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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Missing Reference: 'IEEE802154' is mentioned on line 439, but not defined ** Obsolete normative reference: RFC 6253 (Obsoleted by RFC 8002) == Outdated reference: A later version (-05) exists of draft-moskowitz-hip-dex-02 Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Ohba, Ed. 3 Internet-Draft Toshiba 4 Intended status: Experimental January 21, 2015 5 Expires: July 25, 2015 7 An Extension to Mesh Link Establishment (MLE) for Host Identity Protocol 8 Diet Exchange (HIP DEX) 9 draft-ohba-mle-hip-dex-00 11 Abstract 13 This document defines an extension of MLE (Mesh Link Establishment) 14 protocol to encapsulate HIP DEX key exchange protocol messages. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on July 25, 2015. 33 Copyright Notice 35 Copyright (c) 2015 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 1.1. Requirement Language . . . . . . . . . . . . . . . . . . 3 52 1.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 53 1.3. Convention . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. Key Establishment Phase . . . . . . . . . . . . . . . . . . . 4 56 4. Key Update Phase . . . . . . . . . . . . . . . . . . . . . . 6 57 5. Key Materials . . . . . . . . . . . . . . . . . . . . . . . . 7 58 5.1. Pair-wise Key . . . . . . . . . . . . . . . . . . . . . . 7 59 5.2. Group Keys . . . . . . . . . . . . . . . . . . . . . . . 7 60 6. MLE Security . . . . . . . . . . . . . . . . . . . . . . . . 7 61 7. Certificate Revocation . . . . . . . . . . . . . . . . . . . 8 62 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 63 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 64 9.1. MLE TLV Types . . . . . . . . . . . . . . . . . . . . . . 9 65 9.2. HIP Parameter . . . . . . . . . . . . . . . . . . . . . . 9 66 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 67 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 68 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 69 11.2. External Informative References . . . . . . . . . . . . 10 70 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 72 1. Introduction 74 HIP DEX (Host Identity Protocol Diet EXchange) 75 [I-D.moskowitz-hip-dex] is a light-weight key exchange protocol 76 designed for constrained devices. HIP DEX builds on the HIP Base 77 EXchange (HIP BEX) [I-D.ietf-hip-rfc5201-bis] and inherits the 78 transport-agnostic property of HIP BEX. 80 MLE (Mesh Link Establishment) 81 [I-D.kelsey-intarea-mesh-link-establishment] is defined for 82 establishing and configuring secure links in IEEE 802.15.4 mesh 83 networks. MLE assumes that shared keys to secure link-layer frames 84 and MLE messages exchanged between a pair of nodes are pre-configured 85 between the nodes. Therefore, a key exchange protocol is required in 86 order to dynamically configure the required shared keys. While such 87 a key exchange protocol can be run outside MLE, sequentially running 88 a key exchange protocol and MLE as separate protocols requires more 89 message roundtrips. For example, running a HIP DEX 4-way handshake 90 followed by an MLE 3-way handshake requires 3.5 message roundtrips. 92 In this document, an extension to the MLE protocol for encapsulating 93 HIP DEX messages is defined in order to realize optimized key 94 exchange and link establishment for IEEE 802.15.4 mesh networks. 96 1.1. Requirement Language 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 100 "OPTIONAL" in this document are to be interpreted as described in 101 [RFC2119]. 103 1.2. Acronyms 105 DEX-I1, DEX-R1, DEX-I2, DEX-R2: HIP DEX I1, R1, I2, R2 messages 107 ECDH: Elliptic Curve Diffie-Hellman 109 EI: HIP DEX Key Establishment Initiator 111 ER: HIP DEX Key Establishment Responder 113 LLFC: Link-Layer Frame Counter 115 MIC: MLE Message Integrity Code 117 MLFC: MLE Frame Counter 119 UI: HIP DEX Key Update Initiator 121 UR: HIP DEX Key Update Responder 123 1.3. Convention 125 In the figures of this document, MLE messages marked with '*' are 126 those secured by the MLE protocol. 128 In the key material formats in this document, '|' denotes 129 concatenation operator. 131 2. Overview 133 MLE over HIP DEX consists of two phases, i.e., Key Establishment 134 Phase and Key Update Phase. In Key Establishment Phase, a HIP DEX 135 4-way handshake using I1, R1, I2 and R2 messages is conducted to 136 establish a secure channel between an EI and an ER based on an ECDH 137 shared secret and exchange session key materials over the secure 138 channel. 140 In Key Update Phase, HIP DEX Update messages encrypting session key 141 materials are exchanged between a UI and each UR using an MLE Update 142 Request and Update exchange, followed by a multicast MLE Update 143 message for triggering each UR to simultaneously activate new key 144 materials and reset the associated link-layer frame counters. The UI 145 and UR roles for a pair of nodes may be determined independently of 146 the EI and ER roles that have been taken by the nodes. 148 All MLE messages used for the extension defined in this document 149 SHOULD NOT be protected by link-layer so that a key exchange can be 150 done regardless of the security state of the link-layer. A node that 151 implements this specification MUST allow sending and receiving MLE 152 messages not secured by the link-layer. 154 Secured 802.15.4 MAC frames and MLE messages that use keys 155 established via HIP DEX MUST use a 5-octet Frame Counter so that the 156 Frame Counter does not reach its maximum value throughout the 157 lifetime of a node. 159 Other than the rules described in this document, the rules defined in 160 [I-D.kelsey-intarea-mesh-link-establishment] are preserved. 162 3. Key Establishment Phase 164 A message exchange diagram for Key Establishment Phase is shown in 165 Figure 1. 167 (EI) (ER) 168 --> Advertisement [HIP{DEX-I1}, Link Quality] 170 <-- Advertisement [HIP{DEX-R1}, Link Quality] 172 --> Link Request [HIP{DEX-I2}, Source Address, Mode, 173 Timeout, Challenge]* 175 <-- Link Accept and Request 176 [HIP{DEX-R2}, LLFC, MLFC, Source Address, Mode, 177 Timeout, Response, Challenge]* 179 --> Link Accept [LLFC, MLFC, Response]* 181 Figure 1: Key Establishment Phase 183 An EI sends an MLE Advertisement message containing a HIP TLV and a 184 Link Quality TLV to an ER. The HIP TLV carries a DEX-I1 packet. How 185 an EI discovers an ER is outside the scope of this document. 187 The ER receives the MLE Advertisement message containing a DEX-I1 188 packet from the EI and sends an MLE Advertisement message containing 189 a HIP TLV and a Link Quality TLV to the EI. The HIP TLV carries a 190 DEX-R1 packet. The DEX-R1 packet MUST contain mandatory R1 191 parameters specified in [I-D.moskowitz-hip-dex]. The DEX-R1 packet 192 MAY contain optional R1 parameters specified in 193 [I-D.moskowitz-hip-dex] and a CERT parameter defined in [RFC6253]. 195 The EI receives the MLE Advertisement message from the ER and sends a 196 secured MLE Link Request message containing HIP, Source Address, 197 Mode, Timeout and Challenge TLVs to the ER. The HIP TLV carries a 198 DEX-I2 packet. The DEX-I2 packet MUST contain mandatory I2 199 parameters specified in [I-D.moskowitz-hip-dex] including an 200 ENCRYPTED_KEY parameter wrapping a session key material of the EI. 201 The DEX-I2 packet MUST also contain an ENCRYPTED parameter wrapping 202 group key materials of the EI. The DEX-I2 packet MAY contain 203 optional I2 parameters specified in [I-D.moskowitz-hip-dex] and a 204 CERT parameter defined in [RFC6253]. The MLE Link Request message is 205 protected by the EI's group MLE key (see section Section 5.2) derived 206 from the EI's group key materials. 208 The ER receives the MLE Link Request message from the EI and extracts 209 the EI's session key material wrapped in the ENCRYPTED_KEY parameter 210 and the EI's group key materials wrapped in the ENCRYPTED parameter. 211 Then the ER sends a secured MLE Link Accept and Request message 212 containing HIP, LLFC, MLFC, Source Address, Mode Timeout, Response 213 and Challenge TLVs to the EI. The HIP TLV carries a DEX-R2 packet. 214 The DEX-R2 packet MUST contain R2 parameters specified in 215 [I-D.moskowitz-hip-dex] including an ENCRYPTED_KEY parameter wrapping 216 a session key material of the ER. The DEX-R2 packet MUST also 217 contain an ENCRYPTED parameter wrapping group key materials of the 218 ER. The DEX-R2 packet MAY contain optional R2 parameters specified 219 in [I-D.moskowitz-hip-dex]. Note that the MIC field of the MLE Link 220 Request message is verified after the ER successfully extracts the 221 EI's group key materials. 223 The EI receives the MLE Link Accept and Request message from the ER 224 and extracts the ER's session key material wrapped in the 225 ENCRYPTED_KEY parameter and the ER's group key materials wrapped in 226 the ENCRYPTED parameter. Then the EI sends a secured MLE Link Accept 227 message containing LLFC TLV, MLFC and Response TLVs to the ER. If a 228 pair-wise key is used by the link-layer, the EI also creates a Pair- 229 wise Key SA with the session key generated by the pair of session key 230 materials of the EI and ER as specified in [I-D.moskowitz-hip-dex]. 231 Note that the MIC field of the MLE Link Accept and Request message is 232 verified after the EI successfully extracts the ER's group key 233 materials. 235 The ER receives the MLE Link Accept message from the EI. If a pair- 236 wise key is used by the link-layer, the EI creates a Pair-wise Key SA 237 with the session key generated by the pair of session key materials 238 of the EI and ER as specified in [I-D.moskowitz-hip-dex]. 240 4. Key Update Phase 242 In Key Update Phase, group key materials are updated. 244 Since the 5-octet Frame Counter space is large enough considering the 245 maximum bandwidth of 250Kbps in 802.15.4 [IEEE802154] to make an 246 assumption that a Frame Counter does not reach its maximum value 247 throughout the lifetime of a node, a mechanism for updating a pair- 248 wise key is not defined in this document. 250 Updating a group key may happen when a node that shares the group key 251 is revoked. A message exchange diagram for group key update is shown 252 in Figure 2. 254 (UI) (UR1)..(URn) 255 // Update 1st peer 256 ----> Update Request [HIP{DEX-UPDATE}, MLFC, Source Address]* 257 <---- Update [HIP{DEX-UPDATE}, MLFC, Source Address]* 258 .. .. 260 // Update n-th peer 261 -----------> Update Request [HIP{DEX-UPDATE}, MLFC, Source Address]* 262 <----------- Update [HIP{DEX-UPDATE}, MLFC, Source Address]* 264 // Key switch notification (multicast) 265 ----> .. --> Update [LLFC, MLFC]* 267 Figure 2: Group Key Update 269 First, a UI performs the following exchange for each UR: 271 o The UI sends an MLE Update Request message containing HIP, MLFC, 272 Source Address and MIC TLVs to a UR. The HIP TLV carries a DEX- 273 UPDATE packet containing SEC, MAC and ENCRYPTED parameters. The 274 ENCRYPTED parameter wraps new group key materials of the UI. 276 o The UR receives the MLE Update Request message from the UI, 277 extracts UI's new group key materials from the ENCRYPTED 278 parameter, and sends an MLE Update message containing HIP, MLFC 279 and Source Address TLVs, where the HIP TLV carries a DEX-UPDATE 280 packet containing ACK and MAC parameters. 282 Once MLE Update Request and Update exchange is completed for all URs, 283 the UI activates the UI's new group key materials by multicasting an 284 MLE Update message containing LLFC and MLFC TLVs. The MLE Update 285 message is protected by the UI's group MLE key (see section 286 Section 5.2) derived from the UI's new group key materials. 288 Each UR receives the multicast MLE Update message. If the received 289 message is valid, UR activates the UI's new group key material. 291 5. Key Materials 293 5.1. Pair-wise Key 295 The first 16 octets of the session key corresponding to the HIP DEX 296 Pair-wise SA [I-D.moskowitz-hip-dex] is used as the pairwise link- 297 layer key used for securing unicast link-layer frames with Key 298 Identifier Mode 0x00. 300 An encrypted session key material is contained in an ENCRYPTED_KEY 301 parameter of HIP when the session key is distributed during Key 302 Establishment Phase. 304 5.2. Group Keys 306 Group key materials are created by a node and distributed to peer 307 nodes. 309 The group key materials consist of a 1-octet key identifier (KeyId), 310 a 16-octet group link-layer key (GroupL2Key), and a 16-octet group 311 MLE key (GroupMLEKey), and encoded as follows: 313 Group Key Materials = KeyId | GroupL2Key | GroupMLEKey 315 A GroupL2Key is used for securing link-layer frames with Key 316 Identifier Mode 0x03 sent by the node that created the group key 317 material. GroupL2Key MUST be used for securing broadcast link-layer 318 frames and MAY also be used for securing unicast link-layer frames. 320 A GroupMLEKey MUST be used for securing MLE messages with Key 321 Identifier Mode 0x03 sent by the node that created the group key 322 material. 324 The group key materials are contained in an 325 MLE_AND_L2_GROUP_KEY_MATERIALS parameter of HIP, where the 326 MLE_AND_L2_GROUP_KEY_MATERIALS parameter MUST be encrypted in an 327 ENCRYPTED parameter of HIP. 329 6. MLE Security 331 As described in [I-D.kelsey-intarea-mesh-link-establishment], MLE 332 security reuses that of IEEE 802.15.4, i.e., AES-CCM* [IEEE802154]. 333 Since some of the MLE messages (i.e., MLE Link Accept and Request and 334 MLE Accept messages carrying DEX-I2 and DEX-R2 packets, respectively, 335 and unicast MLE Update Request and Update messages carrying a DEX- 336 UPDATE packet) require to be sent unencrypted and only authentication 337 is needed, MIC-64 (Security Level 2) or MIC-128 (Security Level 3) is 338 used to secure MLE messages. MIC-64 is the default security level 339 for securing MLE messages used in this document. GroupMLEKey (see 340 section Section 5.2) with Key Identifier Mode 0x03 and a 5-octet 341 Frame Counter MUST be used for any secured MLE message. 343 7. Certificate Revocation 345 Any MLE message used in this document MAY also contain a CRL 346 (Certificate Revocation List) TLV in which CertificateList defined in 347 [RFC5280] is encoded in the Value field. A node that receives a 348 valid MLE message containing a CRL TLV revokes certificates specified 349 in the TLV and deletes all pair-wise and group keys associated with 350 the revoked certificates. 352 8. Security Considerations 354 The MLE extension defined in this document uses HIP DEX for key 355 management of computation or memory constrained sensor/actuator 356 devices, and thus it inherits all security considerations made for 357 HIP DEX [I-D.moskowitz-hip-dex]. 359 In order to mitigate security weakness caused by lack of Perfect 360 Forward Secrecy (PFS) in HIP DEX, it is RECOMMENDED to use this MLE 361 extension in conjunction with an additional mechanism to update 362 public/private key pairs and renew HIP DEX SAs using new public/ 363 private key pairs whenever necessary. 365 In both Key Establishment Phase and Key Update Phase, MLE messages 366 are secured using a group key instead of a pairwise key in order to 367 optimize message roundtrips since a group key establishment requires 368 only a half roundtrip. As a result, a Denial of Service (DoS) attack 369 from an insider sharing the group key is possible over MLE TLVs. 371 Due to integration of HIP DEX into MLE, secured MLE messages are 372 authenticated but not encrypted because decryption can be done only 373 after establishing a key. As a result, Source Address, Mode, 374 Timeout, Challenge, Response LLFC and MLFC TLVs are sent in clear, 375 and the cleartext information may be used by attackers for the DoS 376 attack described above. Note that authentication of the MLE message 377 carrying a DEX-I2, DEX-R2 or DEX-UPDATE packet is possible by 378 validating MIC of the MLE message after extracting the authentication 379 key (i.e., GroupMLEKey) from the HIP DEX packet. 381 9. IANA Considerations 383 9.1. MLE TLV Types 385 The following MLE TLV types are to be assigned by IANA based on the 386 policy described in [I-D.kelsey-intarea-mesh-link-establishment]: 388 o HIP-DEX (Value: 9, Length: Variable, Meaning: HIP DEX packet, 389 Reference: this document). 391 o CRL (Value: 10, Length: Variable, Meaning: Certificate Revocation 392 List, Reference: this document). 394 9.2. HIP Parameter 396 The following HIP Parameter is assigned based on the policy described 397 in [I-D.ietf-hip-rfc5201-bis]: 399 o MLE_AND_L2_GROUP_KEY_MATERIALS, (Value: 65530, Length: 33, 400 Meaning: Group key materials for MLE and link-layer, Reference: 401 this document). 403 10. Acknowledgments 405 TBD. 407 11. References 409 11.1. Normative References 411 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 412 Requirement Levels", BCP 14, RFC 2119, March 1997. 414 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 415 Housley, R., and W. Polk, "Internet X.509 Public Key 416 Infrastructure Certificate and Certificate Revocation List 417 (CRL) Profile", RFC 5280, May 2008. 419 [RFC6253] Heer, T. and S. Varjonen, "Host Identity Protocol 420 Certificates", RFC 6253, May 2011. 422 [I-D.moskowitz-hip-dex] 423 Moskowitz, R. and R. Hummen, "HIP Diet EXchange (DEX)", 424 draft-moskowitz-hip-dex-02 (work in progress), December 425 2014. 427 [I-D.ietf-hip-rfc5201-bis] 428 Moskowitz, R., Heer, T., Jokela, P., and T. Henderson, 429 "Host Identity Protocol Version 2 (HIPv2)", draft-ietf- 430 hip-rfc5201-bis-20 (work in progress), October 2014. 432 [I-D.kelsey-intarea-mesh-link-establishment] 433 Kelsey, R., "Mesh Link Establishment", draft-kelsey- 434 intarea-mesh-link-establishment-06 (work in progress), May 435 2014. 437 11.2. External Informative References 439 [IEEE802154] 440 IEEE standard for Information Technology, "IEEE std. 441 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 442 and Physical Layer (PHY) Specifications for Low-Rate 443 Wireless Personal Area Networks", June 2011. 445 Author's Address 447 Yoshihiro Ohba (editor) 448 Toshiba Corporate Research and Development Center 449 1 Komukai-Toshiba-cho 450 Saiwai-ku, Kawasaki, Kanagawa 212-8582 451 Japan 453 Phone: +81 44 549 2127 454 Email: yoshihiro.ohba@toshiba.co.jp