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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reference: RFC 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) == Outdated reference: A later version (-20) exists of draft-ietf-netmod-rfc6087bis-14 -- Obsolete informational reference (is this intentional?): RFC 7042 (Obsoleted by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 (~~), 6 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: April 27, 2018 6 D. Romascanu 7 October 24, 2017 9 Manufacturer Usage Description Specification 10 draft-ietf-opsawg-mud-13 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 April 27, 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 . . . . . 9 66 1.8. Order of operations . . . . . . . . . . . . . . . . . . . 10 67 2. The MUD Model and Semantic Meaning . . . . . . . . . . . . . 11 68 2.1. The IETF-MUD YANG Module . . . . . . . . . . . . . . . . 11 69 3. Data Node Definitions . . . . . . . . . . . . . . . . . . . . 13 70 3.1. to-device-policy and from-device-policy containers . . . 13 71 3.2. last-update . . . . . . . . . . . . . . . . . . . . . . . 14 72 3.3. cache-validity . . . . . . . . . . . . . . . . . . . . . 14 73 3.4. is-supported . . . . . . . . . . . . . . . . . . . . . . 14 74 3.5. systeminfo . . . . . . . . . . . . . . . . . . . . . . . 14 75 3.6. extensions . . . . . . . . . . . . . . . . . . . . . . . 14 76 3.7. manufacturer . . . . . . . . . . . . . . . . . . . . . . 15 77 3.8. same-manufacturer . . . . . . . . . . . . . . . . . . . . 15 78 3.9. model . . . . . . . . . . . . . . . . . . . . . . . . . . 15 79 3.10. local-networks . . . . . . . . . . . . . . . . . . . . . 15 80 3.11. controller . . . . . . . . . . . . . . . . . . . . . . . 15 81 3.12. my-controller . . . . . . . . . . . . . . . . . . . . . . 16 82 3.13. direction-initiated . . . . . . . . . . . . . . . . . . . 16 83 4. Processing of the MUD file . . . . . . . . . . . . . . . . . 16 84 5. What does a MUD URL look like? . . . . . . . . . . . . . . . 17 85 6. The MUD YANG Model . . . . . . . . . . . . . . . . . . . . . 17 86 7. The Domain Name Extension to the ACL Model . . . . . . . . . 23 87 7.1. source-dnsname . . . . . . . . . . . . . . . . . . . . . 24 88 7.2. destination-dnsname . . . . . . . . . . . . . . . . . . . 24 89 7.3. The ietf-acldns Model . . . . . . . . . . . . . . . . . . 24 90 8. MUD File Example . . . . . . . . . . . . . . . . . . . . . . 25 91 9. The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . . 28 92 9.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 28 93 9.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 29 94 9.3. Relay Requirements . . . . . . . . . . . . . . . . . . . 29 95 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 29 96 11. The Manufacturer Usage Description LLDP extension . . . . . . 31 97 12. Creating and Processing of Signed MUD Files . . . . . . . . . 33 98 12.1. Creating a MUD file signature . . . . . . . . . . . . . 33 99 12.2. Verifying a MUD file signature . . . . . . . . . . . . . 33 100 13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 34 101 14. Deployment Considerations . . . . . . . . . . . . . . . . . . 34 102 15. Security Considerations . . . . . . . . . . . . . . . . . . . 35 103 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 104 16.1. YANG Module Registrations . . . . . . . . . . . . . . . 37 105 16.2. DHCPv4 and DHCPv6 Options . . . . . . . . . . . . . . . 38 106 16.3. PKIX Extensions . . . . . . . . . . . . . . . . . . . . 38 107 16.4. Well Known URI Suffix . . . . . . . . . . . . . . . . . 38 108 16.5. MIME Media-type Registration for MUD files . . . . . . . 38 109 16.6. LLDP IANA TLV Subtype Registry . . . . . . . . . . . . . 39 110 16.7. The MUD Well Known Universal Resource Name (URNs) . . . 40 111 16.8. Extensions Registry . . . . . . . . . . . . . . . . . . 40 112 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 40 113 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 41 114 18.1. Normative References . . . . . . . . . . . . . . . . . . 41 115 18.2. Informative References . . . . . . . . . . . . . . . . . 43 116 Appendix A. Changes from Earlier Versions . . . . . . . . . . . 44 117 Appendix B. Default MUD nodes . . . . . . . . . . . . . . . . . 47 118 Appendix C. A Sample Extension: DETNET-indicator . . . . . . . . 51 119 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 55 121 1. Introduction 123 The Internet has largely been constructed on general purpose 124 computers, those devices that may be used for a purpose that is 125 specified by those who buy the device. [RFC1984] presumed that an 126 end device would be most capable of protecting itself. This made 127 sense when the typical device was a workstation or a mainframe, and 128 it continues to make sense for general purpose computing devices 129 today, including laptops, smart phones, and tablets. 131 [RFC7452] discusses design patterns for, and poses questions about, 132 smart objects. Let us then posit a group of objects that are 133 specifically NOT general purpose computers. These devices have a 134 specific purpose. By definition, therefore, all other uses are NOT 135 intended. The combination of these two statements can be restated as 136 a manufacturer usage description (MUD) that can be applied at various 137 points within a network. Although this memo may seem to stress 138 access requirements, usage intent also consists of quality of service 139 needs a device may have. 141 We use the notion of "manufacturer" loosely in this context to refer 142 to the entity or organization that will state how a device is 143 intended to be used. In the context of a lightbulb, this might 144 indeed be the lightbulb manufacturer. In the context of a smarter 145 device that has a built in Linux stack, it might be an integrator of 146 that device. The key points are that the device itself is expected 147 to serve a limited purpose, and that there may exist an organization 148 in the supply chain of that device that will take responsibility for 149 informing the network about that purpose. 151 The intent of MUD is to solve for the following problems: 153 o Substantially reduce the threat surface on a device entering a 154 network to those communications intended by the manufacturer. 156 o Provide for a means to scale network policies to the ever- 157 increasing number types of devices in the network. 159 o Provide a means to address at least some vulnerabilities in a way 160 that is faster than it might take to update systems. This will be 161 particularly true for systems that are no longer supported by 162 their manufacturer. 164 o Keep the cost of implementation of such a system to the bare 165 minimum. 167 o Provide a means of extensibility for manufacturers to express 168 other device capabilities or requirements. 170 MUD consists of three architectural building blocks: 172 o A classifier that a device emits that can be used to locate a 173 description; 175 o The description itself, including how it is interpreted, and; 177 o A means for local network management systems to retrieve the 178 description. 180 In this specification we describe each of these building blocks and 181 how they are intended to be used together. However, they may also be 182 used separately, independent of this specification, by local 183 deployments for their own purposes. 185 1.1. What MUD doesn't do 187 MUD is not intended to address network authorization of general 188 purpose computers, as their manufacturers cannot envision a specific 189 communication pattern to describe. In addition, even those devices 190 that have a single or small number of uses might have very broad 191 communication patterns. MUD on its own is not for them either. 193 No matter how good a MUD-enabled network is, it will never replace 194 the need for manufacturers to patch vulnerabilities. It may, 195 however, provide network administrators with some additional 196 protection when those vulnerabilities exist. 198 Finally, no matter what the manufacturer specifies in a MUD file, 199 these are not directives, but suggestions. How they are instantiated 200 locally will depend on many factors and will be ultimately up to the 201 local network administrator, who must decide what is appropriate in a 202 given circumstances. 204 1.2. A Simple Example 206 A light bulb is intended to light a room. It may be remotely 207 controlled through the network, and it may make use of a rendezvous 208 service of some form that an app on smart phone accesses. What we 209 can say about that light bulb, then, is that all other network access 210 is unwanted. It will not contact a news service, nor speak to the 211 refrigerator, and it has no need of a printer or other devices. It 212 has no social networking friends. Therefore, an access list applied 213 to it that states that it will only connect to the single rendezvous 214 service will not impede the light bulb in performing its function, 215 while at the same time allowing the network to provide both it and 216 other devices an additional layer of protection. 218 1.3. Determining Intended Use 220 The notion of intended use is in itself not new. Network 221 administrators apply access lists every day to allow for only such 222 use. This notion of white listing was well described by Chapman and 223 Zwicky in [FW95]. Profiling systems that make use of heuristics to 224 identify types of systems have existed for years as well. 226 A Thing could just as easily tell the network what sort of access it 227 requires without going into what sort of system it is. This would, 228 in effect, be the converse of [RFC7488]. In seeking a general 229 purpose solution, however, we assume that a device has so few 230 capabilities that it will implement the least necessary capabilities 231 to function properly. This is a basic economic constraint. Unless 232 the network would refuse access to such a device, its developers 233 would have no reason to provide the network any information. To 234 date, such an assertion has held true. 236 1.4. Finding A Policy: The MUD URL 238 Our work begins with the device emitting a Universal Resource Locator 239 (URL) [RFC3986]. This URL serves both to classify the device type 240 and to provide a means to locate a policy file. 242 In this memo three means are defined to emit the MUD URL. One is a 243 DHCP option[RFC2131],[RFC3315] that the DHCP client uses to inform 244 the DHCP server. The DHCP server may take further actions, such as 245 retrieve the URL or otherwise pass it along to network management 246 system or controller. The second method defined is an X.509 247 constraint. The IEEE has developed [IEEE8021AR] that provides a 248 certificate-based approach to communicate device characteristics, 249 which itself relies on [RFC5280]. The MUD URL extension is non- 250 critical, as required by IEEE 802.1AR. Various means may be used to 251 communicate that certificate, including Tunnel Extensible 252 Authentication Protocol (TEAP) [RFC7170]. Finally, a Link Layer 253 Discovery Protocol (LLDP) frame is defined [IEEE8021AB]. 255 It is possible that there may be other means for a MUD URL to be 256 learned by a network. For instance, some devices may already be 257 fielded or have very limited ability to communicate a MUD URL, and 258 yet can be identified through some means, such as a serial number or 259 a public key. In these cases, manufacturers may be able to map those 260 identifiers to particular MUD URLs (or even the files themselves). 261 Similarly, there may be alternative resolution mechanisms available 262 for situations where Internet connectivity is limited or does not 263 exist. Such mechanisms are not described in this memo, but are 264 possible. Implementors should allow for this sort of flexibility of 265 how MUD URLs may be learned. 267 1.5. Types of Policies 269 When the MUD URL is resolved, the MUD controller retrieves a file 270 that describes what sort of communications a device is designed to 271 have. The manufacturer may specify either specific hosts for cloud 272 based services or certain classes for access within an operational 273 network. An example of a class might be "devices of a specified 274 manufacturer type", where the manufacturer type itself is indicated 275 simply by the authority component (e.g, the domain name) of the MUD 276 URL. Another example might be to allow or disallow local access. 277 Just like other policies, these may be combined. For example: 279 o Allow access to devices of the same manufacturer 281 o Allow access to and from controllers via Constrained Application 282 Protocol (COAP)[RFC7252] 284 o Allow access to local DNS/NTP 286 o Deny all other access 288 A printer might have a description that states: 290 o Allow access for port IPP or port LPD 292 o Allow local access for port HTTP 294 o Deny all other access 296 In this way anyone can print to the printer, but local access would 297 be required for the management interface. 299 The files that are retrieved are intended to be closely aligned to 300 existing network architectures so that they are easy to deploy. We 301 make use of YANG [RFC7950] because of the time and effort spent to 302 develop accurate and adequate models for use by network devices. 303 JSON is used as a serialization for compactness and readability, 304 relative to XML. Other formats may be chosen with later versions of 305 MUD. 307 While the policy examples given here focus on access control, this is 308 not intended to be the sole focus. By structuring the model 309 described in this document with clear extension points, other 310 descriptions could be included. One that often comes to mind is 311 quality of service. 313 The YANG modules specified here are extensions of 314 [I-D.ietf-netmod-acl-model]. The extensions to this model allow for 315 a manufacturer to express classes of systems that a manufacturer 316 would find necessary for the proper function of the device. Two 317 modules are specified. The first module specifies a means for domain 318 names to be used in ACLs so that devices that have their controllers 319 in the cloud may be appropriately authorized with domain names, where 320 the mapping of those names to addresses may rapidly change. 322 The other module abstracts away IP addresses into certain classes 323 that are instantiated into actual IP addresses through local 324 processing. Through these classes, manufacturers can specify how the 325 device is designed to communicate, so that network elements can be 326 configured by local systems that have local topological knowledge. 327 That is, the deployment populates the classes that the manufacturer 328 specifies. The abstractions below map to zero or more hosts, as 329 follows: 331 Manufacturer: A device made by a particular manufacturer, as 332 identified by the authority component of its MUD URL 334 same-manufacturer: Devices that have the same authority component of 335 their MUD URL. 337 Controller: Devices that the local network administrator admits to 338 the particular class. 340 my-controller: Devices associated with the MUD URL of a device that 341 the administrator admits. 343 local: The class of IP addresses that are scoped within some 344 administrative boundary. By default it is suggested that this be 345 the local subnet. 347 The "manufacturer" classes can be easily specified by the 348 manufacturer, whereas controller classes are initially envisioned to 349 be specified by the administrator. 351 Because manufacturers do not know who will be using their devices, it 352 is important for functionality referenced in usage descriptions to be 353 relatively ubiquitous and mature. For these reasons only a limited 354 subset YANG-based configuration of is permitted in a MUD file. 356 1.6. Terminology 358 MUD: manufacturer usage description. 360 MUD file: a file containing YANG-based JSON that describes a Thing 361 and associated suggested specific network behavior. 363 MUD file server: a web server that hosts a MUD file. 365 MUD controller: the system that requests and receives the MUD file 366 from the MUD server. After it has processed a MUD file, it may 367 direct changes to relevant network elements. 369 MUD URL: a URL that can be used by the MUD controller to receive the 370 MUD file. 372 Thing: the device emitting a MUD URL. 374 Manufacturer: the entity that configures the Thing to emit the MUD 375 URL and the one who asserts a recommendation in a MUD file. The 376 manufacturer might not always be the entity that constructs a 377 Thing. It could, for instance, be a systems integrator, or even a 378 component provider. 380 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 381 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 382 document are to be interpreted as described in [RFC2119]. 384 1.7. The Manufacturer Usage Description Architecture 386 With these components laid out we now have the basis for an 387 architecture. This leads us to ASCII art. 389 ....................................... 390 . ____________ . _____________ 391 . | | . | | 392 . | MUD |-->get URL-->| MUD | 393 . | Controller | .(https) | File Server | 394 . End system network |____________|<-MUD file<-<|_____________| 395 . . . 396 . . . 397 . _______ _________ . 398 .| | (dhcp et al) | router | . 399 .| Thing |---->MUD URL-->| or | . 400 .|_______| | switch | . 401 . |_________| . 402 ....................................... 404 Figure 1: MUD Architecture 406 In the above diagram, the switch or router collects MUD URLs and 407 forwards them to the network management system for processing. This 408 happens in different ways, depending on how the URL is communicated. 409 For instance, in the case of DHCP, the DHCP server might receive the 410 URL and then process it. In the case of IEEE 802.1X, the switch 411 would carry the URL via a certificate to the authentication server 412 via EAP over Radius[RFC3748], which would then process it. One 413 method to do this is TEAP, described in [RFC7170]. The certificate 414 extension is described below. 416 The information returned by the web site is valid for the duration of 417 the Thing's connection, or as specified in the description. Thus if 418 the Thing is disconnected, any associated configuration in the switch 419 can be removed. Similarly, from time to time the description may be 420 refreshed, based on new capabilities or communication patterns or 421 vulnerabilities. 423 The web site is typically run by or on behalf of the manufacturer. 424 Its domain name is that of the authority found in the MUD URL. For 425 legacy cases where Things cannot emit a URL, if the switch is able to 426 determine the appropriate URL, it may proxy it, the trivial cases 427 being a hardcoded MUD-URL on a switch port, or a mapping from some 428 available identifier such as an L2 address or certificate hash to a 429 MUD-URL. 431 The role of the MUD controller in this environment is to do the 432 following: 434 o receive MUD URLs, 436 o retrieve MUD files, 438 o translate abstractions in the MUD files to specific network 439 element configuration, 441 o maintain and update any required mappings of the abstractions, and 443 o update network elements with appropriate configuration. 445 A MUD controller may be a component of a AAA or network management 446 system. Communication within those systems and from those systems to 447 network elements is beyond the scope of this memo. 449 1.8. Order of operations 451 As mentioned above, MUD contains architectural building blocks, and 452 so order of operation may vary. However, here is one clear intended 453 example: 455 1. Thing emits URL. 457 2. That URL is forwarded to a MUD controller by the nearest switch 458 (how this happens depends on the way in which the MUD URL is 459 emitted). 461 3. The MUD controller retrieves the MUD file and signature from the 462 MUD file server, assuming it doesn't already have copies. After 463 validating the signature, it may test the URL against a web or 464 domain reputation service, and it may test any hosts within the 465 file against those reputation services, as it deems fit. 467 4. The MUD controller may query the administrator for permission to 468 add the Thing and associated policy. If the Thing is known or 469 the Thing type is known, it may skip this step. 471 5. The MUD controller instantiates local configuration based on the 472 abstractions defined in this document. 474 6. The MUD controller configures the switch nearest the Thing. 475 Other systems may be configured as well. 477 7. When the Thing disconnects, policy is removed. 479 2. The MUD Model and Semantic Meaning 481 A MUD file consists of a YANG model that has been serialized in JSON 482 [RFC7951]. For purposes of MUD, the nodes that can be modified are 483 access lists as augmented by this model. The MUD file is limited to 484 the serialization of only the following YANG schema: 486 o ietf-access-control-list [I-D.ietf-netmod-acl-model] 488 o ietf-mud (this document) 490 o ietf-acldns (this document) 492 Extensions may be used to add additional schema. This is described 493 further on. 495 To provide the widest possible deployment, publishers of MUD files 496 SHOULD make use of the abstractions in this memo and avoid the use of 497 IP addresses. A MUD controller SHOULD NOT automatically implement 498 any MUD file that contains IP addresses, especially those that might 499 have local significance. The addressing of one side of an access 500 list is implicit, based on whether it is applied as to-device-policy 501 or from-device-policy. 503 With the exceptions of "acl-name", "acl-type", "rule-name", and TCP 504 and UDP source and destination port information, publishers of MUD 505 files SHOULD limit the use of ACL model leaf nodes expressed to those 506 found in this specification. Absent any extensions, MUD files are 507 assumed to implement only the following ACL model features: 509 o any-acl, mud-acl, icmp-acl, ipv6-acl, tcp-acl, any-acl, udp-acl, 510 ipv4-acl, and ipv6-acl 512 Furthermore, only"accept" or "drop" actions SHOULD be included. A 513 MUD controller MAY choose to interpret "reject" as "drop". A MUD 514 controller SHOULD ignore all other actions. 516 In fact, MUD controllers MAY ignore any particular component of a 517 description or MAY ignore the description in its entirety, and SHOULD 518 carefully inspect all MUD descriptions. Publishers of MUD files MUST 519 NOT include other nodes except as described in Section 3.6. See that 520 section for more information. 522 2.1. The IETF-MUD YANG Module 524 This module is structured into three parts: 526 o The first container "mud" holds information that is relevant to 527 retrieval and validity of the MUD file itself, as well as policy 528 intended to and from the Thing. 530 o The second component augments the matching container of the ACL 531 model to add several nodes that are relevant to the MUD URL, or 532 otherwise abstracted for use within a local environment. 534 o The third component augments the tcp-acl container of the ACL 535 model to add the ability to match on the direction of initiation 536 of a TCP connection. 538 A valid MUD file will contain two root objects, a "mud" container and 539 an "access-lists" container. Extensions may add additional root 540 objects as required. As a reminder, when parsing access-lists, 541 elements within a "match" block are logically ANDed. In general, a 542 single abstraction in a match statement should be used. For 543 instance, it makes little sense to match both "my-controller" and 544 "controller" with an argument, since they are highly unlikely to be 545 the same value. 547 A simplified graphical representation of the data models is used in 548 this document. The meaning of the symbols in these diagrams is 549 explained in [I-D.ietf-netmod-rfc6087bis]. 551 module: ietf-mud 552 +--rw mud! 553 +--rw mud-url inet:uri 554 +--rw last-update yang:date-and-time 555 +--rw cache-validity? uint8 556 +--rw is-supported boolean 557 +--rw systeminfo? inet:uri 558 +--rw extensions* string 559 +--rw from-device-policy 560 | +--rw access-lists 561 | +--rw access-list* [acl-name acl-type] 562 | +--rw acl-name -> /acl:access-lists/acl/acl-name 563 | +--rw acl-type identityref 564 +--rw to-device-policy 565 +--rw access-lists 566 +--rw access-list* [acl-name acl-type] 567 +--rw acl-name -> /acl:access-lists/acl/acl-name 568 +--rw acl-type identityref 569 augment /acl:access-lists/acl:acl/acl:aces/ 570 acl:ace/acl:matches: 571 +--rw mud-acl 572 +--rw manufacturer? inet:host 573 +--rw same-manufacturer? empty 574 +--rw model? inet:uri 575 +--rw local-networks? empty 576 +--rw controller? inet:uri 577 +--rw my-controller? empty 578 augment /acl:access-lists/acl:acl/acl:aces/ 579 acl:ace/acl:matches/acl:tcp-acl: 580 +--rw direction-initiated? direction 582 3. Data Node Definitions 584 Note that in this section, when we use the term "match" we are 585 referring to the ACL model "matches" node, and thus returns positive 586 such that an action should be applied. 588 The following nodes are defined. 590 3.1. to-device-policy and from-device-policy containers 592 [I-D.ietf-netmod-acl-model] describes access-lists but does not 593 attempt to indicate where they are applied as that is handled 594 elsewhere in a configuration. However, in this case, a MUD file must 595 be explicit in describing the communication pattern of a Thing, and 596 that includes indicating what is to be permitted or denied in either 597 direction of communication. Hence each of these containers indicate 598 the appropriate direction of a flow in association with a particular 599 Thing. They contain references to specific access-lists. 601 3.2. last-update 603 This is a date-and-time value of when the MUD file was generated. 604 This is akin to a version number. Its form is taken from [RFC6991] 605 which, for those keeping score, in turn was taken from Section 5.6 of 606 [RFC3339], which was taken from [ISO.8601.1988]. 608 3.3. cache-validity 610 This uint8 is the period of time in hours that a network management 611 station MUST wait since its last retrieval before checking for an 612 update. It is RECOMMENDED that this value be no less than 24 and 613 MUST NOT be more than 168 for any Thing that is supported. This 614 period SHOULD be no shorter than any period determined through HTTP 615 caching directives (e.g., "cache-control" or "Expires"). N.B., 616 expiring of this timer does not require the MUD controller to discard 617 the MUD file, nor terminate access to a Thing. See Section 15 for 618 more information. 620 3.4. is-supported 622 This boolean is an indication from the manufacturer to the network 623 administrator as to whether or not the Thing is supported. In this 624 context a Thing is said to NOT be supported if the manufacturer 625 intends never to issue an update to the Thing or never update the MUD 626 file. A MUD controller MAY still periodically check for updates. 628 3.5. systeminfo 630 This is a URL that points to a description of the Thing to be 631 connected. The intent is for administrators to be able to see a 632 localized name associated with the Thing. The referenced URL SHOULD 633 be a localized display string, and MAY be in either HTML or a raw 634 UTF-8 text file. It SHOULD NOT exceed 60 characters worth of display 635 space (that is- what the administrator actually sees), but it MAY 636 contain links to other documents (presumably product documentation). 638 3.6. extensions 640 This optional leaf-list names MUD extensions that are used in the MUD 641 file. Note that NO MUD extensions may be used in a MUD file prior to 642 the extensions being declared. Implementations MUST ignore any node 643 in this file that they do not understand. 645 Note that extensions can either extend the MUD file as described in 646 the previous paragraph, or they might reference other work. An 647 extension example can be found in Appendix C. 649 3.7. manufacturer 651 This node consists of a hostname that would be matched against the 652 authority component of another Thing's MUD URL. In its simplest form 653 "manufacturer" and "same-manufacturer" may be implemented as access- 654 lists. In more complex forms, additional network capabilities may be 655 used. For example, if one saw the line "manufacturer" : 656 "flobbidy.example.com", then all Things that registered with a MUD 657 URL that contained flobbity.example.com in its authority section 658 would match. 660 3.8. same-manufacturer 662 This is an equivalent for when the manufacturer element is used to 663 indicate the authority that is found in another Thing's MUD URL 664 matches that of the authority found in this Thing's MUD URL. For 665 example, if the Thing's MUD URL were https://b1.example.com/.well- 666 known/mud/v1/ThingV1, then all devices that had MUD URL with an 667 authority section of b1.example.com would match. 669 3.9. model 671 This string matches the entire MUD URL, thus covering the model that 672 is unique within the context of the authority. It may contain not 673 only model information, but versioning information as well, and any 674 other information that the manufacturer wishes to add. The intended 675 use is for devices of this precise class to match, to permit or deny 676 communication between one another. 678 3.10. local-networks 680 This null-valued node expands to include local networks. Its default 681 expansion is that packets must not traverse toward a default route 682 that is received from the router. However, administrators may expand 683 the expression as is appropriate in their deployments. 685 3.11. controller 687 This URI specifies a value that a controller will register with the 688 mud controller. The node then is expanded to the set of hosts that 689 are so registered. This node may also be a URN. In this case, the 690 URN describes a well known service, such as DNS or NTP. 692 Great care should be used when invoking the controller class. For 693 one thing, it requires some understanding by the administrator as to 694 when it is appropriate. Classes that are standardized may make it 695 possible to easily name devices that support standard functions. For 696 instance, the MUD controller could have some knowledge of which DNS 697 servers should be used for any particular group of Things. Non- 698 standard classes will likely require some sort of administrator 699 interaction. Pre-registration in such classes by controllers with 700 the MUD server is encouraged. The mechanism to do that is beyond the 701 scope of this work. 703 Controller URIs MAY take the form of a URL (e.g. "http[s]://"). 704 However, MUD controllers MUST NOT resolve and retrieve such files, 705 and it is RECOMMENDED that there be no such file at this time, as 706 their form and function may be defined at a point in the future. For 707 now, URLs should serve simply as class names and be populated by the 708 local deployment administrator. 710 3.12. my-controller 712 This null-valued node signals to the MUD controller to use whatever 713 mapping it has for this MUD URL to a particular group of hosts. This 714 may require prompting the administrator for class members. Future 715 work should seek to automate membership management. 717 3.13. direction-initiated 719 When applied this matches packets when the flow was initiated in the 720 corresponding direction. [RFC6092] specifies IPv6 guidance best 721 practices. While that document is scoped specifically to IPv6, its 722 contents are applicable for IPv4 as well. When this flag is set, and 723 the system has no reason to believe a flow has been initiated it MUST 724 drop the packet. This node may be implemented in its simplest form 725 by looking at naked SYN bits, but may also be implemented through 726 more stateful mechanisms. 728 4. Processing of the MUD file 730 To keep things relatively simple in addition to whatever definitions 731 exist, we also apply two additional default behaviors: 733 o Anything not explicitly permitted is denied. 735 o Local DNS and NTP are, by default, permitted to and from the 736 Thing. 738 An explicit description of the defaults can be found in Appendix B. 740 5. What does a MUD URL look like? 742 To begin with, MUD takes full advantage of both the https: scheme and 743 the use of .well-known. HTTPS is important in this case because a 744 man in the middle attack could otherwise harm the operation of a 745 class of Things. .well-known is used because we wish to add 746 additional structure to the URL, and want to leave open for future 747 versions both the means by which the URL is processed and the format 748 of the MUD file retrieved (there have already been some discussions 749 along these lines). The URL appears as follows: 751 mud-url = "https://" authority "/.well-known/mud/" mud-rev 752 "/" modelinfo ( "?" extras ) 753 ; authority is from RFC3986 754 mud-rev = "v1" 755 modelinfo = segment ; from RFC3986 756 extras = query ; from RFC3986 758 mud-rev signifies the version of the manufacturer usage description 759 file. This memo specifies "v1" of that file. Later versions may 760 permit additional schemas or modify the format. In order to provide 761 for the broadest compatibility for the various transmission 762 mechanisms, the length of the URL for v1 MUST NOT exceed 255 octets. 764 Taken together with the mud-url, "modelinfo" represents a Thing model 765 as the manufacturer wishes to represent it. It could be a brand name 766 or something more specific. It also may provide a means to indicate 767 what version the product is. Specifically if it has been updated in 768 the field, this is the place where evidence of that update would 769 appear. The field should be changed when the intended communication 770 patterns of a Thing change. While from a controller standpoint, only 771 comparison and matching operations are safe, it is envisioned that 772 updates will require some administrative review. Processing of this 773 URL occurs as specified in [RFC2818] and [RFC3986]. 775 "extras" is intended for use by the MUD controller to provide 776 additional information such as posture about the Thing to the MUD 777 file server. This field MUST NOT be configured on the Thing itself 778 by a manufacturer - that is what "modelinfo" is for. It is left as 779 future work to define the full semantics of this field. 781 6. The MUD YANG Model 783 file "ietf-mud@2017-10-07.yang" 784 module ietf-mud { 785 yang-version 1.1; 786 namespace "urn:ietf:params:xml:ns:yang:ietf-mud"; 787 prefix ietf-mud; 789 import ietf-access-control-list { 790 prefix acl; 791 } 792 import ietf-yang-types { 793 prefix yang; 794 } 795 import ietf-inet-types { 796 prefix inet; 797 } 799 organization 800 "IETF OPSAWG (Ops Area) Working Group"; 801 contact 802 "WG Web: http://tools.ietf.org/wg/opsawg/ 803 WG List: opsawg@ietf.org 804 Author: Eliot Lear 805 lear@cisco.com 806 Author: Ralph Droms 807 rdroms@gmail.com 808 Author: Dan Romascanu 809 dromasca@gmail.com 811 "; 812 description 813 "This YANG module defines a component that augments the 814 IETF description of an access list. This specific module 815 focuses on additional filters that include local, model, 816 and same-manufacturer. 818 This module is intended to be serialized via JSON and stored 819 as a file, as described in RFC XXXX [RFC Editor to fill in with 820 this document #]. 822 Copyright (c) 2016,2017 IETF Trust and the persons 823 identified as the document authors. All rights reserved. 824 Redistribution and use in source and binary forms, with or 825 without modification, is permitted pursuant to, and subject 826 to the license terms contained in, the Simplified BSD 827 License set forth in Section 4.c of the IETF Trust's Legal 828 Provisions Relating to IETF Documents 829 (http://trustee.ietf.org/license-info). 830 This version of this YANG module is part of RFC XXXX; see 831 the RFC itself for full legal notices."; 833 revision 2017-10-07 { 834 description 835 "Initial proposed standard."; 836 reference 837 "RFC XXXX: Manufacturer Usage Description 838 Specification"; 839 } 841 typedef direction { 842 type enumeration { 843 enum "to-device" { 844 description 845 "packets or flows destined to the target 846 Thing"; 847 } 848 enum "from-device" { 849 description 850 "packets or flows destined from 851 the target Thing"; 852 } 853 } 854 description 855 "Which way are we talking about?"; 856 } 858 container mud { 859 presence "Enabled for this particular MUD URL"; 860 description 861 "MUD related information, as specified 862 by RFC-XXXX [RFC Editor to fill in]."; 863 uses mud-grouping; 864 } 866 grouping mud-grouping { 867 description 868 "Information about when support end(ed), and 869 when to refresh"; 870 leaf mud-url { 871 type inet:uri; 872 mandatory true; 873 description 874 "This is the MUD URL associated with the entry found 875 in a MUD file."; 876 } 877 leaf last-update { 878 type yang:date-and-time; 879 mandatory true; 880 description 881 "This is intended to be when the current MUD file 882 was generated. MUD Controllers SHOULD NOT check 883 for updates between this time plus cache validity"; 884 } 885 leaf cache-validity { 886 type uint8 { 887 range "1..168"; 888 } 889 units "hours"; 890 default "48"; 891 description 892 "The information retrieved from the MUD server is 893 valid for these many hours, after which it should 894 be refreshed. N.B. MUD controller implementations 895 need not discard MUD files beyond this period."; 896 } 897 leaf is-supported { 898 type boolean; 899 mandatory true; 900 description 901 "This boolean indicates whether or not the Thing is 902 currently supported by the manufacturer."; 903 } 904 leaf systeminfo { 905 type inet:uri; 906 description 907 "A URL to a description of this Thing. This 908 should be a brief localized description. The 909 reference text should be no more than octets. 910 systeminfo may be displayed to the user to 911 determine whether to allow the Thing on the 912 network."; 913 } 914 leaf-list extensions { 915 type string { 916 length "1..40"; 917 } 918 description 919 "A list of extension names that are used in this MUD 920 file. Each name is registered with the IANA and 921 described in an RFC."; 922 } 923 container from-device-policy { 924 description 925 "The policies that should be enforced on traffic 926 coming from the device. These policies are not 927 necessarily intended to be enforced at a single 928 point, but may be rendered by the controller to any 929 relevant enorcement points in the network or 930 elsewhere."; 932 uses access-lists; 933 } 934 container to-device-policy { 935 description 936 "The policies that should be enforced on traffic 937 going to the device. These policies are not 938 necessarily intended to be enforced at a single 939 point, but may be rendered by the controller to any 940 relevant enorcement points in the network or 941 elsewhere."; 942 uses access-lists; 943 } 944 } 946 grouping access-lists { 947 description 948 "A grouping for access lists in the context of device 949 policy."; 950 container access-lists { 951 description 952 "The access lists that should be applied to traffic 953 to or from the device."; 954 list access-list { 955 key "acl-name acl-type"; 956 description 957 "Each entry on this list refers to an ACL that 958 should be present in the overall access list 959 data model. Each ACL is identified by name and 960 type."; 961 leaf acl-name { 962 type leafref { 963 path "/acl:access-lists/acl:acl/acl:acl-name"; 964 } 965 description 966 "The name of the ACL for this entry."; 967 } 968 leaf acl-type { 969 type identityref { 970 base acl:acl-base; 971 } 972 description 973 "The type of the ACL for this entry. The name is 974 scoped ONLY to the MUD file, and may not be unique 975 in any other circumstance."; 976 } 977 } 978 } 979 } 980 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches" { 981 description 982 "adding abstractions to avoid need of IP addresses"; 983 container mud-acl { 984 description 985 "MUD-specific matches."; 986 leaf manufacturer { 987 type inet:host; 988 description 989 "A domain that is intended to match the authority 990 section of the MUD URL. This node is used to specify 991 one or more manufacturers a device should 992 be authorized to access."; 993 } 994 leaf same-manufacturer { 995 type empty; 996 description 997 "This node matches the authority section of the MUD URL 998 of a Thing. It is intended to grant access to all 999 devices with the same authority section."; 1000 } 1001 leaf model { 1002 type inet:uri; 1003 description 1004 "Devices of the specified model type will match if 1005 they have an identical MUD URL."; 1006 } 1007 leaf local-networks { 1008 type empty; 1009 description 1010 "IP addresses will match this node if they are 1011 considered local addresses. A local address may be 1012 a list of locally defined prefixes and masks 1013 that indicate a particular administrative scope."; 1014 } 1015 leaf controller { 1016 type inet:uri; 1017 description 1018 "This node names a class that has associated with it 1019 zero or more IP addresses to match against. These 1020 may be scoped to a manufacturer or via a standard 1021 URN."; 1022 } 1023 leaf my-controller { 1024 type empty; 1025 description 1026 "This node matches one or more network elements that 1027 have been configured to be the controller for this 1028 Thing, based on its MUD URL."; 1029 } 1030 } 1031 } 1032 augment "/acl:access-lists/acl:acl/acl:aces/" + 1033 "acl:ace/acl:matches/acl:tcp-acl" { 1034 description 1035 "Adding domain names to matching"; 1036 leaf direction-initiated { 1037 type direction; 1038 description 1039 "This node matches based on which direction a 1040 connection was initiated. The means by which that 1041 is determined is discussed in this document."; 1042 } 1043 } 1044 } 1046 1048 7. The Domain Name Extension to the ACL Model 1050 This module specifies an extension to IETF-ACL model such that domain 1051 names may be referenced by augmenting the "matches" node. Different 1052 implementations may deploy differing methods to maintain the mapping 1053 between IP address and domain name, if indeed any are needed. 1054 However, the intent is that resources that are referred to using a 1055 name should be authorized (or not) within an access list. 1057 The structure of the change is as follows: 1059 module: ietf-acldns 1060 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/ 1061 acl:matches/acl:ipv4-acl: 1062 +--rw src-dnsname? inet:host 1063 +--rw dst-dnsname? inet:host 1064 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/ 1065 acl:matches/acl:ipv6-acl: 1066 +--rw src-dnsname? inet:host 1067 +--rw dst-dnsname? inet:host 1069 The choice of these particular points in the access-list model is 1070 based on the assumption that we are in some way referring to IP- 1071 related resources, as that is what the DNS returns. A domain name in 1072 our context is defined in [RFC6991]. The augmentations are 1073 replicated across IPv4 and IPv6 to allow MUD file authors the ability 1074 to control the IP version that the Thing may utilize. 1076 The following node are defined. 1078 7.1. source-dnsname 1080 The argument corresponds to a domain name of a source as specified by 1081 inet:host. A number of means may be used to resolve hosts. What is 1082 important is that such resolutions be consistent with ACLs required 1083 by Things to properly operate. 1085 7.2. destination-dnsname 1087 The argument corresponds to a domain name of a destination as 1088 specified by inet:host See the previous section relating to 1089 resolution. 1091 7.3. The ietf-acldns Model 1093 file "ietf-acldns@2017-10-07.yang" 1094 module ietf-acldns { 1095 yang-version 1.1; 1096 namespace "urn:ietf:params:xml:ns:yang:ietf-acldns"; 1097 prefix "ietf-acldns"; 1099 import ietf-access-control-list { 1100 prefix "acl"; 1101 } 1103 import ietf-inet-types { 1104 prefix "inet"; 1105 } 1107 organization 1108 "IETF OPSAWG (Ops Area) Working Group"; 1110 contact 1111 "WG Web: http://tools.ietf.org/wg/opsawg/ 1112 WG List: opsawg@ietf.org 1113 Author: Eliot Lear 1114 lear@cisco.com 1115 Author: Ralph Droms 1116 rdroms@gmail.com 1117 Author: Dan Romascanu 1118 dromasca@gmail.com 1119 "; 1121 description 1122 "This YANG module defines a component that augments the 1123 IETF description of an access list to allow dns names 1124 as matching criteria."; 1126 revision "2017-10-07" { 1127 description "Base version of dnsname extension of ACL model"; 1128 reference "RFC XXXX: Manufacturer Usage Description 1129 Specification"; 1130 } 1132 grouping dns-matches { 1133 description "Domain names for matching."; 1135 leaf src-dnsname { 1136 type inet:host; 1137 description "domain name to be matched against"; 1138 } 1139 leaf dst-dnsname { 1140 type inet:host; 1141 description "domain name to be matched against"; 1142 } 1143 } 1145 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/" + 1146 "acl:matches/acl:ipv4-acl" { 1147 description "Adding domain names to matching"; 1148 uses dns-matches; 1149 } 1151 augment "/acl:access-lists/acl:acl/" + 1152 "acl:aces/acl:ace/" + 1153 "acl:matches/acl:ipv6-acl" { 1154 description "Adding domain names to matching"; 1155 uses dns-matches; 1156 } 1157 } 1158 1160 8. MUD File Example 1162 This example contains two access lists that are intended to provide 1163 outbound access to a cloud service on TCP port 443. 1165 { 1166 "ietf-mud:mud": { 1167 "mud-url": 1168 "https://bms.example.com/.well-known/mud/v1/lightbulb2000", 1169 "last-update": "2017-10-07T12:16:24+02:00", 1170 "cache-validity": 48, 1171 "is-supported": true, 1172 "systeminfo": 1173 "https://bms.example.com/descriptions/lightbulb2000", 1174 "from-device-policy": { 1175 "access-lists": { 1176 "access-list": [ 1177 { 1178 "acl-name": "mud-14377-v6fr", 1179 "acl-type": "ietf-access-control-list:ipv6-acl" 1180 } 1181 ] 1182 } 1183 }, 1184 "to-device-policy": { 1185 "access-lists": { 1186 "access-list": [ 1187 { 1188 "acl-name": "mud-14377-v6to", 1189 "acl-type": "ietf-access-control-list:ipv6-acl" 1190 } 1191 ] 1192 } 1193 } 1194 }, 1195 "ietf-access-control-list:access-lists": { 1196 "acl": [ 1197 { 1198 "acl-name": "mud-14377-v6to", 1199 "acl-type": "ipv6-acl", 1200 "access-list-entries": { 1201 "ace": [ 1202 { 1203 "rule-name": "cl0-todev", 1204 "matches": { 1205 "ipv6-acl": { 1206 "ietf-acldns:src-dnsname": 1207 "service.bms.example.com", 1208 "protocol": 6, 1209 "source-port-range": { 1210 "lower-port": 443, 1211 "upper-port": 443 1212 } 1213 }, 1214 "tcp-acl": { 1215 "ietf-mud:direction-initiated": "from-device" 1216 } 1217 }, 1218 "actions": { 1219 "forwarding": "accept" 1220 } 1221 } 1222 ] 1223 } 1224 }, 1225 { 1226 "acl-name": "mud-14377-v6fr", 1227 "acl-type": "ipv6-acl", 1228 "access-list-entries": { 1229 "ace": [ 1230 { 1231 "rule-name": "cl0-frdev", 1232 "matches": { 1233 "ipv6-acl": { 1234 "ietf-acldns:dst-dnsname": 1235 "service.bms.example.com", 1236 "protocol": 6, 1237 "destination-port-range": { 1238 "lower-port": 443, 1239 "upper-port": 443 1240 } 1241 }, 1242 "tcp-acl": { 1243 "ietf-mud:direction-initiated": "from-device" 1244 } 1245 }, 1246 "actions": { 1247 "forwarding": "accept" 1248 } 1249 } 1250 ] 1251 } 1252 } 1253 ] 1254 } 1255 } 1257 In this example, two policies are declared, one from the Thing and 1258 the other to the Thing. Each policy names an access list that 1259 applies to the Thing, and one that applies from. Within each access 1260 list, access is permitted to packets flowing to or from the Thing 1261 that can be mapped to the domain name of "service.bms.example.com". 1262 For each access list, the enforcement point should expect that the 1263 Thing initiated the connection. 1265 9. The MUD URL DHCP Option 1267 The IPv4 MUD URL client option has the following format: 1269 +------+-----+------------------------------ 1270 | code | len | MUD URL 1271 +------+-----+------------------------------ 1273 Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single 1274 octet that indicates the length of the URL in octets. MUD URL is a 1275 URL. MUD URLs MUST NOT exceed 255 octets. 1277 The IPv6 MUD URL client option has the following format: 1279 0 1 2 3 1280 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 1281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1282 | OPTION_MUD_URL_V6 | option-length | 1283 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1284 | MUD URL | 1285 | ... | 1286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1288 OPTION_MUD_URL_V6 (112; assigned by IANA). 1290 option-length contains the length of the URL in octets. 1292 The intent of this option is to provide both a new Thing classifier 1293 to the network as well as some recommended configuration to the 1294 routers that implement policy. However, it is entirely the purview 1295 of the network system as managed by the network administrator to 1296 decide what to do with this information. The key function of this 1297 option is simply to identify the type of Thing to the network in a 1298 structured way such that the policy can be easily found with existing 1299 toolsets. 1301 9.1. Client Behavior 1303 A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit 1304 DHCPv6 option. These options are singletons, as specified in 1305 [RFC7227]. Because clients are intended to have at most one MUD URL 1306 associated with them, they may emit at most one MUD URL option via 1307 DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4 1308 and v6 DHCP options are emitted, the same URL MUST be used. 1310 Clients SHOULD log or otherwise report improper acknowledgments from 1311 servers, but they MUST NOT modify their MUD URL configuration based 1312 on a server's response. The server's response is only an 1313 acknowledgment that the server has processed the option, and promises 1314 no specific network behavior to the client. In particular, it may 1315 not be possible for the server to retrieve the file associated with 1316 the MUD URL, or the local network administration may not wish to use 1317 the usage description. Neither of these situations should be 1318 considered in any way exceptional. 1320 9.2. Server Behavior 1322 A DHCP server may ignore these options or take action based on 1323 receipt of these options. If a server successfully parses the option 1324 and the URL, it MUST return the option with length field set to zero 1325 and a corresponding null URL field as an acknowledgment. Even in 1326 this circumstance, no specific network behavior is guaranteed. When 1327 a server consumes this option, it will either forward the URL and 1328 relevant client information (such as the gateway address or giaddr) 1329 to a network management system, or it will retrieve the usage 1330 description itself by resolving the URL. 1332 DHCP servers may implement MUD functionality themselves or they may 1333 pass along appropriate information to a network management system or 1334 MUD controller. A DHCP server that does process the MUD URL MUST 1335 adhere to the process specified in [RFC2818] and [RFC5280] to 1336 validate the TLS certificate of the web server hosting the MUD file. 1337 Those servers will retrieve the file, process it, create and install 1338 the necessary configuration on the relevant network element. Servers 1339 SHOULD monitor the gateway for state changes on a given interface. A 1340 DHCP server that does not provide MUD functionality and has forwarded 1341 a MUD URL to a MUD controller MUST notify the MUD controller of any 1342 corresponding change to the DHCP state of the client (such as 1343 expiration or explicit release of a network address lease). 1345 9.3. Relay Requirements 1347 There are no additional requirements for relays. 1349 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 1351 This section defines an X.509 non-critical certificate extension that 1352 contains a single Uniform Resource Locator (URL) that points to an 1353 on-line Manufacturer Usage Description concerning the certificate 1354 subject. URI must be represented as described in Section 7.4 of 1355 [RFC5280]. 1357 Any Internationalized Resource Identifiers (IRIs) MUST be mapped to 1358 URIs as specified in Section 3.1 of [RFC3987] before they are placed 1359 in the certificate extension. 1361 The semantics of the URL are defined Section 5 of this document. 1363 The choice of id-pe is based on guidance found in Section 4.2.2 of 1364 [RFC5280]: 1366 These extensions may be used to direct applications to on-line 1367 information about the issuer or the subject. 1369 The MUD URL is precisely that: online information about the 1370 particular subject. 1372 The new extension is identified as follows: 1374 1376 MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) 1377 internet(1) security(5) mechanisms(5) pkix(7) 1378 id-mod(0) id-mod-mudURLExtn2016(88) } 1380 DEFINITIONS IMPLICIT TAGS ::= BEGIN 1382 -- EXPORTS ALL -- 1384 IMPORTS 1385 EXTENSION 1386 FROM PKIX-CommonTypes-2009 1387 { iso(1) identified-organization(3) dod(6) internet(1) 1388 security(5) mechanisms(5) pkix(7) id-mod(0) 1389 id-mod-pkixCommon-02(57) } 1391 id-pe 1392 FROM PKIX1Explicit-2009 1393 { iso(1) identified-organization(3) dod(6) internet(1) 1394 security(5) mechanisms(5) pkix(7) id-mod(0) 1395 id-mod-pkix1-explicit-02(51) } ; 1396 MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... } 1397 ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax 1398 IDENTIFIED BY id-pe-mud-url } 1400 id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 } 1402 MUDURLSyntax ::= IA5String 1404 END 1406 1408 While this extension can appear in either an 802.AR manufacturer 1409 certificate (IDevID) or deployment certificate (LDevID), of course it 1410 is not guaranteed in either, nor is it guaranteed to be carried over. 1411 It is RECOMMENDED that MUD controller implementations maintain a 1412 table that maps a Thing to its MUD URL based on IDevIDs. 1414 11. The Manufacturer Usage Description LLDP extension 1416 The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop 1417 vendor-neutral link layer protocol used by end hosts network Things 1418 for advertising their identity, capabilities, and neighbors on an 1419 IEEE 802 local area network. Its Type-Length-Value (TLV) design 1420 allows for 'vendor-specific' extensions to be defined. IANA has a 1421 registered IEEE 802 organizationally unique identifier (OUI) defined 1422 as documented in [RFC7042]. The MUD LLDP extension uses a subtype 1423 defined in this document to carry the MUD URL. 1425 The LLDP vendor specific frame has the following format: 1427 +--------+--------+----------+---------+-------------- 1428 |TLV Type| len | OUI |subtype | MUD URL 1429 | =127 | |= 00 00 5E| = 1 | 1430 |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets) 1431 +--------+--------+----------+---------+-------------- 1433 where: 1435 o TLV Type = 127 indicates a vendor-specific TLV 1437 o len - indicates the TLV string length 1439 o OUI = 00 00 5E is the organizationally unique identifier of IANA 1441 o subtype = 1 (to be assigned by IANA for the MUD URL) 1443 o MUD URL - the length MUST NOT exceed 255 octets 1445 The intent of this extension is to provide both a new Thing 1446 classifier to the network as well as some recommended configuration 1447 to the routers that implement policy. However, it is entirely the 1448 purview of the network system as managed by the network administrator 1449 to decide what to do with this information. The key function of this 1450 extension is simply to identify the type of Thing to the network in a 1451 structured way such that the policy can be easily found with existing 1452 toolsets. 1454 Hosts, routers, or other network elements that implement this option 1455 are intended to have at most one MUD URL associated with them, so 1456 they may transmit at most one MUD URL value. 1458 Hosts, routers, or other network elements that implement this option 1459 may ignore these options or take action based on receipt of these 1460 options. For example they may fill in information in the respective 1461 extensions of the LLDP Management Information Base (LLDP MIB). LLDP 1462 operates in a one-way direction. LLDPDUs are not exchanged as 1463 information requests by one Thing and response sent by another Thing. 1464 The other Things do not acknowledge LLDP information received from a 1465 Thing. No specific network behavior is guaranteed. When a Thing 1466 consumes this extension, it may either forward the URL and relevant 1467 remote Thing information to a MUD controller, or it will retrieve the 1468 usage description by resolving the URL in accordance with normal HTTP 1469 semantics. 1471 12. Creating and Processing of Signed MUD Files 1473 Because MUD files contain information that may be used to configure 1474 network access lists, they are sensitive. To insure that they have 1475 not been tampered with, it is important that they be signed. We make 1476 use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for 1477 this purpose. 1479 12.1. Creating a MUD file signature 1481 A MUD file MUST be signed using CMS as an opaque binary object. In 1482 order to make successful verification more likely, intermediate 1483 certificates SHOULD be included. The signature is stored at the same 1484 location as the MUD URL but with the suffix of ".p7s". Signatures 1485 are transferred using content-type "application/pkcs7-signature". 1487 For example: 1489 % openssl cms -sign -signer mancertfile -inkey mankey \ 1490 -in mudfile -binary -outform DER - \ 1491 -certfile intermediatecert -out mudfile.p7s 1493 Note: A MUD file may need to be re-signed if the signature expires. 1495 12.2. Verifying a MUD file signature 1497 Prior to retrieving a MUD file the MUD controller SHOULD retrieve the 1498 MUD signature file using the MUD URL with a suffix of ".p7s". For 1499 example, if the MUD URL is "https://example.com/.well-known/v1/ 1500 modela", the MUD signature URL will be "https://example.com/.well- 1501 known/v1/modela.p7s". 1503 Upon retrieving a MUD file, a MUD controller MUST validate the 1504 signature of the file before continuing with further processing. A 1505 MUD controller MUST cease processing of that file it cannot validate 1506 the chain of trust to a known trust anchor until an administrator has 1507 given approval. 1509 The purpose of the signature on the file is to assign accountability 1510 to an entity, whose reputation can be used to guide administrators on 1511 whether or not to accept a given MUD file. It is already common 1512 place to check web reputation on the location of a server on which a 1513 file resides. While it is likely that the manufacturer will be the 1514 signer of the file, this is not strictly necessary, and may not be 1515 desirable. For one thing, in some environments, integrators may 1516 install their own certificates. For another, what is more important 1517 is the accountability of the recommendation, and not the 1518 cryptographic relationship between the device and the file. 1520 An example: 1522 % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile 1524 Note the additional step of verifying the common trust root. 1526 13. Extensibility 1528 One of our design goals is to see that MUD files are able to be 1529 understood by as broad a cross-section of systems as is possible. 1530 Coupled with the fact that we have also chosen to leverage existing 1531 mechanisms, we are left with no ability to negotiate extensions and a 1532 limited desire for those extensions in any event. A such, a two-tier 1533 extensibility framework is employed, as follows: 1535 1. At a coarse grain, a protocol version is included in a MUD URL. 1536 This memo specifies MUD version 1. Any and all changes are 1537 entertained when this version is bumped. Transition approaches 1538 between versions would be a matter for discussion in future 1539 versions. 1541 2. At a finer grain, only extensions that would not incur additional 1542 risk to the Thing are permitted. Specifically, adding nodes to 1543 the mud container is permitted with the understanding that such 1544 additions will be ignored by unaware implementations. Any such 1545 extensions SHALL be standardized through the IETF process, and 1546 MUST be named in the "extensions" list. MUD controllers MUST 1547 ignore YANG nodes they do not understand and SHOULD create an 1548 exception to be resolved by an administrator, so as to avoid any 1549 policy inconsistencies. 1551 14. Deployment Considerations 1553 Because MUD consists of a number of architectural building blocks, it 1554 is possible to assemble different deployment scenarios. One key 1555 aspect is where to place policy enforcement. In order to protect the 1556 Thing from other Things within a local deployment, policy can be 1557 enforced on the nearest switch or access point. In order to limit 1558 unwanted traffic within a network, it may also be advisable to 1559 enforce policy as close to the Internet as possible. In some 1560 circumstances, policy enforcement may not be available at the closest 1561 hop. At that point, the risk of so-called east-west infection is 1562 increased to the number of Things that are able to communicate 1563 without protection. 1565 A caution about some of the classes: admission of a Thing into the 1566 "manufacturer" and "same-manufacturer" class may have impact on 1567 access of other Things. Put another way, the admission may grow the 1568 access-list on switches connected to other Things, depending on how 1569 access is managed. Some care should be given on managing that 1570 access-list growth. Alternative methods such as additional network 1571 segmentation can be used to keep that growth within reason. 1573 Because as of this writing MUD is a new concept, one can expect a 1574 great many devices to not have implemented it. It remains a local 1575 deployment decision as to whether a device that is first connected 1576 should be alloewed broad or limited access. Furthermore, as 1577 mentioned in the introduction, a deployment may choose to ignore a 1578 MUD policy in its entirety, but simply taken into account the MUD URL 1579 as a classifier to be used as part of a local policy decision. 1581 15. Security Considerations 1583 Based on how a MUD URL is emitted, a Thing may be able to lie about 1584 what it is, thus gaining additional network access. There are 1585 several means to limit risk in this case. The most obvious is to 1586 only believe Things that make use of certificate-based authentication 1587 such as IEEE 802.1AR certificates. When those certificates are not 1588 present, Things claiming to be of a certain manufacturer SHOULD NOT 1589 be included in that manufacturer grouping without additional 1590 validation of some form. This will occur when it makes use of 1591 primitives such as "manufacturer" for the purpose of accessing Things 1592 of a particular type. Similarly, network management systems may be 1593 able to fingerprint the Thing. In such cases, the MUD URL can act as 1594 a classifier that can be proven or disproven. Fingerprinting may 1595 have other advantages as well: when 802.1AR certificates are used, 1596 because they themselves cannot change, fingerprinting offers the 1597 opportunity to add artificats to the MUD URL. The meaning of such 1598 artifacts is left as future work. 1600 Network management systems SHOULD NOT accept a usage description for 1601 a Thing with the same MAC address that has indicated a change of 1602 authority without some additional validation (such as review by a 1603 network administrator). New Things that present some form of 1604 unauthenticated MUD URL SHOULD be validated by some external means 1605 when they would be otherwise be given increased network access. 1607 It may be possible for a rogue manufacturer to inappropriately 1608 exercise the MUD file parser, in order to exploit a vulnerability. 1609 There are three recommended approaches to address this threat. The 1610 first is to validate the signature of the MUD file. The second is to 1611 have a system do a primary scan of the file to ensure that it is both 1612 parseable and believable at some level. MUD files will likely be 1613 relatively small, to start with. The number of ACEs used by any 1614 given Thing should be relatively small as well. It may also be 1615 useful to limit retrieval of MUD URLs to only those sites that are 1616 known to have decent web or domain reputations. 1618 Use of a URL necessitates the use of domain names. If a domain name 1619 changes ownership, the new owner of that domain may be able to 1620 provide MUD files that MUD controllers would consider valid. There 1621 are a few approaches that can mitigate this attack. First, MUD 1622 controllers SHOULD cache certificates used by the MUD file server. 1623 When a new certificate is retrieved for whatever reason, the MUD 1624 controller should check to see if ownership of the domain has 1625 changed. A fair programmatic approximation of this is when the name 1626 servers for the domain have changed. If the actual MUD file has 1627 changed, the controller MAY check the WHOIS database to see if 1628 registration ownership of a domain has changed. If a change has 1629 occured, or if for some reason it is not possible to determine 1630 whether ownership has changed, further review may be warranted. 1631 Note, this remediation does not take into account the case of a Thing 1632 that was produced long ago and only recently fielded, or the case 1633 where a new MUD controller has been installed. 1635 It may not be possible for a MUD controller to retrieve a MUD file at 1636 any given time. Should a MUD controller fail to retrieve a MUD file, 1637 it SHOULD consider the existing one safe to use, at least for a time. 1638 After some period, it SHOULD log that it has been unable to retrieve 1639 the file. There may be very good reasons for such failures, 1640 including the possibility that the MUD controller is in an off-line 1641 environment, the local Internet connection has failed, or the remote 1642 Internet connection has failed. It is also possible that an attacker 1643 is attempting to prevent onboarding of a device. It is a local 1644 deployment decision as to whether or not devices may be onboarded in 1645 the face of such failures. 1647 The release of a MUD URL by a Thing reveals what the Thing is, and 1648 provides an attacker with guidance on what vulnerabilities may be 1649 present. 1651 While the MUD URL itself is not intended to be unique to a specific 1652 Thing, the release of the URL may aid an observer in identifying 1653 individuals when combined with other information. This is a privacy 1654 consideration. 1656 In addressing both of these concerns, implementors should take into 1657 account what other information they are advertising through 1658 mechanisms such as mDNS[RFC6872], how a Thing might otherwise be 1659 identified, perhaps through how it behaves when it is connected to 1660 the network, whether a Thing is intended to be used by individuals or 1661 carry personal identifying information, and then apply appropriate 1662 data minimization techniques. One approach is to make use of TEAP 1663 [RFC7170] as the means to share information with authorized 1664 components in the network. Network elements may also assist in 1665 limiting access to the MUD URL through the use of mechanisms such as 1666 DHCPv6-Shield [RFC7610]. 1668 Please note that the security considerations mentioned in Section 4.7 1669 of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case 1670 because the YANG serialization is not intended to be accessed via 1671 NETCONF. However, for those who try to instantiate this model in a 1672 network element via NETCONF, all objects in each model in this draft 1673 exhibit similar security characteristics as 1674 [I-D.ietf-netmod-acl-model]. The basic purpose of MUD is to 1675 configure access, and so by its very nature can be disruptive if used 1676 by unauthorized parties. 1678 16. IANA Considerations 1680 16.1. YANG Module Registrations 1682 The following YANG modules are requested to be registred in the "IANA 1683 Module Names" registry: 1685 The ietf-mud module: 1687 o Name: ietf-mud 1689 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud 1691 o Prefix: ief-mud 1693 o Reference: This memo 1695 The ietf-acldns module: 1697 o Name: ietf-acldns 1699 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns 1701 o Prefix: ietf-acldns 1703 o Reference: This memo 1705 16.2. DHCPv4 and DHCPv6 Options 1707 The IANA has allocated option 161 in the Dynamic Host Configuration 1708 Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry 1709 for the MUD DHCPv4 option. 1711 IANA is requested to allocated the DHCPv4 and v6 options as specified 1712 in Section 9. 1714 16.3. PKIX Extensions 1716 IANA is kindly requested to make the following assignments for: 1718 o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for 1719 PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). 1721 o id-pe-mud-url object identifier from the "SMI Security for PKIX 1722 Certificate Extension" registry (1.3.6.1.5.5.7.1). 1724 The use of these values is specified in Section 10. 1726 16.4. Well Known URI Suffix 1728 The IANA has allocated the URL suffix of "mud" as follows: 1730 o URI Suffix: "mud" o Specification documents: this document o 1731 Related information: n/a 1733 16.5. MIME Media-type Registration for MUD files 1735 The following media-type is defined for transfer of MUD file: 1737 o Type name: application 1738 o Subtype name: mud+json 1739 o Required parameters: n/a 1740 o Optional parameters: n/a 1741 o Encoding considerations: 8bit; application/mud+json values 1742 are represented as a JSON object; UTF-8 encoding SHOULD be 1743 employed. 1744 o Security considerations: See Security Considerations 1745 of this document. 1746 o Interoperability considerations: n/a 1747 o Published specification: this document 1748 o Applications that use this media type: MUD controllers as 1749 specified by this document. 1750 o Fragment identifier considerations: n/a 1751 o Additional information: 1753 Magic number(s): n/a 1754 File extension(s): n/a 1755 Macintosh file type code(s): n/a 1757 o Person & email address to contact for further information: 1758 Eliot Lear , Ralph Droms 1759 o Intended usage: COMMON 1760 o Restrictions on usage: none 1761 o Author: 1762 Eliot Lear 1763 Ralph Droms 1764 o Change controller: IESG 1765 o Provisional registration? (standards tree only): No. 1767 16.6. LLDP IANA TLV Subtype Registry 1769 IANA is requested to create a new registry for IANA Link Layer 1770 Discovery Protocol (LLDP) TLV subtype values. The recommended policy 1771 for this registry is Expert Review. The maximum number of entries in 1772 the registry is 256. 1774 IANA is required to populate the initial registry with the value: 1776 LLDP subtype value = 1 (All the other 255 values should be initially 1777 marked as 'Unassigned'.) 1779 Description = the Manufacturer Usage Description (MUD) Uniform 1780 Resource Locator (URL) 1782 Reference = < this document > 1784 16.7. The MUD Well Known Universal Resource Name (URNs) 1786 The following parameter registry is requested to be added in 1787 accordance with [RFC3553] 1789 Registry name: "urn:ietf:params:mud" is requested. 1790 Specification: this document 1791 Repository: this document 1792 Index value: Encoded identically to a TCP/UDP port service 1793 name, as specified in Section 5.1 of [RFC6335] 1795 The following entries should be added to the "urn:ietf:params:mud" 1796 name space: 1798 "urn:ietf:params:mud:dns" refers to the service specified by 1799 [RFC1123]. "urn:ietf:params:mud:ntp" refers to the service specified 1800 by [RFC5905]. 1802 16.8. Extensions Registry 1804 The IANA is requested to establish a registry of extensions as 1805 follows: 1807 Registry name: MUD extensions registry 1808 Registry policy: Standards action 1809 Standard reference: document 1810 Extension name: UTF-8 encoded string, not to exceed 40 characters. 1812 Each extension MUST follow the rules specified in this specification. 1813 As is usual, the IANA issues early allocations based in accordance 1814 with [RFC7120]. 1816 17. Acknowledgments 1818 The authors would like to thank Einar Nilsen-Nygaard, who 1819 singlehandedly updated the model to match the updated ACL model, 1820 Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm, 1821 John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk 1822 Birkholz, Adam Montville, and Robert Sparks for their valuable advice 1823 and reviews. Russ Housley entirely rewrote Section 10 to be a 1824 complete module. Adrian Farrel provided the basis for privacy 1825 considerations text. Kent Watsen provided a thorough review of the 1826 architecture and the YANG model. The remaining errors in this work 1827 are entirely the responsibility of the authors. 1829 18. References 1831 18.1. Normative References 1833 [I-D.ietf-netmod-acl-model] 1834 Jethanandani, M., Huang, L., Agarwal, S., and D. Blair, 1835 "Network Access Control List (ACL) YANG Data Model", 1836 draft-ietf-netmod-acl-model-14 (work in progress), October 1837 2017. 1839 [IEEE8021AB] 1840 Institute for Electrical and Electronics Engineers, "IEEE 1841 Standard for Local and Metropolitan Area Networks-- 1842 Station and Media Access Control Connectivity Discovery", 1843 n.d.. 1845 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1846 Application and Support", STD 3, RFC 1123, 1847 DOI 10.17487/RFC1123, October 1989, . 1850 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1851 Requirement Levels", BCP 14, RFC 2119, 1852 DOI 10.17487/RFC2119, March 1997, . 1855 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1856 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1857 . 1859 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1860 DOI 10.17487/RFC2818, May 2000, . 1863 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1864 C., and M. Carney, "Dynamic Host Configuration Protocol 1865 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1866 2003, . 1868 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1869 Levkowetz, Ed., "Extensible Authentication Protocol 1870 (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, 1871 . 1873 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1874 Resource Identifier (URI): Generic Syntax", STD 66, 1875 RFC 3986, DOI 10.17487/RFC3986, January 2005, 1876 . 1878 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1879 Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, 1880 January 2005, . 1882 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1883 Housley, R., and W. Polk, "Internet X.509 Public Key 1884 Infrastructure Certificate and Certificate Revocation List 1885 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1886 . 1888 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, 1889 RFC 5652, DOI 10.17487/RFC5652, September 2009, 1890 . 1892 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1893 "Network Time Protocol Version 4: Protocol and Algorithms 1894 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1895 . 1897 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1898 Cheshire, "Internet Assigned Numbers Authority (IANA) 1899 Procedures for the Management of the Service Name and 1900 Transport Protocol Port Number Registry", BCP 165, 1901 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1902 . 1904 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 1905 RFC 6991, DOI 10.17487/RFC6991, July 2013, 1906 . 1908 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 1909 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 1910 2014, . 1912 [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 1913 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 1914 BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, 1915 . 1917 [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield: 1918 Protecting against Rogue DHCPv6 Servers", BCP 199, 1919 RFC 7610, DOI 10.17487/RFC7610, August 2015, 1920 . 1922 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 1923 RFC 7950, DOI 10.17487/RFC7950, August 2016, 1924 . 1926 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 1927 RFC 7951, DOI 10.17487/RFC7951, August 2016, 1928 . 1930 18.2. Informative References 1932 [FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls", 1933 January 1995. 1935 [I-D.ietf-netmod-rfc6087bis] 1936 Bierman, A., "Guidelines for Authors and Reviewers of YANG 1937 Data Model Documents", draft-ietf-netmod-rfc6087bis-14 1938 (work in progress), September 2017. 1940 [IEEE8021AR] 1941 Institute for Electrical and Electronics Engineers, 1942 "Secure Device Identity", 1998. 1944 [ISO.8601.1988] 1945 International Organization for Standardization, "Data 1946 elements and interchange formats - Information interchange 1947 - Representation of dates and times", ISO Standard 8601, 1948 June 1988. 1950 [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic 1951 Technology and the Internet", BCP 200, RFC 1984, 1952 DOI 10.17487/RFC1984, August 1996, . 1955 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 1956 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 1957 . 1959 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 1960 IETF URN Sub-namespace for Registered Protocol 1961 Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June 1962 2003, . 1964 [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security 1965 Capabilities in Customer Premises Equipment (CPE) for 1966 Providing Residential IPv6 Internet Service", RFC 6092, 1967 DOI 10.17487/RFC6092, January 2011, . 1970 [RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur, 1971 H., and O. Festor, "The Common Log Format (CLF) for the 1972 Session Initiation Protocol (SIP): Framework and 1973 Information Model", RFC 6872, DOI 10.17487/RFC6872, 1974 February 2013, . 1976 [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and 1977 IETF Protocol and Documentation Usage for IEEE 802 1978 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, 1979 October 2013, . 1981 [RFC7170] Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, 1982 "Tunnel Extensible Authentication Protocol (TEAP) Version 1983 1", RFC 7170, DOI 10.17487/RFC7170, May 2014, 1984 . 1986 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 1987 Application Protocol (CoAP)", RFC 7252, 1988 DOI 10.17487/RFC7252, June 2014, . 1991 [RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson, 1992 "Architectural Considerations in Smart Object Networking", 1993 RFC 7452, DOI 10.17487/RFC7452, March 2015, 1994 . 1996 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 1997 Reddy, "Port Control Protocol (PCP) Server Selection", 1998 RFC 7488, DOI 10.17487/RFC7488, March 2015, 1999 . 2001 Appendix A. Changes from Earlier Versions 2003 RFC Editor to remove this section prior to publication. 2005 Draft -10 to -12: 2007 These are based on WGLC comments: 2009 o Correct examples based on ACL model changes. 2011 o Change ordering nodes. 2013 o Additional explanatory text around systeminfo. 2015 o Change ordering in examples. 2017 o Make it VERY VERY VERY VERY clear that these are recommendations, 2018 not mandates. 2020 o DHCP -> NTP in some of the intro text. 2022 o Remove masa-server 2024 o "Things" to "network elements" in a few key places. 2026 o Reference to JSON YANG RFC added. 2028 Draft -10 to -11: 2030 o Example corrections 2032 o Typo 2034 o Fix two lists. 2036 o Addition of 'any-acl' and 'mud-acl' in the list of allowed 2037 features. 2039 o Clarification of what should be in a MUD file. 2041 Draft -09 to -10: 2043 o AD input. 2045 o Correct dates. 2047 o Add compliance sentence as to which ACL module features are 2048 implemented. 2050 Draft -08 to -09: 2052 o Resolution of Security Area review, IoT directorate review, GenART 2053 review, YANG doctors review. 2055 o change of YANG structure to address mandatory nodes. 2057 o Terminology cleanup. 2059 o specify out extra portion of MUD-URL. 2061 o consistency changes. 2063 o improved YANG descriptions. 2065 o Remove extra revisions. 2067 o Track ACL model changes. 2069 o Additional cautions on use of ACL model; further clarifications on 2070 extensions. 2072 Draft -07 to -08: 2074 o a number of editorials corrected. 2076 o definition of MUD file tweaked. 2078 Draft -06 to -07: 2080 o Examples updated. 2082 o Additional clarification for direction-initiated. 2084 o Additional implementation guidance given. 2086 Draft -06 to -07: 2088 o Update models to match new ACL model 2090 o extract directionality from the ACL, introducing a new device 2091 container. 2093 Draft -05 to -06: 2095 o Make clear that this is a component architecture (Polk and Watson) 2097 o Add order of operations (Watson) 2099 o Add extensions leaf-list (Pritikin) 2101 o Remove previous-mud-file (Watson) 2103 o Modify text in last-update (Watson) 2105 o Clarify local networks (Weis, Watson) 2107 o Fix contact info (Watson) 2109 o Terminology clarification (Weis) 2111 o Advice on how to handle LDevIDs (Watson) 2112 o Add deployment considerations (Watson) 2114 o Add some additional text about fingerprinting (Watson) 2116 o Appropriate references to 6087bis (Watson) 2118 o Change systeminfo to a URL to be referenced (Lear) 2120 Draft -04 to -05: * syntax error correction 2122 Draft -03 to -04: * Re-add my-controller 2124 Draft -02 to -03: * Additional IANA updates * Format correction in 2125 YANG. * Add reference to TEAP. 2127 Draft -01 to -02: * Update IANA considerations * Accept Russ Housley 2128 rewrite of X.509 text * Include privacy considerations text * Redo 2129 the URL limit. Still 255 bytes, but now stated in the URL 2130 definition. * Change URI registration to be under urn:ietf:params 2132 Draft -00 to -01: * Fix cert trust text. * change supportInformation 2133 to meta-info * Add an informational element in. * add urn registry 2134 and create first entry * add default elements 2136 Appendix B. Default MUD nodes 2138 What follows is the portion of a MUD file that permits DNS traffic to 2139 a controller that is registered with the URN 2140 "urn:ietf:params:mud:dns" and traffic NTP to a controller that is 2141 registered "urn:ietf:params:mud:ntp". This is considered the default 2142 behavior and the ACEs are in effect appended to whatever other "ace" 2143 entries that a MUD file contains. To block DNS or NTP one repeats 2144 the matching statement but replaces the "forwarding" action "accept" 2145 with "drop". Because ACEs are processed in the order they are 2146 received, the defaults would not be reached. A MUD controller might 2147 further decide to optimize to simply not include the defaults when 2148 they are overriden. 2150 Four of "acl" liste entries that implement default MUD nodes is 2151 listed below. Two are for IPv4 and two are for IPv6 (one in each 2152 direction for both versions of IP). 2154 "ietf-access-control-list:access-lists": { 2155 "acl": [ 2156 { 2157 "acl-name": "mud-v4-default-to-device", 2158 "acl-type": "ipv4-acl", 2159 "aces": { 2160 "ace": [ 2161 { 2162 "rule-name": "ent0-todev", 2163 "matches": { 2164 "ietf-mud:mud-acl": { 2165 "controller": "urn:ietf:params:mud:dns" 2166 }, 2167 "ipv4-acl": { 2168 "protocol": 17, 2169 "source-port-range": { 2170 "lower-port": 53, 2171 "upper-port": 53 2172 } 2173 } 2174 }, 2175 "actions": { 2176 "forwarding": "accept" 2177 } 2178 }, 2179 { 2180 "rule-name": "ent1-todev", 2181 "matches": { 2182 "ietf-mud:mud-acl": { 2183 "controller": "urn:ietf:params:mud:ntp" 2184 }, 2185 "ipv4-acl": { 2186 "protocol": 17, 2187 "source-port-range": { 2188 "lower-port": 123, 2189 "upper-port": 123 2190 } 2191 } 2192 }, 2193 "actions": { 2194 "forwarding": "accept" 2195 } 2196 } 2197 ] 2198 } 2199 }, 2200 { 2201 "acl-name": "mud-v4-default-from-device", 2202 "acl-type": "ipv4-acl", 2203 "aces": { 2204 "ace": [ 2205 { 2206 "rule-name": "ent0-frdev", 2207 "matches": { 2208 "ietf-mud:mud-acl": { 2209 "controller": "urn:ietf:params:mud:dns" 2210 }, 2211 "ipv4-acl": { 2212 "protocol": 17, 2213 "destination-port-range": { 2214 "lower-port": 53, 2215 "upper-port": 53 2216 } 2217 } 2218 }, 2219 "actions": { 2220 "forwarding": "accept" 2221 } 2222 }, 2223 { 2224 "rule-name": "ent1-frdev", 2225 "matches": { 2226 "ietf-mud:mud-acl": { 2227 "controller": "urn:ietf:params:mud:ntp" 2228 }, 2229 "ipv4-acl": { 2230 "protocol": 17, 2231 "destination-port-range": { 2232 "lower-port": 123, 2233 "upper-port": 123 2234 } 2235 } 2236 }, 2237 "actions": { 2238 "forwarding": "accept" 2239 } 2240 } 2241 ] 2242 } 2243 }, 2244 { 2245 "acl-name": "mud-v6-default-to-device", 2246 "acl-type": "ipv6-acl", 2247 "access-list-entries": { 2248 "ace": [ 2249 { 2250 "rule-name": "ent0-todev", 2251 "matches": { 2252 "ietf-mud:mud-acl": { 2253 "controller": "urn:ietf:params:mud:dns" 2254 }, 2255 "ipv6-acl": { 2256 "protocol": 17, 2257 "source-port-range": { 2258 "lower-port": 53, 2259 "upper-port": 53 2260 } 2261 } 2262 }, 2263 "actions": { 2264 "forwarding": "accept" 2265 } 2266 }, 2267 { 2268 "rule-name": "ent1-todev", 2269 "matches": { 2270 "ietf-mud:mud-acl": { 2271 "controller": "urn:ietf:params:mud:ntp" 2272 }, 2273 "ipv6-acl": { 2274 "protocol": 17, 2275 "source-port-range": { 2276 "lower-port": 123, 2277 "upper-port": 123 2278 } 2279 } 2280 }, 2281 "actions": { 2282 "forwarding": "accept" 2283 } 2284 } 2285 ] 2286 } 2287 }, 2288 { 2289 "acl-name": "mud-v6-default-from-device", 2290 "acl-type": "ipv6-acl", 2291 "access-list-entries": { 2292 "ace": [ 2293 { 2294 "rule-name": "ent0-frdev", 2295 "matches": { 2296 "ietf-mud:mud-acl": { 2297 "controller": "urn:ietf:params:mud:dns" 2298 }, 2299 "ipv6-acl": { 2300 "protocol": 17, 2301 "destination-port-range": { 2302 "lower-port": 53, 2303 "upper-port": 53 2305 } 2306 } 2307 }, 2308 "actions": { 2309 "forwarding": "accept" 2310 } 2311 }, 2312 { 2313 "rule-name": "ent1-frdev", 2314 "matches": { 2315 "ietf-mud:mud-acl": { 2316 "controller": "urn:ietf:params:mud:ntp" 2317 }, 2318 "ipv6-acl": { 2319 "protocol": 17, 2320 "destination-port-range": { 2321 "lower-port": 123, 2322 "upper-port": 123 2323 } 2324 } 2325 }, 2326 "actions": { 2327 "forwarding": "accept" 2328 } 2329 } 2330 ] 2331 } 2332 } 2333 ] 2334 } 2336 Appendix C. A Sample Extension: DETNET-indicator 2338 In this sample extension we augment the core MUD model to indicate 2339 whether the device implements DETNET. If a device later attempts to 2340 make use of DETNET, an notification or exception might be generated. 2341 Note that this example is intended only for illustrative purposes. 2343 Extension Name: "Example-Extension" (to be used in the extensions list) 2344 Standard: this document (but do not register the example) 2346 This extension augments the MUD model to include a single node, using 2347 the following sample module that has the following tree structure: 2349 module: ietf-mud-detext-example 2350 augment /ietf-mud:mud: 2351 +--rw is-detnet-required? boolean 2353 The model is defined as follows: 2355 file "ietf-mud-detext-example@2016-09-07.yang" 2356 module ietf-mud-detext-example { 2357 yang-version 1.1; 2358 namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example"; 2359 prefix ietf-mud-detext-example; 2361 import ietf-mud { 2362 prefix ietf-mud; 2363 } 2365 organization 2366 "IETF OPSAWG (Ops Area) Working Group"; 2367 contact 2368 "WG Web: http://tools.ietf.org/wg/opsawg/ 2369 WG List: opsawg@ietf.org 2370 Author: Eliot Lear 2371 lear@cisco.com 2372 Author: Ralph Droms 2373 rdroms@gmail.com 2374 Author: Dan Romascanu 2375 dromasca@gmail.com 2377 "; 2378 description 2379 "Sample extension to a MUD module to indicate a need 2380 for DETNET support."; 2382 revision 2017-09-05 { 2383 description 2384 "Initial revision."; 2385 reference 2386 "RFC XXXX: Manufacturer Usage Description 2387 Specification"; 2388 } 2390 augment "/ietf-mud:mud" { 2391 description 2392 "This adds a simple extension for a manufacturer 2393 to indicate whether DETNET is required by a 2394 device."; 2395 leaf is-detnet-required { 2396 type boolean; 2397 description 2398 "This value will equal true if a device requires 2399 detnet to properly function"; 2400 } 2401 } 2402 } 2403 2405 Using the previous example, we now show how the extension would be 2406 expressed: 2408 { 2409 "ietf-mud:mud": { 2410 "mud-url": "https://bms.example.com/.well-known/mud/v1/lightbulb", 2411 "last-update": "2017-09-20T15:49:18+02:00", 2412 "cache-validity": 48, 2413 "is-supported": true, 2414 "systeminfo": "https://bms.example.com/descriptions/lightbulb", 2415 "extensions": [ 2416 "ietf-mud-detext-example" 2417 ], 2418 "ietf-mud-detext-example:is-detnet-required": "false", 2419 "from-device-policy": { 2420 "access-lists": { 2421 "access-list": [ 2422 { 2423 "acl-name": "mud-54684-v6fr", 2424 "acl-type": "ietf-access-control-list:ipv6-acl" 2425 } 2426 ] 2427 } 2428 }, 2429 "to-device-policy": { 2430 "access-lists": { 2431 "access-list": [ 2432 { 2433 "acl-name": "mud-54684-v6to", 2434 "acl-type": "ietf-access-control-list:ipv6-acl" 2435 } 2436 ] 2437 } 2438 } 2439 }, 2440 "ietf-access-control-list:access-lists": { 2441 "acl": [ 2442 { 2443 "acl-name": "mud-54684-v6to", 2444 "acl-type": "ipv6-acl", 2445 "access-list-entries": { 2446 "ace": [ 2447 { 2448 "rule-name": "cl0-todev", 2449 "matches": { 2450 "ipv6-acl": { 2451 "ietf-acldns:src-dnsname": "service.bms.example.com", 2452 "protocol": 6, 2453 "source-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 "forwarding": "accept" 2464 } 2465 } 2466 ] 2467 } 2468 }, 2469 { 2470 "acl-name": "mud-54684-v6fr", 2471 "acl-type": "ipv6-acl", 2472 "access-list-entries": { 2473 "ace": [ 2474 { 2475 "rule-name": "cl0-frdev", 2476 "matches": { 2477 "ipv6-acl": { 2478 "ietf-acldns:dst-dnsname": "service.bms.example.com", 2479 "protocol": 6, 2480 "destination-port-range": { 2481 "lower-port": 443, 2482 "upper-port": 443 2483 } 2484 }, 2485 "tcp-acl": { 2486 "ietf-mud:direction-initiated": "from-device" 2487 } 2488 }, 2489 "actions": { 2490 "forwarding": "accept" 2491 } 2493 } 2494 ] 2495 } 2496 } 2497 ] 2498 } 2499 } 2501 Authors' Addresses 2503 Eliot Lear 2504 Cisco Systems 2505 Richtistrasse 7 2506 Wallisellen CH-8304 2507 Switzerland 2509 Phone: +41 44 878 9200 2510 Email: lear@cisco.com 2512 Ralph Droms 2514 Phone: +1 978 376 3731 2515 Email: rdroms@gmail.com 2517 Dan Romascanu 2519 Phone: +972 54 5555347 2520 Email: dromasca@gmail.com