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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC1195' is defined on line 788, but no explicit reference was found in the text == Outdated reference: A later version (-04) exists of draft-housley-saag-crypto-key-table-03 Summary: 0 errors (**), 0 flaws (~~), 10 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET DRAFT T. Polk 3 Intended Status: Informational NIST 4 R. Housley 5 Vigil Security 6 Expires: April 28, 2011 October 25, 2010 8 Routing Authentication Using A Database of Long-Lived Cryptographic Keys 9 draft-polk-saag-rtg-auth-keytable-04.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as 19 Internet-Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/1id-abstracts.html 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html 32 Abstract 34 This document describes the application of a database of long-lived 35 cryptographic keys to establish session-specific cryptographic keys 36 to support authentication services in routing protocols. Keys may be 37 established between two peers for pair-wise communications, or 38 between groups of peers for multicast traffic. 40 Table of Contents 42 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 2 43 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 2 44 2 Architecture and Design . . . . . . . . . . . . . . . . . . . . . 3 45 3 Pair-wise Application . . . . . . . . . . . . . . . . . . . . . . 3 46 4 Identifier Mapping . . . . . . . . . . . . . . . . . . . . . . . 5 47 4.1 Selected Range Reservation . . . . . . . . . . . . . . . . . 6 48 4.2 Protocol Specific Mapping Tables . . . . . . . . . . . . . . 6 49 5 Database Maintenance . . . . . . . . . . . . . . . . . . . . . . 6 50 6 Worked Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6 51 6.1 Worked Example: TCP-AO . . . . . . . . . . . . . . . . . . . 7 52 6.1.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . 7 53 6.1.2 Protocol Operation: Xp Initiates a Connection . . . . . 8 54 6.1.3 Protocol Operation: Yp Initiates a Connection . . . . . 9 55 6.2 Worked Example: IS-IS . . . . . . . . . . . . . . . . . . . 9 56 6.2.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . 10 57 6.2.2 Protocol Operations . . . . . . . . . . . . . . . . . 13 58 6.2.2.1 Sending a Hello Message . . . . . . . . . . . . 14 59 6.2.2.2 Receiving a Hello Message . . . . . . . . . . . 14 60 6.2.2.3 Generating a Link State PDU . . . . . . . . . . 15 61 6.2.2.4 Receiving a Link State PDU . . . . . . . . . . . 15 62 6.2.2.5 Sending a Sequence Number PDU . . . . . . . . . 16 63 6.2.2.6 Receiving a Sequence Number PDU . . . . . . . . 16 64 7 Security Considerations . . . . . . . . . . . . . . . . . . . 16 65 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 66 9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 67 10 References . . . . . . . . . . . . . . . . . . . . . . . . . 17 68 10.1 Normative References . . . . . . . . . . . . . . . . . . 17 69 10.2 Informative References . . . . . . . . . . . . . . . . . 17 70 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 71 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 19 73 1 Introduction 75 This document describes the application of a database of long-lived 76 cryptographic keys, as defined in [KEYTAB], to establish session- 77 specific cryptographic keys to provide authentication services in 78 routing protocols. Keys may be established between two peers for 79 pair-wise communications, or between groups of peers for multicast 80 traffic. 82 1.1 Terminology 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 86 document are to be interpreted as described in RFC 2119 [RFC2119]. 88 2 Architecture and Design 90 Figure 1 illustrates the establishment and use of cryptographic keys 91 for authentication in routing protocols. Long-lived cryptographic 92 keys are inserted in a database manually. In the future, we 93 anticipate an automated key management protocol to insert these keys 94 in the database. (While this future environment conceivably includes 95 automated key management protocols to negotiate short-lived 96 cryptographic session keys, such keys are out of scope for this 97 database.) The structure of the database of long-lived cryptographic 98 keys is described in [KEYTAB]. 100 The cryptographic keying material for individual sessions is derived 101 from the keying material stored in the database of long-lived 102 cryptographic keys. A key derivation function (KDF) and its inputs 103 are named in the database of long-lived cryptographic keys; session 104 specific values based on the routing protocol are input the the KDF. 105 Protocol specific key identifiers may be assigned to the 106 cryptographic keying material for individual sessions if needed. 108 +--------------+ +----------------+ 109 | | | | 110 | Manual Key | | Automated Key | 111 | Installation | | Mgmt. Protocol | 112 | | | | 113 +------+-------+ +--+----------+--+ 114 | | | 115 | | | 116 V V |<== Out of scope for this model. 117 +------------------------+ | Often used in other 118 | | | protocol environments 119 | Long-lived Crypto Keys | | like IPsec and TLS. 120 | | | 121 +------------+-----------+ | 122 | | 123 | | 124 V V 125 +---------------------------------+ 126 | | 127 | Short-lived Crypto Session Keys | 128 | | 129 +---------------------------------+ 131 Figure 1. Cryptographic key establishment and use. 133 3 Pair-wise Application 134 Figure 2 illustrates how the long-lived cryptographic keys are 135 accessed and employed when an entity wishes to establish a protected 136 session with a peer. As one step in the initiation process, the 137 initiator requests the set of long term keys associated with the peer 138 for the particular protocol. If the set contains more than one key, 139 the initiator selects one long-term key based on the local policy. 140 The long-term key is provided as an input, along with session- 141 specific information (e.g., ports or initial counters), to a key 142 derivation function. The result is session-specific key material 143 which is used to generate cryptographic authentication. 145 Where the initiator is establishing a multicast session, the Peer in 146 the key request identifies the set of systems that will receive this 147 information. 149 +-------------------------+ 150 | | 151 | Long-Lived | 152 | Crypto Keys | 153 | | 154 +-+---------------------+-+ 155 ^ | 156 | | 157 | V 158 +-------+-------+ +-------+-------+ 159 | | | | 160 | Lookup Keys | | Select Key | 161 | By Peer | | By Policy | 162 | and Protocol | | | 163 | | +-------+-------+ 164 +-------+-------+ | 165 ^ | 166 | V 167 | +-------+-------+ 168 | | | 169 | | Session Key | 170 | | Derivation | 171 | | | 172 | +-------+-------+ 173 | | 174 | | 175 +-------+-------+ V 176 | | +-------+-------+ 177 | Initiate | | | 178 | Session | |Authentication | 179 | with Peer | | Mechanism | 180 | | | | 181 +---------------+ +---------------+ 182 Figure 2. Session Initiation 184 Figure 3 illustrates how the long-lived cryptographic keys are 185 accessed and employed when an entity receives a request establish a 186 protected session with a peer. As step one in the session 187 establishment process, the receiver extracts the keyID for the long- 188 term keyID from the received data. The receiver then requests the 189 specified long-term key from the table. The long-term key is provided 190 as an input, along with session-specific information (e.g., ports or 191 initial counters), to a key derivation function. The result is 192 session-specific key material which is used to verify the 193 cryptographic authentication information. 195 +-------------------------+ 196 | | 197 | Long-Lived | 198 | Crypto Keys | 199 | | 200 +-+---------------------+-+ 201 ^ | 202 | | 203 | V 204 +-------+-------+ +-------+-------+ 205 | | | | 206 | Lookup Key | | Session Key | 207 | By KeyID | | Derivation | 208 | | | | 209 +-------+-------+ +-------+-------+ 210 ^ | 211 | | 212 | V 213 +-------+-------+ +-------+-------+ 214 | | | | 215 | Receive Data | |Authentication | 216 | From Peer | | Mechanism | 217 | | | | 218 +---------------+ +---------------+ 220 Figure 3. Session Acceptance 222 4 Identifier Mapping 224 [KEYTAB] specifies a 16-bit identifier, but protocols already exist 225 with key identifiers of various sizes. Where the identifiers are of 226 different sizes, an extra mapping step may be required. Note that 227 mapping mechanisms are local - that is, different mapping mechanisms 228 could be employed on different peers. 230 In practice, the mapping process need only be applied to the 231 LocalKeyID, whose value must be unique in the context of the 232 database, as defined in [KEYTAB]. Uniqueness is not required for the 233 PeerKeyID, so mapping is generally restricted to truncation. Mapping 234 would only be needed to expand PeerKeyID's value beyond 16 bits. 236 4.1 Selected Range Reservation 238 Where a protocol uses an index of less than 16 bits, a selected range 239 of the local index space can be reserved for a particular protocol. 240 For example, consider two protocols P1 and P2 that each use 8 bit key 241 identifiers. Without identifier mapping these protocols would share 242 the space {0x0000 through 0x00ff} which would limit the pair of 243 protocols to 256 keys in total. By reserving the ranges {0x7f00 244 through 0x7fff} and {0x7e00 through 0x7eff} for P1 and P2 245 respectively permits each protocol to use the full 256 key 246 identifiers and establishes an unambiguous mapping for the protocol 247 key identifiers and local table identifiers. 249 When an initiator selects a key from the set in the table, the given 250 key identifier needs to be masked or shifted to the on-the-wire 251 range. Before requesting a specific key, the receiver would use a 252 shim layer to map the on-the-wire identifier into the reserved range. 254 4.2 Protocol Specific Mapping Tables 256 Each protocol can also maintain a simple mapping table with two 257 fields: the 16 bit index and the protocol specific value: 259 KEYTAB index (16 bits) | Protocol specific index (8 bits) 261 In this case, the host system would maintain separate mapping tables 262 for protocols P1 and P2. 264 5 Database Maintenance 266 The previous sections focus upon installing and using the 267 cryptographic keys in the database. A mechanism or mechanisms to 268 remove unneeded keys is also needed to ensure that the key material 269 up-to-date. [KEYTAB] provides mechanisms for expiration of entries; 270 such key management could be performed in a fully automated fashion. 271 Other reasons for key removal, such as severing a business 272 relationship, or deciding a long lived key has been compromised 273 before its expiration date, would inherently require a manual key 274 removal process. 276 6 Worked Examples 277 6.1 Worked Example: TCP-AO 279 This section describes the way a TCP-AO implementation could use the 280 database. [tcpao] TCP-AO protocol is an example where the key 281 identifier is limited to 8 bits, so an identifier mapping is needed. 283 We will assume two peers Xp and Yp. Xp employs the range reservation 284 method for mapping and has reserved the range {0x7f00 ... 0x7fff} for 285 LocalKeyIDs for TCP-AO, mapping to {0x00 ... 0xff}. Yp employs a 286 protocol specific mapping table in its TCP-AO implementation. 288 The following subsections describe how peers Xp and Yp make use of 289 the database of long-lived cryptographic keys when Xp and Yp 290 respectively initiate a session. (Note: Rollover to new sessions 291 keys during a session is described in [tcpao].) 293 6.1.1 Setup 295 The owners of Xp and Yp determine a need for authenticated 296 communication using TCP-AO. They decide to use AES-CMAC-128 for 297 authentication, so a 128 bit key is needed. They decide to use the 298 same key for both directions (inbound and outbound), and that the key 299 will be available from 12/31/2010 through 12/31/2011. Through an out- 300 of-band channel, the administrators establish the shared secret: 302 0x0123456789ABCDEF0123456789ABCDEF 304 Peer Xp selects the first available TCP-AO identifier in the reserved 305 range, which is 0x7f05 and maps to an eight-bit identifier 0x05. 306 Peer Yp selects the next available TCP-AO identifier, 0x12, and the 307 next available LocalKeyID, which is 0x0107. Peer Yp also adds an 308 entry to its TCP-AO mapping table mapping the LocalKeyID to the TCP- 309 AO identifier, as shown in Figure 5: 311 LocalKeyID TCP-AO identifier 312 -------------------------------- 313 0x001a | 0x01 314 0x004d | 0x02 315 ... ... 316 0x0107 | 0x12 318 Figure 5. Protocol Specific KeyID Mapping Table for TCP-AO 320 After exchanging the TCP-AO identifiers, the peers have sufficient 321 information to establish their [KEYTAB] entries. Peer Xp's [KEYTAB] 322 entry is shown as Figure 6: 324 LocalKeyID 0x7f05 325 PeerKeyID 0x0012 326 KDF ???? 327 KDFInputs none 328 AlgID AES-CMAC-128 329 Key 0x0123456789ABCDEF0123456789ABCDEF 330 Direction both 331 NotBefore 12/31/2010 332 NotAfter 12/31/2011 333 Peers yp.example.com 334 Protocol TCP-AO 336 Figure 6. Key Table Entry on Xp 338 Peer Yp's [KEYTAB] entry is shown as Figure 6: 340 LocalKeyID 0x0107 341 PeerKeyID 0x0005 342 KDF ???? 343 KDFInputs none 344 AlgID AES-CMAC-128 345 Key 0x0123456789ABCDEF0123456789ABCDEF 346 Direction both 347 NotBefore 12/31/2010 348 NotAfter 12/31/2011 349 Peers xp.example.com 350 Protocol TCP-AO 352 Figure 7. Key Table Entry on Yp 354 6.1.2 Protocol Operation: Xp Initiates a Connection 356 Peer Xp wishes to initiate a connection with Peer Yp. 358 (1) Xp performs a key lookup for {Peer=Yp, Protocol=TCP-AO}, and the 359 entry with LocalKeyID 0x7f05 is returned. 360 (2) The LocalKeyID 0x7f05 is range mapped by Xp to the TCP-AO 361 identifier 0x05. 362 (3) Xp performs the session key derivation using the mechanism 363 specified for the TCP-AO protocol in [ao-crypto]. 364 (4) Xp generates the AES-CMAC-128 MACs for the outgoing traffic using 365 the derived key, and asserts the key identifier 0x05 in the packets. 366 (5) Yp receives a protected packet from Xp, and extracts the key 367 identifier 0x05. 368 (6) Yp performs a a key lookup for {Peer=Xp, Protocol=TCP-AO, 369 PeerKeyID=0x05}, and the entry with LocalKeyID 0x0107 is returned. 370 (7) Yp performs the session key derivation using the mechanism 371 specified for the TCP-AO protocol in [ao-crypto]. 372 (8) Yp verifies the MACs for the incoming traffic using the derived 373 key. 375 6.1.3 Protocol Operation: Yp Initiates a Connection 377 Where Peer Yp establishes the connection, the same process is 378 followed, except that the range mapping process from step (2) is 379 replaced by a table lookup. 381 6.2 Worked Example: IS-IS 383 This section describes the way an IS-IS implementation with 384 supporting the IS-IS generic cryptographic authentication mechanism 385 could use the database. [isis] [rfc5310] IS-IS is an interior gateway 386 protocol (IGP) that can be used to support IP as well as OSI. 388 IS-IS routers are grouped into "areas"; routers within the same area 389 establish adjacencies with neighboring routers and share link state 390 information through flooding. Areas are designated as either Level 1 391 or Level 2; Level 1 areas support routing within that area, while 392 Level 2 areas support routing between areas. An IS-IS router can be 393 Level 1, Level 2, or both (designated as Level 1/2). 395 An IS-IS deployment can have multiple Level 1 areas; Level 1 areas 396 are differentiated by area addresses that are unique within the IS-IS 397 deployment. (An IS-IS deployment has only a single Level 2 area; an 398 area address is not needed.) 400 The IS-IS protocol supports routers that are connected by LANs and 401 point-to-point links. Level 1 and Level 2 messages on a LAN are 402 differentiated by the broadcast address. Point-to-Point links may be 403 configured as Level 1, Level 2, or both. 405 This worked example describes how an IS-IS router, denoted Rp, makes 406 use of the database for the following eight cases: 407 * sending a LAN IS to IS Hello PDU 408 * receiving a LAN IS to IS Hello PDU 409 * sending a Point-to-Point IS to IS Hello PDU 410 * receiving a Point-to-Point IS to IS Hello PDU 411 * sending a Link State Packet 412 * receiving a Link State Packet 413 * sending sequence number PDUs 414 * receiving sequence number PDUs 416 In this example, Rp is a Level 1/2 router. Rp has two LAN interfaces; 417 on the first interface (eth0) Rp is connected to other Level 1 418 routers; on the second interface (eth1) Rp is connected to both other 419 Level 1 and Level 2 routers by a LAN. Rp is also connected to one 420 additional Level 1 router, Rq, by a point-to-point link (ppp1). The 421 Level 1 area that Rp participates in has an area address of: 423 0x22 425 The IS-IS protocol supports routers that are connected by LANs and 426 point-to-point links. Level 1 and Level 2 messages on a LAN are 427 differentiated by the broadcast address. For this example, the 428 implementation will use the following broadcast addresses: 430 Level 1: 01-80-C2-00-00-14 431 Level 2: 01-80-C2-00-00-15 433 The authentication mechanism specified in RFC 5310 uses a 16 bit key 434 identifier which matches the key table, so the identifier can be used 435 directly. 437 In this example, an interior router Rp makes use of the database of 438 long-lived cryptographic keys to manage its IS-IS long-term keys. Rp 439 participates in both Level 1 and Level 2. 441 (For this example, we will use a single area address for the Level 1 442 and Level 2 Areas. Note that multiple area addresses can be 443 supported for each area.) 445 In addition to the area addresses that specify the set of recipients, 446 six octet system IDs are used to uniquely identify the sender. The 447 system ID is required to be unique within the area, and in practice 448 is derived from a MAC address. Rp has the following system ID 450 0x123456 452 The Network Entity Title (or NET address) is constructed from the 453 system ID and the area. Rp has the following NET address: 455 Level 1 Area: 0x22123456 457 6.2.1 Setup 459 The owners of the IS-IS system determine a need for authenticated 460 communication between the interior gateways. They decide to use HMAC- 461 SHA1 for authentication with 128 bit keys. 463 For routers that only participate in Level 1, there are two long-term 464 keys: one for hello traffic, and a second for link state PDUs. For 465 routers that participate in both Level 1 and Level 2, two additional 466 long-term keys are required: again, the two keys are used to protect 467 hellos and LSPs, respectively. The owners decide these keys will be 468 available from 12/31/2010 through 12/31/2011. Through an out-of-band 469 channel, the administrators establish the following shared secrets: 471 * a pairwise key for each point-to-point link to protect hello 472 messages; 474 * a multicast key for each broadcast LAN interface for each Level to 475 protect hello messages; 477 * a multicast key for LSP and sequence number packets for each Level 478 1 area; and 480 * a multicast key for LSP and sequence number packets for the Level 2 481 area. 483 Since Rp will send Level 1 hellos on two LANs and a point-to-point 484 link, and Level 2 hellos on one LAN, it will be configured with four 485 IS-IS hello keys. These keys are specified in Figures 8 through 11, 486 respectively. 488 Level 1 hello traffic: 0x0123456789ABCDEF0123456789ABCDEF 489 Level 1 link state PDUs: 0x123456789ABCDEF0123456789ABCDEF0 490 Level 2 hello traffic: 0x23456789ABCDEF0123456789ABCDEF01 491 Level 2 link state PDUs: 0x3456789ABCDEF0123456789ABCDEF012 493 Since the three LAN hello keys are for multicast traffic, the leading 494 bit of the LocalKeyID is required to be 1. PeerkeyID is set to group. 495 There is a pairwsie key for the point-to-point hellos (in Figure 496 10), Since there is no concept of a session, key diversification is 497 not needed. This implies there is no kdf or kdf inputs, and the 498 long-term key is used directly to protect the messages. The 499 algorithm id indicates hmac sha1, and the direction is both inbound 500 and outbound. 502 The key generator selects the first available IS-IS identifier. For 503 a new implementation, any value may be selected. Otherwise, need to 504 not collide. Since Rp participates in both Level 1 and Level 2 areas, 505 Rp installs all four keys. Rp's [KEYTAB] entries are shown as Figures 506 8 through 11: 508 LocalKeyID 0x7101 509 PeerKeyID group 510 KDF none 511 KDFInputs none 512 AlgID HMAC-SHA-1 513 Key 0x0123456789ABCDEF0123456789ABCDEF 514 Interface eth0 515 Direction both 516 NotBefore 12/31/2010 517 NotAfter 12/31/2011 518 Peers 0x22 519 Protocol IS-IS Hello L1 521 Figure 8. Key Table Entry on Rp for Level 1 LAN Hellos on eth0 523 (use ppp1) 525 LocalKeyID 0x7102 526 PeerKeyID 0x7102 527 KDF none 528 KDFInputs none 529 AlgID HMAC-SHA-1 530 Key 0x123456789ABCDEF0123456789ABCDEF0 531 Interface eth1 532 Direction both 533 NotBefore 12/31/2010 534 NotAfter 12/31/2011 535 Peers 0x22 536 Protocol IS-IS Hello L1 538 Figure 9. Key Table Entry on Rp for Level 1 LAN Hellos on eth1 540 LocalKeyID 0x0003 541 PeerKeyID 0x0105 542 KDF none 543 KDFInputs none 544 AlgID HMAC-SHA-1 545 Key 0x23456789ABCDEF0123456789ABCDEF01 546 Interface ppp1 547 Direction both 548 NotBefore 12/31/2010 549 NotAfter 12/31/2011 550 Peers 0x22 551 Protocol IS-IS Hello L1 553 Figure 10. Key Table Entry on Rp for Level 1 point-to-point Hellos 555 LocalKeyID 0x7103 556 PeerKeyID group 557 KDF none 558 KDFInputs none 559 AlgID HMAC-SHA-1 560 Key 0x3456789ABCDEF0123456789ABCDEF012 561 Interface eth1 562 Direction both 563 NotBefore 12/31/2010 564 NotAfter 12/31/2011 565 Peers 0x22 566 Protocol IS-IS Hello L2 568 Figure 11. Key Table Entry on Rp for Level 2 Hellos on eth1 570 Rp also requires two multicast keys for flooding Link State Packets 571 and Sequence number packets. The first key is shared throughout the 572 Level 1 Area 0x22; the second key is shared amongst the routers in 573 the Level 2. Rp's [KEYTAB] entries for the two multicast LSP/sequence 574 number packet keys are shown as Figures 12 and 13: 576 LocalKeyID 0x7104 577 PeerKeyID group 578 KDF none 579 KDFInputs none 580 AlgID HMAC-SHA-1 581 Key 0x456789ABCDEF0123456789ABCDEF0123 582 Interface * 583 Direction both 584 NotBefore 12/31/2010 585 NotAfter 12/31/2011 586 Peers 0x22 587 Protocol IS-IS LSP L1 589 Figure 12. Key Table Entry on Rp for Level 1 LSPs and Sequence Number 590 packets 592 LocalKeyID 0x7105 593 PeerKeyID group 594 KDF none 595 KDFInputs none 596 AlgID HMAC-SHA-1 597 Key 0x56789ABCDEF0123456789ABCDEF01234 598 Interface * 599 Direction both 600 NotBefore 12/31/2010 601 NotAfter 12/31/2011 602 Peers IS-IS L2 603 Protocol IS-IS LSP L2 605 Figure 13. Key Table Entry on Rp for Level 1 LSPs and Sequence Number 606 packets 608 6.2.2 Protocol Operations 610 The following subsections describe how an IS-IS router makes use of 611 the database for the following four cases: 613 * sending a Hello message 614 * receiving a Hello message 615 * sending a Link State Packet 616 * receiving a Link State Packet 617 * sending a sequence number PDU 618 * receiving a sequence number PDU 620 6.2.2.1 Sending a Hello Message 622 Rp wishes to send a Hello message. Because Rp is configured with 623 three Level 1 interfaces, and one Level 2 interface, four different 624 hjello messages will be transmitted. Each message is protected with 625 the key IS-IS Hello key for that interface and level. 627 For each LAN interface: 629 (1) Rp performs a key lookup for the interface (e.g., eth0 or eth1) 630 with the protocol "IS-IS Hello L1". 631 (2) Rp parses the key entry and determines the algorithm attribute 632 (in this example, the algorithm attribute is always HMAC-SHA1). 633 (3) Rp constructs the outgoing LAN Hello PDU. If replay protection 634 is a concern, Rp includes a timestamp with the local time. 635 (4) Rp generates the SHA1-HMAC for the outgoing LAN Hello using the 636 long-term key, and asserts the appropriate key identifier in the RFC 637 5310 authentication mechanism TLV. 638 (5) Rp transmits the Hello message on the LAN interface using the 639 Level 1 broadcast MAC address. 641 For the point-to-point HELLO: 643 (1) Rp performs a key lookup for the interface (ppp1) and protocol 644 "IS-IS Hello L1". 645 (2) Rp parses the key entry and determines the algorithm attribute 646 (i.e., HMAC-SHA1). 647 (3) Rp constructs the outgoing point-to-point Hello PDU. If replay 648 protection is a concern, Rp includes a timestamp with the local time. 649 (4) Rp generates the SHA1-HMAC for the outgoing point-to-point LAN 650 Hello using the long-term key, and asserts the key identifier in the 651 RFC 5310 authentication mechanism TLV. 652 (5) Rp transmits the Hello message over the point-to-point link. 654 6.2.2.2 Receiving a Hello Message 656 Rp processes hello messages by the following algorithm: 658 (1) Rp parses the RFC 5310 authentication mechanism TLV and retrieves 659 the performs a key lookup using the included PeerKeyID. 660 (2) Rp parses the key entry and 661 (a) Rp verifies the keyID is associated with this interface. If 662 the interface does not match, the sender or receiver is 663 misconfigured. An alarm is triggered and the hello is discarded. 664 Otherwise, continue with (2)(b). 665 (b) Rp determines the algorithm attribute (in this case, HMAC- 666 SHA1). 667 (3) Rp calculates the SHA1-HMAC and compares it to the value in the 668 Hello. If the HMACs do not match, the message is discarded. 669 (Otherwise proceed to step 4.) 670 (4) Rp checks the timestamp state for the sender. (If the timestamp 671 value is NULL, proceed to 6. If there is a timestamp value for this 672 sender, proceed to step 7). 673 (5) Rp extracts the timestamp, if any, and compares it to the value 674 in the Hello. If the timestamp is earlier than the stored timestamp, 675 or no timestamp was present, the Hello message is discarded. If the 676 timestamp is later than the stored timestamp, update the stored value 677 and process the Hello message. 678 (6) Process the hello message. 680 [Note that there is no different in processing for LAN or Point-to- 681 point hellos.] 683 6.2.2.3 Generating a Link State PDU 685 Rp wishes to send a link state PDU to the other routers. To perform 686 this task, Rp constructs two separate LSPs, protected by its Level 1 687 and Level 2 LSP keys. The LSPs are transmitted to each neighbor that 688 has formed an adjacency with Rp. 690 (1) Rp performs a key lookup for protocol "IS-IS L1 Flood". (The 691 entry with PeerKeyID 0x7104 is returned.) 692 (2) Rp parses the key entry and determines the algorithm attribute 693 (HMAC-SHA1). 694 (3) Rp constructs the link state PDU. Note that this includes a 695 sequence number. 696 (4) Rp generates the appropriate MAC for the outgoing LSP using the 697 long-term key, and asserts the key identifier 0x7104 in the RFC 5310 698 authentication mechanism TLV. 699 (5) Rp transmits the LSP to all current L1 neighboring adjacencies. 701 The process is repeated for Level 2, beginning with a key lookup for 702 protocol "IS-IS L2 Flood"". 704 Note that there is no difference when sending partial or full link 705 state PDUs. 707 6.2.2.4 Receiving a Link State PDU 708 Rp processes incoming link state PDUs by the following algorithm: 710 (1) Rp parses the RFC 5310 authentication mechanism TLV and retrieves 711 the performs a key lookup using the PeerKeyID. 712 (2) Rp parses the key entry and determines the algorithm attribute 713 (HMAC-SHA1) 714 (3) Rp calculates the SHA1-HMAC and compares it to the value in the 715 link state PDU. If the HMACs do not match, the message is discarded. 716 (Otherwise proceed to step 4.) 717 (4) Rp performs IS-IS processing to ensure the message is fresh 718 (e.g., checks the sequence number for the sender.) If Rp already has 719 fresher information, the packet is discarded. Otherwise, perform step 720 5. 721 (5) Rp forwards the verified Link State PDU to all neighbors with the 722 same level except the neighbor that transmitted the PDU. (That is, 723 Level 1 Link State PDUs are forwarded to Level 1 neighbors; Level 2 724 Link State PDUs are forwarded to Level 2 neighbors.) 726 6.2.2.5 Sending a Sequence Number PDU 728 Same process as in 6.2.2.3. 730 6.2.2.6 Receiving a Sequence Number PDU 732 Same process as in 6.2.2.4. 734 7 Security Considerations 736 The "hello" message processing examples assume the existence of a 737 timestamp extension to provide replay protection. Sequence numbers 738 for hello messages would provide an alternative solution; the authors 739 selected a timestamp since this imposes no state on the sender. Time 740 synchronization is not needed to achieve replay protection; receivers 741 that desire replay protection simply retain the timestamp from the 742 previous hello for comparison. 744 By requiring an IS-IS router to begin using timestamps immediately 745 upon key change, or not at all, step (x) in 6.2.2.2 could have been 746 omitted. By verifying that previous messages did not have a 747 timestamp, a receiver prevents replay of a past hello message that 748 did not include timestamps that was protected with the current key. 750 The timestamp was omitted from the point-to-point hello in the 751 example based on an assumption of physically protected media. If that 752 is not the case, the timestamp could be included in these messages as 753 well. 755 8 IANA Considerations 757 This document requires no actions by IANA. 759 9 IANA Considerations 761 Mike Shand was amazingly patient and helpful, demystifying and 762 explaining IS-IS. The authors are grateful for his assistance. Any 763 remaining mistakes in section 6.2 are the responsibility of the 764 authors, of course! 766 10 References 768 10.1 Normative References 770 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 771 Requirement Levels", BCP 14, RFC 2119, March 1997. 773 [KEYTAB] R. Housley and Polk, T. "Database of Long-Lived 774 Cryptographic Keys", draft-housley-saag-crypto-key-table- 775 03.txt, October 2010. 777 10.2 Informative References 779 [tcpao] J. Touch, Mankin A., and Bonica R. "The TCP Authentication 780 Option", draft-ietf-tcpm-tcp-auth-opt-08.txt, October 781 2009. 783 [ao-crypto] Lebovitz, G., "Cryptographic Algorithms, Use, & 784 Implementation Requirments for TCP Authentication 785 Option", draft-lebovitz-ietf-tcpm-tcp-ao-crypto-02.txt, 786 July 2009. 788 [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and 789 dual environments", RFC 1195, December 1990. 791 [rfc5310] M. Bhatia, Manral, V., Li, T., Atkinson, R., White, R. 792 and Fanto, M. "IS-IS Generic Cryptographic 793 Authentication", RFC 5310, February 2009 795 Author's Addresses 797 Tim Polk 798 National Institute of Standards and Technology 799 100 Bureau Drive, Mail Stop 8930 800 Gaithersburg, MD 20899-8930 801 USA 802 EMail: tim.polk@nist.gov 804 Russell Housley 805 Vigil Security, LLC 806 918 Spring Knoll Drive 807 Herndon, VA 20170 808 USA 809 EMail: housley@vigilsec.com 811 Full Copyright Statement 813 Copyright (c) 2010 IETF Trust and the persons identified as the 814 document authors. All rights reserved. 816 This document is subject to BCP 78 and the IETF Trust's Legal 817 Provisions Relating to IETF Documents 818 (http://trustee.ietf.org/license-info) in effect on the date of 819 publication of this document. 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