Network Working Group                                            E. Lear
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                R. Droms
Expires: November 16, 2017 January 4, 2018
                                                            D. Romascanu
                                                            May 15,
                                                           July 03, 2017

              Manufacturer Usage Description Specification


   This memo specifies a component-based architecture for manufacturer
   usage descriptions (MUD).  This includes 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

Status of This Memo

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   This Internet-Draft will expire on November 16, 2017. January 4, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  What MUD doesn't do . . . . . . . . . . . . . . . . . . .   4
     1.2.  A Simple Example  . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Determining Intended Use  . . . . . . . . . . . . . . . .   5
     1.4.  Finding A Policy: The MUD URL . . . . . . . . . . . . . .   5
     1.5.  Types of Policies . . . . . . . . . . . . . . . . . . . .   6
     1.6.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   7
     1.7.  The Manufacturer Usage Description Architecture . . . . .   8
     1.8.  Order of operations . . . . . . . . . . . . . . . . . . .   9
   2.  The MUD Model and Semantic Meaning  . . . . . . . . . . . . .   9
   3.  Element Definitions . . . . . . . . . . . . . . . . . . . . .  10  11
     3.1.  last-update . . . . . . . . . . . . . . . . . . . . . . .  10  11
     3.2.  cache-validity  . . . . . . . . . . . . . . . . . . . . .  11
     3.3.  masa-server . . . . . . . . . . . . . . . . . . . . . . .  11  12
     3.4.  is-supported  . . . . . . . . . . . . . . . . . . . . . .  11  12
     3.5.  systeminfo  . . . . . . . . . . . . . . . . . . . . . . .  11  12
     3.6.  extensions  . . . . . . . . . . . . . . . . . . . . . . .  11  12
     3.7.  packet-direction  . . . . . . . . . . . . . . . . . . . .  11  12
     3.8.  manufacturer  . . . . . . . . . . . . . . . . . . . . . .  12
     3.9.  same-manufacturer . . . . . . . . . . . . . . . . . . . .  12  13
     3.10. model . . . . . . . . . . . . . . . . . . . . . . . . . .  12  13
     3.11. local-networks  . . . . . . . . . . . . . . . . . . . . .  12  13
     3.12. controller  . . . . . . . . . . . . . . . . . . . . . . .  12  13
     3.13. my-controller . . . . . . . . . . . . . . . . . . . . . .  12  13
     3.14. direction-initiated . . . . . . . . . . . . . . . . . . .  13
   4.  Processing of the MUD file  . . . . . . . . . . . . . . . . .  13  14
   5.  What does a MUD URL look like?  . . . . . . . . . . . . . . .  13  14
   6.  The MUD YANG Model  . . . . . . . . . . . . . . . . . . . . .  14  15
   7.  The Domain Name Extension to the ACL Model  . . . . . . . . .  17  20
     7.1.  source-dnsname  . . . . . . . . . . . . . . . . . . . . .  18  21
     7.2.  destination-dnsname . . . . . . . . . . . . . . . . . . .  18  21
     7.3.  The ietf-acldns Model . . . . . . . . . . . . . . . . . .  18  21
   8.  MUD File Example  . . . . . . . . . . . . . . . . . . . . . .  20  22
   9.  The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . .  21  24
     9.1.  Client Behavior . . . . . . . . . . . . . . . . . . . . .  22  25
     9.2.  Server Behavior . . . . . . . . . . . . . . . . . . . . .  22  25
     9.3.  Relay Requirements  . . . . . . . . . . . . . . . . . . .  23  26
   10. The Manufacturer Usage Description (MUD) URL X.509 Extension   23   26
   11. The Manufacturer Usage Description LLDP extension . . . . . .  24  27
   12. Creating and Processing of Signed MUD Files . . . . . . . . .  26  29
     12.1.  Creating a MUD file signature  . . . . . . . . . . . . .  26  29
     12.2.  Verifying a MUD file signature . . . . . . . . . . . . .  26  29
   13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . .  27  30
   14. Deployment Considerations . . . . . . . . . . . . . . . . . .  27  30
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  28  31
   16. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  29  32
     16.1.  YANG Module Registrations  . . . . . . . . . . . . . . .  29  32
     16.2.  DHCPv4 and DHCPv6 Options  . . . . . . . . . . . . . . .  30  33
     16.3.  PKIX Extensions  . . . . . . . . . . . . . . . . . . . .  30  33
     16.4.  Well Known URI Suffix  . . . . . . . . . . . . . . . . .  30  33
     16.5.  MIME Media-type Registration for MUD files . . . . . . .  30  33
     16.6.  LLDP IANA TLV Subtype Registry . . . . . . . . . . . . .  31  34
     16.7.  The MUD Well Known Universal Resource Name (URNs)  . . .  32  35
   17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  32  35
   18. References  . . . . . . . . . . . . . . . . . . . . . . . . .  32  35
     18.1.  Normative References . . . . . . . . . . . . . . . . . .  32  35
     18.2.  Informative References . . . . . . . . . . . . . . . . .  35  38
   Appendix A.  Changes from Earlier Versions  . . . . . . . . . . .  36  39
   Appendix B.  Default MUD elements . . . . . . . . . . . . . . . .  37  40
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  42  45

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 therefore
   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
   device that has a built in Linux stack, it might be 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 of MUD is to therefore 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

   MUD therefore 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 to retrieve the description.

   In this specification we specify 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 enterprise
   networks for their own purposes.

1.1.  What MUD doesn't do

   General computing systems will benefit very little from MUD, 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 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.

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 Facebook 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].  Programmatically profiling systems have existed
   for years as well.  These systems make use of heuristics that take at
   least some time to assert what a system is.

   A system 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 implement such an approach.  To date, such an
   assertion has held true.

1.4.  Finding A Policy: The MUD URL

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

   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 other method defined is an X.509
   constraint.  The IEEE has developed [IEEE8021AR] that provides a
   certificate-based approach to communicate device characteristics,
   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, if a device has a serial number,
   it may be possible for the MUD controller to perform a lookup of the
   device, if it has some knowledge as to who the device manufacturer
   is, and what its MUD file server is.  Such mechanisms are not
   described in this memo, but are possible.

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 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 who need to speak 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
   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.

   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, and by
   leveraging YANG-based models, we provide the opportunity for new
   policies to be introduced as required.

   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 are 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:  A device that the local network administrator admits to
      the particular class.

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

   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 therefore, mature.  Therefore, only a a
   limited subset YANG-based configuration of is permitted in a MUD

1.6.  Terminology

   MUD:  manufacturer usage description.

   MUD file:  a file containing YANG-based JSON that describes a
      recommended 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 end device that emits 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
      device.  It could, for instance, be a systems integrator, or even
      a component provider.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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.

    .                      ____________     .           _____________
    .                     |            |    .          |             |
    .                     |    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 URI is communicated.
   For instance, in the case of DHCP, the DHCP server might receive the
   URI and then process it.  In the case of IEEE 802.1X, the switch
   would carry the URI 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 device's connection, or as specified in the description.  Thus if
   the device is mobile, when it moves on, any configuration in the
   switch is removed.  Similarly, from time to time the description may
   be refreshed, based on new capabilities or communication patterns or

   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 URI, it may proxy it, the trivial cases
   being a map between some registered device or port and a URL.

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

   1.  Device 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

   3.  The MUD controller retrieves the MUD file from the MUD file
       server, assuming it doesn't already have a copy.  It may test the
       URL against a reputation service, and it may test any hosts
       within the file against reputation services, as it deems fit.

   4.  The MUD controller may query the administrator for permission to
       add the device and associated policy.  If the device is known or
       the device 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 device.
       Other systems may be configured as well.

   7.  When the device 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 elements that can be modified are access lists as augmented
   by this model.  The MUD file is limited to the serialization of a
   small number of YANG schema, including the models specified in the
   following documents:

   o  [I-D.ietf-netmod-acl-model]

   o  [RFC6991]

   Publishers of MUD files MUST NOT include other elements except as
   described in Section 3.6, and MUST only contain information relevant
   to the device being described.  Devices parsing MUD files MUST cease
   processing if they find other elements.

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

   o  The first container container, metainfo, holds information that is relevant
      to retrieval and validity of the MUD file itself.

   o  The second container augments container, device, describes the access list policies to
   indicate direction be applied
      to traffic to and from the ACL device.  The only policy currently
      defined is to be applied. a list of access control lists, but the from-device-
      policy and to-device-policy containers serve as extension points
      for subsequent augmentation.

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


   o  The fourth container 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 simplified graphical representation of the data models are is used in
   this document.  The meaning of the symbols in these diagrams is
   defined in [I-D.ietf-netmod-rfc6087bis].

   module: ietf-mud
       +--rw metainfo
       |  +--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
     augment /acl:access-lists/acl:acl:
       +--rw packet-direction?   direction device
          +--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:access-list-entries/
     acl:ace/acl:matches: /acl:access-lists/acl:acl/acl:access-list-entries \
       +--rw mud-acl {mud-acl}?
          +--rw manufacturer?        inet:host
          +--rw same-manufacturer?   empty
          +--rw model?               string
          +--rw local-networks?      empty
          +--rw controller?          inet:uri
          +--rw my-controller?       empty
     augment /acl:access-lists/acl:acl/acl:access-list-entries \
       +--rw direction-initiated?   direction

3.  Element Definitions

   The following elements are defined.

3.1.  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, turn was taken from Section 5.6 of
   [RFC3339], which was taken from [ISO.8601.1988].

3.2.  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 device that is supported.

3.3.  masa-server

   This optional element refers to the URL that should be used to
   resolve the location any MASA service, as specified in

3.4.  is-supported

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

3.5.  systeminfo

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

3.6.  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
   the extensions being declared.  Implementations MUST ignore any
   elements in this file that they do not understand.

3.7.  packet-direction

   [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 device, and
   that includes indicating what is to be permitted or denied in either
   direction of communication.  This element takes a single value of
   either "to-device" or "from-device", based on a typedef "direction".
   This is applied specifically for TCP, and may be implemented either
   via stateful or stateless approaches (e.g,. TCP flags)

3.8.  manufacturer

   This element consists of a hostname that would be matched against the
   authority component of another device's MUD URL.

3.9.  same-manufacturer

   This is an equivalent for when the manufacturer element is used to
   indicate the authority that is found in another device's MUD URL
   matches that of the authority found in this device's MUD URL.

3.10.  model

   This string matches the one and only segment following the authority
   component of the MUD URL.  It refers to a model that is unique within
   the context of the authority.  It may also include product version
   information.  Thus how this field is constructed is entirely a local
   matter for the manufacturer.

3.11.  local-networks

   This null-valued element 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.

3.12.  controller

   This URI specifies a value that a controller will register with the
   mud controller.  The element then is expanded to the set of hosts
   that are so registered.  This element 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 code in certain intelligence.  Nonstandard classes may
   require substantially more care.  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.

3.13.  my-controller

   This null-valued element establishes a class of controllers that are
   intended to control the device associated with the MUD file being
   referenced. a given MUD-URL.

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 match SHOULD be applied with specific
   transport parameters, such as protocol.

4.  Processing of the MUD file

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

   o  Anything not explicitly permitted is denied.

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

   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 devices.  .well-known is used because we wish to add
   additional structure to the URL.  And so the URL appears as follows:

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

   "model" represents a device 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 device 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].

6.  The MUD YANG Model

<CODE BEGINS>file "ietf-mud@2017-04-18.yang" "ietf-mud@2017-07-03.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";

   "IETF OPSAWG (Ops Area) Working Group";

      "WG Web:
      WG List:
      Author: Eliot Lear
      Author: Ralph Droms
      Author: Dan Romascanu


   "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.

   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
   This version of this YANG module is part of RFC XXXX; see
   the RFC itself for full legal notices.";

 revision "2017-04-18" "2017-07-03"  {
   description "Base version of MUD extensions to
     "More work on ACL model"; usage.";
   reference "RFC XXXX: Manufacturer Usage Description

  typedef direction

 revision "2017-06-29"  {
     "Take packet directionality out of ACL. " +
     "Introduce device container.";
   reference "RFC XXXX: Manufacturer Usage Description

 revision "2017-04-18"  {
   description "Base version of MUD extensions to ACL model";
   reference "RFC XXXX: Manufacturer Usage Description

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

 identity mud-acl {
   base "acl:acl-base";
     "ACL that contains MUD-specific access control list entries.";

 feature mud-acl {
     "MUD ACL augmentations supported.";


 container metainfo  {

   description "Information about when support end(ed), and
                when to refresh";

   leaf last-update {
     type yang:date-and-time;
     description "This is intended to be when
                  the MUD file was generated.";

   leaf cache-validity {
     type uint8 {
       range "1..168";
     description "The information retrieved from the MUD server is
                valid for these many hours, after which it should
                be refreshed.";

   leaf masa-server {
     type inet:uri;
     description "The URI of the MASA server that network
     elements should forward requests to for this device.";

   leaf is-supported {
     type boolean;
     description "The element is currently supported
                  by the manufacturer.";
   leaf systeminfo {
     type inet:uri;
     description "A reference to a description of this device";

   leaf-list extensions {
     type string;
     description "A list of extension names that are used in this MUD
                  file.  Each name is registered with the IANA and
                  described in an RFC.";

  augment "/acl:access-lists/acl:acl"

 grouping ACCESS_LISTS {
   description "add inbound or outbound.  Normally "A grouping for access lists
                 are applied in an inbound the context of device
   container access-lists {
     description "The access lists that should be applied to traffic
                    to or outbound direction
                 separately from their definition.  This 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 not
                 possible with MUD."; identified by name and
       leaf packet-direction acl-name {
         type direction; leafref {
           path "/acl:access-lists/acl:acl/acl:acl-name";
         description "The name of the ACL for this entry.";
       leaf acl-type {
         type identityref {
           base acl:acl-base;
         description "The type of the ACL for this entry.";

 container device {
   description "A container allowing us to associate data with the
                device type being described in the instance document";

   container from-device-policy {
     description "inbound "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 outbound ACL.";
     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
     uses ACCESS_LISTS;



 augment "/acl:access-lists/acl:acl/" +
    "acl:access-list-entries/acl:ace/" +
    "acl:matches" {
   description "adding abstractions to avoid need of IP addresses";

   container mud-acl {
     if-feature mud-acl;
     must "../../../../acl-type = 'ietf-mud:mud-acl'";

       "TODO; improve. MUD-specific matches.";

     leaf manufacturer {
       type inet:host;
       description "authority component of the manufacturer URI";

     leaf same-manufacturer {
       type empty;
       description "expand to ACEs for each device
                  with the same origin";

     leaf model {
       type string;
       description "specific model (including version) for a
                    given manufacturer";

     leaf local-networks {
       type empty;
       description "this string is used to indicate networks
                  considered local in a given environment.";

     leaf controller {
       type inet:uri;
       description "expands to one or more controllers for a
                  given service that is codified by inet:uri.";

     leaf my-controller {
       type empty;
       description "This element indicates that the network should manage
                  a class of devices related to this MUD-URL that are
                  intended to control this device.";


 augment "/acl:access-lists/acl:acl/" +
   "acl:access-list-entries/acl:ace/" +
   "acl:matches/acl:tcp-acl" {
   description "Adding domain names to matching";
   leaf direction-initiated {
     type direction;
     description "which direction a flow was initiated";

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" element.
   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:

   module: ietf-acldns
     augment /acl:access-lists/acl:acl/acl:access-list-entries
         /acl:ace/acl:matches/acl:ace-type/acl:ace-ip: \
       +--rw src-dnsname?   inet:host
       +--rw dst-dnsname?   inet:host
     augment /acl:access-lists/acl:acl/acl:access-list-entries \
       +--rw src-dnsname?   inet:host
       +--rw dst-dnsname?   inet:host

   The choice of this these particular point points in the access-list model is
   based on the assumption that we are in some way referring to IP-related 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 autjors the ability
   to control the IP version that the device may utilize.

   The following elements are defined.

7.1.  source-dnsname

   The argument corresponds to a domain name of a source as specified by
   inet:host.  Depending on how the model is used, it may or may not be
   resolved, as required by the implementation and circumstances.

7.2.  destination-dnsname

   The argument corresponds to a domain name of a destination as
   specified by inet:host.  Depending on how the model is used, it may
   or may not be resolved, as required by the implementation and

7.3.  The ietf-acldns Model

   <CODE BEGINS>file "ietf-acldns@2016-07-20.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";

       "IETF OPSAWG (Ops Area) Working Group";

          "WG Web:
          WG List:
          Author: Eliot Lear

          Author: Ralph Droms

          Author: Dan Romascanu


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

     revision "2017-07-03" {
       description "Clone across IP ACL types.";
       reference "RFC XXXX: Manufacturer Usage Description

     revision "2016-07-20" {
       description "Base version of dnsname extension of ACL model";
       reference "RFC XXXX: Manufacturer Usage Description

     augment "/acl:access-lists/acl:acl/" +
        "acl:access-list-entries/acl:ace/" +

     grouping DNS_MATCHES {
       description "adding domain "Domain names to matching"; 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:access-list-entries/acl:ace/" +
        "acl:matches/acl:ipv4-acl" {
       description "Adding domain names to matching";
       uses DNS_MATCHES;

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

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.

   TODO: this needs to be revised.

      "ietf-mud:metainfo": {
         "last-update": "2016-05-18T20:00:50Z",
         "cache-validity": 168
      "ietf-access-control-list:access-lists":  {
        "acl": [ {
         "acl-name": "inbound-stuff",
         "acl-type" : "ipv4-acl",
         "ietf-mud:packet-direction" : "to-device",
         "access-list-entries": {
            "ace": [
                  "rule-name": "access-cloud",
                  "matches": {
                     "protocol" : 6,
                     "source-port-range" : {
                        "lower-port" : 443,
                        "upper-port" : 443
                  "actions" : {
                    "permit" : [null]
         "acl-name": "outbound-stuff",
         "acl-type" : "ipv4-acl",
         "ietf-mud:packet-direction" : "from-device",
         "access-list-entries": {
            "ace": [
                  "rule-name": "access-cloud",
                  "matches": {
                      "protocol" : 6,
                      "destination-port-range" : {
                        "lower-port" : 443,
                        "upper-port" : 443
                  "actions" : {
                      "permit" : [null]

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 device 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
   option is simply to identify the type of device to the network in a
   structured way such that the policy can be easily found with existing

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 to a network management system (such as
   the giaddr), or it will retrieve the usage description 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).

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 Identifier (URI) that points to an
   on-line Manufacturer Usage Description concerning the certificate
   subject.  URI must be represented as described in Section 7.4 of

   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 URI are defined Section 5 of this document.

   The choice of id-pe is based on guidance found in Section 4.2.2 of

         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:


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


     -- EXPORTS ALL --

       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) }

       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, ... }
       IDENTIFIED BY id-pe-mud-url }

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

       MUDURLSyntax ::= IA5String



   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 device to its MUD-URL.

11.  The Manufacturer Usage Description LLDP extension

   The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one hop
   vendor-neutral link layer protocols used by end hosts network devices
   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
   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)


   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 device
   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 device to the network in
   a structured way such that the policy can be easily found with
   existing toolsets.

   Hosts, routers, or other network devices 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 devices 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 device and response sent by another
   device.  The other devices do not acknowledge LLDP information
   received from a device. No specific network behavior is guaranteed.
   When a device consumes this extension, it may either forward the URL
   and relevant remote device information to a MUD controller, or it
   will retrieve the usage description by resolving the URL.

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 "
   modela", the MUD signature URL will be "

   Upon retrieving a MUD file, a MUD controller MUST validate the
   signature of the file before continuing with further processing.  A
   MUD controller SHOULD produce an error and it MUST cease all
   processing of that file if the signature cannot be validated.  It is
   important that MUD controllers have some reason to trust the
   certificates they are seeing.  Therefore, it is RECOMMENDED that new
   signers be validated either directly by an administrator or by a
   service that has some reason to believe that the signer is a good

   For 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

   2.  At a finer grain, only extensions that would not incur additional
       risk to the device are permitted.  Specifically, augmenting of
       the metainfo container is permitted with the understanding that
       such additions may be ignored.  In addition, augmentation of the
       ACL model is permitted so long as it remains safe for a given ACE
       to be ignored by the MUD Controller or the network elements it
       configures.  Most specifically, is is not permitted to include as
       an augmentation that modifies "deny" behavior without bumping the
       version.  Furthermore, implementations that are not able to parse
       a component of the ACE array MUST ignore the entire array entry
       (e.g., not the entire array) and MAY ignore the entire MUD file.

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
   device from other devices 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 devices that are able to communicate
   without protection.

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

15.  Security Considerations

   Based on how a MUD-URL is emitted, a device 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 devices that make use of certificate-based
   authentication such as IEEE 802.1AR certificates.  When those
   certificates are not present, devices 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 devices of a particular type.  Similarly, network
   management systems may be able to fingerprint the device.  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 device with the same MAC address that has indicated a change of
   authority without some additional validation (such as review of the
   class).  New devices 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 device 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 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
   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
   device that was produced long ago and only recently fielded, or the
   case where a new MUD controller has been installed.

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

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

   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 device might otherwise be
   identified, perhaps through how it behaves when it is connected to
   the network, whether a device 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 devices may also assist in
   limiting access to the MUD-URL through the use of mechanisms such as
   DHCPv6-Shield [RFC7610].

   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
   device 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.

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 (

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

   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:

    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
    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 <>, Ralph Droms <>
    o Intended usage: COMMON
    o Restrictions on usage: none
    o Author:
         Eliot Lear <>
         Ralph Droms <>
    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 >

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].

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, and Dan Wing 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 archictecture and the YANG model.  The remaining errors
   in this work are entirely the responsibility of the author.

18.  References

18.1.  Normative References

              Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
              S., and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-06 (work in progress), March May 2017.

              Bogdanovic, D., Koushik, K., Jethanandani, M., Huang, L., Agarwal, S.,
              and D. Blair, "Network Access Control List (ACL) YANG Data
              draft-ietf-netmod-acl-model-10 draft-ietf-netmod-acl-model-11 (work in progress), March
              June 2017.

              Bierman, A., "Guidelines for Authors and Reviewers of YANG
              Data Model Documents", draft-ietf-netmod-rfc6087bis-12 draft-ietf-netmod-rfc6087bis-13
              (work in progress), March June 2017.

              Institute for Electrical and Electronics Engineers, "IEEE
              Standard for Local and Metropolitan Area Networks--
              Station and Media Access Control Connectivity Discovery",

   [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, RFC 1123,
              DOI 10.17487/RFC1123, October 1989,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,

   [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, <>.

   [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,

   [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,

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
              January 2005, <>.

   [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,

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,

   [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,

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,

   [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,

   [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,

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,

   [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,

   [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,

18.2.  Informative References

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

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

              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,

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,

   [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, <>.

   [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, <>.

   [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, <>.

   [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,

   [RFC7452]  Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
              "Architectural Considerations in Smart Object Networking",
              RFC 7452, DOI 10.17487/RFC7452, March 2015,

   [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,

Appendix A.  Changes from Earlier Versions

   RFC Editor to remove this section prior to publication.

   Draft -06 to -07:

   o  Update models to match new ACL model

   o  extract directionality from the ACL, introducing a new device

   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)

   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 informaitonal element in.  * add urn registry
   and create first entry * add default elements

Appendix B.  Default MUD elements

   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.

   A complete MUD entry is included below.

     "ietf-mud:metainfo": {
       "last-update": "2016-09-27T15:10:24+02:00",
       "cache-validity": 168
     "acl:access-lists": {
       "access-list": [
           "acl-name": "mud-53134-v4in",
           "acl-type": "ipv4-acl",
           "ietf-mud:packet-direction": "to-device",
           "access-list-entries": {
             "ace": [
                 "rule-name": "entout0-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout1-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 6,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout2-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:ntp",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 123,
                     "upper-port": 123
                 "actions": {
                   "permit": [
           "acl-name": "mud-53134-v4out",
           "acl-type": "ipv4-acl",
           "ietf-mud:packet-direction": "from-device",
           "access-list-entries": {
             "ace": [
                 "rule-name": "entout0-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout1-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 6,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout2-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:ntp",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 123,
                     "upper-port": 123
                 "actions": {
                   "permit": [
           "acl-name": "mud-53134-v6in",
           "acl-type": "ipv6-acl",
           "ietf-mud:packet-direction": "to-device",
           "access-list-entries": {
             "ace": [
                 "rule-name": "entout0-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout1-in",
                 "matches": {
                   "ietf-mud:controller": "urn:params:mud:dns",
                   "protocol": 6,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout2-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:ntp",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 123,
                     "upper-port": 123
                 "actions": {
                   "permit": [
           "acl-name": "mud-53134-v6out",
           "acl-type": "ipv6-acl",
           "ietf-mud:packet-direction": "from-device",
           "access-list-entries": {
             "ace": [
                 "rule-name": "entout0-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout1-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:dns",
                   "protocol": 6,
                   "source-port-range": {
                     "lower-port": 53,
                     "upper-port": 53
                 "actions": {
                   "permit": [
                 "rule-name": "entout2-in",
                 "matches": {
                   "ietf-mud:controller": "urn:ietf:params:mud:ntp",
                   "protocol": 17,
                   "source-port-range": {
                     "lower-port": 123,
                     "upper-port": 123
                 "actions": {
                   "permit": [

Authors' Addresses

   Eliot Lear
   Cisco Systems
   Richtistrasse 7
   Wallisellen  CH-8304

   Phone: +41 44 878 9200

   Ralph Droms

   Phone: +1 978 376 3731
   Dan Romascanu

   Phone: +972 54 5555347