Internet Engineering Task Force (IETF)                           E. Lear
Request for Comments: 9472                                 Cisco Systems
Category: Standards Track                                        S. Rose
ISSN: 2070-1721                                                     NIST
                                                           October 2023


A YANG Data Model for Reporting Software Bills of Materials (SBOMs) and
                      Vulnerability Information

Abstract

  To improve cybersecurity posture, automation is necessary to locate
  the software a device is using, whether that software has known
  vulnerabilities, and what, if any, recommendations suppliers may
  have.  This memo extends the Manufacturer User Description (MUD) YANG
  schema to provide the locations of software bills of materials
  (SBOMs) and vulnerability information by introducing a transparency
  schema.

Status of This Memo

  This is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc9472.

Copyright Notice

  Copyright (c) 2023 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
  (https://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 Revised BSD License text as described in Section 4.e of the
  Trust Legal Provisions and are provided without warranty as described
  in the Revised BSD License.

Table of Contents

  1.  Introduction
    1.1.  Requirements Language
    1.2.  How This Information Is Retrieved
    1.3.  Formats
  2.  The Well-Known Transparency Endpoint Set
  3.  The mud-transparency Extension
  4.  The mud-sbom Augmentation to the MUD YANG Data Model
  5.  Examples
    5.1.  Without ACLS
    5.2.  SBOM Located on the Device
    5.3.  Further Contact Required
    5.4.  With ACLS
  6.  Security Considerations
  7.  IANA Considerations
    7.1.  MUD Extension
    7.2.  YANG Registration
    7.3.  Well-Known Prefix
  8.  References
    8.1.  Normative References
    8.2.  Informative References
  Acknowledgments
  Authors' Addresses

1.  Introduction

  A number of activities have taken place to improve the visibility of
  what software is running on a system and what vulnerabilities that
  software may have [EO2021].

  Put simply, this memo seeks to answer two classes of questions for
  tens of thousands of devices and a large variety of device types.
  Those questions are as follows:

  *  Is this system susceptible to a particular vulnerability?

  *  Which devices in a particular environment contain vulnerabilities
     that require some action?

  This memo doesn't specify the format of this information but rather
  only how to locate and retrieve these objects.  That is, the model is
  intended to facilitate discovery and on its own provides no access to
  the underlying data.

  Software bills of materials (SBOMs) are descriptions of what
  software, including versioning and dependencies, a device contains.
  There are different SBOM formats such as Software Package Data
  Exchange [SPDX] or CycloneDX [CycloneDX15].

  System vulnerabilities may be similarly described using several data
  formats, including the aforementioned CycloneDX, the Common
  Vulnerability Reporting Framework [CVRF], and the Common Security
  Advisory Format [CSAF].  This information is typically used to report
  the state of any known vulnerabilities on a system to administrators.

  SBOM and vulnerability information can be used in concert with other
  sources of vulnerability information.  A network management tool
  could discover that a system uses a particular set of software
  components, searches a national vulnerability database to determine
  known vulnerabilities, and applies information provided by the
  manufacturer through this mechanism to produce a vulnerability
  report.  That report may be used to indicate what, if any, versions
  of software correct that vulnerability or whether the system
  exercises the vulnerable code at all.

  Both classes of information elements are optional under the model
  specified in this memo.  One can provide only an SBOM, only
  vulnerability information, or both an SBOM and vulnerability
  information.

  Note that SBOM formats may also carry other information, the most
  common being any licensing terms.  Because this specification is
  neutral regarding content, it is left for format developers such as
  the Linux Foundation, OASIS, and ISO to decide what attributes they
  will support.

  This memo does not specify how vulnerability information may be
  retrieved directly from the endpoint.  That is because vulnerability
  information changes occur to software updates at different rates.
  However, some SBOM formats may also contain vulnerability
  information.

  SBOMs and vulnerability information are advertised and retrieved
  through the use of a YANG augmentation of the Manufacturer User
  Description (MUD) model [RFC8520].  Note that the schema creates a
  grouping that can also be used independently of MUD.  Moreover, other
  MUD features, such as access controls, needn't be present.

  The mechanisms specified in this document are meant to address two
  use cases:

  *  A network-layer management system retrieving information from an
     Internet of Things (IoT) device as part of its ongoing life cycle.
     Such devices may or may not have query interfaces available.

  *  An application-layer management system retrieving vulnerability or
     SBOM information in order to evaluate the posture of an
     application server of some form.  These application servers may
     themselves be containers or hypervisors.  Discovery of the
     topology of a server is beyond the scope of this memo.

  To satisfy these two key use cases, objects may be found in one of
  three methods:

  1.  on the devices themselves

  2.  on a website (e.g., via a URI)

  3.  through some form of out-of-band contact with the supplier

  Using the first method, devices will have interfaces that permit
  direct retrieval.  Examples of these interfaces might be an HTTP
  [RFC9110] or Constrained Application Protocol (CoAP) [RFC7252]
  endpoint for retrieval.  There may also be private interfaces as
  well.

  Using the second method, when a device does not have an appropriate
  retrieval interface, but one is directly available from the
  manufacturer, a URI to that information is discovered through
  interfaces such as MUD via DHCP or bootstrapping and ownership
  transfer mechanisms.

  Using the third method, a supplier may wish to make an SBOM or
  vulnerability information available under certain circumstances and
  may need to individually evaluate requests.  The result of that
  evaluation might be the SBOM, the vulnerability itself, a restricted
  URL, or no access.

  To enable application-layer discovery, this memo defines a well-known
  URI [RFC8615].  Management or orchestration tools can query this
  well-known URI to retrieve a system's SBOM information.  Further
  queries may be necessary based on the content and structure of the
  response.

1.1.  Requirements Language

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
  "OPTIONAL" in this document are to be interpreted as described in
  BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
  capitals, as shown here.

1.2.  How This Information Is Retrieved

  Section 4 describes a data model to extend the MUD file format to
  carry SBOM and vulnerability information.  Section 1.5 of [RFC8520]
  describes mechanisms by which devices can emit a URL to point to this
  file.  Additionally, devices can share this URL either through
  documentation or within a QR code on a box.  Section 2 describes a
  well-known URL from which an SBOM could be served from the local
  device.

  Note that vulnerability and SBOM information are likely to change at
  different rates.  MUD's cache-validity node provides a way for
  manufacturers to control how often tooling should check for those
  changes through the cache-validity node.

1.3.  Formats

  There are multiple ways to express both SBOMs and vulnerability
  information.  When these are retrieved either from the device or from
  a remote web server, tools will need to observe the Content-Type
  header to determine precisely which format is being transmitted.
  Because IoT devices in particular have limited capabilities, use of a
  specific Accept: header in HTTP or the Accept Option in CoAP is NOT
  RECOMMENDED.  Instead, backend tooling is encouraged to support all
  known formats and SHOULD silently discard SBOM information sent with
  a media type that is not understood.

  If multiple SBOMs are intended to be supported in the same file, the
  media type should properly reflect that.  For example, one might make
  use of application/{someformat}+json-seq.  It is left to those
  supporting those formats to make the appropriate registrations in
  this case.

  Some formats may support both vulnerability and software inventory
  information.  When both vulnerability and software inventory
  information is available from the same URL, both sbom-url and members
  of the vuln-url list MUST indicate that.  Network management systems
  MUST take note of when the SBOM and vulnerability information are
  accessible via the same resource and not retrieve the resource a
  second time.

2.  The Well-Known Transparency Endpoint Set

  A well-known endpoint is defined:

     "/.well-known/sbom" retrieves an SBOM

  As discussed previously, the precise format of a response is based on
  the Content-Type provided.

3.  The mud-transparency Extension

  We now formally define the mud-transparency extension; this is done
  in two parts.

  First, the extension name "transparency" is listed in the
  "extensions" array of the MUD file.  Note that this schema extension
  is intended to be used wherever it might be appropriate (e.g., not
  just with MUD).

  Second, the "mud" container is augmented with a list of SBOM sources.

  This is done as follows:

  module: ietf-mud-transparency

    augment /mud:mud:
      +--rw transparency
         +--rw (sbom-retrieval-method)?
         |  +--:(cloud)
         |  |  +--rw sboms* [version-info]
         |  |     +--rw version-info    string
         |  |     +--rw sbom-url?       inet:uri
         |  +--:(local-well-known)
         |  |  +--rw sbom-local-well-known?   identityref
         |  +--:(sbom-contact-info)
         |     +--rw sbom-contact-uri?        inet:uri
         +--rw sbom-archive-list?             inet:uri
         +--rw (vuln-retrieval-method)?
            +--:(cloud)
            |  +--rw vuln-url*                inet:uri
            +--:(vuln-contact-info)
               +--rw vuln-contact-uri?        inet:uri

  See [RFC8340] for a description of YANG trees.

4.  The mud-sbom Augmentation to the MUD YANG Data Model

  This YANG module references [RFC6991], [RFC7231], [RFC7252],
  [RFC8520], and [RFC9110].

  <CODE BEGINS> file "[email protected]"
  module ietf-mud-transparency {
    yang-version 1.1;
    namespace "urn:ietf:params:xml:ns:yang:ietf-mud-transparency";
    prefix mudtx;

    import ietf-inet-types {
      prefix inet;
      reference
        "RFC 6991: Common YANG Data Types";
    }
    import ietf-mud {
      prefix mud;
      reference
        "RFC 8520: Manufacturer Usage Description Specification";
    }

    organization
      "IETF OPSAWG (Ops Area) Working Group";
    contact
      "WG Web: <https://datatracker.ietf.org/wg/opsawg/>
       WG List: <[email protected]>

       Editor: Eliot Lear <[email protected]>
       Editor: Scott Rose <[email protected]>";
    description
      "This YANG module augments the ietf-mud model to provide for
       reporting of SBOMs and vulnerability information.

       The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
       NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
       'MAY', and 'OPTIONAL' in this document are to be interpreted as
       described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
       they appear in all capitals, as shown here.

       Copyright (c) 2023 IETF Trust and the persons identified as
       authors of the code.  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 Revised BSD License set
       forth in Section 4.c of the IETF Trust's Legal Provisions
       Relating to IETF Documents
       (https://trustee.ietf.org/license-info).

       This version of this YANG module is part of RFC 9472
       (https://www.rfc-editor.org/info/rfc9472);
       see the RFC itself for full legal notices.";

    revision 2023-10-10 {
      description
        "Initial proposed standard.";
      reference
        "RFC 9472: A YANG Data Model for Reporting Software Bills
         of Materials (SBOMs) and Vulnerability Information";
    }

    identity local-type {
      description
        "Base identity for local well-known choices.";
    }

    identity http {
      base mudtx:local-type;
      description
        "Use http (RFC 7231) (insecure) to retrieve SBOM information.
          This method is NOT RECOMMENDED but may be unavoidable for
          certain classes of deployment where TLS has not or
          cannot be implemented.";
        reference
          "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1):
           Semantics and Content";
    }

    identity https {
      base mudtx:local-type;
      description
        "Use https (secure) to retrieve SBOM information.  See
         RFC 9110.";
        reference
          "RFC 9110: HTTP Semantics";
    }

    identity coap {
      base mudtx:local-type;
      description
        "Use COAP (RFC 7252) (insecure) to retrieve SBOM.  This method
         is NOT RECOMMENDED, although it may be unavoidable
         for certain classes of implementations/deployments.";
        reference
          "RFC 7252: The Constrained Application Protocol (CoAP)";
    }

    identity coaps {
      base mudtx:local-type;
      description
        "Use COAPS (secure) to retrieve SBOM (RFC 7252).";
    }

    grouping transparency-extension {
      description
        "This grouping provides a means to describe the location of
         software bills of material and vulnerability descriptions.";
      container transparency {
        description
          "Container of methods to get SBOMs and vulnerability
           information.";
        choice sbom-retrieval-method {
          description
            "How to find SBOM information.";
          case cloud {
            list sboms {
              key "version-info";
              description
                "A list of SBOMs tied to different software
                 or hardware versions.";
              leaf version-info {
                type string;
                description
                  "The version to which this SBOM refers.";
              }
              leaf sbom-url {
                type inet:uri {
                  pattern '((coaps?)|(https?)):.*';
                }
                description
                  "A statically located URL.";
              }
            }
          }
          case local-well-known {
            leaf sbom-local-well-known {
              type identityref {
                base mudtx:local-type;
              }
              description
                "Which communication protocol to choose.";
            }
          }
          case sbom-contact-info {
            leaf sbom-contact-uri {
              type inet:uri {
                pattern '((mailto)|(https?)|(tel)):.*';
              }
              description
                "This MUST be a tel, an http, an https, or
                 a mailto uri schema that customers can use to
                 contact someone for SBOM information.";
            }
          }
        }
        leaf sbom-archive-list {
          type inet:uri;
          description
            "This URI returns a JSON list of URLs that consist of
             SBOMs that were previously published for this
             device.  Publication dates can be found inside
             the SBOMs.";
        }
        choice vuln-retrieval-method {
          description
            "How to find vulnerability information.";
          case cloud {
            leaf-list vuln-url {
              type inet:uri;
              description
                "List of statically located URLs that reference
                 vulnerability information.";
            }
          }
          case vuln-contact-info {
            leaf vuln-contact-uri {
              type inet:uri {
                pattern '((mailto)|(https?)|(tel)):.*';
              }
              description
                "This MUST be a tel, an http, an https, or
                 a mailto uri schema that customers can use to
                 contact someone for vulnerability information.";
            }
          }
        }
      }
    }

    augment "/mud:mud" {
      description
        "Add extension for software transparency.";
      uses transparency-extension;
    }
  }
  <CODE ENDS>

5.  Examples

  In this example MUD file that uses a cloud service, the modelX
  presents a location of the SBOM in a URL.  Note that the Access
  Control Lists (ACLs) in a MUD file are NOT required, although they
  are a very good idea for IP-based devices.

5.1.  Without ACLS

  This first MUD file demonstrates how to get SBOM and vulnerability
  information without ACLs.

  {
   "ietf-mud:mud": {
     "mud-version": 1,
     "extensions": [
       "transparency"
     ],
     "mudtx:transparency": {
       sboms: [ {
       "version-info": "1.2",
       "sbom-url": "https://iot.example.com/info/modelX/sbom.json"
       } ],
       "vuln-url" : [
         "https://iotd.example.com/info/modelX/csaf.json"
       ]
     },
     "mud-url": "https://iot.example.com/modelX.json",
     "mud-signature": "https://iot.example.com/modelX.p7s",
     "last-update": "2022-01-05T13:29:12+00:00",
     "cache-validity": 48,
     "is-supported": true,
     "systeminfo": "retrieving vuln and SBOM info via a cloud service",
     "mfg-name": "Example, Inc.",
     "documentation": "https://iot.example.com/doc/modelX",
     "model-name": "modelX"
   }
  }

  The second example demonstrates that just SBOM information is
  included from the cloud.

  {
   "ietf-mud:mud": {
     "mud-version": 1,
     "extensions": [
       "transparency"
     ],
     "mudtx:transparency": {
       sboms: [ {
       "version-info": "1.2",
       "sbom-url": "https://iot.example.com/info/modelX/sbom.json"
       } ],
     },
     "mud-url": "https://iot.example.com/modelX.json",
     "mud-signature": "https://iot.example.com/modelX.p7s",
     "last-update": "2022-01-05T13:29:12+00:00",
     "cache-validity": 48,
     "is-supported": true,
     "systeminfo": "retrieving vuln and SBOM info via a cloud service",
     "mfg-name": "Example, Inc.",
     "documentation": "https://iot.example.com/doc/modelX",
     "model-name": "modelX"
   }
  }

5.2.  SBOM Located on the Device

  In the next example, the SBOM is located on the device, and there is
  no vulnerability information provided.

  {
    "ietf-mud:mud": {
      "mud-version": 1,
      "extensions": [
        "transparency"
      ],
      "mudtx:transparency": {
        "sbom-local-well-known": "https"
      },
      "mud-url": "https://iot.example.com/modelX.json",
      "mud-signature": "https://iot.example.com/modelX.p7s",
      "last-update": "2022-01-05T13:29:47+00:00",
      "cache-validity": 48,
      "is-supported": true,
      "systeminfo": "retrieving SBOM info from a local source",
      "mfg-name": "Example, Inc.",
      "documentation": "https://iot.example.com/doc/modelX",
      "model-name": "modelX"
    }
  }

  In this example, the SBOM is retrieved from the device, while
  vulnerability information is available from the cloud.  This is
  likely a common case because vendors may learn of vulnerability
  information more frequently than they update software.

  {
   "ietf-mud:mud": {
     "mud-version": 1,
     "extensions": [
       "transparency"
     ],
     "mudtx:transparency": {
       "sbom-local-well-known": "https",
       "vuln-url" : [
         "https://iotd.example.com/info/modelX/csaf.json"
       ]
     },
     "mud-url": "https://iot-device.example.com/modelX.json",
     "mud-signature": "https://iot-device.example.com/modelX.p7s",
     "last-update": "2022-01-05T13:25:14+00:00",
     "cache-validity": 48,
     "is-supported": true,
     "systeminfo": "mixed example: SBOM on device, vuln info in cloud",
     "mfg-name": "Example, Inc.",
     "documentation": "https://iot-device.example.com/doc/modelX",
     "model-name": "modelX"
   }
  }

5.3.  Further Contact Required

  In this example, the network manager must take further steps to
  retrieve SBOM information.  Vulnerability information is still
  available.

  {
  "ietf-mud:mud": {
  "mud-version": 1,
  "extensions": [
    "transparency"
  ],
  "mudtx:transparency": {
    "contact-info": "https://iot-device.example.com/contact-info.html",
      "vuln-url" : [
        "https://iotd.example.com/info/modelX/csaf.json"
      ]
  },
  "mud-url": "https://iot-device.example.com/modelX.json",
  "mud-signature": "https://iot-device.example.com/modelX.p7s",
  "last-update": "2021-07-09T06:16:42+00:00",
  "cache-validity": 48,
  "is-supported": true,
  "systeminfo": "retrieving vuln and SBOM info via a cloud service",
  "mfg-name": "Example, Inc.",
  "documentation": "https://iot-device.example.com/doc/modelX",
  "model-name": "modelX"
  }
  }

5.4.  With ACLS

  Finally, here is a complete example where the device provides SBOM
  and vulnerability information as well as access control information.

  {
   "ietf-mud:mud": {
     "mud-version": 1,
     "extensions": [
       "transparency"
     ],
     "mudtx:transparency": {
       "sbom-local-well-known": "https",
       "vuln-url" : [
         "https://iotd.example.com/info/modelX/csaf.json"
       ]
     },
     "mud-url": "https://iot.example.com/modelX.json",
     "mud-signature": "https://iot.example.com/modelX.p7s",
     "last-update": "2022-01-05T13:30:31+00:00",
     "cache-validity": 48,
     "is-supported": true,
     "systeminfo": "retrieving vuln and SBOM info via a cloud service",
     "mfg-name": "Example, Inc.",
     "documentation": "https://iot.example.com/doc/modelX",
     "model-name": "modelX",
     "from-device-policy": {
       "access-lists": {
         "access-list": [
           {
             "name": "mud-65443-v4fr"
           }
         ]
       }
     },
     "to-device-policy": {
       "access-lists": {
         "access-list": [
           {
             "name": "mud-65443-v4to"
           }
         ]
       }
     }
   },
   "ietf-access-control-list:acls": {
     "acl": [
       {
         "name": "mud-65443-v4to",
         "type": "ipv4-acl-type",
         "aces": {
           "ace": [
             {
               "name": "cl0-todev",
               "matches": {
                 "ipv4": {
                   "ietf-acldns:src-dnsname": "iotserver.example.com"
                 }
               },
               "actions": {
                 "forwarding": "accept"
               }
             }
           ]
         }
       },
       {
         "name": "mud-65443-v4fr",
         "type": "ipv4-acl-type",
         "aces": {
           "ace": [
             {
               "name": "cl0-frdev",
               "matches": {
                 "ipv4": {
                   "ietf-acldns:dst-dnsname": "iotserver.example.com"
                 }
               },
               "actions": {
                 "forwarding": "accept"
               }
             }
           ]
         }
       }
     ]
   }
  }

  At this point, the management system can attempt to retrieve the
  SBOM, determine which format is in use through the Content-Type
  header on the response to a GET request, independently repeat the
  process for vulnerability information, and apply ACLs as appropriate.

6.  Security Considerations

  This document describes a schema for discovering the location of
  information relating to software transparency and does not specify
  the access model for the information itself.  In particular, the YANG
  module specified in this document is not necessarily intended to be
  accessed via regular network management protocols, such as NETCONF
  [RFC6241] or RESTCONF [RFC8040], and hence the regular security
  considerations for such usage are not considered here.

  Below, we describe protections relating to both discovery and some
  advice on protecting the underlying SBOM and vulnerability
  information.

  The model specifies both encrypted and unencrypted means to retrieve
  information.  This is a matter of pragmatism.  Unencrypted
  communications allow for manipulation of information being retrieved.
  Therefore, it is RECOMMENDED that implementations offer a means to
  configure endpoints so that they may make use of TLS or DTLS.

  The ietf-mud-transparency module has no operational impact on the
  element itself and is used to discover state information that may be
  available on or off the element.  In as much as the module itself is
  made writeable, this only indicates a change in how to retrieve read-
  only elements.  There are no means, for instance, to upload an SBOM.
  Additional risks are discussed below and are applicable to all nodes
  within the transparency container.

  If an attacker modifies the elements, they may misdirect automation
  to retrieve a different set of URLs than was intended by the
  designer.  This in turn leads to two specific sets of risks:

  *  the information retrieved would be false

  *  the URLs themselves point to malware

  To address either of these risks or any tampering of a URL:

  *  test any cloud-based URL against a reputation service

  *  provide the administrator an opportunity to approve further
     processing when the authority changes to one not known to be
     reputable

  SBOMs provide an inventory of software.  Knowledge of which specific
  software is loaded on a system can aid an attacker in identifying an
  appropriate exploit for a known vulnerability or guide the
  development of novel exploit against this system.  However, if
  software is available to an attacker, the attacker may already be
  able to derive this very same software inventory.  When this
  information resides on the endpoint itself, the endpoint SHOULD NOT
  provide unrestricted access to the well-known URL by default.

  Other servers that offer the data MAY restrict access to SBOM
  information using appropriate authorization semantics within HTTP.
  One way to do this would be to issue a certificate to the client for
  this purpose after a registration process has taken place.  Another
  approach would involve the use of OAuth in combination.  In
  particular, if a system attempts to retrieve an SBOM via HTTP or CoAP
  and the client is not authorized, the server MUST produce an
  appropriate error with instructions on how to register a particular
  client.

  Another risk is a skew in the SBOM listing and the actual software
  inventory of a device/container.  For example, a manufacturer may
  update the SBOM on its server, but an individual device has not been
  upgraded yet.  This may result in an incorrect policy being applied
  to a device.  A unique mapping of a device's software version and its
  SBOM can minimize this risk.

  To further mitigate attacks against a device, manufacturers SHOULD
  recommend network access controls.

  Vulnerability information is generally made available to such
  databases as NIST's National Vulnerability Database [NISTNVD].  It is
  possible that vendors may wish to release information early to some
  customers.  We do not discuss here whether that is a good idea, but
  if it is employed, then appropriate access controls and authorization
  SHOULD be applied to that information.

7.  IANA Considerations

7.1.  MUD Extension

  IANA has added "transparency" to the "MUD Extensions" registry
  [RFC8520] as follows:

  Value:  transparency
  Reference:  RFC 9472

7.2.  YANG Registration

  IANA has registered the following YANG module in the "YANG Module
  Names" registry [RFC6020]:

  Name:  ietf-mud-transparency
  Namespace:  urn:ietf:params:xml:ns:yang:ietf-mud-transparency
  Maintained by IANA:  N
  Prefix:  mudtx
  Reference:  RFC 9472

  The following URI has been registered in the "IETF XML Registry"
  [RFC3688]:

  URI:  urn:ietf:params:xml:ns:yang:ietf-mud-transparency
  Registrant Contact:  IESG
  XML:  None.  Namespace URIs do not represent an XML specification.

7.3.  Well-Known Prefix

  IANA has added the following URI suffix to the "Well-Known URIs"
  registry in accordance with [RFC8615]:

  URI Suffix:  sbom
  Change Controller:  IETF
  Reference:  RFC 9472
  Status:  permanent
  Related Information:  See ISO/IEC 5962:2021 and SPDX.org

8.  References

8.1.  Normative References

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

  [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
             DOI 10.17487/RFC3688, January 2004,
             <https://www.rfc-editor.org/info/rfc3688>.

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

  [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
             and A. Bierman, Ed., "Network Configuration Protocol
             (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
             <https://www.rfc-editor.org/info/rfc6241>.

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

  [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
             Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
             DOI 10.17487/RFC7231, June 2014,
             <https://www.rfc-editor.org/info/rfc7231>.

  [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
             Application Protocol (CoAP)", RFC 7252,
             DOI 10.17487/RFC7252, June 2014,
             <https://www.rfc-editor.org/info/rfc7252>.

  [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
             Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
             <https://www.rfc-editor.org/info/rfc8040>.

  [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
             May 2017, <https://www.rfc-editor.org/info/rfc8174>.

  [RFC8520]  Lear, E., Droms, R., and D. Romascanu, "Manufacturer Usage
             Description Specification", RFC 8520,
             DOI 10.17487/RFC8520, March 2019,
             <https://www.rfc-editor.org/info/rfc8520>.

  [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers
             (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
             <https://www.rfc-editor.org/info/rfc8615>.

  [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
             Ed., "HTTP Semantics", STD 97, RFC 9110,
             DOI 10.17487/RFC9110, June 2022,
             <https://www.rfc-editor.org/info/rfc9110>.

8.2.  Informative References

  [CSAF]     Rock, L., Ed., Hagen, S., Ed., and T. Schmidt, Ed.,
             "Common Security Advisory Framework Version 2.0", OASIS
             Standard, November 2022, <https://docs.oasis-
             open.org/csaf/csaf/v2.0/csaf-v2.0.html>.

  [CVRF]     Hagen, S., Ed., "CSAF Common Vulnerability Reporting
             Framework (CVRF) Version 1.2", Committee Specification 01,
             September 2017, <https://docs.oasis-open.org/csaf/csaf-
             cvrf/v1.2/csaf-cvrf-v1.2.pdf>.

  [CycloneDX15]
             CycloneDX, "CycloneDX v1.5 JSON Reference", Version 1.5.0,
             <https://cyclonedx.org/docs/1.5/json>.

  [EO2021]   Biden, J., "Executive Order on Improving the Nation's
             Cybersecurity", EO 14028, May 2021.

  [NISTNVD]  NIST, "National Vulnerability Database",
             <https://nvd.nist.gov>.

  [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
             BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
             <https://www.rfc-editor.org/info/rfc8340>.

  [SPDX]     The Linux Foundation, "The Software Package Data Exchange
             (SPDX) Specification", Version 2.3, 2022,
             <https://spdx.github.io/spdx-spec/v2.3/>.

Acknowledgments

  Thanks to Russ Housley, Dick Brooks, Tom Petch, and Nicolas Comstedt,
  who provided review comments.

Authors' Addresses

  Eliot Lear
  Cisco Systems
  Richtistrasse 7
  CH-8304 Wallisellen
  Switzerland
  Phone: +41 44 878 9200
  Email: [email protected]


  Scott Rose
  NIST
  100 Bureau Dr.
  Gaithersburg, MD 20899
  United States of America
  Phone: +1 301-975-8439
  Email: [email protected]

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