MUD-Based RATS Resources Discovery

Verifiers, Endorsers, and Attesters are roles defined in the RATS Architecture . In the RATS architecture, the Attester role relies on the Verifier and Endorser roles to enable the appraisal of Attestation Evidence produced by said Attesters; and to create corresponding Attestation Results. Attestation Results compose a believable chunk of information that can be digested by Relying Parities in order to assess an Attester’s trustworthiness. The assessment of a remote peer’s trustworthiness is vital to steer any future protocol interaction between the Attester and the remote Relying Party. To create these Attestation Results to be consumed by Relying Parties, the Attestation Evidence an Attester creates has to be processed by one or more appropriate Verifiers. This document defines a procedure that enables the discovery of viable resources for RATS services in a local scope: 1.) Reference Integrity Measurements, and 2.) Endorsement documents. Additionally, a third option is provided: this document defines the option to enable the discovery of remote Verfiers: 3.) Remote Attestation Services (RAS) in a global scope (if no local trusted authorities are available). Attestation Policies and Endorsements are required to enable an appropriate appraisal of Attestation Evidence in a fashion that helps Relying Parties to digest the corresponding Attestation Results. This document defines the use of MUD URIs embedded in Secure Device Identifiers (IEEE 802.1AR DevIDs) as defined by . These DevIDs are enrolled on the Attester by manufacturers or related supply chain entities with appropriate authority. The DevIDs can be presented to local Network Management Systems, AAA-services (e.g. via IEEE 802.1X), or other points of first contact (e.g. ) in a local scope. These local entities of authority can digest the DevID and conduct trust decisions based on the DevID by tracing associated certification paths and trust anchors . If the DevID presented by the Attester is deemed to be trusted by the local trust authority, the MUD URI embedded is considered to be a trusted source of viable (and if their Identity Documents are also to be trusted - believable) Attestation Policies, Endorsements, and even globally available RAS. In essence, the MUD file that is referenced by the DevID presented refers to sources of Attestation Policies and Endorsements recommended by the manufacturer or related supply chain entities with appropriate authority. These sources are required by appraisal procedures conducted by Verifiers in order to create well-founded Attestation Results. For example, trusted Endorses can enrich Attestation Results by vouching for the quality of hardware components, the composition of a Composite Attester, or other security characteristics of an Attester. This specification does not define the format of Attestation Policies and Endorsement documents. A type of Attestation Policies and their representation is defined in [I-D.birkholz-rats-coswid-rim]. A specific format of Endorsements for hardware components based on is defined in [I-D.birkholz-rats-endorsement-eat].

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 when, and only when, they appear in all capitals, as shown here.

The MUD URI embedded in a DevID presented by an Attester points to a MUD file. defines the format of how to embed MUD URIs in Secure Device Identifiers. This document uses this specification and does neither modify nor augment the definition about how to compose a MUD URI.

As the resources required by a Verifier’s appraisal procedures have to be trustworthy, a MUD signature file for a corresponding MUD File MUST be available. The MUD File MUST also include a reference to its MUD signature file via the ‘mud-signature’ statement. A MUD signature MAY be referenced in the DevID, but entities consuming this information must be aware that a MUD File can change. If MUD file changed (the MUD signature in the DevID does not match any more), a MUD signature file referenced in the MUD File itself MUST exist and MUST be available. If both the signature embedded in a DevID and referenced by a MUD File do not match, the MUD File SHOULD NOT be trusted.

The level of assurance about the integrity of a MUD URI embedded in a DevID is based on the level of trust put into the corresponding trust anchor associated with the DevID. If you cannot establish a level of trust towards the entity that signed a DevID (the signer), the embedded MUD URI SHOULD NOT be trusted. The level of assurance about the integrity of a MUD file is based on the level of trust put into the entity that created the corresponding MUD File Signature. If you cannot establish a level of trust put into the corresponding trust anchor associated with the MUD signature file, the referenced MUD File SHOULD NOT be trusted.

Reference Integrity Measurements and Endorsement documents that are referenced by a MUD File MUST be signed. The signing procedures, the format of corresponding Identity documents, and the establishment of trust relationships associated with these resources are out-of-scope of this document.

The MUD URI embedded in a DevID presented by an Attester points to a MUD File. At the time of writing this -00 I-D, MUD URIs always point to a piece of data that is a YANG-modeled XML file with a structure specified in the style of a YANG module definition ( and corresponding updates: , ). This document specifies a YANG module augment definition for generic MUD files to create RATS MUD files. The following definition MUST be used, if a MUD URI points to a RATS MUD file.

The following tree diagram provides an overview of the data model for the “ietf-mud-rats” module augment.

module: ietf-mud-rats augment /mud:mud: +--rw ras | +--rw ras-uris* inet:uri +--rw rim | +--rw rim-uris* inet:uri +--rw edt +--rw edt-uris* inet:uri

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This YANG module has normative references to  and augments .

 file ietf-mud-rats@2019-03-09.yang
module ietf-mud-rats {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-mud-rats";
  prefix "mud-rats";

  import ietf-mud {
    prefix "mud";
  }

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

  organization
    "IETF RATS (Remote ATtestation procedureS) Working Group";

  contact
    "WG Web: http://tools.ietf.org/wg/rats/
     WG List: rats@ietf.org
     Author: Eliot Lear 
     Author: Henk Birkholz ";

  description
    "This YANG module augments the ietf-mud model to provide for three
     optional lists to enable Remote Attestation Procedures so that
     this device type may be used as a controller for other
     MUD-enabled devices.

     Copyright (c) 2020 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 Simplified 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 XXXX
     (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
      for full legal notices.

     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.";

  revision 2020-03-09 {
    description
      "Initial proposed standard.";
       reference "RFC XXXX: MUD Extension to find RATS supply chain
       entity resources: remote attestation services, endorsement
       documents, and reference integrity measurement";
  }

  grouping mud-rats-grouping {
    description
      "Grouping to locate RATS services";
    container ras {
      description
        "Lists of Remote Attestation Service
         (RAS/Verifiers) candidates.";
      leaf-list ras-uris {
        type inet:uri;
        description
          "A list of Verifiers that can appraise evidence produced by
           the entity that presents a DevID including this MUD URI.";
      }
    }
    container rim {
      description
        "Lists of Reference Integrity Measurement (RIM) candidates.";
      leaf-list rim-uris {
        type inet:uri;
        description
          "A list of RIM CoSWID that provide reference integrity
           measurements represented as signed CoSWID using
           the CoSWID RIM extension.";
      }
    }
    container edt {
      description
        "List of Endorsements for Roots of Trusts (e.g. Endorsement
         Key Certificates).";
      leaf-list edt-uris {
        type inet:uri;
        description
          "A list of Endorsements that vouch for the characteristics
           of Roots of Trusts the entity possesses.";
      }
    }
  }
  augment "/mud:mud" {
    uses mud-rats-grouping;
    description
      "add mud-rats URI resources";
  }
}

]]>




Potentially




Most likely a summary of the trust relationship corresponding to the RATS architecture