idnits 2.17.1 draft-ietf-opsawg-mud-14.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 1022 has weird spacing: '...ecified model...' == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: Note when using either of these with a MUD file, because access is associated with a particular Thing, MUD files MUST not contain either a src-dnsname in an ACL associated with from-device-policy or a dst-dnsname associated with to-device-policy. -- The document date (January 24, 2018) is 2277 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-21) exists of draft-ietf-netmod-acl-model-15 == Outdated reference: A later version (-06) exists of draft-ietf-netmod-yang-tree-diagrams-05 -- Possible downref: Non-RFC (?) normative reference: ref. 'IEEE8021AB' ** Obsolete normative reference: RFC 2618 (Obsoleted by RFC 4668) ** Obsolete normative reference: RFC 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 7230 (Obsoleted by RFC 9110, RFC 9112) ** Obsolete normative reference: RFC 7231 (Obsoleted by RFC 9110) == Outdated reference: A later version (-20) exists of draft-ietf-netmod-rfc6087bis-16 -- Obsolete informational reference (is this intentional?): RFC 7042 (Obsoleted by RFC 9542) Summary: 5 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: July 28, 2018 6 D. Romascanu 7 January 24, 2018 9 Manufacturer Usage Description Specification 10 draft-ietf-opsawg-mud-14 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 https://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 July 28, 2018. 41 Copyright Notice 43 Copyright (c) 2018 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 (https://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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 62 1.4. Determining Intended Use . . . . . . . . . . . . . . . . 6 63 1.5. Finding A Policy: The MUD URL . . . . . . . . . . . . . . 6 64 1.6. Processing of the MUD URL . . . . . . . . . . . . . . . . 7 65 1.7. Types of Policies . . . . . . . . . . . . . . . . . . . . 7 66 1.8. The Manufacturer Usage Description Architecture . . . . . 9 67 1.9. Order of operations . . . . . . . . . . . . . . . . . . . 11 68 2. The MUD Model and Semantic Meaning . . . . . . . . . . . . . 11 69 2.1. The IETF-MUD YANG Module . . . . . . . . . . . . . . . . 12 70 3. Data Node Definitions . . . . . . . . . . . . . . . . . . . . 14 71 3.1. mud-version . . . . . . . . . . . . . . . . . . . . . . . 14 72 3.2. to-device-policy and from-device-policy containers . . . 14 73 3.3. last-update . . . . . . . . . . . . . . . . . . . . . . . 14 74 3.4. cache-validity . . . . . . . . . . . . . . . . . . . . . 14 75 3.5. is-supported . . . . . . . . . . . . . . . . . . . . . . 14 76 3.6. systeminfo . . . . . . . . . . . . . . . . . . . . . . . 15 77 3.7. extensions . . . . . . . . . . . . . . . . . . . . . . . 15 78 3.8. manufacturer . . . . . . . . . . . . . . . . . . . . . . 15 79 3.9. same-manufacturer . . . . . . . . . . . . . . . . . . . . 15 80 3.10. model . . . . . . . . . . . . . . . . . . . . . . . . . . 15 81 3.11. local-networks . . . . . . . . . . . . . . . . . . . . . 16 82 3.12. controller . . . . . . . . . . . . . . . . . . . . . . . 16 83 3.13. my-controller . . . . . . . . . . . . . . . . . . . . . . 16 84 3.14. direction-initiated . . . . . . . . . . . . . . . . . . . 16 85 4. Processing of the MUD file . . . . . . . . . . . . . . . . . 17 86 5. What does a MUD URL look like? . . . . . . . . . . . . . . . 17 87 6. The MUD YANG Model . . . . . . . . . . . . . . . . . . . . . 18 88 7. The Domain Name Extension to the ACL Model . . . . . . . . . 23 89 7.1. src-dnsname . . . . . . . . . . . . . . . . . . . . . . . 24 90 7.2. destination-dnsname . . . . . . . . . . . . . . . . . . . 24 91 7.3. The ietf-acldns Model . . . . . . . . . . . . . . . . . . 24 92 8. MUD File Example . . . . . . . . . . . . . . . . . . . . . . 26 93 9. The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . . 28 94 9.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 29 95 9.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 29 96 9.3. Relay Requirements . . . . . . . . . . . . . . . . . . . 30 98 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 30 99 11. The Manufacturer Usage Description LLDP extension . . . . . . 31 100 12. Creating and Processing of Signed MUD Files . . . . . . . . . 33 101 12.1. Creating a MUD file signature . . . . . . . . . . . . . 33 102 12.2. Verifying a MUD file signature . . . . . . . . . . . . . 33 103 13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 34 104 14. Deployment Considerations . . . . . . . . . . . . . . . . . . 34 105 15. Security Considerations . . . . . . . . . . . . . . . . . . . 35 106 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 107 16.1. YANG Module Registrations . . . . . . . . . . . . . . . 37 108 16.2. DHCPv4 and DHCPv6 Options . . . . . . . . . . . . . . . 38 109 16.3. PKIX Extensions . . . . . . . . . . . . . . . . . . . . 38 110 16.4. Well Known URI Suffix . . . . . . . . . . . . . . . . . 38 111 16.5. MIME Media-type Registration for MUD files . . . . . . . 38 112 16.6. LLDP IANA TLV Subtype Registry . . . . . . . . . . . . . 39 113 16.7. The MUD Well Known Universal Resource Name (URNs) . . . 40 114 16.8. Extensions Registry . . . . . . . . . . . . . . . . . . 40 115 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 40 116 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 41 117 18.1. Normative References . . . . . . . . . . . . . . . . . . 41 118 18.2. Informative References . . . . . . . . . . . . . . . . . 43 119 Appendix A. Changes from Earlier Versions . . . . . . . . . . . 45 120 Appendix B. Default MUD nodes . . . . . . . . . . . . . . . . . 48 121 Appendix C. A Sample Extension: DETNET-indicator . . . . . . . . 52 122 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 55 124 1. Introduction 126 The Internet has largely been constructed for general purpose 127 computers, those devices that may be used for a purpose that is 128 specified by those who own the device. [RFC1984] presumed that an 129 end device would be most capable of protecting itself. This made 130 sense when the typical device was a workstation or a mainframe, and 131 it continues to make sense for general purpose computing devices 132 today, including laptops, smart phones, and tablets. 134 [RFC7452] discusses design patterns for, and poses questions about, 135 smart objects. Let us then posit a group of objects that are 136 specifically not general purpose computers. These devices, which 137 this memo refers to as Things, have a specific purpose. By 138 definition, therefore, all other uses are not intended. The 139 combination of these two statements can be restated as a manufacturer 140 usage description (MUD) that can be applied at various points within 141 a network. 143 We use the notion of "manufacturer" loosely in this context to refer 144 to the entity or organization that will state how a device is 145 intended to be used. For example, in the context of a lightbulb, 146 this might indeed be the lightbulb manufacturer. In the context of a 147 smarter device that has a built in Linux stack, it might be an 148 integrator of that device. The key points are that the device itself 149 is assumed to serve a limited purpose, and that there may exist an 150 organization in the supply chain of that device that will take 151 responsibility for informing the network about that purpose. 153 The intent of MUD is to provide the following: 155 o Substantially reduce the threat surface on a device entering a 156 network to those communications intended by the manufacturer. 158 o Provide a means to scale network policies to the ever-increasing 159 number of types of devices in the network. 161 o Provide a means to address at least some vulnerabilities in a way 162 that is faster than the time it might take to update systems. 163 This will be particularly true for systems that are no longer 164 supported by their manufacturer. 166 o Keep the cost of implementation of such a system to the bare 167 minimum. 169 o Provide a means of extensibility for manufacturers to express 170 other device capabilities or requirements. 172 MUD consists of three architectural building blocks: 174 o A URL that is can be used to locate a description; 176 o The description itself, including how it is interpreted, and; 178 o A means for local network management systems to retrieve the 179 description. 181 In this specification we describe each of these building blocks and 182 how they are intended to be used together. However, they may also be 183 used separately, independent of this specification, by local 184 deployments for their own purposes. 186 1.1. What MUD Doesn't Do 188 MUD is not intended to address network authorization of general 189 purpose computers, as their manufacturers cannot envision a specific 190 communication pattern to describe. In addition, even those devices 191 that have a single or small number of uses might have very broad 192 communication patterns. MUD on its own is not for them either. 194 Although MUD can provide network administrators with some additional 195 protection when device vulnerabilities exist, it will never replace 196 the need for manufacturers to patch vulnerabilities. 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 application on a smart phone. 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. Terminology 220 MUD: manufacturer usage description. 222 MUD file: a file containing YANG-based JSON that describes a Thing 223 and associated suggested specific network behavior. 225 MUD file server: a web server that hosts a MUD file. 227 MUD controller: the system that requests and receives the MUD file 228 from the MUD server. After it has processed a MUD file, it may 229 direct changes to relevant network elements. 231 MUD URL: a URL that can be used by the MUD controller to receive the 232 MUD file. 234 Thing: the device emitting a MUD URL. 236 Manufacturer: the entity that configures the Thing to emit the MUD 237 URL and the one who asserts a recommendation in a MUD file. The 238 manufacturer might not always be the entity that constructs a 239 Thing. It could, for instance, be a systems integrator, or even a 240 component provider. 242 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 243 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 244 document are to be interpreted as described in [RFC2119]. 246 1.4. Determining Intended Use 248 The notion of intended use is in itself not new. Network 249 administrators apply access lists every day to allow for only such 250 use. This notion of white listing was well described by Chapman and 251 Zwicky in [FW95]. Profiling systems that make use of heuristics to 252 identify types of systems have existed for years as well. 254 A Thing could just as easily tell the network what sort of access it 255 requires without going into what sort of system it is. This would, 256 in effect, be the converse of [RFC7488]. In seeking a general 257 purpose solution, however, we assume that a device has so few 258 capabilities that it will implement the least necessary capabilities 259 to function properly. This is a basic economic constraint. Unless 260 the network would refuse access to such a device, its developers 261 would have no reason to provide the network any information. To 262 date, such an assertion has held true. 264 1.5. Finding A Policy: The MUD URL 266 Our work begins with the device emitting a Universal Resource Locator 267 (URL) [RFC3986]. This URL serves both to classify the device type 268 and to provide a means to locate a policy file. 270 In this memo three means are defined to emit the MUD URL, as follows: 272 o A DHCP option[RFC2131],[RFC3315] that the DHCP client uses to 273 inform the DHCP server. The DHCP server may take further actions, 274 such as retrieve the URL or otherwise pass it along to network 275 management system or controller. 277 o An X.509 constraint. The IEEE has developed [IEEE8021AR] that 278 provides a certificate-based approach to communicate device 279 characteristics, which itself relies on [RFC5280]. The MUD URL 280 extension is non-critical, as required by IEEE 802.1AR. Various 281 means may be used to communicate that certificate, including 282 Tunnel Extensible Authentication Protocol (TEAP) [RFC7170]. 284 o Finally, a Link Layer Discovery Protocol (LLDP) frame is defined 285 [IEEE8021AB]. 287 It is possible that there may be other means for a MUD URL to be 288 learned by a network. For instance, some devices may already be 289 fielded or have very limited ability to communicate a MUD URL, and 290 yet can be identified through some means, such as a serial number or 291 a public key. In these cases, manufacturers may be able to map those 292 identifiers to particular MUD URLs (or even the files themselves). 293 Similarly, there may be alternative resolution mechanisms available 294 for situations where Internet connectivity is limited or does not 295 exist. Such mechanisms are not described in this memo, but are 296 possible. Implementors should allow for this sort of flexibility of 297 how MUD URLs may be learned. 299 1.6. Processing of the MUD URL 301 MUD URLs MUST use the HTTPS scheme [RFC7230]. 303 MUD controllers that are able to do so SHOULD retrieve MUD URLs and 304 signature files as per [RFC7230], using the GET method [RFC7231]. 305 They MUST validate the certificate using the rules in [RFC2618], 306 Section 3.1. 308 Requests for MUD URLs SHOULD include an "Accept" header ([RFC7231], 309 Section 5.3.2) containing "application/mud+json", an "Accept- 310 Language" header ([RFC7231], Section 5.3.5), and a "User-Agent" 311 header ([RFC7231], Section 5.5.3). 313 MUD controllers SHOULD automatically process 3xx response status 314 codes. 316 If a MUD controller is not able to fetch a MUD URL, other means MAY 317 be used to import MUD files and associated signature files. So long 318 as the signature of the file can be validated, the file can be used. 319 In such environments, controllers SHOULD warn administrators when 320 cache-validity expiry is approaching so that they may check for new 321 files. 323 1.7. Types of Policies 325 When the MUD URL is resolved, the MUD controller retrieves a file 326 that describes what sort of communications a device is designed to 327 have. The manufacturer may specify either specific hosts for cloud 328 based services or certain classes for access within an operational 329 network. An example of a class might be "devices of a specified 330 manufacturer type", where the manufacturer type itself is indicated 331 simply by the authority component (e.g, the domain name) of the MUD 332 URL. Another example might be to allow or disallow local access. 333 Just like other policies, these may be combined. For example: 335 o Allow access to devices of the same manufacturer 336 o Allow access to and from controllers via Constrained Application 337 Protocol (COAP)[RFC7252] 339 o Allow access to local DNS/NTP 341 o Deny all other access 343 A printer might have a description that states: 345 o Allow access for port IPP or port LPD 347 o Allow local access for port HTTP 349 o Deny all other access 351 In this way anyone can print to the printer, but local access would 352 be required for the management interface. 354 The files that are retrieved are intended to be closely aligned to 355 existing network architectures so that they are easy to deploy. We 356 make use of YANG [RFC7950] because of the time and effort spent to 357 develop accurate and adequate models for use by network devices. 358 JSON is used as a serialization for compactness and readability, 359 relative to XML. Other formats may be chosen with later versions of 360 MUD. 362 While the policy examples given here focus on access control, this is 363 not intended to be the sole focus. By structuring the model 364 described in this document with clear extension points, other 365 descriptions could be included. One that often comes to mind is 366 quality of service. 368 The YANG modules specified here are extensions of 369 [I-D.ietf-netmod-acl-model]. The extensions to this model allow for 370 a manufacturer to express classes of systems that a manufacturer 371 would find necessary for the proper function of the device. Two 372 modules are specified. The first module specifies a means for domain 373 names to be used in ACLs so that devices that have their controllers 374 in the cloud may be appropriately authorized with domain names, where 375 the mapping of those names to addresses may rapidly change. 377 The other module abstracts away IP addresses into certain classes 378 that are instantiated into actual IP addresses through local 379 processing. Through these classes, manufacturers can specify how the 380 device is designed to communicate, so that network elements can be 381 configured by local systems that have local topological knowledge. 382 That is, the deployment populates the classes that the manufacturer 383 specifies. The abstractions below map to zero or more hosts, as 384 follows: 386 Manufacturer: A device made by a particular manufacturer, as 387 identified by the authority component of its MUD URL 389 same-manufacturer: Devices that have the same authority component of 390 their MUD URL. 392 controller: Devices that the local network administrator admits to 393 the particular class. 395 my-controller: Devices associated with the MUD URL of a device that 396 the administrator admits. 398 local: The class of IP addresses that are scoped within some 399 administrative boundary. By default it is suggested that this be 400 the local subnet. 402 The "manufacturer" classes can be easily specified by the 403 manufacturer, whereas controller classes are initially envisioned to 404 be specified by the administrator. 406 Because manufacturers do not know who will be using their devices, it 407 is important for functionality referenced in usage descriptions to be 408 relatively ubiquitous and mature. For these reasons only a limited 409 subset YANG-based configuration is permitted in a MUD file. 411 1.8. The Manufacturer Usage Description Architecture 413 With these components laid out we now have the basis for an 414 architecture. This leads us to ASCII art. 416 ....................................... 417 . ____________ . _____________ 418 . | | . | | 419 . | MUD |-->get URL-->| MUD | 420 . | Controller | .(https) | File Server | 421 . End system network |____________|<-MUD file<-<|_____________| 422 . . . 423 . . . 424 . _______ _________ . 425 .| | (dhcp et al) | router | . 426 .| Thing |---->MUD URL-->| or | . 427 .|_______| | switch | . 428 . |_________| . 429 ....................................... 431 Figure 1: MUD Architecture 433 In the above diagram, the switch or router collects MUD URLs and 434 forwards them to the MUD controller (a network management system) for 435 processing. This happens in different ways, depending on how the URL 436 is communicated. For instance, in the case of DHCP, the DHCP server 437 might receive the URL and then process it. In the case of IEEE 438 802.1X, the switch would carry the URL via a certificate to the 439 authentication server via EAP over Radius[RFC3748], which would then 440 process it. One method to do this is TEAP, described in [RFC7170]. 441 The certificate extension is described below. 443 The information returned by the MUD file server (a web server) is 444 valid for the duration of the Thing's connection, or as specified in 445 the description. Thus if the Thing is disconnected, any associated 446 configuration in the switch can be removed. Similarly, from time to 447 time the description may be refreshed, based on new capabilities or 448 communication patterns or vulnerabilities. 450 The web site is typically run by or on behalf of the manufacturer. 451 Its domain name is that of the authority found in the MUD URL. For 452 legacy cases where Things cannot emit a URL, if the switch is able to 453 determine the appropriate URL, it may proxy it, the trivial cases 454 being a hardcoded MUD-URL on a switch port, or a mapping from some 455 available identifier such as an L2 address or certificate hash to a 456 MUD-URL. 458 The role of the MUD controller in this environment is to do the 459 following: 461 o receive MUD URLs, 463 o fetch MUD files, 464 o translate abstractions in the MUD files to specific network 465 element configuration, 467 o maintain and update any required mappings of the abstractions, and 469 o update network elements with appropriate configuration. 471 A MUD controller may be a component of a AAA or network management 472 system. Communication within those systems and from those systems to 473 network elements is beyond the scope of this memo. 475 1.9. Order of operations 477 As mentioned above, MUD contains architectural building blocks, and 478 so order of operation may vary. However, here is one clear intended 479 example: 481 1. Thing emits URL. 483 2. That URL is forwarded to a MUD controller by the nearest switch 484 (how this happens depends on the way in which the MUD URL is 485 emitted). 487 3. The MUD controller retrieves the MUD file and signature from the 488 MUD file server, assuming it doesn't already have copies. After 489 validating the signature, it may test the URL against a web or 490 domain reputation service, and it may test any hosts within the 491 file against those reputation services, as it deems fit. 493 4. The MUD controller may query the administrator for permission to 494 add the Thing and associated policy. If the Thing is known or 495 the Thing type is known, it may skip this step. 497 5. The MUD controller instantiates local configuration based on the 498 abstractions defined in this document. 500 6. The MUD controller configures the switch nearest the Thing. 501 Other systems may be configured as well. 503 7. When the Thing disconnects, policy is removed. 505 2. The MUD Model and Semantic Meaning 507 A MUD file consists of a YANG model that has been serialized in JSON 508 [RFC7951]. For purposes of MUD, the nodes that can be modified are 509 access lists as augmented by this model. The MUD file is limited to 510 the serialization of only the following YANG schema: 512 o ietf-access-control-list [I-D.ietf-netmod-acl-model] 514 o ietf-mud (this document) 516 o ietf-acldns (this document) 518 Extensions may be used to add additional schema. This is described 519 further on. 521 To provide the widest possible deployment, publishers of MUD files 522 SHOULD make use of the abstractions in this memo and avoid the use of 523 IP addresses. A MUD controller SHOULD NOT automatically implement 524 any MUD file that contains IP addresses, especially those that might 525 have local significance. The addressing of one side of an access 526 list is implicit, based on whether it is applied as to-device-policy 527 or from-device-policy. 529 With the exceptions of "name", "acl-type", "rule-name", and TCP and 530 UDP source and destination port information, publishers of MUD files 531 SHOULD limit the use of ACL model leaf nodes expressed to those found 532 in this specification. Absent any extensions, MUD files are assumed 533 to implement only the following ACL model features: 535 o match-on-ipv4, match-on-ipv6, match-on-tcp, match-on-udp, match- 536 on-icmp 538 Furthermore, only "accept" or "drop" actions SHOULD be included. A 539 MUD controller MAY choose to interpret "reject" as "drop". A MUD 540 controller SHOULD ignore all other actions. 542 In fact, MUD controllers MAY ignore any particular component of a 543 description or MAY ignore the description in its entirety, and SHOULD 544 carefully inspect all MUD descriptions. Publishers of MUD files MUST 545 NOT include other nodes except as described in Section 3.7. See that 546 section for more information. 548 2.1. The IETF-MUD YANG Module 550 This module is structured into three parts: 552 o The first container "mud" holds information that is relevant to 553 retrieval and validity of the MUD file itself, as well as policy 554 intended to and from the Thing. 556 o The second component augments the matching container of the ACL 557 model to add several nodes that are relevant to the MUD URL, or 558 otherwise abstracted for use within a local environment. 560 o The third component augments the tcp-acl container of the ACL 561 model to add the ability to match on the direction of initiation 562 of a TCP connection. 564 A valid MUD file will contain two root objects, a "mud" container and 565 an "access-lists" container. Extensions may add additional root 566 objects as required. As a reminder, when parsing access-lists, 567 elements within a "match" block are logically ANDed. In general, a 568 single abstraction in a match statement should be used. For 569 instance, it makes little sense to match both "my-controller" and 570 "controller" with an argument, since they are highly unlikely to be 571 the same value. 573 A simplified graphical representation of the data models is used in 574 this document. The meaning of the symbols in these diagrams is 575 explained in [I-D.ietf-netmod-yang-tree-diagrams]. 577 module: ietf-mud 578 +--rw mud! 579 +--rw mud-version uint8 580 +--rw mud-url inet:uri 581 +--rw last-update yang:date-and-time 582 +--rw cache-validity? uint8 583 +--rw is-supported boolean 584 +--rw systeminfo? inet:uri 585 +--rw extensions* string 586 +--rw from-device-policy 587 | +--rw access-lists 588 | +--rw access-list* [name] 589 | +--rw name -> /acl:access-lists/acl/name 590 +--rw to-device-policy 591 +--rw access-lists 592 +--rw access-list* [name] 593 +--rw name -> /acl:access-lists/acl/name 594 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches: 595 +--rw mud 596 +--rw manufacturer? inet:host 597 +--rw same-manufacturer? empty 598 +--rw model? inet:uri 599 +--rw local-networks? empty 600 +--rw controller? inet:uri 601 +--rw my-controller? empty 602 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches 603 /acl:l4/acl:tcp: 604 +--rw direction-initiated? direction 606 3. Data Node Definitions 608 Note that in this section, when we use the term "match" we are 609 referring to the ACL model "matches" node. 611 The following nodes are defined. 613 3.1. mud-version 615 This node specifies the integer version of the MUD specification. 616 This memo specifies version 1. 618 3.2. to-device-policy and from-device-policy containers 620 [I-D.ietf-netmod-acl-model] describes access-lists. In the case of 621 MUD, a MUD file must be explicit in describing the communication 622 pattern of a Thing, and that includes indicating what is to be 623 permitted or denied in either direction of communication. Hence each 624 of these containers indicates the appropriate direction of a flow in 625 association with a particular Thing. They contain references to 626 specific access-lists. 628 3.3. last-update 630 This is a date-and-time value of when the MUD file was generated. 631 This is akin to a version number. Its form is taken from [RFC6991] 632 which, for those keeping score, in turn was taken from Section 5.6 of 633 [RFC3339], which was taken from [ISO.8601.1988]. 635 3.4. cache-validity 637 This uint8 is the period of time in hours that a network management 638 station MUST wait since its last retrieval before checking for an 639 update. It is RECOMMENDED that this value be no less than 24 and 640 MUST NOT be more than 168 for any Thing that is supported. This 641 period SHOULD be no shorter than any period determined through HTTP 642 caching directives (e.g., "cache-control" or "Expires"). N.B., 643 expiring of this timer does not require the MUD controller to discard 644 the MUD file, nor terminate access to a Thing. See Section 15 for 645 more information. 647 3.5. is-supported 649 This boolean is an indication from the manufacturer to the network 650 administrator as to whether or not the Thing is supported. In this 651 context a Thing is said to not be supported if the manufacturer 652 intends never to issue an update to the Thing or never update the MUD 653 file. A MUD controller MAY still periodically check for updates. 655 3.6. systeminfo 657 This is a URL that points to a description of the Thing to be 658 connected. The intent is for administrators to be able to see a 659 localized name associated with the Thing. The referenced URL SHOULD 660 be a localized display string, and MAY be in either HTML or a raw 661 UTF-8 text file. It SHOULD NOT exceed 60 characters worth of display 662 space (that is- what the administrator actually sees), but it MAY 663 contain links to other documents (presumably product documentation). 665 3.7. extensions 667 This optional leaf-list names MUD extensions that are used in the MUD 668 file. Note that NO MUD extensions may be used in a MUD file without 669 the extensions being declared. Implementations MUST ignore any node 670 in this file that they do not understand. 672 Note that extensions can either extend the MUD file as described in 673 the previous paragraph, or they might reference other work. An 674 extension example can be found in Appendix C. 676 3.8. manufacturer 678 This node consists of a hostname that would be matched against the 679 authority component of another Thing's MUD URL. In its simplest form 680 "manufacturer" and "same-manufacturer" may be implemented as access- 681 lists. In more complex forms, additional network capabilities may be 682 used. For example, if one saw the line "manufacturer" : 683 "flobbidy.example.com", then all Things that registered with a MUD 684 URL that contained flobbity.example.com in its authority section 685 would match. 687 3.9. same-manufacturer 689 This null-valued node is an equivalent for when the manufacturer 690 element is used to indicate the authority that is found in another 691 Thing's MUD URL matches that of the authority found in this Thing's 692 MUD URL. For example, if the Thing's MUD URL were 693 https://b1.example.com/.well-known/mud/ThingV1, then all devices that 694 had MUD URL with an authority section of b1.example.com would match. 696 3.10. model 698 This string matches the entire MUD URL, thus covering the model that 699 is unique within the context of the authority. It may contain not 700 only model information, but versioning information as well, and any 701 other information that the manufacturer wishes to add. The intended 702 use is for devices of this precise class to match, to permit or deny 703 communication between one another. 705 3.11. local-networks 707 This null-valued node expands to include local networks. Its default 708 expansion is that packets must not traverse toward a default route 709 that is received from the router. However, administrators may expand 710 the expression as is appropriate in their deployments. 712 3.12. controller 714 This URI specifies a value that a controller will register with the 715 MUD controller. The node then is expanded to the set of hosts that 716 are so registered. This node may also be a URN. In this case, the 717 URN describes a well known service, such as DNS or NTP. 719 Great care should be used when invoking the controller class. For 720 one thing, it requires some understanding by the administrator as to 721 when it is appropriate. Classes that are standardized may make it 722 possible to easily name devices that support standard functions. For 723 instance, the MUD controller could have some knowledge of which DNS 724 servers should be used for any particular group of Things. Non- 725 standard classes will likely require some sort of administrator 726 interaction. Pre-registration in such classes by controllers with 727 the MUD server is encouraged. The mechanism to do that is beyond the 728 scope of this work. 730 Controller URIs MAY take the form of a URL (e.g. "http[s]://"). 731 However, MUD controllers MUST NOT resolve and retrieve such files, 732 and it is RECOMMENDED that there be no such file at this time, as 733 their form and function may be defined at a point in the future. For 734 now, URLs should serve simply as class names and be populated by the 735 local deployment administrator. 737 3.13. my-controller 739 This null-valued node signals to the MUD controller to use whatever 740 mapping it has for this MUD URL to a particular group of hosts. This 741 may require prompting the administrator for class members. Future 742 work should seek to automate membership management. 744 3.14. direction-initiated 746 When applied this matches packets when the flow was initiated in the 747 corresponding direction. [RFC6092] specifies IPv6 guidance best 748 practices. While that document is scoped specifically to IPv6, its 749 contents are applicable for IPv4 as well. When this flag is set, and 750 the system has no reason to believe a flow has been initiated it MUST 751 drop the packet. This node may be implemented in its simplest form 752 by looking at naked SYN bits, but may also be implemented through 753 more stateful mechanisms. 755 4. Processing of the MUD file 757 To keep things relatively simple in addition to whatever definitions 758 exist, we also apply two additional default behaviors: 760 o Anything not explicitly permitted is denied. 762 o Local DNS and NTP are, by default, permitted to and from the 763 Thing. 765 An explicit description of the defaults can be found in Appendix B. 767 5. What does a MUD URL look like? 769 To begin with, MUD takes full advantage of both the https: scheme and 770 the use of .well-known. HTTPS is important in this case because a 771 man in the middle attack could otherwise harm the operation of a 772 class of Things. .well-known is used because we wish to add 773 additional structure to the URL, and want to leave open for future 774 versions both the means by which the URL is processed and the format 775 of the MUD file retrieved (there have already been some discussions 776 along these lines). The URL appears as follows: 778 mud-url = "https://" authority "/.well-known/mud/" 779 "/" modelinfo ( "?" extras ) 780 ; authority is from RFC3986 781 modelinfo = segment ; from RFC3986 782 extras = query ; from RFC3986 784 Taken together with the mud-url, "modelinfo" represents a Thing model 785 as the manufacturer wishes to represent it. It could be a brand name 786 or something more specific. It also may provide a means to indicate 787 what version the product is. Specifically if it has been updated in 788 the field, this is the place where evidence of that update would 789 appear. The field should be changed when the intended communication 790 patterns of a Thing change. While from a controller standpoint, only 791 comparison and matching operations are safe, it is envisioned that 792 updates will require some administrative review. 794 "extras" is intended for use by the MUD controller to provide 795 additional information such as posture about the Thing to the MUD 796 file server. This field MUST NOT be configured on the Thing itself 797 by a manufacturer - that is what "modelinfo" is for. It is left as 798 future work to define the full semantics of this field. 800 6. The MUD YANG Model 802 file "ietf-mud@2018-01-24.yang" 803 module ietf-mud { 804 yang-version 1.1; 805 namespace "urn:ietf:params:xml:ns:yang:ietf-mud"; 806 prefix ietf-mud; 808 import ietf-access-control-list { 809 prefix acl; 810 } 811 import ietf-yang-types { 812 prefix yang; 813 } 814 import ietf-inet-types { 815 prefix inet; 816 } 818 organization 819 "IETF OPSAWG (Ops Area) Working Group"; 820 contact 821 "WG Web: http://tools.ietf.org/wg/opsawg/ 822 WG List: opsawg@ietf.org 823 Author: Eliot Lear 824 lear@cisco.com 825 Author: Ralph Droms 826 rdroms@gmail.com 827 Author: Dan Romascanu 828 dromasca@gmail.com 830 "; 831 description 832 "This YANG module defines a component that augments the 833 IETF description of an access list. This specific module 834 focuses on additional filters that include local, model, 835 and same-manufacturer. 837 This module is intended to be serialized via JSON and stored 838 as a file, as described in RFC XXXX [RFC Editor to fill in with 839 this document #]. 841 Copyright (c) 2016,2017 IETF Trust and the persons 842 identified as the document authors. All rights reserved. 843 Redistribution and use in source and binary forms, with or 844 without modification, is permitted pursuant to, and subject 845 to the license terms contained in, the Simplified BSD 846 License set forth in Section 4.c of the IETF Trust's Legal 847 Provisions Relating to IETF Documents 848 (http://trustee.ietf.org/license-info). 849 This version of this YANG module is part of RFC XXXX; see 850 the RFC itself for full legal notices."; 852 revision 2018-01-24 { 853 description 854 "Initial proposed standard."; 855 reference 856 "RFC XXXX: Manufacturer Usage Description 857 Specification"; 858 } 860 typedef direction { 861 type enumeration { 862 enum "to-device" { 863 description 864 "packets or flows destined to the target 865 Thing"; 866 } 867 enum "from-device" { 868 description 869 "packets or flows destined from 870 the target Thing"; 871 } 872 } 873 description 874 "Which way are we talking about?"; 875 } 877 container mud { 878 presence "Enabled for this particular MUD URL"; 879 description 880 "MUD related information, as specified 881 by RFC-XXXX [RFC Editor to fill in]."; 882 uses mud-grouping; 883 } 885 grouping mud-grouping { 886 description 887 "Information about when support end(ed), and 888 when to refresh"; 890 leaf mud-version { 891 type uint8; 892 mandatory true; 893 description "This is the version of the MUD 894 specification. This memo specifies version 1."; 895 } 897 leaf mud-url { 898 type inet:uri; 899 mandatory true; 900 description 901 "This is the MUD URL associated with the entry found 902 in a MUD file."; 903 } 904 leaf last-update { 905 type yang:date-and-time; 906 mandatory true; 907 description 908 "This is intended to be when the current MUD file 909 was generated. MUD Controllers SHOULD NOT check 910 for updates between this time plus cache validity"; 911 } 912 leaf cache-validity { 913 type uint8 { 914 range "1..168"; 915 } 916 units "hours"; 917 default "48"; 918 description 919 "The information retrieved from the MUD server is 920 valid for these many hours, after which it should 921 be refreshed. N.B. MUD controller implementations 922 need not discard MUD files beyond this period."; 923 } 924 leaf is-supported { 925 type boolean; 926 mandatory true; 927 description 928 "This boolean indicates whether or not the Thing is 929 currently supported by the manufacturer."; 930 } 931 leaf systeminfo { 932 type inet:uri; 933 description 934 "A URL to a description of this Thing. This 935 should be a brief localized description. The 936 reference text should be no more than octets. 937 systeminfo may be displayed to the user to 938 determine whether to allow the Thing on the 939 network."; 941 } 942 leaf-list extensions { 943 type string { 944 length "1..40"; 945 } 946 description 947 "A list of extension names that are used in this MUD 948 file. Each name is registered with the IANA and 949 described in an RFC."; 950 } 951 container from-device-policy { 952 description 953 "The policies that should be enforced on traffic 954 coming from the device. These policies are not 955 necessarily intended to be enforced at a single 956 point, but may be rendered by the controller to any 957 relevant enorcement points in the network or 958 elsewhere."; 959 uses access-lists; 960 } 961 container to-device-policy { 962 description 963 "The policies that should be enforced on traffic 964 going to the device. These policies are not 965 necessarily intended to be enforced at a single 966 point, but may be rendered by the controller to any 967 relevant enorcement points in the network or 968 elsewhere."; 969 uses access-lists; 970 } 971 } 973 grouping access-lists { 974 description 975 "A grouping for access lists in the context of device 976 policy."; 977 container access-lists { 978 description 979 "The access lists that should be applied to traffic 980 to or from the device."; 981 list access-list { 982 key "name"; 983 description 984 "Each entry on this list refers to an ACL that 985 should be present in the overall access list 986 data model. Each ACL is identified by name and 987 type."; 988 leaf name { 989 type leafref { 990 path "/acl:access-lists/acl:acl/acl:name"; 991 } 992 description 993 "The name of the ACL for this entry."; 994 } 995 } 996 } 997 } 998 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches" { 999 description 1000 "adding abstractions to avoid need of IP addresses"; 1001 container mud { 1002 description 1003 "MUD-specific matches."; 1004 leaf manufacturer { 1005 type inet:host; 1006 description 1007 "A domain that is intended to match the authority 1008 section of the MUD URL. This node is used to specify 1009 one or more manufacturers a device should 1010 be authorized to access."; 1011 } 1012 leaf same-manufacturer { 1013 type empty; 1014 description 1015 "This node matches the authority section of the MUD URL 1016 of a Thing. It is intended to grant access to all 1017 devices with the same authority section."; 1018 } 1019 leaf model { 1020 type inet:uri; 1021 description 1022 "Devices of the specified model type will match if 1023 they have an identical MUD URL."; 1024 } 1025 leaf local-networks { 1026 type empty; 1027 description 1028 "IP addresses will match this node if they are 1029 considered local addresses. A local address may be 1030 a list of locally defined prefixes and masks 1031 that indicate a particular administrative scope."; 1032 } 1033 leaf controller { 1034 type inet:uri; 1035 description 1036 "This node names a class that has associated with it 1037 zero or more IP addresses to match against. These 1038 may be scoped to a manufacturer or via a standard 1039 URN."; 1040 } 1041 leaf my-controller { 1042 type empty; 1043 description 1044 "This node matches one or more network elements that 1045 have been configured to be the controller for this 1046 Thing, based on its MUD URL."; 1047 } 1048 } 1049 } 1050 augment "/acl:access-lists/acl:acl/acl:aces/" + 1051 "acl:ace/acl:matches/acl:l4/acl:tcp" { 1052 description 1053 "Adding domain names to matching"; 1054 leaf direction-initiated { 1055 type direction; 1056 description 1057 "This node matches based on which direction a 1058 connection was initiated. The means by which that 1059 is determined is discussed in this document."; 1060 } 1061 } 1062 } 1064 1066 7. The Domain Name Extension to the ACL Model 1068 This module specifies an extension to IETF-ACL model such that domain 1069 names may be referenced by augmenting the "matches" node. Different 1070 implementations may deploy differing methods to maintain the mapping 1071 between IP address and domain name, if indeed any are needed. 1072 However, the intent is that resources that are referred to using a 1073 name should be authorized (or not) within an access list. 1075 The structure of the change is as follows: 1077 module: ietf-acldns 1078 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches 1079 /acl:l3/acl:ipv4: 1080 +--rw src-dnsname? inet:host 1081 +--rw dst-dnsname? inet:host 1082 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches 1083 /acl:l3/acl:ipv6: 1084 +--rw src-dnsname? inet:host 1085 +--rw dst-dnsname? inet:host 1087 The choice of these particular points in the access-list model is 1088 based on the assumption that we are in some way referring to IP- 1089 related resources, as that is what the DNS returns. A domain name in 1090 our context is defined in [RFC6991]. The augmentations are 1091 replicated across IPv4 and IPv6 to allow MUD file authors the ability 1092 to control the IP version that the Thing may utilize. 1094 The following node are defined. 1096 7.1. src-dnsname 1098 The argument corresponds to a domain name of a source as specified by 1099 inet:host. A number of means may be used to resolve hosts. What is 1100 important is that such resolutions be consistent with ACLs required 1101 by Things to properly operate. 1103 7.2. destination-dnsname 1105 The argument corresponds to a domain name of a destination as 1106 specified by inet:host See the previous section relating to 1107 resolution. 1109 Note when using either of these with a MUD file, because access is 1110 associated with a particular Thing, MUD files MUST not contain either 1111 a src-dnsname in an ACL associated with from-device-policy or a dst- 1112 dnsname associated with to-device-policy. 1114 7.3. The ietf-acldns Model 1116 file "ietf-acldns@2018-01-24.yang" 1117 module ietf-acldns { 1118 yang-version 1.1; 1119 namespace "urn:ietf:params:xml:ns:yang:ietf-acldns"; 1120 prefix "ietf-acldns"; 1122 import ietf-access-control-list { 1123 prefix "acl"; 1125 } 1127 import ietf-inet-types { 1128 prefix "inet"; 1129 } 1131 organization 1132 "IETF OPSAWG (Ops Area) Working Group"; 1134 contact 1135 "WG Web: http://tools.ietf.org/wg/opsawg/ 1136 WG List: opsawg@ietf.org 1137 Author: Eliot Lear 1138 lear@cisco.com 1139 Author: Ralph Droms 1140 rdroms@gmail.com 1141 Author: Dan Romascanu 1142 dromasca@gmail.com 1143 "; 1145 description 1146 "This YANG module defines a component that augments the 1147 IETF description of an access list to allow dns names 1148 as matching criteria."; 1150 revision "2018-01-24" { 1151 description "Base version of dnsname extension of ACL model"; 1152 reference "RFC XXXX: Manufacturer Usage Description 1153 Specification"; 1154 } 1156 grouping dns-matches { 1157 description "Domain names for matching."; 1159 leaf src-dnsname { 1160 type inet:host; 1161 description "domain name to be matched against"; 1162 } 1163 leaf dst-dnsname { 1164 type inet:host; 1165 description "domain name to be matched against"; 1166 } 1167 } 1169 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/" + 1170 "acl:matches/acl:l3/acl:ipv4" { 1171 description "Adding domain names to matching"; 1172 uses dns-matches; 1174 } 1176 augment "/acl:access-lists/acl:acl/" + 1177 "acl:aces/acl:ace/" + 1178 "acl:matches/acl:l3/acl:ipv6" { 1179 description "Adding domain names to matching"; 1180 uses dns-matches; 1181 } 1182 } 1183 1185 8. MUD File Example 1187 This example contains two access lists that are intended to provide 1188 outbound access to a cloud service on TCP port 443. 1190 { 1191 "ietf-mud:mud": { 1192 "mud-version": 1, 1193 "mud-url": "https://bms.example.com/.well-known/mud/lightbulb2000", 1194 "last-update": "2018-01-23T13:33:52+01:00", 1195 "cache-validity": 48, 1196 "is-supported": true, 1197 "systeminfo": "The BMS Example Lightbulb", 1198 "from-device-policy": { 1199 "access-lists": { 1200 "access-list": [ 1201 { 1202 "name": "mud-45782-v6fr" 1203 } 1204 ] 1205 } 1206 }, 1207 "to-device-policy": { 1208 "access-lists": { 1209 "access-list": [ 1210 { 1211 "name": "mud-45782-v6to" 1212 } 1213 ] 1214 } 1215 } 1216 }, 1217 "ietf-access-control-list:access-lists": { 1218 "acl": [ 1219 { 1220 "name": "mud-45782-v6to", 1221 "acl-type": "ipv6-acl-type", 1222 "access-list-entries": { 1223 "ace": [ 1224 { 1225 "rule-name": "cl0-todev", 1226 "matches": { 1227 "ipv6-acl": { 1228 "ietf-acldns:src-dnsname": "service.bms.example.com", 1229 "protocol": 6, 1230 "source-port-range-or-operator": { 1231 "operator": "eq", 1232 "port": 443 1233 } 1234 }, 1235 "tcp": { 1236 "ietf-mud:direction-initiated": "from-device" 1237 } 1238 }, 1239 "actions": { 1240 "forwarding": "accept" 1241 } 1242 } 1243 ] 1244 } 1245 }, 1246 { 1247 "name": "mud-45782-v6fr", 1248 "acl-type": "ipv6-acl-type", 1249 "access-list-entries": { 1250 "ace": [ 1251 { 1252 "rule-name": "cl0-frdev", 1253 "matches": { 1254 "ipv6-acl": { 1255 "ietf-acldns:dst-dnsname": "service.bms.example.com", 1256 "protocol": 6, 1257 "destination-port-range-or-operator": { 1258 "operator": "eq", 1259 "port": 443 1260 } 1261 }, 1262 "tcp": { 1263 "ietf-mud:direction-initiated": "from-device" 1264 } 1265 }, 1266 "actions": { 1267 "forwarding": "accept" 1269 } 1270 } 1271 ] 1272 } 1273 } 1274 ] 1275 } 1276 } 1278 In this example, two policies are declared, one from the Thing and 1279 the other to the Thing. Each policy names an access list that 1280 applies to the Thing, and one that applies from. Within each access 1281 list, access is permitted to packets flowing to or from the Thing 1282 that can be mapped to the domain name of "service.bms.example.com". 1283 For each access list, the enforcement point should expect that the 1284 Thing initiated the connection. 1286 9. The MUD URL DHCP Option 1288 The IPv4 MUD URL client option has the following format: 1290 +------+-----+------------------------------ 1291 | code | len | MUD URL 1292 +------+-----+------------------------------ 1294 Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single 1295 octet that indicates the length of the URL in octets. MUD URL is a 1296 URL. MUD URLs MUST NOT exceed 255 octets. 1298 The IPv6 MUD URL client option has the following format: 1300 0 1 2 3 1301 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 1302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1303 | OPTION_MUD_URL_V6 | option-length | 1304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1305 | MUD URL | 1306 | ... | 1307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1309 OPTION_MUD_URL_V6 (112; assigned by IANA). 1311 option-length contains the length of the URL in octets. 1313 The intent of this option is to provide both a new Thing classifier 1314 to the network as well as some recommended configuration to the 1315 routers that implement policy. However, it is entirely the purview 1316 of the network system as managed by the network administrator to 1317 decide what to do with this information. The key function of this 1318 option is simply to identify the type of Thing to the network in a 1319 structured way such that the policy can be easily found with existing 1320 toolsets. 1322 9.1. Client Behavior 1324 A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit 1325 DHCPv6 option. These options are singletons, as specified in 1326 [RFC7227]. Because clients are intended to have at most one MUD URL 1327 associated with them, they may emit at most one MUD URL option via 1328 DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4 1329 and v6 DHCP options are emitted, the same URL MUST be used. 1331 Clients SHOULD log or otherwise report improper acknowledgments from 1332 servers, but they MUST NOT modify their MUD URL configuration based 1333 on a server's response. The server's response is only an 1334 acknowledgment that the server has processed the option, and promises 1335 no specific network behavior to the client. In particular, it may 1336 not be possible for the server to retrieve the file associated with 1337 the MUD URL, or the local network administration may not wish to use 1338 the usage description. Neither of these situations should be 1339 considered in any way exceptional. 1341 9.2. Server Behavior 1343 A DHCP server may ignore these options or take action based on 1344 receipt of these options. If a server successfully parses the option 1345 and the URL, it MUST return the option with length field set to zero 1346 and a corresponding null URL field as an acknowledgment. Even in 1347 this circumstance, no specific network behavior is guaranteed. When 1348 a server consumes this option, it will either forward the URL and 1349 relevant client information (such as the gateway address or giaddr) 1350 to a network management system, or it will retrieve the usage 1351 description itself by resolving the URL. 1353 DHCP servers may implement MUD functionality themselves or they may 1354 pass along appropriate information to a network management system or 1355 MUD controller. A DHCP server that does process the MUD URL MUST 1356 adhere to the process specified in [RFC2818] and [RFC5280] to 1357 validate the TLS certificate of the web server hosting the MUD file. 1358 Those servers will retrieve the file, process it, create and install 1359 the necessary configuration on the relevant network element. Servers 1360 SHOULD monitor the gateway for state changes on a given interface. A 1361 DHCP server that does not provide MUD functionality and has forwarded 1362 a MUD URL to a MUD controller MUST notify the MUD controller of any 1363 corresponding change to the DHCP state of the client (such as 1364 expiration or explicit release of a network address lease). 1366 9.3. Relay Requirements 1368 There are no additional requirements for relays. 1370 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 1372 This section defines an X.509 non-critical certificate extension that 1373 contains a single Uniform Resource Locator (URL) that points to an 1374 on-line Manufacturer Usage Description concerning the certificate 1375 subject. URI must be represented as described in Section 7.4 of 1376 [RFC5280]. 1378 Any Internationalized Resource Identifiers (IRIs) MUST be mapped to 1379 URIs as specified in Section 3.1 of [RFC3987] before they are placed 1380 in the certificate extension. 1382 The semantics of the URL are defined Section 5 of this document. 1384 The choice of id-pe is based on guidance found in Section 4.2.2 of 1385 [RFC5280]: 1387 These extensions may be used to direct applications to on-line 1388 information about the issuer or the subject. 1390 The MUD URL is precisely that: online information about the 1391 particular subject. 1393 The new extension is identified as follows: 1395 1397 MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) 1398 internet(1) security(5) mechanisms(5) pkix(7) 1399 id-mod(0) id-mod-mudURLExtn2016(88) } 1401 DEFINITIONS IMPLICIT TAGS ::= BEGIN 1403 -- EXPORTS ALL -- 1405 IMPORTS 1406 EXTENSION 1407 FROM PKIX-CommonTypes-2009 1408 { iso(1) identified-organization(3) dod(6) internet(1) 1409 security(5) mechanisms(5) pkix(7) id-mod(0) 1410 id-mod-pkixCommon-02(57) } 1412 id-pe 1413 FROM PKIX1Explicit-2009 1414 { iso(1) identified-organization(3) dod(6) internet(1) 1415 security(5) mechanisms(5) pkix(7) id-mod(0) 1416 id-mod-pkix1-explicit-02(51) } ; 1417 MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... } 1418 ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax 1419 IDENTIFIED BY id-pe-mud-url } 1421 id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 } 1423 MUDURLSyntax ::= IA5String 1425 END 1427 1429 While this extension can appear in either an 802.AR manufacturer 1430 certificate (IDevID) or deployment certificate (LDevID), of course it 1431 is not guaranteed in either, nor is it guaranteed to be carried over. 1432 It is RECOMMENDED that MUD controller implementations maintain a 1433 table that maps a Thing to its MUD URL based on IDevIDs. 1435 11. The Manufacturer Usage Description LLDP extension 1437 The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop 1438 vendor-neutral link layer protocol used by end hosts network Things 1439 for advertising their identity, capabilities, and neighbors on an 1440 IEEE 802 local area network. Its Type-Length-Value (TLV) design 1441 allows for 'vendor-specific' extensions to be defined. IANA has a 1442 registered IEEE 802 organizationally unique identifier (OUI) defined 1443 as documented in [RFC7042]. The MUD LLDP extension uses a subtype 1444 defined in this document to carry the MUD URL. 1446 The LLDP vendor specific frame has the following format: 1448 +--------+--------+----------+---------+-------------- 1449 |TLV Type| len | OUI |subtype | MUD URL 1450 | =127 | |= 00 00 5E| = 1 | 1451 |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets) 1452 +--------+--------+----------+---------+-------------- 1454 where: 1456 o TLV Type = 127 indicates a vendor-specific TLV 1458 o len - indicates the TLV string length 1460 o OUI = 00 00 5E is the organizationally unique identifier of IANA 1462 o subtype = 1 (to be assigned by IANA for the MUD URL) 1464 o MUD URL - the length MUST NOT exceed 255 octets 1466 The intent of this extension is to provide both a new Thing 1467 classifier to the network as well as some recommended configuration 1468 to the routers that implement policy. However, it is entirely the 1469 purview of the network system as managed by the network administrator 1470 to decide what to do with this information. The key function of this 1471 extension is simply to identify the type of Thing to the network in a 1472 structured way such that the policy can be easily found with existing 1473 toolsets. 1475 Hosts, routers, or other network elements that implement this option 1476 are intended to have at most one MUD URL associated with them, so 1477 they may transmit at most one MUD URL value. 1479 Hosts, routers, or other network elements that implement this option 1480 may ignore these options or take action based on receipt of these 1481 options. For example they may fill in information in the respective 1482 extensions of the LLDP Management Information Base (LLDP MIB). LLDP 1483 operates in a one-way direction. LLDPDUs are not exchanged as 1484 information requests by one Thing and response sent by another Thing. 1485 The other Things do not acknowledge LLDP information received from a 1486 Thing. No specific network behavior is guaranteed. When a Thing 1487 consumes this extension, it may either forward the URL and relevant 1488 remote Thing information to a MUD controller, or it will retrieve the 1489 usage description by resolving the URL in accordance with normal HTTP 1490 semantics. 1492 12. Creating and Processing of Signed MUD Files 1494 Because MUD files contain information that may be used to configure 1495 network access lists, they are sensitive. To insure that they have 1496 not been tampered with, it is important that they be signed. We make 1497 use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for 1498 this purpose. 1500 12.1. Creating a MUD file signature 1502 A MUD file MUST be signed using CMS as an opaque binary object. In 1503 order to make successful verification more likely, intermediate 1504 certificates SHOULD be included. The signature is stored at the same 1505 location as the MUD URL but with the suffix of ".p7s". Signatures 1506 are transferred using content-type "application/pkcs7-signature". 1508 For example: 1510 % openssl cms -sign -signer mancertfile -inkey mankey \ 1511 -in mudfile -binary -outform DER - \ 1512 -certfile intermediatecert -out mudfile.p7s 1514 Note: A MUD file may need to be re-signed if the signature expires. 1516 12.2. Verifying a MUD file signature 1518 Prior to retrieving a MUD file the MUD controller SHOULD retrieve the 1519 MUD signature file using the MUD URL with a suffix of ".p7s". For 1520 example, if the MUD URL is "https://example.com/.well-known/modela", 1521 the MUD signature URL will be "https://example.com/.well-known/ 1522 modela.p7s". 1524 Upon retrieving a MUD file, a MUD controller MUST validate the 1525 signature of the file before continuing with further processing. A 1526 MUD controller MUST cease processing of that file it cannot validate 1527 the chain of trust to a known trust anchor until an administrator has 1528 given approval. 1530 The purpose of the signature on the file is to assign accountability 1531 to an entity, whose reputation can be used to guide administrators on 1532 whether or not to accept a given MUD file. It is already common 1533 place to check web reputation on the location of a server on which a 1534 file resides. While it is likely that the manufacturer will be the 1535 signer of the file, this is not strictly necessary, and may not be 1536 desirable. For one thing, in some environments, integrators may 1537 install their own certificates. For another, what is more important 1538 is the accountability of the recommendation, and not the 1539 cryptographic relationship between the device and the file. 1541 An example: 1543 % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile 1545 Note the additional step of verifying the common trust root. 1547 13. Extensibility 1549 One of our design goals is to see that MUD files are able to be 1550 understood by as broad a cross-section of systems as is possible. 1551 Coupled with the fact that we have also chosen to leverage existing 1552 mechanisms, we are left with no ability to negotiate extensions and a 1553 limited desire for those extensions in any event. A such, a two-tier 1554 extensibility framework is employed, as follows: 1556 1. At a coarse grain, a protocol version is included in a MUD URL. 1557 This memo specifies MUD version 1. Any and all changes are 1558 entertained when this version is bumped. Transition approaches 1559 between versions would be a matter for discussion in future 1560 versions. 1562 2. At a finer grain, only extensions that would not incur additional 1563 risk to the Thing are permitted. Specifically, adding nodes to 1564 the mud container is permitted with the understanding that such 1565 additions will be ignored by unaware implementations. Any such 1566 extensions SHALL be standardized through the IETF process, and 1567 MUST be named in the "extensions" list. MUD controllers MUST 1568 ignore YANG nodes they do not understand and SHOULD create an 1569 exception to be resolved by an administrator, so as to avoid any 1570 policy inconsistencies. 1572 14. Deployment Considerations 1574 Because MUD consists of a number of architectural building blocks, it 1575 is possible to assemble different deployment scenarios. One key 1576 aspect is where to place policy enforcement. In order to protect the 1577 Thing from other Things within a local deployment, policy can be 1578 enforced on the nearest switch or access point. In order to limit 1579 unwanted traffic within a network, it may also be advisable to 1580 enforce policy as close to the Internet as possible. In some 1581 circumstances, policy enforcement may not be available at the closest 1582 hop. At that point, the risk of so-called east-west infection is 1583 increased to the number of Things that are able to communicate 1584 without protection. 1586 A caution about some of the classes: admission of a Thing into the 1587 "manufacturer" and "same-manufacturer" class may have impact on 1588 access of other Things. Put another way, the admission may grow the 1589 access-list on switches connected to other Things, depending on how 1590 access is managed. Some care should be given on managing that 1591 access-list growth. Alternative methods such as additional network 1592 segmentation can be used to keep that growth within reason. 1594 Because as of this writing MUD is a new concept, one can expect a 1595 great many devices to not have implemented it. It remains a local 1596 deployment decision as to whether a device that is first connected 1597 should be alloewed broad or limited access. Furthermore, as 1598 mentioned in the introduction, a deployment may choose to ignore a 1599 MUD policy in its entirety, but simply taken into account the MUD URL 1600 as a classifier to be used as part of a local policy decision. 1602 15. Security Considerations 1604 Based on how a MUD URL is emitted, a Thing may be able to lie about 1605 what it is, thus gaining additional network access. There are 1606 several means to limit risk in this case. The most obvious is to 1607 only believe Things that make use of certificate-based authentication 1608 such as IEEE 802.1AR certificates. When those certificates are not 1609 present, Things claiming to be of a certain manufacturer SHOULD NOT 1610 be included in that manufacturer grouping without additional 1611 validation of some form. This will occur when it makes use of 1612 primitives such as "manufacturer" for the purpose of accessing Things 1613 of a particular type. Similarly, network management systems may be 1614 able to fingerprint the Thing. In such cases, the MUD URL can act as 1615 a classifier that can be proven or disproven. Fingerprinting may 1616 have other advantages as well: when 802.1AR certificates are used, 1617 because they themselves cannot change, fingerprinting offers the 1618 opportunity to add artificats to the MUD URL. The meaning of such 1619 artifacts is left as future work. 1621 Network management systems SHOULD NOT accept a usage description for 1622 a Thing with the same MAC address that has indicated a change of 1623 authority without some additional validation (such as review by a 1624 network administrator). New Things that present some form of 1625 unauthenticated MUD URL SHOULD be validated by some external means 1626 when they would be otherwise be given increased network access. 1628 It may be possible for a rogue manufacturer to inappropriately 1629 exercise the MUD file parser, in order to exploit a vulnerability. 1630 There are three recommended approaches to address this threat. The 1631 first is to validate the signature of the MUD file. The second is to 1632 have a system do a primary scan of the file to ensure that it is both 1633 parseable and believable at some level. MUD files will likely be 1634 relatively small, to start with. The number of ACEs used by any 1635 given Thing should be relatively small as well. It may also be 1636 useful to limit retrieval of MUD URLs to only those sites that are 1637 known to have decent web or domain reputations. 1639 Use of a URL necessitates the use of domain names. If a domain name 1640 changes ownership, the new owner of that domain may be able to 1641 provide MUD files that MUD controllers would consider valid. There 1642 are a few approaches that can mitigate this attack. First, MUD 1643 controllers SHOULD cache certificates used by the MUD file server. 1644 When a new certificate is retrieved for whatever reason, the MUD 1645 controller should check to see if ownership of the domain has 1646 changed. A fair programmatic approximation of this is when the name 1647 servers for the domain have changed. If the actual MUD file has 1648 changed, the controller MAY check the WHOIS database to see if 1649 registration ownership of a domain has changed. If a change has 1650 occured, or if for some reason it is not possible to determine 1651 whether ownership has changed, further review may be warranted. 1652 Note, this remediation does not take into account the case of a Thing 1653 that was produced long ago and only recently fielded, or the case 1654 where a new MUD controller has been installed. 1656 It may not be possible for a MUD controller to retrieve a MUD file at 1657 any given time. Should a MUD controller fail to retrieve a MUD file, 1658 it SHOULD consider the existing one safe to use, at least for a time. 1659 After some period, it SHOULD log that it has been unable to retrieve 1660 the file. There may be very good reasons for such failures, 1661 including the possibility that the MUD controller is in an off-line 1662 environment, the local Internet connection has failed, or the remote 1663 Internet connection has failed. It is also possible that an attacker 1664 is attempting to prevent onboarding of a device. It is a local 1665 deployment decision as to whether or not devices may be onboarded in 1666 the face of such failures. 1668 The release of a MUD URL by a Thing reveals what the Thing is, and 1669 provides an attacker with guidance on what vulnerabilities may be 1670 present. 1672 While the MUD URL itself is not intended to be unique to a specific 1673 Thing, the release of the URL may aid an observer in identifying 1674 individuals when combined with other information. This is a privacy 1675 consideration. 1677 In addressing both of these concerns, implementors should take into 1678 account what other information they are advertising through 1679 mechanisms such as mDNS[RFC6872], how a Thing might otherwise be 1680 identified, perhaps through how it behaves when it is connected to 1681 the network, whether a Thing is intended to be used by individuals or 1682 carry personal identifying information, and then apply appropriate 1683 data minimization techniques. One approach is to make use of TEAP 1684 [RFC7170] as the means to share information with authorized 1685 components in the network. Network elements may also assist in 1686 limiting access to the MUD URL through the use of mechanisms such as 1687 DHCPv6-Shield [RFC7610]. 1689 Please note that the security considerations mentioned in Section 4.7 1690 of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case 1691 because the YANG serialization is not intended to be accessed via 1692 NETCONF. However, for those who try to instantiate this model in a 1693 network element via NETCONF, all objects in each model in this draft 1694 exhibit similar security characteristics as 1695 [I-D.ietf-netmod-acl-model]. The basic purpose of MUD is to 1696 configure access, and so by its very nature can be disruptive if used 1697 by unauthorized parties. 1699 16. IANA Considerations 1701 16.1. YANG Module Registrations 1703 The following YANG modules are requested to be registred in the "IANA 1704 Module Names" registry: 1706 The ietf-mud module: 1708 o Name: ietf-mud 1710 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud 1712 o Prefix: ief-mud 1714 o Reference: This memo 1716 The ietf-acldns module: 1718 o Name: ietf-acldns 1720 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns 1722 o Prefix: ietf-acldns 1724 o Reference: This memo 1726 16.2. DHCPv4 and DHCPv6 Options 1728 The IANA has allocated option 161 in the Dynamic Host Configuration 1729 Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry 1730 for the MUD DHCPv4 option, and option 112 for DHCPv6, as described in 1731 Section 9. 1733 16.3. PKIX Extensions 1735 IANA is kindly requested to make the following assignments for: 1737 o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for 1738 PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). 1740 o id-pe-mud-url object identifier from the "SMI Security for PKIX 1741 Certificate Extension" registry (1.3.6.1.5.5.7.1). 1743 The use of these values is specified in Section 10. 1745 16.4. Well Known URI Suffix 1747 The IANA has allocated the URL suffix of "mud" as follows: 1749 o URI Suffix: "mud" o Specification documents: this document o 1750 Related information: n/a 1752 16.5. MIME Media-type Registration for MUD files 1754 The following media-type is defined for transfer of MUD file: 1756 o Type name: application 1757 o Subtype name: mud+json 1758 o Required parameters: n/a 1759 o Optional parameters: n/a 1760 o Encoding considerations: 8bit; application/mud+json values 1761 are represented as a JSON object; UTF-8 encoding SHOULD be 1762 employed. 1763 o Security considerations: See Security Considerations 1764 of this document. 1765 o Interoperability considerations: n/a 1766 o Published specification: this document 1767 o Applications that use this media type: MUD controllers as 1768 specified by this document. 1769 o Fragment identifier considerations: n/a 1770 o Additional information: 1772 Magic number(s): n/a 1773 File extension(s): n/a 1774 Macintosh file type code(s): n/a 1776 o Person & email address to contact for further information: 1777 Eliot Lear , Ralph Droms 1778 o Intended usage: COMMON 1779 o Restrictions on usage: none 1780 o Author: 1781 Eliot Lear 1782 Ralph Droms 1783 o Change controller: IESG 1784 o Provisional registration? (standards tree only): No. 1786 16.6. LLDP IANA TLV Subtype Registry 1788 IANA is requested to create a new registry for IANA Link Layer 1789 Discovery Protocol (LLDP) TLV subtype values. The recommended policy 1790 for this registry is Expert Review. The maximum number of entries in 1791 the registry is 256. 1793 IANA is required to populate the initial registry with the value: 1795 LLDP subtype value = 1 (All the other 255 values should be initially 1796 marked as 'Unassigned'.) 1798 Description = the Manufacturer Usage Description (MUD) Uniform 1799 Resource Locator (URL) 1801 Reference = < this document > 1803 16.7. The MUD Well Known Universal Resource Name (URNs) 1805 The following parameter registry is requested to be added in 1806 accordance with [RFC3553] 1808 Registry name: "urn:ietf:params:mud" is requested. 1809 Specification: this document 1810 Repository: this document 1811 Index value: Encoded identically to a TCP/UDP port service 1812 name, as specified in Section 5.1 of [RFC6335] 1814 The following entries should be added to the "urn:ietf:params:mud" 1815 name space: 1817 "urn:ietf:params:mud:dns" refers to the service specified by 1818 [RFC1123]. "urn:ietf:params:mud:ntp" refers to the service specified 1819 by [RFC5905]. 1821 16.8. Extensions Registry 1823 The IANA is requested to establish a registry of extensions as 1824 follows: 1826 Registry name: MUD extensions registry 1827 Registry policy: Standards action 1828 Standard reference: document 1829 Extension name: UTF-8 encoded string, not to exceed 40 characters. 1831 Each extension MUST follow the rules specified in this specification. 1832 As is usual, the IANA issues early allocations based in accordance 1833 with [RFC7120]. 1835 17. Acknowledgments 1837 The authors would like to thank Einar Nilsen-Nygaard, who 1838 singlehandedly updated the model to match the updated ACL model, 1839 Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm, 1840 John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk 1841 Birkholz, Adam Montville, and Robert Sparks for their valuable advice 1842 and reviews. Russ Housley entirely rewrote Section 10 to be a 1843 complete module. Adrian Farrel provided the basis for privacy 1844 considerations text. Kent Watsen provided a thorough review of the 1845 architecture and the YANG model. The remaining errors in this work 1846 are entirely the responsibility of the authors. 1848 18. References 1850 18.1. Normative References 1852 [I-D.ietf-netmod-acl-model] 1853 Jethanandani, M., Huang, L., Agarwal, S., and D. Blair, 1854 "Network Access Control List (ACL) YANG Data Model", 1855 draft-ietf-netmod-acl-model-15 (work in progress), January 1856 2018. 1858 [I-D.ietf-netmod-yang-tree-diagrams] 1859 Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft- 1860 ietf-netmod-yang-tree-diagrams-05 (work in progress), 1861 January 2018. 1863 [IEEE8021AB] 1864 Institute for Electrical and Electronics Engineers, "IEEE 1865 Standard for Local and Metropolitan Area Networks-- 1866 Station and Media Access Control Connectivity Discovery", 1867 n.d.. 1869 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1870 Application and Support", STD 3, RFC 1123, 1871 DOI 10.17487/RFC1123, October 1989, 1872 . 1874 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1875 Requirement Levels", BCP 14, RFC 2119, 1876 DOI 10.17487/RFC2119, March 1997, 1877 . 1879 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1880 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1881 . 1883 [RFC2618] Aboba, B. and G. Zorn, "RADIUS Authentication Client MIB", 1884 RFC 2618, DOI 10.17487/RFC2618, June 1999, 1885 . 1887 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1888 DOI 10.17487/RFC2818, May 2000, 1889 . 1891 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1892 C., and M. Carney, "Dynamic Host Configuration Protocol 1893 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1894 2003, . 1896 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1897 Levkowetz, Ed., "Extensible Authentication Protocol 1898 (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, 1899 . 1901 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1902 Resource Identifier (URI): Generic Syntax", STD 66, 1903 RFC 3986, DOI 10.17487/RFC3986, January 2005, 1904 . 1906 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1907 Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, 1908 January 2005, . 1910 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1911 Housley, R., and W. Polk, "Internet X.509 Public Key 1912 Infrastructure Certificate and Certificate Revocation List 1913 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1914 . 1916 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, 1917 RFC 5652, DOI 10.17487/RFC5652, September 2009, 1918 . 1920 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1921 "Network Time Protocol Version 4: Protocol and Algorithms 1922 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1923 . 1925 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1926 Cheshire, "Internet Assigned Numbers Authority (IANA) 1927 Procedures for the Management of the Service Name and 1928 Transport Protocol Port Number Registry", BCP 165, 1929 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1930 . 1932 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 1933 RFC 6991, DOI 10.17487/RFC6991, July 2013, 1934 . 1936 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 1937 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 1938 2014, . 1940 [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 1941 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 1942 BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, 1943 . 1945 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1946 Protocol (HTTP/1.1): Message Syntax and Routing", 1947 RFC 7230, DOI 10.17487/RFC7230, June 2014, 1948 . 1950 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1951 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1952 DOI 10.17487/RFC7231, June 2014, 1953 . 1955 [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield: 1956 Protecting against Rogue DHCPv6 Servers", BCP 199, 1957 RFC 7610, DOI 10.17487/RFC7610, August 2015, 1958 . 1960 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 1961 RFC 7950, DOI 10.17487/RFC7950, August 2016, 1962 . 1964 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 1965 RFC 7951, DOI 10.17487/RFC7951, August 2016, 1966 . 1968 18.2. Informative References 1970 [FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls", 1971 January 1995. 1973 [I-D.ietf-netmod-rfc6087bis] 1974 Bierman, A., "Guidelines for Authors and Reviewers of YANG 1975 Data Model Documents", draft-ietf-netmod-rfc6087bis-16 1976 (work in progress), January 2018. 1978 [IEEE8021AR] 1979 Institute for Electrical and Electronics Engineers, 1980 "Secure Device Identity", 1998. 1982 [ISO.8601.1988] 1983 International Organization for Standardization, "Data 1984 elements and interchange formats - Information interchange 1985 - Representation of dates and times", ISO Standard 8601, 1986 June 1988. 1988 [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic 1989 Technology and the Internet", BCP 200, RFC 1984, 1990 DOI 10.17487/RFC1984, August 1996, 1991 . 1993 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 1994 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 1995 . 1997 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 1998 IETF URN Sub-namespace for Registered Protocol 1999 Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June 2000 2003, . 2002 [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security 2003 Capabilities in Customer Premises Equipment (CPE) for 2004 Providing Residential IPv6 Internet Service", RFC 6092, 2005 DOI 10.17487/RFC6092, January 2011, 2006 . 2008 [RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur, 2009 H., and O. Festor, "The Common Log Format (CLF) for the 2010 Session Initiation Protocol (SIP): Framework and 2011 Information Model", RFC 6872, DOI 10.17487/RFC6872, 2012 February 2013, . 2014 [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and 2015 IETF Protocol and Documentation Usage for IEEE 802 2016 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, 2017 October 2013, . 2019 [RFC7170] Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, 2020 "Tunnel Extensible Authentication Protocol (TEAP) Version 2021 1", RFC 7170, DOI 10.17487/RFC7170, May 2014, 2022 . 2024 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 2025 Application Protocol (CoAP)", RFC 7252, 2026 DOI 10.17487/RFC7252, June 2014, 2027 . 2029 [RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson, 2030 "Architectural Considerations in Smart Object Networking", 2031 RFC 7452, DOI 10.17487/RFC7452, March 2015, 2032 . 2034 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 2035 Reddy, "Port Control Protocol (PCP) Server Selection", 2036 RFC 7488, DOI 10.17487/RFC7488, March 2015, 2037 . 2039 Appendix A. Changes from Earlier Versions 2041 RFC Editor to remove this section prior to publication. 2043 Draft -13 to -14: 2045 o Final WGLC comments and review comments 2047 o Move version from MUD-URL to Model 2049 o Have MUD-URL in model 2051 o Update based on update to draft-ietf-netmod-acl-model 2053 o Point to tree diagram draft instead of 6087bis. 2055 Draft -12 to -13: 2057 o Additional WGLC comments 2059 Draft -10 to -12: 2061 These are based on WGLC comments: 2063 o Correct examples based on ACL model changes. 2065 o Change ordering nodes. 2067 o Additional explanatory text around systeminfo. 2069 o Change ordering in examples. 2071 o Make it VERY VERY VERY VERY clear that these are recommendations, 2072 not mandates. 2074 o DHCP -> NTP in some of the intro text. 2076 o Remove masa-server 2078 o "Things" to "network elements" in a few key places. 2080 o Reference to JSON YANG RFC added. 2082 Draft -10 to -11: 2084 o Example corrections 2086 o Typo 2087 o Fix two lists. 2089 o Addition of 'any-acl' and 'mud-acl' in the list of allowed 2090 features. 2092 o Clarification of what should be in a MUD file. 2094 Draft -09 to -10: 2096 o AD input. 2098 o Correct dates. 2100 o Add compliance sentence as to which ACL module features are 2101 implemented. 2103 Draft -08 to -09: 2105 o Resolution of Security Area review, IoT directorate review, GenART 2106 review, YANG doctors review. 2108 o change of YANG structure to address mandatory nodes. 2110 o Terminology cleanup. 2112 o specify out extra portion of MUD-URL. 2114 o consistency changes. 2116 o improved YANG descriptions. 2118 o Remove extra revisions. 2120 o Track ACL model changes. 2122 o Additional cautions on use of ACL model; further clarifications on 2123 extensions. 2125 Draft -07 to -08: 2127 o a number of editorials corrected. 2129 o definition of MUD file tweaked. 2131 Draft -06 to -07: 2133 o Examples updated. 2135 o Additional clarification for direction-initiated. 2137 o Additional implementation guidance given. 2139 Draft -06 to -07: 2141 o Update models to match new ACL model 2143 o extract directionality from the ACL, introducing a new device 2144 container. 2146 Draft -05 to -06: 2148 o Make clear that this is a component architecture (Polk and Watson) 2150 o Add order of operations (Watson) 2152 o Add extensions leaf-list (Pritikin) 2154 o Remove previous-mud-file (Watson) 2156 o Modify text in last-update (Watson) 2158 o Clarify local networks (Weis, Watson) 2160 o Fix contact info (Watson) 2162 o Terminology clarification (Weis) 2164 o Advice on how to handle LDevIDs (Watson) 2166 o Add deployment considerations (Watson) 2168 o Add some additional text about fingerprinting (Watson) 2170 o Appropriate references to 6087bis (Watson) 2172 o Change systeminfo to a URL to be referenced (Lear) 2174 Draft -04 to -05: * syntax error correction 2176 Draft -03 to -04: * Re-add my-controller 2178 Draft -02 to -03: * Additional IANA updates * Format correction in 2179 YANG. * Add reference to TEAP. 2181 Draft -01 to -02: * Update IANA considerations * Accept Russ Housley 2182 rewrite of X.509 text * Include privacy considerations text * Redo 2183 the URL limit. Still 255 bytes, but now stated in the URL 2184 definition. * Change URI registration to be under urn:ietf:params 2186 Draft -00 to -01: * Fix cert trust text. * change supportInformation 2187 to meta-info * Add an informational element in. * add urn registry 2188 and create first entry * add default elements 2190 Appendix B. Default MUD nodes 2192 What follows is the portion of a MUD file that permits DNS traffic to 2193 a controller that is registered with the URN 2194 "urn:ietf:params:mud:dns" and traffic NTP to a controller that is 2195 registered "urn:ietf:params:mud:ntp". This is considered the default 2196 behavior and the ACEs are in effect appended to whatever other "ace" 2197 entries that a MUD file contains. To block DNS or NTP one repeats 2198 the matching statement but replaces the "forwarding" action "accept" 2199 with "drop". Because ACEs are processed in the order they are 2200 received, the defaults would not be reached. A MUD controller might 2201 further decide to optimize to simply not include the defaults when 2202 they are overriden. 2204 Four of "acl" liste entries that implement default MUD nodes is 2205 listed below. Two are for IPv4 and two are for IPv6 (one in each 2206 direction for both versions of IP). 2208 "ietf-access-control-list:access-lists": { 2209 "acl": [ 2210 { 2211 "name": "mud-63142-v4to", 2212 "acl-type": "ipv4-acl-type", 2213 "aces": { 2214 "ace": [ 2215 { 2216 "rule-name": "ent0-todev", 2217 "matches": { 2218 "ietf-mud:mud-acl": { 2219 "controller": "urn:ietf:params:mud:dns" 2220 }, 2221 "ipv4": { 2222 "protocol": 17, 2223 "source-port-range-or-operator": { 2224 "operator": "eq", 2225 "port": 53 2226 } 2227 } 2228 }, 2229 "actions": { 2230 "forwarding": "accept" 2232 } 2233 }, 2234 { 2235 "rule-name": "ent1-todev", 2236 "matches": { 2237 "ietf-mud:mud-acl": { 2238 "controller": "urn:ietf:params:mud:ntp" 2239 }, 2240 "ipv4": { 2241 "protocol": 17, 2242 "source-port-range-or-operator": { 2243 "operator": "eq", 2244 "port": 123 2245 } 2246 } 2247 }, 2248 "actions": { 2249 "forwarding": "accept" 2250 } 2251 } 2252 ] 2253 } 2254 }, 2255 { 2256 "name": "mud-63142-v4fr", 2257 "acl-type": "ipv4-acl-type", 2258 "aces": { 2259 "ace": [ 2260 { 2261 "rule-name": "ent0-frdev", 2262 "matches": { 2263 "ietf-mud:mud-acl": { 2264 "controller": "urn:ietf:params:mud:dns" 2265 }, 2266 "ipv4": { 2267 "protocol": 17, 2268 "destination-port-range-or-operator": { 2269 "operator": "eq", 2270 "port": 53 2271 } 2272 } 2273 }, 2274 "actions": { 2275 "forwarding": "accept" 2276 } 2277 }, 2278 { 2279 "rule-name": "ent1-frdev", 2280 "matches": { 2281 "ietf-mud:mud-acl": { 2282 "controller": "urn:ietf:params:mud:ntp" 2283 }, 2284 "ipv4": { 2285 "protocol": 17, 2286 "destination-port-range-or-operator": { 2287 "operator": "eq", 2288 "port": 123 2289 } 2290 } 2291 }, 2292 "actions": { 2293 "forwarding": "accept" 2294 } 2295 } 2296 ] 2297 } 2298 }, 2299 { 2300 "name": "mud-63142-v6to", 2301 "acl-type": "ipv6-acl-type", 2302 "access-list-entries": { 2303 "ace": [ 2304 { 2305 "rule-name": "ent0-todev", 2306 "matches": { 2307 "ietf-mud:mud-acl": { 2308 "controller": "urn:ietf:params:mud:dns" 2309 }, 2310 "ipv6": { 2311 "protocol": 17, 2312 "source-port-range-or-operator": { 2313 "operator": "eq", 2314 "port": 53 2315 } 2316 } 2317 }, 2318 "actions": { 2319 "forwarding": "accept" 2320 } 2321 }, 2322 { 2323 "rule-name": "ent1-todev", 2324 "matches": { 2325 "ietf-mud:mud-acl": { 2326 "controller": "urn:ietf:params:mud:ntp" 2327 }, 2328 "ipv6": { 2329 "protocol": 17, 2330 "source-port-range-or-operator": { 2331 "operator": "eq", 2332 "port": 123 2333 } 2334 } 2335 }, 2336 "actions": { 2337 "forwarding": "accept" 2338 } 2339 } 2340 ] 2341 } 2342 }, 2343 { 2344 "name": "mud-63142-v6fr", 2345 "acl-type": "ipv6-acl-type", 2346 "access-list-entries": { 2347 "ace": [ 2348 { 2349 "rule-name": "ent0-frdev", 2350 "matches": { 2351 "ietf-mud:mud-acl": { 2352 "controller": "urn:ietf:params:mud:dns" 2353 }, 2354 "ipv6": { 2355 "protocol": 17, 2356 "destination-port-range-or-operator": { 2357 "operator": "eq", 2358 "port": 53 2359 } 2360 } 2361 }, 2362 "actions": { 2363 "forwarding": "accept" 2364 } 2365 }, 2366 { 2367 "rule-name": "ent1-frdev", 2368 "matches": { 2369 "ietf-mud:mud-acl": { 2370 "controller": "urn:ietf:params:mud:ntp" 2371 }, 2372 "ipv6": { 2373 "protocol": 17, 2374 "destination-port-range-or-operator": { 2375 "operator": "eq", 2376 "port": 123 2377 } 2378 } 2379 }, 2380 "actions": { 2381 "forwarding": "accept" 2382 } 2383 } 2384 ] 2385 } 2386 } 2387 ] 2388 } 2390 Appendix C. A Sample Extension: DETNET-indicator 2392 In this sample extension we augment the core MUD model to indicate 2393 whether the device implements DETNET. If a device later attempts to 2394 make use of DETNET, an notification or exception might be generated. 2395 Note that this example is intended only for illustrative purposes. 2397 Extension Name: "Example-Extension" (to be used in the extensions list) 2398 Standard: this document (but do not register the example) 2400 This extension augments the MUD model to include a single node, using 2401 the following sample module that has the following tree structure: 2403 module: ietf-mud-detext-example 2404 augment /ietf-mud:mud: 2405 +--rw is-detnet-required? boolean 2407 The model is defined as follows: 2409 file "ietf-mud-detext-example@2018-01-24.yang" 2410 module ietf-mud-detext-example { 2411 yang-version 1.1; 2412 namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example"; 2413 prefix ietf-mud-detext-example; 2415 import ietf-mud { 2416 prefix ietf-mud; 2417 } 2419 organization 2420 "IETF OPSAWG (Ops Area) Working Group"; 2422 contact 2423 "WG Web: http://tools.ietf.org/wg/opsawg/ 2424 WG List: opsawg@ietf.org 2425 Author: Eliot Lear 2426 lear@cisco.com 2427 Author: Ralph Droms 2428 rdroms@gmail.com 2429 Author: Dan Romascanu 2430 dromasca@gmail.com 2432 "; 2433 description 2434 "Sample extension to a MUD module to indicate a need 2435 for DETNET support."; 2437 revision 2018-01-24 { 2438 description 2439 "Initial revision."; 2440 reference 2441 "RFC XXXX: Manufacturer Usage Description 2442 Specification"; 2443 } 2445 augment "/ietf-mud:mud" { 2446 description 2447 "This adds a simple extension for a manufacturer 2448 to indicate whether DETNET is required by a 2449 device."; 2450 leaf is-detnet-required { 2451 type boolean; 2452 description 2453 "This value will equal true if a device requires 2454 detnet to properly function"; 2455 } 2456 } 2457 } 2458 2460 Using the previous example, we now show how the extension would be 2461 expressed: 2463 { 2465 { 2466 "ietf-mud:mud": { 2467 "mud-version": 1, 2468 "mud-url": "https://bms.example.com/.well-known/mud/lightbulb2000", 2469 "last-update": "2018-01-23T13:33:52+01:00", 2470 "cache-validity": 48, 2471 "is-supported": true, 2472 "systeminfo": "The BMS Example Lightbulb", 2473 "extensions": [ 2474 "ietf-mud-detext-example" 2475 ], 2476 "ietf-mud-detext-example:is-detnet-required": "false", 2477 "from-device-policy": { 2478 "access-lists": { 2479 "access-list": [ 2480 { 2481 "name": "mud-45782-v6fr" 2482 } 2483 ] 2484 } 2485 }, 2486 "to-device-policy": { 2487 "access-lists": { 2488 "access-list": [ 2489 { 2490 "name": "mud-45782-v6to" 2491 } 2492 ] 2493 } 2494 } 2495 }, 2496 "ietf-access-control-list:access-lists": { 2497 "acl": [ 2498 { 2499 "name": "mud-45782-v6to", 2500 "acl-type": "ipv6-acl-type", 2501 "access-list-entries": { 2502 "ace": [ 2503 { 2504 "rule-name": "cl0-todev", 2505 "matches": { 2506 "ipv6-acl": { 2507 "ietf-acldns:src-dnsname": "service.bms.example.com", 2508 "protocol": 6, 2509 "source-port-range-or-operator": { 2510 "operator": "eq", 2511 "port": 443 2512 } 2513 }, 2514 "tcp": { 2515 "ietf-mud:direction-initiated": "from-device" 2516 } 2517 }, 2518 "actions": { 2519 "forwarding": "accept" 2520 } 2521 } 2522 ] 2523 } 2524 }, 2525 { 2526 "name": "mud-45782-v6fr", 2527 "acl-type": "ipv6-acl-type", 2528 "access-list-entries": { 2529 "ace": [ 2530 { 2531 "rule-name": "cl0-frdev", 2532 "matches": { 2533 "ipv6-acl": { 2534 "ietf-acldns:dst-dnsname": "service.bms.example.com", 2535 "protocol": 6, 2536 "destination-port-range-or-operator": { 2537 "operator": "eq", 2538 "port": 443 2539 } 2540 }, 2541 "tcp": { 2542 "ietf-mud:direction-initiated": "from-device" 2543 } 2544 }, 2545 "actions": { 2546 "forwarding": "accept" 2547 } 2548 } 2549 ] 2550 } 2551 } 2552 ] 2553 } 2554 } 2556 Authors' Addresses 2557 Eliot Lear 2558 Cisco Systems 2559 Richtistrasse 7 2560 Wallisellen CH-8304 2561 Switzerland 2563 Phone: +41 44 878 9200 2564 Email: lear@cisco.com 2566 Ralph Droms 2568 Phone: +1 978 376 3731 2569 Email: rdroms@gmail.com 2571 Dan Romascanu 2573 Phone: +972 54 5555347 2574 Email: dromasca@gmail.com