse the 294 firewall without any assistance. Hence no pinhole is required. 296 5.3. Binding Update from MN to CN 298 After successfully performing the return routability procedure, the 299 MN sends the BU to the CN and expects the BA. Since this BU does not 300 match any previous installed pinhole rules, an additional pinhole 301 with the following format is required.When only a few priviledged 302 nodes (like servers) are allowed to be contacted by outside nodes, 303 then the following pattern will allow the BU messages to reach these 304 nodes: 306 Destination Address: CN Address 308 Mobility Header Type: 5 310 where CN Address describes the address(es) of the priviledged 311 node(s).This allows the BU to traverse the firewall and the BA can 312 pass the firewall without any assistance. Therefore, the Binding 313 Update sequence can be performed successfully. 315 5.4. Route Optimization data traffic from MN 317 Also the Route Optimization data traffic from MN directly to the CN 318 can not traverse the firewall without assistance. A dynamically 319 created pinhole such as the one specified in [MIP6FWVENDOR] will 320 allow this traffic to pass. 322 6. Mobile Node behind a firewall 324 This section presents the recommendations for configuring a firewall 325 that protects the network a mobile node visiting. 327 +----------------+ +----+ 328 | | | HA | 329 | | +----+ 330 | | Home Agent 331 | +---+ +----+ of A +---+ 332 | | A | | FW | | B | 333 | +---+ +----+ +---+ 334 |Internal | External 335 | MN | Node 336 | | 337 +----------------+ 338 Network protected 339 by a firewall 341 Figure 3: MN behind a firewall 343 For each type of traffic that needs to pass through this firewall, 344 recommendations are presented on how to identify that traffic. The 345 following types of traffic are considered 347 o Signaling between MN and HA 349 o Route Optimization Signaling between MN and CN 351 o IKEv2 signaling between MN and HA for establishing SAs 353 6.1. Signaling between MN and HA 355 As described in Section 4.1, the signaling between the MN and HA is 356 protected using IPSec ESP. Currently, a lot of firewalls are 357 configured to block the incoming ESP packets. Moreover, from the 358 view of the firewall, both source and destination addresses of these 359 messages from/to mobile node are variable. Fortunately, for a 360 stateful firewall, if the initial traffic is allowed through the 361 firewall, then the return traffic is also allowed. A mobile node is 362 always the initiator for the BU. Since MN's CoA is not able to be 363 known in advance, the firewall can use following patterns to permit 364 these messages through. 366 Source Address: Visited subnet prefix 367 Destination Address: Address of HA 368 Next Header: 50 (ESP) 369 Mobility Header Type: 5 (BU) 371 This pattern will allow the Binding Update packets to pass through 372 the firewall. Then the return packets (BA from HA to MN) will also 373 able to pass through accordingly. 375 6.2. Data packets between DSMIPv6 377 In case of a DSMIPv6 client with only a v4 CoA, the dynamic rules set 378 by the firewall to allow DSMIPv6 signalling packets pass through 379 between the MN and the HA, may time out and be closed. If that 380 happens, data packets sent by a CN to the MN through the HA will not 381 reach the MN. Therefore, the firewall will need to set a static rule 382 to allow data packets sent from the HA's IPv4 address to the MN's 383 IPv4 CoA using either protocol number 4 (IP-in-IP encapsulation) or 384 17 (UDP), depending on the value of the F bit, to pass through. The 385 UDP port numbers for the rule are to be read from the BU/BA message 386 exchange [RFC5555]. When the firewall chooses to create static rules 387 (without traffic based timeout) for allowing DSMIPv6 signalling pass 388 between the MN and HA, then no further rules need to be created by 389 the firewall, as data packets follow the same tunnel as the 390 signaling. 392 6.3. Signaling between MN and CN 394 Route Optimization allows direct communication of data packets 395 between the MN and a CN without tunneling it back through the HA. It 396 includes 3 pairs of messages: HoTI/HoT, CoTI/CoT and BU/BA. The 397 first pair can pass through the firewall using the pattern described 398 in section 5.1. Here we discuss CoTI/CoT and BU/BA messages. 399 Following pattern permits these messages through the firewall. 401 Source Address: Visited subnet prefix 402 Mobility Header Type: 2 (CoTI) 404 Source Address: Visited subnet prefix 405 Mobility Header Type: 5 (BU) 407 This pattern allows the initial messages (CoTI and BU) from the MN to 408 the CN pass through the firewall. The return messages (CoT and BA) 409 from the CN to the MN can also passes through the firewall 410 accordingly. 412 6.4. IKEv2 signaling between MN and HA for establishing SAs 414 The MN and HA exchange IKEv2 signaling in order to establish the 415 security associations. The security associations so established will 416 later be used for securing the mobility signaling messages. Due to 417 variable source/destination IP addresses and MN always as initiator, 418 the following pattern will let the negotiation pass. 420 Source Address: Visited subnet prefix 421 Transport Protocol: UDP 422 Destination UDP Port: 500 424 7. Related documents 426 There are other IETF published documents that provide recommendations 427 for firewall configuration that can affect Mobile IPv6 messages. 428 [RFC4890] that provides recommendations for filtering ICMPv6 messages 429 (especially Section 4.3.2). [RFC4942] describes security issues 430 present in IPv6 and related protocols (especially Sections 2.1.2 and 431 2.1.15). 433 8. Acknowledgements 435 The authors would like to thank the following members of the MIPv6 436 firewall design team for contributing to this document: Hannes 437 Tschofenig, Hesham Soliman, Yaron Sheffer, and Vijay Devarapalli. 438 The authors would also like to thank William Ivancic, Ryuji Wakikawa, 439 Jari Arkko, Henrik Levkowetz, Pasi Eronen and Noriaki Takamiya for 440 their thorough reviews of the document and for providing comments to 441 improve the quality of the document. 443 9. IANA Considerations 445 This document does not require any IANA action. 447 10. Security Considerations 449 This document specifies recommendations for firewall administrators 450 to allow Mobile IPv6 traffic to pass through unhindered. Since some 451 of this traffic is encrypted it is not possible for firewalls to 452 discern whether it is safe or not. This document recommends a 453 liberal setting so that all legitimate traffic can pass. This means 454 that some malicious traffic may be permitted by these rules. These 455 rules may allow the initiation of Denial of Service attacks against 456 Mobile IPv6 capable nodes (the MNs, CNs and the HAs). 458 11. References 460 11.1. Normative References 462 [MIP6FWVENDOR] 463 Krishnan, S., Sheffer, Y., Steinleitner, N., and G. Bajko, 464 "Guidelines for firewall vendors regarding MIPv6 traffic", 465 draft-ietf-mext-firewall-vendor-0 (work in progress), 466 October 2008. 468 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 469 Requirement Levels", BCP 14, RFC 2119, March 1997. 471 [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support 472 in IPv6", RFC 3775, June 2004. 474 [RFC4487] Le, F., Faccin, S., Patil, B., and H. Tschofenig, "Mobile 475 IPv6 and Firewalls: Problem Statement", RFC 4487, 476 May 2006. 478 [RFC5555] Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and 479 Routers", RFC 5555, June 2009. 481 11.2. Informative References 483 [RFC4890] Davies, E. and J. Mohacsi, "Recommendations for Filtering 484 ICMPv6 Messages in Firewalls", RFC 4890, May 2007. 486 [RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/ 487 Co-existence Security Considerations", RFC 4942, 488 September 2007. 490 Authors' Addresses 492 Suresh Krishnan 493 Ericsson 494 8400 Decarie Blvd. 495 Town of Mount Royal, QC 496 Canada 498 Phone: +1 514 345 7900 x42871 499 Email: suresh.krishnan@ericsson.com 500 Niklas Steinleitner 501 University of Goettingen 502 Lotzestr. 16-18 503 Goettingen 504 Germany 506 Email: steinleitner@cs.uni-goettingen.de 508 Ying Qiu 509 Institute for Infocomm Research 510 21 Heng Mui Keng Terrace 511 Singapore 513 Phone: +65-6874-6742 514 Email: qiuying@i2r.a-star.edu.sg 516 Gabor Bajko 517 Nokia 519 Email: gabor.bajko@nokia.com