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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-31) exists of draft-ietf-dtn-bpbis-28 ** Downref: Normative reference to an Informational RFC: RFC 6255 ** Obsolete normative reference: RFC 7049 (Obsoleted by RFC 8949) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Delay-Tolerant Networking E. Birrane 3 Internet-Draft K. McKeever 4 Intended status: Standards Track JHU/APL 5 Expires: June 4, 2021 December 1, 2020 7 Bundle Protocol Security Specification 8 draft-ietf-dtn-bpsec-25 10 Abstract 12 This document defines a security protocol providing data integrity 13 and confidentiality services for the Bundle Protocol. 15 Status of This Memo 17 This Internet-Draft is submitted in full conformance with the 18 provisions of BCP 78 and BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF). Note that other groups may also distribute 22 working documents as Internet-Drafts. The list of current Internet- 23 Drafts is at https://datatracker.ietf.org/drafts/current/. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 This Internet-Draft will expire on June 4, 2021. 32 Copyright Notice 34 Copyright (c) 2020 IETF Trust and the persons identified as the 35 document authors. All rights reserved. 37 This document is subject to BCP 78 and the IETF Trust's Legal 38 Provisions Relating to IETF Documents 39 (https://trustee.ietf.org/license-info) in effect on the date of 40 publication of this document. Please review these documents 41 carefully, as they describe your rights and restrictions with respect 42 to this document. Code Components extracted from this document must 43 include Simplified BSD License text as described in Section 4.e of 44 the Trust Legal Provisions and are provided without warranty as 45 described in the Simplified BSD License. 47 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 50 1.1. Supported Security Services . . . . . . . . . . . . . . . 3 51 1.2. Specification Scope . . . . . . . . . . . . . . . . . . . 4 52 1.3. Related Documents . . . . . . . . . . . . . . . . . . . . 5 53 1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 54 2. Design Decisions . . . . . . . . . . . . . . . . . . . . . . 7 55 2.1. Block-Level Granularity . . . . . . . . . . . . . . . . . 7 56 2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 8 57 2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 9 58 2.4. User-Defined Security Contexts . . . . . . . . . . . . . 9 59 2.5. Deterministic Processing . . . . . . . . . . . . . . . . 9 60 3. Security Blocks . . . . . . . . . . . . . . . . . . . . . . . 10 61 3.1. Block Definitions . . . . . . . . . . . . . . . . . . . . 10 62 3.2. Uniqueness . . . . . . . . . . . . . . . . . . . . . . . 10 63 3.3. Target Multiplicity . . . . . . . . . . . . . . . . . . . 12 64 3.4. Target Identification . . . . . . . . . . . . . . . . . . 13 65 3.5. Block Representation . . . . . . . . . . . . . . . . . . 13 66 3.6. Abstract Security Block . . . . . . . . . . . . . . . . . 13 67 3.7. Block Integrity Block . . . . . . . . . . . . . . . . . . 16 68 3.8. Block Confidentiality Block . . . . . . . . . . . . . . . 17 69 3.9. Block Interactions . . . . . . . . . . . . . . . . . . . 18 70 3.10. Parameter and Result Identification . . . . . . . . . . . 20 71 3.11. BSP Block Examples . . . . . . . . . . . . . . . . . . . 20 72 3.11.1. Example 1: Constructing a Bundle with Security . . . 20 73 3.11.2. Example 2: Adding More Security At A New Node . . . 21 74 4. Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . 23 75 5. Security Processing . . . . . . . . . . . . . . . . . . . . . 24 76 5.1. Bundles Received from Other Nodes . . . . . . . . . . . . 24 77 5.1.1. Receiving BCBs . . . . . . . . . . . . . . . . . . . 24 78 5.1.2. Receiving BIBs . . . . . . . . . . . . . . . . . . . 25 79 5.2. Bundle Fragmentation and Reassembly . . . . . . . . . . . 26 80 6. Key Management . . . . . . . . . . . . . . . . . . . . . . . 27 81 7. Security Policy Considerations . . . . . . . . . . . . . . . 27 82 7.1. Security Reason Codes . . . . . . . . . . . . . . . . . . 28 83 8. Security Considerations . . . . . . . . . . . . . . . . . . . 29 84 8.1. Attacker Capabilities and Objectives . . . . . . . . . . 30 85 8.2. Attacker Behaviors and BPSec Mitigations . . . . . . . . 31 86 8.2.1. Eavesdropping Attacks . . . . . . . . . . . . . . . . 31 87 8.2.2. Modification Attacks . . . . . . . . . . . . . . . . 32 88 8.2.3. Topology Attacks . . . . . . . . . . . . . . . . . . 33 89 8.2.4. Message Injection . . . . . . . . . . . . . . . . . . 33 90 9. Security Context Considerations . . . . . . . . . . . . . . . 34 91 9.1. Mandating Security Contexts . . . . . . . . . . . . . . . 34 92 9.2. Identification and Configuration . . . . . . . . . . . . 35 93 9.3. Authorship . . . . . . . . . . . . . . . . . . . . . . . 36 94 10. Defining Other Security Blocks . . . . . . . . . . . . . . . 37 95 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 96 11.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 39 97 11.2. Bundle Status Report Reason Codes . . . . . . . . . . . 39 98 11.3. Security Context Identifiers . . . . . . . . . . . . . . 40 99 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 40 100 12.1. Normative References . . . . . . . . . . . . . . . . . . 40 101 12.2. Informative References . . . . . . . . . . . . . . . . . 41 102 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 41 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42 105 1. Introduction 107 This document defines security features for the Bundle Protocol (BP) 108 [I-D.ietf-dtn-bpbis] and is intended for use in Delay Tolerant 109 Networks (DTNs) to provide security services between a security 110 source and a security acceptor. When the security source is the 111 bundle source and when the security acceptor is the bundle 112 destination, the security service provides end-to-end protection. 114 The Bundle Protocol specification [I-D.ietf-dtn-bpbis] defines DTN as 115 referring to "a networking architecture providing communications in 116 and/or through highly stressed environments" where "BP may be viewed 117 as sitting at the application layer of some number of constituent 118 networks, forming a store-carry-forward overlay network". The term 119 "stressed" environment refers to multiple challenging conditions 120 including intermittent connectivity, large and/or variable delays, 121 asymmetric data rates, and high bit error rates. 123 It should be presumed that the BP will be deployed such that the 124 network cannot be trusted, posing the usual security challenges 125 related to confidentiality and integrity. However, the stressed 126 nature of the BP operating environment imposes unique conditions 127 where usual transport security mechanisms may not be sufficient. For 128 example, the store-carry-forward nature of the network may require 129 protecting data at rest, preventing unauthorized consumption of 130 critical resources such as storage space, and operating without 131 regular contact with a centralized security oracle (such as a 132 certificate authority). 134 An end-to-end security service is needed that operates in all of the 135 environments where the BP operates. 137 1.1. Supported Security Services 139 BPSec provides integrity and confidentiality services for BP bundles, 140 as defined in this section. 142 Integrity services ensure that changes to target data within a bundle 143 can be discovered. Data changes may be caused by processing errors, 144 environmental conditions, or intentional manipulation. In the 145 context of BPSec, integrity services apply to plain text in the 146 bundle. 148 Confidentiality services ensure that target data is unintelligible to 149 nodes in the DTN, except for authorized nodes possessing special 150 information. This generally means producing cipher text from plain 151 text and generating authentication information for that cipher text. 152 Confidentiality, in this context, applies to the contents of target 153 data and does not extend to hiding the fact that confidentiality 154 exists in the bundle. 156 NOTE: Hop-by-hop authentication is NOT a supported security service 157 in this specification, for two reasons. 159 1. The term "hop-by-hop" is ambiguous in a BP overlay, as nodes that 160 are adjacent in the overlay may not be adjacent in physical 161 connectivity. This condition is difficult or impossible to 162 detect and therefore hop-by-hop authentication is difficult or 163 impossible to enforce. 165 2. Hop-by-hop authentication cannot be deployed in a network if 166 adjacent nodes in the network have incompatible security 167 capabilities. 169 1.2. Specification Scope 171 This document defines the security services provided by the BPSec. 172 This includes the data specification for representing these services 173 as BP extension blocks, and the rules for adding, removing, and 174 processing these blocks at various points during the bundle's 175 traversal of the DTN. 177 BPSec addresses only the security of data traveling over the DTN, not 178 the underlying DTN itself. Furthermore, while the BPSec protocol can 179 provide security-at-rest in a store-carry-forward network, it does 180 not address threats which share computing resources with the DTN and/ 181 or BPSec software implementations. These threats may be malicious 182 software or compromised libraries which intend to intercept data or 183 recover cryptographic material. Here, it is the responsibility of 184 the BPSec implementer to ensure that any cryptographic material, 185 including shared secret or private keys, is protected against access 186 within both memory and storage devices. 188 Completely trusted networks are extremely uncommon. Amongst 189 untrusted networks, different networking conditions and operational 190 considerations require varying strengths of security mechanism. 191 Mandating a single security context may result in too much security 192 for some networks and too little security in others. It is expected 193 that separate documents define different security contexts for use in 194 different networks. A set of default security contexts are defined 195 in ([I-D.ietf-dtn-bpsec-interop-sc]) and provide basic security 196 services for interoperability testing and for operational use on the 197 terrestrial Internet. 199 This specification addresses neither the fitness of externally- 200 defined cryptographic methods nor the security of their 201 implementation. 203 This specification does not address the implementation of security 204 policy and does not provide a security policy for the BPSec. Similar 205 to cipher suites, security policies are based on the nature and 206 capabilities of individual networks and network operational concepts. 207 This specification does provide policy considerations when building a 208 security policy. 210 With the exception of the Bundle Protocol, this specification does 211 not address how to combine the BPSec security blocks with other 212 protocols, other BP extension blocks, or other best practices to 213 achieve security in any particular network implementation. 215 1.3. Related Documents 217 This document is best read and understood within the context of the 218 following other DTN documents: 220 "Delay-Tolerant Networking Architecture" [RFC4838] defines the 221 architecture for DTNs and identifies certain security assumptions 222 made by existing Internet protocols that are not valid in a DTN. 224 The Bundle Protocol [I-D.ietf-dtn-bpbis] defines the format and 225 processing of bundles, defines the extension block format used to 226 represent BPSec security blocks, and defines the canonical block 227 structure used by this specification. 229 The Concise Binary Object Representation (CBOR) format [RFC7049] 230 defines a data format that allows for small code size, fairly small 231 message size, and extensibility without version negotiation. The 232 block-specific-data associated with BPSec security blocks are encoded 233 in this data format. 235 The Bundle Security Protocol [RFC6257] and Streamlined Bundle 236 Security Protocol [I-D.birrane-dtn-sbsp] documents introduced the 237 concepts of using BP extension blocks for security services in a DTN. 238 The BPSec is a continuation and refinement of these documents. 240 1.4. Terminology 242 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 243 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 244 "OPTIONAL" in this document are to be interpreted as described in BCP 245 14 [RFC2119] [RFC8174] when, and only when, they appear in all 246 capitals, as shown here. 248 This section defines terminology either unique to the BPSec or 249 otherwise necessary for understanding the concepts defined in this 250 specification. 252 o Bundle Destination - the node which receives a bundle and delivers 253 the payload of the bundle to an application. Also, the Node ID of 254 the Bundle Protocol Agent (BPA) receiving the bundle. The bundle 255 destination acts as the security acceptor for every security 256 target in every security block in every bundle it receives. 258 o Bundle Source - the node which originates a bundle. Also, the 259 Node ID of the BPA originating the bundle. 261 o Cipher Suite - a set of one or more algorithms providing integrity 262 and/or confidentiality services. Cipher suites may define user 263 parameters (e.g. secret keys to use) but do not provide values for 264 those parameters. 266 o Forwarder - any node that transmits a bundle in the DTN. Also, 267 the Node ID of the BPA that sent the bundle on its most recent 268 hop. 270 o Intermediate Receiver, Waypoint, or Next Hop - any node that 271 receives a bundle from a Forwarder that is not the Bundle 272 Destination. Also, the Node ID of the BPA at any such node. 274 o Path - the ordered sequence of nodes through which a bundle passes 275 on its way from Source to Destination. The path is not 276 necessarily known in advance by the bundle or any BPAs in the DTN. 278 o Security Acceptor - a bundle node that processes and dispositions 279 one or more security blocks in a bundle. Also, the Node ID of 280 that node. 282 o Security Block - a BPSec extension block in a bundle. 284 o Security Context - the set of assumptions, algorithms, 285 configurations and policies used to implement security services. 287 o Security Operation - the application of a given security service 288 to a security target, notated as OP(security service, security 289 target). For example, OP(bcb-confidentiality, payload). Every 290 security operation in a bundle MUST be unique, meaning that a 291 given security service can only be applied to a security target 292 once in a bundle. A security operation is implemented by a 293 security block. 295 o Security Service - a process that gives some protection to a 296 security target. For example, this specification defines security 297 services for plain text integrity (bib-integrity), and 298 authenticated plain text confidentiality with additional 299 authenticated data (bcb-confidentiality). 301 o Security Source - a bundle node that adds a security block to a 302 bundle. Also, the Node ID of that node. 304 o Security Target - the block within a bundle that receives a 305 security service as part of a security operation. 307 2. Design Decisions 309 The application of security services in a DTN is a complex endeavor 310 that must consider physical properties of the network (such as 311 connectivity and propagation times), policies at each node, 312 application security requirements, and current and future threat 313 environments. This section identifies those desirable properties 314 that guide design decisions for this specification and are necessary 315 for understanding the format and behavior of the BPSec protocol. 317 2.1. Block-Level Granularity 319 Security services within this specification must allow different 320 blocks within a bundle to have different security services applied to 321 them. 323 Blocks within a bundle represent different types of information. The 324 primary block contains identification and routing information. The 325 payload block carries application data. Extension blocks carry a 326 variety of data that may augment or annotate the payload, or 327 otherwise provide information necessary for the proper processing of 328 a bundle along a path. Therefore, applying a single level and type 329 of security across an entire bundle fails to recognize that blocks in 330 a bundle represent different types of information with different 331 security needs. 333 For example, a payload block might be encrypted to protect its 334 contents and an extension block containing summary information 335 related to the payload might be integrity signed but unencrypted to 336 provide waypoints access to payload-related data without providing 337 access to the payload. 339 2.2. Multiple Security Sources 341 A bundle can have multiple security blocks and these blocks can have 342 different security sources. BPSec implementations MUST NOT assume 343 that all blocks in a bundle have the same security operations applied 344 to them. 346 The Bundle Protocol allows extension blocks to be added to a bundle 347 at any time during its existence in the DTN. When a waypoint adds a 348 new extension block to a bundle, that extension block MAY have 349 security services applied to it by that waypoint. Similarly, a 350 waypoint MAY add a security service to an existing block, consistent 351 with its security policy. 353 When a waypoint adds a security service to the bundle, the waypoint 354 is the security source for that service. The security block(s) which 355 represent that service in the bundle may need to record this security 356 source as the bundle destination might need this information for 357 processing. 359 For example, a bundle source may choose to apply an integrity service 360 to its plain text payload. Later a waypoint node, representing a 361 gateway to another portion of the DTN, may receive the bundle and 362 choose to apply a confidentiality service. In this case, the 363 integrity security source is the bundle source and the 364 confidentiality security source is the waypoint node. 366 In cases where the security source and security acceptor are not the 367 bundle source and bundle destination, it is possible that the bundle 368 will reach the bundle destination prior to reaching a security 369 acceptor. In cases where this may be a practical problem, it is 370 recommended that solutions such as bundle encapsulation can be used 371 to ensure that a bundle be delivered to a security acceptor prior to 372 being delivered to the bundle destination. Generally, if a bundle 373 reaches a waypoint that has the appropriate configuration and policy 374 to act as a security acceptor for a security service in the bundle, 375 then the waypoint should act as that security acceptor. 377 2.3. Mixed Security Policy 379 The security policy enforced by nodes in the DTN may differ. 381 Some waypoints will have security policies that require evaluating 382 security services even if they are not the bundle destination or the 383 final intended acceptor of the service. For example, a waypoint 384 could choose to verify an integrity service even though the waypoint 385 is not the bundle destination and the integrity service will be 386 needed by other nodes along the bundle's path. 388 Some waypoints will determine, through policy, that they are the 389 intended recipient of the security service and terminate the security 390 service in the bundle. For example, a gateway node could determine 391 that, even though it is not the destination of the bundle, it should 392 verify and remove a particular integrity service or attempt to 393 decrypt a confidentiality service, before forwarding the bundle along 394 its path. 396 Some waypoints could understand security blocks but refuse to process 397 them unless they are the bundle destination. 399 2.4. User-Defined Security Contexts 401 A security context is the union of security algorithms (cipher 402 suites), policies associated with the use of those algorithms, and 403 configuration values. Different contexts may specify different 404 algorithms, different polices, or different configuration values used 405 in the implementation of their security services. BPSec provides a 406 mechanism to define security contexts. Users may select from 407 registered security contexts and customize those contexts through 408 security context parameters. 410 For example, some users might prefer a SHA2 hash function for 411 integrity whereas other users might prefer a SHA3 hash function. 412 Providing either separate security contexts or a single, 413 parameterized security context allows users flexibility in applying 414 the desired cipher suite, policy, and configuration when populating a 415 security block. 417 2.5. Deterministic Processing 419 Whenever a node determines that it must process more than one 420 security block in a received bundle (either because the policy at a 421 waypoint states that it should process security blocks or because the 422 node is the bundle destination) the order in which security blocks 423 are processed must be deterministic. All nodes must impose this same 424 deterministic processing order for all security blocks. This 425 specification provides determinism in the application and evaluation 426 of security services, even when doing so results in a loss of 427 flexibility. 429 3. Security Blocks 431 3.1. Block Definitions 433 This specification defines two types of security block: the Block 434 Integrity Block (BIB) and the Block Confidentiality Block (BCB). 436 The BIB is used to ensure the integrity of its plain text security 437 target(s). The integrity information in the BIB MAY be verified 438 by any node along the bundle path from the BIB security source to 439 the bundle destination. Waypoints add or remove BIBs from bundles 440 in accordance with their security policy. BIBs are never used for 441 integrity protection of the cipher text provided by a BCB. 442 Because security policy at BPSec nodes may differ regarding 443 integrity verification, BIBs do not guarantee hop-by-hop 444 authentication, as discussed in Section 1.1. 446 The BCB indicates that the security target(s) have been encrypted 447 at the BCB security source in order to protect their content while 448 in transit. The BCB is decrypted by security acceptor nodes in 449 the network, up to and including the bundle destination, as a 450 matter of security policy. BCBs additionally provide integrity 451 protection mechanisms for the cipher text they generate. 453 3.2. Uniqueness 455 Security operations in a bundle MUST be unique; the same security 456 service MUST NOT be applied to a security target more than once in a 457 bundle. Since a security operation is represented by a security 458 block, this means that multiple security blocks of the same type 459 cannot share the same security targets. A new security block MUST 460 NOT be added to a bundle if a pre-existing security block of the same 461 type is already defined for the security target of the new security 462 block. 464 This uniqueness requirement ensures that there is no ambiguity 465 related to the order in which security blocks are processed or how 466 security policy can be specified to require certain security services 467 be present in a bundle. 469 Using the notation OP(service, target), several examples illustrate 470 this uniqueness requirement. 472 o Signing the payload twice: The two operations OP(bib-integrity, 473 payload) and OP(bib-integrity, payload) are redundant and MUST NOT 474 both be present in the same bundle at the same time. 476 o Signing different blocks: The two operations OP(bib-integrity, 477 payload) and OP(bib-integrity, extension_block_1) are not 478 redundant and both may be present in the same bundle at the same 479 time. Similarly, the two operations OP(bib-integrity, 480 extension_block_1) and OP(bib-integrity, extension_block_2) are 481 also not redundant and may both be present in the bundle at the 482 same time. 484 o Different Services on same block: The two operations OP(bib- 485 integrity, payload) and OP(bcb-confidentiality, payload) are not 486 inherently redundant and may both be present in the bundle at the 487 same time, pursuant to other processing rules in this 488 specification. 490 o Different services from different block types: The notation 491 OP(service, target) refers specifically to a security block, as 492 the security block is the embodiment of a security service applied 493 to a security target in a bundle. Were some Other Security Block 494 (OSB) to be defined providing an integrity service, then the 495 operations OP(bib-integrity, target) and OP(osb-integrity, target) 496 MAY both be present in the same bundle if so allowed by the 497 definition of the OSB, as discussed in Section 10. 499 NOTES: 501 A security block may be removed from a bundle as part of security 502 processing at a waypoint node with a new security block being 503 added to the bundle by that node. In this case, conflicting 504 security blocks never co-exist in the bundle at the same time and 505 the uniqueness requirement is not violated. 507 A cipher text integrity mechanism (such as associated 508 authenticated data) calculated by a cipher suite and transported 509 in a BCB is considered part of the confidentiality service and, 510 therefore, unique from the plain text integrity service provided 511 by a BIB. 513 The security blocks defined in this specification (BIB and BCB) 514 are designed with the intention that the BPA adding these blocks 515 is the authoritative source of the security service. If a BPA 516 adds a BIB on a security target, then the BIB is expected to be 517 the authoritative source of integrity for that security target. 518 If a BPA adds a BCB to a security target, then the BCB is expected 519 to be the authoritative source of confidentiality for that 520 security target. More complex scenarios, such as having multiple 521 nodes in a network sign the same security target, can be 522 accommodated using the definition of custom security contexts 523 (Section 9) and/or the definition of other security blocks 524 (Section 10). 526 3.3. Target Multiplicity 528 A single security block MAY represent multiple security operations as 529 a way of reducing the overall number of security blocks present in a 530 bundle. In these circumstances, reducing the number of security 531 blocks in the bundle reduces the amount of redundant information in 532 the bundle. 534 A set of security operations can be represented by a single security 535 block when all of the following conditions are true. 537 o The security operations apply the same security service. For 538 example, they are all integrity operations or all confidentiality 539 operations. 541 o The security context parameters for the security operations are 542 identical. 544 o The security source for the security operations is the same, 545 meaning the set of operations are being added by the same node. 547 o No security operations have the same security target, as that 548 would violate the need for security operations to be unique. 550 o None of the security operations conflict with security operations 551 already present in the bundle. 553 When representing multiple security operations in a single security 554 block, the information that is common across all operations is 555 represented once in the security block, and the information which is 556 different (e.g., the security targets) are represented individually. 558 It is RECOMMENDED that if a node processes any security operation in 559 a security block that it process all security operations in the 560 security block. This allows security sources to assert that the set 561 of security operations in a security block are expected to be 562 processed by the same security acceptor. However, the determination 563 of whether a node actually is a security acceptor or not is a matter 564 of the policy of the node itself. In cases where a receiving node 565 determines that it is the security acceptor of only a subset of the 566 security operations in a security block, the node may choose to only 567 process that subset of security operations. 569 3.4. Target Identification 571 A security target is a block in the bundle to which a security 572 service applies. This target must be uniquely and unambiguously 573 identifiable when processing a security block. The definition of the 574 extension block header from [I-D.ietf-dtn-bpbis] provides a "Block 575 Number" field suitable for this purpose. Therefore, a security 576 target in a security block MUST be represented as the Block Number of 577 the target block. 579 3.5. Block Representation 581 Each security block uses the Canonical Bundle Block Format as defined 582 in [I-D.ietf-dtn-bpbis]. That is, each security block is comprised 583 of the following elements: 585 o block type code 587 o block number 589 o block processing control flags 591 o CRC type 593 o block-type-specific-data 595 o CRC field (if present) 597 Security-specific information for a security block is captured in the 598 block-type-specific-data field. 600 3.6. Abstract Security Block 602 The structure of the security-specific portions of a security block 603 is identical for both the BIB and BCB Block Types. Therefore, this 604 section defines an Abstract Security Block (ASB) data structure and 605 discusses the definition, processing, and other constraints for using 606 this structure. An ASB is never directly instantiated within a 607 bundle, it is only a mechanism for discussing the common aspects of 608 BIB and BCB security blocks. 610 The fields of the ASB SHALL be as follows, listed in the order in 611 which they must appear. 613 Security Targets: 614 This field identifies the block(s) targeted by the security 615 operation(s) represented by this security block. Each target 616 block is represented by its unique Block Number. This field 617 SHALL be represented by a CBOR array of data items. Each 618 target within this CBOR array SHALL be represented by a CBOR 619 unsigned integer. This array MUST have at least 1 entry and 620 each entry MUST represent the Block Number of a block that 621 exists in the bundle. There MUST NOT be duplicate entries in 622 this array. The order of elements in this list has no semantic 623 meaning outside of the context of this block. Within the 624 block, the ordering of targets must match the ordering of 625 results associated with these targets. 627 Security Context Id: 628 This field identifies the security context used to implement 629 the security service represented by this block and applied to 630 each security target. This field SHALL be represented by a 631 CBOR unsigned integer. The values for this Id should come from 632 the registry defined in Section 11.3 634 Security Context Flags: 635 This field identifies which optional fields are present in the 636 security block. This field SHALL be represented as a CBOR 637 unsigned integer whose contents shall be interpreted as a bit 638 field. Each bit in this bit field indicates the presence (bit 639 set to 1) or absence (bit set to 0) of optional data in the 640 security block. The association of bits to security block data 641 is defined as follows. 643 Bit 0 (the least-significant bit, 0x01): Security Context 644 Parameters Present Flag. 646 Bit 1 (0x02): Security Source Present Flag. 648 Bit >1 Reserved 650 Implementations MUST set reserved bits to 0 when writing this 651 field and MUST ignore the values of reserved bits when reading 652 this field. For unreserved bits, a value of 1 indicates that 653 the associated security block field MUST be included in the 654 security block. A value of 0 indicates that the associated 655 security block field MUST NOT be in the security block. 657 Security Source (Optional): 658 This field identifies the Endpoint that inserted the security 659 block in the bundle. If the security source field is not 660 present then the source MUST be inferred from other 661 information, such as the bundle source, previous hop, or other 662 values defined by security policy. This field SHALL be 663 represented by a CBOR array in accordance with 665 [I-D.ietf-dtn-bpbis] rules for representing Endpoint 666 Identifiers (EIDs). 668 Security Context Parameters (Optional): 669 This field captures one or more security context parameters 670 that should be used when processing the security service 671 described by this security block. This field SHALL be 672 represented by a CBOR array. Each entry in this array is a 673 single security context parameter. A single parameter SHALL 674 also be represented as a CBOR array comprising a 2-tuple of the 675 id and value of the parameter, as follows. 677 * Parameter Id. This field identifies which parameter is 678 being specified. This field SHALL be represented as a CBOR 679 unsigned integer. Parameter Ids are selected as described 680 in Section 3.10. 682 * Parameter Value. This field captures the value associated 683 with this parameter. This field SHALL be represented by the 684 applicable CBOR representation of the parameter, in 685 accordance with Section 3.10. 687 The logical layout of the parameters array is illustrated in 688 Figure 1. 690 +----------------+----------------+ +----------------+ 691 | Parameter 1 | Parameter 2 | ... | Parameter N | 692 +------+---------+------+---------+ +------+---------+ 693 | Id | Value | Id | Value | | Id | Value | 694 +------+---------+------+---------+ +------+---------+ 696 Figure 1: Security Context Parameters 698 Security Results: 699 This field captures the results of applying a security service 700 to the security targets of the security block. This field 701 SHALL be represented as a CBOR array of target results. Each 702 entry in this array represents the set of security results for 703 a specific security target. The target results MUST be ordered 704 identically to the Security Targets field of the security 705 block. This means that the first set of target results in this 706 array corresponds to the first entry in the Security Targets 707 field of the security block, and so on. There MUST be one 708 entry in this array for each entry in the Security Targets 709 field of the security block. 711 The set of security results for a target is also represented as 712 a CBOR array of individual results. An individual result is 713 represented as a 2-tuple of a result id and a result value, 714 defined as follows. 716 * Result Id. This field identifies which security result is 717 being specified. Some security results capture the primary 718 output of a cipher suite. Other security results contain 719 additional annotative information from cipher suite 720 processing. This field SHALL be represented as a CBOR 721 unsigned integer. Security result Ids will be as specified 722 in Section 3.10. 724 * Result Value. This field captures the value associated with 725 the result. This field SHALL be represented by the 726 applicable CBOR representation of the result value, in 727 accordance with Section 3.10. 729 The logical layout of the security results array is illustrated 730 in Figure 2. In this figure there are N security targets for 731 this security block. The first security target contains M 732 results and the Nth security target contains K results. 734 +------------------------------+ +------------------------------+ 735 | Target 1 | | Target N | 736 +------------+----+------------+ +------------------------------+ 737 | Result 1 | | Result M | ... | Result 1 | | Result K | 738 +----+-------+ .. +----+-------+ +----+-------+ .. +----+-------+ 739 | Id | Value | | Id | Value | | Id | Value | | Id | Value | 740 +----+-------+ +----+-------+ +----+-------+ +----+-------+ 742 Figure 2: Security Results 744 3.7. Block Integrity Block 746 A BIB is a bundle extension block with the following characteristics. 748 The Block Type Code value is as specified in Section 11.1. 750 The block-type-specific-data field follows the structure of the 751 ASB. 753 A security target listed in the Security Targets field MUST NOT 754 reference a security block defined in this specification (e.g., a 755 BIB or a BCB). 757 The Security Context MUST utilize an authentication mechanism or 758 an error detection mechanism. 760 The EID of the security source MAY be present. If this field is 761 not present, then the security source of the block SHOULD be 762 inferred according to security policy and MAY default to the 763 bundle source. The security source MAY be specified as part of 764 security context parameters described in Section 3.10. 766 Notes: 768 o Designers SHOULD carefully consider the effect of setting flags 769 that either discard the block or delete the bundle in the event 770 that this block cannot be processed. 772 o Since OP(bib-integrity, target) is allowed only once in a bundle 773 per target, it is RECOMMENDED that users wishing to support 774 multiple integrity mechanisms for the same target define a multi- 775 result security context. Such a context could generate multiple 776 security results for the same security target using different 777 integrity-protection mechanisms or different configurations for 778 the same integrity-protection mechanism. 780 o A BIB is used to verify the plain text integrity of its security 781 target. However, a single BIB MAY include security results for 782 blocks other than its security target when doing so establishes a 783 needed relationship between the BIB security target and other 784 blocks in the bundle (such as the primary block). 786 o Security information MAY be checked at any hop on the way to the 787 bundle destination that has access to the required keying 788 information, in accordance with Section 3.9. 790 3.8. Block Confidentiality Block 792 A BCB is a bundle extension block with the following characteristics. 794 The Block Type Code value is as specified in Section 11.1. 796 The Block Processing Control flags value can be set to whatever 797 values are required by local policy with the following exceptions. 798 BCB blocks MUST have the "block must be replicated in every 799 fragment" flag set if one of the targets is the payload block. 800 Having that BCB in each fragment indicates to a receiving node 801 that the payload portion of each fragment represents cipher text. 802 BCB blocks MUST NOT have the "block must be removed from bundle if 803 it can't be processed" flag set. Removing a BCB from a bundle 804 without decrypting its security targets removes information from 805 the bundle necessary for their later decryption. 807 The block-type-specific-data fields follow the structure of the 808 ASB. 810 A security target listed in the Security Targets field can 811 reference the payload block, a non-security extension block, or a 812 BIB. A BCB MUST NOT include another BCB as a security target. A 813 BCB MUST NOT target the primary block. A BCB MUST NOT target a 814 BIB block unless it shares a security target with that BIB block. 816 Any Security Context used by a BCB MUST utilize a confidentiality 817 cipher that provides authenticated encryption with associated data 818 (AEAD). 820 Additional information created by a cipher suite (such as an 821 authentication tag) can be placed either in a security result 822 field or in the generated cipher text. The determination of where 823 to place this information is a function of the cipher suite and 824 security context used. 826 The EID of the security source MAY be present. If this field is 827 not present, then the security source of the block SHOULD be 828 inferred according to security policy and MAY default to the 829 bundle source. The security source MAY be specified as part of 830 security context parameters described in Section 3.10. 832 The BCB modifies the contents of its security target(s). When a BCB 833 is applied, the security target body data are encrypted "in-place". 834 Following encryption, the security target block-type-specific-data 835 field contains cipher text, not plain text. 837 Notes: 839 o It is RECOMMENDED that designers carefully consider the effect of 840 setting flags that delete the bundle in the event that this block 841 cannot be processed. 843 o The BCB block processing control flags can be set independently 844 from the processing control flags of the security target(s). The 845 setting of such flags should be an implementation/policy decision 846 for the encrypting node. 848 3.9. Block Interactions 850 The security block types defined in this specification are designed 851 to be as independent as possible. However, there are some cases 852 where security blocks may share a security target creating processing 853 dependencies. 855 If a security target of a BCB is also a security target of a BIB, an 856 undesirable condition occurs where a waypoint would be unable to 857 validate the BIB because one of its security target's contents have 858 been encrypted by a BCB. To address this situation the following 859 processing rules MUST be followed. 861 o When adding a BCB to a bundle, if some (or all) of the security 862 targets of the BCB also match all of the security targets of an 863 existing BIB, then the existing BIB MUST also be encrypted. This 864 can be accomplished by either adding a new BCB that targets the 865 existing BIB, or by adding the BIB to the list of security targets 866 for the BCB. Deciding which way to represent this situation is a 867 matter of security policy. 869 o When adding a BCB to a bundle, if some (or all) of the security 870 targets of the BCB match some (but not all) of the security 871 targets of a BIB then that BIB MUST be altered in the following 872 way. Any security results in the BIB associated with the BCB 873 security targets MUST be removed from the BIB and placed in a new 874 BIB. This newly created BIB MUST then be encrypted. The 875 encryption of the new BIB can be accomplished by either adding a 876 new BCB that targets the new BIB, or by adding the new BIB to the 877 list of security targets for the BCB. Deciding which way to 878 represent this situation is a matter of security policy. 880 o A BIB MUST NOT be added for a security target that is already the 881 security target of a BCB as this would cause ambiguity in block 882 processing order. 884 o A BIB integrity value MUST NOT be checked if the BIB is the 885 security target of an existing BCB. In this case, the BIB data is 886 encrypted. 888 o A BIB integrity value MUST NOT be checked if the security target 889 associated with that value is also the security target of a BCB. 890 In such a case, the security target data contains cipher text as 891 it has been encrypted. 893 o As mentioned in Section 3.7, a BIB MUST NOT have a BCB as its 894 security target. 896 These restrictions on block interactions impose a necessary ordering 897 when applying security operations within a bundle. Specifically, for 898 a given security target, BIBs MUST be added before BCBs. This 899 ordering MUST be preserved in cases where the current BPA is adding 900 all of the security blocks for the bundle or whether the BPA is a 901 waypoint adding new security blocks to a bundle that already contains 902 security blocks. 904 In cases where a security source wishes to calculate both a plain 905 text integrity mechanism and encrypt a security target, a BCB with a 906 security context that generates an integrity-protection mechanism as 907 one or more additional security results MUST be used instead of 908 adding both a BIB and then a BCB for the security target at the 909 security source. 911 3.10. Parameter and Result Identification 913 Each security context MUST define its own context parameters and 914 results. Each defined parameter and result is represented as the 915 tuple of an identifier and a value. Identifiers are always 916 represented as a CBOR unsigned integer. The CBOR encoding of values 917 is as defined by the security context specification. 919 Identifiers MUST be unique for a given security context but do not 920 need to be unique amongst all security contexts. 922 An example of a security context can be found at 923 [I-D.ietf-dtn-bpsec-interop-sc]. 925 3.11. BSP Block Examples 927 This section provides two examples of BPSec blocks applied to a 928 bundle. In the first example, a single node adds several security 929 operations to a bundle. In the second example, a waypoint node 930 received the bundle created in the first example and adds additional 931 security operations. In both examples, the first column represents 932 blocks within a bundle and the second column represents the Block 933 Number for the block, using the terminology B1...Bn for the purpose 934 of illustration. 936 3.11.1. Example 1: Constructing a Bundle with Security 938 In this example a bundle has four non-security-related blocks: the 939 primary block (B1), two extension blocks (B4,B5), and a payload block 940 (B6). The bundle source wishes to provide an integrity signature of 941 the plain text associated with the primary block, the second 942 extension block, and the payload. The bundle source also wishes to 943 provide confidentiality for the first extension block. The resultant 944 bundle is illustrated in Figure 3 and the security actions are 945 described below. 947 Block in Bundle ID 948 +==========================================+====+ 949 | Primary Block | B1 | 950 +------------------------------------------+----+ 951 | BIB | B2 | 952 | OP(bib-integrity, targets=B1, B5, B6) | | 953 +------------------------------------------+----+ 954 | BCB | B3 | 955 | OP(bcb-confidentiality, target=B4) | | 956 +------------------------------------------+----+ 957 | Extension Block (encrypted) | B4 | 958 +------------------------------------------+----+ 959 | Extension Block | B5 | 960 +------------------------------------------+----+ 961 | Payload Block | B6 | 962 +------------------------------------------+----+ 964 Figure 3: Security at Bundle Creation 966 The following security actions were applied to this bundle at its 967 time of creation. 969 o An integrity signature applied to the canonical form of the 970 primary block (B1), the canonical form of the block-type-specific- 971 data field of the second extension block (B5) and the canonical 972 form of the payload block (B6). This is accomplished by a single 973 BIB (B2) with multiple targets. A single BIB is used in this case 974 because all three targets share a security source, security 975 context, and security context parameters. Had this not been the 976 case, multiple BIBs could have been added instead. 978 o Confidentiality for the first extension block (B4). This is 979 accomplished by a BCB (B3). Once applied, the block-type- 980 specific-data field of extension block B4 is encrypted. The BCB 981 MUST hold an authentication tag for the cipher text either in the 982 cipher text that now populates the first extension block or as a 983 security result in the BCB itself, depending on which security 984 context is used to form the BCB. A plain text integrity signature 985 may also exist as a security result in the BCB if one is provided 986 by the selected confidentiality security context. 988 3.11.2. Example 2: Adding More Security At A New Node 990 Consider that the bundle as it is illustrated in Figure 3 is now 991 received by a waypoint node that wishes to encrypt the second 992 extension block and the bundle payload. The waypoint security policy 993 is to allow existing BIBs for these blocks to persist, as they may be 994 required as part of the security policy at the bundle destination. 996 The resultant bundle is illustrated in Figure 4 and the security 997 actions are described below. Note that block IDs provided here are 998 ordered solely for the purpose of this example and not meant to 999 impose an ordering for block creation. The ordering of blocks added 1000 to a bundle MUST always be in compliance with [I-D.ietf-dtn-bpbis]. 1002 Block in Bundle ID 1003 +==========================================+====+ 1004 | Primary Block | B1 | 1005 +------------------------------------------+----+ 1006 | BIB | B2 | 1007 | OP(bib-integrity, targets=B1) | | 1008 +------------------------------------------+----+ 1009 | BIB (encrypted) | B7 | 1010 | OP(bib-integrity, targets=B5, B6) | | 1011 +------------------------------------------+----+ 1012 | BCB | B8 | 1013 | OP(bcb-confidentiality,targets=B5,B6,B7) | | 1014 +------------------------------------------+----+ 1015 | BCB | B3 | 1016 | OP(bcb-confidentiality, target=B4) | | 1017 +------------------------------------------+----+ 1018 | Extension Block (encrypted) | B4 | 1019 +------------------------------------------+----+ 1020 | Extension Block (encrypted) | B5 | 1021 +------------------------------------------+----+ 1022 | Payload Block (encrypted) | B6 | 1023 +------------------------------------------+----+ 1025 Figure 4: Security At Bundle Forwarding 1027 The following security actions were applied to this bundle prior to 1028 its forwarding from the waypoint node. 1030 o Since the waypoint node wishes to encrypt the block-type-specific- 1031 data field of blocks B5 and B6, it MUST also encrypt the block- 1032 type-specific-data field of the BIBs providing plain text 1033 integrity over those blocks. However, BIB B2 could not be 1034 encrypted in its entirety because it also held a signature for the 1035 primary block (B1). Therefore, a new BIB (B7) is created and 1036 security results associated with B5 and B6 are moved out of BIB B2 1037 and into BIB B7. 1039 o Now that there is no longer confusion of which plain text 1040 integrity signatures must be encrypted, a BCB is added to the 1041 bundle with the security targets being the second extension block 1042 (B5) and the payload (B6) as well as the newly created BIB holding 1043 their plain text integrity signatures (B7). A single new BCB is 1044 used in this case because all three targets share a security 1045 source, security context, and security context parameters. Had 1046 this not been the case, multiple BCBs could have been added 1047 instead. 1049 4. Canonical Forms 1051 Security services require consistency and determinism in how 1052 information is presented to cipher suites at security sources, 1053 verifiers, and acceptors. For example, integrity services require 1054 that the same target information (e.g., the same bits in the same 1055 order) is provided to the cipher suite when generating an original 1056 signature and when validating a signature. Canonicalization 1057 algorithms transcode the contents of a security target into a 1058 canonical form. 1060 Canonical forms are used to generate input to a security context for 1061 security processing at a BP node. If the values of a security target 1062 are unchanged, then the canonical form of that target will be the 1063 same even if the encoding of those values for wire transmission is 1064 different. 1066 BPSec operates on data fields within bundle blocks (e.g., the block- 1067 type-specific-data field). In their canonical form, these fields 1068 MUST include their own CBOR encoding and MUST NOT include any other 1069 encapsulating CBOR encoding. For example, the canonical form of the 1070 block-type-specific-data field is a CBOR byte string existing within 1071 the CBOR array containing the fields of the extension block. The 1072 entire CBOR byte string is considered the canonical block-type- 1073 specific-data field. The CBOR array framing is not considered part 1074 of the field. 1076 The canonical form of the primary block is as specified in 1077 [I-D.ietf-dtn-bpbis] with the following constraint. 1079 o CBOR values from the primary block MUST be canonicalized using the 1080 rules for Canonical CBOR, as specified in [RFC7049]. Canonical 1081 CBOR generally requires that integers and type lengths are encoded 1082 to be as small as possible, that map values be sorted, and that 1083 indefinite-length items be made into definite-length items. 1085 All non-primary blocks share the same block structure and are 1086 canonicalized as specified in [I-D.ietf-dtn-bpbis] with the following 1087 constraints. 1089 o CBOR values from the non-primary block MUST be canonicalized using 1090 the rules for Canonical CBOR, as specified in [RFC7049]. 1092 o Only the block-type-specific-data field may be provided to a 1093 cipher suite for encryption as part of a confidentiality security 1094 service. Other fields within a non-primary-block MUST NOT be 1095 encrypted or decrypted and MUST NOT be included in the canonical 1096 form used by the cipher suite for encryption and decryption. 1097 These other fields MAY have an integrity protection mechanism 1098 applied to them by treating them as associated authenticated data. 1100 o Reserved and unassigned flags in the block processing control 1101 flags field MUST be set to 0 in a canonical form as it is not 1102 known if those flags will change in transit. 1104 Security contexts MAY define their own canonicalization algorithms 1105 and require the use of those algorithms over the ones provided in 1106 this specification. In the event of conflicting canonicalization 1107 algorithms, algorithms defined in a security context take precedence 1108 over this specification when constructing canonical forms for that 1109 security context. 1111 5. Security Processing 1113 This section describes the security aspects of bundle processing. 1115 5.1. Bundles Received from Other Nodes 1117 Security blocks must be processed in a specific order when received 1118 by a BP node. The processing order is as follows. 1120 o When BIBs and BCBs share a security target, BCBs MUST be evaluated 1121 first and BIBs second. 1123 5.1.1. Receiving BCBs 1125 If a received bundle contains a BCB, the receiving node MUST 1126 determine whether it is the security acceptor for any of the security 1127 operations in the BCB. If so, the node MUST process those operations 1128 and remove any operation-specific information from the BCB prior to 1129 delivering data to an application at the node or forwarding the 1130 bundle. If processing a security operation fails, the target SHALL 1131 be processed according to the security policy. A bundle status 1132 report indicating the failure MAY be generated. When all security 1133 operations for a BCB have been removed from the BCB, the BCB MUST be 1134 removed from the bundle. 1136 If the receiving node is the destination of the bundle, the node MUST 1137 decrypt any BCBs remaining in the bundle. If the receiving node is 1138 not the destination of the bundle, the node MUST process the BCB if 1139 directed to do so as a matter of security policy. 1141 If the security policy of a node specifies that a node should have 1142 applied confidentiality to a specific security target and no such BCB 1143 is present in the bundle, then the node MUST process this security 1144 target in accordance with the security policy. It is RECOMMENDED 1145 that the node remove the security target from the bundle because the 1146 confidentiality (and possibly the integrity) of the security target 1147 cannot be guaranteed. If the removed security target is the payload 1148 block, the bundle MUST be discarded. 1150 If an encrypted payload block cannot be decrypted (i.e., the cipher 1151 text cannot be authenticated), then the bundle MUST be discarded and 1152 processed no further. If an encrypted security target other than the 1153 payload block cannot be decrypted then the associated security target 1154 and all security blocks associated with that target MUST be discarded 1155 and processed no further. In both cases, requested status reports 1156 (see [I-D.ietf-dtn-bpbis]) MAY be generated to reflect bundle or 1157 block deletion. 1159 When a BCB is decrypted, the recovered plain text for each security 1160 target MUST replace the cipher text in each of the security targets' 1161 block-type-specific-data fields. If the plain text is of different 1162 size than the cipher text, the CBOR byte string framing of this field 1163 must be updated to ensure this field remains a valid CBOR byte 1164 string. The length of the recovered plain text is known by the 1165 decrypting security context. 1167 If a BCB contains multiple security operations, each operation 1168 processed by the node MUST be treated as if the security operation 1169 has been represented by a single BCB with a single security operation 1170 for the purposes of report generation and policy processing. 1172 5.1.2. Receiving BIBs 1174 If a received bundle contains a BIB, the receiving node MUST 1175 determine whether it is the security acceptor for any of the security 1176 operations in the BIB. If so, the node MUST process those operations 1177 and remove any operation-specific information from the BIB prior to 1178 delivering data to an application at the node or forwarding the 1179 bundle. If processing a security operation fails, the target SHALL 1180 be processed according to the security policy. A bundle status 1181 report indicating the failure MAY be generated. When all security 1182 operations for a BIB have been removed from the BIB, the BIB MUST be 1183 removed from the bundle. 1185 A BIB MUST NOT be processed if the security target of the BIB is also 1186 the security target of a BCB in the bundle. Given the order of 1187 operations mandated by this specification, when both a BIB and a BCB 1188 share a security target, it means that the security target must have 1189 been encrypted after it was integrity signed and, therefore, the BIB 1190 cannot be verified until the security target has been decrypted by 1191 processing the BCB. 1193 If the security policy of a node specifies that a node should have 1194 applied integrity to a specific security target and no such BIB is 1195 present in the bundle, then the node MUST process this security 1196 target in accordance with the security policy. It is RECOMMENDED 1197 that the node remove the security target from the bundle if the 1198 security target is not the payload or primary block. If the security 1199 target is the payload or primary block, the bundle MAY be discarded. 1200 This action can occur at any node that has the ability to verify an 1201 integrity signature, not just the bundle destination. 1203 If a receiving node is not the security acceptor of a security 1204 operation in a BIB it MAY attempt to verify the security operation 1205 anyway to prevent forwarding corrupt data. If the verification 1206 fails, the node SHALL process the security target in accordance to 1207 local security policy. It is RECOMMENDED that if a payload integrity 1208 check fails at a waypoint that it is processed in the same way as if 1209 the check fails at the bundle destination. If the check passes, the 1210 node MUST NOT remove the security operation from the BIB prior to 1211 forwarding. 1213 If a BIB contains multiple security operations, each operation 1214 processed by the node MUST be treated as if the security operation 1215 has been represented by a single BIB with a single security operation 1216 for the purposes of report generation and policy processing. 1218 5.2. Bundle Fragmentation and Reassembly 1220 If it is necessary for a node to fragment a bundle payload, and 1221 security services have been applied to that bundle, the fragmentation 1222 rules described in [I-D.ietf-dtn-bpbis] MUST be followed. As defined 1223 there and summarized here for completeness, only the payload block 1224 can be fragmented; security blocks, like all extension blocks, can 1225 never be fragmented. 1227 Due to the complexity of payload block fragmentation, including the 1228 possibility of fragmenting payload block fragments, integrity and 1229 confidentiality operations are not to be applied to a bundle 1230 representing a fragment. Specifically, a BCB or BIB MUST NOT be 1231 added to a bundle if the "Bundle is a Fragment" flag is set in the 1232 Bundle Processing Control Flags field. 1234 Security processing in the presence of payload block fragmentation 1235 may be handled by other mechanisms outside of the BPSec protocol or 1236 by applying BPSec blocks in coordination with an encapsulation 1237 mechanism. A node should apply any confidentiality protection prior 1238 to performing any fragmentation. 1240 6. Key Management 1242 There exist a myriad of ways to establish, communicate, and otherwise 1243 manage key information in a DTN. Certain DTN deployments might 1244 follow established protocols for key management whereas other DTN 1245 deployments might require new and novel approaches. BPSec assumes 1246 that key management is handled as a separate part of network 1247 management and this specification neither defines nor requires a 1248 specific key management strategy. 1250 7. Security Policy Considerations 1252 When implementing BPSec, several policy decisions must be considered. 1253 This section describes key policies that affect the generation, 1254 forwarding, and receipt of bundles that are secured using this 1255 specification. No single set of policy decisions is envisioned to 1256 work for all secure DTN deployments. 1258 o If a bundle is received that contains combinations of security 1259 operations that are disallowed by this specification the BPA must 1260 determine how to handle the bundle. The bundle may be discarded, 1261 the block affected by the security operation may be discarded, or 1262 one security operation may be favored over another. 1264 o BPAs in the network must understand what security operations they 1265 should apply to bundles. This decision may be based on the source 1266 of the bundle, the destination of the bundle, or some other 1267 information related to the bundle. 1269 o If a waypoint has been configured to add a security operation to a 1270 bundle, and the received bundle already has the security operation 1271 applied, then the receiver must understand what to do. The 1272 receiver may discard the bundle, discard the security target and 1273 associated BPSec blocks, replace the security operation, or some 1274 other action. 1276 o It is RECOMMENDED that security operations be applied to every 1277 block in a bundle and that the default behavior of a bundle agent 1278 is to use the security services defined in this specification. 1279 Designers should only deviate from the use of security operations 1280 when the deviation can be justified - such as when doing so causes 1281 downstream errors when processing blocks whose contents must be 1282 inspected or changed at one or more hops along the path. 1284 o BCB security contexts can alter the size of extension blocks and 1285 the payload block. Security policy SHOULD consider how changes to 1286 the size of a block could negatively effect bundle processing 1287 (e.g., calculating storage needs and scheduling transmission 1288 times). 1290 o Adding a BIB to a security target that has already been encrypted 1291 by a BCB is not allowed. If this condition is likely to be 1292 encountered, there are (at least) three possible policies that 1293 could handle this situation. 1295 1. At the time of encryption, a security context can be selected 1296 which computes a plain text integrity-protection mechanism 1297 that is included as a security context result field. 1299 2. The encrypted block may be replicated as a new block with a 1300 new block number and given integrity protection. 1302 3. An encapsulation scheme may be applied to encapsulate the 1303 security target (or the entire bundle) such that the 1304 encapsulating structure is, itself, no longer the security 1305 target of a BCB and may therefore be the security target of a 1306 BIB. 1308 o Security policy SHOULD address whether cipher suites whose cipher 1309 text is larger than the initial plain text are permitted and, if 1310 so, for what types of blocks. Changing the size of a block may 1311 cause processing difficulties for networks that calculate block 1312 offsets into bundles or predict transmission times or storage 1313 availability as a function of bundle size. In other cases, 1314 changing the size of a payload as part of encryption has no 1315 significant impact. 1317 7.1. Security Reason Codes 1319 Bundle protocol agents (BPAs) must process blocks and bundles in 1320 accordance with both BP policy and BPSec policy. The decision to 1321 receive, forward, deliver, or delete a bundle may be communicated to 1322 the report-to address of the bundle, in the form of a status report, 1323 as a method of tracking the progress of the bundle through the 1324 network. The status report for a bundle may be augmented with a 1325 "reason code" explaining why the particular action was taken on the 1326 bundle. 1328 This section describes a set of reason codes associated with the 1329 security processing of a bundle. Security reason codes are assigned 1330 in accordance with Section 11.2. 1332 Missing Security Operation: 1333 This reason code indicates that a bundle was missing one or 1334 more required security operations. This reason code is 1335 typically used by a security verifier or security acceptor. 1337 Unknown Security Operation: 1338 This reason code indicates that one or more security operations 1339 present in a bundle cannot be understood by the security 1340 verifier or security acceptor for the operation. For example, 1341 this reason code may be used if a security block references an 1342 unknown security context identifier or security context 1343 parameter. This reason code should not be used for security 1344 operations for which the node is not a security verifier or 1345 security acceptor; there is no requirement that all nodes in a 1346 network understand all security contexts, security context 1347 parameters, and security services for every bundle in a 1348 network. 1350 Unexpected Security Operation: 1351 This reason code indicates that a receiving node is neither a 1352 security verifier nor a security acceptor for at least one 1353 security operation in a bundle. This reason code should not be 1354 seen as an error condition; not every node is a security 1355 verifier or security acceptor for every security operation in 1356 every bundle. In certain networks, this reason code may be 1357 useful in identifying misconfigurations of security policy. 1359 Failed Security Operation: 1360 This reason code indicates that one or more security operations 1361 in a bundle failed to process as expected for reasons other 1362 than misconfiguration. This may occur when a security-source 1363 is unable to add a security block to a bundle. This may occur 1364 if the target of a security operation fails to verify using the 1365 defined security context at a security verifier. This may also 1366 occur if a security operation fails to be processed without 1367 error at a security acceptor. 1369 Conflicting Security Operations: 1370 This reason code indicates that two or more security operations 1371 in a bundle are not conformant with the BPSec specification and 1372 that security processing was unable to proceed because of a 1373 BPSec protocol violation. 1375 8. Security Considerations 1377 Given the nature of DTN applications, it is expected that bundles may 1378 traverse a variety of environments and devices which each pose unique 1379 security risks and requirements on the implementation of security 1380 within BPSec. For these reasons, it is important to introduce key 1381 threat models and describe the roles and responsibilities of the 1382 BPSec protocol in protecting the confidentiality and integrity of the 1383 data against those threats. This section provides additional 1384 discussion on security threats that BPSec will face and describes how 1385 BPSec security mechanisms operate to mitigate these threats. 1387 The threat model described here is assumed to have a set of 1388 capabilities identical to those described by the Internet Threat 1389 Model in [RFC3552], but the BPSec threat model is scoped to 1390 illustrate threats specific to BPSec operating within DTN 1391 environments and therefore focuses on on-path-attackers (OPAs). In 1392 doing so, it is assumed that the DTN (or significant portions of the 1393 DTN) are completely under the control of an attacker. 1395 8.1. Attacker Capabilities and Objectives 1397 BPSec was designed to protect against OPA threats which may have 1398 access to a bundle during transit from its source, Alice, to its 1399 destination, Bob. An OPA node, Olive, is a non-cooperative node 1400 operating on the DTN between Alice and Bob that has the ability to 1401 receive bundles, examine bundles, modify bundles, forward bundles, 1402 and generate bundles at will in order to compromise the 1403 confidentiality or integrity of data within the DTN. There are three 1404 classes of OPA nodes which are differentiated based on their access 1405 to cryptographic material: 1407 o Unprivileged Node: Olive has not been provisioned within the 1408 secure environment and only has access to cryptographic material 1409 which has been publicly-shared. 1411 o Legitimate Node: Olive is within the secure environment and 1412 therefore has access to cryptographic material which has been 1413 provisioned to Olive (i.e., K_M) as well as material which has 1414 been publicly-shared. 1416 o Privileged Node: Olive is a privileged node within the secure 1417 environment and therefore has access to cryptographic material 1418 which has been provisioned to Olive, Alice and/or Bob (i.e. K_M, 1419 K_A, and/or K_B) as well as material which has been publicly- 1420 shared. 1422 If Olive is operating as a privileged node, this is tantamount to 1423 compromise; BPSec does not provide mechanisms to detect or remove 1424 Olive from the DTN or BPSec secure environment. It is up to the 1425 BPSec implementer or the underlying cryptographic mechanisms to 1426 provide appropriate capabilities if they are needed. It should also 1427 be noted that if the implementation of BPSec uses a single set of 1428 shared cryptographic material for all nodes, a legitimate node is 1429 equivalent to a privileged node because K_M == K_A == K_B. For this 1430 reason, sharing cryptographic material in this way is not 1431 recommended. 1433 A special case of the legitimate node is when Olive is either Alice 1434 or Bob (i.e., K_M == K_A or K_M == K_B). In this case, Olive is able 1435 to impersonate traffic as either Alice or Bob, respectively, which 1436 means that traffic to and from that node can be decrypted and 1437 encrypted, respectively. Additionally, messages may be signed as 1438 originating from one of the endpoints. 1440 8.2. Attacker Behaviors and BPSec Mitigations 1442 8.2.1. Eavesdropping Attacks 1444 Once Olive has received a bundle, she is able to examine the contents 1445 of that bundle and attempt to recover any protected data or 1446 cryptographic keying material from the blocks contained within. The 1447 protection mechanism that BPSec provides against this action is the 1448 BCB, which encrypts the contents of its security target, providing 1449 confidentiality of the data. Of course, it should be assumed that 1450 Olive is able to attempt offline recovery of encrypted data, so the 1451 cryptographic mechanisms selected to protect the data should provide 1452 a suitable level of protection. 1454 When evaluating the risk of eavesdropping attacks, it is important to 1455 consider the lifetime of bundles on a DTN. Depending on the network, 1456 bundles may persist for days or even years. Long-lived bundles imply 1457 that the data exists in the network for a longer period of time and, 1458 thus, there may be more opportunities to capture those bundles. 1459 Additionally, bundles that are long-lived imply that the information 1460 stored within them may remain relevant and sensitive for long enough 1461 that, once captured, there is sufficient time to crack encryption 1462 associated with the bundle. If a bundle does persist on the network 1463 for years and the cipher suite used for a BCB provides inadequate 1464 protection, Olive may be able to recover the protected data either 1465 before that bundle reaches its intended destination or before the 1466 information in the bundle is no longer considered sensitive. 1468 NOTE: Olive is not limited by the bundle lifetime and may retain a 1469 given bundle indefinitely. 1471 NOTE: Irrespective of whether BPSec is used, traffic analysis will be 1472 possible. 1474 8.2.2. Modification Attacks 1476 As a node participating in the DTN between Alice and Bob, Olive will 1477 also be able to modify the received bundle, including non-BPSec data 1478 such as the primary block, payload blocks, or block processing 1479 control flags as defined in [I-D.ietf-dtn-bpbis]. Olive will be able 1480 to undertake activities which include modification of data within the 1481 blocks, replacement of blocks, addition of blocks, or removal of 1482 blocks. Within BPSec, both the BIB and BCB provide integrity 1483 protection mechanisms to detect or prevent data manipulation attempts 1484 by Olive. 1486 The BIB provides that protection to another block which is its 1487 security target. The cryptographic mechanisms used to generate the 1488 BIB should be strong against collision attacks and Olive should not 1489 have access to the cryptographic material used by the originating 1490 node to generate the BIB (e.g., K_A). If both of these conditions 1491 are true, Olive will be unable to modify the security target or the 1492 BIB and lead Bob to validate the security target as originating from 1493 Alice. 1495 Since BPSec security operations are implemented by placing blocks in 1496 a bundle, there is no in-band mechanism for detecting or correcting 1497 certain cases where Olive removes blocks from a bundle. If Olive 1498 removes a BCB, but keeps the security target, the security target 1499 remains encrypted and there is a possibility that there may no longer 1500 be sufficient information to decrypt the block at its destination. 1501 If Olive removes both a BCB (or BIB) and its security target there is 1502 no evidence left in the bundle of the security operation. Similarly, 1503 if Olive removes the BIB but not the security target there is no 1504 evidence left in the bundle of the security operation. In each of 1505 these cases, the implementation of BPSec must be combined with policy 1506 configuration at endpoints in the network which describe the expected 1507 and required security operations that must be applied on transmission 1508 and are expected to be present on receipt. This or other similar 1509 out-of-band information is required to correct for removal of 1510 security information in the bundle. 1512 A limitation of the BIB may exist within the implementation of BIB 1513 validation at the destination node. If Olive is a legitimate node 1514 within the DTN, the BIB generated by Alice with K_A can be replaced 1515 with a new BIB generated with K_M and forwarded to Bob. If Bob is 1516 only validating that the BIB was generated by a legitimate user, Bob 1517 will acknowledge the message as originating from Olive instead of 1518 Alice. Validating a BIB indicates only that the BIB was generated by 1519 a holder of the relevant key; it does not provide any guarantee that 1520 the bundle or block was created by the same entity. In order to 1521 provide verifiable integrity checks BCB should require an encryption 1522 scheme that is Indistinguishable under adaptive Chosen Ciphertext 1523 Attack (IND-CCA2) secure. Such an encryption scheme will guard 1524 against signature substitution attempts by Olive. In this case, 1525 Alice creates a BIB with the protected data block as the security 1526 target and then creates a BCB with both the BIB and protected data 1527 block as its security targets. 1529 8.2.3. Topology Attacks 1531 If Olive is in a OPA position within the DTN, she is able to 1532 influence how any bundles that come to her may pass through the 1533 network. Upon receiving and processing a bundle that must be routed 1534 elsewhere in the network, Olive has three options as to how to 1535 proceed: not forward the bundle, forward the bundle as intended, or 1536 forward the bundle to one or more specific nodes within the network. 1538 Attacks that involve re-routing the packets throughout the network 1539 are essentially a special case of the modification attacks described 1540 in this section where the attacker is modifying fields within the 1541 primary block of the bundle. Given that BPSec cannot encrypt the 1542 contents of the primary block, alternate methods must be used to 1543 prevent this situation. These methods may include requiring BIBs for 1544 primary blocks, using encapsulation, or otherwise strategically 1545 manipulating primary block data. The specifics of any such 1546 mitigation technique are specific to the implementation of the 1547 deploying network and outside of the scope of this document. 1549 Furthermore, routing rules and policies may be useful in enforcing 1550 particular traffic flows to prevent topology attacks. While these 1551 rules and policies may utilize some features provided by BPSec, their 1552 definition is beyond the scope of this specification. 1554 8.2.4. Message Injection 1556 Olive is also able to generate new bundles and transmit them into the 1557 DTN at will. These bundles may either be copies or slight 1558 modifications of previously-observed bundles (i.e., a replay attack) 1559 or entirely new bundles generated based on the Bundle Protocol, 1560 BPSec, or other bundle-related protocols. With these attacks Olive's 1561 objectives may vary, but may be targeting either the bundle protocol 1562 or application-layer protocols conveyed by the bundle protocol. The 1563 target could also be the storage and compute of the nodes running the 1564 bundle or application layer protocols (e.g., a denial of service to 1565 flood on the storage of the store-and-forward mechanism; or compute 1566 which would process the packets and perhaps prevent other 1567 activities). 1569 BPSec relies on cipher suite capabilities to prevent replay or forged 1570 message attacks. A BCB used with appropriate cryptographic 1571 mechanisms may provide replay protection under certain circumstances. 1572 Alternatively, application data itself may be augmented to include 1573 mechanisms to assert data uniqueness and then protected with a BIB, a 1574 BCB, or both along with other block data. In such a case, the 1575 receiving node would be able to validate the uniqueness of the data. 1577 For example, a BIB may be used to validate the integrity of a 1578 bundle's primary block, which includes a timestamp and lifetime for 1579 the bundle. If a bundle is replayed outside of its lifetime, then 1580 the replay attack will fail as the bundle will be discarded. 1581 Similarly, additional blocks such as the Bundle Age may be signed and 1582 validated to identify replay attacks. Finally, security context 1583 parameters within BIB and BCB blocks may include anti-replay 1584 mechanisms such as session identifiers, nonces, and dynamic passwords 1585 as supported by network characteristics. 1587 9. Security Context Considerations 1589 9.1. Mandating Security Contexts 1591 Because of the diversity of networking scenarios and node 1592 capabilities that may utilize BPSec there is a risk that a single 1593 security context mandated for every possible BPSec implementation is 1594 not feasible. For example, a security context appropriate for a 1595 resource-constrained node with limited connectivity may be 1596 inappropriate for use in a well-resourced, well connected node. 1598 This does not mean that the use of BPSec in a particular network is 1599 meant to be used without security contexts for interoperability and 1600 default behavior. Network designers must identify the minimal set of 1601 security contexts necessary for functions in their network. For 1602 example, a default set of security contexts could be created for use 1603 over the terrestrial Internet and required by any BPSec 1604 implementation communicating over the terrestrial Internet. 1606 To ensure interoperability among various implementations, all BPSec 1607 implementations MUST support at least the current IETF standards- 1608 track mandatory security context(s). As of this writing, that BCP 1609 mandatory security context is specified in 1610 [I-D.ietf-dtn-bpsec-interop-sc], but the mandatory security 1611 context(s) might change over time in accordance with usual IETF 1612 processes. Such changes are likely to occur in the future if/when 1613 flaws are discovered in the applicable cryptographic algorithms, for 1614 example. 1616 Additionally, BPsec implementations need to support the security 1617 contexts which are specified and/or used by the BP networks in which 1618 they are deployed. 1620 If a node serves as a gateway amongst two or more networks, the BPSec 1621 implementation at that node needs to support the union of security 1622 contexts mandated in those networks. 1624 BPSec has been designed to allow for a diversity of security contexts 1625 and for new contexts to be defined over time. The use of different 1626 security contexts does not change the BPSec protocol itself and the 1627 definition of new security contexts MUST adhere to the requirements 1628 of such contexts as presented in this section and generally in this 1629 specification. 1631 Implementors should monitor the state of security context 1632 specifications to check for future updates and replacement. 1634 9.2. Identification and Configuration 1636 Security blocks uniquely identify the security context to be used in 1637 the processing of their security services. The security context for 1638 a security block MUST be uniquely identifiable and MAY use parameters 1639 for customization. 1641 To reduce the number of security contexts used in a network, security 1642 context designers should make security contexts customizable through 1643 the definition of security context parameters. For example, a single 1644 security context could be associated with a single cipher suite and 1645 security context parameters could be used to configure the use of 1646 this security context with different key lengths and different key 1647 management options without needing to define separate security 1648 contexts for each possible option. 1650 A single security context may be used in the application of more than 1651 one security service. This means that a security context identifier 1652 MAY be used with a BIB, with a BCB, or with any other BPSec-compliant 1653 security block. The definition of a security context MUST identify 1654 which security services may be used with the security context, how 1655 security context parameters are interpreted as a function of the 1656 security operation being supported, and which security results are 1657 produced for each security service. 1659 Network operators must determine the number, type, and configuration 1660 of security contexts in a system. Networks with rapidly changing 1661 configurations may define relatively few security contexts with each 1662 context customized with multiple parameters. For networks with more 1663 stability, or an increased need for confidentiality, a larger number 1664 of contexts can be defined with each context supporting few, if any, 1665 parameters. 1667 Security Context Examples 1669 +------------+------------+-----------------------------------------+ 1670 | Context | Parameters | Definition | 1671 | Type | | | 1672 +------------+------------+-----------------------------------------+ 1673 | Key | Encrypted | AES-GCM-256 cipher suite with provided | 1674 | Exchange | Key, IV | ephemeral key encrypted with a | 1675 | AES | | predetermined key encryption key and | 1676 | | | clear text initialization vector. | 1677 | Pre-shared | IV | AES-GCM-256 cipher suite with | 1678 | Key AES | | predetermined key and predetermined | 1679 | | | key rotation policy. | 1680 | Out of | None | AES-GCM-256 cipher suite with all info | 1681 | Band AES | | predetermined. | 1682 +------------+------------+-----------------------------------------+ 1684 Table 1 1686 9.3. Authorship 1688 Developers or implementers should consider the diverse performance 1689 and conditions of networks on which the Bundle Protocol (and 1690 therefore BPSec) will operate. Specifically, the delay and capacity 1691 of delay-tolerant networks can vary substantially. Developers should 1692 consider these conditions to better describe the conditions when 1693 those contexts will operate or exhibit vulnerability, and selection 1694 of these contexts for implementation should be made with 1695 consideration for this reality. There are key differences that may 1696 limit the opportunity for a security context to leverage existing 1697 cipher suites and technologies that have been developed for use in 1698 traditional, more reliable networks: 1700 o Data Lifetime: Depending on the application environment, bundles 1701 may persist on the network for extended periods of time, perhaps 1702 even years. Cryptographic algorithms should be selected to ensure 1703 protection of data against attacks for a length of time reasonable 1704 for the application. 1706 o One-Way Traffic: Depending on the application environment, it is 1707 possible that only a one-way connection may exist between two 1708 endpoints, or if a two-way connection does exist, the round- trip 1709 time may be extremely large. This may limit the utility of 1710 session key generation mechanisms, such as Diffie-Hellman, as a 1711 two-way handshake may not be feasible or reliable. 1713 o Opportunistic Access: Depending on the application environment, a 1714 given endpoint may not be guaranteed to be accessible within a 1715 certain amount of time. This may make asymmetric cryptographic 1716 architectures which rely on a key distribution center or other 1717 trust center impractical under certain conditions. 1719 When developing security contexts for use with BPSec, the following 1720 information SHOULD be considered for inclusion in these 1721 specifications. 1723 o Security Context Parameters. Security contexts MUST define their 1724 parameter Ids, the data types of those parameters, and their CBOR 1725 encoding. 1727 o Security Results. Security contexts MUST define their security 1728 result Ids, the data types of those results, and their CBOR 1729 encoding. 1731 o New Canonicalizations. Security contexts may define new 1732 canonicalization algorithms as necessary. 1734 o Cipher-Text Size. Security contexts MUST state whether their 1735 associated cipher suites generate cipher text (to include any 1736 authentication information) that is of a different size than the 1737 input plain text. 1739 If a security context does not wish to alter the size of the plain 1740 text it should place overflow bytes and authentication tags in 1741 security result fields. 1743 o Block Header Information. Security contexts SHOULD include block 1744 header information that is considered to be immutable for the 1745 block. This information MAY include the block type code, block 1746 number, CRC Type and CRC field (if present or if missing and 1747 unlikely to be added later), and possibly certain block processing 1748 control flags. Designers should input these fields as additional 1749 data for integrity protection when these fields are expected to 1750 remain unchanged over the path the block will take from the 1751 security source to the security acceptor. Security contexts 1752 considering block header information MUST describe expected 1753 behavior when these fields fail their integrity verification. 1755 10. Defining Other Security Blocks 1757 Other security blocks (OSBs) may be defined and used in addition to 1758 the security blocks identified in this specification. Both the usage 1759 of BIB, BCB, and any future OSBs can co-exist within a bundle and can 1760 be considered in conformance with BPSec if each of the following 1761 requirements are met by any future identified security blocks. 1763 o Other security blocks (OSBs) MUST NOT reuse any enumerations 1764 identified in this specification, to include the block type codes 1765 for BIB and BCB. 1767 o An OSB definition MUST state whether it can be the target of a BIB 1768 or a BCB. The definition MUST also state whether the OSB can 1769 target a BIB or a BCB. 1771 o An OSB definition MUST provide a deterministic processing order in 1772 the event that a bundle is received containing BIBs, BCBs, and 1773 OSBs. This processing order MUST NOT alter the BIB and BCB 1774 processing orders identified in this specification. 1776 o An OSB definition MUST provide a canonicalization algorithm if the 1777 default non-primary-block canonicalization algorithm cannot be 1778 used to generate a deterministic input for a cipher suite. This 1779 requirement can be waived if the OSB is defined so as to never be 1780 the security target of a BIB or a BCB. 1782 o An OSB definition MUST NOT require any behavior of a BPSEC-BPA 1783 that is in conflict with the behavior identified in this 1784 specification. In particular, the security processing 1785 requirements imposed by this specification must be consistent 1786 across all BPSEC-BPAs in a network. 1788 o The behavior of an OSB when dealing with fragmentation must be 1789 specified and MUST NOT lead to ambiguous processing states. In 1790 particular, an OSB definition should address how to receive and 1791 process an OSB in a bundle fragment that may or may not also 1792 contain its security target. An OSB definition should also 1793 address whether an OSB may be added to a bundle marked as a 1794 fragment. 1796 Additionally, policy considerations for the management, monitoring, 1797 and configuration associated with blocks SHOULD be included in any 1798 OSB definition. 1800 NOTE: The burden of showing compliance with processing rules is 1801 placed upon the specifications defining new security blocks and the 1802 identification of such blocks shall not, alone, require maintenance 1803 of this specification. 1805 11. IANA Considerations 1807 This specification includes fields requiring registries managed by 1808 IANA. 1810 11.1. Bundle Block Types 1812 This specification allocates two block types from the existing 1813 "Bundle Block Types" registry defined in [RFC6255]. 1815 Additional Entries for the Bundle Block-Type Codes Registry: 1817 +-------+-----------------------------+---------------+ 1818 | Value | Description | Reference | 1819 +-------+-----------------------------+---------------+ 1820 | TBA | Block Integrity Block | This document | 1821 | TBA | Block Confidentiality Block | This document | 1822 +-------+-----------------------------+---------------+ 1824 Table 2 1826 The Bundle Block Types namespace notes whether a block type is meant 1827 for use in BP version 6, BP version 7, or both. The two block types 1828 defined in this specification are meant for use with BP version 7. 1830 11.2. Bundle Status Report Reason Codes 1832 This specification allocates five reason codes from the existing 1833 "Bundle Status Report Reason Codes" registry defined in [RFC6255]. 1835 Additional Entries for the Bundle Status Report Reason Codes 1836 Registry: 1838 +---------+-------+-----------------------+-------------------------+ 1839 | BP | Value | Description | Reference | 1840 | Version | | | | 1841 +---------+-------+-----------------------+-------------------------+ 1842 | 7 | TBD | Missing Security | This document, Section | 1843 | | | Operation | Section 7.1 | 1844 | 7 | TBD | Unknown Security | This document, Section | 1845 | | | Operation | Section 7.1 | 1846 | 7 | TBD | Unexpected Security | This document, Section | 1847 | | | Operation | Section 7.1 | 1848 | 7 | TBD | Failed Security | This document, Section | 1849 | | | Operation | Section 7.1 | 1850 | 7 | TBD | Conflicting Security | This document, Section | 1851 | | | Operation | Section 7.1 | 1852 +---------+-------+-----------------------+-------------------------+ 1854 11.3. Security Context Identifiers 1856 BPSec has a Security Context Identifier field for which IANA is 1857 requested to create and maintain a new registry named "BPSec Security 1858 Context Identifiers". Initial values for this registry are given 1859 below. 1861 The registration policy for this registry is: Specification Required. 1863 The value range is: signed 16-bit integer. 1865 BPSec Security Context Identifier Registry 1867 +-------+-------------+---------------+ 1868 | Value | Description | Reference | 1869 +-------+-------------+---------------+ 1870 | < 0 | Reserved | This document | 1871 | 0 | Reserved | This document | 1872 +-------+-------------+---------------+ 1874 Table 3 1876 Negative security context identifiers are reserved for local/site- 1877 specific uses. The use of 0 as a security context identifier is for 1878 non-operational testing purposes only. 1880 12. References 1882 12.1. Normative References 1884 [I-D.ietf-dtn-bpbis] 1885 Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol 1886 Version 7", draft-ietf-dtn-bpbis-28 (work in progress), 1887 October 2020. 1889 [I-D.ietf-dtn-bpsec-interop-sc] 1890 Birrane, E., "BPSec Default Security Contexts", draft- 1891 ietf-dtn-bpsec-interop-sc-02 (work in progress), November 1892 2020. 1894 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1895 Requirement Levels", BCP 14, RFC 2119, 1896 DOI 10.17487/RFC2119, March 1997, 1897 . 1899 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 1900 Text on Security Considerations", BCP 72, RFC 3552, 1901 DOI 10.17487/RFC3552, July 2003, 1902 . 1904 [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol 1905 IANA Registries", RFC 6255, DOI 10.17487/RFC6255, May 1906 2011, . 1908 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 1909 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 1910 October 2013, . 1912 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1913 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1914 May 2017, . 1916 12.2. Informative References 1918 [I-D.birrane-dtn-sbsp] 1919 Birrane, E., Pierce-Mayer, J., and D. Iannicca, 1920 "Streamlined Bundle Security Protocol Specification", 1921 draft-birrane-dtn-sbsp-01 (work in progress), October 1922 2015. 1924 [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, 1925 R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant 1926 Networking Architecture", RFC 4838, DOI 10.17487/RFC4838, 1927 April 2007, . 1929 [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, 1930 "Bundle Security Protocol Specification", RFC 6257, 1931 DOI 10.17487/RFC6257, May 2011, 1932 . 1934 Appendix A. Acknowledgements 1936 The following participants contributed technical material, use cases, 1937 and useful thoughts on the overall approach to this security 1938 specification: Scott Burleigh of the Jet Propulsion Laboratory, 1939 Angela Hennessy of the Laboratory for Telecommunications Sciences, 1940 and Amy Alford, Angela Dalton, and Cherita Corbett of the Johns 1941 Hopkins University Applied Physics Laboratory. 1943 Authors' Addresses 1945 Edward J. Birrane, III 1946 The Johns Hopkins University Applied 1947 Physics Laboratory 1948 11100 Johns Hopkins Rd. 1949 Laurel, MD 20723 1950 US 1952 Phone: +1 443 778 7423 1953 Email: Edward.Birrane@jhuapl.edu 1955 Kenneth McKeever 1956 The Johns Hopkins University Applied 1957 Physics Laboratory 1958 11100 Johns Hopkins Rd. 1959 Laurel, MD 20723 1960 US 1962 Phone: +1 443 778 2237 1963 Email: Ken.McKeever@jhuapl.edu