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Versions: (draft-lear-ietf-pkix-mud-extension) 00 01 02 03 04 draft-ietf-opsawg-mud

Network Working Group                                            E. Lear
Internet-Draft                                                  R. Droms
Intended status: Standards Track                           Cisco Systems
Expires: February 2, 2017                                   D. Romascanu
                                                                   Avaya
                                                         August 01, 2016


              Manufacturer Usage Description Specification
                     draft-lear-ietf-netmod-mud-04

Abstract

   This memo specifies the necessary components to implement
   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 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 February 2, 2017.

Copyright Notice

   Copyright (c) 2016 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
   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



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  The MUD Model and Semantic Meaning  . . . . . . . . . . . . .   4
   3.  Element Definitions . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  last-update . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  previous-mud-file . . . . . . . . . . . . . . . . . . . .   5
     3.3.  cache-validity  . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  masa-server . . . . . . . . . . . . . . . . . . . . . . .   6
     3.5.  is-supported  . . . . . . . . . . . . . . . . . . . . . .   6
     3.6.  packet-direction  . . . . . . . . . . . . . . . . . . . .   6
     3.7.  manufacturer  . . . . . . . . . . . . . . . . . . . . . .   6
     3.8.  same-manufacturer . . . . . . . . . . . . . . . . . . . .   6
     3.9.  model . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.10. local-networks  . . . . . . . . . . . . . . . . . . . . .   6
     3.11. controller  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.12. direction-initiated . . . . . . . . . . . . . . . . . . .   7
   4.  Processing of the MUD file  . . . . . . . . . . . . . . . . .   7
   5.  What does a MUD URL look like?  . . . . . . . . . . . . . . .   7
   6.  The MUD YANG Model  . . . . . . . . . . . . . . . . . . . . .   8
   7.  The Domain Name Extension to the ACL Model  . . . . . . . . .  11
     7.1.  source-dnsname  . . . . . . . . . . . . . . . . . . . . .  12
     7.2.  destination-dnsname . . . . . . . . . . . . . . . . . . .  12
     7.3.  The ietf-acldns Model . . . . . . . . . . . . . . . . . .  12
   8.  MUD File Example  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  The MUD URL DHCP Option . . . . . . . . . . . . . . . . . . .  15
     9.1.  Client Behavior . . . . . . . . . . . . . . . . . . . . .  15
     9.2.  Server Behavior . . . . . . . . . . . . . . . . . . . . .  16
     9.3.  Relay Requirements  . . . . . . . . . . . . . . . . . . .  16
   10. The Manufacturer Usage Description (MUD) URL X.509 Extension   16
   11. The Manufacturer Usage Description LLDP extension . . . . . .  17
   12. Creating and Processing of Signed MUD Files . . . . . . . . .  18
     12.1.  Creating a MUD file signature  . . . . . . . . . . . . .  18
     12.2.  Verifying a MUD file signature . . . . . . . . . . . . .  19
   13. Extensibility . . . . . . . . . . . . . . . . . . . . . . . .  19
   14. Security Considerations . . . . . . . . . . . . . . . . . . .  20
   15. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
     15.1.  DHCPv4 and DHCPv6 Options  . . . . . . . . . . . . . . .  21
     15.2.  PKIX Extensions  . . . . . . . . . . . . . . . . . . . .  21
     15.3.  Well Known URI Suffix  . . . . . . . . . . . . . . . . .  21
     15.4.  MIME Media-type Registration for MUD files . . . . . . .  21
     15.5.  LLDP IANA TLV Subtype Registry . . . . . . . . . . . . .  22
   16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  23
   17. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23



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     17.1.  Normative References . . . . . . . . . . . . . . . . . .  23
     17.2.  Informative References . . . . . . . . . . . . . . . . .  24
   Appendix A.  Changes from Earlier Versions  . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  26

1.  Introduction

   Manufacturer Usage Descriptions (MUDs) provide advice to end networks
   on how to treat specific classes of devices.  The MUD architecture is
   explained in [I-D.lear-mud-framework].  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.

   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 second 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.

   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.  Finally, an LLDP frame is defined.

   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.

   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
   limited subset of NETCONF-like content is permitted.



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1.1.  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.

   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].

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 13, 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.  The first container
   holds information that is relevant to retrieval and validity of the
   MUD file itself.  The second container augments the access list to
   indicate direction the ACL is to be applied.  The final 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.







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     module: ietf-mud
       +--rw meta-information
           +--rw last-update?         yang:date-and-time
           +--rw previous-mud-file?   yang:uri
           +--rw cache-validity?      uint32
           +--rw masa-server?         inet:uri
           +--rw is-supported?        boolean
     augment /acl:access-lists/acl:acl:
        +--rw packet-direction?   direction
     augment /acl:access-lists/acl:acl
             /acl:access-list-entries/acl:ace/acl:matches:
        +--rw manufacturer?          inet:host
        +--rw same-manufacturer?     empty
        +--rw model?                 string
        +--rw local-networks?        empty
        +--rw controller?            inet:uri
        +--rw direction-initiated?   direction

3.  Element Definitions

   The following elements are defined.

3.1.  last-update

   This is a date-and-time value of the last time the MUD file was
   updated.  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.  previous-mud-file

   This is a URL that should point to the previous MUD URL for auditing
   purposes.  Because it should not be necessary to resign a MUD file
   when a new one is released, the archival location of a current MUD
   file should be identified prior to its release.  Note the signature
   file MUST also be available.  For example, if previous-mud-file is
   set to "https://example.com/.mud/v1/xxx", the corresponding signature
   would be found at "https://example.com/.mud/v1/xxx.p7s".

3.3.  cache-validity

   This uint32 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 no
   more than 1440 for any device that is supported.






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3.4.  masa-server

   This optional element refers to the URL that should be used to
   resolve the location any 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 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.

3.6.  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 communcation 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".

3.7.  manufacturer

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

3.8.  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.

3.9.  model

   This string matches the one and only segment following the authority
   section 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.

3.10.  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.



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3.11.  controller

   This URI specifies a value that a controller will register with the
   network management station.  The element then is expanded to the set
   of hosts that are so registered.

   In addition, some meta information is defined in order to determine
   when a usage description should be refreshed.

3.12.  direction-initiated

   When applied this matches packets when the flow was initiated in the
   corresponding direction.  [RFC6092] provides guidance for 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, DHCP, and NTP are, by default, permitted to and from
      the device.

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.



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   "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@2016-07-20.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
       WG Chair: Warren Kumari
       warren@kumari.net
       WG Chair: Zhou Tianran
       zhoutianran@huawei.com
       Editor: Eliot Lear
       lear@cisco.com
       Editor: Ralph Droms
       rdroms@cisco.com
    ";




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  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.

    Copyright (c) 2016 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
    (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 "2016-07-20"  {
    description "Base version of MUD extensions to ACL model";
    reference "RFC XXXX: Manufacturer Usage Description Specification";
  }

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

  container meta-information {

    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 the time and date that
                   the MUD file was generated.";
    }

    leaf previous-mud-file {
       type inet:uri;



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       description "Use to find the previous MUD file location
                    for auditing purposes.";
    }

    leaf cache-validity {
      type uint32;
      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.";
    }
  }

  augment "/acl:access-lists/acl:acl"   {
    description "add inbound or outbound.  Normally access lists
                 are applied in an inbound or outbound direction
                 separately from their definition.  This is not
                 possible with MUD.";
    leaf packet-direction
    {
      type direction;
      description "inbound or outbound ACL.";
    }
  }


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

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

    leaf same-manufacturer {



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      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 direction-initiated {
      type direction;
      description "which direction a flow was initiated";
    }
  }
}

<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" 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:

      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





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   The choice of this particular point 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 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
   circumstances.

7.3.  The ietf-acldns Model

 <CODE BEGINS>file "ietf-acldns@2007-07020.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";
   }

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

   contact
        "WG Web: http://tools.ietf.org/wg/opsawg/
        WG List: opsawg@ietf.org
        WG Chair: Warren Kumari
        warren@kumari.net
        WG Chair: Zhou Tianran
        zhoutianran@huawei.com
        Editor: Eliot Lear



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        lear@cisco.com
        Editor: Ralph Droms
        rdroms@cisco.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 "2016-07-20" {
     description "Base version of dnsname extension of ACL model";
     reference "RFC XXXX: Manufacturer Usage Description Specification";
   }

   augment "/acl:access-lists/acl:acl/" +
      "acl:access-list-entries/acl:ace/" +
      "acl:matches/acl:ace-type/acl:ace-ip" {
     description "adding domain names to 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";
     }
   }
 }

 <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:support-information": {
         "last-update": "2016-05-18T20:00:50Z",
         "cache-validity": 1440
         },
      "ietf-access-control-list:access-lists":  {
        "acl": [ {
         "acl-name": "inbound-stuff",
         "acl-type" : "ipv4-acl",



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         "ietf-mud:direction" : "to-device",
         "access-list-entries": {
            "ace": [
               {
                  "rule-name": "access-cloud",
                  "matches": {
                    "ietf-acldns:src-dnsname":
                        "lighting-system.example.com",
                     "protocol" : 6,
                     "source-port-range" : {
                        "lower-port" : 443,
                        "upper-port" : 443
                        }
                     },
                  "actions" : {
                    "permit" : [null]
                    }
                 }
               ]
              }
            },
            {
         "acl-name": "outbound-stuff",
         "acl-type" : "ipv4-acl",
         "ietf-mud:direction" : "from-device",
         "access-list-entries": {
            "ace": [
               {
                  "rule-name": "access-cloud",
                  "matches": {
                     "ietf-acldns:dst-dnsname":
                          "lighting-system.example.com",
                      "protocol" : 6,
                      "destination-port-range" : {
                        "lower-port" : 443,
                        "upper-port" : 443
                       }
                   },
                  "actions" : {
                      "permit" : [null]
                    }
                 }
               ]
              }
            }
           ]
       }
   }



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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 (TBD) is assigned by IANA.  len is a single
   octet that indicates the length of the URL in octets.  MUD URL is a
   URL.  The length of a MUD URL does not exceed 255 bytes.

   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 (TBD; assigned by IANA).

   option-length contains the length of the URL in octets.  The length
   MUST NOT exceed 255 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
   toolsets.

9.1.  Client Behavior

   A DHCP client MAY emit either a DHCPv4 or DHCPv6 option or both.
   These options 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.




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   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.  For purposes of debugging, if a server
   successfully parses the option and the URL, it MUST return the option
   with the same URL 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
   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 network management system MUST notify the network
   management 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

   [RFC7299] provides a procedure and means to specify extensions to
   X.509 certificates.  The MUD URL is a non-critical Certificate
   extension that points to an on-line Manufacturer Usage Description
   concerning the certificate subject.  This extension contains a single
   Uniform Resource Identifier (URI).  Internationalized Resource
   Identifiers must be represented as URI's in the way described in RFC
   5280, section 7.4.



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   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:

   - The MUD URI extension id-pe-mud-url OBJECT IDENTIFER ::= { id-pe
   TBD }

   The extension returns a single value:

   mudURLSyntax ::= IA5String - for use with MUD architecture.

   The semantics of the URI are defined Section 5.

11.  The Manufacturer Usage Description LLDP extension

   The IEEE802.1AB Link Layer Discovery Protocol (LLDP) [IEEE8021AB] 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)|(1-256 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




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

   o  MUD URL - the length MUST NOT exceed 256 octets (consistent with
      the DHCP option defined in Section 9)

   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 network management
   system, 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.  If the device that is being
   described supports IEEE 802.1AR, its manufacturer certificate and the
   certificate in the MUD file MUST share a common trust anchor in order
   to insure that manufacturer of the device is also the provider of the
   MUD file.  The signature is stored at the same location as the MUD



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   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 resigned 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 SHOULD produce an error and it MUST cease all
   processing of that file if the signature cannot be validated.  If the
   MUD controller has received the MUD URL via IEEE 802.1AR containing
   an IDevID (a manufacturer certificate), it MUST further confirm that
   the manufacturer certificate and that of the MUD file share a common
   trust anchor.

   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
       versions.



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   2.  At a finer grain, only extensions that would not incur additional
       risk to the device are permitted.  Specifically, augmenting of
       the meta-information 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.  Security Considerations

   Based on the means a URL is procured, 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.

   Network management systems SHOULD NOT deploy 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.  Second, it may 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 file



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   servers 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.

15.  IANA Considerations

15.1.  DHCPv4 and DHCPv6 Options

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

15.2.  PKIX Extensions

   The IANA is requested to assign a value for id-pe-mud-uri in the "SMI
   Security for PKIX Certificate Extension" Registry.  Its use is
   specified in Section 10.

15.3.  Well Known URI Suffix

   The IANA is requested to register the URL suffix of "mud" as follows:

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

15.4.  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.


15.5.  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

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

   Reference = < this document >







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16.  Acknowledgments

   The authors would like to thank Einar Nilsen-Nygaard, 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.  The remaining errors in this work are entirely the
   responsibility of the author.

17.  References

17.1.  Normative References

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., and S.
              Bjarnason, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-03 (work in progress), June 2016.

   [I-D.ietf-netmod-acl-model]
              Bogdanovic, D., Koushik, K., Huang, L., and D. Blair,
              "Network Access Control List (ACL) YANG Data Model",
              draft-ietf-netmod-acl-model-08 (work in progress), July
              2016.

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

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

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

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,
              <http://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, <http://www.rfc-editor.org/info/rfc3315>.




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   [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,
              <http://www.rfc-editor.org/info/rfc3986>.

   [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,
              <http://www.rfc-editor.org/info/rfc5280>.

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

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

   [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,
              <http://www.rfc-editor.org/info/rfc6092>.

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

   [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,
              <http://www.rfc-editor.org/info/rfc7227>.

   [RFC7299]  Housley, R., "Object Identifier Registry for the PKIX
              Working Group", RFC 7299, DOI 10.17487/RFC7299, July 2014,
              <http://www.rfc-editor.org/info/rfc7299>.

17.2.  Informative References

   [I-D.lear-mud-framework]
              Lear, E., "Manufacturer Usage Description Framework",
              draft-lear-mud-framework-00 (work in progress), January
              2016.






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   [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.

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

   [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, <http://www.rfc-editor.org/info/rfc7042>.

Appendix A.  Changes from Earlier Versions

   RFC Editor to remove this section prior to publication.

   Draft -03 to -04: * add LLDP extension.  * add Dan Romascanu as co-
   author.

   Draft -02 to -03: * incorporate domain name model.  * discuss
   extensibility.  * leave placeholder for LLDP TLV.

   Draft -01 to -02:

   o  XML->JSON

   o  Remove device versioning information from URL

   o  Add PKIX and DHCP options

   o  Add Content-type information

   o  Clean up IANA considerations to match registration templates

   o  Ralph Droms carried over as author from DHCP option.

   o  Signing information

   o  Expanded Security Considerations

   o  Add directionality for both packets and flows.



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   o  add previous-mud-file

   Draft -00 to -01:

   o  Add MASA server element

Authors' Addresses

   Eliot Lear
   Cisco Systems
   Richtistrasse 7
   Wallisellen  CH-8304
   Switzerland

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


   Ralph Droms
   Cisco Systems
   55 Cambridge Parkway
   Cambridge  1057
   United States

   Phone: +1 617 621 1904
   Email: rdroms@cisco.com


   Dan Romascanu
   Avaya
   26, HaRokhmim Str., Bldg. D
   Holon  5885849
   Israel

   Phone: +972-3-645-8414
   Email: dromasca@avaya.com















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