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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Pritikin 3 Internet-Draft M. Behringer 4 Intended status: Informational S. Bjarnason 5 Expires: July 19, 2014 Cisco 6 January 15, 2014 8 Bootstrapping Key Infrastructures 9 draft-pritikin-bootstrapping-keyinfrastructures-00 11 Abstract 13 This document specifies automated bootstrapping of an key 14 infrastructure using vendor installed IEEE 802.1AR manufacturing 15 installed certificates, in combination with a vendor based cloud 16 service. Before being authenticated, a new device has only link- 17 local connectivity, and does not require a routable address. When a 18 vendor cloud service is provided devices can be forced to join only 19 specific domains but for contrained environments we describe a 20 variety of options that allow bootstrapping to proceed. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on July 19, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 58 2. Architectural Overview . . . . . . . . . . . . . . . . . . . . 4 59 3. Operational Overview . . . . . . . . . . . . . . . . . . . . . 7 60 3.1. Instantiating the Domain Certification Authority . . . . . 7 61 3.2. Instantiating the Registrar . . . . . . . . . . . . . . . 7 62 3.3. Accepting New Entities . . . . . . . . . . . . . . . . . . 7 63 3.4. Operating the Network . . . . . . . . . . . . . . . . . . 8 64 4. Functional Overview . . . . . . . . . . . . . . . . . . . . . 8 65 4.1. Behavior of a new entity . . . . . . . . . . . . . . . . . 9 66 4.1.1. Proxy Discovery . . . . . . . . . . . . . . . . . . . 9 67 4.1.2. Receiving and accepting the Domain Identity . . . . . 10 68 4.1.3. Enrollment . . . . . . . . . . . . . . . . . . . . . . 11 69 4.1.4. After Enrollment . . . . . . . . . . . . . . . . . . . 11 70 4.2. Behavior of a proxy . . . . . . . . . . . . . . . . . . . 12 71 4.3. Behavior of the Registrar . . . . . . . . . . . . . . . . 12 72 4.3.1. Authenticating the Device . . . . . . . . . . . . . . 12 73 4.3.2. Accepting the Entity . . . . . . . . . . . . . . . . . 12 74 4.3.3. Claiming the new entity . . . . . . . . . . . . . . . 13 75 4.4. Behavior of the MASA Cloud Service . . . . . . . . . . . . 13 76 4.4.1. Issue Authorization Token and Log the event . . . . . 13 77 4.4.2. Retrieve Audit Entries from Log . . . . . . . . . . . 14 78 4.5. Leveraging the new key infrastructure / next steps . . . . 14 79 4.5.1. Network boundaries . . . . . . . . . . . . . . . . . . 14 80 5. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 14 81 5.1. EAP-EST . . . . . . . . . . . . . . . . . . . . . . . . . 15 82 5.2. Request bootstrap token . . . . . . . . . . . . . . . . . 15 83 5.3. Request MASA authorization token . . . . . . . . . . . . . 16 84 5.4. Request MASA authorization log . . . . . . . . . . . . . . 16 85 6. Reduced security operational modes . . . . . . . . . . . . . . 17 86 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 87 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 88 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 89 8.2. Informative References . . . . . . . . . . . . . . . . . . 18 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 92 1. Introduction 94 To literally "pull yourself up by the bootstraps" is an impossible 95 action. Similarly the secure establishment of a key infrastructure 96 without external help is also an impossibility. Today it is accepted 97 that the initial connections between nodes are insecure, until key 98 distribution is complete, or that domain-specific keying material is 99 pre-provisioned on each new device in a costly and non-scalable 100 manner. This document describes a zero-touch approach to 101 bootstrapping an entity by securing the initial distribution of key 102 material using third-party generic keying material, such as a 103 manufacturer installed IEEE 802.1AR certificate [IDevID], and a 104 corresponding third-party cloud service. 106 The two sides of an association being bootstrapped authenticate each 107 other and then determine appropriate authorization. This process is 108 described as four distinct steps between the existing domain and the 109 new entity being added: 111 o New entity authentication: "Who is this? What is its identity?" 112 o New entity authorization: "Is it mine? Do I want it? What are 113 the chances it has been compromised?" 114 o Domain authentication: "What is this domain's claimed identity?" 115 o Domain authorization: "Should I join it?" 117 A precise answer to these questions can not be obtained without 118 leveraging an established key infrastructure(s). The domain's 119 decisions are based on the new entity's authenticated identity, as 120 established by verification of previously installed credentials such 121 as a manufacturer installed IEEE 802.1AR certificate, and verified 122 back-end information such as a configured list of purchased devices 123 or communication with a trusted third-party. The new entity's 124 decisions are made according to verified communication with a trusted 125 third-party or in a strictly auditable fasion. 127 Optimal security is achieved with IEEE 802.1AR certificates on each 128 new entity, accompanied by a third-party cloud service for 129 verification. The concept also works with less requirements, but is 130 then less secure. A domain can choose to accept lower levels of 131 security when a trusted third-party is not available so that 132 bootstrapping proceeds even at the risk of reduced security. Only 133 the domain can make these decisions based on administrative input and 134 known behavior of the new entity. 136 The result of bootstrapping is that a domain specific key 137 infrastructure is deployed. Since IEEE 802.1AR PKI certificates are 138 used for identifying the new entity and the public key of the domain 139 identity is leveraged during communiciations with a cloud service, 140 which is itself authenticated using HTTPS, bootstrapping of a domain 141 specific Public Key Infrastructure (PKI) is fully described. 142 Sufficient agility to support bootstrapping alternative key 143 infrastructures (such as symmetric key solutions) is considered 144 although no such key infrastructure is described. 146 1.1. Terminology 148 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 149 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 150 "OPTIONAL" in this document are to be interpreted as described in 151 [RFC2119]. 153 The following terms are defined for clarity: 155 2. Architectural Overview 157 The logical elements of the bootstrapping framework are described in 158 this section. Figure 1 provides a simplified overview of the 159 components. Each component is logical and may be combined with other 160 components as necessary. 162 Factory components 163 . 164 . +------------+ 165 . | Factory CA | 166 . +------------+ 167 . | 168 . +------------+ 169 . | | 170 +--------------(provides)---------------------------| Factory | 171 | +---------->| | 172 | | . +------------+ 173 | V . 174 | +---------------+ . +------------+ 175 | | Orchestrator | . | MASA | 176 V +---------------+ . | Cloud | 177 +-------+ | . | Service | 178 | New | +------------+ +-----------+ . +------------+ 179 | Entity|<--L2-->| Proxy |<----->| | ....... ^ 180 | | +------------+ | | | 181 | | | Registrar | | 182 | | | | | 183 | |<--DHCP-->(L3 bootstrap) | | | 184 | | | | | 185 | |<-----L3---------------------( registrar )-----------+ 186 | | ( may proxy ) | 187 +-------+ +-----------+ 188 | 189 +----------------------------+ 190 ^ | Domain Certification | ^ 191 . | Authority | . 192 . +----------------------------+ . 193 . . 194 ......................................... 195 | 196 "domain" components 198 Figure 1 200 Domain: The set of entities that trust a common key infrastructure 201 trust anchor. 202 Domain CA: The domain Certification Authority (CA) optionally 203 provides certification functionalities to the domain entities. At 204 a minimum it provides certification funtionalities to the 205 Registrar and stores the trust anchor that defines the domain. 207 Domain Identity: The domain identity is the 160-bit SHA-1 hash of 208 the BIT STRING of the subjectPublicKey of the domain trust anchor 209 that is stored by the Domain CA. This is consistent with the 210 RFC5280 Certification Authority subject key identifier of the 211 Domain CA's self signed root certificate. (A string value bound 212 to the Domain CA's self signed root certificate subject and issuer 213 fields is often colloqually used as a humanized identity value but 214 during protocol discussions the more exact term as defined here is 215 used). 216 Orchestrator: Although bootstrapping of an individual device is 217 automated and requires zero administrative involvement 218 (particularly on the New Entity) the orchestrator drives general 219 operations of the domain. In simple deployments this might be a 220 single administrator ordering a new device from the Factory and 221 manually inputing a serial number from the bill-of-sale into a 222 Registrar. In a more complex environment this might be an 223 automated process that directs a hypervisor "Factory" to 224 instantiate a new virtual machine. 225 Factory: This instantiates the New Entity. For physical devices 226 this can be representative of third-party vendor manufacturing, 227 ordering and shipping process(es) that results in a physical 228 hardware device with an IEEE 802.1AR identity being drop shipped 229 to a destination domain for physical installation. In a virtual 230 machine environment this can be the virtual machine hypervisor 231 control software that initiates a virtual machine instance, in 232 which case the factory is a "virtual factory" and might be managed 233 by the domain itself. 234 Factory CA: This Certification Authority is leveraged by the Factory 235 to issue IEEE 802.1AR identities to each New Entity. For a 236 virtual factory it may be reasonable to assume the domain 237 certification authority is directly used but in a complex 238 environment it is assumed the Factory does not have direct access 239 to the Domain Certification Authority. 240 Registrar: A representative of the domain that is configured, 241 perhaps autonomically, to decide whether a new device is allowed 242 to join the domain. The administrator of the domain interfaces 243 with a Registrar to control this process. 244 New Entity: A new device or virtual machine or software component 245 that is not yet part of the domain. 246 Proxy: A domain entity that helps the New Entity join the domain. A 247 Proxy facilitates communication for devices that find themselves 248 in an environment where they are not provided L3 connectivity 249 until after they are validated as members of the domain. 250 MASA Cloud Service: A Manufacturer Authorized Signing Authority 251 (MASA) cloud service on the global Internet. At a minimum the 252 MASA provides a trusted repository for audit information 253 concerning privacy protected bootstrapping events. As a service 254 offering the MASA can encorporate many of the bootstrapping 255 elements (such as the Registrar and the Domain CA) into the cloud 256 service. 258 3. Operational Overview 260 This section describes how an operator interacts with a domain that 261 supports the bootstrapping as described in this document. 263 3.1. Instantiating the Domain Certification Authority 265 This is a one time step by the domain administrator. This is an "off 266 the shelf" CA with the exception that it is designed to work as an 267 integrated part of the security solution. This precludes the use of 268 3rd party certification authority services that do not provide 269 support for delegation of certificate issuance decisions to a domain 270 managed Registration Authority. 272 3.2. Instantiating the Registrar 274 This is a one time step by the domain administrator. One or more 275 devices in the domain are configured take on a Registrar function. 277 A device can be configured to act as a Registrar or a device can 278 auto-select itself to take on this function, using a detection 279 mechanism to resolve potential conflicts and setup communication with 280 the Domain Certification Authority. An automated Registrar selection 281 processes is not detailed here. [[EDNOTE: yet]] 283 3.3. Accepting New Entities 285 For each New Entity the Registrar is informed a priori the unique 286 identifier (e.g. serial number). This can be supplied automatically 287 from the Orchestrator [[EDNOTE: TBD]] or inputed manually by the 288 administrator. 290 For each entity that will be accepted a Registrar maintains the 291 Factory CA identity and the entity's unique identifier. The Factory 292 CA identity could be implemented as the Factory CA root certificate 293 keyIdentifier (the 160-bit SHA-1 hash of the value of the BIT STRING 294 subjectPublicKey). For user interface purposes the keyIdentifier 295 information can be mapped to a colloquial Factory name (Registrars 296 can be shipped with the keyIdentifier of a significant number of 297 third-party manufacturers). 299 Additional policy can be stored for future authorization decisions. 300 For example an expected deployment time window or that a certain 301 Proxy must be used. 303 3.4. Operating the Network 305 Once devices are enrolled to the domain, the network operator can 306 specify a policy, or otherwise configure the devices if required. 307 This is outside scope for this document. 309 4. Functional Overview 311 Entities behave in an autonomic fashion. They discover each other 312 and autonomically establish a key infrastructure deliminating the 313 autonomic domain. See [I-D.behringer-autonomic-network-framework] 314 for more information. 316 The overall flow is shown in Figure 2: 318 +---------+ +----------+ +-----------+ 319 | New | | | | Factory | 320 | Entity | | Domain | | Cloud | 321 | | | | | Service | 322 +---------+ +----------+ +-----------+ 323 | | | 324 |<-------discovery--------->| | 325 |---802.1AR credential----->| | 326 | | | 327 | [ accept device? ] | 328 | | | 329 | |---802.1AR identity-------->| 330 | |---Domain ID--------------->| 331 | | | 332 | | [device belongs] 333 | | [to domain? ] 334 | | | 335 | | [update audit log] 336 | | | 337 | |<---device history log------| 338 | |<-- authorization token-----| 339 | | | 340 | [ still accept device?] | 341 | | | 342 |<----authorization token---| | 343 |<----domain information----| | 344 | | | 345 [auth token valid?] | | 346 | | | 347 |----domain enrolment------>| | 348 |<----domain certificate----| | 349 | | 351 4.1. Behavior of a new entity 353 A New Entity that has not yet been bootstrapped attempts to find a 354 local domain and join it. A number of methods are attempted for 355 establishing communications with the domain in a specified order. 357 Client behavior is as follows: 359 1. Discover a communication channel to the "closest" Registrar by 360 trying the following steps in this order: 361 A. Search for a Proxy on the local link using Neighbor 362 Discovery. If multiple local proxies are discovered attempt 363 communications with each before widening the search to other 364 options. If this fails: 365 B. Obtain an IP address using DHCP, and search for a local 366 registrar using DNS service discovery. If this fails: 367 C. Obtain an IP address using DHCP, and search for a pre-defined 368 Factory provided global registrar using DNS. 369 2. Present IEEE 802.1AR credentials to the discovered Registrar (via 370 a Proxy if necessary). Included is a generated nonce that is 371 specific to this attempt. 372 3. Verify the MASA cloud service generated authorization token as 373 provided by the contacted Registrar. The nonce information 374 previously provided is also checked, if it was not removed by the 375 Registrar. 376 4. If and only if step three is successful: Join Domain, by 377 accepting the domain specific information from the registrar, and 378 by enrolling a domain certificate from the registrar. 379 5. The New Entity is now a member of the domain and will only repeat 380 the discovery aspects of bootstrapping if it is returned to 381 factory default settings. 383 [[EDNOTE: Step (1b and 1c) is similar to the vendor DNS mechanisms 384 described in draft-kwatsen-netconf-zerotouch although the goal here 385 is to contact a Registrar rather than a vendor supplied NMS] 387 The following sections describe each of these steps in more detail. 389 4.1.1. Proxy Discovery 391 Existing protocols provide the appropriate functionality for both 392 discovering the Proxy and facilitating communication through the 393 Proxy: 395 IEEE 802.1X Where the New Entity can be cast as the "supplicant" and 396 the Proxy is the "authenticator". The bootstrapping protocol 397 messages are encapsulated as EAP methods. The "authenticator" 398 reencapsulates the EAPOL frames and forwards them to the 399 "Authentication Server", which provides Registrar functionalities. 400 PANA [RFC5191] [[EDNOTE: TBD]] 401 ND [RFC2461] / [RFC4861] [[EDNOTE: TBD]] NOTE: Neighbor Discovery 402 protocols do not describe a mechanism for forwarding messages. 403 Each provides a method for the New Entity to discover and initiate 404 communication with a local neighbor. In each protocol methods are 405 available to support encapsulation of the bootstrapping protocol 406 messages described elsewhere in this document. Other protocols for 407 transporting bootstrapping messages can be added in future 408 references. 410 All security assocaitions established are between the new device and 411 the Registrar regardless of proxy operations. 413 If multiple proxies are available the New Entity tries each until a 414 successful bootstrapping occurs. The New Entity may prioritize 415 proxies selection order as appropriate for the anticipated 416 environment. 418 If Proxy discovery fails the New Entity moves on to discovering a 419 Registrar directly. 421 4.1.2. Receiving and accepting the Domain Identity 423 The domain trust anchor is received by the New Entity during the 424 boostrapping protocol exchange. 426 EST [RFC7030] details a set of non-autonomic bootstrapping methods 427 such as: 429 o using the Implicit Trust Anchor database (not an autonomic 430 solution because the URL must be securely distributed), 431 o engaging a human user to authorize the CA certificate using out- 432 of-band data (not an autonomic solution because the human user is 433 involved), 434 o and using a configured Explicit TA database (not an autonomic 435 solution because the distribution of symmetric key material is not 436 autonomic). 437 This document describes two additional autonomic methods: 439 MASA authorization token Authorization tokens are obtained by the 440 Registrar from the MASA cloud service and presented to the New 441 Entity for validation. 442 URL redirect If the New Entity discovers a well known global 443 registrar using DNS then the EST protocol exchange is protected 444 using an Implicit TA database, but also the MASA authorization is 445 required. The global registrar MUST claim the device with the 446 MASA server to ensure the logging information is consistent. The 447 global registrar forwards the New Entity to an alternate URI as 448 described in EST [RFC7030]. 449 If these methods fail the New Entity returns to discovery state and 450 attempts bootstrapping with the next available discovered Registrar. 452 [[EDNOTE: move protocol discussion down into protocol section]] The 453 domain trust anchor MUST be included in the TLS handshake Server 454 Certificate "certificate_list" [RFC5246] or the client MUST request 455 the EST Bootstrap Distribution of CA Certificates [RFC7030]. (This 456 document defines an additional method for accepting the CA 457 certificates). 459 4.1.3. Enrollment 461 As the final step of bootstrapping a Registrar helps to issue a 462 domain specific credential to the New Entity. For simplicity in this 463 document, a Registrar primarly facilitates issuing a credential by 464 acting as an RFC5280 Registration Authority for the Domain 465 Certification Authority. 467 Enrollment proceeds as described in Enrollment over Secure Transport 468 (EST) [RFC7030]. The New Entity contacts the Registrar using EST as 469 indicated: 471 o The New Entity is authenticated using the IEEE 802.1AR credentials 472 [[EDNOTE: or in the non-autonomic case using the the out of band 473 secret]. 474 o The EST section 4.1.3 CA Certificates Response is verified using 475 the MASA authorization token provided domain identity. 477 4.1.4. After Enrollment 479 Functionality to provide generic "configuration" is supported. The 480 parsing of this data and any subsequent use of the data, for example 481 communications with a Network Management System is out of scope but 482 is expected to occur after bootstrapping enrollment is complete. 484 See Section 4.5. 486 4.2. Behavior of a proxy 488 The role of the Proxy is to facilitate communications. The Proxy 489 forwards messages between the New Entity and a Registrar. Where 490 existing protocols as detailed in Section 4.1.1 already provide this 491 functionality nothing additional is defined. 493 [[EDNOTE: If neighbor discovery protocols are used for Proxy 494 discovery then a proxy forwarding protocol is to be defined here]] 496 4.3. Behavior of the Registrar 498 One a registrar is established it listens for new entities and 499 determines if they can join the domain. The registrar delivers any 500 necessary authorization information to the new device and facilitates 501 enrollment with the domain PKI. 503 Registrar behavior is as follows: 505 4.3.1. Authenticating the Device 507 The authentication methods detailed in EST [RFC7030] are: 509 o the use of an IEEE 802.1AR IDevID credential, 510 o or the use of a secret that is transmitted out of band between the 511 New Entity and the Registrar (this use case is not autonomic). 513 4.3.2. Accepting the Entity 515 In a fully automated nework all devices must be securely identified. 517 A Registrar accepts or declines a request to join the domain, based 518 on the authenticated identity presented and other policy defined 519 criteria such as Proxy identity. Automated acceptance criteria 520 include: 522 o allow any device of a specific type (as determined by the IEEE 523 802.1AR device identity), 524 o allow any device from a specific Factory (as determined by the 525 IEEE 802.1AR identity), 526 o allow a specific device from a Factory (as determined by the IEEE 527 802.1AR identity) 528 In all cases a Registrar must use the globally available MASA cloud 529 service to verify the device's history log does not include 530 unexpected Registrars. 532 If a device is accepted into the domain, it is then invited to 533 request a domain certificate through a certificate enrolment process. 535 The result is a common trust anchor and device certificates for all 536 autonomic devices in a domain. These certificates can subsequently 537 be used to determine the boundaries of the homenet, to authenticate 538 other domain nodes, and to autonomically enable services on the 539 homenet. 541 4.3.3. Claiming the new entity 543 During initial bootstrapping the New Entity provides a nonce specific 544 to the particular bootstrapping attempt. The registrar should 545 include this nonce when claiming the New Entity from the MASA cloud 546 service. If a nonce is provided by the Registrar then claims from an 547 unauthenticated Registrar are serviced by the MASA cloud resource. 549 The Registrar can claim a New Entity that is not online by forming 550 the request using the entities unique identifier but not including a 551 nonce in the claim request. MASA authorization tokens obtained in 552 this way do not have a lifetime and they provide a permanent method 553 for the domain to claim the device. Evidence of such a claim is 554 provided in the audit log entries available to any future Registrar. 555 Such claims reduce the ability for future domains to secure 556 bootstrapping and therefore the Registrar MUST be authenticated by 557 the MASA cloud service. 559 Claiming an entity establishes an audit log at the MASA server and 560 provides the Registrar with proof, in the form of a MASA 561 authorization token, that the log entry has been inserted. As 562 indicated in Section 4.1.2 a New Entity will only proceed with 563 bootstrapping if a validated MASA authorization token has been 564 recieved. The New Entity therefore enforces that bootstrapping only 565 occurs if the claim has been logged. 567 4.4. Behavior of the MASA Cloud Service 569 The cloud service is provided by the Factory provider. The URI of 570 the cloud service is well known. The URI should be provided as an 571 IEEE 802.1AR IDevID X.509 extension (a "MASA authorization token 572 Distribution Point" extension). 574 The cloud service provides the following functionalities to 575 Registrars: 577 4.4.1. Issue Authorization Token and Log the event 579 A Registrar POSTs a claim message optionally containing the bootstrap 580 nonce to the MASA server. 582 If a nonce is provided the MASA cloud service responds to all 583 requests. The MASA cloud service verifies the Registrar is 584 representative of the domain and generates a privacy protected log 585 entry before responding with the authorization token. 587 If a nonce is not provided the MASA cloud service MUST authenticate 588 the Registrar as a valid customer. This prevents denial of service 589 attacks. The specific level of authentication provided by the 590 customer is not defined here. An MASA Practice Statement (MPS) 591 similar to the Certification Authority CPS, as defined in RFC5280, is 592 provided by the Factory such that Registrar's can determine the level 593 of trust they have in the Factory. 595 4.4.2. Retrieve Audit Entries from Log 597 When determining if a New Entity should be accepted into a domain the 598 Registrar retrieves a copy of the audit log from the MASA cloud 599 service. This contains a list of privacy protected domain identities 600 that have previously claimed the device. Included in the list is an 601 indication of the time the entry was made and if the nonce was 602 included. 604 4.5. Leveraging the new key infrastructure / next steps 606 As the devices have a common trust anchor, device identity can be 607 securely established, making it possible to automatically deploy 608 services across the domain in a secure manner. 610 Examples of services: 611 o Device management. 612 o Routing authentication. 613 o Service discovery. 615 4.5.1. Network boundaries 617 When a device has joined the domain, it can validate the domain 618 membership of other devices. This makes it possible to create trust 619 boundaries where domain members have higher level of trusted than 620 external devices. Using the autonomic User Interface, specific 621 devices can be grouped into to sub domains and specific trust levels 622 can be implemented between those. 624 5. Protocol Details 626 The bootstrapping protocol is an extension of EST [RFC7030]. 628 [[EDNOTE: Insert figure here]] 629 EST provides a bootstrapping mechanism for new entities that are 630 configured with the URI of the EST server or new entities that can 631 "engage a human user to authorize the CA certificate using out-of- 632 band data such as a CA certificate". EST does not provide a 633 completely automated method of bootstrapping the PKI. [[EDNOTE: This 634 paragraph should be expanded to provide a detailed discussion of 635 current EST functionalitites, or do we assume the reader follows the 636 normative reference?]]. 638 The following additions provide for fully automated functionality. 639 EST is extended by defining additional HTTP URIs and messages 640 specific to bootstrapping. These are optionally supported by the EST 641 server within the same .well-known URI tree as the existing EST URIs. 643 The "New Entity" is the EST client and the "Registrar" is the EST 644 server. 646 5.1. EAP-EST 648 In order to support Proxy environments EAP-EST is defined. 650 [[EDNOTE: TBD. EST is TLS with some data. EAP-TLS and other similar 651 protocols provide an example framework for filling out this section]] 653 5.2. Request bootstrap token 655 When the New Entity reaches the EST section 4.1.1 "Bootstrap 656 Distribution of CA Certificates" state but wishes to proceed in a 657 fully automated fashion it makes a request for a MASA authorization 658 token from the Registrar. 660 This is done with an HTTPS POST using the operation path value of 661 "/requestbootstraptoken". 663 The request format is a raw nonce value. [[EDNOTE: exact format TBD. 664 There is an advantage to having the client sign the nonce (similar to 665 a PKI Certification Signing Request) since this allows the MASA cloud 666 service to confirm the actual device identity. It is not clear that 667 there is a security benefit from this.]] 669 The Registrar validates the client identity as described in EST 670 [RFC7030] section 3.3.2. The registrar performs authorization as 671 detailed in Section 4.3.2. If authorization is successful the 672 Registrar obtains a MASA authorization token from the MASA cloud 673 service (see Section 5.3). 675 The recieved MASA authorization token is returned to the New Entity. 677 [[EDNOTE: update to CMS language]] 679 5.3. Request MASA authorization token 681 A registrar requests the MASA authorization token from the cloud 682 service using this EST extension. 684 This is done with an HTTP POST using the operation path value of 685 "/requestMASAauthorization". 687 The request format is an optional raw nonce value (as obtained from 688 the bootstrap request) and the IEEE 802.1AR identity of the device as 689 a serial number (the full certificate is not needed and no proof-of- 690 possession information for the device identity is included). This 691 information is encapsulated in a PKCS7 signed data structure that is 692 signed by the Registrar. The entire certificate chain, up to and 693 including the Domain CA, is included in the PKCS7. 695 The MASA cloud service checks the internal consistency of the PKCS7 696 but is unable to actually authenticate the domain identity 697 information. The domain is not know to the MASA server in advance 698 and a shared trust anchor is not implied. The MASA server verifies 699 that the PKCS7 is signed by a Registrar (by checking for the cmc-idRA 700 field in the Registrar certificate) certificate that was issued by 701 the root certificate included in the PKCS7. 703 The domain ID is extracted from the root certificate and is used to 704 generate the MASA authorization token and to update the audit log. 706 [[EDNOTE: update to CMS language]] 708 5.4. Request MASA authorization log 710 A registrar requests the MASA authorization log from the cloud 711 service using this EST extension. 713 This is done with an HTTP GET using the operation path value of 714 "/requestMASAlog". 716 The log data returned is a file consisting of each log entry. The 717 data in each entry includes: 719 o date/time of the entry 720 o domain ID (this is just a hash of the public key information and 721 is thus privacy protected) 722 o nonce value 723 [[EDNOTE: exact format TBD]] 725 6. Reduced security operational modes 727 A common requirement of bootstrapping infrastructures is often that 728 they support less secure operational modes. To support these 729 operational modes the Registrar can choose to accept devices using 730 less secure methods. For example: 732 1. The registrar may chose to accept all devices, or all devices of 733 a particular type, at the administrator's discretion. This may 734 occur when: Informing the Registrar of unique identifiers of new 735 entities might be operationally difficult. 736 2. The registrar may chose to accept devices that claim a unique 737 identity without the benefit of authenticating that claimed 738 identity. This may occur when: The New Entity does not include 739 an IEEE 802.1AR factory installed credential. 740 3. A representative of the Registar (e.g. the Orchestrator) may 741 request nonce-less authorization tokens from the MASA cloud 742 service when network connectivity is available. These tokens can 743 then be transmitted to the Registrar and stored until they are 744 needed during bootstrapping operations. Ths may occur when: The 745 target network is protected by an air gap and therefore can not 746 contact the MASA cloud service during New Entity deployment. 747 4. The device may have an operational mode where it skips 748 authorization token validation. For example if a physical button 749 is depressed during the bootstrapping operation. This may occur 750 when: A device Factory goes out of business or otherwise fails to 751 provide a reliable MASA cloud service. 752 5. The device may not require the MASA cloud service authorization 753 token. An entity that does not validate the domain identity is 754 inherently dangerous as it may contain malware. This risk should 755 be mitigated using attestation and measurement technologies. In 756 order to support an unsecured imprint the New Entity MUST support 757 remote attestation technologies such as is defined by the Trusted 758 Computing Group. [[EDNOTE: How to include remote attestation 759 into the boostrapping protocol exchange is TBD]]. This may occur 760 when: The device Factory does not provide a MASA cloud service. 762 7. Security Considerations 764 In order to support a variety of use cases, devices can be claimed by 765 a registrar without proving possession of the device in question. 766 This would result in a nonceless, and thus always valid, claim. The 767 MASA cloud service is required to authenticate such Registrars but no 768 programatic method is provided to ensure good behavior by the MASA 769 cloud service. Nonceless entries into the audit log therefore 770 permanently reduce the value of a device because future Registrars, 771 during future bootstrap attempts, must now be configured with policy 772 to ignore previously (and potentially unknown) domains. 774 Future registrars are recommended to take the audit history of a 775 device into account when deciding to join such devices into their 776 network. 778 It is possible for an attacker to send an authorization request to 779 the MASA cloud service directly after the real Registrar obtains an 780 authorization log. If the attacker could also force the 781 bootstrapping protocol to reset there is a theoretical opportunity 782 for the attacker to use the authorization token to take control of 783 the New Entity but then proceed to enrol with the target domain. To 784 prevent this the MASA cloud service is rate limited to only generate 785 authorization tokens at a rate of 1 per minute. The Registrar 786 therefore has at least 1 minute to get the response back to the New 787 Entity. [[EDNOTE: a better solution can likely be found. This text 788 captures the issue for now.]] Also the Registar can double check the 789 log information after enrolling the New Entity. 791 The MASA cloud service could lock a claim and refuse to issue a new 792 token. Or the MASA cloud service could go offline (for example if a 793 vendor went out of business). This functionality provides benefits 794 such as theft resistance, but it also implies an operational risk. 795 This can be mitigated by Registrars that request nonce-less 796 authorization tokens. 798 8. References 800 8.1. Normative References 802 [IDevID] IEEE Standard, "IEEE 802.1AR Secure Device Identifier", 803 December 2009, . 806 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 807 Requirement Levels", BCP 14, RFC 2119, March 1997. 809 [RFC7030] Pritikin, M., Yee, P., and D. Harkins, "Enrollment over 810 Secure Transport", RFC 7030, October 2013. 812 8.2. Informative References 814 [I-D.behringer-autonomic-network-framework] 815 Behringer, M., Pritikin, M., Bjarnason, S., and A. Clemm, 816 "A Framework for Autonomic Networking", 817 draft-behringer-autonomic-network-framework-01 (work in 818 progress), October 2013. 820 Authors' Addresses 822 Max Pritikin 823 Cisco 825 Email: pritikin@cisco.com 827 Michael H. Behringer 828 Cisco 830 Email: mbehring@cisco.com 832 Steinthor Bjarnason 833 Cisco 835 Email: sbjarnas@cisco.com