Manufacturer Usage Description Specification
draft-ietf-opsawg-mud-13

Network Working Group                                            E. Lear
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                R. Droms
Expires: March 19, 2018
                                                            D. Romascanu
                                                      September 15, 2017


              Manufacturer Usage Description Specification
                        draft-ietf-opsawg-mud-10

Abstract

   This memo specifies a component-based architecture for manufacturer
   usage descriptions (MUD).  The goal of MUD is to provide a means for
   Things to signal to the network what sort of access and network
   functionality they require to properly function.  The initial focus
   is on access control.  Later work can delve into other aspects.

   This memo specifies two YANG modules, IPv4 and IPv6 DHCP options, an
   LLDP TLV, a URL suffix specification, an X.509 certificate extension
   and a means to sign and verify the descriptions.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 19, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  What MUD doesn't do . . . . . . . . . . . . . . . . . . .   4
     1.2.  A Simple Example  . . . . . . . . . . . . . . . . . . . .   5
     1.3.  Determining Intended Use  . . . . . . . . . . . . . . . .   5
     1.4.  Finding A Policy: The MUD URL . . . . . . . . . . . . . .   5
     1.5.  Types of Policies . . . . . . . . . . . . . . . . . . . .   6
     1.6.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   8
     1.7.  The Manufacturer Usage Description Architecture . . . . .   8
     1.8.  Order of operations . . . . . . . . . . . . . . . . . . .  10
   2.  The MUD Model and Semantic Meaning  . . . . . . . . . . . . .  10
   3.  Data Node Definitions . . . . . . . . . . . . . . . . . . . .  12
     3.1.  to-device-policy and from-device-policy containers  . . .  12
     3.2.  last-update . . . . . . . . . . . . . . . . . . . . . . .  13
     3.3.  cache-validity  . . . . . . . . . . . . . . . . . . . . .  13
     3.4.  masa-server . . . . . . . . . . . . . . . . . . . . . . .  13
     3.5.  is-supported  . . . . . . . . . . . . . . . . . . . . . .  13
     3.6.  systeminfo  . . . . . . . . . . . . . . . . . . . . . . .  13
     3.7.  extensions  . . . . . . . . . . . . . . . . . . . . . . .  13
     3.8.  manufacturer  . . . . . . . . . . . . . . . . . . . . . .  14
     3.9.  same-manufacturer . . . . . . . . . . . . . . . . . . . .  14
     3.10. model . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     3.11. local-networks  . . . . . . . . . . . . . . . . . . . . .  14
     3.12. controller  . . . . . . . . . . . . . . . . . . . . . . .  15
     3.13. my-controller . . . . . . . . . . . . . . . . . . . . . .  15
     3.14. direction-initiated . . . . . . . . . . . . . . . . . . .  15
   4.  Processing of the MUD file  . . . . . . . . . . . . . . . . .  15
   5.  What does a MUD URL look like?  . . . . . . . . . . . . . . .  16
   6.  The MUD YANG Model  . . . . . . . . . . . . . . . . . . . . .  17
   7.  The Domain Name Extension to the ACL Model  . . . . . . . . .  22
     7.1.  source-dnsname  . . . . . . . . . . . . . . . . . . . . .  23
     7.2.  destination-dnsname . . . . . . . . . . . . . . . . . . .  23
     7.3.  The ietf-acldns Model . . . . . . . . . . . . . . . . . .  23
   8.  MUD File Example  . . . . . . . . . . . . . . . . . . . . . .  25
   9.  The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . .  27
     9.1.  Client Behavior . . . . . . . . . . . . . . . . . . . . .  28
     9.2.  Server Behavior . . . . . . . . . . . . . . . . . . . . .  28
     9.3.  Relay Requirements  . . . . . . . . . . . . . . . . . . .  29
   10. The Manufacturer Usage Description (MUD) URL X.509 Extension   29
   11. The Manufacturer Usage Description LLDP extension . . . . . .  30



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   12. Creating and Processing of Signed MUD Files . . . . . . . . .  32
     12.1.  Creating a MUD file signature  . . . . . . . . . . . . .  32
     12.2.  Verifying a MUD file signature . . . . . . . . . . . . .  32
   13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . .  33
   14. Deployment Considerations . . . . . . . . . . . . . . . . . .  33
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  34
   16. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  36
     16.1.  YANG Module Registrations  . . . . . . . . . . . . . . .  36
     16.2.  DHCPv4 and DHCPv6 Options  . . . . . . . . . . . . . . .  36
     16.3.  PKIX Extensions  . . . . . . . . . . . . . . . . . . . .  37
     16.4.  Well Known URI Suffix  . . . . . . . . . . . . . . . . .  37
     16.5.  MIME Media-type Registration for MUD files . . . . . . .  37
     16.6.  LLDP IANA TLV Subtype Registry . . . . . . . . . . . . .  38
     16.7.  The MUD Well Known Universal Resource Name (URNs)  . . .  39
     16.8.  Extensions Registry  . . . . . . . . . . . . . . . . . .  39
   17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  39
   18. References  . . . . . . . . . . . . . . . . . . . . . . . . .  40
     18.1.  Normative References . . . . . . . . . . . . . . . . . .  40
     18.2.  Informative References . . . . . . . . . . . . . . . . .  42
   Appendix A.  Changes from Earlier Versions  . . . . . . . . . . .  43
   Appendix B.  Default MUD nodes  . . . . . . . . . . . . . . . . .  45
   Appendix C.  A Sample Extension: DETNET-indicator . . . . . . . .  49
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  53

1.  Introduction

   The Internet has largely been constructed on general purpose
   computers; those devices that may be used for a purpose that is
   specified by those who buy the device.  [RFC1984] presumed that an
   end device would be most capable of protecting itself.  This made
   sense when the typical device was a workstation or a mainframe, and
   it continues to make sense for general purpose computing devices
   today, including laptops, smart phones, and tablets.

   [RFC7452] discusses design patterns for, and poses questions about,
   smart objects.  Let us then posit a group of objects that are
   specifically NOT general purpose computers.  These devices have a
   purpose to their use.  By definition, therefore, all other purposes
   are NOT intended.  The combination of these two statements can be
   restated as a manufacturer usage description (MUD) that can be
   applied at various points within a network.  Although this memo may
   seem to stress access requirements, usage intent also consists of
   quality of service needs a device may have.

   We use the notion of "manufacturer" loosely in this context, to
   simply mean the entity or organization that will state how a device
   is intended to be used.  In the context of a lightbulb, this might
   indeed be the lightbulb manufacturer.  In the context of a smarter



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   device that has a built in Linux stack, it might be an integrator of
   that device.  The key points are that the device itself is expected
   to serve a limited purpose, and that there may exist an organization
   in the supply chain of that device that will take responsibility for
   informing the network about that purpose.

   The intent MUD is to solve for the following problems:

   o  Substantially reduce the threat surface on a device entering a
      network to those communications intended by the manufacturer.

   o  Provide for a means to scale network policies to the ever-
      increasing number types of devices in the network.

   o  Provide a means to address at least some vulnerabilities in a way
      that is faster than it might take to update systems.  This will be
      particularly true for systems that are no longer supported by
      their manufacturer.

   o  Keep the cost of implementation of such a system to the bare
      minimum.

   MUD consists of three architectural building blocks: * A classifier
   that a device emits that can be used to locate a description; * The
   description itself, including how it is interpreted, and; * A means
   for local network management systems to retrieve the description.

   In this specification we describe each of these building blocks and
   how they are intended to be used together.  However, they may also be
   used separately, independent of this specification by local
   deployments for their own purposes.

1.1.  What MUD doesn't do

   MUD is not intended to address network authorization of general
   purpose computers, as their manufacturers cannot envision a specific
   communication pattern to describe.  In addition, even those devices
   that have a single or small number of uses might have very broad
   communication patterns.  MUD on its own is not for them either.

   No matter how good a MUD-enabled network is, it will never replace
   the need for manufacturers to patch vulnerabilities.  It may,
   however, provide network administrators with some additional
   protection when those vulnerabilities exist.

   Finally, no matter what the manufacturer specifies in a MUD file,
   these are not directives, but suggestions.  How they are instantiated




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   locally will depend on many factors, and is ultimately up to the
   local network administrator.

1.2.  A Simple Example

   A light bulb is intended to light a room.  It may be remotely
   controlled through the network; and it may make use of a rendezvous
   service of some form that an app on smart phone accesses.  What we
   can say about that light bulb, then, is that all other network access
   is unwanted.  It will not contact a news service, nor speak to the
   refrigerator, and it has no need of a printer or other devices.  It
   has no social networking friends.  Therefore, an access list applied
   to it that states that it will only connect to the single rendezvous
   service will not impede the light bulb in performing its function,
   while at the same time allowing the network to provide both it and
   other devices an additional layer of protection.

1.3.  Determining Intended Use

   The notion of intended use is in itself not new.  Network
   administrators apply access lists every day to allow for only such
   use.  This notion of white listing was well described by Chapman and
   Zwicky in [FW95].  Profiling systems that make use of heuristics to
   identify types of systems have existed for years as well.

   A Thing could just as easily tell the network what sort of protection
   it requires without going into what sort of system it is.  This
   would, in effect, be the converse of [RFC7488].  In seeking a general
   purpose solution, however, we assume that a device has so few
   capabilities that it will implement the least necessary capabilities
   to function properly.  This is a basic economic constraint.  Unless
   the network would refuse access to such a device, its developers
   would have no reason to provide the network any information.  To
   date, such an assertion has held true.

1.4.  Finding A Policy: The MUD URL

   Our work begins with the device emitting a Universal Resource Locator
   (URL) [RFC3986].  This URL serves both to classify the device type
   and to provide a means to locate a policy file.

   In this memo three means are defined to emit the MUD URL.  One is a
   DHCP option[RFC2131],[RFC3315] that the DHCP client uses to inform
   the DHCP server.  The DHCP server may take further actions, such as
   retrieve the URL or otherwise pass it along to network management
   system or controller.  The second method defined is an X.509
   constraint.  The IEEE has developed [IEEE8021AR] that provides a
   certificate-based approach to communicate device characteristics,



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   which itself relies on [RFC5280].  The MUD URL extension is non-
   critical, as required by IEEE 802.1AR.  Various means may be used to
   communicate that certificate, including Tunnel Extensible
   Authentication Protocol (TEAP) [RFC7170].  Finally, a Link Layer
   Discovery Protocol (LLDP) frame is defined [IEEE8021AB].

   It is possible that there may be other means for a MUD URL to be
   learned by a network.  For instance, some devices may already be
   fielded or have very limited ability to communicate a MUD URL, and
   yet can be identified through some means, such as a serial number or
   a public key.  In these cases, manufacturers may be able to map those
   identifies to particular MUD URLs (or even the files themselves).
   Similarly, there may be alternative resolution mechanisms available
   for situations where Internet connectivity is limited or does not
   exist.  Such mechanisms are not described in this memo, but are
   possible.  Implementors should allow for this sort of flexibility of
   how MUD URLs may be learned.

1.5.  Types of Policies

   When the MUD URL is resolved, the MUD controller retrieves a file
   that describes what sort of communications a device is designed to
   have.  The manufacturer may specify either specific hosts for cloud
   based services or certain classes for access within an operational
   network.  An example of a class might be "devices of a specified
   manufacturer type", where the manufacturer type itself is indicated
   simply by the authority component (e.g, the domain name) of the MUD
   URL.  Another example might be to allow or disallow local access.
   Just like other policies, these may be combined.  For example:

      Allow access to devices of the same manufacturer
      Allow access to and from controllers via COAP
      Allow access to local DNS/DHCP
      Deny all other access

   To add a bit more depth that should not be a stretch of anyone's
   imagination, one could also make use of port-based access lists.
   Thus a printer might have a description that states:

      Allow access for port IPP or port LPD
      Allow local access for port HTTP
      Deny all other access

   In this way anyone can print to the printer, but local access would
   be required for the management interface.

   The files that are retrieved are intended to be closely aligned to
   existing network architectures so that they are easy to deploy.  We



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   make use of YANG [RFC6020] because of the time and effort spent to
   develop accurate and adequate models for use by network devices.
   JSON is used as a serialization for compactness and readability,
   relative to XML.  Other formats may be chosen with later versions of
   MUD.

   While the policy examples given here focus on access control, this is
   not intended to be the sole focus.  By structuring the model
   described in this document with clear extension points, so that other
   descriptions could be included.  One that often comes to mind is
   quality of service.

   The YANG modules specified here are extensions of
   [I-D.ietf-netmod-acl-model].  The extensions to this model allow for
   a manufacturer to express classes of systems that a manufacturer
   would find necessary for the proper function of the device.  Two
   modules are specified.  The first module specifies a means for domain
   names to be used in ACLs so that devices that have their controllers
   in the cloud may be appropriately authorized with domain names, where
   the mapping of those names to addresses may rapidly change.

   The other module abstracts away IP addresses into certain classes
   that are instantiated into actual IP addresses through local
   processing.  Through these classes, manufacturers can specify how the
   device is designed to communicate, so that network elements can be
   configured by local systems that have local topological knowledge.
   That is, the deployment populates the classes that the manufacturer
   specifies.  The abstractions below map to zero or more hosts, as
   follows:

   Manufacturer:  A device made by a particular manufacturer, as
      identified by the authority component of its MUD-URL

   same-manufacturer:  Devices that have the same authority component of
      their MUD-URL.

   Controller:  Devices that the local network administrator admits to
      the particular class.

   my-controller:  Devices associated with the MUD-URL of a device that
      the administrator admits.

   local:  The class of IP addresses that are scoped within some
      administrative boundary.  By default it is suggested that this be
      the local subnet.






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   The "manufacturer" classes can be easily specified by the
   manufacturer, whereas controller classes are initially envisioned to
   be specified by the administrator.

   Because manufacturers do not know who will be using their devices, it
   is important for functionality referenced in usage descriptions to be
   relatively ubiquitous, and mature.  For these reasons only a limited
   subset YANG-based configuration of is permitted in a MUD file.

1.6.  Terminology

   MUD:  manufacturer usage description.

   MUD file:  a file containing YANG-based JSON that describes a Thing
      and associated suggested specific network behavior.

   MUD file server:  a web server that hosts a MUD file.

   MUD controller:  the system that requests and receives the MUD file
      from the MUD server.  After it has processed a MUD file it may
      direct changes to relevant network elements.

   MUD URL:  a URL that can be used by the MUD controller to receive the
      MUD file.

   Thing:  the device emitting a MUD URL.

   Manufacturer:  the entity that configures the Thing to emit the MUD
      URL and the one who asserts a recommendation in a MUD file.  The
      manufacturer might not always be the entity that constructs a
      Thing.  It could, for instance, be a systems integrator, or even a
      component provider.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.7.  The Manufacturer Usage Description Architecture

   With these components laid out we now have the basis for an
   archicture.  This leads us to ASCII art.










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    .......................................
    .                      ____________   .           _____________
    .                     |            |  .          |             |
    .                     |    MUD     |-->get URL-->|   MUD       |
    .                     | Controller |  .(https)   | File Server |
    .  End system network |____________|<-MUD file<-<|_____________|
    .                             .       .
    .                             .       .
    . _______                 _________   .
    .|       |  (dhcp et al) | router  |  .
    .| Thing |---->MUD URL-->|   or    |  .
    .|_______|               | switch  |  .
    .                        |_________|  .
    .......................................

                        Figure 1: MUD Architecture

   In the above diagram, the switch or router collects MUD URLs and
   forwards them to the network management system for processing.  This
   happens in different ways, depending on how the URL is communicated.
   For instance, in the case of DHCP, the DHCP server might receive the
   URL and then process it.  In the case of IEEE 802.1X, the switch
   would carry the URL via a certificate to the authentication server
   via EAP over Radius[RFC3748], which would then process it.  One
   method to do this is TEAP, described in [RFC7170].  The certificate
   extension is described below.

   The information returned by the web site is valid for the duration of
   the Thing's connection, or as specified in the description.  Thus if
   the Thing is disconnected, any associated configuration in the switch
   can be removed.  Similarly, from time to time the description may be
   refreshed, based on new capabilities or communication patterns or
   vulnerabilities.

   The web site is typically run by or on behalf of the manufacturer.
   Its domain name is that of the authority found in the MUD URL.  For
   legacy cases where Things cannot emit a URL, if the switch is able to
   determine the appropriate URL, it may proxy it, the trivial cases
   being a map between some registered Thing or port and a URL.

   The role of the MUD controller in this environment is to do the
   following:

   o  receive MUD URLs,

   o  retrieve MUD files,





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   o  translate abstractions in the MUD files to specific Thing
      configuration,

   o  maintain and update any required mappings of the abstractions, and

   o  update network elements with appropriate configuration.

   A MUD controller may be a component of a AAA or network management
   system.  Communication within those systems and from those systems to
   network elements is beyond the scope of this memo.

1.8.  Order of operations

   As mentioned above, MUD contains architectural building blocks, and
   so order of operation may vary.  However, here is one clear intended
   example:

   1.  Thing emits URL.

   2.  That URL is forwarded to a MUD controller by the nearest switch
       (how this happens depends on the way in which the MUD URL is
       emitted).

   3.  The MUD controller retrieves the MUD file and signature from the
       MUD file server, assuming it doesn't already have copies.  After
       validating the signature, it may test the URL against a web or
       domain reputation service, and it may test any hosts within the
       file against those reputation services, as it deems fit.

   4.  The MUD controller may query the administrator for permission to
       add the Thing and associated policy.  If the Thing is known or
       the Thing type is known, it may skip this step.

   5.  The MUD controller instantiates local configuration based on the
       abstractions defined in this document.

   6.  The MUD controller configures the switch nearest the Thing.
       Other systems may be configured as well.

   7.  When the Thing disconnects, policy is removed.

2.  The MUD Model and Semantic Meaning

   A MUD file consists of JSON based on a YANG model.  For purposes of
   MUD, the nodes that can be modified are access lists as augmented by
   this model.  The MUD file is limited to the serialization of only the
   following YANG schema:




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   o  ietf-access-control-list [I-D.ietf-netmod-acl-model]

   o  ietf-mud (this document)

   o  ietf-acldns (this document)

   Extensions may be used to add additional schema.  This is described
   further on.

   To provide the widest possible deployability, with the exceptions of
   "acl-name", "acl-type", "rule-name", and TCP and UDP source and
   destination port information, publishers of MUD files SHOULD limit
   the use of ACL model leaf nodes expressed to those found in this
   specification.  Absent any extensions, MUD files are assumed to
   implement only the following ACL model features:

   o  icmp-acl, ipv6-acl, tcp-acl, udp-acl, ipv4-acl, and ipv6-acl

   MUD controllers MAY ignore any particular component of a description
   or MAY ignore the description in its entirety, and SHOULD carefully
   inspect all MUD descriptions.  Publishers of MUD files MUST NOT
   include other nodes except as described in Section 3.7.  See that
   section for more information.

   ======= This module is structured into three parts:

   o  The first container "mud" holds information that is relevant to
      retrieval and validity of the MUD file itself, as well as policy
      intended to and from the Thing.

   o  The second component augments the matching container of the ACL
      model to add several nodes that are relevant to the MUD URL, or
      otherwise abstracted for use within a local environment.

   o  The third component augments the tcp-acl container of the ACL
      model to add the ability to match on the direction of initiation
      of a TCP connection.

   A valid MUD file will contain two root objects, a "mud" container and
   an "access-lists" container.  Extensions may add additional root
   objects as required.

   A simplified graphical representation of the data models is used in
   this document.  The meaning of the symbols in these diagrams is
   explained in [I-D.ietf-netmod-rfc6087bis].






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   module: ietf-mud
       +--rw mud!
          +--rw mud-url               inet:uri
          +--rw last-update           yang:date-and-time
          +--rw cache-validity?       uint8
          +--rw masa-server?          inet:uri
          +--rw is-supported          boolean
          +--rw systeminfo?           inet:uri
          +--rw extensions*           string
          +--rw from-device-policy
          |  +--rw access-lists
          |     +--rw access-list* [acl-name acl-type]
          |        +--rw acl-name    -> /acl:access-lists/acl/acl-name
          |        +--rw acl-type    identityref
          +--rw to-device-policy
             +--rw access-lists
                +--rw access-list* [acl-name acl-type]
                   +--rw acl-name    -> /acl:access-lists/acl/acl-name
                   +--rw acl-type    identityref
     augment /acl:access-lists/acl:acl/acl:aces/
      acl:ace/acl:matches:
       +--rw mud-acl
          +--rw manufacturer?        inet:host
          +--rw same-manufacturer?   empty
          +--rw model?               inet:uri
          +--rw local-networks?      empty
          +--rw controller?          inet:uri
          +--rw my-controller?       empty
     augment /acl:access-lists/acl:acl/acl:aces/
      acl:ace/acl:matches/acl:tcp-acl:
       +--rw direction-initiated?   direction


3.  Data Node Definitions

   Note that in this section, when we use the term "match" we are
   referring to the ACL model "matches" node, and thus returns positive
   such that an action should be applied.

   The following nodes are defined.

3.1.  to-device-policy and from-device-policy containers

   [I-D.ietf-netmod-acl-model] describes access-lists but does not
   attempt to indicate where they are applied as that is handled
   elsewhere in a configuration.  However, in this case, a MUD file must
   be explicit in describing the communication pattern of a Thing, and
   that includes indicating what is to be permitted or denied in either



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   direction of communication.  Hence each of these containers indicate
   the appropriate direction of a flow in association with a particular
   Thing.  They contain references to specific access-lists.

3.2.  last-update

   This is a date-and-time value of when the MUD file was generated.
   This is akin to a version number.  Its form is taken from [RFC6991]
   which, for those keeping score, in turn was taken from Section 5.6 of
   [RFC3339], which was taken from [ISO.8601.1988].

3.3.  cache-validity

   This uint8 is the period of time in hours that a network management
   station MUST wait since its last retrieval before checking for an
   update.  It is RECOMMENDED that this value be no less than 24 and
   MUST NOT be more than 168 for any Thing that is supported.  This
   period SHOULD be no shorter than any period determined through HTTP
   caching directives (e.g., "cache-control" or "Expires").  N.B.,
   expiring of this timer does not require the MUD controller to discard
   the MUD file, nor terminate access to a Thing.  See Section 15 for
   more information.

3.4.  masa-server

   This optional node refers to the URL that should be used to resolve
   the MASA service, as specified in
   [I-D.ietf-anima-bootstrapping-keyinfra].

3.5.  is-supported

   This boolean is an indication from the manufacturer to the network
   administrator as to whether or not the Thing is supported.  In this
   context a Thing is said to be supported if the manufacturer might
   issue an update to the Thing or if the manufacturer might update the
   MUD file.

3.6.  systeminfo

   This is a URL that points to a description of the Thing to be
   connected.  The intent is for administrators to be able to read about
   what the Thing is the first time the MUD-URL is used.

3.7.  extensions

   This optional leaf-list names MUD extensions that are used in the MUD
   file.  Note that NO MUD extensions may be used in a MUD file prior to




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   the extensions being declared.  Implementations MUST ignore any node
   in this file that they do not understand.

   Note that extensions can either extend the MUD file as described in
   the previous paragraph, or they might reference other work.  A good
   example of how this might be done is the masa-server URI that is
   defined in the base model.  We say nothing about the semantics of
   that work here, but rather leave that to the underlying specification
   found in [I-D.ietf-anima-bootstrapping-keyinfra].

3.8.  manufacturer

   This node consists of a hostname that would be matched against the
   authority component of another Thing's MUD URL.  In its simplest form
   "manufacturer" and "same-manufacturer" may be implemented as access-
   lists.  In more complex forms, additional network capabilities may be
   used.  For example, if one saw the line "manufacturer" :
   "flobbidy.example.com", then all Things that registered with a MUD
   URL that contained flobbity.example.com in its authority section
   would match.

3.9.  same-manufacturer

   This is an equivalent for when the manufacturer element is used to
   indicate the authority that is found in another Thing's MUD URL
   matches that of the authority found in this Thing's MUD URL.  For
   example, if the Thing's MUD URL were https://b1.example.com/.well-
   known/mud/v1/ThingV1, then all devices that had MUD URL with an
   authority section of b1.example.com would match.

3.10.  model

   This string matches the entire MUD URL, thus covering the model that
   is unique within the context of the authority.  It may contain not
   only model information, but versioning information as well, and any
   other information that the manufacturer wishes to add.  The intended
   use is for devices of this precise class to match, to permit or deny
   communication between one another.

3.11.  local-networks

   This null-valued node expands to include local networks.  Its default
   expansion is that packets must not traverse toward a default route
   that is received from the router.  However, administrators may expand
   the expression as is appropriate in their deployments.






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3.12.  controller

   This URI specifies a value that a controller will register with the
   mud controller.  The node then is expanded to the set of hosts that
   are so registered.  This node may also be a URN.  In this case, the
   URN describes a well known service, such as DNS or NTP.

   Great care should be used when invoking the controller class.  For
   one thing, it requires some understanding by the administrator as to
   when it is appropriate.  Classes that are standardized may make it
   possible to easily name devices that support standard functions.  For
   instance, the MUD controller could have some knowledge of which DNS
   servers should be used for any particular group of Things.  Non-
   standard classes will likely require some sort of administrator
   interaction.  Pre-registration in such classes by controllers with
   the MUD server is encouraged.  The mechanism to do that is beyond the
   scope of this work.

   Controller URIs MAY take the form of a URL (e.g. "http[s]://").
   However, MUD controllers MUST NOT resolve and retrieve such files,
   and it is RECOMMENDED that there be no such file at this time, as
   their form and function may be defined at a point in the future.  For
   now, URLs should serve simply as class names and be populated by the
   local deployment administrator.

3.13.  my-controller

   This null-valued node signals to the MUD controller to use whatever
   mapping it has for this MUD-URL to a particular group of hosts.  This
   may require prompting the administrator for class members.  Future
   work should seek to automate membership management.

3.14.  direction-initiated

   When applied this matches packets when the flow was initiated in the
   corresponding direction.  [RFC6092] specifies IPv6 guidance best
   practices.  While that document is scoped specifically to IPv6, its
   contents are applicable for IPv4 as well.  When this flag is set, and
   the system has no reason to believe a flow has been initiated it MUST
   drop the packet.  This node may be implemented in its simplest form
   by looking at naked SYN bits, but may also be implemented through
   more stateful mechanisms.

4.  Processing of the MUD file

   To keep things relatively simple in addition to whatever definitions
   exist, we also apply two additional default behaviors:




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   o  Anything not explicitly permitted is denied.

   o  Local DNS and NTP are, by default, permitted to and from the
      Thing.

   An explicit description of the defaults can be found in Appendix B.

5.  What does a MUD URL look like?

   To begin with, MUD takes full advantage of both the https: scheme and
   the use of .well-known.  HTTPS is important in this case because a
   man in the middle attack could otherwise harm the operation of a
   class of Things.  .well-known is used because we wish to add
   additional structure to the URL, and want to leave open for future
   versions both the means by which the URL is processed and the format
   of the MUD file retrieved (there have already been some discussions
   along these lines).  The URL appears as follows:

      mud-url   = "https://" authority  "/.well-known/mud/" mud-rev
                  "/" modelinfo ( "?" extras )
                  ; authority is from RFC3986
      mud-rev   = "v1"
      modelinfo = segment  ; from RFC3986
      extras    = query    ; from RFC3986


   mud-rev signifies the version of the manufacturer usage description
   file.  This memo specifies "v1" of that file.  Later versions may
   permit additional schemas or modify the format.  In order to provide
   for the broadest compatibility for the various transmission
   mechanisms, the length of the URL for v1 MUST NOT exceed 255 octets.

   Taken together with the mud-url, "modelinfo" represents a Thing model
   as the manufacturer wishes to represent it.  It could be a brand name
   or something more specific.  It also may provide a means to indicate
   what version the product is.  Specifically if it has been updated in
   the field, this is the place where evidence of that update would
   appear.  The field should be changed when the intended communication
   patterns of a Thing change.  While from a controller standpoint, only
   comparison and matching operations are safe, it is envisioned that
   updates will require some administrative review.  Processing of this
   URL occurs as specified in [RFC2818] and [RFC3986].

   "extras" is intended for use by the MUD controller to provide
   additional information such as posture about the Thing to the MUD
   file server.  This field MUST NOT be configured on the Thing itself
   by a manufacturer - that is what "modelinfo" is for.  It is left as
   future work to define the full semantics of this field.



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6.  The MUD YANG Model

   <CODE BEGINS>file "ietf-mud@2017-09-15.yang"
   module ietf-mud {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-mud";
     prefix ietf-mud;

     import ietf-access-control-list {
       prefix acl;
     }
     import ietf-yang-types {
       prefix yang;
     }
     import ietf-inet-types {
       prefix inet;
     }

     organization
       "IETF OPSAWG (Ops Area) Working Group";
     contact
       "WG Web: http://tools.ietf.org/wg/opsawg/
        WG List: opsawg@ietf.org
        Author: Eliot Lear
        lear@cisco.com
        Author: Ralph Droms
        rdroms@gmail.com
        Author: Dan Romascanu
        dromasca@gmail.com

       ";
     description
       "This YANG module defines a component that augments the
        IETF description of an access list.  This specific module
        focuses on additional filters that include local, model,
        and same-manufacturer.

        This module is intended to be serialized via JSON and stored
        as a file, as described in RFC XXXX [RFC Editor to fill in with
        this document #].

        Copyright (c) 2016,2017 IETF Trust and the persons
        identified as the document authors.  All rights reserved.
        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Simplified BSD
        License set forth in Section 4.c of the IETF Trust's Legal
        Provisions Relating to IETF Documents



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        (http://trustee.ietf.org/license-info).
        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     revision 2017-09-15 {
       description
         "Initial proposed standard.";
       reference
         "RFC XXXX: Manufacturer Usage Description
          Specification";
     }

     typedef direction {
       type enumeration {
         enum "to-device" {
           description
             "packets or flows destined to the target
              Thing";
         }
         enum "from-device" {
           description
             "packets or flows destined from
              the target Thing";
         }
       }
       description
         "Which way are we talking about?";
     }

     container mud {
       presence "Enabled for this particular MUD-URL";
       description
         "MUD related information, as specified
          by RFC-XXXX [RFC Editor to fill in].";
       uses mud-grouping;
     }

     grouping mud-grouping {
       description
         "Information about when support end(ed), and
          when to refresh";
       leaf mud-url {
         type inet:uri;
         mandatory true;
         description
           "This is the MUD-URL associated with the entry found
            in a MUD file.";
       }



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       leaf last-update {
         type yang:date-and-time;
         mandatory true;
         description
           "This is intended to be when the current MUD file
            was generated.  MUD Controllers SHOULD NOT check
            for updates between this time plus cache validity";
       }
       leaf cache-validity {
         type uint8 {
           range "1..168";
         }
         units "hours";
         default "48";
         description
           "The information retrieved from the MUD server is
            valid for these many hours, after which it should
            be refreshed.  N.B. MUD controller implementations
            need not discard MUD files beyond this period.";
       }
       leaf masa-server {
         type inet:uri;
         description
           "The URI of the MASA server that network
            elements should forward requests to for this Thing.";
       }
       leaf is-supported {
         type boolean;
         mandatory true;
         description
           "This boolean indicates whether or not the Thing is
            currently supported by the manufacturer.";
       }
       leaf systeminfo {
         type inet:uri;
         description
           "A URL to a description of this Thing.  This
            should be a brief localized description.  The
            reference text should be no more than octets.
            systeminfo may be displayed to the user to
            determine whether to allow the Thing on the
            network.";
       }
       leaf-list extensions {
         type string {
            length "1..40";
         }
         description



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           "A list of extension names that are used in this MUD
            file.  Each name is registered with the IANA and
            described in an RFC.";
       }
       container from-device-policy {
         description
           "The policies that should be enforced on traffic
            coming from the device. These policies are not
            necessarily intended to be enforced at a single
            point, but may be rendered by the controller to any
            relevant enorcement points in the network or
            elsewhere.";
         uses access-lists;
       }
       container to-device-policy {
         description
           "The policies that should be enforced on traffic
            going to the device. These policies are not
            necessarily intended to be enforced at a single
            point, but may be rendered by the controller to any
            relevant enorcement points in the network or
            elsewhere.";
         uses access-lists;
       }
     }

     grouping access-lists {
       description
         "A grouping for access lists in the context of device
          policy.";
       container access-lists {
         description
           "The access lists that should be applied to traffic
              to or from the device.";
         list access-list {
           key "acl-name acl-type";
           description
             "Each entry on this list refers to an ACL that
                should be present in the overall access list
                data model. Each ACL is identified by name and
                type.";
           leaf acl-name {
             type leafref {
               path "/acl:access-lists/acl:acl/acl:acl-name";
             }
             description
               "The name of the ACL for this entry.";
           }



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           leaf acl-type {
             type identityref {
               base acl:acl-base;
             }
             description
               "The type of the ACL for this entry.  The name is
                scoped ONLY to the MUD file, and may not be unique
                in any other circumstance.";
           }
         }
       }
     }

     augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/acl:matches" {
       description
         "adding abstractions to avoid need of IP addresses";
       container mud-acl {
         description
           "MUD-specific matches.";
         leaf manufacturer {
           type inet:host;
           description
             "A domain that is intended to match the authority
              section of the MUD-URL. This node is used to specify
              one or more manufacturers a device should
              be authorized to access.";
         }
         leaf same-manufacturer {
           type empty;
           description
             "This node matches the authority section of the MUD-URL
              of a Thing.  It is intended to grant access to all
              devices with the same authority section.";
         }
         leaf model {
           type inet:uri;
           description
             "Devices of the specified  model type will match if
              they have an identical MUD-URL.";
         }
         leaf local-networks {
           type empty;
           description
             "IP addresses will match this node if they are
              considered local addresses.  A local address may be
              a list of locally defined prefixes and masks
              that indicate a particular administrative scope.";
         }



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         leaf controller {
           type inet:uri;
           description
             "This node names a class that has associated with it
              zero or more IP addresses to match against.  These
              may be scoped to a manufacturer or via a standard
              URN.";
         }
         leaf my-controller {
           type empty;
           description
             "This node matches one or more network elements that
              have been configured to be the controller for this
              Thing, based on its MUD-URL.";
         }
       }
     }
     augment "/acl:access-lists/acl:acl/acl:aces/" +
        "acl:ace/acl:matches/acl:tcp-acl" {
       description
         "Adding domain names to matching";
       leaf direction-initiated {
         type direction;
         description
           "This node matches based on which direction a
            connection was initiated. The means by which that
            is determined is discussed in this document.";
       }
     }
   }

   <CODE ENDS>


7.  The Domain Name Extension to the ACL Model

   This module specifies an extension to IETF-ACL model such that domain
   names may be referenced by augmenting the "matches" node.  Different
   implementations may deploy differing methods to maintain the mapping
   between IP address and domain name, if indeed any are needed.
   However, the intent is that resources that are referred to using a
   name should be authorized (or not) within an access list.

   The structure of the change is as follows:







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   module: ietf-acldns
     augment /acl:access-lists/acl:acl/acl:aces/acl:ace/
       acl:matches/acl:ipv4-acl:
       +--rw src-dnsname?   inet:host
       +--rw dst-dnsname?   inet:host
     augment /acl:access-lists/acl:acl/acl:aces/acl:ace/
       acl:matches/acl:ipv6-acl:
       +--rw src-dnsname?   inet:host
       +--rw dst-dnsname?   inet:host


   The choice of these particular points in the access-list model is
   based on the assumption that we are in some way referring to IP-
   related resources, as that is what the DNS returns.  A domain name in
   our context is defined in [RFC6991].  The augmentations are
   replicated across IPv4 and IPv6 to allow MUD file authors the ability
   to control the IP version that the Thing may utilize.

   The following node are defined.

7.1.  source-dnsname

   The argument corresponds to a domain name of a source as specified by
   inet:host.  A number of means may be used to resolve hosts.  What is
   important is that such resolutions be consistent with ACLs required
   by Things to properly operate.

7.2.  destination-dnsname

   The argument corresponds to a domain name of a destination as
   specified by inet:host See the previous section relating to
   resolution.

7.3.  The ietf-acldns Model

   <CODE BEGINS>file "ietf-acldns@2017-09-15.yang"
   module ietf-acldns {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-acldns";
     prefix "ietf-acldns";

     import ietf-access-control-list {
       prefix "acl";
     }

     import ietf-inet-types {
       prefix "inet";
     }



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     organization
       "IETF OPSAWG (Ops Area) Working Group";

     contact
          "WG Web: http://tools.ietf.org/wg/opsawg/
          WG List: opsawg@ietf.org
          Author: Eliot Lear
          lear@cisco.com
          Author: Ralph Droms
          rdroms@gmail.com
          Author: Dan Romascanu
          dromasca@gmail.com
       ";

     description
       "This YANG module defines a component that augments the
        IETF description of an access list to allow dns names
        as matching criteria.";

     revision "2017-09-15" {
       description "Base version of dnsname extension of ACL model";
       reference "RFC XXXX: Manufacturer Usage Description
                  Specification";
     }

     grouping dns-matches {
       description "Domain names for matching.";

       leaf src-dnsname {
         type inet:host;
         description "domain name to be matched against";
       }
       leaf dst-dnsname {
         type inet:host;
         description "domain name to be matched against";
       }
     }

     augment "/acl:access-lists/acl:acl/acl:aces/acl:ace/" +
        "acl:matches/acl:ipv4-acl" {
       description "Adding domain names to matching";
       uses dns-matches;
     }

     augment "/acl:access-lists/acl:acl/" +
        "acl:aces/acl:ace/" +
        "acl:matches/acl:ipv6-acl" {
       description "Adding domain names to matching";



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       uses dns-matches;
     }
   }
   <CODE ENDS>


8.  MUD File Example

   This example contains two access lists that are intended to provide
   outbound access to a cloud service on TCP port 443.

{
  "ietf-mud:mud": {
  "mud-url": "https://bms.example.com/.well-known/mud/v1/lightbulb2000",
    "last-update": "2017-09-07T13:47:52+02:00",
    "systeminfo": "https://bms.example.com/descriptions/lightbulb2000",
    "cache-validity": 48,
    "from-device-policy": {
      "access-lists": {
        "access-list": [
          {
            "acl-name": "mud-83312-v6fr",
            "acl-type": "ietf-access-control-list:ipv6-acl"
          }
        ]
      }
    },
    "to-device-policy": {
      "access-lists": {
        "access-list": [
          {
            "acl-name": "mud-83312-v6to",
            "acl-type": "ietf-access-control-list:ipv6-acl"
          }
        ]
      }
    }
  },
  "ietf-access-control-list:access-lists": {
    "acl": [
      {
        "acl-name": "mud-83312-v6to",
        "acl-type": "ipv6-acl",
        "access-list-entries": {
          "ace": [
            {
              "rule-name": "cl0-todev",
              "matches": {



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                "ipv6-acl": {
                  "ietf-acldns:src-dnsname": "service.bms.example.com"
                },
                "protocol": 6,
                "source-port-range": {
                  "lower-port": 443,
                  "upper-port": 443
                },
                "tcp-acl": {
                  "ietf-mud:direction-initiated": "from-device"
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            }
          ]
        }
      },
      {
        "acl-name": "mud-83312-v6fr",
        "acl-type": "ipv6-acl",
        "access-list-entries": {
          "ace": [
            {
              "rule-name": "cl0-frdev",
              "matches": {
                "ipv6-acl": {
                  "ietf-acldns:dst-dnsname": "service.bms.example.com"
                },
                "protocol": 6,
                "destination-port-range": {
                  "lower-port": 443,
                  "upper-port": 443
                },
                "tcp-acl": {
                  "ietf-mud:direction-initiated": "from-device"
                }
              },
              "actions": {
                "permit": [
                  null
                ]
              }
            }
          ]



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        }
      }
    ]
  }
}


   In this example, two policies are declared, one from the Thing and
   the other to the Thing.  Each policy names an access list that
   applies to the Thing, and one that applies from.  Within each access
   list, access is permitted to packets flowing to or from the Thing
   that can be mapped to the domain name of "service.bms.example.com".
   For each access list, the enforcement point should expect that the
   thing initiated the connection.

9.  The MUD URL DHCP Option

   The IPv4 MUD URL client option has the following format:

     +------+-----+------------------------------
     | code | len |  MUD URL
     +------+-----+------------------------------


   Code OPTION_MUD_URL_V4 (161) is assigned by IANA.  len is a single
   octet that indicates the length of the URL in octets.  MUD URL is a
   URL.  MUD URLs MUST NOT exceed 255 octets.

   The IPv6 MUD URL client option has the following format:

      0                   1                   2                   3
      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         OPTION_MUD_URL_V6     |        option-length          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            MUD URL                            |
     |                              ...                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   OPTION_MUD_URL_V6 (112; assigned by IANA).

   option-length contains the length of the URL in octets.

   The intent of this option is to provide both a new Thing classifier
   to the network as well as some recommended configuration to the
   routers that implement policy.  However, it is entirely the purview
   of the network system as managed by the network administrator to



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   decide what to do with this information.  The key function of this
   option is simply to identify the type of Thing to the network in a
   structured way such that the policy can be easily found with existing
   toolsets.

9.1.  Client Behavior

   A DHCPv4 client MAY emit a DHCPv4 option and a DHCPv6 client MAY emit
   DHCPv6 option.  These options are singletons, as specified in
   [RFC7227].  Because clients are intended to have at most one MUD URL
   associated with them, they may emit at most one MUD URL option via
   DHCPv4 and one MUD URL option via DHCPv6.  In the case where both v4
   and v6 DHCP options are emitted, the same URL MUST be used.

   Clients SHOULD log or otherwise report improper acknowledgments from
   servers, but they MUST NOT modify their MUD URL configuration based
   on a server's response.  The server's response is only an
   acknowledgment that the server has processed the option, and promises
   no specific network behavior to the client.  In particular, it may
   not be possible for the server to retrieve the file associated with
   the MUD URL, or the local network administration may not wish to use
   the usage description.  Neither of these situations should be
   considered in any way exceptional.

9.2.  Server Behavior

   A DHCP server may ignore these options or take action based on
   receipt of these options.  If a server successfully parses the option
   and the URL, it MUST return the option with length field set to zero
   and a corresponding null URL field as an acknowledgment.  Even in
   this circumstance, no specific network behavior is guaranteed.  When
   a server consumes this option, it will either forward the URL and
   relevant client information (such as the gateway address or giaddr)
   to a network management system, or it will retrieve the usage
   description itself by resolving the URL.

   DHCP servers may implement MUD functionality themselves or they may
   pass along appropriate information to a network management system or
   MUD controller.  A DHCP server that does process the MUD URL MUST
   adhere to the process specified in [RFC2818] and [RFC5280] to
   validate the TLS certificate of the web server hosting the MUD file.
   Those servers will retrieve the file, process it, create and install
   the necessary configuration on the relevant network element.  Servers
   SHOULD monitor the gateway for state changes on a given interface.  A
   DHCP server that does not provide MUD functionality and has forwarded
   a MUD URL to a MUD controller MUST notify the MUD controller of any
   corresponding change to the DHCP state of the client (such as
   expiration or explicit release of a network address lease).



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9.3.  Relay Requirements

   There are no additional requirements for relays.

10.  The Manufacturer Usage Description (MUD) URL X.509 Extension

   This section defines an X.509 non-critical certificate extension that
   contains a single Uniform Resource Locator (URL) that points to an
   on-line Manufacturer Usage Description concerning the certificate
   subject.  URI must be represented as described in Section 7.4 of
   [RFC5280].

   Any Internationalized Resource Identifiers (IRIs) MUST be mapped to
   URIs as specified in Section 3.1 of [RFC3987] before they are placed
   in the certificate extension.

   The semantics of the URL are defined Section 5 of this document.

   The choice of id-pe is based on guidance found in Section 4.2.2 of
   [RFC5280]:

         These extensions may be used to direct applications to on-line
         information about the issuer or the subject.


   The MUD URL is precisely that: online information about the
   particular subject.

   The new extension is identified as follows:






















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   <CODE BEGINS>

     MUDURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
                  internet(1) security(5) mechanisms(5) pkix(7)
                  id-mod(0) id-mod-mudURLExtn2016(88) }

     DEFINITIONS IMPLICIT TAGS ::= BEGIN

     -- EXPORTS ALL --

     IMPORTS
       EXTENSION
       FROM PKIX-CommonTypes-2009
               { iso(1) identified-organization(3) dod(6) internet(1)
                 security(5) mechanisms(5) pkix(7) id-mod(0)
                 id-mod-pkixCommon-02(57) }

       id-pe
       FROM PKIX1Explicit-2009
               { iso(1) identified-organization(3) dod(6) internet(1)
                 security(5) mechanisms(5) pkix(7) id-mod(0)
                 id-mod-pkix1-explicit-02(51) } ;
       MUDCertExtensions EXTENSION ::= { ext-MUDURL, ... }
       ext-MUDURL EXTENSION ::= { SYNTAX MUDURLSyntax
       IDENTIFIED BY id-pe-mud-url }

       id-pe-mud-url OBJECT IDENTIFIER ::= { id-pe 25 }

       MUDURLSyntax ::= IA5String

       END

   <CODE ENDS>

   While this extension can appear in either an 802.AR manufacturer
   certificate (IDevID) or deployment certificate (LDevID), of course it
   is not guaranteed in either, nor is it guaranteed to be carried over.
   It is RECOMMENDED that MUD controller implementations maintain a
   table that maps a Thing to its MUD-URL based on IDevIDs.

11.  The Manufacturer Usage Description LLDP extension

   The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop
   vendor-neutral link layer protocol used by end hosts network Things
   for advertising their identity, capabilities, and neighbors on an
   IEEE 802 local area network.  Its Type-Length-Value (TLV) design
   allows for 'vendor-specific' extensions to be defined.  IANA has a
   registered IEEE 802 organizationally unique identifier (OUI) defined



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   as documented in [RFC7042].  The MUD LLDP extension uses a subtype
   defined in this document to carry the MUD URL.

   The LLDP vendor specific frame has the following format:

   +--------+--------+----------+---------+--------------
   |TLV Type|  len   |   OUI    |subtype  | MUD URL
   |  =127  |        |= 00 00 5E|  = 1    |
   |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets)
   +--------+--------+----------+---------+--------------


   where:

   o  TLV Type = 127 indicates a vendor-specific TLV

   o  len - indicates the TLV string length

   o  OUI = 00 00 5E is the organizationally unique identifier of IANA

   o  subtype = 1 (to be assigned by IANA for the MUD URL)

   o  MUD URL - the length MUST NOT exceed 255 octets

   The intent of this extension is to provide both a new Thing
   classifier to the network as well as some recommended configuration
   to the routers that implement policy.  However, it is entirely the
   purview of the network system as managed by the network administrator
   to decide what to do with this information.  The key function of this
   extension is simply to identify the type of Thing to the network in a
   structured way such that the policy can be easily found with existing
   toolsets.

   Hosts, routers, or other network Things that implement this option
   are intended to have at most one MUD URL associated with them, so
   they may transmit at most one MUD URL value.

   Hosts, routers, or other network Things that implement this option
   may ignore these options or take action based on receipt of these
   options.  For example they may fill in information in the respective
   extensions of the LLDP Management Information Base (LLDP MIB).  LLDP
   operates in a one-way direction.  LLDPDUs are not exchanged as
   information requests by one Thing and response sent by another Thing.
   The other Things do not acknowledge LLDP information received from a
   Thing.  No specific network behavior is guaranteed.  When a Thing
   consumes this extension, it may either forward the URL and relevant
   remote Thing information to a MUD controller, or it will retrieve the




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   usage description by resolving the URL in accordance with normal HTTP
   semantics.

12.  Creating and Processing of Signed MUD Files

   Because MUD files contain information that may be used to configure
   network access lists, they are sensitive.  To insure that they have
   not been tampered with, it is important that they be signed.  We make
   use of DER-encoded Cryptographic Message Syntax (CMS) [RFC5652] for
   this purpose.

12.1.  Creating a MUD file signature

   A MUD file MUST be signed using CMS as an opaque binary object.  In
   order to make successful verification more likely, intermediate
   certificates SHOULD be included.  The signature is stored at the same
   location as the MUD URL but with the suffix of ".p7s".  Signatures
   are transferred using content-type "application/pkcs7-signature".

   For example:

   % openssl cms -sign -signer mancertfile -inkey mankey \
                 -in mudfile -binary -outform DER - \
                 -certfile intermediatecert -out mudfile.p7s

   Note: A MUD file may need to be re-signed if the signature expires.

12.2.  Verifying a MUD file signature

   Prior to retrieving a MUD file the MUD controller SHOULD retrieve the
   MUD signature file using the MUD URL with a suffix of ".p7s".  For
   example, if the MUD URL is "https://example.com/.well-known/v1/
   modela", the MUD signature URL will be "https://example.com/.well-
   known/v1/modela.p7s".

   Upon retrieving a MUD file, a MUD controller MUST validate the
   signature of the file before continuing with further processing.  A
   MUD controller MUST cease processing of that file it cannot validate
   the chain of trust to a known trust anchor until an administrator has
   given approval.

   The purpose of the signature on the file is to assign accountability
   to an entity, whose reputation can be used to guide administrators on
   whether or not to accept a given MUD file.  It is already common
   place to check web reputation on the location of a server on which a
   file resides.  While it is likely that the manufacturer will be the
   signer of the file, this is not strictly necessary, and may not be
   desirable.  For one thing, in some environments, integrators may



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   install their own certificates.  For another, what is more important
   is the accountability of the recommendation, and not the
   cryptographic relationship between the device and the file.

   An example:

   % openssl cms -verify -in mudfile.p7s -inform DER -content mudfile

   Note the additional step of verifying the common trust root.

13.  Extensibility

   One of our design goals is to see that MUD files are able to be
   understood by as broad a cross-section of systems as is possible.
   Coupled with the fact that we have also chosen to leverage existing
   mechanisms, we are left with no ability to negotiate extensions and a
   limited desire for those extensions in any event.  A such, a two-tier
   extensibility framework is employed, as follows:

   1.  At a coarse grain, a protocol version is included in a MUD URL.
       This memo specifies MUD version 1.  Any and all changes are
       entertained when this version is bumped.  Transition approaches
       between versions would be a matter for discussion in future
       versions.

   2.  At a finer grain, only extensions that would not incur additional
       risk to the Thing are permitted.  Specifically, adding nodes to
       the mud container is permitted with the understanding that such
       additions will be ignored by unaware implementations.  Any such
       extensions SHALL be standardized through the IETF process, and
       MUST be named in the "extensions" list.  MUD controllers MUST
       ignore YANG nodes they do not understand and SHOULD create an
       exception to be resolved by an administrator, so as to avoid any
       policy inconsistencies.

14.  Deployment Considerations

   Because MUD consists of a number of architectural building blocks, it
   is possible to assemble different deployment scenarios.  One key
   aspect is where to place policy enforcement.  In order to protect the
   Thing from other Things within a local deployment, policy can be
   enforced on the nearest switch or access point.  In order to limit
   unwanted traffic within a network, it may also be advisable to
   enforce policy as close to the Internet as possible.  In some
   circumstances, policy enforcement may not be available at the closest
   hop.  At that point, the risk of so-called east-west infection is
   increased to the number of Things that are able to communicate
   without protection.



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   A caution about some of the classes: admission of a Thing into the
   "manufacturer" and "same-manufacturer" class may have impact on
   access of other Things.  Put another way, the admission may grow the
   access-list on switches connected to other Things, depending on how
   access is managed.  Some care should be given on managing that
   access-list growth.  Alternative methods such as additional network
   segmentation can be used to keep that growth within reason.

15.  Security Considerations

   Based on how a MUD-URL is emitted, a Thing may be able to lie about
   what it is, thus gaining additional network access.  There are
   several means to limit risk in this case.  The most obvious is to
   only believe Things that make use of certificate-based authentication
   such as IEEE 802.1AR certificates.  When those certificates are not
   present, Things claiming to be of a certain manufacturer SHOULD NOT
   be included in that manufacturer grouping without additional
   validation of some form.  This will occur when it makes use of
   primitives such as "manufacturer" for the purpose of accessing Things
   of a particular type.  Similarly, network management systems may be
   able to fingerprint the Thing.  In such cases, the MUD-URL can act as
   a classifier that can be proven or disproven.  Fingerprinting may
   have other advantages as well: when 802.1AR certificates are used,
   because they themselves cannot change, fingerprinting offers the
   opportunity to add artificats to the MUD-URL.  The meaning of such
   artifacts is left as future work.

   Network management systems SHOULD NOT accept a usage description for
   a Thing with the same MAC address that has indicated a change of
   authority without some additional validation (such as review by a
   network administrator).  New Things that present some form of
   unauthenticated MUD URL SHOULD be validated by some external means
   when they would be otherwise be given increased network access.

   It may be possible for a rogue manufacturer to inappropriately
   exercise the MUD file parser, in order to exploit a vulnerability.
   There are three recommended approaches to address this threat.  The
   first is to validate the signature of the MUD file.  The second is to
   have a system do a primary scan of the file to ensure that it is both
   parseable and believable at some level.  MUD files will likely be
   relatively small, to start with.  The number of ACEs used by any
   given Thing should be relatively small as well.  It may also be
   useful to limit retrieval of MUD URLs to only those sites that are
   known to have decent web or domain reputations.

   Use of a URL necessitates the use of domain names.  If a domain name
   changes ownership, the new owner of that domain may be able to
   provide MUD files that MUD controllers would consider valid.  There



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   are a few approaches that can mitigate this attack.  First, MUD
   controllers SHOULD cache certificates used by the MUD file server.
   When a new certificate is retrieved for whatever reason, the MUD
   controller should check to see if ownership of the domain has
   changed.  A fair programmatic approximation of this is when the name
   servers for the domain have changed.  If the actual MUD file has
   changed, the controller MAY check the WHOIS database to see if
   registration ownership of a domain has changed.  If a change has
   occured, or if for some reason it is not possible to determine
   whether ownership has changed, further review may be warranted.
   Note, this remediation does not take into account the case of a Thing
   that was produced long ago and only recently fielded, or the case
   where a new MUD controller has been installed.

   It may not be possible for a MUD controller to retrieve a MUD file at
   any given time.  Should a MUD controller fail to retrieve a MUD file,
   it SHOULD consider the existing one safe to use, at least for a time.
   After some period, it SHOULD log that it has been unable to retrieve
   the file.  There may be very good reasons for such failures,
   including the possibility that the MUD controller is in an off-line
   environment, the local Internet connection has failed, or the remote
   Internet connection has failed.  It is also possible that an attacker
   is attempting to prevent onboarding of a device.  It is a local
   deployment decision as to whether or not devices may be onboarded in
   the face of such failures.

   The release of a MUD URL by a Thing reveals what the Thing is, and
   provides an attacker with guidance on what vulnerabilities may be
   present.

   While the MUD URL itself is not intended to be unique to a specific
   Thing, the release of the URL may aid an observer in identifying
   individuals when combined with other information.  This is a privacy
   consideration.

   In addressing both of these concerns, implementors should take into
   account what other information they are advertising through
   mechanisms such as mDNS[RFC6872], how a Thing might otherwise be
   identified, perhaps through how it behaves when it is connected to
   the network, whether a Thing is intended to be used by individuals or
   carry personal identifying information, and then apply appropriate
   data minimization techniques.  One approach is to make use of TEAP
   [RFC7170] as the means to share information with authorized
   components in the network.  Network Things may also assist in
   limiting access to the MUD-URL through the use of mechanisms such as
   DHCPv6-Shield [RFC7610].





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   Please note that the security considerations mentioned in Section 4.7
   of [I-D.ietf-netmod-rfc6087bis] are not applicable in this case
   because the YANG serialization is not intended to be accessed via
   NETCONF.  However, for those who try to instantiate this model in a
   Thing via NETCONF, all objects in each model in this draft exhibit
   similar security characteristics as [I-D.ietf-netmod-acl-model].  The
   basic purpose of MUD is to configure access, and so by its very
   nature can be disruptive if used by unauthorized parties.

16.  IANA Considerations

16.1.  YANG Module Registrations

   The following YANG modules are requested to be registred in the "IANA
   Module Names" registry:

   The ietf-mud module:

   o  Name: ietf-mud

   o  XML Namespace: urn:ietf:params:xml:ns:yang:ietf-mud

   o  Prefix: ief-mud

   o  Reference: This memo

   The ietf-acldns module:

   o  Name: ietf-acldns

   o  XML Namespace: urn:ietf:params:xml:ns:yang:ietf-acldns

   o  Prefix: ietf-acldns

   o  Reference: This memo

16.2.  DHCPv4 and DHCPv6 Options

   The IANA has allocated option 161 in the Dynamic Host Configuration
   Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters registry
   for the MUD DHCPv4 option.

   IANA is requested to allocated the DHCPv4 and v6 options as specified
   in Section 9.







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16.3.  PKIX Extensions

   IANA is kindly requested to make the following assignments for:

   o The MUDURLExtnModule-2016 ASN.1 module in the "SMI Security for
   PKIX Module Identifier" registry (1.3.6.1.5.5.7.0).

   o id-pe-mud-url object identifier from the "SMI Security for PKIX
   Certificate Extension" registry (1.3.6.1.5.5.7.1).

   The use fo these values is specified in Section 10.

16.4.  Well Known URI Suffix

   The IANA has allocated the URL suffix of "mud" as follows:

   o URI Suffix: "mud" o Specification documents: this document o
   Related information: n/a

16.5.  MIME Media-type Registration for MUD files

   The following media-type is defined for transfer of MUD file:





























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    o Type name: application
    o Subtype name: mud+json
    o Required parameters: n/a
    o Optional parameters: n/a
    o Encoding considerations: 8bit; application/mud+json values
      are represented as a JSON object; UTF-8 encoding SHOULD be
      employed.
    o Security considerations: See {{secon}} of this document.
    o Interoperability considerations: n/a
    o Published specification: this document
    o Applications that use this media type: MUD controllers as
      specified by this document.
    o Fragment identifier considerations: n/a
    o Additional information:

        Magic number(s): n/a
        File extension(s): n/a
        Macintosh file type code(s): n/a

    o Person & email address to contact for further information:
      Eliot Lear <lear@cisco.com>, Ralph Droms <rdroms@cisco.com>
    o Intended usage: COMMON
    o Restrictions on usage: none
    o Author:
         Eliot Lear <lear@cisco.com>
         Ralph Droms <rdroms@cisco.com>
    o Change controller: IESG
    o Provisional registration? (standards tree only): No.


16.6.  LLDP IANA TLV Subtype Registry

   IANA is requested to create a new registry for IANA Link Layer
   Discovery Protocol (LLDP) TLV subtype values.  The recommended policy
   for this registry is Expert Review.  The maximum number of entries in
   the registry is 256.

   IANA is required to populate the initial registry with the value:

   LLDP subtype value = 1 (All the other 255 values should be initially
   marked as 'Unassigned'.)

   Description = the Manufacturer Usage Description (MUD) Uniform
   Resource Locator (URL)

   Reference = < this document >





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16.7.  The MUD Well Known Universal Resource Name (URNs)

   The following parameter registry is requested to be added in
   accordance with [RFC3553]

      Registry name: "urn:ietf:params:mud" is requested.
      Specification: this document
      Repository: this document
      Index value:  Encoded identically to a TCP/UDP port service
                    name, as specified in Section 5.1 of [RFC6335]

   The following entries should be added to the "urn:ietf:params:mud"
   name space:

   "urn:ietf:params:mud:dns" refers to the service specified by
   [RFC1123].  "urn:ietf:params:mud:ntp" refers to the service specified
   by [RFC5905].

16.8.  Extensions Registry

   The IANA is requested to establish a registry of extensions as
   follows:

      Registry name: MUD extensions registry
      Registry policy: Standards action
      Standard reference: document
      Extension name: UTF-8 encoded string, not to exceed 40 characters.

   Each extension MUST follow the rules specified in this specification.
   As is usual, the IANA issues early allocations based in accordance
   with [RFC7120].

17.  Acknowledgments

   The authors would like to thank Einar Nilsen-Nygaard, who
   singlehandedly updated the model to match the updated ACL model,
   Bernie Volz, Tom Gindin, Brian Weis, Sandeep Kumar, Thorsten Dahm,
   John Bashinski, Steve Rich, Jim Bieda, Dan Wing, Joe Clarke, Henk
   Birkholz, Adam Montville, and Robert Sparks for their valuable advice
   and reviews.  Russ Housley entirely rewrote Section 10 to be a
   complete module.  Adrian Farrel provided the basis for privacy
   considerations text.  Kent Watson provided a thorough review of the
   architecture and the YANG model.  The remaining errors in this work
   are entirely the responsibility of the authors.







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18.  References

18.1.  Normative References

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
              S., and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-07 (work in progress), July 2017.

   [I-D.ietf-netmod-acl-model]
              Jethanandani, M., Huang, L., Agarwal, S., and D. Blair,
              "Network Access Control List (ACL) YANG Data Model",
              draft-ietf-netmod-acl-model-13 (work in progress),
              September 2017.

   [IEEE8021AB]
              Institute for Electrical and Electronics Engineers, "IEEE
              Standard for Local and Metropolitan Area Networks--
              Station and Media Access Control Connectivity Discovery",
              n.d..

   [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, RFC 1123,
              DOI 10.17487/RFC1123, October 1989, <https://www.rfc-
              editor.org/info/rfc1123>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
              editor.org/info/rfc2119>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <https://www.rfc-editor.org/info/rfc2131>.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000, <https://www.rfc-
              editor.org/info/rfc2818>.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <https://www.rfc-editor.org/info/rfc3315>.







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   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
              <https://www.rfc-editor.org/info/rfc3748>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
              January 2005, <https://www.rfc-editor.org/info/rfc3987>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/info/rfc5652>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <https://www.rfc-editor.org/info/rfc5905>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010, <https://www.rfc-
              editor.org/info/rfc6020>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7120]  Cotton, M., "Early IANA Allocation of Standards Track Code
              Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
              2014, <https://www.rfc-editor.org/info/rfc7120>.



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   [RFC7227]  Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
              <https://www.rfc-editor.org/info/rfc7227>.

   [RFC7610]  Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield:
              Protecting against Rogue DHCPv6 Servers", BCP 199,
              RFC 7610, DOI 10.17487/RFC7610, August 2015,
              <https://www.rfc-editor.org/info/rfc7610>.

18.2.  Informative References

   [FW95]     Chapman, D. and E. Zwicky, "Building Internet Firewalls",
              January 1995.

   [I-D.ietf-netmod-rfc6087bis]
              Bierman, A., "Guidelines for Authors and Reviewers of YANG
              Data Model Documents", draft-ietf-netmod-rfc6087bis-14
              (work in progress), September 2017.

   [IEEE8021AR]
              Institute for Electrical and Electronics Engineers,
              "Secure Device Identity", 1998.

   [ISO.8601.1988]
              International Organization for Standardization, "Data
              elements and interchange formats - Information interchange
              - Representation of dates and times", ISO Standard 8601,
              June 1988.

   [RFC1984]  IAB and IESG, "IAB and IESG Statement on Cryptographic
              Technology and the Internet", BCP 200, RFC 1984,
              DOI 10.17487/RFC1984, August 1996, <https://www.rfc-
              editor.org/info/rfc1984>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC3553]  Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
              IETF URN Sub-namespace for Registered Protocol
              Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
              2003, <https://www.rfc-editor.org/info/rfc3553>.








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   [RFC6092]  Woodyatt, J., Ed., "Recommended Simple Security
              Capabilities in Customer Premises Equipment (CPE) for
              Providing Residential IPv6 Internet Service", RFC 6092,
              DOI 10.17487/RFC6092, January 2011, <https://www.rfc-
              editor.org/info/rfc6092>.

   [RFC6872]  Gurbani, V., Ed., Burger, E., Ed., Anjali, T., Abdelnur,
              H., and O. Festor, "The Common Log Format (CLF) for the
              Session Initiation Protocol (SIP): Framework and
              Information Model", RFC 6872, DOI 10.17487/RFC6872,
              February 2013, <https://www.rfc-editor.org/info/rfc6872>.

   [RFC7042]  Eastlake 3rd, D. and J. Abley, "IANA Considerations and
              IETF Protocol and Documentation Usage for IEEE 802
              Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042,
              October 2013, <https://www.rfc-editor.org/info/rfc7042>.

   [RFC7170]  Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna,
              "Tunnel Extensible Authentication Protocol (TEAP) Version
              1", RFC 7170, DOI 10.17487/RFC7170, May 2014,
              <https://www.rfc-editor.org/info/rfc7170>.

   [RFC7452]  Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
              "Architectural Considerations in Smart Object Networking",
              RFC 7452, DOI 10.17487/RFC7452, March 2015,
              <https://www.rfc-editor.org/info/rfc7452>.

   [RFC7488]  Boucadair, M., Penno, R., Wing, D., Patil, P., and T.
              Reddy, "Port Control Protocol (PCP) Server Selection",
              RFC 7488, DOI 10.17487/RFC7488, March 2015,
              <https://www.rfc-editor.org/info/rfc7488>.

Appendix A.  Changes from Earlier Versions

   RFC Editor to remove this section prior to publication.

   Draft -09 to -10:

   o  AD input.

   o  Correct dates.

   o  Add compliance sentence as to which ACL module features are
      implemented.

   Draft -08 to -09:





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   o  Resolution of Security Area review, IoT directorate review, GenART
      review, YANG doctors review.

   o  change of YANG structure to address mandatory nodes.

   o  Terminology cleanup.

   o  specify out extra portion of MUD-URL.

   o  consistency changes.

   o  improved YANG descriptions.

   o  Remove extra revisions.

   o  Track ACL model changes.

   o  Additional cautions on use of ACL model; further clarifications on
      extensions.

   Draft -07 to -08:

   o  a number of editorials corrected.

   o  definition of MUD file tweaked.

   Draft -06 to -07:

   o  Examples updated.

   o  Additional clarification for direction-initiated.

   o  Additional implementation guidance given.

   Draft -06 to -07:

   o  Update models to match new ACL model

   o  extract directionality from the ACL, introducing a new device
      container.

   Draft -05 to -06:

   o  Make clear that this is a component architecture (Polk and Watson)

   o  Add order of operations (Watson)

   o  Add extensions leaf-list (Pritikin)



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   o  Remove previous-mud-file (Watson)

   o  Modify text in last-update (Watson)

   o  Clarify local networks (Weis, Watson)

   o  Fix contact info (Watson)

   o  Terminology clarification (Weis)

   o  Advice on how to handle LDevIDs (Watson)

   o  Add deployment considerations (Watson)

   o  Add some additional text about fingerprinting (Watson)

   o  Appropriate references to 6087bis (Watson)

   o  Change systeminfo to a URL to be referenced (Lear)

   Draft -04 to -05: * syntax error correction

   Draft -03 to -04: * Re-add my-controller

   Draft -02 to -03: * Additional IANA updates * Format correction in
   YANG.  * Add reference to TEAP.

   Draft -01 to -02: * Update IANA considerations * Accept Russ Housley
   rewrite of X.509 text * Include privacy considerations text * Redo
   the URL limit.  Still 255 bytes, but now stated in the URL
   definition.  * Change URI registration to be under urn:ietf:params

   Draft -00 to -01: * Fix cert trust text.  * change supportInformation
   to meta-info * Add an informational element in.  * add urn registry
   and create first entry * add default elements

Appendix B.  Default MUD nodes

   What follows is a MUD file that permits DNS traffic to a controller
   that is registered with the URN "urn:ietf:params:mud:dns" and traffic
   NTP to a controller that is registered "urn:ietf:params:mud:ntp".
   This is considered the default behavior and the ACEs are in effect
   appended to whatever other ACEs.  To block DNS or NTP one repeats the
   matching statement but replace "permit" with deny.  Because ACEs are
   processed in the order they are received, the defaults would not be
   reached.  A MUD controller might further decide to optimize to simply
   not include the defaults when they are overriden.




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   The access-list component of the MUD entry is included below.

   {
    "ietf-access-control-list:access-lists": {
       "acl": [
         {
           "acl-name": "mud-67390-v4to",
           "acl-type": "ipv4-acl",
           "aces": {
             "ace": [
               {
                 "rule-name": "ent0-todev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:dns"
                   },
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                   }
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               },
               {
                 "rule-name": "ent1-todev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:ntp"
                   },
                   "protocol": 17
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               }
             ]
           }
         },
         {
           "acl-name": "mud-67390-v4fr",
           "acl-type": "ipv4-acl",



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           "access-list-entries": {
             "ace": [
               {
                 "rule-name": "ent0-frdev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:dns"
                   },
                   "protocol": 17,
                   "destination-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                   }
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               },
               {
                 "rule-name": "ent1-frdev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:ntp"
                   },
                   "protocol": 17
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               }
             ]
           }
         },
         {
           "acl-name": "mud-67390-v6to",
           "acl-type": "ipv6-acl",
           "aces": {
             "ace": [
               {
                 "rule-name": "ent0-todev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:dns"
                   },



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                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                   }
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               },
               {
                 "rule-name": "ent1-todev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:ntp"
                   },
                   "protocol": 17
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               }
             ]
           }
         },
         {
           "acl-name": "mud-67390-v6fr",
           "acl-type": "ipv6-acl",
           "aces": {
             "ace": [
               {
                 "rule-name": "ent0-frdev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:dns"
                   },
                   "protocol": 17,
                   "destination-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                   }
                 },
                 "actions": {
                   "permit": [



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                     null
                   ]
                 }
               },
               {
                 "rule-name": "ent1-frdev",
                 "matches": {
                   "ietf-mud:mud-acl"{
                     "controller": "urn:ietf:params:mud:ntp"
                   },
                   "protocol": 17
                 },
                 "actions": {
                   "permit": [
                     null
                   ]
                 }
               }
             ]
           }
         }
       ]
     }

Appendix C.  A Sample Extension: DETNET-indicator

   In this sample extension we augment the core MUD model to indicate
   whether the device implements DETNET.  If a device later attempts to
   make use of DETNET, an notification or exception might be generated.
   Note that this example is intended only for illustrative purposes.

 Extension Name: "Example-Extension" (to be used in the extensions list)
 Standard: this document (but do not register the example)


   This extension augments the MUD model to include a single node, using
   the following sample module that has the following tree structure:

   module: ietf-mud-detext-example
     augment /ietf-mud:mud:
       +--rw is-detnet-required?   boolean


   The model is defined as follows:

   <CODE BEGINS>file "ietf-mud-detext-example@2016-09-07.yang"
   module ietf-mud-detext-example {
     yang-version 1.1;



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     namespace "urn:ietf:params:xml:ns:yang:ietf-mud-detext-example";
     prefix ietf-mud-detext-example;

     import ietf-mud {
       prefix ietf-mud;
     }

     organization
       "IETF OPSAWG (Ops Area) Working Group";
     contact
       "WG Web: http://tools.ietf.org/wg/opsawg/
        WG List: opsawg@ietf.org
        Author: Eliot Lear
        lear@cisco.com
        Author: Ralph Droms
        rdroms@gmail.com
        Author: Dan Romascanu
        dromasca@gmail.com

       ";
     description
       "Sample extension to a MUD module to indicate a need
        for DETNET support.";

     revision 2017-09-05 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Manufacturer Usage Description
          Specification";
     }

     augment "/ietf-mud:mud" {
       description
         "This adds a simple extension for a manufacturer
           to indicate whether DETNET is required by a
          device.";
       leaf is-detnet-required {
         type boolean;
         description
           "This value will equal true if a device requires
            detnet to properly function";
       }
     }
   }
   <CODE ENDS>





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   Using the previous example, we now show how the extension would be
   expressed:

 {
   "ietf-mud:mud": {
     "mud-url": "https://bms.example.com/.well-known/mud/v1/lightbulb2",
     "last-update": "2017-08-30T15:48:42+02:00",
     "systeminfo": "https://bms.example.com/descriptions/lightbulb2",
     "cache-validity": 48,
     "extensions": [
         "ietf-mud-detext-example"
      ],
     "ietf-mud-detext-example:is-detnet-required": "false",
     "from-device-policy": {
       "access-lists": {
         "access-list": [
           {
             "acl-name": "mud-16595-v6fr",
             "acl-type": "ietf-access-control-list:ipv6-acl"
           }
         ]
       }
     },
     "to-device-policy": {
       "access-lists": {
         "access-list": [
           {
             "acl-name": "mud-16595-v4to",
             "acl-type": "ietf-access-control-list:ipv6-acl"
           }
         ]
       }
     }
   },
   "ietf-access-control-list:access-lists": {
     "acl": [
       {
         "acl-name": "mud-16595-v6to",
         "acl-type": "ipv6-acl",
         "access-list-entries": {
           "ace": [
             {
               "rule-name": "cl0-todev",
               "matches": {
                 "ipv4-acl": {
                   "ietf-acldns:src-dnsname": "service.bms.example.com"
                 },
                 "protocol": 6,



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                 "source-port-range": {
                   "lower-port": 443,
                   "upper-port": 443
                 },
                 "tcp-acl": {
                   "ietf-mud:direction-initiated": "to-device"
                 }
               },
               "actions": {
                 "permit": [
                   null
                 ]
               }
             }
           ]
         }
       },
       {
         "acl-name": "mud-16595-v6fr",
         "acl-type": "ipv6-acl",
         "aces": {
           "ace": [
             {
               "rule-name": "cl0-frdev",
               "matches": {
                 "ipv6-acl": {
                   "ietf-acldns:dst-dnsname": "service.bms.example.com"
                 },
                 "protocol": 6,
                 "destination-port-range": {
                   "lower-port": 443,
                   "upper-port": 443
                 },
                 "tcp-acl": {
                   "ietf-mud:direction-initiated": "to-device"
                 }
               },
               "actions": {
                 "permit": [
                   null
                 ]
               }
             }
           ]
         }
       }
     ]
   }



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 }


Authors' Addresses

   Eliot Lear
   Cisco Systems
   Richtistrasse 7
   Wallisellen  CH-8304
   Switzerland

   Phone: +41 44 878 9200
   Email: lear@cisco.com


   Ralph Droms

   Phone: +1 978 376 3731
   Email: rdroms@gmail.com


   Dan Romascanu

   Phone: +972 54 5555347
   Email: dromasca@gmail.com


























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