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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-13 ** Obsolete normative reference: RFC 4492 (Obsoleted by RFC 8422) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) ** Obsolete normative reference: RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 7539 (Obsoleted by RFC 8439) == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-10 Summary: 4 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force D. Farinacci 3 Internet-Draft lispers.net 4 Intended status: Experimental B. Weis 5 Expires: March 23, 2017 cisco Systems 6 September 19, 2016 8 LISP Data-Plane Confidentiality 9 draft-ietf-lisp-crypto-07 11 Abstract 13 This document describes a mechanism for encrypting LISP encapsulated 14 traffic. The design describes how key exchange is achieved using 15 existing LISP control-plane mechanisms as well as how to secure the 16 LISP data-plane from third-party surveillance attacks. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on March 23, 2017. 35 Copyright Notice 37 Copyright (c) 2016 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3 54 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 55 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 5. Diffie-Hellman Key Exchange . . . . . . . . . . . . . . . . . 4 57 6. Encoding and Transmitting Key Material . . . . . . . . . . . 5 58 7. Shared Keys used for the Data-Plane . . . . . . . . . . . . . 7 59 8. Data-Plane Operation . . . . . . . . . . . . . . . . . . . . 9 60 9. Procedures for Encryption and Decryption . . . . . . . . . . 10 61 10. Dynamic Rekeying . . . . . . . . . . . . . . . . . . . . . . 11 62 11. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 12 63 12. Security Considerations . . . . . . . . . . . . . . . . . . . 12 64 12.1. SAAG Support . . . . . . . . . . . . . . . . . . . . . . 12 65 12.2. LISP-Crypto Security Threats . . . . . . . . . . . . . . 13 66 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 67 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 68 14.1. Normative References . . . . . . . . . . . . . . . . . . 14 69 14.2. Informative References . . . . . . . . . . . . . . . . . 15 70 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 16 71 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 16 72 B.1. Changes to draft-ietf-lisp-crypto-07.txt . . . . . . . . 16 73 B.2. Changes to draft-ietf-lisp-crypto-06.txt . . . . . . . . 17 74 B.3. Changes to draft-ietf-lisp-crypto-05.txt . . . . . . . . 17 75 B.4. Changes to draft-ietf-lisp-crypto-04.txt . . . . . . . . 17 76 B.5. Changes to draft-ietf-lisp-crypto-03.txt . . . . . . . . 17 77 B.6. Changes to draft-ietf-lisp-crypto-02.txt . . . . . . . . 18 78 B.7. Changes to draft-ietf-lisp-crypto-01.txt . . . . . . . . 18 79 B.8. Changes to draft-ietf-lisp-crypto-00.txt . . . . . . . . 18 80 B.9. Changes to draft-farinacci-lisp-crypto-01.txt . . . . . . 18 81 B.10. Changes to draft-farinacci-lisp-crypto-00.txt . . . . . . 19 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 84 1. Introduction 86 The Locator/ID Separation Protocol [RFC6830] defines a set of 87 functions for routers to exchange information used to map from non- 88 routable Endpoint Identifiers (EIDs) to routable Routing Locators 89 (RLOCs). LISP Ingress Tunnel Routers (ITRs) and Proxy Ingress Tunnel 90 Routers (PITRs) encapsulate packets to Egress Tunnel Routers (ETRs) 91 and Reencapsulating Tunnel Routers (RTRs). Packets that arrive at 92 the ITR or PITR are typically not modified, which means no protection 93 or privacy of the data is added. If the source host encrypts the 94 data stream then the encapsulated packets can be encrypted but would 95 be redundant. However, when plaintext packets are sent by hosts, 96 this design can encrypt the user payload to maintain privacy on the 97 path between the encapsulator (the ITR or PITR) to a decapsulator 98 (ETR or RTR). The encrypted payload is unidirectional. However, 99 return traffic uses the same procedures but with different key values 100 by the same xTRs or potentially different xTRs when the paths between 101 LISP sites are asymmetric. 103 This document has the following requirements (as well as the general 104 requirements from [RFC6973]) for the solution space: 106 o Do not require a separate Public Key Infrastructure (PKI) that is 107 out of scope of the LISP control-plane architecture. 109 o The budget for key exchange MUST be one round-trip time. That is, 110 only a two packet exchange can occur. 112 o Use symmetric keying so faster cryptography can be performed in 113 the LISP data plane. 115 o Avoid a third-party trust anchor if possible. 117 o Provide for rekeying when secret keys are compromised. 119 o Support Authenticated Encryption with packet integrity checks. 121 o Support multiple cipher suites so new crypto algorithms can be 122 easily introduced. 124 2. Requirements Notation 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 128 document are to be interpreted as described in [RFC2119]. 130 3. Definition of Terms 132 AEAD: Authenticated Encryption with Additional Data. 134 ICV: Integrity Check Value. 136 LCAF: LISP Canonical Address Format ([LCAF]). 138 xTR: A general reference to ITRs, ETRs, RTRs, and PxTRs. 140 4. Overview 142 The approach proposed in this document is to NOT rely on the LISP 143 mapping system (or any other key infrastructure system) to store 144 security keys. This will provide for a simpler and more secure 145 mechanism. Secret shared keys will be negotiated between the ITR and 146 the ETR in Map-Request and Map-Reply messages. Therefore, when an 147 ITR needs to obtain the RLOC of an ETR, it will get security material 148 to compute a shared secret with the ETR. 150 The ITR can compute 3 shared-secrets per ETR the ITR is encapsulating 151 to. When the ITR encrypts a packet before encapsulation, it will 152 identify the key it used for the crypto calculation so the ETR knows 153 which key to use for decrypting the packet after decapsulation. By 154 using key-ids in the LISP header, we can also get fast rekeying 155 functionality. 157 The key management described in this documemnt is unidirectional from 158 the ITR (the encapsulator) to the ETR (the decapsultor). 160 5. Diffie-Hellman Key Exchange 162 LISP will use a Diffie-Hellman [RFC2631] key exchange sequence and 163 computation for computing a shared secret. The Diffie-Hellman 164 parameters will be passed via Cipher Suite code-points in Map-Request 165 and Map-Reply messages. 167 Here is a brief description how Diff-Hellman works: 169 +----------------------------+---------+----------------------------+ 170 | ITR | | ETR | 171 +------+--------+------------+---------+------------+---------------+ 172 |Secret| Public | Calculates | Sends | Calculates | Public |Secret| 173 +------|--------|------------|---------|------------|--------|------+ 174 | i | p,g | | p,g --> | | | e | 175 +------|--------|------------|---------|------------|--------|------+ 176 | i | p,g,I |g^i mod p=I | I --> | | p,g,I | e | 177 +------|--------|------------|---------|------------|--------|------+ 178 | i | p,g,I | | <-- E |g^e mod p=E | p,g | e | 179 +------|--------|------------|---------|------------|--------|------+ 180 | i,s |p,g,I,E |E^i mod p=s | |I^e mod p=s |p,g,I,E | e,s | 181 +------|--------|------------|---------|------------|--------|------+ 183 Public-key exchange for computing a shared private key [DH] 185 Diffie-Hellman parameters 'p' and 'g' must be the same values used by 186 the ITR and ETR. The ITR computes public-key 'I' and transmits 'I' 187 in a Map-Request packet. When the ETR receives the Map-Request, it 188 uses parameters 'p' and 'g' to compute the ETR's public key 'E'. The 189 ETR transmits 'E' in a Map-Reply message. At this point, the ETR has 190 enough information to compute 's', the shared secret, by using 'I' as 191 the base and the ETR's private key 'e' as the exponent. When the ITR 192 receives the Map-Reply, it uses the ETR's public-key 'E' with the 193 ITR's private key 'i' to compute the same 's' shared secret the ETR 194 computed. The value 'p' is used as a modulus to create the width of 195 the shared secret 's' (see Section 6). 197 6. Encoding and Transmitting Key Material 199 The Diffie-Hellman key material is transmitted in Map-Request and 200 Map-Reply messages. Diffie-Hellman parameters are encoded in the 201 LISP Security Type LCAF [LCAF]. 203 0 1 2 3 204 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 | AFI = 16387 | Rsvd1 | Flags | 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 208 | Type = 11 | Rsvd2 | 6 + n | 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | Key Count | Rsvd3 | Cipher Suite | Rsvd4 |R| 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | Key Length | Public Key Material ... | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | ... Public Key Material | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | AFI = x | Locator Address ... | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 Cipher Suite field contains DH Key Exchange and Cipher/Hash Functions 221 The 'Key Count' field encodes the number of {'Key-Length', 'Key- 222 Material'} fields included in the encoded LCAF. The maximum number 223 of keys that can be encoded are 3, each identified by key-id 1, 224 followed by key-id 2, an finally key-id 3. 226 The 'R' bit is not used for this use-case of the Security Type LCAF 227 but is reserved for [LISP-DDT] security. Therefore, the R bit is 228 transmitted as 0 and ignored on receipt. 230 Cipher Suite 0: 231 Reserved 233 Cipher Suite 1: 234 Diffie-Hellman Group: 2048-bit MODP [RFC3526] 235 Encryption: AES with 128-bit keys in CBC mode [AES-CBC] 236 Integrity: Integrated with [AES-CBC] AEAD_AES_128_CBC_HMAC_SHA_256 237 IV length: 16 bytes 239 Cipher Suite 2: 240 Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519] 241 Encryption: AES with 128-bit keys in CBC mode [AES-CBC] 242 Integrity: Integrated with [AES-CBC] AEAD_AES_128_CBC_HMAC_SHA_256 243 IV length: 16 bytes 245 Cipher Suite 3: 246 Diffie-Hellman Group: 2048-bit MODP [RFC3526] 247 Encryption: AES with 128-bit keys in GCM mode [RFC5116] 248 Integrity: Integrated with [RFC5116] AEAD_AES_128_GCM 249 IV length: 12 bytes 251 Cipher Suite 4: 252 Diffie-Hellman Group: 3072-bit MODP [RFC3526] 253 Encryption: AES with 128-bit keys in GCM mode [RFC5116] 254 Integrity: Integrated with [RFC5116] AEAD_AES_128_GCM 255 IV length: 12 bytes 257 Cipher Suite 5: 258 Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519] 259 Encryption: AES with 128-bit keys in GCM mode [RFC5116] 260 Integrity: Integrated with [RFC5116] AEAD_AES_128_GCM 261 IV length: 12 bytes 263 Cipher Suite 6: 264 Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519] 265 Encryption: Chacha20-Poly1305 [CHACHA-POLY] [RFC7539] 266 Integrity: Integrated with [CHACHA-POLY] AEAD_CHACHA20_POLY1305 267 IV length: 8 bytes 269 The "Public Key Material" field contains the public key generated by 270 one of the Cipher Suites defined above. The length of the key in 271 octets is encoded in the "Key Length" field. 273 When an ITR, PITR, or RTR sends a Map-Request, they will encode their 274 own RLOC in the Security Type LCAF format within the ITR-RLOCs field. 275 When a ETR or RTR sends a Map-Reply, they will encode their RLOCs in 276 Security Type LCAF format within the RLOC-record field of each EID- 277 record supplied. 279 If an ITR, PITR, or RTR sends a Map-Request with the Security Type 280 LCAF included and the ETR or RTR does not want to have encapsulated 281 traffic encrypted, they will return a Map-Reply with no RLOC records 282 encoded with the Security Type LCAF. This signals to the ITR, PITR 283 or RTR not to encrypt traffic (it cannot encrypt traffic anyways 284 since no ETR public-key was returned). 286 Likewise, if an ITR or PITR wish to include multiple key-ids in the 287 Map-Request but the ETR or RTR wish to use some but not all of the 288 key-ids, they return a Map-Reply only for those key-ids they wish to 289 use. 291 7. Shared Keys used for the Data-Plane 293 When an ITR or PITR receives a Map-Reply accepting the Cipher Suite 294 sent in the Map-Request, it is ready to create data plane keys. The 295 same process is followed by the ETR or RTR returning the Map-Reply. 297 The first step is to create a shared secret, using the peer's shared 298 Diffie-Hellman Public Key Material combined with device's own private 299 keying material as described in Section 5. The Diffie-Hellman 300 parameters used is defined in the cipher suite sent in the Map- 301 Request and copied into the Map-Reply. 303 The resulting shared secret is used to compute an AEAD-key for the 304 algorithms specified in the cipher suite. A Key Derivation Function 305 (KDF) in counter mode as specified by [NIST-SP800-108] is used to 306 generate the data-plane keys. The amount of keying material that is 307 derived depends on the algorithms in the cipher suite. 309 The inputs to the KDF are as follows: 311 o KDF function. This is HMAC-SHA-256. 313 o A key for the KDF function. This is the computed Diffie-Hellman 314 shared secret. 316 o Context that binds the use of the data-plane keys to this session. 317 The context is made up of the following fields, which are 318 concatenated and provided as the data to be acted upon by the KDF 319 function. 321 Context: 323 o A counter, represented as a two-octet value in network byte order. 325 o The null-terminated string "lisp-crypto". 327 o The ITR's nonce from the Map-Request the cipher suite was included 328 in. 330 o The number of bits of keying material required (L), represented as 331 a two-octet value in network byte order. 333 The counter value in the context is first set to 1. When the amount 334 of keying material exceeds the number of bits returned by the KDF 335 function, then the KDF function is called again with the same inputs 336 except that the counter increments for each call. When enough keying 337 material is returned, it is concatenated and used to create keys. 339 For example, AES with 128-bit keys requires 16 octets (128 bits) of 340 keying material, and HMAC-SHA1-96 requires another 16 octets (128 341 bits) of keying material in order to maintain a consistent 128-bits 342 of security. Since 32 octets (256 bits) of keying material are 343 required, and the KDF function HMAC-SHA-256 outputs 256 bits, only 344 one call is required. The inputs are as follows: 346 key-material = HMAC-SHA-256(dh-shared-secret, context) 348 where: context = 0x0001 || "lisp-crypto" || || 0x0100 350 In contrast, a cipher suite specifying AES with 256-bit keys requires 351 32 octets (256 bits) of keying material, and HMAC-SHA256-128 requires 352 another 32 octets (256 bits) of keying material in order to maintain 353 a consistent 256-bits of security. Since 64 octets (512 bits) of 354 keying material are required, and the KDF function HMAC-SHA-256 355 outputs 256 bits, two calls are required. 357 key-material-1 = HMAC-SHA-256(dh-shared-secret, context) 359 where: context = 0x0001 || "lisp-crypto" || || 0x0200 361 key-material-2 = HMAC-SHA-256(dh-shared-secret, context) 363 where: context = 0x0002 || "lisp-crypto" || || 0x0200 365 key-material = key-material-1 || key-material-2 367 If the key-material is longer than the required number of bits (L), 368 then only the most significant L bits are used. 370 From the derived key-material, the most significant 256 bits are used 371 for the AEAD-key by AEAD ciphers. The 256-bit AEAD-key is divided 372 into a 128-bit encryption key and a 128-bit integrity check key 373 internal to the cipher used by the ITR. 375 8. Data-Plane Operation 377 The LISP encapsulation header [RFC6830] requires changes to encode 378 the key-id for the key being used for encryption. 380 0 1 2 3 381 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 / | Source Port = xxxx | Dest Port = 4341 | 384 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 \ | UDP Length | UDP Checksum | 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 L / |N|L|E|V|I|R|K|K| Nonce/Map-Version |\ \ 388 I +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A 389 S \ | Instance ID/Locator-Status-Bits | |D 390 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |/ 391 | Initialization Vector (IV) | I 392 E +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ C 393 n / | | V 394 c | | | 395 r | Packet Payload with EID Header ... | | 396 y | | | 397 p \ | |/ 398 t +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 400 K-bits indicate when packet is encrypted and which key used 402 When the KK bits are 00, the encapsulated packet is not encrypted. 403 When the value of the KK bits are 1, 2, or 3, it encodes the key-id 404 of the secret keys computed during the Diffie-Hellman Map-Request/ 405 Map-Reply exchange. When the KK bits are not 0, the payload is 406 prepended with an Initialization Vector (IV). The length of the IV 407 field is based on the cipher suite used. Since all cipher suites 408 defined in this document do Authenticated Encryption (AEAD), an ICV 409 field does not need to be present in the packet since it is included 410 in the ciphertext. The Additional Data (AD) used for the ICV is 411 shown above and includes the LISP header, the IV field and the packet 412 payload. 414 When an ITR or PITR receives a packet to be encapsulated, they will 415 first decide what key to use, encode the key-id into the LISP header, 416 and use that key to encrypt all packet data that follows the LISP 417 header. Therefore, the outer header, UDP header, and LISP header 418 travel as plaintext. 420 There is an open working group item to discuss if the data 421 encapsulation header needs change for encryption or any new 422 applications. This document proposes changes to the existing header 423 so experimentation can continue without making large changes to the 424 data-plane at this time. This document allocates 2 bits of the 425 previously unused 3 flag bits (note the R-bit above is still a 426 reserved flag bit as documented in [RFC6830]) for the KK bits. 428 9. Procedures for Encryption and Decryption 430 When an ITR, PITR, or RTR encapsulate a packet and have already 431 computed an AEAD-key (detailed in section Section 7) that is 432 associated with a destination RLOC, the following encryption and 433 encapsulation procedures are performed: 435 1. The encapsulator creates an IV and prepends the IV value to the 436 packet being encapsulated. For GCM and Chacha cipher suites, the 437 IV is incremented for every packet (beginning with a value of 1 438 in the first packet) and sent to the destination RLOC. For CBC 439 cipher suites, the IV is a new random number for every packet 440 sent to the destination RLOC. For the Chacha cipher suite, the 441 IV is an 8-byte random value that is appended to a 4-byte counter 442 that is incremented for every packet (beginning with a value of 1 443 in the first packet). 445 2. Next encrypt with cipher function AES or Chacha20 using the AEAD- 446 key over the packet payload following the AEAD specification 447 referenced in the cipher suite definition. This does not include 448 the IV. The IV must be transmitted as plaintext so the decrypter 449 can use it as input to the decryption cipher. The payload should 450 be padded to an integral number of bytes a block cipher may 451 require. The result of the AEAD operation may contain an ICV, 452 the size of which is defined by the referenced AEAD 453 specification. Note that the AD (i.e. the LISP header exactly as 454 will be prepended in the next step and the IV) must be given to 455 the AEAD encryption function as the "associated data" argument. 457 3. Prepend the LISP header. The key-id field of the LISP header is 458 set to the key-id value that corresponds to key-pair used for the 459 encryption cipher. 461 4. Lastly, prepend the UDP header and outer IP header onto the 462 encrypted packet and send packet to destination RLOC. 464 When an ETR, PETR, or RTR receive an encapsulated packet, the 465 following decapsulation and decryption procedures are performed: 467 1. The outer IP header, UDP header, LISP header, and IV field are 468 stripped from the start of the packet. The LISP header and IV 469 are retained and given to the AEAD decryption operation as the 470 "associated data" argument. 472 2. The packet is decrypted using the AEAD-key and the IV from the 473 packet. The AEAD-key is obtained from a local-cache associated 474 with the key-id value from the LISP header. The result of the 475 decryption function is a plaintext packet payload if the cipher 476 returned a verified ICV. Otherwise, the packet has been tampered 477 with and is discarded. If the AEAD specification included an 478 ICV, the AEAD decryption function will locate the ICV in the 479 ciphertext and compare it to a version of the ICV that the AEAD 480 decryption function computes. If the computed ICV is different 481 than the ICV located in the ciphertext, then it will be 482 considered tampered. 484 3. If the packet was not tampered with, the decrypted packet is 485 forwarded to the destination EID. 487 10. Dynamic Rekeying 489 Since multiple keys can be encoded in both control and data messages, 490 an ITR can encapsulate and encrypt with a specific key while it is 491 negotiating other keys with the same ETR. Soon as an ETR or RTR 492 returns a Map-Reply, it should be prepared to decapsulate and decrypt 493 using the new keys computed with the new Diffie-Hellman parameters 494 received in the Map-Request and returned in the Map-Reply. 496 RLOC-probing can be used to change keys or cipher suites by the ITR 497 at any time. And when an initial Map-Request is sent to populate the 498 ITR's map-cache, the Map-Request flows across the mapping system 499 where a single ETR from the Map-Reply RLOC-set will respond. If the 500 ITR decides to use the other RLOCs in the RLOC-set, it MUST send a 501 Map-Request directly to negotiate security parameters with the ETR. 502 This process may be used to test reachability from an ITR to an ETR 503 initially when a map-cache entry is added for the first time, so an 504 ITR can get both reachability status and keys negotiated with one 505 Map-Request/Map-Reply exchange. 507 A rekeying event is defined to be when an ITR or PITR changes the 508 cipher suite or public-key in the Map-Request. The ETR or RTR 509 compares the cipher suite and public-key it last received from the 510 ITR for the key-id, and if any value has changed, it computes a new 511 public-key and cipher suite requested by the ITR from the Map-Request 512 and returns it in the Map-Reply. Now a new shared secret is computed 513 and can be used for the key-id for encryption by the ITR and 514 decryption by the ETR. When the ITR or PITR starts this process of 515 negotiating a new key, it must not use the corresponding key-id in 516 encapsulated packets until it receives a Map-Reply from the ETR with 517 the same cipher suite value it expects (the values it sent in a Map- 518 Request). 520 Note when RLOC-probing continues to maintain RLOC reachability and 521 rekeying is not desirable, the ITR or RTR can either not include the 522 Security Type LCAF in the Map-Request or supply the same key material 523 as it received from the last Map-Reply from the ETR or RTR. This 524 approach signals to the ETR or RTR that no rekeying event is 525 requested. 527 11. Future Work 529 For performance considerations, newer Elliptic-Curve Diffie-Hellman 530 (ECDH) groups can be used as specified in [RFC4492] and [RFC6090] to 531 reduce CPU cycles required to compute shared secret keys. 533 For better security considerations as well as to be able to build 534 faster software implementations, newer approaches to ciphers and 535 authentication methods will be researched and tested. Some examples 536 are Chacha20 and Poly1305 [CHACHA-POLY] [RFC7539]. 538 12. Security Considerations 540 12.1. SAAG Support 542 The LISP working group received security advice and guidance from the 543 Security Area Advisory Group (SAAG). The SAAG has been involved 544 early in the design process and their input and reviews have been 545 included in this document. 547 Comments from the SAAG included: 549 1. Do not use assymmetric ciphers in the data-plane. 551 2. Consider adding ECDH early in the design. 553 3. Add cipher suites because ciphers are created more frequently 554 than protocols that use them. 556 4. Consider the newer AEAD technology so authentication comes with 557 doing encryption. 559 12.2. LISP-Crypto Security Threats 561 Since ITRs and ETRs participate in key exchange over a public non- 562 secure network, a man-in-the-middle (MITM) could circumvent the key 563 exchange and compromise data-plane confidentiality. This can happen 564 when the MITM is acting as a Map-Replier, provides its own public key 565 so the ITR and the MITM generate a shared secret key among each 566 other. If the MITM is in the data path between the ITR and ETR, it 567 can use the shared secret key to decrypt traffic from the ITR. 569 Since LISP can secure Map-Replies by the authentication process 570 specified in [LISP-SEC], the ITR can detect when a MITM has signed a 571 Map-Reply for an EID-prefix it is not authoritative for. When an ITR 572 determines the signature verification fails, it discards and does not 573 reuse the key exchange parameters, avoids using the ETR for 574 encapsulation, and issues a severe log message to the network 575 administrator. Optionally, the ITR can send RLOC-probes to the 576 compromised RLOC to determine if can reach the authoritative ETR. 577 And when the ITR validates the signature of a Map-Reply, it can begin 578 encrypting and encapsulating packets to the RLOC of ETR. 580 13. IANA Considerations 582 This document describes a mechanism for encrypting LISP encapsulated 583 packets based on Diffie-Hellman key exchange procedures. During the 584 exchange the devices have to agree on a Cipher Suite used (i.e. the 585 cipher and hash functions used to encrypt/decrypt and to sign/verify 586 packets). The 8-bit Cipher Suite field is reserved for such purpose 587 in the security material section of the Map-Request and Map-Reply 588 messages. 590 This document requests IANA to create and maintain a new registry (as 591 outlined in [RFC5226]) entitled "LISP Crypto Cipher Suite". Initial 592 values for the registry are provided below. Future assignments are 593 to be made on a First Come First Served Basis. 595 +-----+--------------------------------------------+------------+ 596 |Value| Suite | Definition | 597 +-----+--------------------------------------------+------------+ 598 | 0 | Reserved | Section 6 | 599 +-----+--------------------------------------------+------------+ 600 | 1 | LISP_2048MODP_AES128_CBC_SHA256 | Section 6 | 601 +-----+--------------------------------------------+------------+ 602 | 2 | LISP_EC25519_AES128_CBC_SHA256 | Section 6 | 603 +-----+--------------------------------------------+------------+ 604 | 3 | LISP_2048MODP_AES128_GCM | Section 6 | 605 +-----+--------------------------------------------+------------+ 606 | 4 | LISP_3072MODP_AES128_GCM M-3072 | Section 6 | 607 +-----+--------------------------------------------+------------+ 608 | 5 | LISP_256_EC25519_AES128_GCM | Section 6 | 609 +-----+--------------------------------------------+------------+ 610 | 6 | LISP_256_EC25519_CHACHA20_POLY1305 | Section 6 | 611 +-----+--------------------------------------------+------------+ 613 LISP Crypto Cipher Suites 615 14. References 617 14.1. Normative References 619 [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 620 Address Format", draft-ietf-lisp-lcaf-13.txt (work in 621 progress). 623 [NIST-SP800-108] 624 "National Institute of Standards and Technology, 625 "Recommendation for Key Derivation Using Pseudorandom 626 Functions NIST SP800-108"", NIST SP 800-108, October 2009. 628 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 629 Requirement Levels", BCP 14, RFC 2119, 630 DOI 10.17487/RFC2119, March 1997, 631 . 633 [RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method", 634 RFC 2631, DOI 10.17487/RFC2631, June 1999, 635 . 637 [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) 638 Diffie-Hellman groups for Internet Key Exchange (IKE)", 639 RFC 3526, DOI 10.17487/RFC3526, May 2003, 640 . 642 [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. 643 Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites 644 for Transport Layer Security (TLS)", RFC 4492, 645 DOI 10.17487/RFC4492, May 2006, 646 . 648 [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated 649 Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, 650 . 652 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 653 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 654 DOI 10.17487/RFC5226, May 2008, 655 . 657 [RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic 658 Curve Cryptography Algorithms", RFC 6090, 659 DOI 10.17487/RFC6090, February 2011, 660 . 662 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 663 Locator/ID Separation Protocol (LISP)", RFC 6830, 664 DOI 10.17487/RFC6830, January 2013, 665 . 667 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 668 Morris, J., Hansen, M., and R. Smith, "Privacy 669 Considerations for Internet Protocols", RFC 6973, 670 DOI 10.17487/RFC6973, July 2013, 671 . 673 [RFC7539] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF 674 Protocols", RFC 7539, DOI 10.17487/RFC7539, May 2015, 675 . 677 14.2. Informative References 679 [AES-CBC] McGrew, D., Foley, J., and K. Paterson, "Authenticated 680 Encryption with AES-CBC and HMAC-SHA", draft-mcgrew-aead- 681 aes-cbc-hmac-sha2-05.txt (work in progress). 683 [CHACHA-POLY] 684 Langley, A., "ChaCha20 and Poly1305 based Cipher Suites 685 for TLS", draft-agl-tls-chacha20poly1305-04 (work in 686 progress). 688 [CURVE25519] 689 Bernstein, D., "Curve25519: new Diffie-Hellman speed 690 records", Publication 691 http://www.iacr.org/cryptodb/archive/2006/ 692 PKC/3351/3351.pdf. 694 [DH] "Diffie-Hellman key exchange", Wikipedia 695 http://en.wikipedia.org/wiki/Diffie-Hellman_key_exchange. 697 [LISP-DDT] 698 Fuller, V., Lewis, D., Ermaagan, V., and A. Jain, "LISP 699 Delegated Database Tree", draft-fuller-lisp-ddt-04 (work 700 in progress). 702 [LISP-SEC] 703 Maino, F., Ermagan, V., Cabellos, A., and D. Saucez, 704 "LISP-Secuirty (LISP-SEC)", draft-ietf-lisp-sec-10 (work 705 in progress). 707 Appendix A. Acknowledgments 709 The authors would like to thank Dan Harkins, Joel Halpern, Fabio 710 Maino, Ed Lopez, Roger Jorgensen, and Watson Ladd for their interest, 711 suggestions, and discussions about LISP data-plane security. An 712 individual thank you to LISP WG chair Luigi Iannone for shepherding 713 this document as well as contributing to the IANA Considerations 714 section. 716 The authors would like to give a special thank you to Ilari Liusvaara 717 for his extensive commentary and discussion. He has contributed his 718 security expertise to make lisp-crypto as secure as the state of the 719 art in cryptography. 721 In addition, the support and suggestions from the SAAG working group 722 were helpful and appreciative. 724 Appendix B. Document Change Log 726 [RFC Editor: Please delete this section on publication as RFC.] 728 B.1. Changes to draft-ietf-lisp-crypto-07.txt 730 o Posted September 2016. 732 o Addressed comments from Routing Directorate reviewer Danny 733 McPherson. 735 B.2. Changes to draft-ietf-lisp-crypto-06.txt 737 o Posted June 2016. 739 o Fixed IDnits errors. 741 B.3. Changes to draft-ietf-lisp-crypto-05.txt 743 o Posted June 2016. 745 o Update document which reflects comments Luigi provided as document 746 shepherd. 748 B.4. Changes to draft-ietf-lisp-crypto-04.txt 750 o Posted May 2016. 752 o Update document timer from expiration. 754 B.5. Changes to draft-ietf-lisp-crypto-03.txt 756 o Posted December 2015. 758 o Changed cipher suite allocations. We now have 2 AES-CBC cipher 759 suites for compatibility, 3 AES-GCM cipher suites that are faster 760 ciphers that include AE and a Chacha20-Poly1305 cipher suite which 761 is the fastest but not totally proven/accepted.. 763 o Remove 1024-bit DH keys for key exchange. 765 o Make clear that AES and chacha20 ciphers use AEAD so part of 766 encrytion/decryption does authentication. 768 o Make it more clear that separate key pairs are used in each 769 direction between xTRs. 771 o Indicate that the IV length is different per cipher suite. 773 o Use a counter based IV for every packet for AEAD ciphers. 774 Previously text said to use a random number. But CBC ciphers, use 775 a random number. 777 o Indicate that key material is sent in network byte order (big 778 endian). 780 o Remove A-bit from Security Type LCAF. No need to do 781 authentication only with the introduction of AEAD ciphers. These 782 ciphers can do authentication. So you get ciphertext for free. 784 o Remove language that refers to "encryption-key" and "integrity- 785 key". Used term "AEAD-key" that is used by the AEAD cipher suites 786 that do encryption and authenticaiton internal to the cipher. 788 B.6. Changes to draft-ietf-lisp-crypto-02.txt 790 o Posted September 2015. 792 o Add cipher suite for Elliptic Curve 25519 DH exchange. 794 o Add cipher suite for Chacha20/Poly1305 ciphers. 796 B.7. Changes to draft-ietf-lisp-crypto-01.txt 798 o Posted May 2015. 800 o Create cipher suites and encode them in the Security LCAF. 802 o Add IV to beginning of packet header and ICV to end of packet. 804 o AEAD procedures are now part of encrpytion process. 806 B.8. Changes to draft-ietf-lisp-crypto-00.txt 808 o Posted January 2015. 810 o Changing draft-farinacci-lisp-crypto-01 to draft-ietf-lisp-crypto- 811 00. This draft has become a working group document 813 o Add text to indicate the working group may work on a new data 814 encapsulation header format for data-plane encryption. 816 B.9. Changes to draft-farinacci-lisp-crypto-01.txt 818 o Posted July 2014. 820 o Add Group-ID to the encoding format of Key Material in a Security 821 Type LCAF and modify the IANA Considerations so this draft can use 822 key exchange parameters from the IANA registry. 824 o Indicate that the R-bit in the Security Type LCAF is not used by 825 lisp-crypto. 827 o Add text to indicate that ETRs/RTRs can negotiate less number of 828 keys from which the ITR/PITR sent in a Map-Request. 830 o Add text explaining how LISP-SEC solves the problem when a man-in- 831 the-middle becomes part of the Map-Request/Map-Reply key exchange 832 process. 834 o Add text indicating that when RLOC-probing is used for RLOC 835 reachability purposes and rekeying is not desired, that the same 836 key exchange parameters should be used so a reallocation of a 837 pubic key does not happen at the ETR. 839 o Add text to indicate that ECDH can be used to reduce CPU 840 requirements for computing shared secret-keys. 842 B.10. Changes to draft-farinacci-lisp-crypto-00.txt 844 o Initial draft posted February 2014. 846 Authors' Addresses 848 Dino Farinacci 849 lispers.net 850 San Jose, California 95120 851 USA 853 Phone: 408-718-2001 854 Email: farinacci@gmail.com 856 Brian Weis 857 cisco Systems 858 170 West Tasman Drive 859 San Jose, California 95124-1706 860 USA 862 Phone: 408-526-4796 863 Email: bew@cisco.com