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'IEEE8021AB' ** Obsolete normative reference: RFC 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) == Outdated reference: A later version (-20) exists of draft-ietf-netmod-rfc6087bis-14 -- Obsolete informational reference (is this intentional?): RFC 7042 (Obsoleted by RFC 9542) Summary: 2 errors (**), 0 flaws (~~), 7 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group E. Lear 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track R. Droms 5 Expires: March 24, 2018 6 D. Romascanu 7 September 20, 2017 9 Manufacturer Usage Description Specification 10 draft-ietf-opsawg-mud-11 12 Abstract 14 This memo specifies a component-based architecture for manufacturer 15 usage descriptions (MUD). The goal of MUD is to provide a means for 16 Things to signal to the network what sort of access and network 17 functionality they require to properly function. The initial focus 18 is on access control. Later work can delve into other aspects. 20 This memo specifies two YANG modules, IPv4 and IPv6 DHCP options, an 21 LLDP TLV, a URL suffix specification, an X.509 certificate extension 22 and a means to sign and verify the descriptions. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on March 24, 2018. 41 Copyright Notice 43 Copyright (c) 2017 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 1.1. What MUD doesn't do . . . . . . . . . . . . . . . . . . . 4 60 1.2. A Simple Example . . . . . . . . . . . . . . . . . . . . 5 61 1.3. Determining Intended Use . . . . . . . . . . . . . . . . 5 62 1.4. Finding A Policy: The MUD URL . . . . . . . . . . . . . . 5 63 1.5. Types of Policies . . . . . . . . . . . . . . . . . . . . 6 64 1.6. Terminology . . . . . . . . . . . . . . . . . . . . . . . 8 65 1.7. The Manufacturer Usage Description Architecture . . . . . 8 66 1.8. Order of operations . . . . . . . . . . . . . . . . . . . 10 67 2. The MUD Model and Semantic Meaning . . . . . . . . . . . . . 10 68 2.1. The IETF-MUD YANG Module . . . . . . . . . . . . . . . . 11 69 3. Data Node Definitions . . . . . . . . . . . . . . . . . . . . 12 70 3.1. to-device-policy and from-device-policy containers . . . 13 71 3.2. last-update . . . . . . . . . . . . . . . . . . . . . . . 13 72 3.3. cache-validity . . . . . . . . . . . . . . . . . . . . . 13 73 3.4. masa-server . . . . . . . . . . . . . . . . . . . . . . . 13 74 3.5. is-supported . . . . . . . . . . . . . . . . . . . . . . 13 75 3.6. systeminfo . . . . . . . . . . . . . . . . . . . . . . . 14 76 3.7. extensions . . . . . . . . . . . . . . . . . . . . . . . 14 77 3.8. manufacturer . . . . . . . . . . . . . . . . . . . . . . 14 78 3.9. same-manufacturer . . . . . . . . . . . . . . . . . . . . 14 79 3.10. model . . . . . . . . . . . . . . . . . . . . . . . . . . 14 80 3.11. local-networks . . . . . . . . . . . . . . . . . . . . . 15 81 3.12. controller . . . . . . . . . . . . . . . . . . . . . . . 15 82 3.13. my-controller . . . . . . . . . . . . . . . . . . . . . . 15 83 3.14. direction-initiated . . . . . . . . . . . . . . . . . . . 15 84 4. Processing of the MUD file . . . . . . . . . . . . . . . . . 16 85 5. What does a MUD URL look like? . . . . . . . . . . . . . . . 16 86 6. The MUD YANG Model . . . . . . . . . . . . . . . . . . . . . 17 87 7. The Domain Name Extension to the ACL Model . . . . . . . . . 22 88 7.1. source-dnsname . . . . . . . . . . . . . . . . . . . . . 23 89 7.2. destination-dnsname . . . . . . . . . . . . . . . . . . . 23 90 7.3. The ietf-acldns Model . . . . . . . . . . . . . . . . . . 23 91 8. MUD File Example . . . . . . . . . . . . . . . . . . . . . . 25 92 9. The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . . 27 93 9.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 28 94 9.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 28 95 9.3. Relay Requirements . . . . . . . . . . . . . . . . . . . 29 96 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 29 97 11. The Manufacturer Usage Description LLDP extension . . . . . . 30 98 12. Creating and Processing of Signed MUD Files . . . . . . . . . 32 99 12.1. Creating a MUD file signature . . . . . . . . . . . . . 32 100 12.2. Verifying a MUD file signature . . . . . . . . . . . . . 32 101 13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 33 102 14. Deployment Considerations . . . . . . . . . . . . . . . . . . 33 103 15. Security Considerations . . . . . . . . . . . . . . . . . . . 34 104 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 105 16.1. YANG Module Registrations . . . . . . . . . . . . . . . 36 106 16.2. DHCPv4 and DHCPv6 Options . . . . . . . . . . . . . . . 36 107 16.3. PKIX Extensions . . . . . . . . . . . . . . . . . . . . 37 108 16.4. Well Known URI Suffix . . . . . . . . . . . . . . . . . 37 109 16.5. MIME Media-type Registration for MUD files . . . . . . . 37 110 16.6. LLDP IANA TLV Subtype Registry . . . . . . . . . . . . . 38 111 16.7. The MUD Well Known Universal Resource Name (URNs) . . . 39 112 16.8. Extensions Registry . . . . . . . . . . . . . . . . . . 39 113 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 39 114 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 40 115 18.1. Normative References . . . . . . . . . . . . . . . . . . 40 116 18.2. Informative References . . . . . . . . . . . . . . . . . 42 117 Appendix A. Changes from Earlier Versions . . . . . . . . . . . 43 118 Appendix B. Default MUD nodes . . . . . . . . . . . . . . . . . 46 119 Appendix C. A Sample Extension: DETNET-indicator . . . . . . . . 50 120 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54 122 1. Introduction 124 The Internet has largely been constructed on general purpose 125 computers; those devices that may be used for a purpose that is 126 specified by those who buy the device. [RFC1984] presumed that an 127 end device would be most capable of protecting itself. This made 128 sense when the typical device was a workstation or a mainframe, and 129 it continues to make sense for general purpose computing devices 130 today, including laptops, smart phones, and tablets. 132 [RFC7452] discusses design patterns for, and poses questions about, 133 smart objects. Let us then posit a group of objects that are 134 specifically NOT general purpose computers. These devices have a 135 purpose to their use. By definition, therefore, all other purposes 136 are NOT intended. The combination of these two statements can be 137 restated as a manufacturer usage description (MUD) that can be 138 applied at various points within a network. Although this memo may 139 seem to stress access requirements, usage intent also consists of 140 quality of service needs a device may have. 142 We use the notion of "manufacturer" loosely in this context, to 143 simply mean the entity or organization that will state how a device 144 is intended to be used. In the context of a lightbulb, this might 145 indeed be the lightbulb manufacturer. In the context of a smarter 146 device that has a built in Linux stack, it might be an integrator of 147 that device. The key points are that the device itself is expected 148 to serve a limited purpose, and that there may exist an organization 149 in the supply chain of that device that will take responsibility for 150 informing the network about that purpose. 152 The intent MUD is to solve for the following problems: 154 o Substantially reduce the threat surface on a device entering a 155 network to those communications intended by the manufacturer. 157 o Provide for a means to scale network policies to the ever- 158 increasing number types of devices in the network. 160 o Provide a means to address at least some vulnerabilities in a way 161 that is faster than it might take to update systems. This will be 162 particularly true for systems that are no longer supported by 163 their manufacturer. 165 o Keep the cost of implementation of such a system to the bare 166 minimum. 168 MUD consists of three architectural building blocks: 170 o A classifier that a device emits that can be used to locate a 171 description; 173 o The description itself, including how it is interpreted, and; 175 o A means for local network management systems to retrieve the 176 description. 178 In this specification we describe each of these building blocks and 179 how they are intended to be used together. However, they may also be 180 used separately, independent of this specification by local 181 deployments for their own purposes. 183 1.1. What MUD doesn't do 185 MUD is not intended to address network authorization of general 186 purpose computers, as their manufacturers cannot envision a specific 187 communication pattern to describe. In addition, even those devices 188 that have a single or small number of uses might have very broad 189 communication patterns. MUD on its own is not for them either. 191 No matter how good a MUD-enabled network is, it will never replace 192 the need for manufacturers to patch vulnerabilities. It may, 193 however, provide network administrators with some additional 194 protection when those vulnerabilities exist. 196 Finally, no matter what the manufacturer specifies in a MUD file, 197 these are not directives, but suggestions. How they are instantiated 198 locally will depend on many factors, and is ultimately up to the 199 local network administrator. 201 1.2. A Simple Example 203 A light bulb is intended to light a room. It may be remotely 204 controlled through the network; and it may make use of a rendezvous 205 service of some form that an app on smart phone accesses. What we 206 can say about that light bulb, then, is that all other network access 207 is unwanted. It will not contact a news service, nor speak to the 208 refrigerator, and it has no need of a printer or other devices. It 209 has no social networking friends. Therefore, an access list applied 210 to it that states that it will only connect to the single rendezvous 211 service will not impede the light bulb in performing its function, 212 while at the same time allowing the network to provide both it and 213 other devices an additional layer of protection. 215 1.3. Determining Intended Use 217 The notion of intended use is in itself not new. Network 218 administrators apply access lists every day to allow for only such 219 use. This notion of white listing was well described by Chapman and 220 Zwicky in [FW95]. Profiling systems that make use of heuristics to 221 identify types of systems have existed for years as well. 223 A Thing could just as easily tell the network what sort of protection 224 it requires without going into what sort of system it is. This 225 would, in effect, be the converse of [RFC7488]. In seeking a general 226 purpose solution, however, we assume that a device has so few 227 capabilities that it will implement the least necessary capabilities 228 to function properly. This is a basic economic constraint. Unless 229 the network would refuse access to such a device, its developers 230 would have no reason to provide the network any information. To 231 date, such an assertion has held true. 233 1.4. Finding A Policy: The MUD URL 235 Our work begins with the device emitting a Universal Resource Locator 236 (URL) [RFC3986]. This URL serves both to classify the device type 237 and to provide a means to locate a policy file. 239 In this memo three means are defined to emit the MUD URL. One is a 240 DHCP option[RFC2131],[RFC3315] that the DHCP client uses to inform 241 the DHCP server. The DHCP server may take further actions, such as 242 retrieve the URL or otherwise pass it along to network management 243 system or controller. The second method defined is an X.509 244 constraint. The IEEE has developed [IEEE8021AR] that provides a 245 certificate-based approach to communicate device characteristics, 246 which itself relies on [RFC5280]. The MUD URL extension is non- 247 critical, as required by IEEE 802.1AR. Various means may be used to 248 communicate that certificate, including Tunnel Extensible 249 Authentication Protocol (TEAP) [RFC7170]. Finally, a Link Layer 250 Discovery Protocol (LLDP) frame is defined [IEEE8021AB]. 252 It is possible that there may be other means for a MUD URL to be 253 learned by a network. For instance, some devices may already be 254 fielded or have very limited ability to communicate a MUD URL, and 255 yet can be identified through some means, such as a serial number or 256 a public key. In these cases, manufacturers may be able to map those 257 identifies to particular MUD URLs (or even the files themselves). 258 Similarly, there may be alternative resolution mechanisms available 259 for situations where Internet connectivity is limited or does not 260 exist. Such mechanisms are not described in this memo, but are 261 possible. Implementors should allow for this sort of flexibility of 262 how MUD URLs may be learned. 264 1.5. Types of Policies 266 When the MUD URL is resolved, the MUD controller retrieves a file 267 that describes what sort of communications a device is designed to 268 have. The manufacturer may specify either specific hosts for cloud 269 based services or certain classes for access within an operational 270 network. An example of a class might be "devices of a specified 271 manufacturer type", where the manufacturer type itself is indicated 272 simply by the authority component (e.g, the domain name) of the MUD 273 URL. Another example might be to allow or disallow local access. 274 Just like other policies, these may be combined. For example: 276 Allow access to devices of the same manufacturer 277 Allow access to and from controllers via COAP 278 Allow access to local DNS/DHCP 279 Deny all other access 281 To add a bit more depth that should not be a stretch of anyone's 282 imagination, one could also make use of port-based access lists. 283 Thus a printer might have a description that states: 285 Allow access for port IPP or port LPD 286 Allow local access for port HTTP 287 Deny all other access 289 In this way anyone can print to the printer, but local access would 290 be required for the management interface. 292 The files that are retrieved are intended to be closely aligned to 293 existing network architectures so that they are easy to deploy. We 294 make use of YANG [RFC6020] because of the time and effort spent to 295 develop accurate and adequate models for use by network devices. 296 JSON is used as a serialization for compactness and readability, 297 relative to XML. Other formats may be chosen with later versions of 298 MUD. 300 While the policy examples given here focus on access control, this is 301 not intended to be the sole focus. By structuring the model 302 described in this document with clear extension points, so that other 303 descriptions could be included. One that often comes to mind is 304 quality of service. 306 The YANG modules specified here are extensions of 307 [I-D.ietf-netmod-acl-model]. The extensions to this model allow for 308 a manufacturer to express classes of systems that a manufacturer 309 would find necessary for the proper function of the device. Two 310 modules are specified. The first module specifies a means for domain 311 names to be used in ACLs so that devices that have their controllers 312 in the cloud may be appropriately authorized with domain names, where 313 the mapping of those names to addresses may rapidly change. 315 The other module abstracts away IP addresses into certain classes 316 that are instantiated into actual IP addresses through local 317 processing. Through these classes, manufacturers can specify how the 318 device is designed to communicate, so that network elements can be 319 configured by local systems that have local topological knowledge. 320 That is, the deployment populates the classes that the manufacturer 321 specifies. The abstractions below map to zero or more hosts, as 322 follows: 324 Manufacturer: A device made by a particular manufacturer, as 325 identified by the authority component of its MUD-URL 327 same-manufacturer: Devices that have the same authority component of 328 their MUD-URL. 330 Controller: Devices that the local network administrator admits to 331 the particular class. 333 my-controller: Devices associated with the MUD-URL of a device that 334 the administrator admits. 336 local: The class of IP addresses that are scoped within some 337 administrative boundary. By default it is suggested that this be 338 the local subnet. 340 The "manufacturer" classes can be easily specified by the 341 manufacturer, whereas controller classes are initially envisioned to 342 be specified by the administrator. 344 Because manufacturers do not know who will be using their devices, it 345 is important for functionality referenced in usage descriptions to be 346 relatively ubiquitous, and mature. For these reasons only a limited 347 subset YANG-based configuration of is permitted in a MUD file. 349 1.6. Terminology 351 MUD: manufacturer usage description. 353 MUD file: a file containing YANG-based JSON that describes a Thing 354 and associated suggested specific network behavior. 356 MUD file server: a web server that hosts a MUD file. 358 MUD controller: the system that requests and receives the MUD file 359 from the MUD server. After it has processed a MUD file it may 360 direct changes to relevant network elements. 362 MUD URL: a URL that can be used by the MUD controller to receive the 363 MUD file. 365 Thing: the device emitting a MUD URL. 367 Manufacturer: the entity that configures the Thing to emit the MUD 368 URL and the one who asserts a recommendation in a MUD file. The 369 manufacturer might not always be the entity that constructs a 370 Thing. It could, for instance, be a systems integrator, or even a 371 component provider. 373 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 374 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 375 document are to be interpreted as described in [RFC2119]. 377 1.7. The Manufacturer Usage Description Architecture 379 With these components laid out we now have the basis for an 380 archicture. This leads us to ASCII art. 382 ....................................... 383 . ____________ . _____________ 384 . | | . | | 385 . | MUD |-->get URL-->| MUD | 386 . | Controller | .(https) | File Server | 387 . End system network |____________|<-MUD file<-<|_____________| 388 . . . 389 . . . 390 . _______ _________ . 391 .| | (dhcp et al) | router | . 392 .| Thing |---->MUD URL-->| or | . 393 .|_______| | switch | . 394 . |_________| . 395 ....................................... 397 Figure 1: MUD Architecture 399 In the above diagram, the switch or router collects MUD URLs and 400 forwards them to the network management system for processing. This 401 happens in different ways, depending on how the URL is communicated. 402 For instance, in the case of DHCP, the DHCP server might receive the 403 URL and then process it. In the case of IEEE 802.1X, the switch 404 would carry the URL via a certificate to the authentication server 405 via EAP over Radius[RFC3748], which would then process it. One 406 method to do this is TEAP, described in [RFC7170]. The certificate 407 extension is described below. 409 The information returned by the web site is valid for the duration of 410 the Thing's connection, or as specified in the description. Thus if 411 the Thing is disconnected, any associated configuration in the switch 412 can be removed. Similarly, from time to time the description may be 413 refreshed, based on new capabilities or communication patterns or 414 vulnerabilities. 416 The web site is typically run by or on behalf of the manufacturer. 417 Its domain name is that of the authority found in the MUD URL. For 418 legacy cases where Things cannot emit a URL, if the switch is able to 419 determine the appropriate URL, it may proxy it, the trivial cases 420 being a map between some registered Thing or port and a URL. 422 The role of the MUD controller in this environment is to do the 423 following: 425 o receive MUD URLs, 427 o retrieve MUD files, 428 o translate abstractions in the MUD files to specific Thing 429 configuration, 431 o maintain and update any required mappings of the abstractions, and 433 o update network elements with appropriate configuration. 435 A MUD controller may be a component of a AAA or network management 436 system. Communication within those systems and from those systems to 437 network elements is beyond the scope of this memo. 439 1.8. Order of operations 441 As mentioned above, MUD contains architectural building blocks, and 442 so order of operation may vary. However, here is one clear intended 443 example: 445 1. Thing emits URL. 447 2. That URL is forwarded to a MUD controller by the nearest switch 448 (how this happens depends on the way in which the MUD URL is 449 emitted). 451 3. The MUD controller retrieves the MUD file and signature from the 452 MUD file server, assuming it doesn't already have copies. After 453 validating the signature, it may test the URL against a web or 454 domain reputation service, and it may test any hosts within the 455 file against those reputation services, as it deems fit. 457 4. The MUD controller may query the administrator for permission to 458 add the Thing and associated policy. If the Thing is known or 459 the Thing type is known, it may skip this step. 461 5. The MUD controller instantiates local configuration based on the 462 abstractions defined in this document. 464 6. The MUD controller configures the switch nearest the Thing. 465 Other systems may be configured as well. 467 7. When the Thing disconnects, policy is removed. 469 2. The MUD Model and Semantic Meaning 471 A MUD file consists of JSON based on a YANG model. For purposes of 472 MUD, the nodes that can be modified are access lists as augmented by 473 this model. The MUD file is limited to the serialization of only the 474 following YANG schema: 476 o ietf-access-control-list [I-D.ietf-netmod-acl-model] 478 o ietf-mud (this document) 480 o ietf-acldns (this document) 482 Extensions may be used to add additional schema. This is described 483 further on. 485 To provide the widest possible deployability, publishers of MUD files 486 SHOULD make use of the abstractions in this memo and avoid the use of 487 IP addresses. The addressing of one side of an access list is 488 implicit, based on whether it is applied as to-device-policy or from- 489 device-policy. 491 With the exceptions of "acl-name", "acl-type", "rule-name", and TCP 492 and UDP source and destination port information, publishers of MUD 493 files SHOULD limit the use of ACL model leaf nodes expressed to those 494 found in this specification. Absent any extensions, MUD files are 495 assumed to implement only the following ACL model features: 497 o any-acl, mud-acl, icmp-acl, ipv6-acl, tcp-acl, any-acl, udp-acl, 498 ipv4-acl, and ipv6-acl 500 MUD controllers MAY ignore any particular component of a description 501 or MAY ignore the description in its entirety, and SHOULD carefully 502 inspect all MUD descriptions. Publishers of MUD files MUST NOT 503 include other nodes except as described in Section 3.7. See that 504 section for more information. 506 2.1. The IETF-MUD YANG Module 508 This module is structured into three parts: 510 o The first container "mud" holds information that is relevant to 511 retrieval and validity of the MUD file itself, as well as policy 512 intended to and from the Thing. 514 o The second component augments the matching container of the ACL 515 model to add several nodes that are relevant to the MUD URL, or 516 otherwise abstracted for use within a local environment. 518 o The third component augments the tcp-acl container of the ACL 519 model to add the ability to match on the direction of initiation 520 of a TCP connection. 522 A valid MUD file will contain two root objects, a "mud" container and 523 an "access-lists" container. Extensions may add additional root 524 objects as required. 526 A simplified graphical representation of the data models is used in 527 this document. The meaning of the symbols in these diagrams is 528 explained in [I-D.ietf-netmod-rfc6087bis]. 530 module: ietf-mud 531 +--rw mud! 532 +--rw mud-url inet:uri 533 +--rw last-update yang:date-and-time 534 +--rw cache-validity? uint8 535 +--rw masa-server? inet:uri 536 +--rw is-supported boolean 537 +--rw systeminfo? inet:uri 538 +--rw extensions* string 539 +--rw from-device-policy 540 | +--rw access-lists 541 | +--rw access-list* [acl-name acl-type] 542 | +--rw acl-name -> /acl:access-lists/acl/acl-name 543 | +--rw acl-type identityref 544 +--rw to-device-policy 545 +--rw access-lists 546 +--rw access-list* [acl-name acl-type] 547 +--rw acl-name -> /acl:access-lists/acl/acl-name 548 +--rw acl-type identityref 549 augment /acl:access-lists/acl:acl/acl:aces/ 550 acl:ace/acl:matches: 551 +--rw mud-acl 552 +--rw manufacturer? inet:host 553 +--rw same-manufacturer? empty 554 +--rw model? inet:uri 555 +--rw local-networks? empty 556 +--rw controller? inet:uri 557 +--rw my-controller? empty 558 augment /acl:access-lists/acl:acl/acl:aces/ 559 acl:ace/acl:matches/acl:tcp-acl: 560 +--rw direction-initiated? direction 562 3. Data Node Definitions 564 Note that in this section, when we use the term "match" we are 565 referring to the ACL model "matches" node, and thus returns positive 566 such that an action should be applied. 568 The following nodes are defined. 570 3.1. to-device-policy and from-device-policy containers 572 [I-D.ietf-netmod-acl-model] describes access-lists but does not 573 attempt to indicate where they are applied as that is handled 574 elsewhere in a configuration. However, in this case, a MUD file must 575 be explicit in describing the communication pattern of a Thing, and 576 that includes indicating what is to be permitted or denied in either 577 direction of communication. Hence each of these containers indicate 578 the appropriate direction of a flow in association with a particular 579 Thing. They contain references to specific access-lists. 581 3.2. last-update 583 This is a date-and-time value of when the MUD file was generated. 584 This is akin to a version number. Its form is taken from [RFC6991] 585 which, for those keeping score, in turn was taken from Section 5.6 of 586 [RFC3339], which was taken from [ISO.8601.1988]. 588 3.3. cache-validity 590 This uint8 is the period of time in hours that a network management 591 station MUST wait since its last retrieval before checking for an 592 update. It is RECOMMENDED that this value be no less than 24 and 593 MUST NOT be more than 168 for any Thing that is supported. This 594 period SHOULD be no shorter than any period determined through HTTP 595 caching directives (e.g., "cache-control" or "Expires"). N.B., 596 expiring of this timer does not require the MUD controller to discard 597 the MUD file, nor terminate access to a Thing. See Section 15 for 598 more information. 600 3.4. masa-server 602 This optional node refers to the URL that should be used to resolve 603 the MASA service, as specified in 604 [I-D.ietf-anima-bootstrapping-keyinfra]. 606 3.5. is-supported 608 This boolean is an indication from the manufacturer to the network 609 administrator as to whether or not the Thing is supported. In this 610 context a Thing is said to be supported if the manufacturer might 611 issue an update to the Thing or if the manufacturer might update the 612 MUD file. 614 3.6. systeminfo 616 This is a URL that points to a description of the Thing to be 617 connected. The intent is for administrators to be able to read about 618 what the Thing is the first time the MUD-URL is used. 620 3.7. extensions 622 This optional leaf-list names MUD extensions that are used in the MUD 623 file. Note that NO MUD extensions may be used in a MUD file prior to 624 the extensions being declared. Implementations MUST ignore any node 625 in this file that they do not understand. 627 Note that extensions can either extend the MUD file as described in 628 the previous paragraph, or they might reference other work. A good 629 example of how this might be done is the masa-server URI that is 630 defined in the base model. We say nothing about the semantics of 631 that work here, but rather leave that to the underlying specification 632 found in [I-D.ietf-anima-bootstrapping-keyinfra]. 634 3.8. manufacturer 636 This node consists of a hostname that would be matched against the 637 authority component of another Thing's MUD URL. In its simplest form 638 "manufacturer" and "same-manufacturer" may be implemented as access- 639 lists. In more complex forms, additional network capabilities may be 640 used. For example, if one saw the line "manufacturer" : 641 "flobbidy.example.com", then all Things that registered with a MUD 642 URL that contained flobbity.example.com in its authority section 643 would match. 645 3.9. same-manufacturer 647 This is an equivalent for when the manufacturer element is used to 648 indicate the authority that is found in another Thing's MUD URL 649 matches that of the authority found in this Thing's MUD URL. For 650 example, if the Thing's MUD URL were https://b1.example.com/.well- 651 known/mud/v1/ThingV1, then all devices that had MUD URL with an 652 authority section of b1.example.com would match. 654 3.10. model 656 This string matches the entire MUD URL, thus covering the model that 657 is unique within the context of the authority. It may contain not 658 only model information, but versioning information as well, and any 659 other information that the manufacturer wishes to add. The intended 660 use is for devices of this precise class to match, to permit or deny 661 communication between one another. 663 3.11. local-networks 665 This null-valued node expands to include local networks. Its default 666 expansion is that packets must not traverse toward a default route 667 that is received from the router. However, administrators may expand 668 the expression as is appropriate in their deployments. 670 3.12. controller 672 This URI specifies a value that a controller will register with the 673 mud controller. The node then is expanded to the set of hosts that 674 are so registered. This node may also be a URN. In this case, the 675 URN describes a well known service, such as DNS or NTP. 677 Great care should be used when invoking the controller class. For 678 one thing, it requires some understanding by the administrator as to 679 when it is appropriate. Classes that are standardized may make it 680 possible to easily name devices that support standard functions. For 681 instance, the MUD controller could have some knowledge of which DNS 682 servers should be used for any particular group of Things. Non- 683 standard classes will likely require some sort of administrator 684 interaction. Pre-registration in such classes by controllers with 685 the MUD server is encouraged. The mechanism to do that is beyond the 686 scope of this work. 688 Controller URIs MAY take the form of a URL (e.g. "http[s]://"). 689 However, MUD controllers MUST NOT resolve and retrieve such files, 690 and it is RECOMMENDED that there be no such file at this time, as 691 their form and function may be defined at a point in the future. For 692 now, URLs should serve simply as class names and be populated by the 693 local deployment administrator. 695 3.13. my-controller 697 This null-valued node signals to the MUD controller to use whatever 698 mapping it has for this MUD-URL to a particular group of hosts. This 699 may require prompting the administrator for class members. Future 700 work should seek to automate membership management. 702 3.14. direction-initiated 704 When applied this matches packets when the flow was initiated in the 705 corresponding direction. [RFC6092] specifies IPv6 guidance best 706 practices. While that document is scoped specifically to IPv6, its 707 contents are applicable for IPv4 as well. When this flag is set, and 708 the system has no reason to believe a flow has been initiated it MUST 709 drop the packet. This node may be implemented in its simplest form 710 by looking at naked SYN bits, but may also be implemented through 711 more stateful mechanisms. 713 4. Processing of the MUD file 715 To keep things relatively simple in addition to whatever definitions 716 exist, we also apply two additional default behaviors: 718 o Anything not explicitly permitted is denied. 720 o Local DNS and NTP are, by default, permitted to and from the 721 Thing. 723 An explicit description of the defaults can be found in Appendix B. 725 5. What does a MUD URL look like? 727 To begin with, MUD takes full advantage of both the https: scheme and 728 the use of .well-known. HTTPS is important in this case because a 729 man in the middle attack could otherwise harm the operation of a 730 class of Things. .well-known is used because we wish to add 731 additional structure to the URL, and want to leave open for future 732 versions both the means by which the URL is processed and the format 733 of the MUD file retrieved (there have already been some discussions 734 along these lines). The URL appears as follows: 736 mud-url = "https://" authority "/.well-known/mud/" mud-rev 737 "/" modelinfo ( "?" extras ) 738 ; authority is from RFC3986 739 mud-rev = "v1" 740 modelinfo = segment ; from RFC3986 741 extras = query ; from RFC3986 743 mud-rev signifies the version of the manufacturer usage description 744 file. This memo specifies "v1" of that file. Later versions may 745 permit additional schemas or modify the format. In order to provide 746 for the broadest compatibility for the various transmission 747 mechanisms, the length of the URL for v1 MUST NOT exceed 255 octets. 749 Taken together with the mud-url, "modelinfo" represents a Thing model 750 as the manufacturer wishes to represent it. It could be a brand name 751 or something more specific. It also may provide a means to indicate 752 what version the product is. Specifically if it has been updated in 753 the field, this is the place where evidence of that update would 754 appear. The field should be changed when the intended communication 755 patterns of a Thing change. While from a controller standpoint, only 756 comparison and matching operations are safe, it is envisioned that 757 updates will require some administrative review. Processing of this 758 URL occurs as specified in [RFC2818] and [RFC3986]. 760 "extras" is intended for use by the MUD controller to provide 761 additional information such as posture about the Thing to the MUD 762 file server. This field MUST NOT be configured on the Thing itself 763 by a manufacturer - that is what "modelinfo" is for. It is left as 764 future work to define the full semantics of this field. 766 6. The MUD YANG Model 768 file "ietf-mud@2017-09-15.yang" 769 module ietf-mud { 770 yang-version 1.1; 771 namespace "urn:ietf:params:xml:ns:yang:ietf-mud"; 772 prefix ietf-mud; 774 import ietf-access-control-list { 775 prefix acl; 776 } 777 import ietf-yang-types { 778 prefix yang; 779 } 780 import ietf-inet-types { 781 prefix inet; 782 } 784 organization 785 "IETF OPSAWG (Ops Area) Working Group"; 786 contact 787 "WG Web: http://tools.ietf.org/wg/opsawg/ 788 WG List: opsawg@ietf.org 789 Author: Eliot Lear 790 lear@cisco.com 791 Author: Ralph Droms 792 rdroms@gmail.com 793 Author: Dan Romascanu 794 dromasca@gmail.com 796 "; 797 description 798 "This YANG module defines a component that augments the 799 IETF description of an access list. This specific module 800 focuses on additional filters that include local, model, 801 and same-manufacturer. 803 This module is intended to be serialized via JSON and stored 804 as a file, as described in RFC XXXX [RFC Editor to fill in with 805 this document #]. 807 Copyright (c) 2016,2017 IETF Trust and the persons 808 identified as the document authors. All rights reserved. 809 Redistribution and use in source and binary forms, with or 810 without modification, is permitted pursuant to, and subject 811 to the license terms contained in, the Simplified BSD 812 License set forth in Section 4.c of the IETF Trust's Legal 813 Provisions Relating to IETF Documents 814 (http://trustee.ietf.org/license-info). 815 This version of this YANG module is part of RFC XXXX; see 816 the RFC itself for full legal notices."; 818 revision 2017-09-15 { 819 description 820 "Initial proposed standard."; 821 reference 822 "RFC XXXX: Manufacturer Usage Description 823 Specification"; 824 } 826 typedef direction { 827 type enumeration { 828 enum "to-device" { 829 description 830 "packets or flows destined to the target 831 Thing"; 832 } 833 enum "from-device" { 834 description 835 "packets or flows destined from 836 the target Thing"; 837 } 838 } 839 description 840 "Which way are we talking about?"; 841 } 843 container mud { 844 presence "Enabled for this particular MUD-URL"; 845 description 846 "MUD related information, as specified 847 by RFC-XXXX [RFC Editor to fill in]."; 848 uses mud-grouping; 849 } 851 grouping mud-grouping { 852 description 853 "Information about when support end(ed), and 854 when to refresh"; 855 leaf mud-url { 856 type inet:uri; 857 mandatory true; 858 description 859 "This is the MUD-URL associated with the entry found 860 in a MUD file."; 861 } 862 leaf last-update { 863 type yang:date-and-time; 864 mandatory true; 865 description 866 "This is intended to be when the current MUD file 867 was generated. MUD Controllers SHOULD NOT check 868 for updates between this time plus cache validity"; 869 } 870 leaf cache-validity { 871 type uint8 { 872 range "1..168"; 873 } 874 units "hours"; 875 default "48"; 876 description 877 "The information retrieved from the MUD server is 878 valid for these many hours, after which it should 879 be refreshed. N.B. MUD controller implementations 880 need not discard MUD files beyond this period."; 881 } 882 leaf masa-server { 883 type inet:uri; 884 description 885 "The URI of the MASA server that network 886 elements should forward requests to for this Thing."; 887 } 888 leaf is-supported { 889 type boolean; 890 mandatory true; 891 description 892 "This boolean indicates whether or not the Thing is 893 currently supported by the manufacturer."; 894 } 895 leaf systeminfo { 896 type inet:uri; 897 description 898 "A URL to a description of this Thing. This 899 should be a brief localized description. The 900 reference text should be no more than octets. 902 systeminfo may be displayed to the user to 903 determine whether to allow the Thing on the 904 network."; 905 } 906 leaf-list extensions { 907 type string { 908 length "1..40"; 909 } 910 description 911 "A list of extension names that are used in this MUD 912 file. Each name is registered with the IANA and 913 described in an RFC."; 914 } 915 container from-device-policy { 916 description 917 "The policies that should be enforced on traffic 918 coming from the device. These policies are not 919 necessarily intended to be enforced at a single 920 point, but may be rendered by the controller to any 921 relevant enorcement points in the network or 922 elsewhere."; 923 uses access-lists; 924 } 925 container to-device-policy { 926 description 927 "The policies that should be enforced on traffic 928 going to the device. These policies are not 929 necessarily intended to be enforced at a single 930 point, but may be rendered by the controller to any 931 relevant enorcement points in the network or 932 elsewhere."; 933 uses access-lists; 934 } 935 } 937 grouping access-lists { 938 description 939 "A grouping for access lists in the context of device 940 policy."; 941 container access-lists { 942 description 943 "The access lists that should be applied to traffic 944 to or from the device."; 945 list access-list { 946 key "acl-name acl-type"; 947 description 948 "Each entry on this list refers to an ACL that 949 should be present in the overall access list 950 data model. Each ACL is identified by name and 951 type."; 952 leaf acl-name { 953 type leafref { 954 path "/acl:access-lists/acl:acl/acl:acl-name"; 955 } 956 description 957 "The name of the ACL for this entry."; 958 } 959 leaf acl-type { 960 type identityref { 961 base acl:acl-base; 962 } 963 description 964 "The type of the ACL for this entry. The name is 965 scoped ONLY to the MUD file, and may not be unique 966 in any other circumstance."; 967 } 968 } 969 } 970 } 972 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches" { 973 description 974 "adding abstractions to avoid need of IP addresses"; 975 container mud-acl { 976 description 977 "MUD-specific matches."; 978 leaf manufacturer { 979 type inet:host; 980 description 981 "A domain that is intended to match the authority 982 section of the MUD-URL. This node is used to specify 983 one or more manufacturers a device should 984 be authorized to access."; 985 } 986 leaf same-manufacturer { 987 type empty; 988 description 989 "This node matches the authority section of the MUD-URL 990 of a Thing. It is intended to grant access to all 991 devices with the same authority section."; 992 } 993 leaf model { 994 type inet:uri; 995 description 996 "Devices of the specified model type will match if 997 they have an identical MUD-URL."; 999 } 1000 leaf local-networks { 1001 type empty; 1002 description 1003 "IP addresses will match this node if they are 1004 considered local addresses. A local address may be 1005 a list of locally defined prefixes and masks 1006 that indicate a particular administrative scope."; 1007 } 1008 leaf controller { 1009 type inet:uri; 1010 description 1011 "This node names a class that has associated with it 1012 zero or more IP addresses to match against. These 1013 may be scoped to a manufacturer or via a standard 1014 URN."; 1015 } 1016 leaf my-controller { 1017 type empty; 1018 description 1019 "This node matches one or more network elements that 1020 have been configured to be the controller for this 1021 Thing, based on its MUD-URL."; 1022 } 1023 } 1024 } 1025 augment "/acl:access-lists/acl:acl/acl:aces/" + 1026 "acl:ace/acl:matches/acl:tcp-acl" { 1027 description 1028 "Adding domain names to matching"; 1029 leaf direction-initiated { 1030 type direction; 1031 description 1032 "This node matches based on which direction a 1033 connection was initiated. The means by which that 1034 is determined is discussed in this document."; 1035 } 1036 } 1037 } 1039 1041 7. The Domain Name Extension to the ACL Model 1043 This module specifies an extension to IETF-ACL model such that domain 1044 names may be referenced by augmenting the "matches" node. Different 1045 implementations may deploy differing methods to maintain the mapping 1046 between IP address and domain name, if indeed any are needed. 1047 However, the intent is that resources that are referred to using a 1048 name should be authorized (or not) within an access list. 1050 The structure of the change is as follows: 1052 module: ietf-acldns 1053 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/ 1054 acl:matches/acl:ipv4-acl: 1055 +--rw src-dnsname? inet:host 1056 +--rw dst-dnsname? inet:host 1057 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/ 1058 acl:matches/acl:ipv6-acl: 1059 +--rw src-dnsname? inet:host 1060 +--rw dst-dnsname? inet:host 1062 The choice of these particular points in the access-list model is 1063 based on the assumption that we are in some way referring to IP- 1064 related resources, as that is what the DNS returns. A domain name in 1065 our context is defined in [RFC6991]. The augmentations are 1066 replicated across IPv4 and IPv6 to allow MUD file authors the ability 1067 to control the IP version that the Thing may utilize. 1069 The following node are defined. 1071 7.1. source-dnsname 1073 The argument corresponds to a domain name of a source as specified by 1074 inet:host. A number of means may be used to resolve hosts. What is 1075 important is that such resolutions be consistent with ACLs required 1076 by Things to properly operate. 1078 7.2. destination-dnsname 1080 The argument corresponds to a domain name of a destination as 1081 specified by inet:host See the previous section relating to 1082 resolution. 1084 7.3. The ietf-acldns Model 1086 file "ietf-acldns@2017-09-15.yang" 1087 module ietf-acldns { 1088 yang-version 1.1; 1089 namespace "urn:ietf:params:xml:ns:yang:ietf-acldns"; 1090 prefix "ietf-acldns"; 1092 import ietf-access-control-list { 1093 prefix "acl"; 1094 } 1096 import ietf-inet-types { 1097 prefix "inet"; 1098 } 1100 organization 1101 "IETF OPSAWG (Ops Area) Working Group"; 1103 contact 1104 "WG Web: http://tools.ietf.org/wg/opsawg/ 1105 WG List: opsawg@ietf.org 1106 Author: Eliot Lear 1107 lear@cisco.com 1108 Author: Ralph Droms 1109 rdroms@gmail.com 1110 Author: Dan Romascanu 1111 dromasca@gmail.com 1112 "; 1114 description 1115 "This YANG module defines a component that augments the 1116 IETF description of an access list to allow dns names 1117 as matching criteria."; 1119 revision "2017-09-15" { 1120 description "Base version of dnsname extension of ACL model"; 1121 reference "RFC XXXX: Manufacturer Usage Description 1122 Specification"; 1123 } 1125 grouping dns-matches { 1126 description "Domain names for matching."; 1128 leaf src-dnsname { 1129 type inet:host; 1130 description "domain name to be matched against"; 1131 } 1132 leaf dst-dnsname { 1133 type inet:host; 1134 description "domain name to be matched against"; 1135 } 1136 } 1138 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/" + 1139 "acl:matches/acl:ipv4-acl" { 1140 description "Adding domain names to matching"; 1141 uses dns-matches; 1142 } 1144 augment "/acl:access-lists/acl:acl/" + 1145 "acl:aces/acl:ace/" + 1146 "acl:matches/acl:ipv6-acl" { 1147 description "Adding domain names to matching"; 1148 uses dns-matches; 1149 } 1150 } 1151 1153 8. MUD File Example 1155 This example contains two access lists that are intended to provide 1156 outbound access to a cloud service on TCP port 443. 1158 { 1159 "ietf-mud:mud": { 1160 "mud-url": "https://bms.example.com/.well-known/mud/v1/lightbulb", 1161 "last-update": "2017-09-20T15:49:18+02:00", 1162 "is-supported": true, 1163 "systeminfo": "https://bms.example.com/descriptions/lightbulb", 1164 "cache-validity": 48, 1165 "from-device-policy": { 1166 "access-lists": { 1167 "access-list": [ 1168 { 1169 "acl-name": "mud-54684-v6fr", 1170 "acl-type": "ietf-access-control-list:ipv6-acl" 1171 } 1172 ] 1173 } 1174 }, 1175 "to-device-policy": { 1176 "access-lists": { 1177 "access-list": [ 1178 { 1179 "acl-name": "mud-54684-v6to", 1180 "acl-type": "ietf-access-control-list:ipv6-acl" 1181 } 1182 ] 1183 } 1184 } 1185 }, 1186 "ietf-access-control-list:access-lists": { 1187 "acl": [ 1188 { 1189 "acl-name": "mud-54684-v6to", 1190 "acl-type": "ipv6-acl", 1191 "access-list-entries": { 1192 "ace": [ 1193 { 1194 "rule-name": "cl0-todev", 1195 "matches": { 1196 "ipv6-acl": { 1197 "ietf-acldns:src-dnsname": "service.bms.example.com", 1198 "protocol": 6, 1199 "source-port-range": { 1200 "lower-port": 443, 1201 "upper-port": 443 1202 } 1203 }, 1204 "tcp-acl": { 1205 "ietf-mud:direction-initiated": "from-device" 1206 } 1207 }, 1208 "actions": { 1209 "permit": [ 1210 null 1211 ] 1212 } 1213 } 1214 ] 1215 } 1216 }, 1217 { 1218 "acl-name": "mud-54684-v6fr", 1219 "acl-type": "ipv6-acl", 1220 "access-list-entries": { 1221 "ace": [ 1222 { 1223 "rule-name": "cl0-frdev", 1224 "matches": { 1225 "ipv6-acl": { 1226 "ietf-acldns:dst-dnsname": "service.bms.example.com", 1227 "protocol": 6, 1228 "destination-port-range": { 1229 "lower-port": 443, 1230 "upper-port": 443 1231 } 1232 }, 1233 "tcp-acl": { 1234 "ietf-mud:direction-initiated": "from-device" 1236 } 1237 }, 1238 "actions": { 1239 "permit": [ 1240 null 1241 ] 1242 } 1243 } 1244 ] 1245 } 1246 } 1247 ] 1248 } 1249 } 1251 In this example, two policies are declared, one from the Thing and 1252 the other to the Thing. Each policy names an access list that 1253 applies to the Thing, and one that applies from. Within each access 1254 list, access is permitted to packets flowing to or from the Thing 1255 that can be mapped to the domain name of "service.bms.example.com". 1256 For each access list, the enforcement point should expect that the 1257 thing initiated the connection. 1259 9. The MUD URL DHCP Option 1261 The IPv4 MUD URL client option has the following format: 1263 +------+-----+------------------------------ 1264 | code | len | MUD URL 1265 +------+-----+------------------------------ 1267 Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single 1268 octet that indicates the length of the URL in octets. MUD URL is a 1269 URL. MUD URLs MUST NOT exceed 255 octets. 1271 The IPv6 MUD URL client option has the following format: 1273 0 1 2 3 1274 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1276 | OPTION_MUD_URL_V6 | option-length | 1277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1278 | MUD URL | 1279 | ... | 1280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1282 OPTION_MUD_URL_V6 (112; assigned by IANA). 1284 option-length contains the length of the URL in octets. 1286 The intent of this option is to provide both a new Thing classifier 1287 to the network as well as some recommended configuration to the 1288 routers that implement policy. However, it is entirely the purview 1289 of the network system as managed by the network administrator to 1290 decide what to do with this information. The key function of this 1291 option is simply to identify the type of Thing to the network in a 1292 structured way such that the policy can be easily found with existing 1293 toolsets. 1295 9.1. Client Behavior 1297 A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit 1298 DHCPv6 option. These options are singletons, as specified in 1299 [RFC7227]. Because clients are intended to have at most one MUD URL 1300 associated with them, they may emit at most one MUD URL option via 1301 DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4 1302 and v6 DHCP options are emitted, the same URL MUST be used. 1304 Clients SHOULD log or otherwise report improper acknowledgments from 1305 servers, but they MUST NOT modify their MUD URL configuration based 1306 on a server's response. The server's response is only an 1307 acknowledgment that the server has processed the option, and promises 1308 no specific network behavior to the client. In particular, it may 1309 not be possible for the server to retrieve the file associated with 1310 the MUD URL, or the local network administration may not wish to use 1311 the usage description. Neither of these situations should be 1312 considered in any way exceptional. 1314 9.2. Server Behavior 1316 A DHCP server may ignore these options or take action based on 1317 receipt of these options. If a server successfully parses the option 1318 and the URL, it MUST return the option with length field set to zero 1319 and a corresponding null URL field as an acknowledgment. Even in 1320 this circumstance, no specific network behavior is guaranteed. When 1321 a server consumes this option, it will either forward the URL and 1322 relevant client information (such as the gateway address or giaddr) 1323 to a network management system, or it will retrieve the usage 1324 description itself by resolving the URL. 1326 DHCP servers may implement MUD functionality themselves or they may 1327 pass along appropriate information to a network management system or 1328 MUD controller. A DHCP server that does process the MUD URL MUST 1329 adhere to the process specified in [RFC2818] and [RFC5280] to 1330 validate the TLS certificate of the web server hosting the MUD file. 1331 Those servers will retrieve the file, process it, create and install 1332 the necessary configuration on the relevant network element. Servers 1333 SHOULD monitor the gateway for state changes on a given interface. A 1334 DHCP server that does not provide MUD functionality and has forwarded 1335 a MUD URL to a MUD controller MUST notify the MUD controller of any 1336 corresponding change to the DHCP state of the client (such as 1337 expiration or explicit release of a network address lease). 1339 9.3. Relay Requirements 1341 There are no additional requirements for relays. 1343 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 1345 This section defines an X.509 non-critical certificate extension that 1346 contains a single Uniform Resource Locator (URL) that points to an 1347 on-line Manufacturer Usage Description concerning the certificate 1348 subject. URI must be represented as described in Section 7.4 of 1349 [RFC5280]. 1351 Any Internationalized Resource Identifiers (IRIs) MUST be mapped to 1352 URIs as specified in Section 3.1 of [RFC3987] before they are placed 1353 in the certificate extension. 1355 The semantics of the URL are defined Section 5 of this document. 1357 The choice of id-pe is based on guidance found in Section 4.2.2 of 1358 [RFC5280]: 1360 These extensions may be used to direct applications to on-line 1361 information about the issuer or the subject. 1363 The MUD URL is precisely that: online information about the 1364 particular subject. 1366 The new extension is identified as follows: 1368 1370 MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) 1371 internet(1) security(5) mechanisms(5) pkix(7) 1372 id-mod(0) id-mod-mudURLExtn2016(88) } 1374 DEFINITIONS IMPLICIT TAGS ::= BEGIN 1376 -- EXPORTS ALL -- 1378 IMPORTS 1379 EXTENSION 1380 FROM PKIX-CommonTypes-2009 1381 { iso(1) identified-organization(3) dod(6) internet(1) 1382 security(5) mechanisms(5) pkix(7) id-mod(0) 1383 id-mod-pkixCommon-02(57) } 1385 id-pe 1386 FROM PKIX1Explicit-2009 1387 { iso(1) identified-organization(3) dod(6) internet(1) 1388 security(5) mechanisms(5) pkix(7) id-mod(0) 1389 id-mod-pkix1-explicit-02(51) } ; 1390 MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... } 1391 ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax 1392 IDENTIFIED BY id-pe-mud-url } 1394 id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 } 1396 MUDURLSyntax ::= IA5String 1398 END 1400 1402 While this extension can appear in either an 802.AR manufacturer 1403 certificate (IDevID) or deployment certificate (LDevID), of course it 1404 is not guaranteed in either, nor is it guaranteed to be carried over. 1405 It is RECOMMENDED that MUD controller implementations maintain a 1406 table that maps a Thing to its MUD-URL based on IDevIDs. 1408 11. The Manufacturer Usage Description LLDP extension 1410 The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop 1411 vendor-neutral link layer protocol used by end hosts network Things 1412 for advertising their identity, capabilities, and neighbors on an 1413 IEEE 802 local area network. Its Type-Length-Value (TLV) design 1414 allows for 'vendor-specific' extensions to be defined. IANA has a 1415 registered IEEE 802 organizationally unique identifier (OUI) defined 1416 as documented in [RFC7042]. The MUD LLDP extension uses a subtype 1417 defined in this document to carry the MUD URL. 1419 The LLDP vendor specific frame has the following format: 1421 +--------+--------+----------+---------+-------------- 1422 |TLV Type| len | OUI |subtype | MUD URL 1423 | =127 | |= 00 00 5E| = 1 | 1424 |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets) 1425 +--------+--------+----------+---------+-------------- 1427 where: 1429 o TLV Type = 127 indicates a vendor-specific TLV 1431 o len - indicates the TLV string length 1433 o OUI = 00 00 5E is the organizationally unique identifier of IANA 1435 o subtype = 1 (to be assigned by IANA for the MUD URL) 1437 o MUD URL - the length MUST NOT exceed 255 octets 1439 The intent of this extension is to provide both a new Thing 1440 classifier to the network as well as some recommended configuration 1441 to the routers that implement policy. However, it is entirely the 1442 purview of the network system as managed by the network administrator 1443 to decide what to do with this information. The key function of this 1444 extension is simply to identify the type of Thing to the network in a 1445 structured way such that the policy can be easily found with existing 1446 toolsets. 1448 Hosts, routers, or other network Things that implement this option 1449 are intended to have at most one MUD URL associated with them, so 1450 they may transmit at most one MUD URL value. 1452 Hosts, routers, or other network Things that implement this option 1453 may ignore these options or take action based on receipt of these 1454 options. For example they may fill in information in the respective 1455 extensions of the LLDP Management Information Base (LLDP MIB). LLDP 1456 operates in a one-way direction. LLDPDUs are not exchanged as 1457 information requests by one Thing and response sent by another Thing. 1458 The other Things do not acknowledge LLDP information received from a 1459 Thing. No specific network behavior is guaranteed. When a Thing 1460 consumes this extension, it may either forward the URL and relevant 1461 remote Thing information to a MUD controller, or it will retrieve the 1462 usage description by resolving the URL in accordance with normal HTTP 1463 semantics. 1465 12. Creating and Processing of Signed MUD Files 1467 Because MUD files contain information that may be used to configure 1468 network access lists, they are sensitive. To insure that they have 1469 not been tampered with, it is important that they be signed. We make 1470 use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for 1471 this purpose. 1473 12.1. Creating a MUD file signature 1475 A MUD file MUST be signed using CMS as an opaque binary object. In 1476 order to make successful verification more likely, intermediate 1477 certificates SHOULD be included. The signature is stored at the same 1478 location as the MUD URL but with the suffix of ".p7s". Signatures 1479 are transferred using content-type "application/pkcs7-signature". 1481 For example: 1483 % openssl cms -sign -signer mancertfile -inkey mankey \ 1484 -in mudfile -binary -outform DER - \ 1485 -certfile intermediatecert -out mudfile.p7s 1487 Note: A MUD file may need to be re-signed if the signature expires. 1489 12.2. Verifying a MUD file signature 1491 Prior to retrieving a MUD file the MUD controller SHOULD retrieve the 1492 MUD signature file using the MUD URL with a suffix of ".p7s". For 1493 example, if the MUD URL is "https://example.com/.well-known/v1/ 1494 modela", the MUD signature URL will be "https://example.com/.well- 1495 known/v1/modela.p7s". 1497 Upon retrieving a MUD file, a MUD controller MUST validate the 1498 signature of the file before continuing with further processing. A 1499 MUD controller MUST cease processing of that file it cannot validate 1500 the chain of trust to a known trust anchor until an administrator has 1501 given approval. 1503 The purpose of the signature on the file is to assign accountability 1504 to an entity, whose reputation can be used to guide administrators on 1505 whether or not to accept a given MUD file. It is already common 1506 place to check web reputation on the location of a server on which a 1507 file resides. While it is likely that the manufacturer will be the 1508 signer of the file, this is not strictly necessary, and may not be 1509 desirable. For one thing, in some environments, integrators may 1510 install their own certificates. For another, what is more important 1511 is the accountability of the recommendation, and not the 1512 cryptographic relationship between the device and the file. 1514 An example: 1516 % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile 1518 Note the additional step of verifying the common trust root. 1520 13. Extensibility 1522 One of our design goals is to see that MUD files are able to be 1523 understood by as broad a cross-section of systems as is possible. 1524 Coupled with the fact that we have also chosen to leverage existing 1525 mechanisms, we are left with no ability to negotiate extensions and a 1526 limited desire for those extensions in any event. A such, a two-tier 1527 extensibility framework is employed, as follows: 1529 1. At a coarse grain, a protocol version is included in a MUD URL. 1530 This memo specifies MUD version 1. Any and all changes are 1531 entertained when this version is bumped. Transition approaches 1532 between versions would be a matter for discussion in future 1533 versions. 1535 2. At a finer grain, only extensions that would not incur additional 1536 risk to the Thing are permitted. Specifically, adding nodes to 1537 the mud container is permitted with the understanding that such 1538 additions will be ignored by unaware implementations. Any such 1539 extensions SHALL be standardized through the IETF process, and 1540 MUST be named in the "extensions" list. MUD controllers MUST 1541 ignore YANG nodes they do not understand and SHOULD create an 1542 exception to be resolved by an administrator, so as to avoid any 1543 policy inconsistencies. 1545 14. Deployment Considerations 1547 Because MUD consists of a number of architectural building blocks, it 1548 is possible to assemble different deployment scenarios. One key 1549 aspect is where to place policy enforcement. In order to protect the 1550 Thing from other Things within a local deployment, policy can be 1551 enforced on the nearest switch or access point. In order to limit 1552 unwanted traffic within a network, it may also be advisable to 1553 enforce policy as close to the Internet as possible. In some 1554 circumstances, policy enforcement may not be available at the closest 1555 hop. At that point, the risk of so-called east-west infection is 1556 increased to the number of Things that are able to communicate 1557 without protection. 1559 A caution about some of the classes: admission of a Thing into the 1560 "manufacturer" and "same-manufacturer" class may have impact on 1561 access of other Things. Put another way, the admission may grow the 1562 access-list on switches connected to other Things, depending on how 1563 access is managed. Some care should be given on managing that 1564 access-list growth. Alternative methods such as additional network 1565 segmentation can be used to keep that growth within reason. 1567 15. Security Considerations 1569 Based on how a MUD-URL is emitted, a Thing may be able to lie about 1570 what it is, thus gaining additional network access. There are 1571 several means to limit risk in this case. The most obvious is to 1572 only believe Things that make use of certificate-based authentication 1573 such as IEEE 802.1AR certificates. When those certificates are not 1574 present, Things claiming to be of a certain manufacturer SHOULD NOT 1575 be included in that manufacturer grouping without additional 1576 validation of some form. This will occur when it makes use of 1577 primitives such as "manufacturer" for the purpose of accessing Things 1578 of a particular type. Similarly, network management systems may be 1579 able to fingerprint the Thing. In such cases, the MUD-URL can act as 1580 a classifier that can be proven or disproven. Fingerprinting may 1581 have other advantages as well: when 802.1AR certificates are used, 1582 because they themselves cannot change, fingerprinting offers the 1583 opportunity to add artificats to the MUD-URL. The meaning of such 1584 artifacts is left as future work. 1586 Network management systems SHOULD NOT accept a usage description for 1587 a Thing with the same MAC address that has indicated a change of 1588 authority without some additional validation (such as review by a 1589 network administrator). New Things that present some form of 1590 unauthenticated MUD URL SHOULD be validated by some external means 1591 when they would be otherwise be given increased network access. 1593 It may be possible for a rogue manufacturer to inappropriately 1594 exercise the MUD file parser, in order to exploit a vulnerability. 1595 There are three recommended approaches to address this threat. The 1596 first is to validate the signature of the MUD file. The second is to 1597 have a system do a primary scan of the file to ensure that it is both 1598 parseable and believable at some level. MUD files will likely be 1599 relatively small, to start with. The number of ACEs used by any 1600 given Thing should be relatively small as well. It may also be 1601 useful to limit retrieval of MUD URLs to only those sites that are 1602 known to have decent web or domain reputations. 1604 Use of a URL necessitates the use of domain names. If a domain name 1605 changes ownership, the new owner of that domain may be able to 1606 provide MUD files that MUD controllers would consider valid. There 1607 are a few approaches that can mitigate this attack. First, MUD 1608 controllers SHOULD cache certificates used by the MUD file server. 1609 When a new certificate is retrieved for whatever reason, the MUD 1610 controller should check to see if ownership of the domain has 1611 changed. A fair programmatic approximation of this is when the name 1612 servers for the domain have changed. If the actual MUD file has 1613 changed, the controller MAY check the WHOIS database to see if 1614 registration ownership of a domain has changed. If a change has 1615 occured, or if for some reason it is not possible to determine 1616 whether ownership has changed, further review may be warranted. 1617 Note, this remediation does not take into account the case of a Thing 1618 that was produced long ago and only recently fielded, or the case 1619 where a new MUD controller has been installed. 1621 It may not be possible for a MUD controller to retrieve a MUD file at 1622 any given time. Should a MUD controller fail to retrieve a MUD file, 1623 it SHOULD consider the existing one safe to use, at least for a time. 1624 After some period, it SHOULD log that it has been unable to retrieve 1625 the file. There may be very good reasons for such failures, 1626 including the possibility that the MUD controller is in an off-line 1627 environment, the local Internet connection has failed, or the remote 1628 Internet connection has failed. It is also possible that an attacker 1629 is attempting to prevent onboarding of a device. It is a local 1630 deployment decision as to whether or not devices may be onboarded in 1631 the face of such failures. 1633 The release of a MUD URL by a Thing reveals what the Thing is, and 1634 provides an attacker with guidance on what vulnerabilities may be 1635 present. 1637 While the MUD URL itself is not intended to be unique to a specific 1638 Thing, the release of the URL may aid an observer in identifying 1639 individuals when combined with other information. This is a privacy 1640 consideration. 1642 In addressing both of these concerns, implementors should take into 1643 account what other information they are advertising through 1644 mechanisms such as mDNS[RFC6872], how a Thing might otherwise be 1645 identified, perhaps through how it behaves when it is connected to 1646 the network, whether a Thing is intended to be used by individuals or 1647 carry personal identifying information, and then apply appropriate 1648 data minimization techniques. One approach is to make use of TEAP 1649 [RFC7170] as the means to share information with authorized 1650 components in the network. Network Things may also assist in 1651 limiting access to the MUD-URL through the use of mechanisms such as 1652 DHCPv6-Shield [RFC7610]. 1654 Please note that the security considerations mentioned in Section 4.7 1655 of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case 1656 because the YANG serialization is not intended to be accessed via 1657 NETCONF. However, for those who try to instantiate this model in a 1658 Thing via NETCONF, all objects in each model in this draft exhibit 1659 similar security characteristics as [I-D.ietf-netmod-acl-model]. The 1660 basic purpose of MUD is to configure access, and so by its very 1661 nature can be disruptive if used by unauthorized parties. 1663 16. IANA Considerations 1665 16.1. YANG Module Registrations 1667 The following YANG modules are requested to be registred in the "IANA 1668 Module Names" registry: 1670 The ietf-mud module: 1672 o Name: ietf-mud 1674 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud 1676 o Prefix: ief-mud 1678 o Reference: This memo 1680 The ietf-acldns module: 1682 o Name: ietf-acldns 1684 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns 1686 o Prefix: ietf-acldns 1688 o Reference: This memo 1690 16.2. DHCPv4 and DHCPv6 Options 1692 The IANA has allocated option 161 in the Dynamic Host Configuration 1693 Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry 1694 for the MUD DHCPv4 option. 1696 IANA is requested to allocated the DHCPv4 and v6 options as specified 1697 in Section 9. 1699 16.3. PKIX Extensions 1701 IANA is kindly requested to make the following assignments for: 1703 o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for 1704 PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). 1706 o id-pe-mud-url object identifier from the "SMI Security for PKIX 1707 Certificate Extension" registry (1.3.6.1.5.5.7.1). 1709 The use of these values is specified in Section 10. 1711 16.4. Well Known URI Suffix 1713 The IANA has allocated the URL suffix of "mud" as follows: 1715 o URI Suffix: "mud" o Specification documents: this document o 1716 Related information: n/a 1718 16.5. MIME Media-type Registration for MUD files 1720 The following media-type is defined for transfer of MUD file: 1722 o Type name: application 1723 o Subtype name: mud+json 1724 o Required parameters: n/a 1725 o Optional parameters: n/a 1726 o Encoding considerations: 8bit; application/mud+json values 1727 are represented as a JSON object; UTF-8 encoding SHOULD be 1728 employed. 1729 o Security considerations: See {{secon}} of this document. 1730 o Interoperability considerations: n/a 1731 o Published specification: this document 1732 o Applications that use this media type: MUD controllers as 1733 specified by this document. 1734 o Fragment identifier considerations: n/a 1735 o Additional information: 1737 Magic number(s): n/a 1738 File extension(s): n/a 1739 Macintosh file type code(s): n/a 1741 o Person & email address to contact for further information: 1742 Eliot Lear , Ralph Droms 1743 o Intended usage: COMMON 1744 o Restrictions on usage: none 1745 o Author: 1746 Eliot Lear 1747 Ralph Droms 1748 o Change controller: IESG 1749 o Provisional registration? (standards tree only): No. 1751 16.6. LLDP IANA TLV Subtype Registry 1753 IANA is requested to create a new registry for IANA Link Layer 1754 Discovery Protocol (LLDP) TLV subtype values. The recommended policy 1755 for this registry is Expert Review. The maximum number of entries in 1756 the registry is 256. 1758 IANA is required to populate the initial registry with the value: 1760 LLDP subtype value = 1 (All the other 255 values should be initially 1761 marked as 'Unassigned'.) 1763 Description = the Manufacturer Usage Description (MUD) Uniform 1764 Resource Locator (URL) 1766 Reference = < this document > 1768 16.7. The MUD Well Known Universal Resource Name (URNs) 1770 The following parameter registry is requested to be added in 1771 accordance with [RFC3553] 1773 Registry name: "urn:ietf:params:mud" is requested. 1774 Specification: this document 1775 Repository: this document 1776 Index value: Encoded identically to a TCP/UDP port service 1777 name, as specified in Section 5.1 of [RFC6335] 1779 The following entries should be added to the "urn:ietf:params:mud" 1780 name space: 1782 "urn:ietf:params:mud:dns" refers to the service specified by 1783 [RFC1123]. "urn:ietf:params:mud:ntp" refers to the service specified 1784 by [RFC5905]. 1786 16.8. Extensions Registry 1788 The IANA is requested to establish a registry of extensions as 1789 follows: 1791 Registry name: MUD extensions registry 1792 Registry policy: Standards action 1793 Standard reference: document 1794 Extension name: UTF-8 encoded string, not to exceed 40 characters. 1796 Each extension MUST follow the rules specified in this specification. 1797 As is usual, the IANA issues early allocations based in accordance 1798 with [RFC7120]. 1800 17. Acknowledgments 1802 The authors would like to thank Einar Nilsen-Nygaard, who 1803 singlehandedly updated the model to match the updated ACL model, 1804 Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm, 1805 John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk 1806 Birkholz, Adam Montville, and Robert Sparks for their valuable advice 1807 and reviews. Russ Housley entirely rewrote Section 10 to be a 1808 complete module. Adrian Farrel provided the basis for privacy 1809 considerations text. Kent Watson provided a thorough review of the 1810 architecture and the YANG model. The remaining errors in this work 1811 are entirely the responsibility of the authors. 1813 18. References 1815 18.1. Normative References 1817 [I-D.ietf-anima-bootstrapping-keyinfra] 1818 Pritikin, M., Richardson, M., Behringer, M., Bjarnason, 1819 S., and K. Watsen, "Bootstrapping Remote Secure Key 1820 Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- 1821 keyinfra-07 (work in progress), July 2017. 1823 [I-D.ietf-netmod-acl-model] 1824 Jethanandani, M., Huang, L., Agarwal, S., and D. Blair, 1825 "Network Access Control List (ACL) YANG Data Model", 1826 draft-ietf-netmod-acl-model-13 (work in progress), 1827 September 2017. 1829 [IEEE8021AB] 1830 Institute for Electrical and Electronics Engineers, "IEEE 1831 Standard for Local and Metropolitan Area Networks-- 1832 Station and Media Access Control Connectivity Discovery", 1833 n.d.. 1835 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1836 Application and Support", STD 3, RFC 1123, 1837 DOI 10.17487/RFC1123, October 1989, . 1840 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1841 Requirement Levels", BCP 14, RFC 2119, 1842 DOI 10.17487/RFC2119, March 1997, . 1845 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1846 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1847 . 1849 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1850 DOI 10.17487/RFC2818, May 2000, . 1853 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1854 C., and M. Carney, "Dynamic Host Configuration Protocol 1855 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1856 2003, . 1858 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1859 Levkowetz, Ed., "Extensible Authentication Protocol 1860 (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, 1861 . 1863 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1864 Resource Identifier (URI): Generic Syntax", STD 66, 1865 RFC 3986, DOI 10.17487/RFC3986, January 2005, 1866 . 1868 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1869 Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, 1870 January 2005, . 1872 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1873 Housley, R., and W. Polk, "Internet X.509 Public Key 1874 Infrastructure Certificate and Certificate Revocation List 1875 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1876 . 1878 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, 1879 RFC 5652, DOI 10.17487/RFC5652, September 2009, 1880 . 1882 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1883 "Network Time Protocol Version 4: Protocol and Algorithms 1884 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1885 . 1887 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 1888 the Network Configuration Protocol (NETCONF)", RFC 6020, 1889 DOI 10.17487/RFC6020, October 2010, . 1892 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1893 Cheshire, "Internet Assigned Numbers Authority (IANA) 1894 Procedures for the Management of the Service Name and 1895 Transport Protocol Port Number Registry", BCP 165, 1896 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1897 . 1899 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 1900 RFC 6991, DOI 10.17487/RFC6991, July 2013, 1901 . 1903 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 1904 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 1905 2014, . 1907 [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 1908 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 1909 BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, 1910 . 1912 [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield: 1913 Protecting against Rogue DHCPv6 Servers", BCP 199, 1914 RFC 7610, DOI 10.17487/RFC7610, August 2015, 1915 . 1917 18.2. Informative References 1919 [FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls", 1920 January 1995. 1922 [I-D.ietf-netmod-rfc6087bis] 1923 Bierman, A., "Guidelines for Authors and Reviewers of YANG 1924 Data Model Documents", draft-ietf-netmod-rfc6087bis-14 1925 (work in progress), September 2017. 1927 [IEEE8021AR] 1928 Institute for Electrical and Electronics Engineers, 1929 "Secure Device Identity", 1998. 1931 [ISO.8601.1988] 1932 International Organization for Standardization, "Data 1933 elements and interchange formats - Information interchange 1934 - Representation of dates and times", ISO Standard 8601, 1935 June 1988. 1937 [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic 1938 Technology and the Internet", BCP 200, RFC 1984, 1939 DOI 10.17487/RFC1984, August 1996, . 1942 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 1943 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 1944 . 1946 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 1947 IETF URN Sub-namespace for Registered Protocol 1948 Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June 1949 2003, . 1951 [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security 1952 Capabilities in Customer Premises Equipment (CPE) for 1953 Providing Residential IPv6 Internet Service", RFC 6092, 1954 DOI 10.17487/RFC6092, January 2011, . 1957 [RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur, 1958 H., and O. Festor, "The Common Log Format (CLF) for the 1959 Session Initiation Protocol (SIP): Framework and 1960 Information Model", RFC 6872, DOI 10.17487/RFC6872, 1961 February 2013, . 1963 [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and 1964 IETF Protocol and Documentation Usage for IEEE 802 1965 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, 1966 October 2013, . 1968 [RFC7170] Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, 1969 "Tunnel Extensible Authentication Protocol (TEAP) Version 1970 1", RFC 7170, DOI 10.17487/RFC7170, May 2014, 1971 . 1973 [RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson, 1974 "Architectural Considerations in Smart Object Networking", 1975 RFC 7452, DOI 10.17487/RFC7452, March 2015, 1976 . 1978 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 1979 Reddy, "Port Control Protocol (PCP) Server Selection", 1980 RFC 7488, DOI 10.17487/RFC7488, March 2015, 1981 . 1983 Appendix A. Changes from Earlier Versions 1985 RFC Editor to remove this section prior to publication. 1987 Draft -10 to -11: 1989 o Example corrections 1991 o Typo 1993 o Fix two lists. 1995 o Addition of 'any-acl' and 'mud-acl' in the list of allowed 1996 features. 1998 o Clarification of what should be in a MUD file. 2000 Draft -09 to -10: 2002 o AD input. 2004 o Correct dates. 2006 o Add compliance sentence as to which ACL module features are 2007 implemented. 2009 Draft -08 to -09: 2011 o Resolution of Security Area review, IoT directorate review, GenART 2012 review, YANG doctors review. 2014 o change of YANG structure to address mandatory nodes. 2016 o Terminology cleanup. 2018 o specify out extra portion of MUD-URL. 2020 o consistency changes. 2022 o improved YANG descriptions. 2024 o Remove extra revisions. 2026 o Track ACL model changes. 2028 o Additional cautions on use of ACL model; further clarifications on 2029 extensions. 2031 Draft -07 to -08: 2033 o a number of editorials corrected. 2035 o definition of MUD file tweaked. 2037 Draft -06 to -07: 2039 o Examples updated. 2041 o Additional clarification for direction-initiated. 2043 o Additional implementation guidance given. 2045 Draft -06 to -07: 2047 o Update models to match new ACL model 2048 o extract directionality from the ACL, introducing a new device 2049 container. 2051 Draft -05 to -06: 2053 o Make clear that this is a component architecture (Polk and Watson) 2055 o Add order of operations (Watson) 2057 o Add extensions leaf-list (Pritikin) 2059 o Remove previous-mud-file (Watson) 2061 o Modify text in last-update (Watson) 2063 o Clarify local networks (Weis, Watson) 2065 o Fix contact info (Watson) 2067 o Terminology clarification (Weis) 2069 o Advice on how to handle LDevIDs (Watson) 2071 o Add deployment considerations (Watson) 2073 o Add some additional text about fingerprinting (Watson) 2075 o Appropriate references to 6087bis (Watson) 2077 o Change systeminfo to a URL to be referenced (Lear) 2079 Draft -04 to -05: * syntax error correction 2081 Draft -03 to -04: * Re-add my-controller 2083 Draft -02 to -03: * Additional IANA updates * Format correction in 2084 YANG. * Add reference to TEAP. 2086 Draft -01 to -02: * Update IANA considerations * Accept Russ Housley 2087 rewrite of X.509 text * Include privacy considerations text * Redo 2088 the URL limit. Still 255 bytes, but now stated in the URL 2089 definition. * Change URI registration to be under urn:ietf:params 2091 Draft -00 to -01: * Fix cert trust text. * change supportInformation 2092 to meta-info * Add an informational element in. * add urn registry 2093 and create first entry * add default elements 2095 Appendix B. Default MUD nodes 2097 What follows is the portion of a MUD file that permits DNS traffic to 2098 a controller that is registered with the URN 2099 "urn:ietf:params:mud:dns" and traffic NTP to a controller that is 2100 registered "urn:ietf:params:mud:ntp". This is considered the default 2101 behavior and the ACEs are in effect appended to whatever other ACEs. 2102 To block DNS or NTP one repeats the matching statement but replace 2103 "permit" with deny. Because ACEs are processed in the order they are 2104 received, the defaults would not be reached. A MUD controller might 2105 further decide to optimize to simply not include the defaults when 2106 they are overriden. 2108 The access-list component of the MUD entry is included below. 2110 "ietf-access-control-list:access-lists": { 2111 "acl": [ 2112 { 2113 "acl-name": "mud-85666-v4to", 2114 "acl-type": "ipv4-acl", 2115 "aces": { 2116 "ace": [ 2117 { 2118 "rule-name": "ent0-todev", 2119 "matches": { 2120 "ietf-mud:mud-acl": { 2121 "controller": "urn:ietf:params:mud:dns" 2122 }, 2123 "ipv4-acl": { 2124 "protocol": 17, 2125 "source-port-range": { 2126 "lower-port": 53, 2127 "upper-port": 53 2128 } 2129 } 2130 }, 2131 "actions": { 2132 "permit": [ 2133 null 2134 ] 2135 } 2136 }, 2137 { 2138 "rule-name": "ent1-todev", 2139 "matches": { 2140 "ietf-mud:mud-acl": { 2141 "controller": "urn:ietf:params:mud:ntp" 2142 }, 2143 "ipv4-acl": { 2144 "protocol": 17, 2145 "source-port-range": { 2146 "lower-port": 123, 2147 "upper-port": 123 2148 } 2149 } 2150 }, 2151 "actions": { 2152 "permit": [ 2153 null 2154 ] 2155 } 2156 } 2157 ] 2158 } 2159 }, 2160 { 2161 "acl-name": "mud-85666-v4fr", 2162 "acl-type": "ipv4-acl", 2163 "aces": { 2164 "ace": [ 2165 { 2166 "rule-name": "ent0-frdev", 2167 "matches": { 2168 "ietf-mud:mud-acl": { 2169 "controller": "urn:ietf:params:mud:dns" 2170 }, 2171 "ipv4-acl": { 2172 "protocol": 17, 2173 "destination-port-range": { 2174 "lower-port": 53, 2175 "upper-port": 53 2176 } 2177 } 2178 }, 2179 "actions": { 2180 "permit": [ 2181 null 2182 ] 2183 } 2184 }, 2185 { 2186 "rule-name": "ent1-frdev", 2187 "matches": { 2188 "ietf-mud:mud-acl": { 2189 "controller": "urn:ietf:params:mud:ntp" 2190 }, 2191 "ipv4-acl": { 2192 "protocol": 17, 2193 "destination-port-range": { 2194 "lower-port": 123, 2195 "upper-port": 123 2196 } 2197 } 2198 }, 2199 "actions": { 2200 "permit": [ 2201 null 2202 ] 2203 } 2204 } 2205 ] 2206 } 2207 }, 2208 { 2209 "acl-name": "mud-85666-v6to", 2210 "acl-type": "ipv6-acl", 2211 "access-list-entries": { 2212 "ace": [ 2213 { 2214 "rule-name": "ent0-todev", 2215 "matches": { 2216 "ietf-mud:mud-acl": { 2217 "controller": "urn:ietf:params:mud:dns" 2218 }, 2219 "ipv6-acl": { 2220 "protocol": 17, 2221 "source-port-range": { 2222 "lower-port": 53, 2223 "upper-port": 53 2224 } 2225 } 2226 }, 2227 "actions": { 2228 "permit": [ 2229 null 2230 ] 2231 } 2232 }, 2233 { 2234 "rule-name": "ent1-todev", 2235 "matches": { 2236 "ietf-mud:mud-acl": { 2237 "controller": "urn:ietf:params:mud:ntp" 2238 }, 2239 "ipv6-acl": { 2240 "protocol": 17, 2241 "source-port-range": { 2242 "lower-port": 123, 2243 "upper-port": 123 2244 } 2245 } 2246 }, 2247 "actions": { 2248 "permit": [ 2249 null 2250 ] 2251 } 2252 } 2253 ] 2254 } 2255 }, 2256 { 2257 "acl-name": "mud-85666-v6fr", 2258 "acl-type": "ipv6-acl", 2259 "access-list-entries": { 2260 "ace": [ 2261 { 2262 "rule-name": "ent0-frdev", 2263 "matches": { 2264 "ietf-mud:mud-acl": { 2265 "controller": "urn:ietf:params:mud:dns" 2266 }, 2267 "ipv6-acl": { 2268 "protocol": 17, 2269 "destination-port-range": { 2270 "lower-port": 53, 2271 "upper-port": 53 2272 } 2273 } 2274 }, 2275 "actions": { 2276 "permit": [ 2277 null 2278 ] 2279 } 2280 }, 2281 { 2282 "rule-name": "ent1-frdev", 2283 "matches": { 2284 "ietf-mud:mud-acl": { 2285 "controller": "urn:ietf:params:mud:ntp" 2286 }, 2287 "ipv6-acl": { 2288 "protocol": 17, 2289 "destination-port-range": { 2290 "lower-port": 123, 2291 "upper-port": 123 2292 } 2293 } 2294 }, 2295 "actions": { 2296 "permit": [ 2297 null 2298 ] 2299 } 2300 } 2301 ] 2302 } 2303 } 2304 ] 2305 } 2307 Appendix C. A Sample Extension: DETNET-indicator 2309 In this sample extension we augment the core MUD model to indicate 2310 whether the device implements DETNET. If a device later attempts to 2311 make use of DETNET, an notification or exception might be generated. 2312 Note that this example is intended only for illustrative purposes. 2314 Extension Name: "Example-Extension" (to be used in the extensions list) 2315 Standard: this document (but do not register the example) 2317 This extension augments the MUD model to include a single node, using 2318 the following sample module that has the following tree structure: 2320 module: ietf-mud-detext-example 2321 augment /ietf-mud:mud: 2322 +--rw is-detnet-required? boolean 2324 The model is defined as follows: 2326 file "ietf-mud-detext-example@2016-09-07.yang" 2327 module ietf-mud-detext-example { 2328 yang-version 1.1; 2329 namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example"; 2330 prefix ietf-mud-detext-example; 2331 import ietf-mud { 2332 prefix ietf-mud; 2333 } 2335 organization 2336 "IETF OPSAWG (Ops Area) Working Group"; 2337 contact 2338 "WG Web: http://tools.ietf.org/wg/opsawg/ 2339 WG List: opsawg@ietf.org 2340 Author: Eliot Lear 2341 lear@cisco.com 2342 Author: Ralph Droms 2343 rdroms@gmail.com 2344 Author: Dan Romascanu 2345 dromasca@gmail.com 2347 "; 2348 description 2349 "Sample extension to a MUD module to indicate a need 2350 for DETNET support."; 2352 revision 2017-09-05 { 2353 description 2354 "Initial revision."; 2355 reference 2356 "RFC XXXX: Manufacturer Usage Description 2357 Specification"; 2358 } 2360 augment "/ietf-mud:mud" { 2361 description 2362 "This adds a simple extension for a manufacturer 2363 to indicate whether DETNET is required by a 2364 device."; 2365 leaf is-detnet-required { 2366 type boolean; 2367 description 2368 "This value will equal true if a device requires 2369 detnet to properly function"; 2370 } 2371 } 2372 } 2373 2375 Using the previous example, we now show how the extension would be 2376 expressed: 2378 { 2379 "ietf-mud:mud": { 2380 "mud-url": "https://bms.example.com/.well-known/mud/v1/lightbulb", 2381 "last-update": "2017-09-20T15:49:18+02:00", 2382 "is-supported": true, 2383 "systeminfo": "https://bms.example.com/descriptions/lightbulb", 2384 "cache-validity": 48, 2385 "extensions": [ 2386 "ietf-mud-detext-example" 2387 ], 2388 "ietf-mud-detext-example:is-detnet-required": "false", 2389 "from-device-policy": { 2390 "access-lists": { 2391 "access-list": [ 2392 { 2393 "acl-name": "mud-54684-v6fr", 2394 "acl-type": "ietf-access-control-list:ipv6-acl" 2395 } 2396 ] 2397 } 2398 }, 2399 "to-device-policy": { 2400 "access-lists": { 2401 "access-list": [ 2402 { 2403 "acl-name": "mud-54684-v6to", 2404 "acl-type": "ietf-access-control-list:ipv6-acl" 2405 } 2406 ] 2407 } 2408 } 2409 }, 2410 "ietf-access-control-list:access-lists": { 2411 "acl": [ 2412 { 2413 "acl-name": "mud-54684-v6to", 2414 "acl-type": "ipv6-acl", 2415 "access-list-entries": { 2416 "ace": [ 2417 { 2418 "rule-name": "cl0-todev", 2419 "matches": { 2420 "ipv6-acl": { 2421 "ietf-acldns:src-dnsname": "service.bms.example.com", 2422 "protocol": 6, 2423 "source-port-range": { 2424 "lower-port": 443, 2425 "upper-port": 443 2426 } 2428 }, 2429 "tcp-acl": { 2430 "ietf-mud:direction-initiated": "from-device" 2431 } 2432 }, 2433 "actions": { 2434 "permit": [ 2435 null 2436 ] 2437 } 2438 } 2439 ] 2440 } 2441 }, 2442 { 2443 "acl-name": "mud-54684-v6fr", 2444 "acl-type": "ipv6-acl", 2445 "access-list-entries": { 2446 "ace": [ 2447 { 2448 "rule-name": "cl0-frdev", 2449 "matches": { 2450 "ipv6-acl": { 2451 "ietf-acldns:dst-dnsname": "service.bms.example.com", 2452 "protocol": 6, 2453 "destination-port-range": { 2454 "lower-port": 443, 2455 "upper-port": 443 2456 } 2457 }, 2458 "tcp-acl": { 2459 "ietf-mud:direction-initiated": "from-device" 2460 } 2461 }, 2462 "actions": { 2463 "permit": [ 2464 null 2465 ] 2466 } 2467 } 2468 ] 2469 } 2470 } 2471 ] 2472 } 2473 } 2475 Authors' Addresses 2477 Eliot Lear 2478 Cisco Systems 2479 Richtistrasse 7 2480 Wallisellen CH-8304 2481 Switzerland 2483 Phone: +41 44 878 9200 2484 Email: lear@cisco.com 2486 Ralph Droms 2488 Phone: +1 978 376 3731 2489 Email: rdroms@gmail.com 2491 Dan Romascanu 2493 Phone: +972 54 5555347 2494 Email: dromasca@gmail.com