idnits 2.17.1 draft-ietf-opsawg-mud-20.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 1066 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 (April 09, 2018) is 2202 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-21) exists of draft-ietf-netmod-acl-model-18 -- Possible downref: Non-RFC (?)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) -- Obsolete informational reference (is this intentional?): RFC 7042 (Obsoleted by RFC 9542) -- Obsolete informational reference (is this intentional?): RFC 7223 (Obsoleted by RFC 8343) Summary: 5 errors (**), 0 flaws (~~), 4 warnings (==), 4 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: October 11, 2018 Google 6 D. Romascanu 7 April 09, 2018 9 Manufacturer Usage Description Specification 10 draft-ietf-opsawg-mud-20 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, an X.509 certificate extension and a means to sign 22 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 October 11, 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 . . . . . . . . . . . . . . . . 13 70 3. Data Node Definitions . . . . . . . . . . . . . . . . . . . . 14 71 3.1. mud-version . . . . . . . . . . . . . . . . . . . . . . . 14 72 3.2. to-device-policy and from-device-policy containers . . . 15 73 3.3. last-update . . . . . . . . . . . . . . . . . . . . . . . 15 74 3.4. cache-validity . . . . . . . . . . . . . . . . . . . . . 15 75 3.5. is-supported . . . . . . . . . . . . . . . . . . . . . . 15 76 3.6. systeminfo . . . . . . . . . . . . . . . . . . . . . . . 15 77 3.7. mfg-name, software-rev, model-name firmware-rev . . . . . 16 78 3.8. extensions . . . . . . . . . . . . . . . . . . . . . . . 16 79 3.9. manufacturer . . . . . . . . . . . . . . . . . . . . . . 16 80 3.10. same-manufacturer . . . . . . . . . . . . . . . . . . . . 16 81 3.11. model . . . . . . . . . . . . . . . . . . . . . . . . . . 16 82 3.12. local-networks . . . . . . . . . . . . . . . . . . . . . 17 83 3.13. controller . . . . . . . . . . . . . . . . . . . . . . . 17 84 3.14. my-controller . . . . . . . . . . . . . . . . . . . . . . 17 85 3.15. direction-initiated . . . . . . . . . . . . . . . . . . . 17 86 4. Processing of the MUD file . . . . . . . . . . . . . . . . . 18 87 5. What does a MUD URL look like? . . . . . . . . . . . . . . . 18 88 6. The MUD YANG Model . . . . . . . . . . . . . . . . . . . . . 18 89 7. The Domain Name Extension to the ACL Model . . . . . . . . . 25 90 7.1. src-dnsname . . . . . . . . . . . . . . . . . . . . . . . 25 91 7.2. dst-dnsname . . . . . . . . . . . . . . . . . . . . . . . 25 92 7.3. The ietf-acldns Model . . . . . . . . . . . . . . . . . . 26 93 8. MUD File Example . . . . . . . . . . . . . . . . . . . . . . 27 94 9. The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . . 29 95 9.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 30 96 9.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 31 97 9.3. Relay Requirements . . . . . . . . . . . . . . . . . . . 31 98 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 31 99 11. The Manufacturer Usage Description LLDP extension . . . . . . 33 100 12. Creating and Processing of Signed MUD Files . . . . . . . . . 34 101 12.1. Creating a MUD file signature . . . . . . . . . . . . . 34 102 12.2. Verifying a MUD file signature . . . . . . . . . . . . . 34 103 13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 35 104 14. Deployment Considerations . . . . . . . . . . . . . . . . . . 35 105 15. Security Considerations . . . . . . . . . . . . . . . . . . . 36 106 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 107 16.1. YANG Module Registrations . . . . . . . . . . . . . . . 38 108 16.2. DHCPv4 and DHCPv6 Options . . . . . . . . . . . . . . . 39 109 16.3. PKIX Extensions . . . . . . . . . . . . . . . . . . . . 39 110 16.4. MIME Media-type Registration for MUD files . . . . . . . 39 111 16.5. LLDP IANA TLV Subtype Registry . . . . . . . . . . . . . 40 112 16.6. The MUD Well Known Universal Resource Name (URNs) . . . 41 113 16.7. Extensions Registry . . . . . . . . . . . . . . . . . . 41 114 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41 115 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 116 18.1. Normative References . . . . . . . . . . . . . . . . . . 42 117 18.2. Informative References . . . . . . . . . . . . . . . . . 44 118 Appendix A. Changes from Earlier Versions . . . . . . . . . . . 46 119 Appendix B. Default MUD nodes . . . . . . . . . . . . . . . . . 50 120 Appendix C. A Sample Extension: DETNET-indicator . . . . . . . . 54 121 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 58 123 1. Introduction 125 The Internet has largely been constructed for general purpose 126 computers, those devices that may be used for a purpose that is 127 specified by those who own the device. [RFC1984] presumed that an 128 end device would be most capable of protecting itself. This made 129 sense when the typical device was a workstation or a mainframe, and 130 it continues to make sense for general purpose computing devices 131 today, including laptops, smart phones, and tablets. 133 [RFC7452] discusses design patterns for, and poses questions about, 134 smart objects. Let us then posit a group of objects that are 135 specifically not general purpose computers. These devices, which 136 this memo refers to as Things, have a specific purpose. By 137 definition, therefore, all other uses are not intended. The 138 combination of these two statements can be restated as a manufacturer 139 usage description (MUD) that can be applied at various points within 140 a network. 142 We use the notion of "manufacturer" loosely in this context to refer 143 to the entity or organization that will state how a device is 144 intended to be used. For example, in the context of a lightbulb, 145 this might indeed be the lightbulb manufacturer. In the context of a 146 smarter device that has a built in Linux stack, it might be an 147 integrator of that device. The key points are that the device itself 148 is assumed to serve a limited purpose, and that there may exist an 149 organization in the supply chain of that device that will take 150 responsibility for informing the network about that purpose. 152 The intent of MUD is to provide the following: 154 o Substantially reduce the threat surface on a device entering a 155 network to those communications intended by the manufacturer. 157 o Provide a means to scale network policies to the ever-increasing 158 number of types of devices in the network. 160 o Provide a means to address at least some vulnerabilities in a way 161 that is faster than the time it might take to update systems. 162 This will be particularly true for systems that are no longer 163 supported by their manufacturer. 165 o Keep the cost of implementation of such a system to the bare 166 minimum. 168 o Provide a means of extensibility for manufacturers to express 169 other device capabilities or requirements. 171 MUD consists of three architectural building blocks: 173 o A URL that is can be used to locate a description; 175 o The description itself, including how it is interpreted, and; 177 o A means for local network management systems to retrieve the 178 description. 180 In this specification we describe each of these building blocks and 181 how they are intended to be used together. However, they may also be 182 used separately, independent of this specification, by local 183 deployments for their own purposes. 185 1.1. What MUD Doesn't Do 187 MUD is not intended to address network authorization of general 188 purpose computers, as their manufacturers cannot envision a specific 189 communication pattern to describe. In addition, even those devices 190 that have a single or small number of uses might have very broad 191 communication patterns. MUD on its own is not for them either. 193 Although MUD can provide network administrators with some additional 194 protection when device vulnerabilities exist, it will never replace 195 the need for manufacturers to patch vulnerabilities. 197 Finally, no matter what the manufacturer specifies in a MUD file, 198 these are not directives, but suggestions. How they are instantiated 199 locally will depend on many factors and will be ultimately up to the 200 local network administrator, who must decide what is appropriate in a 201 given circumstances. 203 1.2. A Simple Example 205 A light bulb is intended to light a room. It may be remotely 206 controlled through the network, and it may make use of a rendezvous 207 service of some form that an application on a smart phone. What we 208 can say about that light bulb, then, is that all other network access 209 is unwanted. It will not contact a news service, nor speak to the 210 refrigerator, and it has no need of a printer or other devices. It 211 has no social networking friends. Therefore, an access list applied 212 to it that states that it will only connect to the single rendezvous 213 service will not impede the light bulb in performing its function, 214 while at the same time allowing the network to provide both it and 215 other devices an additional layer of protection. 217 1.3. Terminology 219 MUD: manufacturer usage description. 221 MUD file: a file containing YANG-based JSON that describes a Thing 222 and associated suggested specific network behavior. 224 MUD file server: a web server that hosts a MUD file. 226 MUD controller: the system that requests and receives the MUD file 227 from the MUD server. After it has processed a MUD file, it may 228 direct changes to relevant network elements. 230 MUD URL: a URL that can be used by the MUD controller to receive the 231 MUD file. 233 Thing: the device emitting a MUD URL. 235 Manufacturer: the entity that configures the Thing to emit the MUD 236 URL and the one who asserts a recommendation in a MUD file. The 237 manufacturer might not always be the entity that constructs a 238 Thing. It could, for instance, be a systems integrator, or even a 239 component provider. 241 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 242 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 243 document are to be interpreted as described in [RFC2119]. 245 1.4. Determining Intended Use 247 The notion of intended use is in itself not new. Network 248 administrators apply access lists every day to allow for only such 249 use. This notion of white listing was well described by Chapman and 250 Zwicky in [FW95]. Profiling systems that make use of heuristics to 251 identify types of systems have existed for years as well. 253 A Thing could just as easily tell the network what sort of access it 254 requires without going into what sort of system it is. This would, 255 in effect, be the converse of [RFC7488]. In seeking a general 256 purpose solution, however, we assume that a device has so few 257 capabilities that it will implement the least necessary capabilities 258 to function properly. This is a basic economic constraint. Unless 259 the network would refuse access to such a device, its developers 260 would have no reason to provide the network any information. To 261 date, such an assertion has held true. 263 1.5. Finding A Policy: The MUD URL 265 Our work begins with the device emitting a Universal Resource Locator 266 (URL) [RFC3986]. This URL serves both to classify the device type 267 and to provide a means to locate a policy file. 269 MUD URLs MUST use the HTTPS scheme [RFC7230]. 271 In this memo three means are defined to emit the MUD URL, as follows: 273 o A DHCP option[RFC2131],[RFC3315] that the DHCP client uses to 274 inform the DHCP server. The DHCP server may take further actions, 275 such as retrieve the URL or otherwise pass it along to network 276 management system or controller. 278 o An X.509 constraint. The IEEE has developed [IEEE8021AR] that 279 provides a certificate-based approach to communicate device 280 characteristics, which itself relies on [RFC5280]. The MUD URL 281 extension is non-critical, as required by IEEE 802.1AR. Various 282 means may be used to communicate that certificate, including 283 Tunnel Extensible Authentication Protocol (TEAP) [RFC7170]. 285 o Finally, a Link Layer Discovery Protocol (LLDP) frame is defined 286 [IEEE8021AB]. 288 It is possible that there may be other means for a MUD URL to be 289 learned by a network. For instance, some devices may already be 290 fielded or have very limited ability to communicate a MUD URL, and 291 yet can be identified through some means, such as a serial number or 292 a public key. In these cases, manufacturers may be able to map those 293 identifiers to particular MUD URLs (or even the files themselves). 294 Similarly, there may be alternative resolution mechanisms available 295 for situations where Internet connectivity is limited or does not 296 exist. Such mechanisms are not described in this memo, but are 297 possible. Implementors should allow for this sort of flexibility of 298 how MUD URLs may be learned. 300 1.6. Processing of the MUD URL 302 MUD controllers that are able to do so SHOULD retrieve MUD URLs and 303 signature files as per [RFC7230], using the GET method [RFC7231]. 304 They MUST validate the certificate using the rules in [RFC2618], 305 Section 3.1. 307 Requests for MUD URLs SHOULD include an "Accept" header ([RFC7231], 308 Section 5.3.2) containing "application/mud+json", an "Accept- 309 Language" header ([RFC7231], Section 5.3.5), and a "User-Agent" 310 header ([RFC7231], Section 5.5.3). 312 MUD controllers SHOULD automatically process 3xx response status 313 codes. 315 If a MUD controller is not able to fetch a MUD URL, other means MAY 316 be used to import MUD files and associated signature files. So long 317 as the signature of the file can be validated, the file can be used. 318 In such environments, controllers SHOULD warn administrators when 319 cache-validity expiry is approaching so that they may check for new 320 files. 322 1.7. Types of Policies 324 When the MUD URL is resolved, the MUD controller retrieves a file 325 that describes what sort of communications a device is designed to 326 have. The manufacturer may specify either specific hosts for cloud 327 based services or certain classes for access within an operational 328 network. An example of a class might be "devices of a specified 329 manufacturer type", where the manufacturer type itself is indicated 330 simply by the authority component (e.g, the domain name) of the MUD 331 URL. Another example might be to allow or disallow local access. 332 Just like other policies, these may be combined. For example: 334 o Allow access to devices of the same manufacturer 335 o Allow access to and from controllers via Constrained Application 336 Protocol (COAP)[RFC7252] 338 o Allow access to local DNS/NTP 340 o Deny all other access 342 A printer might have a description that states: 344 o Allow access for port IPP or port LPD 346 o Allow local access for port HTTP 348 o Deny all other access 350 In this way anyone can print to the printer, but local access would 351 be required for the management interface. 353 The files that are retrieved are intended to be closely aligned to 354 existing network architectures so that they are easy to deploy. We 355 make use of YANG [RFC7950] because of the time and effort spent to 356 develop accurate and adequate models for use by network devices. 357 JSON is used as a serialization for compactness and readability, 358 relative to XML. Other formats may be chosen with later versions of 359 MUD. 361 While the policy examples given here focus on access control, this is 362 not intended to be the sole focus. By structuring the model 363 described in this document with clear extension points, other 364 descriptions could be included. One that often comes to mind is 365 quality of service. 367 The YANG modules specified here are extensions of 368 [I-D.ietf-netmod-acl-model]. The extensions to this model allow for 369 a manufacturer to express classes of systems that a manufacturer 370 would find necessary for the proper function of the device. Two 371 modules are specified. The first module specifies a means for domain 372 names to be used in ACLs so that devices that have their controllers 373 in the cloud may be appropriately authorized with domain names, where 374 the mapping of those names to addresses may rapidly change. 376 The other module abstracts away IP addresses into certain classes 377 that are instantiated into actual IP addresses through local 378 processing. Through these classes, manufacturers can specify how the 379 device is designed to communicate, so that network elements can be 380 configured by local systems that have local topological knowledge. 381 That is, the deployment populates the classes that the manufacturer 382 specifies. The abstractions below map to zero or more hosts, as 383 follows: 385 Manufacturer: A device made by a particular manufacturer, as 386 identified by the authority component of its MUD URL 388 same-manufacturer: Devices that have the same authority component of 389 their MUD URL. 391 controller: Devices that the local network administrator admits to 392 the particular class. 394 my-controller: Devices associated with the MUD URL of a device that 395 the administrator admits. 397 local: The class of IP addresses that are scoped within some 398 administrative boundary. By default it is suggested that this be 399 the local subnet. 401 The "manufacturer" classes can be easily specified by the 402 manufacturer, whereas controller classes are initially envisioned to 403 be specified by the administrator. 405 Because manufacturers do not know who will be using their devices, it 406 is important for functionality referenced in usage descriptions to be 407 relatively ubiquitous and mature. For these reasons only a limited 408 subset YANG-based configuration is permitted in a MUD file. 410 1.8. The Manufacturer Usage Description Architecture 412 With these components laid out we now have the basis for an 413 architecture. This leads us to ASCII art. 415 ....................................... 416 . ____________ . _____________ 417 . | | . | | 418 . | MUD |-->get URL-->| MUD | 419 . | Controller | .(https) | File Server | 420 . End system network |____________|<-MUD file<-<|_____________| 421 . . . 422 . . . 423 . _______ _________ . 424 .| | (dhcp et al) | router | . 425 .| Thing |---->MUD URL-->| or | . 426 .|_______| | switch | . 427 . |_________| . 428 ....................................... 430 Figure 1: MUD Architecture 432 In the above diagram, the switch or router collects MUD URLs and 433 forwards them to the MUD controller (a network management system) for 434 processing. This happens in different ways, depending on how the URL 435 is communicated. For instance, in the case of DHCP, the DHCP server 436 might receive the URL and then process it. In the case of IEEE 437 802.1X, the switch would carry the URL via a certificate to the 438 authentication server via EAP over Radius[RFC3748], which would then 439 process it. One method to do this is TEAP, described in [RFC7170]. 440 The certificate extension is described below. 442 The information returned by the MUD file server (a web server) is 443 valid for the duration of the Thing's connection, or as specified in 444 the description. Thus if the Thing is disconnected, any associated 445 configuration in the switch can be removed. Similarly, from time to 446 time the description may be refreshed, based on new capabilities or 447 communication patterns or vulnerabilities. 449 The web server is typically run by or on behalf of the manufacturer. 450 Its domain name is that of the authority found in the MUD URL. For 451 legacy cases where Things cannot emit a URL, if the switch is able to 452 determine the appropriate URL, it may proxy it, the trivial cases 453 being a hardcoded MUD-URL on a switch port, or a mapping from some 454 available identifier such as an L2 address or certificate hash to a 455 MUD-URL. 457 The role of the MUD controller in this environment is to do the 458 following: 460 o receive MUD URLs, 462 o fetch MUD files, 463 o translate abstractions in the MUD files to specific network 464 element configuration, 466 o maintain and update any required mappings of the abstractions, and 468 o update network elements with appropriate configuration. 470 A MUD controller may be a component of a AAA or network management 471 system. Communication within those systems and from those systems to 472 network elements is beyond the scope of this memo. 474 1.9. Order of operations 476 As mentioned above, MUD contains architectural building blocks, and 477 so order of operation may vary. However, here is one clear intended 478 example: 480 1. Thing emits URL. 482 2. That URL is forwarded to a MUD controller by the nearest switch 483 (how this happens depends on the way in which the MUD URL is 484 emitted). 486 3. The MUD controller retrieves the MUD file and signature from the 487 MUD file server, assuming it doesn't already have copies. After 488 validating the signature, it may test the URL against a web or 489 domain reputation service, and it may test any hosts within the 490 file against those reputation services, as it deems fit. 492 4. The MUD controller may query the administrator for permission to 493 add the Thing and associated policy. If the Thing is known or 494 the Thing type is known, it may skip this step. 496 5. The MUD controller instantiates local configuration based on the 497 abstractions defined in this document. 499 6. The MUD controller configures the switch nearest the Thing. 500 Other systems may be configured as well. 502 7. When the Thing disconnects, policy is removed. 504 2. The MUD Model and Semantic Meaning 506 A MUD file consists of a YANG model that has been serialized in JSON 507 [RFC7951]. For purposes of MUD, the nodes that can be modified are 508 access lists as augmented by this model. The MUD file is limited to 509 the serialization of only the following YANG schema: 511 o ietf-access-control-list [I-D.ietf-netmod-acl-model] 513 o ietf-mud (this document) 515 o ietf-acldns (this document) 517 Extensions may be used to add additional schema. This is described 518 further on. 520 To provide the widest possible deployment, publishers of MUD files 521 SHOULD make use of the abstractions in this memo and avoid the use of 522 IP addresses. A MUD controller SHOULD NOT automatically implement 523 any MUD file that contains IP addresses, especially those that might 524 have local significance. The addressing of one side of an access 525 list is implicit, based on whether it is applied as to-device-policy 526 or from-device-policy. 528 With the exceptions of "name" of the ACL, "type", "name" of the ACE, 529 and TCP and UDP source and destination port information, publishers 530 of MUD files SHOULD limit the use of ACL model leaf nodes expressed 531 to those found in this specification. Absent any extensions, MUD 532 files are assumed to implement only the following ACL model features: 534 o match-on-ipv4, match-on-ipv6, match-on-tcp, match-on-udp, match- 535 on-icmp 537 Furthermore, only "accept" or "drop" actions SHOULD be included. A 538 MUD controller MAY choose to interpret "reject" as "drop". A MUD 539 controller SHOULD ignore all other actions. This is because 540 manufacturers do not have sufficient context within a local 541 deployment to know whether reject is appropriate. That is a decision 542 that should be left to a network administrator. 544 Given that MUD does not deal with interfaces, the support of the 545 "ietf-interfaces" module [RFC7223] is not required. Specifically, 546 the support of interface-related features and branches (e.g., 547 interface-attachment and interface-stats) of the ACL YANG module is 548 not required. 550 In fact, MUD controllers MAY ignore any particular component of a 551 description or MAY ignore the description in its entirety, and SHOULD 552 carefully inspect all MUD descriptions. Publishers of MUD files MUST 553 NOT include other nodes except as described in Section 3.8. See that 554 section for more information. 556 2.1. The IETF-MUD YANG Module 558 This module is structured into three parts: 560 o The first container "mud" holds information that is relevant to 561 retrieval and validity of the MUD file itself, as well as policy 562 intended to and from the Thing. 564 o The second component augments the matching container of the ACL 565 model to add several nodes that are relevant to the MUD URL, or 566 otherwise abstracted for use within a local environment. 568 o The third component augments the tcp-acl container of the ACL 569 model to add the ability to match on the direction of initiation 570 of a TCP connection. 572 A valid MUD file will contain two root objects, a "mud" container and 573 an "acls" container. Extensions may add additional root objects as 574 required. As a reminder, when parsing access-lists, elements within 575 a "match" block are logically ANDed. In general, a single 576 abstraction in a match statement should be used. For instance, it 577 makes little sense to match both "my-controller" and "controller" 578 with an argument, since they are highly unlikely to be the same 579 value. 581 A simplified graphical representation of the data models is used in 582 this document. The meaning of the symbols in these diagrams is 583 explained in [I-D.ietf-netmod-yang-tree-diagrams]. 585 module: ietf-mud 586 +--rw mud! 587 +--rw mud-version uint8 588 +--rw mud-url inet:uri 589 +--rw last-update yang:date-and-time 590 +--rw mud-signature? inet:uri 591 +--rw cache-validity? uint8 592 +--rw is-supported boolean 593 +--rw systeminfo? string 594 +--rw mfg-name? string 595 +--rw model-name? string 596 +--rw firmware-rev? string 597 +--rw software-rev? string 598 +--rw extensions* string 599 +--rw from-device-policy 600 | +--rw access-lists 601 | +--rw access-list* [name] 602 | +--rw name -> /acl:access-lists/acl/name 603 +--rw to-device-policy 604 +--rw access-lists 605 +--rw access-list* [name] 606 +--rw name -> /acl:access-lists/acl/name 607 augment /acl:acls/acl:acl/acl:aces/acl:ace/acl:matches: 608 +--rw mud 609 +--rw manufacturer? inet:host 610 +--rw same-manufacturer? empty 611 +--rw model? inet:uri 612 +--rw local-networks? empty 613 +--rw controller? inet:uri 614 +--rw my-controller? empty 615 augment /acl:access-lists/acl:acl/acl:aces/acl:ace 616 /acl:matches/acl:l4/acl:tcp/acl:tcp: 617 +--rw direction-initiated? direction 619 3. Data Node Definitions 621 Note that in this section, when we use the term "match" we are 622 referring to the ACL model "matches" node. 624 The following nodes are defined. 626 3.1. mud-version 628 This node specifies the integer version of the MUD specification. 629 This memo specifies version 1. 631 3.2. to-device-policy and from-device-policy containers 633 [I-D.ietf-netmod-acl-model] describes access-lists. In the case of 634 MUD, a MUD file must be explicit in describing the communication 635 pattern of a Thing, and that includes indicating what is to be 636 permitted or denied in either direction of communication. Hence each 637 of these containers indicates the appropriate direction of a flow in 638 association with a particular Thing. They contain references to 639 specific access-lists. 641 3.3. last-update 643 This is a date-and-time value of when the MUD file was generated. 644 This is akin to a version number. Its form is taken from [RFC6991] 645 which, for those keeping score, in turn was taken from Section 5.6 of 646 [RFC3339], which was taken from [ISO.8601.1988]. 648 3.4. cache-validity 650 This uint8 is the period of time in hours that a network management 651 station MUST wait since its last retrieval before checking for an 652 update. It is RECOMMENDED that this value be no less than 24 and 653 MUST NOT be more than 168 for any Thing that is supported. This 654 period SHOULD be no shorter than any period determined through HTTP 655 caching directives (e.g., "cache-control" or "Expires"). N.B., 656 expiring of this timer does not require the MUD controller to discard 657 the MUD file, nor terminate access to a Thing. See Section 15 for 658 more information. 660 3.5. is-supported 662 This boolean is an indication from the manufacturer to the network 663 administrator as to whether or not the Thing is supported. In this 664 context a Thing is said to not be supported if the manufacturer 665 intends never to issue an update to the Thing or never update the MUD 666 file. A MUD controller MAY still periodically check for updates. 668 3.6. systeminfo 670 This is a textual UTF-8 description of the Thing to be connected. 671 The intent is for administrators to be able to see a localized name 672 associated with the Thing. It SHOULD NOT exceed 60 characters worth 673 of display space (that is- what the administrator actually sees). 675 3.7. mfg-name, software-rev, model-name firmware-rev 677 These optional fields are filled in as specified by 678 [I-D.ietf-netmod-entity]. Note that firmware-rev and software-rev 679 MUST NOT be populated in a MUD file if the device can be upgraded but 680 the MUD-URL cannot be. This would be the case, for instance, with 681 MUR-URLs that are contained in 802.1AR certificates. 683 3.8. extensions 685 This optional leaf-list names MUD extensions that are used in the MUD 686 file. Note that NO MUD extensions may be used in a MUD file without 687 the extensions being declared. Implementations MUST ignore any node 688 in this file that they do not understand. 690 Note that extensions can either extend the MUD file as described in 691 the previous paragraph, or they might reference other work. An 692 extension example can be found in Appendix C. 694 3.9. manufacturer 696 This node consists of a hostname that would be matched against the 697 authority component of another Thing's MUD URL. In its simplest form 698 "manufacturer" and "same-manufacturer" may be implemented as access- 699 lists. In more complex forms, additional network capabilities may be 700 used. For example, if one saw the line "manufacturer" : 701 "flobbidy.example.com", then all Things that registered with a MUD 702 URL that contained flobbity.example.com in its authority section 703 would match. 705 3.10. same-manufacturer 707 This null-valued node is an equivalent for when the manufacturer 708 element is used to indicate the authority that is found in another 709 Thing's MUD URL matches that of the authority found in this Thing's 710 MUD URL. For example, if the Thing's MUD URL were 711 https://b1.example.com/ThingV1, then all devices that had MUD URL 712 with an authority section of b1.example.com would match. 714 3.11. model 716 This string matches the entire MUD URL, thus covering the model that 717 is unique within the context of the authority. It may contain not 718 only model information, but versioning information as well, and any 719 other information that the manufacturer wishes to add. The intended 720 use is for devices of this precise class to match, to permit or deny 721 communication between one another. 723 3.12. local-networks 725 This null-valued node expands to include local networks. Its default 726 expansion is that packets must not traverse toward a default route 727 that is received from the router. However, administrators may expand 728 the expression as is appropriate in their deployments. 730 3.13. controller 732 This URI specifies a value that a controller will register with the 733 MUD controller. The node then is expanded to the set of hosts that 734 are so registered. This node may also be a URN. In this case, the 735 URN describes a well known service, such as DNS or NTP. 737 Great care should be used when invoking the controller class. For 738 one thing, it requires some understanding by the administrator as to 739 when it is appropriate. Classes that are standardized may make it 740 possible to easily name devices that support standard functions. For 741 instance, the MUD controller could have some knowledge of which DNS 742 servers should be used for any particular group of Things. Non- 743 standard classes will likely require some sort of administrator 744 interaction. Pre-registration in such classes by controllers with 745 the MUD server is encouraged. The mechanism to do that is beyond the 746 scope of this work. 748 Controller URIs MAY take the form of a URL (e.g. "http[s]://"). 749 However, MUD controllers MUST NOT resolve and retrieve such files, 750 and it is RECOMMENDED that there be no such file at this time, as 751 their form and function may be defined at a point in the future. For 752 now, URLs should serve simply as class names and may be populated by 753 the local deployment administrator. 755 3.14. my-controller 757 This null-valued node signals to the MUD controller to use whatever 758 mapping it has for this MUD URL to a particular group of hosts. This 759 may require prompting the administrator for class members. Future 760 work should seek to automate membership management. 762 3.15. direction-initiated 764 When applied this matches packets when the flow was initiated in the 765 corresponding direction. [RFC6092] specifies IPv6 guidance best 766 practices. While that document is scoped specifically to IPv6, its 767 contents are applicable for IPv4 as well. When this flag is set, and 768 the system has no reason to believe a flow has been initiated it MUST 769 drop the packet. This node may be implemented in its simplest form 770 by looking at naked SYN bits, but may also be implemented through 771 more stateful mechanisms. 773 4. Processing of the MUD file 775 To keep things relatively simple in addition to whatever definitions 776 exist, we also apply two additional default behaviors: 778 o Anything not explicitly permitted is denied. 780 o Local DNS and NTP are, by default, permitted to and from the 781 Thing. 783 An explicit description of the defaults can be found in Appendix B. 784 These are applied AFTER all other explicit rules. Thus, a default 785 behavior can be changed with a "drop" action. 787 5. What does a MUD URL look like? 789 MUD URLs are required to use the HTTPS scheme, in order to establish 790 the MUD file server's identity and assure integrity of the MUD file. 792 Any "https://" URL can be a MUD URL. For example: 794 https://things.example.org/product_abc123/v5 795 https://www.example.net/mudfiles/temperature_sensor/ 796 https://example.com/lightbulbs/colour/v1 798 The MUD URL identifies a Thing with a specificity according to the 799 manufacturer's wishes. It could include a brand name, model number, 800 or something more specific. It also could provide a means to 801 indicate what version the product is. 803 Specifically, if the intended communication patterns of a Thing 804 change, as compared to other things, the MUD URL should change. For 805 example, if a new model of light bulb is released that requires 806 access to different network services, it would have a separate MUD 807 URL from those that do not. 809 6. The MUD YANG Model 811 file "ietf-mud@2018-03-01.yang" 812 module ietf-mud { 813 yang-version 1.1; 814 namespace "urn:ietf:params:xml:ns:yang:ietf-mud"; 815 prefix ietf-mud; 817 import ietf-access-control-list { 818 prefix acl; 819 } 820 import ietf-yang-types { 821 prefix yang; 822 } 823 import ietf-inet-types { 824 prefix inet; 825 } 827 organization 828 "IETF OPSAWG (Ops Area) Working Group"; 829 contact 830 "WG Web: http://tools.ietf.org/wg/opsawg/ 831 WG List: opsawg@ietf.org 832 Author: Eliot Lear 833 lear@cisco.com 834 Author: Ralph Droms 835 rdroms@gmail.com 836 Author: Dan Romascanu 837 dromasca@gmail.com 839 "; 840 description 841 "This YANG module defines a component that augments the 842 IETF description of an access list. This specific module 843 focuses on additional filters that include local, model, 844 and same-manufacturer. 846 This module is intended to be serialized via JSON and stored 847 as a file, as described in RFC XXXX [RFC Editor to fill in with 848 this document #]. 850 Copyright (c) 2016,2017 IETF Trust and the persons 851 identified as the document authors. All rights reserved. 852 Redistribution and use in source and binary forms, with or 853 without modification, is permitted pursuant to, and subject 854 to the license terms contained in, the Simplified BSD 855 License set forth in Section 4.c of the IETF Trust's Legal 856 Provisions Relating to IETF Documents 857 (http://trustee.ietf.org/license-info). 858 This version of this YANG module is part of RFC XXXX; see 859 the RFC itself for full legal notices."; 861 revision 2018-03-01 { 862 description 863 "Initial proposed standard."; 864 reference 865 "RFC XXXX: Manufacturer Usage Description 866 Specification"; 867 } 869 typedef direction { 870 type enumeration { 871 enum "to-device" { 872 description 873 "packets or flows destined to the target 874 Thing"; 875 } 876 enum "from-device" { 877 description 878 "packets or flows destined from 879 the target Thing"; 880 } 881 } 882 description 883 "Which way are we talking about?"; 884 } 886 container mud { 887 presence "Enabled for this particular MUD URL"; 888 description 889 "MUD related information, as specified 890 by RFC-XXXX [RFC Editor to fill in]."; 891 uses mud-grouping; 892 } 894 grouping mud-grouping { 895 description 896 "Information about when support end(ed), and 897 when to refresh"; 899 leaf mud-version { 900 type uint8; 901 mandatory true; 902 description "This is the version of the MUD 903 specification. This memo specifies version 1."; 904 } 906 leaf mud-url { 907 type inet:uri; 908 mandatory true; 909 description 910 "This is the MUD URL associated with the entry found 911 in a MUD file."; 912 } 913 leaf last-update { 914 type yang:date-and-time; 915 mandatory true; 916 description 917 "This is intended to be when the current MUD file 918 was generated. MUD Controllers SHOULD NOT check 919 for updates between this time plus cache validity"; 920 } 922 leaf mud-signature { 923 type inet:uri; 924 description "A URI that resolves to a signature as 925 described in this specification."; 926 } 928 leaf cache-validity { 929 type uint8 { 930 range "1..168"; 931 } 932 units "hours"; 933 default "48"; 934 description 935 "The information retrieved from the MUD server is 936 valid for these many hours, after which it should 937 be refreshed. N.B. MUD controller implementations 938 need not discard MUD files beyond this period."; 939 } 940 leaf is-supported { 941 type boolean; 942 mandatory true; 943 description 944 "This boolean indicates whether or not the Thing is 945 currently supported by the manufacturer."; 946 } 947 leaf systeminfo { 948 type string; 949 description 950 "A UTF-8 description of this Thing. This 951 should be a brief description that may be 952 displayed to the user to determine whether 953 to allow the Thing on the 954 network."; 955 } 957 leaf mfg-name { 958 type string; 959 description "Manufacturer name, as described in 960 the ietf-hardware yang module."; 962 } 964 leaf model-name { 965 type string; 966 description "Model name, as described in the 967 ietf-hardware yang module."; 968 } 970 leaf firmware-rev { 971 type string; 972 description "firmware-rev, as described in the 973 ietf-hardware yang module. Note this field MUST 974 NOT be included when the device can be updated 975 but the MUD-URL cannot."; 976 } 978 leaf software-rev { 979 type string; 980 description "software-rev, as described in the 981 ietf-hardware yang module. Note this field MUST 982 NOT be included when the device can be updated 983 but the MUD-URL cannot."; 984 } 986 leaf-list extensions { 987 type string { 988 length "1..40"; 989 } 990 description 991 "A list of extension names that are used in this MUD 992 file. Each name is registered with the IANA and 993 described in an RFC."; 994 } 995 container from-device-policy { 996 description 997 "The policies that should be enforced on traffic 998 coming from the device. These policies are not 999 necessarily intended to be enforced at a single 1000 point, but may be rendered by the controller to any 1001 relevant enorcement points in the network or 1002 elsewhere."; 1003 uses access-lists; 1004 } 1005 container to-device-policy { 1006 description 1007 "The policies that should be enforced on traffic 1008 going to the device. These policies are not 1009 necessarily intended to be enforced at a single 1010 point, but may be rendered by the controller to any 1011 relevant enorcement points in the network or 1012 elsewhere."; 1013 uses access-lists; 1014 } 1015 } 1017 grouping access-lists { 1018 description 1019 "A grouping for access lists in the context of device 1020 policy."; 1021 container access-lists { 1022 description 1023 "The access lists that should be applied to traffic 1024 to or from the device."; 1025 list access-list { 1026 key "name"; 1027 description 1028 "Each entry on this list refers to an ACL that 1029 should be present in the overall access list 1030 data model. Each ACL is identified by name and 1031 type."; 1032 leaf name { 1033 type leafref { 1034 path "/acl:acls/acl:acl/acl:name"; 1035 } 1036 description 1037 "The name of the ACL for this entry."; 1038 } 1039 } 1040 } 1041 } 1042 augment "/acl:acls/acl:acl/acl:aces/acl:ace/acl:matches" { 1043 description 1044 "adding abstractions to avoid need of IP addresses"; 1045 container mud { 1046 description 1047 "MUD-specific matches."; 1048 leaf manufacturer { 1049 type inet:host; 1050 description 1051 "A domain that is intended to match the authority 1052 section of the MUD URL. This node is used to specify 1053 one or more manufacturers a device should 1054 be authorized to access."; 1055 } 1056 leaf same-manufacturer { 1057 type empty; 1058 description 1059 "This node matches the authority section of the MUD URL 1060 of a Thing. It is intended to grant access to all 1061 devices with the same authority section."; 1062 } 1063 leaf model { 1064 type inet:uri; 1065 description 1066 "Devices of the specified model type will match if 1067 they have an identical MUD URL."; 1068 } 1069 leaf local-networks { 1070 type empty; 1071 description 1072 "IP addresses will match this node if they are 1073 considered local addresses. A local address may be 1074 a list of locally defined prefixes and masks 1075 that indicate a particular administrative scope."; 1076 } 1077 leaf controller { 1078 type inet:uri; 1079 description 1080 "This node names a class that has associated with it 1081 zero or more IP addresses to match against. These 1082 may be scoped to a manufacturer or via a standard 1083 URN."; 1084 } 1085 leaf my-controller { 1086 type empty; 1087 description 1088 "This node matches one or more network elements that 1089 have been configured to be the controller for this 1090 Thing, based on its MUD URL."; 1091 } 1092 } 1093 } 1094 augment "/acl:acls/acl:acl/acl:aces/" + 1095 "acl:ace/acl:matches/acl:l4/acl:tcp/acl:tcp" { 1096 description 1097 "add direction-initiated"; 1098 leaf direction-initiated { 1099 type direction; 1100 description 1101 "This node matches based on which direction a 1102 connection was initiated. The means by which that 1103 is determined is discussed in this document."; 1104 } 1105 } 1107 } 1109 1111 7. The Domain Name Extension to the ACL Model 1113 This module specifies an extension to IETF-ACL model such that domain 1114 names may be referenced by augmenting the "matches" node. Different 1115 implementations may deploy differing methods to maintain the mapping 1116 between IP address and domain name, if indeed any are needed. 1117 However, the intent is that resources that are referred to using a 1118 name should be authorized (or not) within an access list. 1120 The structure of the change is as follows: 1122 module: ietf-acldns 1123 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/ 1124 acl:matches/acl:l3/acl:ipv4/acl:ipv4: 1125 +--rw src-dnsname? inet:host 1126 +--rw dst-dnsname? inet:host 1127 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/ 1128 acl:matches/acl:l3/acl:ipv6/acl:ipv6: 1129 +--rw src-dnsname? inet:host 1130 +--rw dst-dnsname? inet:host 1132 The choice of these particular points in the access-list model is 1133 based on the assumption that we are in some way referring to IP- 1134 related resources, as that is what the DNS returns. A domain name in 1135 our context is defined in [RFC6991]. The augmentations are 1136 replicated across IPv4 and IPv6 to allow MUD file authors the ability 1137 to control the IP version that the Thing may utilize. 1139 The following node are defined. 1141 7.1. src-dnsname 1143 The argument corresponds to a domain name of a source as specified by 1144 inet:host. A number of means may be used to resolve hosts. What is 1145 important is that such resolutions be consistent with ACLs required 1146 by Things to properly operate. 1148 7.2. dst-dnsname 1150 The argument corresponds to a domain name of a destination as 1151 specified by inet:host See the previous section relating to 1152 resolution. 1154 Note when using either of these with a MUD file, because access is 1155 associated with a particular Thing, MUD files MUST not contain either 1156 a src-dnsname in an ACL associated with from-device-policy or a dst- 1157 dnsname associated with to-device-policy. 1159 7.3. The ietf-acldns Model 1161 file "ietf-acldns@2018-03-01.yang" 1162 module ietf-acldns { 1163 yang-version 1.1; 1164 namespace "urn:ietf:params:xml:ns:yang:ietf-acldns"; 1165 prefix "ietf-acldns"; 1167 import ietf-access-control-list { 1168 prefix "acl"; 1169 } 1171 import ietf-inet-types { 1172 prefix "inet"; 1173 } 1175 organization 1176 "IETF OPSAWG (Ops Area) Working Group"; 1178 contact 1179 "WG Web: http://tools.ietf.org/wg/opsawg/ 1180 WG List: opsawg@ietf.org 1181 Author: Eliot Lear 1182 lear@cisco.com 1183 Author: Ralph Droms 1184 rdroms@gmail.com 1185 Author: Dan Romascanu 1186 dromasca@gmail.com 1187 "; 1189 description 1190 "This YANG module defines a component that augments the 1191 IETF description of an access list to allow dns names 1192 as matching criteria."; 1194 revision 2018-03-01 { 1195 description "Base version of dnsname extension of ACL model"; 1196 reference "RFC XXXX: Manufacturer Usage Description 1197 Specification"; 1198 } 1200 grouping dns-matches { 1201 description "Domain names for matching."; 1202 leaf src-dnsname { 1203 type inet:host; 1204 description "domain name to be matched against"; 1205 } 1206 leaf dst-dnsname { 1207 type inet:host; 1208 description "domain name to be matched against"; 1209 } 1210 } 1212 augment "/acl:acls/acl:acl/acl:aces/acl:ace/" + 1213 "acl:matches/acl:l3/acl:ipv4/acl:ipv4" { 1214 description "Adding domain names to matching"; 1215 uses dns-matches; 1216 } 1218 augment "/acl:acls/acl:acl/" + 1219 "acl:aces/acl:ace/" + 1220 "acl:matches/acl:l3/acl:ipv6/acl:ipv6" { 1221 description "Adding domain names to matching"; 1222 uses dns-matches; 1223 } 1224 } 1225 1227 8. MUD File Example 1229 This example contains two access lists that are intended to provide 1230 outbound access to a cloud service on TCP port 443. 1232 { 1233 "ietf-mud:mud": { 1234 "mud-version": 1, 1235 "mud-url": "https://lighting.example.com/lightbulb2000", 1236 "last-update": "2018-03-02T11:20:51+01:00", 1237 "cache-validity": 48, 1238 "is-supported": true, 1239 "systeminfo": "The BMS Example Lightbulb", 1240 "from-device-policy": { 1241 "access-lists": { 1242 "access-list": [ 1243 { 1244 "name": "mud-76100-v6fr" 1245 } 1246 ] 1247 } 1248 }, 1249 "to-device-policy": { 1250 "access-lists": { 1251 "access-list": [ 1252 { 1253 "name": "mud-76100-v6to" 1254 } 1255 ] 1256 } 1257 } 1258 }, 1259 "ietf-access-control-list:access-lists": { 1260 "acl": [ 1261 { 1262 "name": "mud-76100-v6to", 1263 "type": "ipv6-acl-type", 1264 "aces": { 1265 "ace": [ 1266 { 1267 "name": "cl0-todev", 1268 "matches": { 1269 "ipv6": { 1270 "ietf-acldns:src-dnsname": "test.com", 1271 "protocol": 6 1272 }, 1273 "tcp": { 1274 "ietf-mud:direction-initiated": "from-device", 1275 "source-port": { 1276 "operator": "eq", 1277 "port": 443 1278 } 1279 } 1280 }, 1281 "actions": { 1282 "forwarding": "accept" 1283 } 1284 } 1285 ] 1286 } 1287 }, 1288 { 1289 "name": "mud-76100-v6fr", 1290 "type": "ipv6-acl-type", 1291 "aces": { 1292 "ace": [ 1293 { 1294 "name": "cl0-frdev", 1295 "matches": { 1296 "ipv6": { 1297 "ietf-acldns:dst-dnsname": "test.com", 1298 "protocol": 6 1299 }, 1300 "tcp": { 1301 "ietf-mud:direction-initiated": "from-device", 1302 "destination-port": { 1303 "operator": "eq", 1304 "port": 443 1305 } 1306 } 1307 }, 1308 "actions": { 1309 "forwarding": "accept" 1310 } 1311 } 1312 ] 1313 } 1314 } 1315 ] 1316 } 1317 } 1319 In this example, two policies are declared, one from the Thing and 1320 the other to the Thing. Each policy names an access list that 1321 applies to the Thing, and one that applies from. Within each access 1322 list, access is permitted to packets flowing to or from the Thing 1323 that can be mapped to the domain name of "service.bms.example.com". 1324 For each access list, the enforcement point should expect that the 1325 Thing initiated the connection. 1327 9. The MUD URL DHCP Option 1329 The IPv4 MUD URL client option has the following format: 1331 +------+-----+------------------------------ 1332 | code | len | MUDstring 1333 +------+-----+------------------------------ 1335 Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single 1336 octet that indicates the length of MUD string in octets. The MUD 1337 string is defined as follows: 1339 MUDstring = mudurl [ " " reserved ] 1340 mudurl = URI; a URL [RFC3986] that uses the "https" schema [RFC7230] 1341 reserved = 1*( CHAR ) ; from [RFC5234] 1343 The entire option MUST NOT exceed 255 octets. If a space follows the 1344 MUD URL, a reserved string that will be defined in future 1345 specifications follows. MUD controllers that do not understand this 1346 field MUST ignore it. 1348 The IPv6 MUD URL client option has the following format: 1350 0 1 2 3 1351 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 1352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1353 | OPTION_MUD_URL_V6 | option-length | 1354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1355 | MUDstring | 1356 | | 1357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1359 OPTION_MUD_URL_V6 (112; assigned by IANA). 1361 option-length contains the length of the MUDstring, as defined above, 1362 in octets. 1364 The intent of this option is to provide both a new Thing classifier 1365 to the network as well as some recommended configuration to the 1366 routers that implement policy. However, it is entirely the purview 1367 of the network system as managed by the network administrator to 1368 decide what to do with this information. The key function of this 1369 option is simply to identify the type of Thing to the network in a 1370 structured way such that the policy can be easily found with existing 1371 toolsets. 1373 9.1. Client Behavior 1375 A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit 1376 DHCPv6 option. These options are singletons, as specified in 1377 [RFC7227]. Because clients are intended to have at most one MUD URL 1378 associated with them, they may emit at most one MUD URL option via 1379 DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4 1380 and v6 DHCP options are emitted, the same URL MUST be used. 1382 Clients SHOULD log or otherwise report improper acknowledgments from 1383 servers, but they MUST NOT modify their MUD URL configuration based 1384 on a server's response. The server's response is only an 1385 acknowledgment that the server has processed the option, and promises 1386 no specific network behavior to the client. In particular, it may 1387 not be possible for the server to retrieve the file associated with 1388 the MUD URL, or the local network administration may not wish to use 1389 the usage description. Neither of these situations should be 1390 considered in any way exceptional. 1392 9.2. Server Behavior 1394 A DHCP server may ignore these options or take action based on 1395 receipt of these options. If a server successfully parses the option 1396 and the URL, it MUST return the option with length field set to zero 1397 and a corresponding null URL field as an acknowledgment. Even in 1398 this circumstance, no specific network behavior is guaranteed. When 1399 a server consumes this option, it will either forward the URL and 1400 relevant client information (such as the gateway address or giaddr) 1401 to a network management system, or it will retrieve the usage 1402 description itself by resolving the URL. 1404 DHCP servers may implement MUD functionality themselves or they may 1405 pass along appropriate information to a network management system or 1406 MUD controller. A DHCP server that does process the MUD URL MUST 1407 adhere to the process specified in [RFC2818] and [RFC5280] to 1408 validate the TLS certificate of the web server hosting the MUD file. 1409 Those servers will retrieve the file, process it, create and install 1410 the necessary configuration on the relevant network element. Servers 1411 SHOULD monitor the gateway for state changes on a given interface. A 1412 DHCP server that does not provide MUD functionality and has forwarded 1413 a MUD URL to a MUD controller MUST notify the MUD controller of any 1414 corresponding change to the DHCP state of the client (such as 1415 expiration or explicit release of a network address lease). 1417 9.3. Relay Requirements 1419 There are no additional requirements for relays. 1421 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 1423 This section defines an X.509 non-critical certificate extension that 1424 contains a single Uniform Resource Locator (URL) that points to an 1425 on-line Manufacturer Usage Description concerning the certificate 1426 subject. URI must be represented as described in Section 7.4 of 1427 [RFC5280]. 1429 Any Internationalized Resource Identifiers (IRIs) MUST be mapped to 1430 URIs as specified in Section 3.1 of [RFC3987] before they are placed 1431 in the certificate extension. 1433 The semantics of the URL are defined Section 5 of this document. 1435 The choice of id-pe is based on guidance found in Section 4.2.2 of 1436 [RFC5280]: 1438 These extensions may be used to direct applications to on-line 1439 information about the issuer or the subject. 1441 The MUD URL is precisely that: online information about the 1442 particular subject. 1444 The new extension is identified as follows: 1446 1448 MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) 1449 internet(1) security(5) mechanisms(5) pkix(7) 1450 id-mod(0) id-mod-mudURLExtn2016(88) } 1452 DEFINITIONS IMPLICIT TAGS ::= BEGIN 1454 -- EXPORTS ALL -- 1456 IMPORTS 1457 EXTENSION 1458 FROM PKIX-CommonTypes-2009 1459 { iso(1) identified-organization(3) dod(6) internet(1) 1460 security(5) mechanisms(5) pkix(7) id-mod(0) 1461 id-mod-pkixCommon-02(57) } 1463 id-pe 1464 FROM PKIX1Explicit-2009 1465 { iso(1) identified-organization(3) dod(6) internet(1) 1466 security(5) mechanisms(5) pkix(7) id-mod(0) 1467 id-mod-pkix1-explicit-02(51) } ; 1468 MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... } 1469 ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax 1470 IDENTIFIED BY id-pe-mud-url } 1472 id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 } 1474 MUDURLSyntax ::= IA5String 1476 END 1478 1480 While this extension can appear in either an 802.AR manufacturer 1481 certificate (IDevID) or deployment certificate (LDevID), of course it 1482 is not guaranteed in either, nor is it guaranteed to be carried over. 1483 It is RECOMMENDED that MUD controller implementations maintain a 1484 table that maps a Thing to its MUD URL based on IDevIDs. 1486 11. The Manufacturer Usage Description LLDP extension 1488 The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop 1489 vendor-neutral link layer protocol used by end hosts network Things 1490 for advertising their identity, capabilities, and neighbors on an 1491 IEEE 802 local area network. Its Type-Length-Value (TLV) design 1492 allows for 'vendor-specific' extensions to be defined. IANA has a 1493 registered IEEE 802 organizationally unique identifier (OUI) defined 1494 as documented in [RFC7042]. The MUD LLDP extension uses a subtype 1495 defined in this document to carry the MUD URL. 1497 The LLDP vendor specific frame has the following format: 1499 +--------+--------+----------+---------+-------------- 1500 |TLV Type| len | OUI |subtype | MUD URL 1501 | =127 | |= 00 00 5E| = 1 | 1502 |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets) 1503 +--------+--------+----------+---------+-------------- 1505 where: 1507 o TLV Type = 127 indicates a vendor-specific TLV 1509 o len - indicates the TLV string length 1511 o OUI = 00 00 5E is the organizationally unique identifier of IANA 1513 o subtype = 1 (to be assigned by IANA for the MUD URL) 1515 o MUD URL - the length MUST NOT exceed 255 octets 1517 The intent of this extension is to provide both a new Thing 1518 classifier to the network as well as some recommended configuration 1519 to the routers that implement policy. However, it is entirely the 1520 purview of the network system as managed by the network administrator 1521 to decide what to do with this information. The key function of this 1522 extension is simply to identify the type of Thing to the network in a 1523 structured way such that the policy can be easily found with existing 1524 toolsets. 1526 Hosts, routers, or other network elements that implement this option 1527 are intended to have at most one MUD URL associated with them, so 1528 they may transmit at most one MUD URL value. 1530 Hosts, routers, or other network elements that implement this option 1531 may ignore these options or take action based on receipt of these 1532 options. For example they may fill in information in the respective 1533 extensions of the LLDP Management Information Base (LLDP MIB). LLDP 1534 operates in a one-way direction. LLDPDUs are not exchanged as 1535 information requests by one Thing and response sent by another Thing. 1536 The other Things do not acknowledge LLDP information received from a 1537 Thing. No specific network behavior is guaranteed. When a Thing 1538 consumes this extension, it may either forward the URL and relevant 1539 remote Thing information to a MUD controller, or it will retrieve the 1540 usage description by resolving the URL in accordance with normal HTTP 1541 semantics. 1543 12. Creating and Processing of Signed MUD Files 1545 Because MUD files contain information that may be used to configure 1546 network access lists, they are sensitive. To insure that they have 1547 not been tampered with, it is important that they be signed. We make 1548 use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for 1549 this purpose. 1551 12.1. Creating a MUD file signature 1553 A MUD file MUST be signed using CMS as an opaque binary object. In 1554 order to make successful verification more likely, intermediate 1555 certificates SHOULD be included. The signature is stored at the 1556 location specified in the MUD file. Signatures are transferred using 1557 content-type "application/pkcs7-signature". 1559 For example: 1561 % openssl cms -sign -signer mancertfile -inkey mankey \ 1562 -in mudfile -binary -outform DER - \ 1563 -certfile intermediatecert -out mudfile.p7s 1565 Note: A MUD file may need to be re-signed if the signature expires. 1567 12.2. Verifying a MUD file signature 1569 Prior to retrieving a MUD file the MUD controller SHOULD retrieve the 1570 MUD signature file by retrieving the value of "mud-signature" and 1571 validating the signature across the MUD file. 1573 Upon retrieving a MUD file, a MUD controller MUST validate the 1574 signature of the file before continuing with further processing. A 1575 MUD controller MUST cease processing of that file it cannot validate 1576 the chain of trust to a known trust anchor until an administrator has 1577 given approval. 1579 The purpose of the signature on the file is to assign accountability 1580 to an entity, whose reputation can be used to guide administrators on 1581 whether or not to accept a given MUD file. It is already common 1582 place to check web reputation on the location of a server on which a 1583 file resides. While it is likely that the manufacturer will be the 1584 signer of the file, this is not strictly necessary, and may not be 1585 desirable. For one thing, in some environments, integrators may 1586 install their own certificates. For another, what is more important 1587 is the accountability of the recommendation, and not the 1588 cryptographic relationship between the device and the file. 1590 An example: 1592 % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile 1594 Note the additional step of verifying the common trust root. 1596 13. Extensibility 1598 One of our design goals is to see that MUD files are able to be 1599 understood by as broad a cross-section of systems as is possible. 1600 Coupled with the fact that we have also chosen to leverage existing 1601 mechanisms, we are left with no ability to negotiate extensions and a 1602 limited desire for those extensions in any event. A such, a two-tier 1603 extensibility framework is employed, as follows: 1605 1. At a coarse grain, a protocol version is included in a MUD URL. 1606 This memo specifies MUD version 1. Any and all changes are 1607 entertained when this version is bumped. Transition approaches 1608 between versions would be a matter for discussion in future 1609 versions. 1611 2. At a finer grain, only extensions that would not incur additional 1612 risk to the Thing are permitted. Specifically, adding nodes to 1613 the mud container is permitted with the understanding that such 1614 additions will be ignored by unaware implementations. Any such 1615 extensions SHALL be standardized through the IETF process, and 1616 MUST be named in the "extensions" list. MUD controllers MUST 1617 ignore YANG nodes they do not understand and SHOULD create an 1618 exception to be resolved by an administrator, so as to avoid any 1619 policy inconsistencies. 1621 14. Deployment Considerations 1623 Because MUD consists of a number of architectural building blocks, it 1624 is possible to assemble different deployment scenarios. One key 1625 aspect is where to place policy enforcement. In order to protect the 1626 Thing from other Things within a local deployment, policy can be 1627 enforced on the nearest switch or access point. In order to limit 1628 unwanted traffic within a network, it may also be advisable to 1629 enforce policy as close to the Internet as possible. In some 1630 circumstances, policy enforcement may not be available at the closest 1631 hop. At that point, the risk of so-called east-west infection is 1632 increased to the number of Things that are able to communicate 1633 without protection. 1635 A caution about some of the classes: admission of a Thing into the 1636 "manufacturer" and "same-manufacturer" class may have impact on 1637 access of other Things. Put another way, the admission may grow the 1638 access-list on switches connected to other Things, depending on how 1639 access is managed. Some care should be given on managing that 1640 access-list growth. Alternative methods such as additional network 1641 segmentation can be used to keep that growth within reason. 1643 Because as of this writing MUD is a new concept, one can expect a 1644 great many devices to not have implemented it. It remains a local 1645 deployment decision as to whether a device that is first connected 1646 should be alloewed broad or limited access. Furthermore, as 1647 mentioned in the introduction, a deployment may choose to ignore a 1648 MUD policy in its entirety, but simply taken into account the MUD URL 1649 as a classifier to be used as part of a local policy decision. 1651 15. Security Considerations 1653 Based on how a MUD URL is emitted, a Thing may be able to lie about 1654 what it is, thus gaining additional network access. There are 1655 several means to limit risk in this case. The most obvious is to 1656 only believe Things that make use of certificate-based authentication 1657 such as IEEE 802.1AR certificates. When those certificates are not 1658 present, Things claiming to be of a certain manufacturer SHOULD NOT 1659 be included in that manufacturer grouping without additional 1660 validation of some form. This will occur when it makes use of 1661 primitives such as "manufacturer" for the purpose of accessing Things 1662 of a particular type. Similarly, network management systems may be 1663 able to fingerprint the Thing. In such cases, the MUD URL can act as 1664 a classifier that can be proven or disproven. Fingerprinting may 1665 have other advantages as well: when 802.1AR certificates are used, 1666 because they themselves cannot change, fingerprinting offers the 1667 opportunity to add artificats to the MUD URL. The meaning of such 1668 artifacts is left as future work. 1670 Network management systems SHOULD NOT accept a usage description for 1671 a Thing with the same MAC address that has indicated a change of 1672 authority without some additional validation (such as review by a 1673 network administrator). New Things that present some form of 1674 unauthenticated MUD URL SHOULD be validated by some external means 1675 when they would be otherwise be given increased network access. 1677 It may be possible for a rogue manufacturer to inappropriately 1678 exercise the MUD file parser, in order to exploit a vulnerability. 1679 There are three recommended approaches to address this threat. The 1680 first is to validate the signature of the MUD file. The second is to 1681 have a system do a primary scan of the file to ensure that it is both 1682 parseable and believable at some level. MUD files will likely be 1683 relatively small, to start with. The number of ACEs used by any 1684 given Thing should be relatively small as well. It may also be 1685 useful to limit retrieval of MUD URLs to only those sites that are 1686 known to have decent web or domain reputations. 1688 Use of a URL necessitates the use of domain names. If a domain name 1689 changes ownership, the new owner of that domain may be able to 1690 provide MUD files that MUD controllers would consider valid. There 1691 are a few approaches that can mitigate this attack. First, MUD 1692 controllers SHOULD cache certificates used by the MUD file server. 1693 When a new certificate is retrieved for whatever reason, the MUD 1694 controller should check to see if ownership of the domain has 1695 changed. A fair programmatic approximation of this is when the name 1696 servers for the domain have changed. If the actual MUD file has 1697 changed, the controller MAY check the WHOIS database to see if 1698 registration ownership of a domain has changed. If a change has 1699 occured, or if for some reason it is not possible to determine 1700 whether ownership has changed, further review may be warranted. 1701 Note, this remediation does not take into account the case of a Thing 1702 that was produced long ago and only recently fielded, or the case 1703 where a new MUD controller has been installed. 1705 It may not be possible for a MUD controller to retrieve a MUD file at 1706 any given time. Should a MUD controller fail to retrieve a MUD file, 1707 it SHOULD consider the existing one safe to use, at least for a time. 1708 After some period, it SHOULD log that it has been unable to retrieve 1709 the file. There may be very good reasons for such failures, 1710 including the possibility that the MUD controller is in an off-line 1711 environment, the local Internet connection has failed, or the remote 1712 Internet connection has failed. It is also possible that an attacker 1713 is attempting to prevent onboarding of a device. It is a local 1714 deployment decision as to whether or not devices may be onboarded in 1715 the face of such failures. 1717 The release of a MUD URL by a Thing reveals what the Thing is, and 1718 provides an attacker with guidance on what vulnerabilities may be 1719 present. 1721 While the MUD URL itself is not intended to be unique to a specific 1722 Thing, the release of the URL may aid an observer in identifying 1723 individuals when combined with other information. This is a privacy 1724 consideration. 1726 In addressing both of these concerns, implementors should take into 1727 account what other information they are advertising through 1728 mechanisms such as mDNS[RFC6872], how a Thing might otherwise be 1729 identified, perhaps through how it behaves when it is connected to 1730 the network, whether a Thing is intended to be used by individuals or 1731 carry personal identifying information, and then apply appropriate 1732 data minimization techniques. One approach is to make use of TEAP 1733 [RFC7170] as the means to share information with authorized 1734 components in the network. Network elements may also assist in 1735 limiting access to the MUD URL through the use of mechanisms such as 1736 DHCPv6-Shield [RFC7610]. 1738 Please note that the security considerations mentioned in Section 4.7 1739 of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case 1740 because the YANG serialization is not intended to be accessed via 1741 NETCONF. However, for those who try to instantiate this model in a 1742 network element via NETCONF, all objects in each model in this draft 1743 exhibit similar security characteristics as 1744 [I-D.ietf-netmod-acl-model]. The basic purpose of MUD is to 1745 configure access, and so by its very nature can be disruptive if used 1746 by unauthorized parties. 1748 16. IANA Considerations 1750 16.1. YANG Module Registrations 1752 The following YANG modules are requested to be registred in the "IANA 1753 Module Names" registry: 1755 The ietf-mud module: 1757 o Name: ietf-mud 1759 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud 1761 o Prefix: ief-mud 1763 o Reference: This memo 1765 The ietf-acldns module: 1767 o Name: ietf-acldns 1769 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns 1771 o Prefix: ietf-acldns 1773 o Reference: This memo 1775 16.2. DHCPv4 and DHCPv6 Options 1777 The IANA has allocated option 161 in the Dynamic Host Configuration 1778 Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry 1779 for the MUD DHCPv4 option, and option 112 for DHCPv6, as described in 1780 Section 9. 1782 16.3. PKIX Extensions 1784 IANA is kindly requested to make the following assignments for: 1786 o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for 1787 PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). 1789 o id-pe-mud-url object identifier from the "SMI Security for PKIX 1790 Certificate Extension" registry (1.3.6.1.5.5.7.1). 1792 The use of these values is specified in Section 10. 1794 16.4. MIME Media-type Registration for MUD files 1796 The following media-type is defined for transfer of MUD file: 1798 o Type name: application 1799 o Subtype name: mud+json 1800 o Required parameters: n/a 1801 o Optional parameters: n/a 1802 o Encoding considerations: 8bit; application/mud+json values 1803 are represented as a JSON object; UTF-8 encoding SHOULD be 1804 employed. 1805 o Security considerations: See Security Considerations 1806 of this document. 1807 o Interoperability considerations: n/a 1808 o Published specification: this document 1809 o Applications that use this media type: MUD controllers as 1810 specified by this document. 1811 o Fragment identifier considerations: n/a 1812 o Additional information: 1814 Magic number(s): n/a 1815 File extension(s): n/a 1816 Macintosh file type code(s): n/a 1818 o Person & email address to contact for further information: 1819 Eliot Lear , Ralph Droms 1820 o Intended usage: COMMON 1821 o Restrictions on usage: none 1822 o Author: 1823 Eliot Lear 1824 Ralph Droms 1825 o Change controller: IESG 1826 o Provisional registration? (standards tree only): No. 1828 16.5. LLDP IANA TLV Subtype Registry 1830 IANA is requested to create a new registry for IANA Link Layer 1831 Discovery Protocol (LLDP) TLV subtype values. The recommended policy 1832 for this registry is Expert Review. The maximum number of entries in 1833 the registry is 256. 1835 IANA is required to populate the initial registry with the value: 1837 LLDP subtype value = 1 (All the other 255 values should be initially 1838 marked as 'Unassigned'.) 1840 Description = the Manufacturer Usage Description (MUD) Uniform 1841 Resource Locator (URL) 1843 Reference = < this document > 1845 16.6. The MUD Well Known Universal Resource Name (URNs) 1847 The following parameter registry is requested to be added in 1848 accordance with [RFC3553] 1850 Registry name: "urn:ietf:params:mud" is requested. 1851 Specification: this document 1852 Repository: this document 1853 Index value: Encoded identically to a TCP/UDP port service 1854 name, as specified in Section 5.1 of [RFC6335] 1856 The following entries should be added to the "urn:ietf:params:mud" 1857 name space: 1859 "urn:ietf:params:mud:dns" refers to the service specified by 1860 [RFC1123]. "urn:ietf:params:mud:ntp" refers to the service specified 1861 by [RFC5905]. 1863 16.7. Extensions Registry 1865 The IANA is requested to establish a registry of extensions as 1866 follows: 1868 Registry name: MUD extensions registry 1869 Registry policy: Standards action 1870 Standard reference: document 1871 Extension name: UTF-8 encoded string, not to exceed 40 characters. 1873 Each extension MUST follow the rules specified in this specification. 1874 As is usual, the IANA issues early allocations based in accordance 1875 with [RFC7120]. 1877 17. Acknowledgments 1879 The authors would like to thank Einar Nilsen-Nygaard, who 1880 singlehandedly updated the model to match the updated ACL model, 1881 Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm, 1882 John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk 1883 Birkholz, Adam Montville, and Robert Sparks for their valuable advice 1884 and reviews. Russ Housley entirely rewrote Section 10 to be a 1885 complete module. Adrian Farrel provided the basis for privacy 1886 considerations text. Kent Watsen provided a thorough review of the 1887 architecture and the YANG model. The remaining errors in this work 1888 are entirely the responsibility of the authors. 1890 18. References 1892 18.1. Normative References 1894 [I-D.ietf-netmod-acl-model] 1895 Jethanandani, M., Huang, L., Agarwal, S., and D. Blair, 1896 "Network Access Control List (ACL) YANG Data Model", 1897 draft-ietf-netmod-acl-model-18 (work in progress), March 1898 2018. 1900 [I-D.ietf-netmod-entity] 1901 Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A 1902 YANG Data Model for Hardware Management", draft-ietf- 1903 netmod-entity-08 (work in progress), January 2018. 1905 [I-D.ietf-netmod-yang-tree-diagrams] 1906 Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft- 1907 ietf-netmod-yang-tree-diagrams-06 (work in progress), 1908 February 2018. 1910 [IEEE8021AB] 1911 Institute for Electrical and Electronics Engineers, "IEEE 1912 Standard for Local and Metropolitan Area Networks-- 1913 Station and Media Access Control Connectivity Discovery", 1914 n.d.. 1916 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1917 Application and Support", STD 3, RFC 1123, 1918 DOI 10.17487/RFC1123, October 1989, 1919 . 1921 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1922 Requirement Levels", BCP 14, RFC 2119, 1923 DOI 10.17487/RFC2119, March 1997, 1924 . 1926 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1927 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1928 . 1930 [RFC2618] Aboba, B. and G. Zorn, "RADIUS Authentication Client MIB", 1931 RFC 2618, DOI 10.17487/RFC2618, June 1999, 1932 . 1934 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1935 DOI 10.17487/RFC2818, May 2000, 1936 . 1938 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1939 C., and M. Carney, "Dynamic Host Configuration Protocol 1940 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1941 2003, . 1943 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1944 Levkowetz, Ed., "Extensible Authentication Protocol 1945 (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, 1946 . 1948 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1949 Resource Identifier (URI): Generic Syntax", STD 66, 1950 RFC 3986, DOI 10.17487/RFC3986, January 2005, 1951 . 1953 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1954 Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, 1955 January 2005, . 1957 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 1958 Specifications: ABNF", STD 68, RFC 5234, 1959 DOI 10.17487/RFC5234, January 2008, 1960 . 1962 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1963 Housley, R., and W. Polk, "Internet X.509 Public Key 1964 Infrastructure Certificate and Certificate Revocation List 1965 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1966 . 1968 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, 1969 RFC 5652, DOI 10.17487/RFC5652, September 2009, 1970 . 1972 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1973 "Network Time Protocol Version 4: Protocol and Algorithms 1974 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1975 . 1977 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1978 Cheshire, "Internet Assigned Numbers Authority (IANA) 1979 Procedures for the Management of the Service Name and 1980 Transport Protocol Port Number Registry", BCP 165, 1981 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1982 . 1984 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 1985 RFC 6991, DOI 10.17487/RFC6991, July 2013, 1986 . 1988 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 1989 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 1990 2014, . 1992 [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 1993 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 1994 BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, 1995 . 1997 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1998 Protocol (HTTP/1.1): Message Syntax and Routing", 1999 RFC 7230, DOI 10.17487/RFC7230, June 2014, 2000 . 2002 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 2003 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 2004 DOI 10.17487/RFC7231, June 2014, 2005 . 2007 [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield: 2008 Protecting against Rogue DHCPv6 Servers", BCP 199, 2009 RFC 7610, DOI 10.17487/RFC7610, August 2015, 2010 . 2012 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 2013 RFC 7950, DOI 10.17487/RFC7950, August 2016, 2014 . 2016 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 2017 RFC 7951, DOI 10.17487/RFC7951, August 2016, 2018 . 2020 18.2. Informative References 2022 [FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls", 2023 January 1995. 2025 [I-D.ietf-netmod-rfc6087bis] 2026 Bierman, A., "Guidelines for Authors and Reviewers of YANG 2027 Data Model Documents", draft-ietf-netmod-rfc6087bis-20 2028 (work in progress), March 2018. 2030 [IEEE8021AR] 2031 Institute for Electrical and Electronics Engineers, 2032 "Secure Device Identity", 1998. 2034 [ISO.8601.1988] 2035 International Organization for Standardization, "Data 2036 elements and interchange formats - Information interchange 2037 - Representation of dates and times", ISO Standard 8601, 2038 June 1988. 2040 [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic 2041 Technology and the Internet", BCP 200, RFC 1984, 2042 DOI 10.17487/RFC1984, August 1996, 2043 . 2045 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 2046 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 2047 . 2049 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 2050 IETF URN Sub-namespace for Registered Protocol 2051 Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June 2052 2003, . 2054 [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security 2055 Capabilities in Customer Premises Equipment (CPE) for 2056 Providing Residential IPv6 Internet Service", RFC 6092, 2057 DOI 10.17487/RFC6092, January 2011, 2058 . 2060 [RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur, 2061 H., and O. Festor, "The Common Log Format (CLF) for the 2062 Session Initiation Protocol (SIP): Framework and 2063 Information Model", RFC 6872, DOI 10.17487/RFC6872, 2064 February 2013, . 2066 [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and 2067 IETF Protocol and Documentation Usage for IEEE 802 2068 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, 2069 October 2013, . 2071 [RFC7170] Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, 2072 "Tunnel Extensible Authentication Protocol (TEAP) Version 2073 1", RFC 7170, DOI 10.17487/RFC7170, May 2014, 2074 . 2076 [RFC7223] Bjorklund, M., "A YANG Data Model for Interface 2077 Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, 2078 . 2080 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 2081 Application Protocol (CoAP)", RFC 7252, 2082 DOI 10.17487/RFC7252, June 2014, 2083 . 2085 [RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson, 2086 "Architectural Considerations in Smart Object Networking", 2087 RFC 7452, DOI 10.17487/RFC7452, March 2015, 2088 . 2090 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 2091 Reddy, "Port Control Protocol (PCP) Server Selection", 2092 RFC 7488, DOI 10.17487/RFC7488, March 2015, 2093 . 2095 Appendix A. Changes from Earlier Versions 2097 RFC Editor to remove this section prior to publication. 2099 Draft -19: * Edits after discussion with apps area to address 2100 reserved field for the future. * Correct systeminfo to be utf8. * 2101 Remove "hardware-rev" from list. 2103 Draft -18: * Correct an error in the augment statement * Changes to 2104 the ACL model re ports. 2106 Draft -17: 2108 o One editorial. 2110 Draft -16 2112 o add mud-signature element based on review comments 2114 o redo mud-url 2116 o make clear that systeminfo uses UTF8 2118 Draft -13 to -14: 2120 o Final WGLC comments and review comments 2122 o Move version from MUD-URL to Model 2123 o Have MUD-URL in model 2125 o Update based on update to draft-ietf-netmod-acl-model 2127 o Point to tree diagram draft instead of 6087bis. 2129 Draft -12 to -13: 2131 o Additional WGLC comments 2133 Draft -10 to -12: 2135 These are based on WGLC comments: 2137 o Correct examples based on ACL model changes. 2139 o Change ordering nodes. 2141 o Additional explanatory text around systeminfo. 2143 o Change ordering in examples. 2145 o Make it VERY VERY VERY VERY clear that these are recommendations, 2146 not mandates. 2148 o DHCP -> NTP in some of the intro text. 2150 o Remove masa-server 2152 o "Things" to "network elements" in a few key places. 2154 o Reference to JSON YANG RFC added. 2156 Draft -10 to -11: 2158 o Example corrections 2160 o Typo 2162 o Fix two lists. 2164 o Addition of 'any-acl' and 'mud-acl' in the list of allowed 2165 features. 2167 o Clarification of what should be in a MUD file. 2169 Draft -09 to -10: 2171 o AD input. 2173 o Correct dates. 2175 o Add compliance sentence as to which ACL module features are 2176 implemented. 2178 Draft -08 to -09: 2180 o Resolution of Security Area review, IoT directorate review, GenART 2181 review, YANG doctors review. 2183 o change of YANG structure to address mandatory nodes. 2185 o Terminology cleanup. 2187 o specify out extra portion of MUD-URL. 2189 o consistency changes. 2191 o improved YANG descriptions. 2193 o Remove extra revisions. 2195 o Track ACL model changes. 2197 o Additional cautions on use of ACL model; further clarifications on 2198 extensions. 2200 Draft -07 to -08: 2202 o a number of editorials corrected. 2204 o definition of MUD file tweaked. 2206 Draft -06 to -07: 2208 o Examples updated. 2210 o Additional clarification for direction-initiated. 2212 o Additional implementation guidance given. 2214 Draft -06 to -07: 2216 o Update models to match new ACL model 2217 o extract directionality from the ACL, introducing a new device 2218 container. 2220 Draft -05 to -06: 2222 o Make clear that this is a component architecture (Polk and Watson) 2224 o Add order of operations (Watson) 2226 o Add extensions leaf-list (Pritikin) 2228 o Remove previous-mud-file (Watson) 2230 o Modify text in last-update (Watson) 2232 o Clarify local networks (Weis, Watson) 2234 o Fix contact info (Watson) 2236 o Terminology clarification (Weis) 2238 o Advice on how to handle LDevIDs (Watson) 2240 o Add deployment considerations (Watson) 2242 o Add some additional text about fingerprinting (Watson) 2244 o Appropriate references to 6087bis (Watson) 2246 o Change systeminfo to a URL to be referenced (Lear) 2248 Draft -04 to -05: * syntax error correction 2250 Draft -03 to -04: * Re-add my-controller 2252 Draft -02 to -03: * Additional IANA updates * Format correction in 2253 YANG. * Add reference to TEAP. 2255 Draft -01 to -02: * Update IANA considerations * Accept Russ Housley 2256 rewrite of X.509 text * Include privacy considerations text * Redo 2257 the URL limit. Still 255 bytes, but now stated in the URL 2258 definition. * Change URI registration to be under urn:ietf:params 2260 Draft -00 to -01: * Fix cert trust text. * change supportInformation 2261 to meta-info * Add an informational element in. * add urn registry 2262 and create first entry * add default elements 2264 Appendix B. Default MUD nodes 2266 What follows is the portion of a MUD file that permits DNS traffic to 2267 a controller that is registered with the URN 2268 "urn:ietf:params:mud:dns" and traffic NTP to a controller that is 2269 registered "urn:ietf:params:mud:ntp". This is considered the default 2270 behavior and the ACEs are in effect appended to whatever other "ace" 2271 entries that a MUD file contains. To block DNS or NTP one repeats 2272 the matching statement but replaces the "forwarding" action "accept" 2273 with "drop". Because ACEs are processed in the order they are 2274 received, the defaults would not be reached. A MUD controller might 2275 further decide to optimize to simply not include the defaults when 2276 they are overriden. 2278 Four "acl" list entries that implement default MUD nodes are listed 2279 below. Two are for IPv4 and two are for IPv6 (one in each direction 2280 for both versions of IP). Note that neither access-list name nor ace 2281 name need be retained or used in any way by local implementations, 2282 but are simply there for completeness' sake. 2284 "ietf-access-control-list:access-lists": { 2285 "acl": [ 2286 { 2287 "name": "mud-59776-v4to", 2288 "type": "ipv4-acl-type", 2289 "aces": { 2290 "ace": [ 2291 { 2292 "name": "ent0-todev", 2293 "matches": { 2294 "ietf-mud:mud": { 2295 "controller": "urn:ietf:params:mud:dns" 2296 }, 2297 "ipv4": { 2298 "protocol": 17 2299 }, 2300 "udp": { 2301 "source-port": { 2302 "operator": "eq", 2303 "port": 53 2304 } 2305 } 2306 }, 2307 "actions": { 2308 "forwarding": "accept" 2309 } 2310 }, 2311 { 2312 "name": "ent1-todev", 2313 "matches": { 2314 "ietf-mud:mud": { 2315 "controller": "urn:ietf:params:mud:ntp" 2316 }, 2317 "ipv4": { 2318 "protocol": 17 2319 }, 2320 "udp": { 2321 "source-port": { 2322 "operator": "eq", 2323 "port": 123 2324 } 2325 } 2326 }, 2327 "actions": { 2328 "forwarding": "accept" 2329 } 2330 } 2331 ] 2332 } 2333 }, 2334 { 2335 "name": "mud-59776-v4fr", 2336 "type": "ipv4-acl-type", 2337 "aces": { 2338 "ace": [ 2339 { 2340 "name": "ent0-frdev", 2341 "matches": { 2342 "ietf-mud:mud": { 2343 "controller": "urn:ietf:params:mud:dns" 2344 }, 2345 "ipv4": { 2346 "protocol": 17 2347 }, 2348 "udp": { 2349 "destination-port": { 2350 "operator": "eq", 2351 "port": 53 2352 } 2353 } 2354 }, 2355 "actions": { 2356 "forwarding": "accept" 2357 } 2358 }, 2359 { 2360 "name": "ent1-frdev", 2361 "matches": { 2362 "ietf-mud:mud": { 2363 "controller": "urn:ietf:params:mud:ntp" 2364 }, 2365 "ipv4": { 2366 "protocol": 17 2367 }, 2368 "udp": { 2369 "destination-port": { 2370 "operator": "eq", 2371 "port": 123 2372 } 2373 } 2374 }, 2375 "actions": { 2376 "forwarding": "accept" 2377 } 2378 } 2379 ] 2380 } 2381 }, 2382 { 2383 "name": "mud-59776-v6to", 2384 "type": "ipv6-acl-type", 2385 "aces": { 2386 "ace": [ 2387 { 2388 "name": "ent0-todev", 2389 "matches": { 2390 "ietf-mud:mud": { 2391 "controller": "urn:ietf:params:mud:dns" 2392 }, 2393 "ipv6": { 2394 "protocol": 17 2395 }, 2396 "udp": { 2397 "source-port": { 2398 "operator": "eq", 2399 "port": 53 2400 } 2401 } 2402 }, 2403 "actions": { 2404 "forwarding": "accept" 2405 } 2406 }, 2407 { 2408 "name": "ent1-todev", 2409 "matches": { 2410 "ietf-mud:mud": { 2411 "controller": "urn:ietf:params:mud:ntp" 2412 }, 2413 "ipv6": { 2414 "protocol": 17 2415 }, 2416 "udp": { 2417 "source-port": { 2418 "operator": "eq", 2419 "port": 123 2420 } 2421 } 2422 }, 2423 "actions": { 2424 "forwarding": "accept" 2425 } 2426 } 2427 ] 2428 } 2429 }, 2430 { 2431 "name": "mud-59776-v6fr", 2432 "type": "ipv6-acl-type", 2433 "aces": { 2434 "ace": [ 2435 { 2436 "name": "ent0-frdev", 2437 "matches": { 2438 "ietf-mud:mud": { 2439 "controller": "urn:ietf:params:mud:dns" 2440 }, 2441 "ipv6": { 2442 "protocol": 17 2443 }, 2444 "udp": { 2445 "destination-port": { 2446 "operator": "eq", 2447 "port": 53 2448 } 2449 } 2450 }, 2451 "actions": { 2452 "forwarding": "accept" 2453 } 2454 }, 2455 { 2456 "name": "ent1-frdev", 2457 "matches": { 2458 "ietf-mud:mud": { 2459 "controller": "urn:ietf:params:mud:ntp" 2460 }, 2461 "ipv6": { 2462 "protocol": 17 2463 }, 2464 "udp": { 2465 "destination-port": { 2466 "operator": "eq", 2467 "port": 123 2468 } 2469 } 2470 }, 2471 "actions": { 2472 "forwarding": "accept" 2473 } 2474 } 2475 ] 2476 } 2477 } 2478 ] 2479 } 2481 Appendix C. A Sample Extension: DETNET-indicator 2483 In this sample extension we augment the core MUD model to indicate 2484 whether the device implements DETNET. If a device later attempts to 2485 make use of DETNET, an notification or exception might be generated. 2486 Note that this example is intended only for illustrative purposes. 2488 Extension Name: "Example-Extension" (to be used in the extensions list) 2489 Standard: this document (but do not register the example) 2491 This extension augments the MUD model to include a single node, using 2492 the following sample module that has the following tree structure: 2494 module: ietf-mud-detext-example 2495 augment /ietf-mud:mud: 2496 +--rw is-detnet-required? boolean 2498 The model is defined as follows: 2500 file "ietf-mud-detext-example@2018-03-01.yang" 2501 module ietf-mud-detext-example { 2502 yang-version 1.1; 2503 namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example"; 2504 prefix ietf-mud-detext-example; 2506 import ietf-mud { 2507 prefix ietf-mud; 2508 } 2510 organization 2511 "IETF OPSAWG (Ops Area) Working Group"; 2512 contact 2513 "WG Web: http://tools.ietf.org/wg/opsawg/ 2514 WG List: opsawg@ietf.org 2515 Author: Eliot Lear 2516 lear@cisco.com 2517 Author: Ralph Droms 2518 rdroms@gmail.com 2519 Author: Dan Romascanu 2520 dromasca@gmail.com 2522 "; 2523 description 2524 "Sample extension to a MUD module to indicate a need 2525 for DETNET support."; 2527 revision 2018-03-01 { 2528 description 2529 "Initial revision."; 2530 reference 2531 "RFC XXXX: Manufacturer Usage Description 2532 Specification"; 2533 } 2535 augment "/ietf-mud:mud" { 2536 description 2537 "This adds a simple extension for a manufacturer 2538 to indicate whether DETNET is required by a 2539 device."; 2540 leaf is-detnet-required { 2541 type boolean; 2542 description 2543 "This value will equal true if a device requires 2544 detnet to properly function"; 2545 } 2546 } 2547 } 2548 2549 Using the previous example, we now show how the extension would be 2550 expressed: 2552 { 2553 "ietf-mud:mud": { 2554 "mud-version": 1, 2555 "mud-url": "https://lighting.example.com/lightbulb2000", 2556 "last-update": "2018-03-02T11:20:51+01:00", 2557 "cache-validity": 48, 2558 "extensions": [ 2559 "ietf-mud-detext-example" 2560 ], 2561 "ietf-mud-detext-example:is-detnet-required": "false", 2562 "is-supported": true, 2563 "systeminfo": "The BMS Example Lightbulb", 2564 "from-device-policy": { 2565 "access-lists": { 2566 "access-list": [ 2567 { 2568 "name": "mud-76100-v6fr" 2569 } 2570 ] 2571 } 2572 }, 2573 "to-device-policy": { 2574 "access-lists": { 2575 "access-list": [ 2576 { 2577 "name": "mud-76100-v6to" 2578 } 2579 ] 2580 } 2581 } 2582 }, 2583 "ietf-access-control-list:access-lists": { 2584 "acl": [ 2585 { 2586 "name": "mud-76100-v6to", 2587 "type": "ipv6-acl-type", 2588 "aces": { 2589 "ace": [ 2590 { 2591 "name": "cl0-todev", 2592 "matches": { 2593 "ipv6": { 2594 "ietf-acldns:src-dnsname": "test.com", 2595 "protocol": 6 2596 }, 2597 "tcp": { 2598 "ietf-mud:direction-initiated": "from-device", 2599 "source-port": { 2600 "operator": "eq", 2601 "port": 443 2602 } 2603 } 2604 }, 2605 "actions": { 2606 "forwarding": "accept" 2607 } 2608 } 2609 ] 2610 } 2611 }, 2612 { 2613 "name": "mud-76100-v6fr", 2614 "type": "ipv6-acl-type", 2615 "aces": { 2616 "ace": [ 2617 { 2618 "name": "cl0-frdev", 2619 "matches": { 2620 "ipv6": { 2621 "ietf-acldns:dst-dnsname": "test.com", 2622 "protocol": 6 2623 }, 2624 "tcp": { 2625 "ietf-mud:direction-initiated": "from-device", 2626 "destination-port": { 2627 "operator": "eq", 2628 "port": 443 2629 } 2630 } 2631 }, 2632 "actions": { 2633 "forwarding": "accept" 2634 } 2635 } 2636 ] 2637 } 2638 } 2639 ] 2640 } 2641 } 2643 Authors' Addresses 2645 Eliot Lear 2646 Cisco Systems 2647 Richtistrasse 7 2648 Wallisellen CH-8304 2649 Switzerland 2651 Phone: +41 44 878 9200 2652 Email: lear@cisco.com 2654 Ralph Droms 2655 Google 2656 355 Main St., 5th Floor 2657 Cambridge 2659 Phone: +1 978 376 3731 2660 Email: rdroms@gmail.com 2662 Dan Romascanu 2664 Phone: +972 54 5555347 2665 Email: dromasca@gmail.com