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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'I-D.hartman-karp-mrkmp' is defined on line 485, but no explicit reference was found in the text == Unused Reference: 'RFC4107' is defined on line 509, but no explicit reference was found in the text == Outdated reference: A later version (-10) exists of draft-ietf-karp-crypto-key-table-08 == Outdated reference: A later version (-16) exists of draft-yeung-g-ikev2-06 -- Obsolete informational reference (is this intentional?): RFC 6822 (Obsoleted by RFC 8202) Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 KARP Working Group U. Chunduri 3 Internet-Draft A. Tian 4 Intended status: Informational W. Lu 5 Expires: April 23, 2014 Ericsson Inc., 6 October 20, 2013 8 KARP IS-IS security analysis 9 draft-ietf-karp-isis-analysis-01 11 Abstract 13 This document analyzes the threats applicable for Intermediate system 14 to Intermediate system (IS-IS) routing protocol and security gaps 15 according to the KARP Design Guide. This document also provides 16 specific requirements to address the gaps with both manual and auto 17 key management protocols. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on April 23, 2014. 36 Copyright Notice 38 Copyright (c) 2013 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 55 1.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Current State . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2.1. Key Usage . . . . . . . . . . . . . . . . . . . . . . . . 4 58 2.1.1. Sub network Independent . . . . . . . . . . . . . . . 4 59 2.1.2. Sub network dependent . . . . . . . . . . . . . . . . 4 60 2.2. Key Agility . . . . . . . . . . . . . . . . . . . . . . . 5 61 2.3. Security Issues . . . . . . . . . . . . . . . . . . . . . 5 62 2.3.1. Replay Attacks . . . . . . . . . . . . . . . . . . . 5 63 2.3.1.1. Current Recovery mechanism for LSPs . . . . . . . 7 64 2.3.2. Spoofing Attacks . . . . . . . . . . . . . . . . . . 7 65 2.3.3. DoS Attacks . . . . . . . . . . . . . . . . . . . . . 8 66 3. Gap Analysis and Security Requirements . . . . . . . . . . . 8 67 3.1. Manual Key Management . . . . . . . . . . . . . . . . . . 8 68 3.2. Key Management Protocols . . . . . . . . . . . . . . . . 9 69 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 70 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 71 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 72 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 73 7.1. Normative References . . . . . . . . . . . . . . . . . . 11 74 7.2. Informative References . . . . . . . . . . . . . . . . . 11 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 77 1. Introduction 79 This document analyzes the current state of Intermediate system to 80 Intermediate system (IS-IS) protocol according to the requirements 81 set forth in [RFC6518] for both manual and auto key management 82 protocols. 84 With currently published work, IS-IS meets some of the requirements 85 expected from a manually keyed routing protocol. Integrity 86 protection is expanded with more cryptographic algorithms and also 87 limited algorithm agility (HMAC-SHA family) is provided with 88 [RFC5310]. Basic form of Intra-connection re-keying capability is 89 provided by the specification [RFC5310] with some gaps as explained 90 in Section 3. 92 This draft summarizes the current state of cryptographic key usage in 93 IS-IS protocol and several previous efforts to analyze IS-IS 94 security. This includes base IS-IS specification [RFC1195], 95 [RFC5304], [RFC5310] and the OPSEC working group document [RFC6039]. 96 Authors would like to acknowledge all the previous work done in the 97 above documents. 99 This document also analyzes applicability of various threats as 100 described in [RFC6862] to IS-IS, lists gaps and provide specific 101 recommendations to thwart the applicable threats for both manual 102 keying and for auto key management mechanisms. 104 1.1. Requirements Language 106 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 107 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 108 document are to be interpreted as described in RFC 2119 [RFC2119]. 110 1.2. Acronyms 112 IGP - Interior Gateway Protocol. 114 IIH - IS-IS HELLO PDU. 116 IPv4 - Internet Protocol version 4. 118 KMP - Key Management Protocol (auto key management). 120 LSP - IS-IS Link State PDU. 122 MKM - Manual Key management Protocols. 124 NONCE - Number Once. 126 SA - Security Association. 128 SNP - Sequence number PDU. 130 2. Current State 132 IS-IS is specified in International Standards Organization (ISO) 133 10589, with extensions to support Internet Protocol version 4 (IPv4) 134 described in [RFC1195]. The specification includes an authentication 135 mechanism that allows for any authentication algorithm and also 136 specifies the algorithm for clear text passwords. Further [RFC5304] 137 extends the authentication mechanism to work with HMAC-MD5 and also 138 modifies the base protocol for more effectiveness. [RFC5310] 139 provides algorithm agility, with new generic crypto authentication 140 mechanism (CRYPTO_AUTH) for IS-IS. The CRYPTO_AUTH also introduces 141 Key ID mechanism that map to unique IS-IS Security Associations 142 (SAs). 144 The following sections describe the current authentication key usage 145 for various IS-IS messages, current key change methodologies and the 146 various potential security threats. 148 2.1. Key Usage 150 IS-IS can be provisioned with a per interface, peer-to-peer key for 151 IS-IS HELLO PDUs (IIH) and a group key for Link State PDUs (LSPs) and 152 Sequence number PDUs (SNPs). If provisioned, IIH packets potentially 153 can use the same group key used for LSPs and SNPs. 155 2.1.1. Sub network Independent 157 Link State PDUs, Complete and partial Sequence Number PDUs come under 158 Sub network Independent messages. For protecting Level-1 SNPs and 159 Level-1 LSPs, provisioned Area Authentication key is used. Level-2 160 SNPs as well as Level-2 LSPs use the provisioned domain 161 authentication key. 163 Since authentication is performed on the LSPs transmitted by an IS, 164 rather than on the LSP packets transmitted to a specific neighbor, it 165 is implied that all the ISes within a single flooding domain must be 166 configured with the same key in order for authentication to work 167 correctly. This is also true for SNP packets, though they are 168 limited to link local scope in broadcast networks. 170 If multiple instances share the circuits as specified in [RFC6822], 171 instance specific authentication credentials can be used to protect 172 the LSPs and SNPs with in an area or domain. It is important to 173 note, [RFC6822] also allows usage of topology specific authentication 174 credentials with in an instance for the LSPs and SNPs. 176 2.1.2. Sub network dependent 178 IS-IS HELLO PDUs use the Link Level Authentication key, which may be 179 different from that of LSPs and SNPs. This could be particularly 180 true for point-to-point links. In broadcast networks it is possible 181 to provision the same common key used for LSPs and SNPs, to protect 182 IIH messages. This allows neighbor discovery and adjacency formation 183 with more than one neighbor on the same physical interface. If 184 multiple instances share the circuits as specified in [RFC6822], 185 instance specific authentication credentials can be used to protect 186 Hello messages. 188 2.2. Key Agility 190 Key roll over without effecting the routing protocols operation in 191 general and IS-IS in particular, is necessary for effective key 192 management protocol integration. 194 Current HMAC-MD5 crypto authentication as defined in [RFC5304], 195 suggests a transition mode, so that ISes use a set of keys when 196 verifying the authentication value, to allow key changes. This 197 approach will allow changing the authentication key manually without 198 bringing down the adjacency and without dropping any control packet. 199 But, this can increase the load on control plane for the key 200 transition duration as each control packet may have to be verified by 201 more than one key and also allows to mount a potential Denial of 202 Service (DoS) attack in the transition duration. 204 The above situation is improved with the introduction of Key ID 205 mechanism as defined in [RFC5310]. With this, the receiver 206 determines the active security association (SA) by looking at the Key 207 ID field in the incoming PDU and need not try with other keys, when 208 the integrity check or digest verification fails. But, neither Key 209 co-ordination across the group nor exact key change mechanism is 210 clearly defined. [RFC5310] says: " Normally, an implementation would 211 allow the network operator to configure a set of keys in a key chain, 212 with each key in the chain having a fixed lifetime. The actual 213 operation of these mechanisms is outside the scope of this document." 215 2.3. Security Issues 217 The following section analyzes various security threats possible, in 218 the current state for IS-IS protocol. 220 2.3.1. Replay Attacks 222 Replaying a captured protocol packet to cause damage is a common 223 threat for any protocol. Securing the packet with cryptographic 224 authentication information alone can not mitigate this threat 225 completely. Though this problem is more prevalent in broadcast 226 networks it is important to note, most of the IGP deployments use 227 P2P-over-lan [RFC5309], which makes an adversary replay 'easier' than 228 the traditional P2P networks 230 In intra-session replay attacks a secured protocol packet of the 231 current session is replayed, can cause damage, if there is no other 232 mechanism to confirm this is a replay packet. In inter-session 233 replay attacks, captured packet from one of the previous session can 234 be replayed to cause the damage. IS-IS packets are vulnerable to 235 both these attacks, as there is no sequence number verification for 236 IIH packets and SNP packets. Also with current manual key management 237 periodic key changes across the group are done rarely. Thus the 238 intra-connection and inter-connection replay requirements are not 239 met. 241 IS-IS specifies the use of the HMAC-MD5 [RFC5304] and HMAC-SHA-1 242 family in [RFC5310], to protect IS-IS packets. An adversary could 243 replay old IIHs or replay old SNPs that would cause churn in the 244 network or bring down the adjacencies. 246 1. At the time of adjacency bring up an IS sends IIH packet with 247 empty neighbor list (TLV 6) and with the authentication 248 information as per provisioned authentication mechanism. If this 249 packet is replayed later on the broadcast network, all ISes in 250 the broadcast network can bounce the adjacency to create a huge 251 churn in the network. 253 2. Today LSPs have intra-session replay protection as LSP header 254 contains 32-bit sequence number which is verified for every 255 received packet against the local LSP database. But, if a node 256 in the network is out of service (is undergoing some sort of high 257 availability condition, or an upgrade) for more than LSP refresh 258 time and the rest of the network ages out the LSPs of the node 259 under consideration, an adversary can potentially plunge in 260 inter-session replay attacks in the network. If the key is not 261 changed in the above circumstances, attack can be launched by 262 replaying a old LSP with higher sequence number and fewer 263 prefixes or fewer adjacencies. This may force the receiver to 264 accept and remove the routes from the routing table, which 265 eventually causes traffic disruption to those prefixes. However, 266 as per the IS-IS specification there is a built-in recovery 267 mechanism for LSPs from inter-session replay attacks and it is 268 further discussed in Section 2.3.1.1. 270 3. In any IS-IS network (broadcast or otherwise), if a old and an 271 empty Complete Sequence Number packet (CSNP) is replayed this can 272 cause LSP flood in the network. Similarly a replayed Partial 273 Sequence Number packet (PSNP) can cause LSP flood in the 274 broadcast network. 276 2.3.1.1. Current Recovery mechanism for LSPs 278 In the event of inter-session replay attack by an adversary, as LSP 279 with higher sequence number gets accepted, it also gets propagated 280 until it reaches the originating node of the LSP. The originator 281 recognizes the LSP is "newer" than in the local database and this 282 prompts the originator to flood a newer version of the LSP with 283 higher sequence number than the received. This newer version can 284 potentially replace any versions of the replayed LSP which may exist 285 in the network. 287 But in the above process, depending on where in the network the 288 replay is initiated, how quick the nodes in the network react to the 289 replayed LSP and also how different the content in the accepted LSP 290 determines the damage caused by the replayed LSP. 292 2.3.2. Spoofing Attacks 294 IS-IS shares the same key between all neighbors in an area or in a 295 domain to protect the LSP, SNP packets and in broadcast networks even 296 IIH packets. False advertisement by a router is not within scope of 297 the KARP work. However, given the wide sharing of keys as described 298 above, there is a significant risk that an attacker can compromise a 299 key from one device, and use it to falsely participate in the 300 routing, possibly even in a very separate part of the network. 302 If the same underlying topology is shared across multiple instances 303 to transport routing/application information as defined in [RFC6822], 304 it is necessary to use different authentication credentials for 305 different instances. In this connection, based on the deployment 306 considerations, if certain topologies in a particular IS-IS instance 307 require more protection from spoofing attacks and less exposure, 308 topology specific authentication credentials can be used for LSPs and 309 SNPs as facilitated in [RFC6822]. 311 Currently possession of the key it self is used as authentication 312 check and there is no identity check done separately. Spoofing 313 occurs when an illegitimate device assumes the identity of a 314 legitimate one. An attacker can use spoofing as a means for 315 launching various types of attacks. For example: 317 1. The attacker can send out unrealistic routing information that 318 might cause the disruption of network services such as block 319 holes. 321 2. A rogue system having access to the common key used to protect 322 the LSP, can send an LSP, setting the Remaining Lifetime field to 323 zero, and flooding it thereby initiating a purge. Subsequently, 324 this also can cause the sequence number of all the LSPs to 325 increase quickly to max out the sequence number space, which can 326 cause an IS to shut down for MaxAge + ZeroAgeLifetime period to 327 allow the old LSPs to age out in other ISes of the same flooding 328 domain. 330 2.3.3. DoS Attacks 332 Denial-of-service (DoS) attacks using the authentication mechanism is 333 possible and an attacker can send packets which can overwhelm the 334 security mechanism itself. An example is initiating an overwhelming 335 load of spoofed but integrity protected protocol packets, so that the 336 receiver needs to process the integrity check, only to discard the 337 packet. This can cause significant CPU usage. DoS attacks are not 338 generally preventable with in the routing protocol. As the attackers 339 are often remote, the DoS attacks are more damaging to area-scoped or 340 domain-scoped packet receivers than link-local scoped packet 341 receivers. 343 3. Gap Analysis and Security Requirements 345 This section outlines the differences between the current state of 346 the IS-IS routing protocol and the desired state as specified in KARP 347 Design Guidelines [RFC6518]. The section focuses on where IS-IS 348 protocol fails to meet general requirements as specified in the 349 threats and requirements document. 351 This section also describes security requirements that should be met 352 by IS-IS implementations that are secured by manual as well as auto 353 key management protocols. 355 3.1. Manual Key Management 357 1. With CRYPTO_AUTH specification [RFC5310], IS-IS packets can be 358 protected with HMAC-SHA family of cryptographic algorithms. The 359 specification provides the limited algorithm agility (SHA 360 family). By using Key IDs, it also conceals the algorithm 361 information from the protected control messages. 363 2. Even though both intra and inter session replay attacks are best 364 prevented by deploying key management protocols with frequent key 365 change capability, basic constructs for sequence number should be 366 there in the protocol messages. So, some basic or extended 367 sequence number mechanism should be in place to protect IIH 368 packets and SNP packets. The sequence number should be increased 369 for each protocol packet. This allows mitigation of some of the 370 replay threats as mentioned in Section 2.3.1. 372 3. Any common key mechanism with keys shared across a group of 373 routers is susceptible to spoofing attacks caused by a malicious 374 router. Separate authentication check (apart from the integrity 375 check to verify the digest) with digital signatures as described 376 in [RFC2154], can effectively nullify this attack. But this 377 approach was never deployed and one can only assume due to 378 operational considerations at that time. The alternative 379 approach to thwart this threat would be by using the keys from 380 the group key management protocol. As the group key(s) are 381 generated by authenticating the member ISes in the group first, 382 and then periodically rekeyed, per packet identity or 383 authentication check may not be needed. 385 4. In general DoS attacks may not be preventable with mechanism from 386 routing protocols itself. But some form of Admin controlled 387 lists (ACLs) at the forwarding plane can reduce the damage. 388 There are some other forms the DoS attacks common to any protocol 389 are not in scope as per the section 3.3 in [RFC6862]. 391 As discussed in Section 2.2, though Key ID mechanism in [RFC5310] 392 helps, better key co-ordination mechanism for key roll over is 393 desirable even with manual key management. But, it fell short of 394 specifying exact mechanism other than using key chains. The specific 395 requirements: 397 a. Keys SHOULD be able to change without affecting the established 398 adjacency and even better without any control packet loss. 400 b. Keys SHOULD be able to change without effecting the protocol 401 operations, for example, LSP flooding should not be held for a 402 specific Key ID availability. 404 c. Any proposed mechanism SHOULD also be further incrementally 405 deployable with key management protocols. 407 3.2. Key Management Protocols 409 In broadcast deployments, the keys used for protecting IS-IS 410 protocols messages can, in particular, be group keys. A mechanism, 411 similar to as described in [I-D.weis-gdoi-mac-tek] can be used to 412 distribute group keys to a group of ISes in Level-1 area or Level-2 413 domain, using GDOI as specified in [RFC6407]. There are also similar 414 approaches with IKEv2 based group key management solutions, to 415 routing protocols as described in [I-D.yeung-g-ikev2] and [I-D 416 .hartman-karp-mrkmp]. 418 If a group key is used, the authentication granularity becomes group 419 membership of devices, not peer authentication between devices. 421 Group key management protocol deployed SHOULD be capable of 422 supporting rekeying support. 424 In some deployments, where IS-IS point-to-point (P2P) mode is used 425 for adjacency bring-up, sub network dependent messages (IIHs) can use 426 a different key shared between the two point-to-point peers, while 427 all other messages use a group key. When group keying mechanism is 428 deployed, even the P2P IIHs can be protected with the common group 429 keys. This approach facilitates one key management mechanism instead 430 of both pair-wise keying and group keying protocols to be deployed 431 together. If same circuits are shared across multiple instances, the 432 granularity of the group can become per instance for IIHs and per 433 instance/topology for LSPs and SNPs as specified in the [RFC6822]. 435 Effective key change capability with in the routing protocol which 436 allows key roll over without impacting the routing protocol 437 operation, is one of the requirements for deploying any group key 438 mechanism. Once such mechanism is in place with deployment of group 439 key management protocol, IS-IS can be protected from various threats 440 not limited to intra and inter session replay attacks and spoofing 441 attacks. 443 Specific use of crypto tables [I-D.ietf-karp-crypto-key-table] should 444 be defined for IS-IS protocol. 446 4. IANA Considerations 448 This document defines no new namespaces. 450 5. Security Considerations 452 This document is mostly about security considerations of IS-IS 453 protocol, lists potential threats and security requirements for 454 solving those threats. This document does not introduce any new 455 security threats for IS-IS protocol. For more detailed security 456 considerations please refer the Security Considerations section of 457 the KARP Design Guide [RFC6518] document as well as KARP threat 458 document [RFC6862]. 460 6. Acknowledgements 462 Authors would like to thank Joel Halpern for initial discussions on 463 this document and giving valuable review comments. Authors would 464 like to acknowledge Naiming Shen for reviewing and providing feedback 465 on this document. 467 7. References 468 7.1. Normative References 470 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 471 dual environments", RFC 1195, December 1990. 473 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 474 Requirement Levels", BCP 14, RFC 2119, March 1997. 476 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic 477 Authentication", RFC 5304, October 2008. 479 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 480 and M. Fanto, "IS-IS Generic Cryptographic 481 Authentication", RFC 5310, February 2009. 483 7.2. Informative References 485 [I-D.hartman-karp-mrkmp] 486 Hartman, S., Zhang, D., and G. Lebovitz, "Multicast Router 487 Key Management Protocol (MaRK)", draft-hartman-karp- 488 mrkmp-05 (work in progress), September 2012. 490 [I-D.ietf-karp-crypto-key-table] 491 Housley, R., Polk, T., Hartman, S., and D. Zhang, 492 "Database of Long-Lived Symmetric Cryptographic Keys", 493 draft-ietf-karp-crypto-key-table-08 (work in progress), 494 July 2013. 496 [I-D.weis-gdoi-mac-tek] 497 Weis, B. and S. Rowles, "GDOI Generic Message 498 Authentication Code Policy", draft-weis-gdoi-mac-tek-03 499 (work in progress), September 2011. 501 [I-D.yeung-g-ikev2] 502 Rowles, S., Yeung, A., Tran, P., and Y. Nir, "Group Key 503 Management using IKEv2", draft-yeung-g-ikev2-06 (work in 504 progress), April 2013. 506 [RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with 507 Digital Signatures", RFC 2154, June 1997. 509 [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic 510 Key Management", BCP 107, RFC 4107, June 2005. 512 [RFC5309] Shen, N. and A. Zinin, "Point-to-Point Operation over LAN 513 in Link State Routing Protocols", RFC 5309, October 2008. 515 [RFC6039] Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues 516 with Existing Cryptographic Protection Methods for Routing 517 Protocols", RFC 6039, October 2010. 519 [RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain 520 of Interpretation", RFC 6407, October 2011. 522 [RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 523 Routing Protocols (KARP) Design Guidelines", RFC 6518, 524 February 2012. 526 [RFC6822] Previdi, S., Ginsberg, L., Shand, M., Roy, A., and D. 527 Ward, "IS-IS Multi-Instance", RFC 6822, December 2012. 529 [RFC6862] Lebovitz, G., Bhatia, M., and B. Weis, "Keying and 530 Authentication for Routing Protocols (KARP) Overview, 531 Threats, and Requirements", RFC 6862, March 2013. 533 Authors' Addresses 535 Uma Chunduri 536 Ericsson Inc., 537 300 Holger Way, 538 San Jose, California 95134 539 USA 541 Phone: 408 750-5678 542 Email: uma.chunduri@ericsson.com 544 Albert Tian 545 Ericsson Inc., 546 300 Holger Way, 547 San Jose, California 95134 548 USA 550 Phone: 408 750-5210 551 Email: albert.tian@ericsson.com 553 Wenhu Lu 554 Ericsson Inc., 555 300 Holger Way, 556 San Jose, California 95134 557 USA 559 Email: wenhu.lu@ericsson.com