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Wing 7 Citrix 8 June 18, 2020 10 Integrity Protection for the Network Service Header (NSH) and Encryption 11 of Sensitive Context Headers 12 draft-ietf-sfc-nsh-integrity-00 14 Abstract 16 This specification adds integrity protection and optional encryption 17 of sensitive metadata directly to the Network Service Header (NSH) 18 used for Service Function Chaining (SFC). 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on December 20, 2020. 37 Copyright Notice 39 Copyright (c) 2020 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 56 3. Assumptions and Basic Requirements . . . . . . . . . . . . . 4 57 4. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6 58 4.1. Supported Security Services . . . . . . . . . . . . . . . 6 59 4.1.1. Encrypt All or a Subset of Context Headers . . . . . 6 60 4.1.2. Integrity Protection . . . . . . . . . . . . . . . . 7 61 4.2. One Secret Key, Two Security Services . . . . . . . . . . 9 62 4.3. Mandatory-to-Implement Authenticated Encryption and HMAC 63 Algorithms . . . . . . . . . . . . . . . . . . . . . . . 10 64 4.4. Key Management . . . . . . . . . . . . . . . . . . . . . 10 65 4.5. New NSH Variable-Length Context Headers . . . . . . . . . 11 66 4.6. Encapsulation of NSH within NSH . . . . . . . . . . . . . 11 67 5. New NSH Variable-Length Context Headers . . . . . . . . . . . 12 68 5.1. MAC#1 Context Header . . . . . . . . . . . . . . . . . . 13 69 5.2. MAC#2 Context Header . . . . . . . . . . . . . . . . . . 15 70 6. Timestamp Format . . . . . . . . . . . . . . . . . . . . . . 17 71 7. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 18 72 7.1. Generic Behavior . . . . . . . . . . . . . . . . . . . . 18 73 7.2. MAC NSH Data Generation . . . . . . . . . . . . . . . . . 19 74 7.3. Encrypted NSH Metadata Generation . . . . . . . . . . . . 20 75 7.4. Timestamp for Replay Attack . . . . . . . . . . . . . . . 21 76 7.5. NSH Data Validation . . . . . . . . . . . . . . . . . . . 22 77 7.6. Decryption of NSH Metadata . . . . . . . . . . . . . . . 22 78 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 79 8.1. MAC#1 . . . . . . . . . . . . . . . . . . . . . . . . . . 23 80 8.2. MAC#2 . . . . . . . . . . . . . . . . . . . . . . . . . . 24 81 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 82 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24 83 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 84 11.1. Normative References . . . . . . . . . . . . . . . . . . 24 85 11.2. Informative References . . . . . . . . . . . . . . . . . 25 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 88 1. Introduction 90 Many advanced Service Functions (SFs) are invoked for the delivery of 91 value-added services. Typically, SFs are used to meet various 92 service objectives such as IP address sharing, avoiding covert 93 channels, detecting Denial-of-Service (DoS) attacks and protecting 94 network infrastructures against them, network slicing, etc. Because 95 of the proliferation of such advanced SFs together with complex 96 service deployment constraints that demand more agile service 97 delivery procedures, operators need to rationalize their service 98 delivery logics and master their complexity while optimising service 99 activation time cycles. The overall problem space is described in 100 [RFC7498]. 102 [RFC7665] presents a data plane architecture addressing the 103 problematic aspects of existing service deployments, including 104 topological dependence and configuration complexity. It also 105 describes an architecture for the specification, creation, and 106 maintenance of Service Function Chains (SFCs) within a network. That 107 is, how to define an ordered set of SFs and ordering constraints that 108 must be applied to packets/flows selected as a result of traffic 109 classification. [RFC8300] specifies the SFC encapsulation: Network 110 Service Header (NSH). 112 The NSH data is unauthenticated and unencrypted [RFC8300], forcing a 113 service topology that requires security and privacy to use a 114 transport encapsulation that supports such features. Note that some 115 transport encapsulation (e.g., IPsec) only provide hop-by-hop 116 security between two SFC data plane elements (e.g., two Service 117 Function Forwarders (SFFs), SFF to SF) and do not provide SF-to-SF 118 security of NSH metadata. For example, if IPsec is used, SFFs or SFs 119 within a Service Function Path (SFP) not authorized to access the 120 privacy-sensitive metadata will have access to the metadata. As a 121 reminder, the metadata referred to is an information that is inserted 122 by Classifiers or intermediate SFs and shared with downstream SFs; 123 such information is not visible to the communication endpoints 124 (Section 4.9 of [RFC7665]). 126 The lack of such capability was reported during the development of 127 [RFC8300] and [RFC8459]. The reader may refer to Section 3.2.1 of 128 [I-D.arkko-farrell-arch-model-t] for a discussion on the need for 129 more awareness about attacks from within closed domains. 131 This specification fills that gap. Concretely, this document adds 132 integrity protection and optional encryption of sensitive metadata 133 directly to the NSH (Section 4); integrity protects the packet 134 payload, and provides replay protection (Section 7.4). Thus, the NSH 135 does not have to rely upon an underlying transport encapsulation for 136 security and confidentiality. 138 This specification introduces new Variable-Length Context Headers to 139 carry fields necessary for integrity protected NSH headers and 140 encrypted Context Headers (Section 5), and is therefore only 141 applicable to NSH MD Type 0x02 (Section 2.5 of [RFC8300]). 143 This specification limits thus access to an information within an SFP 144 to entities that have a need to interpret it. Particularly, SFFs 145 should not act or process the Context Headers. 147 2. Terminology 149 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 150 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 151 "OPTIONAL" in this document are to be interpreted as described in BCP 152 14 [RFC2119][RFC8174] when, and only when, they appear in all 153 capitals, as shown here. 155 This document makes use of the terms defined in [RFC7665] and 156 [RFC8300]. 158 The document defines the following terms: 160 o SFC data plane element: Refers to SFC-aware SF, SFF, SFC Proxy, or 161 Classifier as defined in the SFC data plane architecture [RFC7665] 162 and further refined in [RFC8300]. 164 o SFC control element: A logical entity that instructs one or more 165 SFC data plane elements on how to process NSH packets within an 166 SFC-enabled domain. 168 o Key Identifier: A key identifier used to identify and deliver keys 169 to authorized entities. See for example, 'kid' usage in 170 [RFC7635]. 172 o NSH data: The NSH is composed of a Base Header, a Service Path 173 Header, and optional Context Headers. NSH data refers to all the 174 above headers and the packet or frame on which the NSH is imposed 175 to realize an SFP. 177 o NSH imposer: Refers to the SFC data plane element that is entitled 178 to impose the NSH with the Context Headers defined in this 179 document. 181 3. Assumptions and Basic Requirements 183 Section 2 of [RFC8300] specifies that the NSH data can be spread over 184 three headers: 186 o Base Header: Provides information about the service header and the 187 payload protocol. 189 o Service Path Header: Provides path identification and location 190 within an SFP. 192 o Context Header(s): Carries metadata (i.e., context data) along a 193 service path. 195 The NSH allows to share context information (a.k.a., metadata) with 196 downstream SFC-aware data elements on a per SFC/SFP basis. To that 197 aim: 199 The control plane is used to instruct the Classifier about the set 200 of context information to be supplied for a given service function 201 chain. 203 The control plane is also used to instruct an SFC-aware SF about 204 any metadata it needs to attach to packets for a given service 205 function chain. This instruction may occur any time during the 206 validity lifetime of an SFC/SFP. The control plane may indicate, 207 for a given service function chain, an order for consuming a set 208 of contexts supplied in a packet. 210 An SFC-aware SF can also be instructed about the behavior it 211 should adopt after consuming a context information that was 212 supplied in the NSH. For example, the context can be maintained, 213 updated, or stripped. 215 An SFC Proxy may be instructed about the behavior it should adopt 216 to process the context information that was supplied in the NSH on 217 behalf of an SFC-unaware SF (e.g., the context can be maintained 218 or stripped). The SFC Proxy may also be instructed to add some 219 new context information into the NSH on behalf of an SFC-unaware 220 SF. 222 In reference to Figure 1, 224 o Classifiers, SFC-aware SFs, and SFC proxies are entitled to update 225 the Context Header(s). 227 o Only SFC-aware SFs and SFC proxies are entitled to update the 228 Service Path Header. 230 o SFFs are entitled to modify the Base Path header (TTL value, for 231 example). Nevertheless, SFFs are not supposed to act on the 232 Context Headers or look into the content of the Context Headers. 234 Thus, the following requirements: 236 o Only Classifiers, SFC-aware SFs, and SFC proxies MUST be able to 237 encrypt and decrypt a given Context Header. 239 o Both encrypted and unecrypted Context Headers MAY be included in 240 the same NSH. That is, some Context Headers (TLVs) may be 241 protected while others do not. 243 o The solution MUST provide integrity protection for the Service 244 Path Header. 246 o The solution MAY provide integrity protection for the Base Header. 247 The implications of disabling such checks are discussed in 248 Section 8.1. 250 +----------------+-----------------------------+-------------------+ 251 | | Insert, remove, or replace | Update the NSH | 252 | | the NSH | | 253 | | | | 254 | SFC Data Plane +---------+---------+---------+---------+---------+ 255 | Element | | | |Decrement| Update | 256 | | Insert | Remove | Replace | Service | Context | 257 | | | | | Index |Header(s)| 258 +================+=========+=========+=========+=========+=========+ 259 | | + | | + | | + | 260 | Classifier | | | | | | 261 +----------------+---------+---------+---------+---------+---------+ 262 |Service Function| | + | | | | 263 |Forwarder (SFF) | | | | | | 264 +----------------+---------+---------+---------+---------+---------+ 265 |Service Function| | | | + | + | 266 | (SF) | | | | | | 267 +----------------+---------+---------+---------+---------+---------+ 268 | | + | + | | + | + | 269 | SFC Proxy | | | | | | 270 +----------------+---------+---------+---------+---------+---------+ 272 Figure 1: Summary of NSH Actions 274 4. Design Overview 276 4.1. Supported Security Services 278 This specification provides the functions described in the following 279 subsections: 281 4.1.1. Encrypt All or a Subset of Context Headers 283 The solution allows to encrypt all or a subset of NSH Context Headers 284 by Classifiers, SFC-aware SFs, and SFC proxies. 286 As depicted in Table 1, SFFs are not involved in data encryption. 287 This document enforces this design approach by encrypting Context 288 Headers with keys that are not supplied to SFFs, thus enforcing this 289 limitation by protocol (rather than requirements language). 291 +-----------------+------------------------------+------------------+ 292 | Data Plane | Base and Service Headers | Metadata | 293 | Element | Encryption | Encryption | 294 +-----------------+------------------------------+------------------+ 295 | Classifier | No | Yes | 296 | SFF | No | No | 297 | SFC-aware SF | No | Yes | 298 | SFC Proxy | No | Yes | 299 | SFC-unaware SF | No | No | 300 +-----------------+------------------------------+------------------+ 302 Table 1: Encryption Function Supported by SFC Data Plane Elements 304 The SFC control plane is assumed to instruct the Classifier(s), SFC- 305 aware SFs, and SFC proxies with the set of Context Headers (privacy- 306 sensitive metadata, typically) that must be encrypted. Encryption 307 keying material is only provided to these SFC data elements. 309 The control plane may also indicate the set of SFC data plane 310 elements that are entitled to supply a given context header (e.g., in 311 reference to their identifiers as assigned within the SFC-enabled 312 domain). It is out of the scope of this document to elaborate on how 313 such instructions are provided to the appropriate SFC data plane 314 elements, nor to detail the structure used to store the instructions. 316 The Service Path Header (Section 2 of [RFC8300]) is not encrypted 317 because SFFs use Service Index (SI) in conjunction with Service Path 318 Identifier (SPI) for determining the next SF in the path. 320 4.1.2. Integrity Protection 322 The solution provides integrity protection for the NSH data. Two 323 levels of assurance (LoAs) are supported. 325 A first level of assurance where all NSH data except the Base Header 326 are integrity protected (Figure 2). In this case, the NSH imposer 327 may be a Classifier, an SFC-aware SF, or an SFC Proxy. SFFs are not 328 thus provided with authentication material. Further details are 329 discussed in Section 5.1. 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 332 | Transport Encapsulation | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+... 334 | Base Header | | 335 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N 336 | | Service Path Header | S 337 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ H 338 | | Context Header(s) | | 339 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+... 340 | | Original Packet | 341 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 | 343 +------Scope of integrity protected data 345 Figure 2: First Level of Assurance 347 A second level of assurance where all NSH data, including the Base 348 Header, are integrity protected (Figure 3). In this case, the NSH 349 imposer may be a Classifier, an SFC-aware SF, an SFF, or an SFC 350 Proxy. Further details are provided in Section 5.2. 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 | Transport Encapsulation | 354 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+... 355 | | Base Header | | 356 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N 357 | | Service Path Header | S 358 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ H 359 | | Context Header(s) | | 360 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+... 361 | | Original Packet | 362 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | 364 +----Scope of integrity protected data 366 Figure 3: Second Level of Assurance 368 The integrity protection scope is explicitly signaled to SFC-aware 369 SFs and SFC proxies in the NSH by means of a dedicated MD Type 370 (Section 5). 372 In both levels of assurance, the unencrypted Context Headers and the 373 packet on which the NSH is imposed are subject to integrity 374 protection. 376 Table 2 lists the roles of SFC data plane elements in providing 377 integrity protection for the NSH. 379 +--------------------+----------------------------------+ 380 | Data Plane Element | Integrity Protection | 381 +--------------------+----------------------------------+ 382 | Classifier | Yes | 383 | SFF | No (first LoA); Yes (second LoA) | 384 | SFC-aware SF | Yes | 385 | SFC Proxy | Yes | 386 | SFC-unaware SF | No | 387 +--------------------+----------------------------------+ 389 Table 2: Integrity Protection Supported by SFC Data Plane Elements 391 4.2. One Secret Key, Two Security Services 393 The authenticated encryption algorithm defined in [RFC7518] is used 394 to provide NSH data integrity and to encrypt the Context Headers that 395 carry privacy-sensitive metadata. 397 The authenticated encryption algorithm provides a unified encryption 398 and authentication operation which turns plaintext into authenticated 399 ciphertext and vice versa. The generation of secondary keys MAC_KEY 400 and ENC_KEY from the secret key (K) is discussed in Section 5.2.2.1 401 of [RFC7518]: 403 o The ENC_KEY is used for encrypting the Context Headers and the 404 message integrity of the NSH data is calculated using the MAC_KEY. 406 o If the Context Headers are not encrypted, the Hashed Message 407 Authentication Mode (HMAC) algorithm discussed in [RFC4868] is 408 used to integrity protect the NSH data. 410 The advantage of using the authenticated encryption algorithm is that 411 SFC-aware SFs and SFC proxies only need to re-compute the message 412 integrity of the NSH data after decrementing the Service Index (SI) 413 and do not have to re-compute the ciphertext. The other advantage is 414 that SFFs do not have access to the ENC_KEY and cannot act on the 415 encrypted Context Headers and, only in case of the second level of 416 assurance, SFFs do have access to the MAC_KEY. Similarly, an SFC- 417 aware SF or SFC Proxy not allowed to decrypt the Context Headers will 418 not have access to the ENC_KEY. 420 The authenticated encryption algorithm or HMAC algorithm to be used 421 by SFC data plane elements is typically controlled using the SFC 422 control plane. Mandatory to implement authenticated encryption and 423 HMAC algorithms are listed in Section 4.3. 425 The authenticated encryption process takes as input four octet 426 strings: a secret key (K), a plaintext (P), Additional Authenticated 427 Data (A) (which contains the data to be authenticated, but not 428 encrypted), and an Initialization Vector (IV). The ciphertext value 429 (E) and the Authentication Tag value (T) are provided as outputs. 431 In order to decrypt and verify, the cipher takes as input K, IV, A, 432 T, and E. The output is either the plaintext or an error indicating 433 that the decryption failed as described in Section 5.2.2.2 of 434 [RFC7518]. 436 4.3. Mandatory-to-Implement Authenticated Encryption and HMAC 437 Algorithms 439 Classifiers, SFC-aware SFs, and SFC proxies MUST implement the 440 AES_128_CBC_HMAC_SHA_256 algorithm and SHOULD implement the 441 AES_192_CBC_HMAC_SHA_384 and AES_256_CBC_HMAC_SHA_512 algorithms. 443 Classifiers, SFC-aware SFs, and SFC proxies MUST implement the HMAC- 444 SHA-256-128 algorithm and SHOULD implement the HMAC-SHA-384-192 and 445 HMAC-SHA-512-256 algorithms. 447 SFFs MAY implement the aforementioned cipher suites and HMAC 448 algorithms. 450 o Note: The use of AES-GCM + HMAC may have CPU and packet size 451 implications (need for a second 128-bit authentication tag). 453 4.4. Key Management 455 The procedure for the allocation/provisioning of secret keys (K) and 456 authenticated encryption algorithm or MAC_KEY and HMAC algorithm is 457 outside the scope of this specification. As such, this specification 458 does not mandate the support of any specific mechanism. 460 The documents does not assume nor preclude the following: 462 o The same keying material is used for all the service functions 463 used within an SFC-enabled domain. 465 o Distinct keying material is used per SFP by all involved SFC data 466 path elements. 468 o Per-tenant keys are used. 470 In order to accommodate deployments relying upon keying material per 471 SFC/SFP and also the need to update keys after encrypting NSH data 472 for certain amount of time, this document uses key identifier (kid) 473 to unambiguously identify the appropriate keying material. Doing so 474 allows to address the problem of synchronization of keying material. 476 Additional information on manual vs. automated key management and 477 when one should be used over the other can be found in [RFC4107]. 479 4.5. New NSH Variable-Length Context Headers 481 New NSH Variable-Length Context Headers are defined in Section 5 for 482 NSH data integrity protection and, optionally, encryption of Context 483 Headers carrying privacy-sensitive metadata. Concretely, an NSH 484 imposer includes (1) the key identifier to identify the keying 485 material, (2) the timestamp to protect against replay attacks 486 (Section 7.4), and (3) the Message Authentication Code (MAC) for the 487 target NSH data (depending on the integrity protection scope) 488 calculated using the MAC_KEY and optionally Context Headers encrypted 489 using ENC_KEY. 491 An SFC data plane element that needs to check the integrity of the 492 NSH data uses MAC_KEY and the HMAC algorithm for the key identifier 493 being carried in the NSH. 495 An SFC-aware SF or SFC Proxy that needs to decrypt some Context 496 Headers uses ENC_Key and the decryption algorithm for the key 497 identifier being carried in the NSH. 499 Section 7 specifies the detailed procedure. 501 4.6. Encapsulation of NSH within NSH 503 As discussed in [RFC8459], an SFC-enabled domain (called, upper-level 504 domain) may be decomposed into many sub-domains (called, lower-level 505 domains). In order to avoid maintaining state to restore back upper- 506 lower NSH information at the boundaries of lower-level domains, two 507 NSH levels are used: an Upper-NSH which is imposed at the boundaries 508 of the upper-level domain and a Lower-NSH that is pushed by the 509 Classifier of a lower-level domain in front of the original NSH 510 (Figure 4). As such, the Upper-NSH information is carried along the 511 lower-level chain without modification. The packet is forwarded in 512 the top-level domain according to the Upper-NSH, while it is 513 forwarded according to the Lower-NSH in a lower-level domain. 515 +---------------------------------+ 516 | Transport Encapsulation | 517 +->+---------------------------------+ 518 | | Lower-NSH Header | 519 | +---------------------------------+ 520 | | Upper-NSH Header | 521 | +---------------------------------+ 522 | | Original Packet | 523 +->+---------------------------------+ 524 | 525 | 526 +----Scope of NSH security protection 527 provided by a lower-level domain 529 Figure 4: Encapsulation of NSH within NSH 531 SFC data plane elements of a lower-level domain includes the Upper- 532 NSH when computing the MAC. 534 Keying material used at the upper-level domain SHOULD NOT be the same 535 as the one used by a lower-level domain. 537 5. New NSH Variable-Length Context Headers 539 This section specifies the format of new Variable-Length Context 540 headers that are used for NSH integrity protection and, optionally, 541 Context Headers encryption. 543 In particular, this section defines two "MAC and Encrypted Metadata" 544 Context Headers; each having specific deployment constraints. Unlike 545 Section 5.1, the level of assurance provided in Section 5.2 requires 546 sharing MAC_KEY with SFFs. Both Context headers have the same format 547 as shown in Section 5. 549 0 1 2 3 550 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 1 551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 552 | Metadata Class | Type |U| Length | 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | Key Length | Key Identifier (Variable) ~ 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 ~ Timestamp (8 bytes) ~ 557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 558 | IV Length | Initialization Vector (Variable) ~ 559 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 | | 561 | Message Authentication Code and optional Encrypted | 562 ~ Context Headers ~ 563 | | 564 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 Figure 5: MAC and Encrypted Metadata Context Header 568 5.1. MAC#1 Context Header 570 MAC#1 Context Header is a variable-length TLV that carries the 571 Message Authentication Code (MAC) for the Service Path Header, 572 Context Headers, and the inner packet on which NSH is imposed, 573 calculated using MAC_KEY and optionally Context Headers encrypted 574 using ENC_KEY. The scope of the integrity protection provided by 575 this TLV is depicted in Figure 6. 577 This MAC scheme does not require sharing MAC_KEY with SFFs. It does 578 not require to re-compute the MAC by each SFF because of TTL 579 processing. Section 8.1 discusses the possible threat associated 580 with this level of assurance. 582 0 1 2 3 583 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 1 584 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 585 |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<--+ 587 | Service Path Identifier | Service Index | | 588 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 589 | | | 590 ~ Variable-Length Unencrypted Context Headers (opt.) ~ | 591 | | | 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 593 | Metadata Class | Type |U| Length | | 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 595 | Key Length | Key Identifier ~ | 596 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 597 ~ Timestamp (8 bytes) ~ | 598 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 599 | IV Length | Initialization Vector ~ | 600 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 601 | ~ Context Header TLVs to encrypt (opt.) ~ | 602 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 603 | | | | 604 | ~ Inner Packet on which NSH is imposed ~ | 605 | | | | 606 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<--| 607 | | 608 | | 609 | | 610 | Integrity Protection Scope ----+ 611 +----Encrypted Data 613 Figure 6: Scope of MAC#1 615 In reference to Figure 5, the description of the fields is as 616 follows: 618 o Metadata Class: MUST be set to 0x0 (Section 2.5.1 of [RFC8300]). 620 o Type: TBD1 (See Section 9) 622 o U: Unassigned bit (Section 2.5.1 of [RFC8300]). 624 o Length: Variable. 626 o Key Length: Variable. Carries the length of the key identifier. 628 o Key Identifier: Carries a variable length Key Identifier object 629 used to identify and deliver keys to SFC data plane elements. 631 This identifier is helpful to accommodate deployments relying upon 632 keying material per SFC/SFP. The key identifier helps in 633 resolving the problem of synchronization of keying material. 635 o Timestamp: Carries an unsigned 64-bit integer value that is 636 expressed in seconds relative to 1970-01-01T00:00Z in UTC time. 637 See Section 6 for more details. 639 o IV Length: Carries the length of the IV (Section 5.2 of 640 [RFC7518]). If HMAC algorithm is used, IV length is set to zero. 642 o Initialization Vector: Carries the IV for authenticated encryption 643 algorithm as discussed in Section 5.2 of [RFC7518]. 645 o The Additional Authenticated Data (defined in [RFC7518]) MUST be 646 the Service Path header, the unencrypted Context headers, and the 647 inner packet on which the NSH is imposed . 649 o Message Authentication Code covering the entire NSH data excluding 650 the Base header. 652 5.2. MAC#2 Context Header 654 MAC#2 Context Header is a variable-length TLV that carries the MAC 655 for the entire NSH data calculated using MAC_KEY and optionally 656 Context Headers encrypted using ENC_KEY. The scope of the integrity 657 protection provided by this TLV is depicted in Figure 7. 659 0 1 2 3 660 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 1 661 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<--+ 662 |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | | 663 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 664 | Service Path Identifier | Service Index | | 665 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 666 | | | 667 ~ Variable-Length Unencrypted Context Headers (opt.) ~ | 668 | | | 669 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 670 | Metadata Class | Type |U| Length | | 671 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 672 | Key Length | Key Identifier ~ | 673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 674 ~ Timestamp (8 bytes) ~ | 675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 676 | IV Length | Initialization Vector | | 677 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 678 | ~ Context Header TLVs to encrypt (opt.) ~ | 679 +->+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 680 | | | | 681 | ~ Inner Packet on which NSH is imposed ~ | 682 | | | | 683 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<--| 684 | | 685 | | 686 | | 687 | Integrity Protection Scope ----+ 688 +----Encrypted Data 690 Figure 7: Scope of MAC#2 692 In reference to Figure 5, the description of the fields is as 693 follows: 695 o Metadata Class: MUST be set to 0x0 (Section 2.5.1 of [RFC8300]). 697 o Type: TBD2 (See Section 9) 699 o U: Unassigned bit (Section 2.5.1 of [RFC8300]). 701 o Length: Variable. 703 o Key Length: See Section 5.1. 705 o Key Identifier: See Section 5.1. 707 o Timestamp: See Section 6. 709 o IV Length: See Section 5.1. 711 o Initialization Vector: See Section 5.1. 713 o The Additional Authenticated Data (defined in [RFC7518]) MUST be 714 the entire NSH data (i.e., including the Base Header) excluding 715 the Context Headers to be encrypted. 717 o Message Authentication Code covering the entire NSH data and 718 optional encrypted Context Headers. 720 6. Timestamp Format 722 This section follows the template provided in 723 [I-D.ietf-ntp-packet-timestamps]. 725 The format of the Timestamp field introduced in Section 5 is depicted 726 in Figure 8. 728 0 1 2 3 729 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 1 730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 731 | Seconds | 732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 733 | Fraction | 734 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 Figure 8: Timestamp Field Format 738 Timestamp field format: 740 Seconds: specifies the integer portion of the number of seconds 741 since the epoch. 743 + Size: 32 bits. 745 + Units: seconds. 747 Fraction: specifies the fractional portion of the number of 748 seconds since the epoch. 750 + Size: 32 bits. 752 + Units: the unit is 2^(-32) seconds, which is roughly equal to 753 233 picoseconds. 755 Epoch: 757 The epoch is 1970-01-01T00:00Z in UTC time. 759 Leap seconds: 761 This timestamp format is affected by leap seconds. The timestamp 762 represents the number of seconds elapsed since the epoch minus the 763 number of leap seconds. 765 Resolution: 767 The resolution is 2^(-32) seconds. 769 Wraparound: 771 This time format wraps around every 2^32 seconds, which is roughly 772 136 years. The next wraparound will occur in the year 2106. 774 Synchronization aspects: 776 It is assumed that SFC data plane elements are synchronized to UTC 777 using a synchronization mechanism that is outside the scope of 778 this document. In typical deployments SFC data plane elements use 779 NTP [RFC5905] for synchronization. Thus, the timestamp may be 780 derived from the NTP-synchronized clock, allowing the timestamp to 781 be measured with respect to the clock of an NTP server. Since the 782 NTP time format is affected by leap seconds, the current timestamp 783 format is similarly affected. Therefore, the value of a timestamp 784 during or slightly after a leap second may be temporarily 785 inaccurate. 787 7. Processing Rules 789 The following subsections describe the processing rules for integrity 790 protected NSH and optionally encrypted Context Headers. 792 7.1. Generic Behavior 794 This document adheres to the recommendations in [RFC8300] for 795 handling the Context Headers at both ingress and egress SFC boundary 796 nodes. That is, to strip such context headers. 798 Failures to inject or validate the Context Headers defined in this 799 document SHOULD be logged locally while a notification alarm MAY be 800 sent to an SFC control element. Similarly, failure to validate the 801 integrity of the NSH data MUST cause that packet to be discarded 802 while a notification alarm MAY be sent to an SFC control element. 804 The details of sending notification alarms (i.e., the parameters 805 affecting the transmission of the notification alarms depend on the 806 information in the context header such as frequency, thresholds, and 807 content in the alarm) SHOULD be configurable by the SFC control 808 plane. 810 SFC-aware SFs and SFC proxies MAY be instructed to strip some 811 encrypted Context Headers from the packet or to pass the data to the 812 next SF in the service function chain after processing the content of 813 the Context Headers. If no instruction is provided, the default 814 behavior for intermediary SFC-aware nodes is to maintain such Context 815 Headers so that the information can be passed to next SFC-aware hops. 816 SFC-aware SFs and SFC proxies MUST re-apply the integrity protection 817 if any modification is made to the Context Headers (strip a Context 818 Header, update the content of an existing Context Header, insert a 819 new Context Header). 821 An SFC-aware SF or SFC Proxy that is not allowed to decrypt any 822 Context Headers MUST NOT be given access to the ENC_KEY. 824 Otherwise, an SFC-aware SF or SFC Proxy that receives encrypted 825 Context Headers, for which it is not allowed to consume a specific 826 Context Header it decrypts (but consumes others), MUST keep that 827 Context Header unaltered when forwarding the packet upstream. 829 Only one instance of "MAC and Encrypted Metadata" Context Header 830 (Section 5) is allowed. If multiple instances of "MAC and Encrypted 831 Metadata" Context Header are included in an NSH packet, the SFC data 832 element MUST process the first instance and ignore subsequent 833 instances, and MAY log or increase a counter for this event as per 834 Section 2.5.1 of [RFC8300]. 836 MTU and fragmentation considerations are discussed in Section 5 of 837 [RFC8300]. Those considerations are not reiterated here. 839 7.2. MAC NSH Data Generation 841 If the Context Headers are not encrypted, the HMAC algorithm 842 discussed in [RFC4868] is used to integrity protect the target NSH 843 data. An NSH imposer inserts a "MAC and Encrypted Metadata" Context 844 Header for integrity protection (Section 5). 846 The NSH imposer computes the message integrity for the target NSH 847 data (depending on the integrity protection scope discussed in 848 Section 5) using MAC_KEY and HMAC algorithm. It inserts the MAC in 849 the "MAC and Encrypted Metadata" Context Header. The length of the 850 MAC is decided by the HMAC algorithm adopted for the particular key 851 identifier. 853 The Message Authentication Code (T) computation process can be 854 illustrated as follows: 856 T = HMAC-SHA-256-128(MAC_KEY, A) 858 An entity in the SFP that intends to update the NSH MUST follow the 859 above behavior to maintain message integrity of the NSH for 860 subsequent validations. 862 7.3. Encrypted NSH Metadata Generation 864 An NSH imposer can encrypt Context Headers carrying privacy-sensitive 865 metadata, i.e., encrypted and unencrypted metadata may be carried 866 simultaneously in the same NSH packet (Figure 9). 868 0 1 2 3 869 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 1 870 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 871 |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | 872 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 873 | Service Path Identifier | Service Index | 874 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 875 | | 876 ~ Variable-Length Unencrypted Context Headers (opt.) ~ 877 | | 878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 879 ~ Key Identifier ~ 880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 881 ~ Timestamp ~ 882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 883 | | 884 ~ MAC and Encrypted Context Headers ~ 885 | | 886 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 888 Figure 9: NSH with Encrypted and Unencrypted Metadata 890 In an SFC-enabled domain where pervasive monitoring [RFC7258] is 891 possible, all Context Headers carrying privacy-sensitive metadata 892 MUST be encrypted; doing so privacy-sensitive metadata is not 893 revealed to attackers. Privacy specific threats are discussed in 894 Section 5.2 of [RFC6973]. 896 Using K and authenticated encryption algorithm, the NSH imposer 897 encrypts the Context Headers (as set by the control plane Section 3), 898 computes the message integrity for the target NSH data, and inserts 899 the resulting payload in the "MAC and Encrypted Metadata" Context 900 Header (Section 5). The entire TLV carrying a privacy-sensitive 901 metadata is encrypted (that is, including the MD Class, Type, Length, 902 and associated metadata of each Context Header). 904 The message Authentication Tag (T) and ciphertext (E) computation 905 process can be illustrated as follows: 907 MAC_KEY = initial MAC_KEY_LEN octets of K, 908 ENC_KEY = final ENC_KEY_LEN octets of K, 909 E = CBC-PKCS7-ENC(ENC_KEY, P), 910 M = MAC(MAC_KEY, A || IV || E || AL), 911 T = initial T_LEN octets of M. 912 MAC and Encrypted Metadata = E || T 914 As specified in [RFC7518], the octet string (AL) is equal to the 915 number of bits in the Additional Authenticated Data (A) expressed as 916 a 64-bit unsigned big-endian integer. 918 An authorized entity in the SFP that intends to update the content of 919 an encrypted Context Header or needs to add a new encrypted Context 920 Header MUST also follow the aforementioned behavior. 922 An SFF or SFC-aware SF or SFC Proxy that only has access to the 923 MAC_KEY, but not the ENC_KEY, computes the message Authentication Tag 924 (T) after decrementing the TTL (by the SFF) or SI (by an SF or SFC 925 Proxy) and replaces the Authentication Tag in the NSH with the 926 computed Authentication Tag. Similarly, an SFC-aware SF (or SFC 927 Proxy) that does not modify the encrypted Context headers also 928 follows the aforementioned behavior. 930 The message Authentication Tag (T) computation process can be 931 illustrated as follows: 933 M = MAC(MAC_KEY, A || IV || E || AL), 934 T = initial T_LEN octets of M. 936 7.4. Timestamp for Replay Attack 938 The received NSH is accepted if the Timestamp (TS) in the NSH is 939 recent enough to the reception time of the NSH (TSrt). The following 940 formula is used for this check: 942 -Delta < (TSrt ? TS) < +Delta 944 The RECOMMENDED value for the allowed Delta is 2 seconds. If the 945 timestamp is not within the boundaries, then the SFC data plane 946 element receiving such packet MUST discard the NSH message. 948 All SFC data plane elements must be synchronized among themselves. 949 These elements may be synchronized to a global reference time. 951 7.5. NSH Data Validation 953 When an SFC data plane element receives an NSH packet, it MUST first 954 ensure that a "MAC and Encrypted Metadata" Context Header is 955 included. It MUST silently discard the message if the timestamp is 956 invalid (Section 7.4). It MUST log an error at least once per the 957 SPI for which the "MAC and Encrypted Metadata" Context Header is 958 missing. 960 If the timestamp check is successfuly passed, the SFC data plane 961 element proceeds then with NSH data integrity validation. The SFC 962 data plane element computes the message integrity for the target NSH 963 data (depending on the integrity protection scope discussed in 964 Section 5) using the MAC_KEY and HMAC algorithm for the key 965 identifier. If the value of the newly generated digest is identical 966 to the one enclosed in the NSH, the SFC data plane element is certain 967 that the NSH data has not been tampered and validation is therefore 968 successful. Otherwise, the NSH packet MUST be discarded. 970 7.6. Decryption of NSH Metadata 972 If entitled to consume a supplied encrypted Context Header, an SFC- 973 aware SF or SFC Proxy decrypts metadata using (K) and decryption 974 algorithm for the key identifier in the NSH. 976 Authenticated encryption algorithm has only a single output, either a 977 plaintext or a special symbol (FAIL) that indicates that the inputs 978 are not authentic (Section 5.2.2.2 of [RFC7518]). 980 8. Security Considerations 982 NSH security considerations are discussed in Section 8 of [RFC8300]. 983 The guidelines for cryptographic key management are discussed in 984 [RFC4107]. 986 The interaction between the SFC-aware data plane elements and a key 987 management system MUST NOT be transmitted in clear since this would 988 completely destroy the security benefits of the integrity protection 989 solution defined in this document. The secret key (K) must have an 990 expiration time assigned as the latest point in time before which the 991 key may be used for integrity protection of NSH data and encryption 992 of Context Headers. Prior to the expiration of the secret key, all 993 participating service function nodes SHOULD have the control plane 994 distribute an new key identifier and associated keying material, so 995 that when the secret key is expired those nodes are prepared with the 996 new secret key. This allows the NSH Imposer to switch to the new key 997 identifier as soon as necessary. It is RECOMMENDED that the next key 998 identifier be distributed by the control plane well prior to the 999 secret key expiration time. 1001 NSH data are exposed to several threats: 1003 o A man-in-the-middle attacker modifying NSH data. 1005 o Attacker spoofing NSH data. 1007 o Attacker capturing and replaying NSH data. 1009 o Metadata in Context Headers revealing privacy-sensitive 1010 information to attackers. 1012 o Attacker replacing the packet on which NSH is imposed with a bogus 1013 or malicious packet. 1015 In an SFC-enabled domain where the above attacks are possible, NSH 1016 data MUST be integrity-protected and replay-protected, and privacy- 1017 sensitive NSH metadata MUST be encrypted for confidentiality 1018 preservation purposes. The Base and Service Path headers are not 1019 encrypted. 1021 MACs with two levels of assurance are defined in Section 5. 1022 Considerations specific to each level of assurance are discussed in 1023 the following subsections. 1025 The attacks discussed in [I-D.nguyen-sfc-security-architecture] are 1026 handled owing to the solution specified in this document, except for 1027 attacks dropping packets. Such attacks can be detected relying upon 1028 statistical analysis; such analysis is out of scope of this document. 1029 Also, if SFFs are not involved in the integrity checks, a misbehaving 1030 SFF which decrements SI while this should be done by an SF (SF bypass 1031 attack) will be detected by an upstream SF because the integrity 1032 check will fail. 1034 8.1. MAC#1 1036 An active attacker can potentially modify the Base header (e.g., 1037 decrement the TTL so the next SFF in the SFP discards the NSH 1038 packet). In the meantime, an active attacker can also drop NSH 1039 packets. As such, this attack is not considered an attack against 1040 the security mechanism specified in the document. 1042 No device other than the SFC-aware SFs in the SFC-enabled domain 1043 should be able to update the integrity protected NSH data. 1045 Similarly, no device other than the SFC-aware SFs and SFC proxies in 1046 the SFC-enabled domain be able to decrypt and update the Context 1047 Headers carrying privacy-sensitive metadata. In other words, if the 1048 SFC-aware SFs and SFC proxies in the SFC-enabled domain are 1049 considered fully trusted to act on the NSH data, only they can have 1050 access to privacy-sensitive NSH metadata and the keying material used 1051 to integrity protect NSH data and encrypt Context Headers. 1053 8.2. MAC#2 1055 SFFs can detect whether an illegitimate node has altered the content 1056 of the Base header. Such messages MUST be discarded with appropriate 1057 logs and alarms generated. 1059 9. IANA Considerations 1061 This document requests IANA to assign the following types from the 1062 "NSH IETF-Assigned Optional Variable-Length Metadata Types" (0x0000 1063 IETF Base NSH MD Class) registry available at: 1064 https://www.iana.org/assignments/nsh/nsh.xhtml#optional-variable- 1065 length-metadata-types. 1067 +-------+-------------------------------+----------------+ 1068 | Value | Description | Reference | 1069 +=======+===============================+================+ 1070 | TBD1 | MAC and Encrypted Metadata #1 | [ThisDocument] | 1071 | TBD2 | MAC and Encrypted Metadata #2 | [ThisDocument] | 1072 +-------+-------------------------------+----------------+ 1074 10. Acknowledgements 1076 This document was edited as a follow up to the discussion in 1077 IETF#104: https://datatracker.ietf.org/meeting/104/materials/slides- 1078 104-sfc-sfc-chair-slides-01 (slide 7). 1080 Thanks to Joel Halpern, Christian Jacquenet, Dirk von Hugo, Tal 1081 Mizrahi, Daniel Migault, and Diego Lopez for the comments. 1083 11. References 1085 11.1. Normative References 1087 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1088 Requirement Levels", BCP 14, RFC 2119, 1089 DOI 10.17487/RFC2119, March 1997, 1090 . 1092 [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic 1093 Key Management", BCP 107, RFC 4107, DOI 10.17487/RFC4107, 1094 June 2005, . 1096 [RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA- 1097 384, and HMAC-SHA-512 with IPsec", RFC 4868, 1098 DOI 10.17487/RFC4868, May 2007, 1099 . 1101 [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, 1102 DOI 10.17487/RFC7518, May 2015, 1103 . 1105 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 1106 Chaining (SFC) Architecture", RFC 7665, 1107 DOI 10.17487/RFC7665, October 2015, 1108 . 1110 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1111 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1112 May 2017, . 1114 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., 1115 "Network Service Header (NSH)", RFC 8300, 1116 DOI 10.17487/RFC8300, January 2018, 1117 . 1119 11.2. Informative References 1121 [I-D.arkko-farrell-arch-model-t] 1122 Arkko, J. and S. Farrell, "Challenges and Changes in the 1123 Internet Threat Model", draft-arkko-farrell-arch-model- 1124 t-03 (work in progress), March 2020. 1126 [I-D.ietf-ntp-packet-timestamps] 1127 Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for 1128 Defining Packet Timestamps", draft-ietf-ntp-packet- 1129 timestamps-09 (work in progress), March 2020. 1131 [I-D.nguyen-sfc-security-architecture] 1132 Nguyen, T. and M. Park, "A Security Architecture Against 1133 Service Function Chaining Threats", draft-nguyen-sfc- 1134 security-architecture-00 (work in progress), November 1135 2019. 1137 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1138 "Network Time Protocol Version 4: Protocol and Algorithms 1139 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1140 . 1142 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 1143 Morris, J., Hansen, M., and R. Smith, "Privacy 1144 Considerations for Internet Protocols", RFC 6973, 1145 DOI 10.17487/RFC6973, July 2013, 1146 . 1148 [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an 1149 Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May 1150 2014, . 1152 [RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for 1153 Service Function Chaining", RFC 7498, 1154 DOI 10.17487/RFC7498, April 2015, 1155 . 1157 [RFC7635] Reddy, T., Patil, P., Ravindranath, R., and J. Uberti, 1158 "Session Traversal Utilities for NAT (STUN) Extension for 1159 Third-Party Authorization", RFC 7635, 1160 DOI 10.17487/RFC7635, August 2015, 1161 . 1163 [RFC8459] Dolson, D., Homma, S., Lopez, D., and M. Boucadair, 1164 "Hierarchical Service Function Chaining (hSFC)", RFC 8459, 1165 DOI 10.17487/RFC8459, September 2018, 1166 . 1168 Authors' Addresses 1170 Mohamed Boucadair 1171 Orange 1172 Rennes 35000 1173 France 1175 Email: mohamed.boucadair@orange.com 1177 Tirumaleswar Reddy 1178 McAfee, Inc. 1179 Embassy Golf Link Business Park 1180 Bangalore, Karnataka 560071 1181 India 1183 Email: TirumaleswarReddy_Konda@McAfee.com 1184 Dan Wing 1185 Citrix Systems, Inc. 1186 USA 1188 Email: dwing-ietf@fuggles.com