idnits 2.17.1 draft-ietf-opsawg-mud-15.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 1078 has weird spacing: '...ecified model...' == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: Note when using either of these with a MUD file, because access is associated with a particular Thing, MUD files MUST not contain either a src-dnsname in an ACL associated with from-device-policy or a dst-dnsname associated with to-device-policy. -- The document date (January 25, 2018) is 2276 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-21) exists of draft-ietf-netmod-acl-model-15 == Outdated reference: A later version (-06) exists of draft-ietf-netmod-yang-tree-diagrams-05 -- Possible downref: Non-RFC (?) normative reference: ref. 'IEEE8021AB' ** Obsolete normative reference: RFC 2618 (Obsoleted by RFC 4668) ** Obsolete normative reference: RFC 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 7230 (Obsoleted by RFC 9110, RFC 9112) ** Obsolete normative reference: RFC 7231 (Obsoleted by RFC 9110) == Outdated reference: A later version (-20) exists of draft-ietf-netmod-rfc6087bis-16 -- Obsolete informational reference (is this intentional?): RFC 7042 (Obsoleted by RFC 9542) -- Obsolete informational reference (is this intentional?): RFC 7223 (Obsoleted by RFC 8343) Summary: 5 errors (**), 0 flaws (~~), 6 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: July 29, 2018 6 D. Romascanu 7 January 25, 2018 9 Manufacturer Usage Description Specification 10 draft-ietf-opsawg-mud-15 12 Abstract 14 This memo specifies a component-based architecture for manufacturer 15 usage descriptions (MUD). The goal of MUD is to provide a means for 16 Things to signal to the network what sort of access and network 17 functionality they require to properly function. The initial focus 18 is on access control. Later work can delve into other aspects. 20 This memo specifies two YANG modules, IPv4 and IPv6 DHCP options, an 21 LLDP TLV, a URL suffix specification, an X.509 certificate extension 22 and a means to sign and verify the descriptions. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on July 29, 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, hardware-rev, software-rev, model-name 78 firmware-rev . . . . . . . . . . . . . . . . . . . . . . 16 79 3.8. extensions . . . . . . . . . . . . . . . . . . . . . . . 16 80 3.9. manufacturer . . . . . . . . . . . . . . . . . . . . . . 16 81 3.10. same-manufacturer . . . . . . . . . . . . . . . . . . . . 16 82 3.11. model . . . . . . . . . . . . . . . . . . . . . . . . . . 16 83 3.12. local-networks . . . . . . . . . . . . . . . . . . . . . 17 84 3.13. controller . . . . . . . . . . . . . . . . . . . . . . . 17 85 3.14. my-controller . . . . . . . . . . . . . . . . . . . . . . 17 86 3.15. direction-initiated . . . . . . . . . . . . . . . . . . . 17 87 4. Processing of the MUD file . . . . . . . . . . . . . . . . . 18 88 5. What does a MUD URL look like? . . . . . . . . . . . . . . . 18 89 6. The MUD YANG Model . . . . . . . . . . . . . . . . . . . . . 19 90 7. The Domain Name Extension to the ACL Model . . . . . . . . . 25 91 7.1. src-dnsname . . . . . . . . . . . . . . . . . . . . . . . 25 92 7.2. dst-dnsname . . . . . . . . . . . . . . . . . . . . . . . 26 93 7.3. The ietf-acldns Model . . . . . . . . . . . . . . . . . . 26 94 8. MUD File Example . . . . . . . . . . . . . . . . . . . . . . 27 95 9. The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . . 30 96 9.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 30 97 9.2. Server Behavior . . . . . . . . . . . . . . . . . . . . . 31 98 9.3. Relay Requirements . . . . . . . . . . . . . . . . . . . 31 99 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 31 100 11. The Manufacturer Usage Description LLDP extension . . . . . . 33 101 12. Creating and Processing of Signed MUD Files . . . . . . . . . 35 102 12.1. Creating a MUD file signature . . . . . . . . . . . . . 35 103 12.2. Verifying a MUD file signature . . . . . . . . . . . . . 35 104 13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 36 105 14. Deployment Considerations . . . . . . . . . . . . . . . . . . 36 106 15. Security Considerations . . . . . . . . . . . . . . . . . . . 37 107 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39 108 16.1. YANG Module Registrations . . . . . . . . . . . . . . . 39 109 16.2. DHCPv4 and DHCPv6 Options . . . . . . . . . . . . . . . 40 110 16.3. PKIX Extensions . . . . . . . . . . . . . . . . . . . . 40 111 16.4. Well Known URI Suffix . . . . . . . . . . . . . . . . . 40 112 16.5. MIME Media-type Registration for MUD files . . . . . . . 40 113 16.6. LLDP IANA TLV Subtype Registry . . . . . . . . . . . . . 41 114 16.7. The MUD Well Known Universal Resource Name (URNs) . . . 42 115 16.8. Extensions Registry . . . . . . . . . . . . . . . . . . 42 116 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42 117 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 43 118 18.1. Normative References . . . . . . . . . . . . . . . . . . 43 119 18.2. Informative References . . . . . . . . . . . . . . . . . 45 120 Appendix A. Changes from Earlier Versions . . . . . . . . . . . 47 121 Appendix B. Default MUD nodes . . . . . . . . . . . . . . . . . 50 122 Appendix C. A Sample Extension: DETNET-indicator . . . . . . . . 55 123 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 59 125 1. Introduction 127 The Internet has largely been constructed for general purpose 128 computers, those devices that may be used for a purpose that is 129 specified by those who own the device. [RFC1984] presumed that an 130 end device would be most capable of protecting itself. This made 131 sense when the typical device was a workstation or a mainframe, and 132 it continues to make sense for general purpose computing devices 133 today, including laptops, smart phones, and tablets. 135 [RFC7452] discusses design patterns for, and poses questions about, 136 smart objects. Let us then posit a group of objects that are 137 specifically not general purpose computers. These devices, which 138 this memo refers to as Things, have a specific purpose. By 139 definition, therefore, all other uses are not intended. The 140 combination of these two statements can be restated as a manufacturer 141 usage description (MUD) that can be applied at various points within 142 a network. 144 We use the notion of "manufacturer" loosely in this context to refer 145 to the entity or organization that will state how a device is 146 intended to be used. For example, in the context of a lightbulb, 147 this might indeed be the lightbulb manufacturer. In the context of a 148 smarter device that has a built in Linux stack, it might be an 149 integrator of that device. The key points are that the device itself 150 is assumed to serve a limited purpose, and that there may exist an 151 organization in the supply chain of that device that will take 152 responsibility for informing the network about that purpose. 154 The intent of MUD is to provide the following: 156 o Substantially reduce the threat surface on a device entering a 157 network to those communications intended by the manufacturer. 159 o Provide a means to scale network policies to the ever-increasing 160 number of types of devices in the network. 162 o Provide a means to address at least some vulnerabilities in a way 163 that is faster than the time it might take to update systems. 164 This will be particularly true for systems that are no longer 165 supported by their manufacturer. 167 o Keep the cost of implementation of such a system to the bare 168 minimum. 170 o Provide a means of extensibility for manufacturers to express 171 other device capabilities or requirements. 173 MUD consists of three architectural building blocks: 175 o A URL that is can be used to locate a description; 177 o The description itself, including how it is interpreted, and; 179 o A means for local network management systems to retrieve the 180 description. 182 In this specification we describe each of these building blocks and 183 how they are intended to be used together. However, they may also be 184 used separately, independent of this specification, by local 185 deployments for their own purposes. 187 1.1. What MUD Doesn't Do 189 MUD is not intended to address network authorization of general 190 purpose computers, as their manufacturers cannot envision a specific 191 communication pattern to describe. In addition, even those devices 192 that have a single or small number of uses might have very broad 193 communication patterns. MUD on its own is not for them either. 195 Although MUD can provide network administrators with some additional 196 protection when device vulnerabilities exist, it will never replace 197 the need for manufacturers to patch vulnerabilities. 199 Finally, no matter what the manufacturer specifies in a MUD file, 200 these are not directives, but suggestions. How they are instantiated 201 locally will depend on many factors and will be ultimately up to the 202 local network administrator, who must decide what is appropriate in a 203 given circumstances. 205 1.2. A Simple Example 207 A light bulb is intended to light a room. It may be remotely 208 controlled through the network, and it may make use of a rendezvous 209 service of some form that an application on a smart phone. What we 210 can say about that light bulb, then, is that all other network access 211 is unwanted. It will not contact a news service, nor speak to the 212 refrigerator, and it has no need of a printer or other devices. It 213 has no social networking friends. Therefore, an access list applied 214 to it that states that it will only connect to the single rendezvous 215 service will not impede the light bulb in performing its function, 216 while at the same time allowing the network to provide both it and 217 other devices an additional layer of protection. 219 1.3. Terminology 221 MUD: manufacturer usage description. 223 MUD file: a file containing YANG-based JSON that describes a Thing 224 and associated suggested specific network behavior. 226 MUD file server: a web server that hosts a MUD file. 228 MUD controller: the system that requests and receives the MUD file 229 from the MUD server. After it has processed a MUD file, it may 230 direct changes to relevant network elements. 232 MUD URL: a URL that can be used by the MUD controller to receive the 233 MUD file. 235 Thing: the device emitting a MUD URL. 237 Manufacturer: the entity that configures the Thing to emit the MUD 238 URL and the one who asserts a recommendation in a MUD file. The 239 manufacturer might not always be the entity that constructs a 240 Thing. It could, for instance, be a systems integrator, or even a 241 component provider. 243 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 244 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 245 document are to be interpreted as described in [RFC2119]. 247 1.4. Determining Intended Use 249 The notion of intended use is in itself not new. Network 250 administrators apply access lists every day to allow for only such 251 use. This notion of white listing was well described by Chapman and 252 Zwicky in [FW95]. Profiling systems that make use of heuristics to 253 identify types of systems have existed for years as well. 255 A Thing could just as easily tell the network what sort of access it 256 requires without going into what sort of system it is. This would, 257 in effect, be the converse of [RFC7488]. In seeking a general 258 purpose solution, however, we assume that a device has so few 259 capabilities that it will implement the least necessary capabilities 260 to function properly. This is a basic economic constraint. Unless 261 the network would refuse access to such a device, its developers 262 would have no reason to provide the network any information. To 263 date, such an assertion has held true. 265 1.5. Finding A Policy: The MUD URL 267 Our work begins with the device emitting a Universal Resource Locator 268 (URL) [RFC3986]. This URL serves both to classify the device type 269 and to provide a means to locate a policy file. 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 URLs MUST use the HTTPS scheme [RFC7230]. 304 MUD controllers that are able to do so SHOULD retrieve MUD URLs and 305 signature files as per [RFC7230], using the GET method [RFC7231]. 306 They MUST validate the certificate using the rules in [RFC2618], 307 Section 3.1. 309 Requests for MUD URLs SHOULD include an "Accept" header ([RFC7231], 310 Section 5.3.2) containing "application/mud+json", an "Accept- 311 Language" header ([RFC7231], Section 5.3.5), and a "User-Agent" 312 header ([RFC7231], Section 5.5.3). 314 MUD controllers SHOULD automatically process 3xx response status 315 codes. 317 If a MUD controller is not able to fetch a MUD URL, other means MAY 318 be used to import MUD files and associated signature files. So long 319 as the signature of the file can be validated, the file can be used. 320 In such environments, controllers SHOULD warn administrators when 321 cache-validity expiry is approaching so that they may check for new 322 files. 324 1.7. Types of Policies 326 When the MUD URL is resolved, the MUD controller retrieves a file 327 that describes what sort of communications a device is designed to 328 have. The manufacturer may specify either specific hosts for cloud 329 based services or certain classes for access within an operational 330 network. An example of a class might be "devices of a specified 331 manufacturer type", where the manufacturer type itself is indicated 332 simply by the authority component (e.g, the domain name) of the MUD 333 URL. Another example might be to allow or disallow local access. 334 Just like other policies, these may be combined. For example: 336 o Allow access to devices of the same manufacturer 338 o Allow access to and from controllers via Constrained Application 339 Protocol (COAP)[RFC7252] 341 o Allow access to local DNS/NTP 343 o Deny all other access 345 A printer might have a description that states: 347 o Allow access for port IPP or port LPD 349 o Allow local access for port HTTP 351 o Deny all other access 353 In this way anyone can print to the printer, but local access would 354 be required for the management interface. 356 The files that are retrieved are intended to be closely aligned to 357 existing network architectures so that they are easy to deploy. We 358 make use of YANG [RFC7950] because of the time and effort spent to 359 develop accurate and adequate models for use by network devices. 360 JSON is used as a serialization for compactness and readability, 361 relative to XML. Other formats may be chosen with later versions of 362 MUD. 364 While the policy examples given here focus on access control, this is 365 not intended to be the sole focus. By structuring the model 366 described in this document with clear extension points, other 367 descriptions could be included. One that often comes to mind is 368 quality of service. 370 The YANG modules specified here are extensions of 371 [I-D.ietf-netmod-acl-model]. The extensions to this model allow for 372 a manufacturer to express classes of systems that a manufacturer 373 would find necessary for the proper function of the device. Two 374 modules are specified. The first module specifies a means for domain 375 names to be used in ACLs so that devices that have their controllers 376 in the cloud may be appropriately authorized with domain names, where 377 the mapping of those names to addresses may rapidly change. 379 The other module abstracts away IP addresses into certain classes 380 that are instantiated into actual IP addresses through local 381 processing. Through these classes, manufacturers can specify how the 382 device is designed to communicate, so that network elements can be 383 configured by local systems that have local topological knowledge. 385 That is, the deployment populates the classes that the manufacturer 386 specifies. The abstractions below map to zero or more hosts, as 387 follows: 389 Manufacturer: A device made by a particular manufacturer, as 390 identified by the authority component of its MUD URL 392 same-manufacturer: Devices that have the same authority component of 393 their MUD URL. 395 controller: Devices that the local network administrator admits to 396 the particular class. 398 my-controller: Devices associated with the MUD URL of a device that 399 the administrator admits. 401 local: The class of IP addresses that are scoped within some 402 administrative boundary. By default it is suggested that this be 403 the local subnet. 405 The "manufacturer" classes can be easily specified by the 406 manufacturer, whereas controller classes are initially envisioned to 407 be specified by the administrator. 409 Because manufacturers do not know who will be using their devices, it 410 is important for functionality referenced in usage descriptions to be 411 relatively ubiquitous and mature. For these reasons only a limited 412 subset YANG-based configuration is permitted in a MUD file. 414 1.8. The Manufacturer Usage Description Architecture 416 With these components laid out we now have the basis for an 417 architecture. This leads us to ASCII art. 419 ....................................... 420 . ____________ . _____________ 421 . | | . | | 422 . | MUD |-->get URL-->| MUD | 423 . | Controller | .(https) | File Server | 424 . End system network |____________|<-MUD file<-<|_____________| 425 . . . 426 . . . 427 . _______ _________ . 428 .| | (dhcp et al) | router | . 429 .| Thing |---->MUD URL-->| or | . 430 .|_______| | switch | . 431 . |_________| . 432 ....................................... 434 Figure 1: MUD Architecture 436 In the above diagram, the switch or router collects MUD URLs and 437 forwards them to the MUD controller (a network management system) for 438 processing. This happens in different ways, depending on how the URL 439 is communicated. For instance, in the case of DHCP, the DHCP server 440 might receive the URL and then process it. In the case of IEEE 441 802.1X, the switch would carry the URL via a certificate to the 442 authentication server via EAP over Radius[RFC3748], which would then 443 process it. One method to do this is TEAP, described in [RFC7170]. 444 The certificate extension is described below. 446 The information returned by the MUD file server (a web server) is 447 valid for the duration of the Thing's connection, or as specified in 448 the description. Thus if the Thing is disconnected, any associated 449 configuration in the switch can be removed. Similarly, from time to 450 time the description may be refreshed, based on new capabilities or 451 communication patterns or vulnerabilities. 453 The web site is typically run by or on behalf of the manufacturer. 454 Its domain name is that of the authority found in the MUD URL. For 455 legacy cases where Things cannot emit a URL, if the switch is able to 456 determine the appropriate URL, it may proxy it, the trivial cases 457 being a hardcoded MUD-URL on a switch port, or a mapping from some 458 available identifier such as an L2 address or certificate hash to a 459 MUD-URL. 461 The role of the MUD controller in this environment is to do the 462 following: 464 o receive MUD URLs, 466 o fetch MUD files, 467 o translate abstractions in the MUD files to specific network 468 element configuration, 470 o maintain and update any required mappings of the abstractions, and 472 o update network elements with appropriate configuration. 474 A MUD controller may be a component of a AAA or network management 475 system. Communication within those systems and from those systems to 476 network elements is beyond the scope of this memo. 478 1.9. Order of operations 480 As mentioned above, MUD contains architectural building blocks, and 481 so order of operation may vary. However, here is one clear intended 482 example: 484 1. Thing emits URL. 486 2. That URL is forwarded to a MUD controller by the nearest switch 487 (how this happens depends on the way in which the MUD URL is 488 emitted). 490 3. The MUD controller retrieves the MUD file and signature from the 491 MUD file server, assuming it doesn't already have copies. After 492 validating the signature, it may test the URL against a web or 493 domain reputation service, and it may test any hosts within the 494 file against those reputation services, as it deems fit. 496 4. The MUD controller may query the administrator for permission to 497 add the Thing and associated policy. If the Thing is known or 498 the Thing type is known, it may skip this step. 500 5. The MUD controller instantiates local configuration based on the 501 abstractions defined in this document. 503 6. The MUD controller configures the switch nearest the Thing. 504 Other systems may be configured as well. 506 7. When the Thing disconnects, policy is removed. 508 2. The MUD Model and Semantic Meaning 510 A MUD file consists of a YANG model that has been serialized in JSON 511 [RFC7951]. For purposes of MUD, the nodes that can be modified are 512 access lists as augmented by this model. The MUD file is limited to 513 the serialization of only the following YANG schema: 515 o ietf-access-control-list [I-D.ietf-netmod-acl-model] 517 o ietf-mud (this document) 519 o ietf-acldns (this document) 521 Extensions may be used to add additional schema. This is described 522 further on. 524 To provide the widest possible deployment, publishers of MUD files 525 SHOULD make use of the abstractions in this memo and avoid the use of 526 IP addresses. A MUD controller SHOULD NOT automatically implement 527 any MUD file that contains IP addresses, especially those that might 528 have local significance. The addressing of one side of an access 529 list is implicit, based on whether it is applied as to-device-policy 530 or from-device-policy. 532 With the exceptions of "name" of the ACL, "type", "name" of the ACE, 533 and TCP and UDP source and destination port information, publishers 534 of MUD files SHOULD limit the use of ACL model leaf nodes expressed 535 to those found in this specification. Absent any extensions, MUD 536 files are assumed to implement only the following ACL model features: 538 o match-on-ipv4, match-on-ipv6, match-on-tcp, match-on-udp, match- 539 on-icmp 541 Furthermore, only "accept" or "drop" actions SHOULD be included. A 542 MUD controller MAY choose to interpret "reject" as "drop". A MUD 543 controller SHOULD ignore all other actions. This is because 544 manufacturers do not have sufficient context within a local 545 deployment to know whether reject is appropriate. That is a decision 546 that should be left to a network administrator. 548 Given that MUD does not deal with interfaces, the support of the 549 "ietf-interfaces" module [RFC7223] is not required. Specifically, 550 the support of interface-related features and branches (e.g., 551 interface-attachment and interface-stats) of the ACL YANG module is 552 not required. 554 In fact, MUD controllers MAY ignore any particular component of a 555 description or MAY ignore the description in its entirety, and SHOULD 556 carefully inspect all MUD descriptions. Publishers of MUD files MUST 557 NOT include other nodes except as described in Section 3.8. See that 558 section for more information. 560 2.1. The IETF-MUD YANG Module 562 This module is structured into three parts: 564 o The first container "mud" holds information that is relevant to 565 retrieval and validity of the MUD file itself, as well as policy 566 intended to and from the Thing. 568 o The second component augments the matching container of the ACL 569 model to add several nodes that are relevant to the MUD URL, or 570 otherwise abstracted for use within a local environment. 572 o The third component augments the tcp-acl container of the ACL 573 model to add the ability to match on the direction of initiation 574 of a TCP connection. 576 A valid MUD file will contain two root objects, a "mud" container and 577 an "access-lists" container. Extensions may add additional root 578 objects as required. As a reminder, when parsing access-lists, 579 elements within a "match" block are logically ANDed. In general, a 580 single abstraction in a match statement should be used. For 581 instance, it makes little sense to match both "my-controller" and 582 "controller" with an argument, since they are highly unlikely to be 583 the same value. 585 A simplified graphical representation of the data models is used in 586 this document. The meaning of the symbols in these diagrams is 587 explained in [I-D.ietf-netmod-yang-tree-diagrams]. 589 module: ietf-mud 590 +--rw mud! 591 +--rw mud-version uint8 592 +--rw mud-url inet:uri 593 +--rw last-update yang:date-and-time 594 +--rw cache-validity? uint8 595 +--rw is-supported boolean 596 +--rw systeminfo? inet:uri 597 +--rw mfg-name? string 598 +--rw model-name? string 599 +--rw firmware-rev? string 600 +--rw software-rev? string 601 +--rw extensions* string 602 +--rw from-device-policy 603 | +--rw access-lists 604 | +--rw access-list* [name] 605 | +--rw name -> /acl:access-lists/acl/name 606 +--rw to-device-policy 607 +--rw access-lists 608 +--rw access-list* [name] 609 +--rw name -> /acl:access-lists/acl/name 610 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches: 611 +--rw mud 612 +--rw manufacturer? inet:host 613 +--rw same-manufacturer? empty 614 +--rw model? inet:uri 615 +--rw local-networks? empty 616 +--rw controller? inet:uri 617 +--rw my-controller? empty 618 augment /acl:access-lists/acl:acl/acl:aces/acl:ace 619 /acl:matches/acl:l4/acl:tcp: 620 +--rw direction-initiated? direction 622 3. Data Node Definitions 624 Note that in this section, when we use the term "match" we are 625 referring to the ACL model "matches" node. 627 The following nodes are defined. 629 3.1. mud-version 631 This node specifies the integer version of the MUD specification. 632 This memo specifies version 1. 634 3.2. to-device-policy and from-device-policy containers 636 [I-D.ietf-netmod-acl-model] describes access-lists. In the case of 637 MUD, a MUD file must be explicit in describing the communication 638 pattern of a Thing, and that includes indicating what is to be 639 permitted or denied in either direction of communication. Hence each 640 of these containers indicates the appropriate direction of a flow in 641 association with a particular Thing. They contain references to 642 specific access-lists. 644 3.3. last-update 646 This is a date-and-time value of when the MUD file was generated. 647 This is akin to a version number. Its form is taken from [RFC6991] 648 which, for those keeping score, in turn was taken from Section 5.6 of 649 [RFC3339], which was taken from [ISO.8601.1988]. 651 3.4. cache-validity 653 This uint8 is the period of time in hours that a network management 654 station MUST wait since its last retrieval before checking for an 655 update. It is RECOMMENDED that this value be no less than 24 and 656 MUST NOT be more than 168 for any Thing that is supported. This 657 period SHOULD be no shorter than any period determined through HTTP 658 caching directives (e.g., "cache-control" or "Expires"). N.B., 659 expiring of this timer does not require the MUD controller to discard 660 the MUD file, nor terminate access to a Thing. See Section 15 for 661 more information. 663 3.5. is-supported 665 This boolean is an indication from the manufacturer to the network 666 administrator as to whether or not the Thing is supported. In this 667 context a Thing is said to not be supported if the manufacturer 668 intends never to issue an update to the Thing or never update the MUD 669 file. A MUD controller MAY still periodically check for updates. 671 3.6. systeminfo 673 This is a URL that points to a description of the Thing to be 674 connected. The intent is for administrators to be able to see a 675 localized name associated with the Thing. The referenced URL SHOULD 676 be a localized display string, and MAY be in either HTML or a raw 677 UTF-8 text file. It SHOULD NOT exceed 60 characters worth of display 678 space (that is- what the administrator actually sees), but it MAY 679 contain links to other documents (presumably product documentation). 681 3.7. mfg-name, hardware-rev, software-rev, model-name firmware-rev 683 These optional fields are filled in as specified by 684 [I-D.ietf-netmod-entity]. Note that firmware-rev and software-rev 685 MUST NOT be populated in a MUD file if the device can be upgraded but 686 the MUD-URL cannot be. This would be the case, for instance, with 687 MUR-URLs that are contained in 802.1AR certificates. 689 3.8. extensions 691 This optional leaf-list names MUD extensions that are used in the MUD 692 file. Note that NO MUD extensions may be used in a MUD file without 693 the extensions being declared. Implementations MUST ignore any node 694 in this file that they do not understand. 696 Note that extensions can either extend the MUD file as described in 697 the previous paragraph, or they might reference other work. An 698 extension example can be found in Appendix C. 700 3.9. manufacturer 702 This node consists of a hostname that would be matched against the 703 authority component of another Thing's MUD URL. In its simplest form 704 "manufacturer" and "same-manufacturer" may be implemented as access- 705 lists. In more complex forms, additional network capabilities may be 706 used. For example, if one saw the line "manufacturer" : 707 "flobbidy.example.com", then all Things that registered with a MUD 708 URL that contained flobbity.example.com in its authority section 709 would match. 711 3.10. same-manufacturer 713 This null-valued node is an equivalent for when the manufacturer 714 element is used to indicate the authority that is found in another 715 Thing's MUD URL matches that of the authority found in this Thing's 716 MUD URL. For example, if the Thing's MUD URL were 717 https://b1.example.com/.well-known/mud/ThingV1, then all devices that 718 had MUD URL with an authority section of b1.example.com would match. 720 3.11. model 722 This string matches the entire MUD URL, thus covering the model that 723 is unique within the context of the authority. It may contain not 724 only model information, but versioning information as well, and any 725 other information that the manufacturer wishes to add. The intended 726 use is for devices of this precise class to match, to permit or deny 727 communication between one another. 729 3.12. local-networks 731 This null-valued node expands to include local networks. Its default 732 expansion is that packets must not traverse toward a default route 733 that is received from the router. However, administrators may expand 734 the expression as is appropriate in their deployments. 736 3.13. controller 738 This URI specifies a value that a controller will register with the 739 MUD controller. The node then is expanded to the set of hosts that 740 are so registered. This node may also be a URN. In this case, the 741 URN describes a well known service, such as DNS or NTP. 743 Great care should be used when invoking the controller class. For 744 one thing, it requires some understanding by the administrator as to 745 when it is appropriate. Classes that are standardized may make it 746 possible to easily name devices that support standard functions. For 747 instance, the MUD controller could have some knowledge of which DNS 748 servers should be used for any particular group of Things. Non- 749 standard classes will likely require some sort of administrator 750 interaction. Pre-registration in such classes by controllers with 751 the MUD server is encouraged. The mechanism to do that is beyond the 752 scope of this work. 754 Controller URIs MAY take the form of a URL (e.g. "http[s]://"). 755 However, MUD controllers MUST NOT resolve and retrieve such files, 756 and it is RECOMMENDED that there be no such file at this time, as 757 their form and function may be defined at a point in the future. For 758 now, URLs should serve simply as class names and may be populated by 759 the local deployment administrator. 761 3.14. my-controller 763 This null-valued node signals to the MUD controller to use whatever 764 mapping it has for this MUD URL to a particular group of hosts. This 765 may require prompting the administrator for class members. Future 766 work should seek to automate membership management. 768 3.15. direction-initiated 770 When applied this matches packets when the flow was initiated in the 771 corresponding direction. [RFC6092] specifies IPv6 guidance best 772 practices. While that document is scoped specifically to IPv6, its 773 contents are applicable for IPv4 as well. When this flag is set, and 774 the system has no reason to believe a flow has been initiated it MUST 775 drop the packet. This node may be implemented in its simplest form 776 by looking at naked SYN bits, but may also be implemented through 777 more stateful mechanisms. 779 4. Processing of the MUD file 781 To keep things relatively simple in addition to whatever definitions 782 exist, we also apply two additional default behaviors: 784 o Anything not explicitly permitted is denied. 786 o Local DNS and NTP are, by default, permitted to and from the 787 Thing. 789 An explicit description of the defaults can be found in Appendix B. 790 These are applied AFTER all other explicit rules. Thus, a default 791 behavior can be changed with a "drop" action. 793 5. What does a MUD URL look like? 795 To begin with, MUD takes full advantage of both the https: scheme and 796 the use of .well-known. HTTPS is important in this case because a 797 man in the middle attack could otherwise harm the operation of a 798 class of Things. .well-known is used because we wish to add 799 additional structure to the URL, and want to leave open for future 800 versions both the means by which the URL is processed and the format 801 of the MUD file retrieved (there have already been some discussions 802 along these lines). The URL appears as follows: 804 mud-url = "https://" authority "/.well-known/mud/" 805 "/" modelinfo ( "?" extras ) 806 ; authority is from RFC3986 807 modelinfo = segment ; from RFC3986 808 extras = query ; from RFC3986 810 Taken together with the mud-url, "modelinfo" represents a Thing model 811 as the manufacturer wishes to represent it. It could be a brand name 812 or something more specific. It also may provide a means to indicate 813 what version the product is. Specifically if it has been updated in 814 the field, this is the place where evidence of that update would 815 appear. The field should be changed when the intended communication 816 patterns of a Thing change. While from a controller standpoint, only 817 comparison and matching operations are safe, it is envisioned that 818 updates will require some administrative review. 820 "extras" is intended for use by the MUD controller to provide 821 additional information such as posture about the Thing to the MUD 822 file server. This field MUST NOT be configured on the Thing itself 823 by a manufacturer - that is what "modelinfo" is for. It is left as 824 future work to define the full semantics of this field. 826 6. The MUD YANG Model 828 file "ietf-mud@2018-01-24.yang" 829 module ietf-mud { 830 yang-version 1.1; 831 namespace "urn:ietf:params:xml:ns:yang:ietf-mud"; 832 prefix ietf-mud; 834 import ietf-access-control-list { 835 prefix acl; 836 } 837 import ietf-yang-types { 838 prefix yang; 839 } 840 import ietf-inet-types { 841 prefix inet; 842 } 844 organization 845 "IETF OPSAWG (Ops Area) Working Group"; 846 contact 847 "WG Web: http://tools.ietf.org/wg/opsawg/ 848 WG List: opsawg@ietf.org 849 Author: Eliot Lear 850 lear@cisco.com 851 Author: Ralph Droms 852 rdroms@gmail.com 853 Author: Dan Romascanu 854 dromasca@gmail.com 856 "; 857 description 858 "This YANG module defines a component that augments the 859 IETF description of an access list. This specific module 860 focuses on additional filters that include local, model, 861 and same-manufacturer. 863 This module is intended to be serialized via JSON and stored 864 as a file, as described in RFC XXXX [RFC Editor to fill in with 865 this document #]. 867 Copyright (c) 2016,2017 IETF Trust and the persons 868 identified as the document authors. All rights reserved. 869 Redistribution and use in source and binary forms, with or 870 without modification, is permitted pursuant to, and subject 871 to the license terms contained in, the Simplified BSD 872 License set forth in Section 4.c of the IETF Trust's Legal 873 Provisions Relating to IETF Documents 874 (http://trustee.ietf.org/license-info). 875 This version of this YANG module is part of RFC XXXX; see 876 the RFC itself for full legal notices."; 878 revision 2018-01-24 { 879 description 880 "Initial proposed standard."; 881 reference 882 "RFC XXXX: Manufacturer Usage Description 883 Specification"; 884 } 886 typedef direction { 887 type enumeration { 888 enum "to-device" { 889 description 890 "packets or flows destined to the target 891 Thing"; 892 } 893 enum "from-device" { 894 description 895 "packets or flows destined from 896 the target Thing"; 897 } 898 } 899 description 900 "Which way are we talking about?"; 901 } 903 container mud { 904 presence "Enabled for this particular MUD URL"; 905 description 906 "MUD related information, as specified 907 by RFC-XXXX [RFC Editor to fill in]."; 908 uses mud-grouping; 909 } 911 grouping mud-grouping { 912 description 913 "Information about when support end(ed), and 914 when to refresh"; 916 leaf mud-version { 917 type uint8; 918 mandatory true; 919 description "This is the version of the MUD 920 specification. This memo specifies version 1."; 921 } 923 leaf mud-url { 924 type inet:uri; 925 mandatory true; 926 description 927 "This is the MUD URL associated with the entry found 928 in a MUD file."; 929 } 930 leaf last-update { 931 type yang:date-and-time; 932 mandatory true; 933 description 934 "This is intended to be when the current MUD file 935 was generated. MUD Controllers SHOULD NOT check 936 for updates between this time plus cache validity"; 937 } 938 leaf cache-validity { 939 type uint8 { 940 range "1..168"; 941 } 942 units "hours"; 943 default "48"; 944 description 945 "The information retrieved from the MUD server is 946 valid for these many hours, after which it should 947 be refreshed. N.B. MUD controller implementations 948 need not discard MUD files beyond this period."; 949 } 950 leaf is-supported { 951 type boolean; 952 mandatory true; 953 description 954 "This boolean indicates whether or not the Thing is 955 currently supported by the manufacturer."; 956 } 957 leaf systeminfo { 958 type inet:uri; 959 description 960 "A URL to a description of this Thing. This 961 should be a brief localized description. The 962 reference text should be no more than octets. 963 systeminfo may be displayed to the user to 964 determine whether to allow the Thing on the 965 network."; 967 } 969 leaf mfg-name { 970 type string; 971 description "Manufacturer name, as described in 972 the ietf-hardware yang module."; 973 } 975 leaf model-name { 976 type string; 977 description "Model name, as described in the 978 ietf-hardware yang module."; 979 } 981 leaf firmware-rev { 982 type string; 983 description "firmware-rev, as described in the 984 ietf-hardware yang module. Note this field MUST 985 NOT be included when the device can be updated 986 but the MUD-URL cannot."; 987 } 989 leaf software-rev { 990 type string; 991 description "software-rev, as described in the 992 ietf-hardware yang module. Note this field MUST 993 NOT be included when the device can be updated 994 but the MUD-URL cannot."; 995 } 997 leaf-list extensions { 998 type string { 999 length "1..40"; 1000 } 1001 description 1002 "A list of extension names that are used in this MUD 1003 file. Each name is registered with the IANA and 1004 described in an RFC."; 1005 } 1006 container from-device-policy { 1007 description 1008 "The policies that should be enforced on traffic 1009 coming from the device. These policies are not 1010 necessarily intended to be enforced at a single 1011 point, but may be rendered by the controller to any 1012 relevant enorcement points in the network or 1013 elsewhere."; 1014 uses access-lists; 1016 } 1017 container to-device-policy { 1018 description 1019 "The policies that should be enforced on traffic 1020 going to the device. These policies are not 1021 necessarily intended to be enforced at a single 1022 point, but may be rendered by the controller to any 1023 relevant enorcement points in the network or 1024 elsewhere."; 1025 uses access-lists; 1026 } 1027 } 1029 grouping access-lists { 1030 description 1031 "A grouping for access lists in the context of device 1032 policy."; 1033 container access-lists { 1034 description 1035 "The access lists that should be applied to traffic 1036 to or from the device."; 1037 list access-list { 1038 key "name"; 1039 description 1040 "Each entry on this list refers to an ACL that 1041 should be present in the overall access list 1042 data model. Each ACL is identified by name and 1043 type."; 1044 leaf name { 1045 type leafref { 1046 path "/acl:access-lists/acl:acl/acl:name"; 1047 } 1048 description 1049 "The name of the ACL for this entry."; 1050 } 1051 } 1052 } 1053 } 1054 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches" { 1055 description 1056 "adding abstractions to avoid need of IP addresses"; 1057 container mud { 1058 description 1059 "MUD-specific matches."; 1060 leaf manufacturer { 1061 type inet:host; 1062 description 1063 "A domain that is intended to match the authority 1064 section of the MUD URL. This node is used to specify 1065 one or more manufacturers a device should 1066 be authorized to access."; 1067 } 1068 leaf same-manufacturer { 1069 type empty; 1070 description 1071 "This node matches the authority section of the MUD URL 1072 of a Thing. It is intended to grant access to all 1073 devices with the same authority section."; 1074 } 1075 leaf model { 1076 type inet:uri; 1077 description 1078 "Devices of the specified model type will match if 1079 they have an identical MUD URL."; 1080 } 1081 leaf local-networks { 1082 type empty; 1083 description 1084 "IP addresses will match this node if they are 1085 considered local addresses. A local address may be 1086 a list of locally defined prefixes and masks 1087 that indicate a particular administrative scope."; 1088 } 1089 leaf controller { 1090 type inet:uri; 1091 description 1092 "This node names a class that has associated with it 1093 zero or more IP addresses to match against. These 1094 may be scoped to a manufacturer or via a standard 1095 URN."; 1096 } 1097 leaf my-controller { 1098 type empty; 1099 description 1100 "This node matches one or more network elements that 1101 have been configured to be the controller for this 1102 Thing, based on its MUD URL."; 1103 } 1104 } 1105 } 1106 augment "/acl:access-lists/acl:acl/acl:aces/" + 1107 "acl:ace/acl:matches/acl:l4/acl:tcp" { 1108 description 1109 "Adding domain names to matching"; 1110 leaf direction-initiated { 1111 type direction; 1112 description 1113 "This node matches based on which direction a 1114 connection was initiated. The means by which that 1115 is determined is discussed in this document."; 1116 } 1117 } 1118 } 1120 1122 7. The Domain Name Extension to the ACL Model 1124 This module specifies an extension to IETF-ACL model such that domain 1125 names may be referenced by augmenting the "matches" node. Different 1126 implementations may deploy differing methods to maintain the mapping 1127 between IP address and domain name, if indeed any are needed. 1128 However, the intent is that resources that are referred to using a 1129 name should be authorized (or not) within an access list. 1131 The structure of the change is as follows: 1133 module: ietf-acldns 1134 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches 1135 /acl:l3/acl:ipv4: 1136 +--rw src-dnsname? inet:host 1137 +--rw dst-dnsname? inet:host 1138 augment /acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches 1139 /acl:l3/acl:ipv6: 1140 +--rw src-dnsname? inet:host 1141 +--rw dst-dnsname? inet:host 1143 The choice of these particular points in the access-list model is 1144 based on the assumption that we are in some way referring to IP- 1145 related resources, as that is what the DNS returns. A domain name in 1146 our context is defined in [RFC6991]. The augmentations are 1147 replicated across IPv4 and IPv6 to allow MUD file authors the ability 1148 to control the IP version that the Thing may utilize. 1150 The following node are defined. 1152 7.1. src-dnsname 1154 The argument corresponds to a domain name of a source as specified by 1155 inet:host. A number of means may be used to resolve hosts. What is 1156 important is that such resolutions be consistent with ACLs required 1157 by Things to properly operate. 1159 7.2. dst-dnsname 1161 The argument corresponds to a domain name of a destination as 1162 specified by inet:host See the previous section relating to 1163 resolution. 1165 Note when using either of these with a MUD file, because access is 1166 associated with a particular Thing, MUD files MUST not contain either 1167 a src-dnsname in an ACL associated with from-device-policy or a dst- 1168 dnsname associated with to-device-policy. 1170 7.3. The ietf-acldns Model 1172 file "ietf-acldns@2018-01-24.yang" 1173 module ietf-acldns { 1174 yang-version 1.1; 1175 namespace "urn:ietf:params:xml:ns:yang:ietf-acldns"; 1176 prefix "ietf-acldns"; 1178 import ietf-access-control-list { 1179 prefix "acl"; 1180 } 1182 import ietf-inet-types { 1183 prefix "inet"; 1184 } 1186 organization 1187 "IETF OPSAWG (Ops Area) Working Group"; 1189 contact 1190 "WG Web: http://tools.ietf.org/wg/opsawg/ 1191 WG List: opsawg@ietf.org 1192 Author: Eliot Lear 1193 lear@cisco.com 1194 Author: Ralph Droms 1195 rdroms@gmail.com 1196 Author: Dan Romascanu 1197 dromasca@gmail.com 1198 "; 1200 description 1201 "This YANG module defines a component that augments the 1202 IETF description of an access list to allow dns names 1203 as matching criteria."; 1205 revision "2018-01-24" { 1206 description "Base version of dnsname extension of ACL model"; 1207 reference "RFC XXXX: Manufacturer Usage Description 1208 Specification"; 1209 } 1211 grouping dns-matches { 1212 description "Domain names for matching."; 1214 leaf src-dnsname { 1215 type inet:host; 1216 description "domain name to be matched against"; 1217 } 1218 leaf dst-dnsname { 1219 type inet:host; 1220 description "domain name to be matched against"; 1221 } 1222 } 1224 augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/" + 1225 "acl:matches/acl:l3/acl:ipv4" { 1226 description "Adding domain names to matching"; 1227 uses dns-matches; 1228 } 1230 augment "/acl:access-lists/acl:acl/" + 1231 "acl:aces/acl:ace/" + 1232 "acl:matches/acl:l3/acl:ipv6" { 1233 description "Adding domain names to matching"; 1234 uses dns-matches; 1235 } 1236 } 1237 1239 8. MUD File Example 1241 This example contains two access lists that are intended to provide 1242 outbound access to a cloud service on TCP port 443. 1244 { 1245 "ietf-mud:mud": { 1246 "mud-version": 1, 1247 "mud-url": "https://bms.example.com/.well-known/mud/lightbulb2000", 1248 "last-update": "2018-01-24T16:08:58+01:00", 1249 "cache-validity": 48, 1250 "is-supported": true, 1251 "systeminfo": "The BMS Example Lightbulb", 1252 "from-device-policy": { 1253 "access-lists": { 1254 "access-list": [ 1255 { 1256 "name": "mud-61898-v6fr" 1257 } 1258 ] 1259 } 1260 }, 1261 "to-device-policy": { 1262 "access-lists": { 1263 "access-list": [ 1264 { 1265 "name": "mud-61898-v6to" 1266 } 1267 ] 1268 } 1269 } 1270 }, 1271 "ietf-access-control-list:access-lists": { 1272 "acl": [ 1273 { 1274 "name": "mud-61898-v6to", 1275 "type": "ipv6-acl-type", 1276 "aces": { 1277 "ace": [ 1278 { 1279 "name": "cl0-todev", 1280 "matches": { 1281 "l3": { 1282 "ipv6": { 1283 "ietf-acldns:src-dnsname": "service.bms.example.com", 1284 "protocol": 6 1285 } 1286 }, 1287 "l4": { 1288 "tcp": { 1289 "ietf-mud:direction-initiated": "from-device", 1290 "source-port-range-or-operator": { 1291 "operator": "eq", 1292 "port": 443 1293 } 1294 } 1295 } 1296 }, 1297 "actions": { 1298 "forwarding": "accept" 1299 } 1300 } 1301 ] 1303 } 1304 }, 1305 { 1306 "name": "mud-61898-v6fr", 1307 "type": "ipv6-acl-type", 1308 "aces": { 1309 "ace": [ 1310 { 1311 "name": "cl0-frdev", 1312 "matches": { 1313 "l3": { 1314 "ipv6": { 1315 "ietf-acldns:dst-dnsname": "service.bms.example.com", 1316 "protocol": 6 1317 } 1318 }, 1319 "l4": { 1320 "tcp": { 1321 "ietf-mud:direction-initiated": "from-device", 1322 "destination-port-range-or-operator": { 1323 "operator": "eq", 1324 "port": 443 1325 } 1326 } 1327 } 1328 }, 1329 "actions": { 1330 "forwarding": "accept" 1331 } 1332 } 1333 ] 1334 } 1335 } 1336 ] 1337 } 1338 } 1340 In this example, two policies are declared, one from the Thing and 1341 the other to the Thing. Each policy names an access list that 1342 applies to the Thing, and one that applies from. Within each access 1343 list, access is permitted to packets flowing to or from the Thing 1344 that can be mapped to the domain name of "service.bms.example.com". 1345 For each access list, the enforcement point should expect that the 1346 Thing initiated the connection. 1348 9. The MUD URL DHCP Option 1350 The IPv4 MUD URL client option has the following format: 1352 +------+-----+------------------------------ 1353 | code | len | MUD URL 1354 +------+-----+------------------------------ 1356 Code OPTION_MUD_URL_V4 (161) is assigned by IANA. len is a single 1357 octet that indicates the length of the URL in octets. MUD URL is a 1358 URL. MUD URLs MUST NOT exceed 255 octets. 1360 The IPv6 MUD URL client option has the following format: 1362 0 1 2 3 1363 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 1364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1365 | OPTION_MUD_URL_V6 | option-length | 1366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1367 | MUD URL | 1368 | ... | 1369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1371 OPTION_MUD_URL_V6 (112; assigned by IANA). 1373 option-length contains the length of the URL in octets. 1375 The intent of this option is to provide both a new Thing classifier 1376 to the network as well as some recommended configuration to the 1377 routers that implement policy. However, it is entirely the purview 1378 of the network system as managed by the network administrator to 1379 decide what to do with this information. The key function of this 1380 option is simply to identify the type of Thing to the network in a 1381 structured way such that the policy can be easily found with existing 1382 toolsets. 1384 9.1. Client Behavior 1386 A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit 1387 DHCPv6 option. These options are singletons, as specified in 1388 [RFC7227]. Because clients are intended to have at most one MUD URL 1389 associated with them, they may emit at most one MUD URL option via 1390 DHCPv4 and one MUD URL option via DHCPv6. In the case where both v4 1391 and v6 DHCP options are emitted, the same URL MUST be used. 1393 Clients SHOULD log or otherwise report improper acknowledgments from 1394 servers, but they MUST NOT modify their MUD URL configuration based 1395 on a server's response. The server's response is only an 1396 acknowledgment that the server has processed the option, and promises 1397 no specific network behavior to the client. In particular, it may 1398 not be possible for the server to retrieve the file associated with 1399 the MUD URL, or the local network administration may not wish to use 1400 the usage description. Neither of these situations should be 1401 considered in any way exceptional. 1403 9.2. Server Behavior 1405 A DHCP server may ignore these options or take action based on 1406 receipt of these options. If a server successfully parses the option 1407 and the URL, it MUST return the option with length field set to zero 1408 and a corresponding null URL field as an acknowledgment. Even in 1409 this circumstance, no specific network behavior is guaranteed. When 1410 a server consumes this option, it will either forward the URL and 1411 relevant client information (such as the gateway address or giaddr) 1412 to a network management system, or it will retrieve the usage 1413 description itself by resolving the URL. 1415 DHCP servers may implement MUD functionality themselves or they may 1416 pass along appropriate information to a network management system or 1417 MUD controller. A DHCP server that does process the MUD URL MUST 1418 adhere to the process specified in [RFC2818] and [RFC5280] to 1419 validate the TLS certificate of the web server hosting the MUD file. 1420 Those servers will retrieve the file, process it, create and install 1421 the necessary configuration on the relevant network element. Servers 1422 SHOULD monitor the gateway for state changes on a given interface. A 1423 DHCP server that does not provide MUD functionality and has forwarded 1424 a MUD URL to a MUD controller MUST notify the MUD controller of any 1425 corresponding change to the DHCP state of the client (such as 1426 expiration or explicit release of a network address lease). 1428 9.3. Relay Requirements 1430 There are no additional requirements for relays. 1432 10. The Manufacturer Usage Description (MUD) URL X.509 Extension 1434 This section defines an X.509 non-critical certificate extension that 1435 contains a single Uniform Resource Locator (URL) that points to an 1436 on-line Manufacturer Usage Description concerning the certificate 1437 subject. URI must be represented as described in Section 7.4 of 1438 [RFC5280]. 1440 Any Internationalized Resource Identifiers (IRIs) MUST be mapped to 1441 URIs as specified in Section 3.1 of [RFC3987] before they are placed 1442 in the certificate extension. 1444 The semantics of the URL are defined Section 5 of this document. 1446 The choice of id-pe is based on guidance found in Section 4.2.2 of 1447 [RFC5280]: 1449 These extensions may be used to direct applications to on-line 1450 information about the issuer or the subject. 1452 The MUD URL is precisely that: online information about the 1453 particular subject. 1455 The new extension is identified as follows: 1457 1459 MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) 1460 internet(1) security(5) mechanisms(5) pkix(7) 1461 id-mod(0) id-mod-mudURLExtn2016(88) } 1463 DEFINITIONS IMPLICIT TAGS ::= BEGIN 1465 -- EXPORTS ALL -- 1467 IMPORTS 1468 EXTENSION 1469 FROM PKIX-CommonTypes-2009 1470 { iso(1) identified-organization(3) dod(6) internet(1) 1471 security(5) mechanisms(5) pkix(7) id-mod(0) 1472 id-mod-pkixCommon-02(57) } 1474 id-pe 1475 FROM PKIX1Explicit-2009 1476 { iso(1) identified-organization(3) dod(6) internet(1) 1477 security(5) mechanisms(5) pkix(7) id-mod(0) 1478 id-mod-pkix1-explicit-02(51) } ; 1479 MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... } 1480 ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax 1481 IDENTIFIED BY id-pe-mud-url } 1483 id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 } 1485 MUDURLSyntax ::= IA5String 1487 END 1489 1491 While this extension can appear in either an 802.AR manufacturer 1492 certificate (IDevID) or deployment certificate (LDevID), of course it 1493 is not guaranteed in either, nor is it guaranteed to be carried over. 1494 It is RECOMMENDED that MUD controller implementations maintain a 1495 table that maps a Thing to its MUD URL based on IDevIDs. 1497 11. The Manufacturer Usage Description LLDP extension 1499 The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop 1500 vendor-neutral link layer protocol used by end hosts network Things 1501 for advertising their identity, capabilities, and neighbors on an 1502 IEEE 802 local area network. Its Type-Length-Value (TLV) design 1503 allows for 'vendor-specific' extensions to be defined. IANA has a 1504 registered IEEE 802 organizationally unique identifier (OUI) defined 1505 as documented in [RFC7042]. The MUD LLDP extension uses a subtype 1506 defined in this document to carry the MUD URL. 1508 The LLDP vendor specific frame has the following format: 1510 +--------+--------+----------+---------+-------------- 1511 |TLV Type| len | OUI |subtype | MUD URL 1512 | =127 | |= 00 00 5E| = 1 | 1513 |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets) 1514 +--------+--------+----------+---------+-------------- 1516 where: 1518 o TLV Type = 127 indicates a vendor-specific TLV 1520 o len - indicates the TLV string length 1522 o OUI = 00 00 5E is the organizationally unique identifier of IANA 1524 o subtype = 1 (to be assigned by IANA for the MUD URL) 1526 o MUD URL - the length MUST NOT exceed 255 octets 1528 The intent of this extension is to provide both a new Thing 1529 classifier to the network as well as some recommended configuration 1530 to the routers that implement policy. However, it is entirely the 1531 purview of the network system as managed by the network administrator 1532 to decide what to do with this information. The key function of this 1533 extension is simply to identify the type of Thing to the network in a 1534 structured way such that the policy can be easily found with existing 1535 toolsets. 1537 Hosts, routers, or other network elements that implement this option 1538 are intended to have at most one MUD URL associated with them, so 1539 they may transmit at most one MUD URL value. 1541 Hosts, routers, or other network elements that implement this option 1542 may ignore these options or take action based on receipt of these 1543 options. For example they may fill in information in the respective 1544 extensions of the LLDP Management Information Base (LLDP MIB). LLDP 1545 operates in a one-way direction. LLDPDUs are not exchanged as 1546 information requests by one Thing and response sent by another Thing. 1547 The other Things do not acknowledge LLDP information received from a 1548 Thing. No specific network behavior is guaranteed. When a Thing 1549 consumes this extension, it may either forward the URL and relevant 1550 remote Thing information to a MUD controller, or it will retrieve the 1551 usage description by resolving the URL in accordance with normal HTTP 1552 semantics. 1554 12. Creating and Processing of Signed MUD Files 1556 Because MUD files contain information that may be used to configure 1557 network access lists, they are sensitive. To insure that they have 1558 not been tampered with, it is important that they be signed. We make 1559 use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for 1560 this purpose. 1562 12.1. Creating a MUD file signature 1564 A MUD file MUST be signed using CMS as an opaque binary object. In 1565 order to make successful verification more likely, intermediate 1566 certificates SHOULD be included. The signature is stored at the same 1567 location as the MUD URL but with the suffix of ".p7s". Signatures 1568 are transferred using content-type "application/pkcs7-signature". 1570 For example: 1572 % openssl cms -sign -signer mancertfile -inkey mankey \ 1573 -in mudfile -binary -outform DER - \ 1574 -certfile intermediatecert -out mudfile.p7s 1576 Note: A MUD file may need to be re-signed if the signature expires. 1578 12.2. Verifying a MUD file signature 1580 Prior to retrieving a MUD file the MUD controller SHOULD retrieve the 1581 MUD signature file using the MUD URL with a suffix of ".p7s". For 1582 example, if the MUD URL is "https://example.com/.well-known/modela", 1583 the MUD signature URL will be "https://example.com/.well-known/ 1584 modela.p7s". 1586 Upon retrieving a MUD file, a MUD controller MUST validate the 1587 signature of the file before continuing with further processing. A 1588 MUD controller MUST cease processing of that file it cannot validate 1589 the chain of trust to a known trust anchor until an administrator has 1590 given approval. 1592 The purpose of the signature on the file is to assign accountability 1593 to an entity, whose reputation can be used to guide administrators on 1594 whether or not to accept a given MUD file. It is already common 1595 place to check web reputation on the location of a server on which a 1596 file resides. While it is likely that the manufacturer will be the 1597 signer of the file, this is not strictly necessary, and may not be 1598 desirable. For one thing, in some environments, integrators may 1599 install their own certificates. For another, what is more important 1600 is the accountability of the recommendation, and not the 1601 cryptographic relationship between the device and the file. 1603 An example: 1605 % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile 1607 Note the additional step of verifying the common trust root. 1609 13. Extensibility 1611 One of our design goals is to see that MUD files are able to be 1612 understood by as broad a cross-section of systems as is possible. 1613 Coupled with the fact that we have also chosen to leverage existing 1614 mechanisms, we are left with no ability to negotiate extensions and a 1615 limited desire for those extensions in any event. A such, a two-tier 1616 extensibility framework is employed, as follows: 1618 1. At a coarse grain, a protocol version is included in a MUD URL. 1619 This memo specifies MUD version 1. Any and all changes are 1620 entertained when this version is bumped. Transition approaches 1621 between versions would be a matter for discussion in future 1622 versions. 1624 2. At a finer grain, only extensions that would not incur additional 1625 risk to the Thing are permitted. Specifically, adding nodes to 1626 the mud container is permitted with the understanding that such 1627 additions will be ignored by unaware implementations. Any such 1628 extensions SHALL be standardized through the IETF process, and 1629 MUST be named in the "extensions" list. MUD controllers MUST 1630 ignore YANG nodes they do not understand and SHOULD create an 1631 exception to be resolved by an administrator, so as to avoid any 1632 policy inconsistencies. 1634 14. Deployment Considerations 1636 Because MUD consists of a number of architectural building blocks, it 1637 is possible to assemble different deployment scenarios. One key 1638 aspect is where to place policy enforcement. In order to protect the 1639 Thing from other Things within a local deployment, policy can be 1640 enforced on the nearest switch or access point. In order to limit 1641 unwanted traffic within a network, it may also be advisable to 1642 enforce policy as close to the Internet as possible. In some 1643 circumstances, policy enforcement may not be available at the closest 1644 hop. At that point, the risk of so-called east-west infection is 1645 increased to the number of Things that are able to communicate 1646 without protection. 1648 A caution about some of the classes: admission of a Thing into the 1649 "manufacturer" and "same-manufacturer" class may have impact on 1650 access of other Things. Put another way, the admission may grow the 1651 access-list on switches connected to other Things, depending on how 1652 access is managed. Some care should be given on managing that 1653 access-list growth. Alternative methods such as additional network 1654 segmentation can be used to keep that growth within reason. 1656 Because as of this writing MUD is a new concept, one can expect a 1657 great many devices to not have implemented it. It remains a local 1658 deployment decision as to whether a device that is first connected 1659 should be alloewed broad or limited access. Furthermore, as 1660 mentioned in the introduction, a deployment may choose to ignore a 1661 MUD policy in its entirety, but simply taken into account the MUD URL 1662 as a classifier to be used as part of a local policy decision. 1664 15. Security Considerations 1666 Based on how a MUD URL is emitted, a Thing may be able to lie about 1667 what it is, thus gaining additional network access. There are 1668 several means to limit risk in this case. The most obvious is to 1669 only believe Things that make use of certificate-based authentication 1670 such as IEEE 802.1AR certificates. When those certificates are not 1671 present, Things claiming to be of a certain manufacturer SHOULD NOT 1672 be included in that manufacturer grouping without additional 1673 validation of some form. This will occur when it makes use of 1674 primitives such as "manufacturer" for the purpose of accessing Things 1675 of a particular type. Similarly, network management systems may be 1676 able to fingerprint the Thing. In such cases, the MUD URL can act as 1677 a classifier that can be proven or disproven. Fingerprinting may 1678 have other advantages as well: when 802.1AR certificates are used, 1679 because they themselves cannot change, fingerprinting offers the 1680 opportunity to add artificats to the MUD URL. The meaning of such 1681 artifacts is left as future work. 1683 Network management systems SHOULD NOT accept a usage description for 1684 a Thing with the same MAC address that has indicated a change of 1685 authority without some additional validation (such as review by a 1686 network administrator). New Things that present some form of 1687 unauthenticated MUD URL SHOULD be validated by some external means 1688 when they would be otherwise be given increased network access. 1690 It may be possible for a rogue manufacturer to inappropriately 1691 exercise the MUD file parser, in order to exploit a vulnerability. 1692 There are three recommended approaches to address this threat. The 1693 first is to validate the signature of the MUD file. The second is to 1694 have a system do a primary scan of the file to ensure that it is both 1695 parseable and believable at some level. MUD files will likely be 1696 relatively small, to start with. The number of ACEs used by any 1697 given Thing should be relatively small as well. It may also be 1698 useful to limit retrieval of MUD URLs to only those sites that are 1699 known to have decent web or domain reputations. 1701 Use of a URL necessitates the use of domain names. If a domain name 1702 changes ownership, the new owner of that domain may be able to 1703 provide MUD files that MUD controllers would consider valid. There 1704 are a few approaches that can mitigate this attack. First, MUD 1705 controllers SHOULD cache certificates used by the MUD file server. 1706 When a new certificate is retrieved for whatever reason, the MUD 1707 controller should check to see if ownership of the domain has 1708 changed. A fair programmatic approximation of this is when the name 1709 servers for the domain have changed. If the actual MUD file has 1710 changed, the controller MAY check the WHOIS database to see if 1711 registration ownership of a domain has changed. If a change has 1712 occured, or if for some reason it is not possible to determine 1713 whether ownership has changed, further review may be warranted. 1714 Note, this remediation does not take into account the case of a Thing 1715 that was produced long ago and only recently fielded, or the case 1716 where a new MUD controller has been installed. 1718 It may not be possible for a MUD controller to retrieve a MUD file at 1719 any given time. Should a MUD controller fail to retrieve a MUD file, 1720 it SHOULD consider the existing one safe to use, at least for a time. 1721 After some period, it SHOULD log that it has been unable to retrieve 1722 the file. There may be very good reasons for such failures, 1723 including the possibility that the MUD controller is in an off-line 1724 environment, the local Internet connection has failed, or the remote 1725 Internet connection has failed. It is also possible that an attacker 1726 is attempting to prevent onboarding of a device. It is a local 1727 deployment decision as to whether or not devices may be onboarded in 1728 the face of such failures. 1730 The release of a MUD URL by a Thing reveals what the Thing is, and 1731 provides an attacker with guidance on what vulnerabilities may be 1732 present. 1734 While the MUD URL itself is not intended to be unique to a specific 1735 Thing, the release of the URL may aid an observer in identifying 1736 individuals when combined with other information. This is a privacy 1737 consideration. 1739 In addressing both of these concerns, implementors should take into 1740 account what other information they are advertising through 1741 mechanisms such as mDNS[RFC6872], how a Thing might otherwise be 1742 identified, perhaps through how it behaves when it is connected to 1743 the network, whether a Thing is intended to be used by individuals or 1744 carry personal identifying information, and then apply appropriate 1745 data minimization techniques. One approach is to make use of TEAP 1746 [RFC7170] as the means to share information with authorized 1747 components in the network. Network elements may also assist in 1748 limiting access to the MUD URL through the use of mechanisms such as 1749 DHCPv6-Shield [RFC7610]. 1751 Please note that the security considerations mentioned in Section 4.7 1752 of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case 1753 because the YANG serialization is not intended to be accessed via 1754 NETCONF. However, for those who try to instantiate this model in a 1755 network element via NETCONF, all objects in each model in this draft 1756 exhibit similar security characteristics as 1757 [I-D.ietf-netmod-acl-model]. The basic purpose of MUD is to 1758 configure access, and so by its very nature can be disruptive if used 1759 by unauthorized parties. 1761 16. IANA Considerations 1763 16.1. YANG Module Registrations 1765 The following YANG modules are requested to be registred in the "IANA 1766 Module Names" registry: 1768 The ietf-mud module: 1770 o Name: ietf-mud 1772 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud 1774 o Prefix: ief-mud 1776 o Reference: This memo 1778 The ietf-acldns module: 1780 o Name: ietf-acldns 1782 o XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns 1784 o Prefix: ietf-acldns 1786 o Reference: This memo 1788 16.2. DHCPv4 and DHCPv6 Options 1790 The IANA has allocated option 161 in the Dynamic Host Configuration 1791 Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry 1792 for the MUD DHCPv4 option, and option 112 for DHCPv6, as described in 1793 Section 9. 1795 16.3. PKIX Extensions 1797 IANA is kindly requested to make the following assignments for: 1799 o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for 1800 PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). 1802 o id-pe-mud-url object identifier from the "SMI Security for PKIX 1803 Certificate Extension" registry (1.3.6.1.5.5.7.1). 1805 The use of these values is specified in Section 10. 1807 16.4. Well Known URI Suffix 1809 The IANA has allocated the URL suffix of "mud" as follows: 1811 o URI Suffix: "mud" o Specification documents: this document o 1812 Related information: n/a 1814 16.5. MIME Media-type Registration for MUD files 1816 The following media-type is defined for transfer of MUD file: 1818 o Type name: application 1819 o Subtype name: mud+json 1820 o Required parameters: n/a 1821 o Optional parameters: n/a 1822 o Encoding considerations: 8bit; application/mud+json values 1823 are represented as a JSON object; UTF-8 encoding SHOULD be 1824 employed. 1825 o Security considerations: See Security Considerations 1826 of this document. 1827 o Interoperability considerations: n/a 1828 o Published specification: this document 1829 o Applications that use this media type: MUD controllers as 1830 specified by this document. 1831 o Fragment identifier considerations: n/a 1832 o Additional information: 1834 Magic number(s): n/a 1835 File extension(s): n/a 1836 Macintosh file type code(s): n/a 1838 o Person & email address to contact for further information: 1839 Eliot Lear , Ralph Droms 1840 o Intended usage: COMMON 1841 o Restrictions on usage: none 1842 o Author: 1843 Eliot Lear 1844 Ralph Droms 1845 o Change controller: IESG 1846 o Provisional registration? (standards tree only): No. 1848 16.6. LLDP IANA TLV Subtype Registry 1850 IANA is requested to create a new registry for IANA Link Layer 1851 Discovery Protocol (LLDP) TLV subtype values. The recommended policy 1852 for this registry is Expert Review. The maximum number of entries in 1853 the registry is 256. 1855 IANA is required to populate the initial registry with the value: 1857 LLDP subtype value = 1 (All the other 255 values should be initially 1858 marked as 'Unassigned'.) 1860 Description = the Manufacturer Usage Description (MUD) Uniform 1861 Resource Locator (URL) 1863 Reference = < this document > 1865 16.7. The MUD Well Known Universal Resource Name (URNs) 1867 The following parameter registry is requested to be added in 1868 accordance with [RFC3553] 1870 Registry name: "urn:ietf:params:mud" is requested. 1871 Specification: this document 1872 Repository: this document 1873 Index value: Encoded identically to a TCP/UDP port service 1874 name, as specified in Section 5.1 of [RFC6335] 1876 The following entries should be added to the "urn:ietf:params:mud" 1877 name space: 1879 "urn:ietf:params:mud:dns" refers to the service specified by 1880 [RFC1123]. "urn:ietf:params:mud:ntp" refers to the service specified 1881 by [RFC5905]. 1883 16.8. Extensions Registry 1885 The IANA is requested to establish a registry of extensions as 1886 follows: 1888 Registry name: MUD extensions registry 1889 Registry policy: Standards action 1890 Standard reference: document 1891 Extension name: UTF-8 encoded string, not to exceed 40 characters. 1893 Each extension MUST follow the rules specified in this specification. 1894 As is usual, the IANA issues early allocations based in accordance 1895 with [RFC7120]. 1897 17. Acknowledgments 1899 The authors would like to thank Einar Nilsen-Nygaard, who 1900 singlehandedly updated the model to match the updated ACL model, 1901 Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm, 1902 John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk 1903 Birkholz, Adam Montville, and Robert Sparks for their valuable advice 1904 and reviews. Russ Housley entirely rewrote Section 10 to be a 1905 complete module. Adrian Farrel provided the basis for privacy 1906 considerations text. Kent Watsen provided a thorough review of the 1907 architecture and the YANG model. The remaining errors in this work 1908 are entirely the responsibility of the authors. 1910 18. References 1912 18.1. Normative References 1914 [I-D.ietf-netmod-acl-model] 1915 Jethanandani, M., Huang, L., Agarwal, S., and D. Blair, 1916 "Network Access Control List (ACL) YANG Data Model", 1917 draft-ietf-netmod-acl-model-15 (work in progress), January 1918 2018. 1920 [I-D.ietf-netmod-entity] 1921 Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A 1922 YANG Data Model for Hardware Management", draft-ietf- 1923 netmod-entity-08 (work in progress), January 2018. 1925 [I-D.ietf-netmod-yang-tree-diagrams] 1926 Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft- 1927 ietf-netmod-yang-tree-diagrams-05 (work in progress), 1928 January 2018. 1930 [IEEE8021AB] 1931 Institute for Electrical and Electronics Engineers, "IEEE 1932 Standard for Local and Metropolitan Area Networks-- 1933 Station and Media Access Control Connectivity Discovery", 1934 n.d.. 1936 [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - 1937 Application and Support", STD 3, RFC 1123, 1938 DOI 10.17487/RFC1123, October 1989, 1939 . 1941 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1942 Requirement Levels", BCP 14, RFC 2119, 1943 DOI 10.17487/RFC2119, March 1997, 1944 . 1946 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1947 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1948 . 1950 [RFC2618] Aboba, B. and G. Zorn, "RADIUS Authentication Client MIB", 1951 RFC 2618, DOI 10.17487/RFC2618, June 1999, 1952 . 1954 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1955 DOI 10.17487/RFC2818, May 2000, 1956 . 1958 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 1959 C., and M. Carney, "Dynamic Host Configuration Protocol 1960 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 1961 2003, . 1963 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1964 Levkowetz, Ed., "Extensible Authentication Protocol 1965 (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, 1966 . 1968 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1969 Resource Identifier (URI): Generic Syntax", STD 66, 1970 RFC 3986, DOI 10.17487/RFC3986, January 2005, 1971 . 1973 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1974 Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, 1975 January 2005, . 1977 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1978 Housley, R., and W. Polk, "Internet X.509 Public Key 1979 Infrastructure Certificate and Certificate Revocation List 1980 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 1981 . 1983 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, 1984 RFC 5652, DOI 10.17487/RFC5652, September 2009, 1985 . 1987 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 1988 "Network Time Protocol Version 4: Protocol and Algorithms 1989 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 1990 . 1992 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1993 Cheshire, "Internet Assigned Numbers Authority (IANA) 1994 Procedures for the Management of the Service Name and 1995 Transport Protocol Port Number Registry", BCP 165, 1996 RFC 6335, DOI 10.17487/RFC6335, August 2011, 1997 . 1999 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 2000 RFC 6991, DOI 10.17487/RFC6991, July 2013, 2001 . 2003 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 2004 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 2005 2014, . 2007 [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and 2008 S. Krishnan, "Guidelines for Creating New DHCPv6 Options", 2009 BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, 2010 . 2012 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 2013 Protocol (HTTP/1.1): Message Syntax and Routing", 2014 RFC 7230, DOI 10.17487/RFC7230, June 2014, 2015 . 2017 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 2018 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 2019 DOI 10.17487/RFC7231, June 2014, 2020 . 2022 [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield: 2023 Protecting against Rogue DHCPv6 Servers", BCP 199, 2024 RFC 7610, DOI 10.17487/RFC7610, August 2015, 2025 . 2027 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 2028 RFC 7950, DOI 10.17487/RFC7950, August 2016, 2029 . 2031 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 2032 RFC 7951, DOI 10.17487/RFC7951, August 2016, 2033 . 2035 18.2. Informative References 2037 [FW95] Chapman, D. and E. Zwicky, "Building Internet Firewalls", 2038 January 1995. 2040 [I-D.ietf-netmod-rfc6087bis] 2041 Bierman, A., "Guidelines for Authors and Reviewers of YANG 2042 Data Model Documents", draft-ietf-netmod-rfc6087bis-16 2043 (work in progress), January 2018. 2045 [IEEE8021AR] 2046 Institute for Electrical and Electronics Engineers, 2047 "Secure Device Identity", 1998. 2049 [ISO.8601.1988] 2050 International Organization for Standardization, "Data 2051 elements and interchange formats - Information interchange 2052 - Representation of dates and times", ISO Standard 8601, 2053 June 1988. 2055 [RFC1984] IAB and IESG, "IAB and IESG Statement on Cryptographic 2056 Technology and the Internet", BCP 200, RFC 1984, 2057 DOI 10.17487/RFC1984, August 1996, 2058 . 2060 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 2061 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 2062 . 2064 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 2065 IETF URN Sub-namespace for Registered Protocol 2066 Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June 2067 2003, . 2069 [RFC6092] Woodyatt, J., Ed., "Recommended Simple Security 2070 Capabilities in Customer Premises Equipment (CPE) for 2071 Providing Residential IPv6 Internet Service", RFC 6092, 2072 DOI 10.17487/RFC6092, January 2011, 2073 . 2075 [RFC6872] Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur, 2076 H., and O. Festor, "The Common Log Format (CLF) for the 2077 Session Initiation Protocol (SIP): Framework and 2078 Information Model", RFC 6872, DOI 10.17487/RFC6872, 2079 February 2013, . 2081 [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and 2082 IETF Protocol and Documentation Usage for IEEE 802 2083 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, 2084 October 2013, . 2086 [RFC7170] Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, 2087 "Tunnel Extensible Authentication Protocol (TEAP) Version 2088 1", RFC 7170, DOI 10.17487/RFC7170, May 2014, 2089 . 2091 [RFC7223] Bjorklund, M., "A YANG Data Model for Interface 2092 Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, 2093 . 2095 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 2096 Application Protocol (CoAP)", RFC 7252, 2097 DOI 10.17487/RFC7252, June 2014, 2098 . 2100 [RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson, 2101 "Architectural Considerations in Smart Object Networking", 2102 RFC 7452, DOI 10.17487/RFC7452, March 2015, 2103 . 2105 [RFC7488] Boucadair, M., Penno, R., Wing, D., Patil, P., and T. 2106 Reddy, "Port Control Protocol (PCP) Server Selection", 2107 RFC 7488, DOI 10.17487/RFC7488, March 2015, 2108 . 2110 Appendix A. Changes from Earlier Versions 2112 RFC Editor to remove this section prior to publication. 2114 Draft -13 to -14: 2116 o Final WGLC comments and review comments 2118 o Move version from MUD-URL to Model 2120 o Have MUD-URL in model 2122 o Update based on update to draft-ietf-netmod-acl-model 2124 o Point to tree diagram draft instead of 6087bis. 2126 Draft -12 to -13: 2128 o Additional WGLC comments 2130 Draft -10 to -12: 2132 These are based on WGLC comments: 2134 o Correct examples based on ACL model changes. 2136 o Change ordering nodes. 2138 o Additional explanatory text around systeminfo. 2140 o Change ordering in examples. 2142 o Make it VERY VERY VERY VERY clear that these are recommendations, 2143 not mandates. 2145 o DHCP -> NTP in some of the intro text. 2147 o Remove masa-server 2148 o "Things" to "network elements" in a few key places. 2150 o Reference to JSON YANG RFC added. 2152 Draft -10 to -11: 2154 o Example corrections 2156 o Typo 2158 o Fix two lists. 2160 o Addition of 'any-acl' and 'mud-acl' in the list of allowed 2161 features. 2163 o Clarification of what should be in a MUD file. 2165 Draft -09 to -10: 2167 o AD input. 2169 o Correct dates. 2171 o Add compliance sentence as to which ACL module features are 2172 implemented. 2174 Draft -08 to -09: 2176 o Resolution of Security Area review, IoT directorate review, GenART 2177 review, YANG doctors review. 2179 o change of YANG structure to address mandatory nodes. 2181 o Terminology cleanup. 2183 o specify out extra portion of MUD-URL. 2185 o consistency changes. 2187 o improved YANG descriptions. 2189 o Remove extra revisions. 2191 o Track ACL model changes. 2193 o Additional cautions on use of ACL model; further clarifications on 2194 extensions. 2196 Draft -07 to -08: 2198 o a number of editorials corrected. 2200 o definition of MUD file tweaked. 2202 Draft -06 to -07: 2204 o Examples updated. 2206 o Additional clarification for direction-initiated. 2208 o Additional implementation guidance given. 2210 Draft -06 to -07: 2212 o Update models to match new ACL model 2214 o extract directionality from the ACL, introducing a new device 2215 container. 2217 Draft -05 to -06: 2219 o Make clear that this is a component architecture (Polk and Watson) 2221 o Add order of operations (Watson) 2223 o Add extensions leaf-list (Pritikin) 2225 o Remove previous-mud-file (Watson) 2227 o Modify text in last-update (Watson) 2229 o Clarify local networks (Weis, Watson) 2231 o Fix contact info (Watson) 2233 o Terminology clarification (Weis) 2235 o Advice on how to handle LDevIDs (Watson) 2237 o Add deployment considerations (Watson) 2239 o Add some additional text about fingerprinting (Watson) 2241 o Appropriate references to 6087bis (Watson) 2243 o Change systeminfo to a URL to be referenced (Lear) 2244 Draft -04 to -05: * syntax error correction 2246 Draft -03 to -04: * Re-add my-controller 2248 Draft -02 to -03: * Additional IANA updates * Format correction in 2249 YANG. * Add reference to TEAP. 2251 Draft -01 to -02: * Update IANA considerations * Accept Russ Housley 2252 rewrite of X.509 text * Include privacy considerations text * Redo 2253 the URL limit. Still 255 bytes, but now stated in the URL 2254 definition. * Change URI registration to be under urn:ietf:params 2256 Draft -00 to -01: * Fix cert trust text. * change supportInformation 2257 to meta-info * Add an informational element in. * add urn registry 2258 and create first entry * add default elements 2260 Appendix B. Default MUD nodes 2262 What follows is the portion of a MUD file that permits DNS traffic to 2263 a controller that is registered with the URN 2264 "urn:ietf:params:mud:dns" and traffic NTP to a controller that is 2265 registered "urn:ietf:params:mud:ntp". This is considered the default 2266 behavior and the ACEs are in effect appended to whatever other "ace" 2267 entries that a MUD file contains. To block DNS or NTP one repeats 2268 the matching statement but replaces the "forwarding" action "accept" 2269 with "drop". Because ACEs are processed in the order they are 2270 received, the defaults would not be reached. A MUD controller might 2271 further decide to optimize to simply not include the defaults when 2272 they are overriden. 2274 Four "acl" list entries that implement default MUD nodes are listed 2275 below. Two are for IPv4 and two are for IPv6 (one in each direction 2276 for both versions of IP). Note that neither access-list name nor ace 2277 name need be retained or used in any way by local implementations, 2278 but are simply there for completeness' sake. 2280 "ietf-access-control-list:access-lists": { 2281 "acl": [ 2282 { 2283 "name": "mud-76295-v4to", 2284 "type": "ipv4-acl-type", 2285 "aces": { 2286 "ace": [ 2287 { 2288 "name": "ent0-todev", 2289 "matches": { 2290 "ietf-mud:mud": { 2291 "controller": "urn:ietf:params:mud:dns" 2293 }, 2294 "l3": { 2295 "ipv4": { 2296 "protocol": 17 2297 } 2298 }, 2299 "l4": { 2300 "udp": { 2301 "source-port-range-or-operator": { 2302 "operator": "eq", 2303 "port": 53 2304 } 2305 } 2306 } 2307 }, 2308 "actions": { 2309 "forwarding": "accept" 2310 } 2311 }, 2312 { 2313 "name": "ent1-todev", 2314 "matches": { 2315 "ietf-mud:mud": { 2316 "controller": "urn:ietf:params:mud:ntp" 2317 }, 2318 "l3": { 2319 "ipv4": { 2320 "protocol": 17 2321 } 2322 }, 2323 "l4": { 2324 "udp": { 2325 "source-port-range-or-operator": { 2326 "operator": "eq", 2327 "port": 123 2328 } 2329 } 2330 } 2331 }, 2332 "actions": { 2333 "forwarding": "accept" 2334 } 2335 } 2336 ] 2337 } 2338 }, 2339 { 2340 "name": "mud-76295-v4fr", 2341 "type": "ipv4-acl-type", 2342 "aces": { 2343 "ace": [ 2344 { 2345 "name": "ent0-frdev", 2346 "matches": { 2347 "ietf-mud:mud": { 2348 "controller": "urn:ietf:params:mud:dns" 2349 }, 2350 "l3": { 2351 "ipv4": { 2352 "protocol": 17 2353 } 2354 }, 2355 "l4": { 2356 "udp": { 2357 "destination-port-range-or-operator": { 2358 "operator": "eq", 2359 "port": 53 2360 } 2361 } 2362 } 2363 }, 2364 "actions": { 2365 "forwarding": "accept" 2366 } 2367 }, 2368 { 2369 "name": "ent1-frdev", 2370 "matches": { 2371 "ietf-mud:mud": { 2372 "controller": "urn:ietf:params:mud:ntp" 2373 }, 2374 "l3": { 2375 "ipv4": { 2376 "protocol": 17 2377 } 2378 }, 2379 "l4": { 2380 "udp": { 2381 "destination-port-range-or-operator": { 2382 "operator": "eq", 2383 "port": 123 2384 } 2385 } 2386 } 2387 }, 2388 "actions": { 2389 "forwarding": "accept" 2390 } 2391 } 2392 ] 2393 } 2394 }, 2395 { 2396 "name": "mud-76295-v6to", 2397 "type": "ipv6-acl-type", 2398 "aces": { 2399 "ace": [ 2400 { 2401 "name": "ent0-todev", 2402 "matches": { 2403 "ietf-mud:mud": { 2404 "controller": "urn:ietf:params:mud:dns" 2405 }, 2406 "l3": { 2407 "ipv6": { 2408 "protocol": 17 2409 } 2410 }, 2411 "l4": { 2412 "udp": { 2413 "source-port-range-or-operator": { 2414 "operator": "eq", 2415 "port": 53 2416 } 2417 } 2418 } 2419 }, 2420 "actions": { 2421 "forwarding": "accept" 2422 } 2423 }, 2424 { 2425 "name": "ent1-todev", 2426 "matches": { 2427 "ietf-mud:mud": { 2428 "controller": "urn:ietf:params:mud:ntp" 2429 }, 2430 "l3": { 2431 "ipv6": { 2432 "protocol": 17 2433 } 2434 }, 2435 "l4": { 2436 "udp": { 2437 "source-port-range-or-operator": { 2438 "operator": "eq", 2439 "port": 123 2440 } 2441 } 2442 } 2443 }, 2444 "actions": { 2445 "forwarding": "accept" 2446 } 2447 } 2448 ] 2449 } 2450 }, 2451 { 2452 "name": "mud-76295-v6fr", 2453 "type": "ipv6-acl-type", 2454 "aces": { 2455 "ace": [ 2456 { 2457 "name": "ent0-frdev", 2458 "matches": { 2459 "ietf-mud:mud": { 2460 "controller": "urn:ietf:params:mud:dns" 2461 }, 2462 "l3": { 2463 "ipv6": { 2464 "protocol": 17 2465 } 2466 }, 2467 "l4": { 2468 "udp": { 2469 "destination-port-range-or-operator": { 2470 "operator": "eq", 2471 "port": 53 2472 } 2473 } 2474 } 2475 }, 2476 "actions": { 2477 "forwarding": "accept" 2478 } 2479 }, 2480 { 2481 "name": "ent1-frdev", 2482 "matches": { 2483 "ietf-mud:mud": { 2484 "controller": "urn:ietf:params:mud:ntp" 2486 }, 2487 "l3": { 2488 "ipv6": { 2489 "protocol": 17 2490 } 2491 }, 2492 "l4": { 2493 "udp": { 2494 "destination-port-range-or-operator": { 2495 "operator": "eq", 2496 "port": 123 2497 } 2498 } 2499 } 2500 }, 2501 "actions": { 2502 "forwarding": "accept" 2503 } 2504 } 2505 ] 2506 } 2507 } 2508 ] 2509 } 2511 Appendix C. A Sample Extension: DETNET-indicator 2513 In this sample extension we augment the core MUD model to indicate 2514 whether the device implements DETNET. If a device later attempts to 2515 make use of DETNET, an notification or exception might be generated. 2516 Note that this example is intended only for illustrative purposes. 2518 Extension Name: "Example-Extension" (to be used in the extensions list) 2519 Standard: this document (but do not register the example) 2521 This extension augments the MUD model to include a single node, using 2522 the following sample module that has the following tree structure: 2524 module: ietf-mud-detext-example 2525 augment /ietf-mud:mud: 2526 +--rw is-detnet-required? boolean 2528 The model is defined as follows: 2530 file "ietf-mud-detext-example@2018-01-24.yang" 2531 module ietf-mud-detext-example { 2532 yang-version 1.1; 2533 namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example"; 2534 prefix ietf-mud-detext-example; 2536 import ietf-mud { 2537 prefix ietf-mud; 2538 } 2540 organization 2541 "IETF OPSAWG (Ops Area) Working Group"; 2542 contact 2543 "WG Web: http://tools.ietf.org/wg/opsawg/ 2544 WG List: opsawg@ietf.org 2545 Author: Eliot Lear 2546 lear@cisco.com 2547 Author: Ralph Droms 2548 rdroms@gmail.com 2549 Author: Dan Romascanu 2550 dromasca@gmail.com 2552 "; 2553 description 2554 "Sample extension to a MUD module to indicate a need 2555 for DETNET support."; 2557 revision 2018-01-24 { 2558 description 2559 "Initial revision."; 2560 reference 2561 "RFC XXXX: Manufacturer Usage Description 2562 Specification"; 2563 } 2565 augment "/ietf-mud:mud" { 2566 description 2567 "This adds a simple extension for a manufacturer 2568 to indicate whether DETNET is required by a 2569 device."; 2570 leaf is-detnet-required { 2571 type boolean; 2572 description 2573 "This value will equal true if a device requires 2574 detnet to properly function"; 2575 } 2576 } 2577 } 2578 2579 Using the previous example, we now show how the extension would be 2580 expressed: 2582 { 2583 "ietf-mud:mud": { 2584 "mud-version": 1, 2585 "mud-url": "https://bms.example.com/.well-known/mud/lightbulb2000", 2586 "last-update": "2018-01-23T13:33:52+01:00", 2587 "cache-validity": 48, 2588 "is-supported": true, 2589 "systeminfo": "The BMS Example Lightbulb", 2590 "extensions": [ 2591 "ietf-mud-detext-example" 2592 ], 2593 "ietf-mud-detext-example:is-detnet-required": "false", 2594 "from-device-policy": { 2595 "access-lists": { 2596 "access-list": [ 2597 { 2598 "name": "mud-45782-v6fr" 2599 } 2600 ] 2601 } 2602 }, 2603 "to-device-policy": { 2604 "access-lists": { 2605 "access-list": [ 2606 { 2607 "name": "mud-45782-v6to" 2608 } 2609 ] 2610 } 2611 } 2612 }, 2613 "ietf-access-control-list:access-lists": { 2614 "acl": [ 2615 { 2616 "name": "mud-45782-v6to", 2617 "type": "ipv6-acl-type", 2618 "aces": { 2619 "ace": [ 2620 { 2621 "rule-name": "cl0-todev", 2622 "matches": { 2623 "ipv6-acl": { 2624 "ietf-acldns:src-dnsname": "service.bms.example.com", 2625 "protocol": 6, 2626 "source-port-range-or-operator": { 2627 "operator": "eq", 2628 "port": 443 2629 } 2630 }, 2631 "tcp": { 2632 "ietf-mud:direction-initiated": "from-device" 2633 } 2634 }, 2635 "actions": { 2636 "forwarding": "accept" 2637 } 2638 } 2639 ] 2640 } 2641 }, 2642 { 2643 "name": "mud-45782-v6fr", 2644 "acl-type": "ipv6-acl-type", 2645 "aces": { 2646 "ace": [ 2647 { 2648 "rule-name": "cl0-frdev", 2649 "matches": { 2650 "ipv6-acl": { 2651 "ietf-acldns:dst-dnsname": "service.bms.example.com", 2652 "protocol": 6, 2653 "destination-port-range-or-operator": { 2654 "operator": "eq", 2655 "port": 443 2656 } 2657 }, 2658 "tcp": { 2659 "ietf-mud:direction-initiated": "from-device" 2660 } 2661 }, 2662 "actions": { 2663 "forwarding": "accept" 2664 } 2665 } 2666 ] 2667 } 2668 } 2669 ] 2670 } 2671 } 2673 Authors' Addresses 2675 Eliot Lear 2676 Cisco Systems 2677 Richtistrasse 7 2678 Wallisellen CH-8304 2679 Switzerland 2681 Phone: +41 44 878 9200 2682 Email: lear@cisco.com 2684 Ralph Droms 2686 Phone: +1 978 376 3731 2687 Email: rdroms@gmail.com 2689 Dan Romascanu 2691 Phone: +972 54 5555347 2692 Email: dromasca@gmail.com